Term
| Where is aqueous humor produced? |
|
Definition
| nonpigmented epithelium of the ciliary body |
|
|
Term
| What are the two mechanisms through which the nonpigmented ciliary body epithelium produce the aqueous humor? |
|
Definition
Passive: Diffusion along concentration gradient and ultrafiltration (via vascular hydrostatic pressure))
Active: most significant component of aqueous humor production, fluid is secreted against the concentration gradient via a reaction catalyzed by carbonic anhydrase |
|
|
Term
| Describe the conventional outflow pathway of aqueous humor as it circulates through the eye. |
|
Definition
| secreted into the posterior chamber (via non-pigmented ciliary epithelium), travels through the pupil into the anterior chamber, exits the eye through the iridocorneal angle into the vortex veins and systemic circulation |
|
|
Term
| Not all of the aqueous humor exits the eye via the iridocorneal angle, describe the unconventional outflow pathway for aqueous humor, and the degree to which it is responsible for drainage in dogs, cats, and horses. |
|
Definition
aka uveoscleral outflow, aqueous humor escapes the globe through the iris root into the supraciliary and suprachoroidal space
dog: 15%
cat: 3%
horse: 50% |
|
|
Term
| What is the normal intraocular pressure in domestic species? |
|
Definition
| 10-25 mmhg, intraocular pressure should not vary more than 20% between eyes |
|
|
Term
| What two environmental factors can influence intraoccular pressure? |
|
Definition
Diurnal/time of day (ie. k9 have highest pressures in the morning)
Seasonal (ie. pressure is usually higher in the winter months) |
|
|
Term
| What is the definition of glaucoma and what is the pathological sequelae of this condition? |
|
Definition
| Intraocular pressures greater than 30mmhg, always due to decreased outflow of aqueous humor --> results in pressure necrosis of retinal ganglion cells and axons --> loss of peripheral visual field --> progressive to blindness |
|
|
Term
| T/F: the development of glaucoma is ALWAYS secondary to decreased outflow of aqueous humor |
|
Definition
|
|
Term
| What three clinical signs are commonly seen in association with acute presentations of glaucoma? |
|
Definition
episcleral venous congestion (indicative of deep intraoccular disease)
corneal edema (blue)
Mydriasis (best appreciated via retroillumination) |
|
|
Term
| What are some clinical signs associated with chronic glaucoma? |
|
Definition
bupthalmos (Can be differentiated from exophthalmos by enlarged corneal diameter in affected eye), haab's stria (linear fractures in descement's membrane secondary to buphthalmos), lens (sub)luxation (stretch and breakage of zonular ligaments), deep corneal vascularization, optic disc cupping, tapetal hyperreflectivity, and retinal vascular attenuation
**insiduous onset, unilateral or bilateral |
|
|
Term
| What is the most important tool used to diagnose glaucoma? |
|
Definition
tonometry
***digital palpation of the globe is UNACCEPTABLE |
|
|
Term
| What is gonioscopy and what condition is it used to diagnose? |
|
Definition
| method of directly examining the iridocorneal angle with a special lens, used to diagnose and differentiate between primary and secondary glaucoma |
|
|
Term
| What are some technical considerations to be considered when using Schiotz tonometer? |
|
Definition
| topical anesthesia is required, not recommended for weak corneas (measures the force necessary to indent the cornea), not as accurate as applanation tonometry, cannot be used in large animal patients (requires the eye to be positioned vertically) |
|
|
Term
| What are some technical considerations to be considered when using applanation tonometry? |
|
Definition
| topical anesthesia isn't always required, can be used on diseased corneas (smaller area of the cornea assessed than schiotz), can be used in any postion, sometimes provided falsely elevated readings |
|
|
Term
| What are some technical considerations to be considered when using rebound tonometry? |
|
Definition
| no topical anesthesia required, can be used on diseased corneas, most accurate of all methods |
|
|
Term
| What three physical restraint methods can result in falsely elevated tonometry readings? |
|
Definition
jugular pressure (Restraint/tight collars)
excessive pressure on eyelids
consistent body position (ex.
intraocular pressure is elevated with dorsal recbumency) |
|
|
Term
| T/F: secondary glaucoma is usually bilateral, more common in female animals, and usually the result of primary-angle closure |
|
Definition
FALSE
all of the above describe primary glaucoma, which is a inherited disease that results in congenital abnormalities in the iridocorneal angle (goniodysgenesis, pectinate ligament dysplasia) in the absence of concurrent ocular or systemic disease |
|
|
Term
| What is the difference between primary open angle glaucoma (POAG) and primary angle-closure glaucoma (PACG)? Which is more common in dogs? |
|
Definition
PACG is characterized by sudden unilateral IOP elevation in middle aged animals with the fellow eye becoming affected in average within the next 8 months. PACG is the most common form of primary glaucoma in dogs.
POAG glaucoma is a insidious bilateral elevation in IOP that presents in younger animals and is the result of biochemical alterations within the trabecular meshwork of the iridocorneal angle with increased resistance to aqueous humor outflow |
|
|
Term
| What is the most common presentation of primary glaucoma in dogs? |
|
Definition
unilateral, red (episcleral injection and deep cornea neovascularization), cloudy (corneal edema) eye with dilated non-responsive pupil in a dog (differentiated from uveitis <-- characterized by miosis)
(ie. primary angle closure glaucoma) |
|
|
Term
| What form of glaucoma is most common in cats and horses? |
|
Definition
| secondary glaucoma (occurs with concurrent ocular or systemic disease) |
|
|
Term
| What disease is most commonly associated with the development of secondary glaucoma? |
|
Definition
|
|
Term
| What are three ways that uveitis can contribute to the development of secondary glaucoma? |
|
Definition
Physical obstruction: inflammatory debris (blood clots, fibrin, inflammatory cells) physically obstructs the iridocorneal angle and/or the pupil --> obstruction to aqueous humor outflow
Peripheral anterior synechia: adhesions between the iris and the cornea obstruct the iridocorneal angle
Formation of preiridial fibrovascular membrane (PIFM): obstructs the iridocorneal angle +/- the iris |
|
|
Term
| What is iris bombe and what is it's pathological sequela? |
|
Definition
| 360 degree posterior synechia (adhesion between iris and lens) resulting in obstruction to aqueous humor outflow at the iridocorneal angle and the pupil with a build up of aqueous in the posterior chamber --> this give the iris a pillowy appearance and results in the development of secondary glaucoma |
|
|
Term
| How can neoplasia cause secondary glaucoma? |
|
Definition
| obstruction of the iridocorneal angle with neoplastic cells, or obliteration of the iridocorneal angle's structural integrity |
|
|
Term
| How can diabetes predispose a patient to the development of secondary glaucoma? |
|
Definition
| diabetic intumsecent cataracts due to accumulation of osmotically active sorbital within the lens capsule results in a swollen lens and a forward displacement of the iris up against the cornea --> narrowing +/- closure of the iridocorneal angle -> secondary glaucoma |
|
|
Term
| Aqueous Humor Misdirection Syndrome (AHMS) occurs spontaneously in what breed? What is the pathology of AHMS? |
|
Definition
AHMS occurs spontaneously in cats
Instead of flowing forward through the pupil the aqueous humor flows posteriorly into the vitreous cavity --> build of of aqueous humor in the vitrous chamber pushed the lens, iris, and ciliary body anteriorly --> narrowed and eventually closure of the iridocorneal angle + pupilary obstruction --> SECONDARY GLAUCOMA |
|
|
Term
| What finding appreciable with slit lamp ocular exam is consistent with AHMS in cats? |
|
Definition
| uniformly shallow anterior chamber (all purkinje images are close together) |
|
|
Term
| What are the three goals of medical management of glaucoma? |
|
Definition
reduce AND maintain intraocular pressure to a healthy level
preservation of vision
maintain comfort/quality of life |
|
|
Term
| What are the two main mechanisms through which medical management of glaucoma operates? |
|
Definition
Reduce aqueous humor production
Increase aqueous humor outflow |
|
|
Term
| How does mannitol aid in the treatment of glaucoma? What situations is it's use approprtiate? |
|
Definition
Mannitol is used for emergency treatment of acute glaucoma (primary- K9) to quickly reduce IOP by decreasing osmostic gradient responsible for passive production of aqueous humor amd by shrinking the vitreous humor
**mannitol is contraindicated in patients with renal failure and/or dehydration, as well as cardiovascular disease (rapid expansion of extracellular volume --> CHF) |
|
|
Term
| How are beta blockers used to treat glaucoma and what are the indications for their use? |
|
Definition
non-specific beta-blockers (timolol) decrease production of aqueous humor secondary to reducing the concentration of CAMP within the ciliary body
Beta blockers only reduce IOP a little on their own so can be used in combination with other drugs for maintenance of glaucomatous eyes and for PROPHYLACTIC treatment of unaffected eye in dogs with primary angle closure glaucoma
***caution for systemic beta blockade in small dogs and cats --> cardiovascular disease/syncope and bronchial asthma |
|
|
Term
| What carbonic anhydrase inhibitor is ineffective in cats? |
|
Definition
brinzolamide
**use dorzolamide topically, or methazolamide/acetozolamide systemically |
|
|
Term
| What are the indications and potential side effects of carbonic anhydrase inhibitors when used to treat glaucoma? |
|
Definition
topicals preffered over systemics due to equal efficacy with reduced side effects (which include diuresis, GI upset, metabolic acidosis, hypokalemia, bone marrow toxicity --> blood dyscrasias)
**cats are more susceptible to adverse effects (use dorzolamide topically in cats) |
|
|
Term
| What is the most effective treatment used in medical management of glaucoma, in what species and diseases is the use of this drug contraindicated? |
|
Definition
prostaglandin analoges (travaprost) rapidly reduce IOP by increasing uveoscleral outflow (ie. unconventional outflow pathway) but are ineffective and cats and may disrupt the blood-aqueous-barrier in horses.
To be used in dogs for emergency management of acute glaucoma as well as maintenance therapy.
**cause extreme miosis, contraindicated in cases of uveitis and/or lens luxation due to the potential for pupilary block to develop and inhibit conventional aqueous outflow |
|
|
Term
| When is surgical management of glaucoma indicated? |
|
Definition
When medical management is no longer effective (prostaglandin anagloges, beta blockers, carbonic anhydrase inhibitors, mannitol) AND the eye is still visual
**DOES NOT elliminate the need for medical management, repeat surgery may be necessary |
|
|
Term
| What two procedures can be used to surgically manage glaucoma? |
|
Definition
Laser Cyclophotocoagulatoion (destruction of the ciliary body processes --> decreased aqueous humor production), can be done transscleral or endoscopic
Goniovalve (silicone tube placed within the anterior chamber provides an additional outlet for aqueous humor outflow) |
|
|
Term
| What are some adverse effects associated with laser cyclophotocoagulation for treatment of glaucoma? |
|
Definition
| post-op spike in IOP due to swelling of uveal tissues compressing the iridocorneal angle, cataracts if laser hits the lens, staphyloma (thin spot in sclera where the laser was directed transcleral, like an anneurysm, increased risk of rupture at this point) |
|
|
Term
| What are some adverse effects associated with goniovalve surgical management of glaucoma? |
|
Definition
| the implant can migrate, and can become obstructed (often secondary to uveitis) |
|
|
Term
| What are three salvage procedures for the treatment of glaucoma, what are the indications for these procedures? |
|
Definition
to be performed in irreversibly blind and painful eyes
Enucleation (remove eye and sew lids together)
Evisceration with intrascleral prosthesis (remove contents of the eye from the fibrous tunic (cornea and sclera) and replace with silicon ball, KCS and dehisence are major complications)
Intravitreous gentamicin injection (if can't afford surgery, or poor candidate for anesthesia) |
|
|
Term
| What drugs are indicated for emergency treatment of glaucoma in a visual eye? |
|
Definition
| prostaglandin analogues (latanoprost) and osmotic diuretics (mannitol) |
|
|
Term
| What drugs are indicated for maintenance of healthy IOP in patients with glaucoma following resolution of acute presentation, or if chronic? |
|
Definition
carbonic anhydrase inhibitor
beta blockers (timolol)
and prostaglandin analogue |
|
|
Term
| What are the components of the posterior segment of the eye? |
|
Definition
| vitreous, choroid (+ tapetum), retina, optic nerve |
|
|
Term
| What is the function of the embryonic hyaloid artery? |
|
Definition
originates from the optic nerve and ramifies to surround and nourish the developing lens
**should be fully regressed by 2-3 weeks of age in the dog |
|
|
Term
| What two terms are synonymous with persistent hyaloid artery? |
|
Definition
Bergmeister's papilla (remnant at optic nerve head)
Mittendorf's dot (remnant at posterior lens capsule) |
|
|
Term
| What accounts for 75% of the volume of the globe of the eye? |
|
Definition
|
|
Term
| What is the composition of the vitreous humor? |
|
Definition
99% water + collagen (produced by hyalocytes <-- vitreous stromal cells) and hyaluronic acid fibrils
**no vessles, nerves or lymphatics |
|
|
Term
| What are the two main functions of the vitreous humor? |
|
Definition
metabolic support for the lens and retina
mechanical support for the retina (gently pushes the neurosensory retina against the retinal pigmented epithelium) |
|
|
Term
| When is a fine needle aspirate of the virteous indicated for diagnostic cytology? |
|
Definition
Only do FNA in blind eyes due to high risk of severe complications (intraocular bleeding, retinal detachement, cataract)
**can also to ocular ultrasound and direct/indirect opthalmoscopy to asses vitreous |
|
|
Term
| What three diseases are associated with vitreous developmental abnormalities? |
|
Definition
Cloquet's Canal (clear tube from the optic nerve head, through the vitreous, to the lens capsule <-- following regression of the hyalin artery)
Mittendorf's dot (white spot on anterior lens capsule, posterior cataract where remnant hyalin artery contacts the back of the lens)
Bergmeister's papilla (small tuft of tissue at optic nerve head, remnant of hyaloid artery) |
|
|
Term
| T/F: ALL developmental vitreous diseases are usually associated with clinically significant visual deficits |
|
Definition
FALSE
Cloquet's canal, mittendorf's dot, bergmeister's papilla and persistent posterior tunica vasculos lentis do not affect vision
**perisistent patent hyaloid artery can lead to vitreous hemorrhage (clotting and contraction of the vitreous can predispose to retinal detachement) |
|
|
Term
| What are two aging changes that occur within the posterior segment of the eye? |
|
Definition
| Vitreal degeneration and asteroid hyalosis (condensed particles of calium phospholipids suspended within the vitreou <-- usually incidental, NO tx) |
|
|
Term
| What three things can result in vitreal degeneration? |
|
Definition
Sequel to uveitis
Sequel to metabolic changes:
aging (+asteroid hyalosis)
retinal disease
systemic disease |
|
|
Term
| What is vitreal syneresis? |
|
Definition
| liquefication of the vitreous --> may prolapse through the pupil into the anterior chamber --> loss of supportive pressure against the retina can predispose to retinal detachment |
|
|
Term
| What are some causes of vitreous hemorrhage? |
|
Definition
trauma, spontaneous/idiopathic, underlying systemic disease (ex. coagulopathy, hypertension, vasculitis)
**slowly reabsorbed (b/c vitreous is avascular) and clotting with contraction can predispose to retinal detachment |
|
|
Term
| Between which two layers of the retinal do detachments occur? |
|
Definition
| retinal detachments occur between the neurosensory retina, and the retinal pigmented epithelium |
|
|
Term
| What vessels nourish the outer retina? Inner? |
|
Definition
Outer retina is nourished by the choroidal vessels
Inner retina is nourished by the retinal vessels (w/in nerve fiber layer)
**only mammals have retinal blood vessels |
|
|
Term
| Where do optic nerve fiber decussate? |
|
Definition
|
|
Term
| What region of the brain interperates sensory info from the retina? |
|
Definition
|
|
Term
| What characteristics are associated with Rod sensory information? |
|
Definition
| most active in dim light (highly sensitive to light), but provide minimal detail |
|
|
Term
| What characteristics are associated with cone sensory information? |
|
Definition
| more active in bright light (less light sensitive than rods), responsible for detailed color vision |
|
|
Term
| T/F: Retinal pigmented epithelium is not pigmented across the entirety of the fundus |
|
Definition
TRUE
**retinal pigmented epithelium is unpigmented in the region overlying the tapetum (triangular area in the superior region of the fundus) |
|
|
Term
| What is the anatomic term for the point of exit of optic nerve fibers through the globe? |
|
Definition
| lamina cribosa (like a sieve through the sclera) |
|
|
Term
| What are stars of winslow? |
|
Definition
end on view of choroicapillaris vessels (provide metabolic support to outer retina)
**esp. prominent in equine fundus |
|
|
Term
| What is the function of the tapetum lucidum? |
|
Definition
reflects light back to the photoreceptors (rods and cones) to enhance light sensitivity <-- especially useful in really dim light
**carnivores have a cellular tapetum, herbivores have a fibrous tapetum |
|
|
Term
| Which neuro exam tests are used to assess vision? |
|
Definition
Menace response (afferent: optic nerve, efferent: CN 7, facial)
Behavioral (history from owner, maze testing etc.) |
|
|
Term
| Which neuro exam tests are used to assess light perception? |
|
Definition
Pupillary light reflex (afferent:optic nerve, efferent: CN 3, occulomotor)
Dazzle reflex
electroretinography
***DOES NOT ASSESS VISION, reflexes may be intact even if only a few photoreceptors are functioning (not enough for vision), OR retina could be fully functional but lesions in the optic nerve/cerebral cortex could result in blindness) |
|
|
Term
| When is electroretinography indicated? |
|
Definition
| prior to cataract surgery and in cases of blindness with an otherwise normal ophthalmic exam |
|
|
Term
| Which type of fundoscopy (direct or indirect) is most useful for screening for posterior segment disease? |
|
Definition
| Indirect --> provides a larger field of view than direct; however image is inverted and reversed so it requires some adjustment/practice |
|
|
Term
| What type of lesion localication is key to understanding fundic pathology? |
|
Definition
object overlay
(neurosensory retina overlaying the retinal pigment eipthelium overlaying the tapedum overlaying the large vessel layer of the choroid overlaying the sclera) |
|
|
Term
| What anatomic structure comprises the outermost layer of the fundus? What is the gross appearance of this structure? |
|
Definition
| The sclera is the outermost layer of the fundus, it appears WHITE |
|
|
Term
| Which layer is directly overlying the sclera on the fundus? What is the gross appearance of this structure? |
|
Definition
the choroid/middle vascular/uveal tunic
Grossly this layer consists of red-orange vessels radially oriented from the optic nerve head +/- dark pigment dispersed between the vessels |
|
|
Term
| T/F: the tapetum obscures all of the fundic layers (choroid and sclera) behind it |
|
Definition
TRUE
**triangular region located in the superior fundus |
|
|
Term
| What color iris is associated with non-pigmented retinal pigment epithelium across the entirety of the fundus? Describe the appearance of the fundus in these patients? |
|
Definition
Blue irises are often associated with non-pigmented retinal pigmented epithelium.
The fundus in these patients has a superior colorful reflective zone which is the tapetum, overlying the orange-red vessels of the choroid, which may have dark pigment between them, or the white sclera may be visible between these choroidal vessels if there is no pigment |
|
|
Term
| T/F: the neurosensory retina is transparent with overlying retinal vessels that branch out radially from the optic nerve head |
|
Definition
TRUE
**that's why accumulation of inflammatory cells results in regions of tapetal hyporeflectivity where the transparent neurosensory retina becomes thicker and more opaque |
|
|
Term
| What color tapetum is more commonly seen in puppies and young dogs? What color is more common in mature dogs? |
|
Definition
| purple in young --> yellow/orange in mature |
|
|
Term
| What color is the tapetum in most cats? |
|
Definition
|
|
Term
| What phenotypes are more likely to lack a tapetum? |
|
Definition
|
|
Term
| What are the morphological differences between retinal vessels and choroidal vessels? |
|
Definition
choroidal vessels are larger caliber, straighter and orange-red
retinal vessels are smaller caliber, dendritic branching, dark red, and arise from (often tend to overly) the optic nerve head |
|
|
Term
| What components of the fundic appearance of the optic nerve head are affected by the degree of retinal ganglion axonal myelination? |
|
Definition
color (more whiteish = more myelin, darker grey = less myelin)
shape (in dogs with highly variable retinal ganglion axonal myelination the optic nerve head can appear round, oval, triangular or polygonal) <-- usually round and darker in the cat because axons are not myelinated until they exit the globe |
|
|
Term
| What is the difference between the position of the optic nerve head in the canine fundus vs. feline fundus? |
|
Definition
In dogs the optic nerve head is normally positioned at the junction of the tapetum and non-tapetal fundus.
In cats the optic nerve head is normally located within the tapetum (ie. more superiorly located in cats than in dogs) |
|
|
Term
| Tapetal hyporeflectivity is associated with what fundic pathology? |
|
Definition
| retinal thickening due to infiltration of cells or fluid |
|
|
Term
| Tapetal hyperreflectivity is associated with what fundic pathology? |
|
Definition
| Retinal thinning/degeneration |
|
|
Term
| What is the characteristic appearance of active fundic lesions (ie. chorioretinitis, neoplastic infiltrates, edema, hemorrhage)? |
|
Definition
indistinct margins
raised (assess looking at the course of overlying blood vessels)
hyporeflective tapetal lesions
greyish-white regions on the nontapedal fundus (accumulation of inflammatory cells/debris obscuring the pigmented retinal pigmented epithelium and the choroid) |
|
|
Term
| What is the characteristic appearance of inactive fundic lesions? |
|
Definition
| depigmentation or variable pigment clumping (ie. mottled appearance), +/- vascular attenuation (less branching, smaller caliber vessels) and optic nerve atrophy/pallor |
|
|
Term
| What four conditions can cause increased calliber and tortuousity of retinal vessels? |
|
Definition
SYSTEMIC HYPERTENSION
and hyperviscosity syndromes, inflammatory conditions, orbital disease |
|
|
Term
| T/F: the appearance of retinal hemorrhage indicates the location and underlying cause of the hemorrhage |
|
Definition
FALSE
**appearance can be used to determine location but NOT cause of hemorrhage
subretinal: large and dark
intraretinal: dot-blot
superficial: flame shaped
pre-retinal: globular/boat-keel shaped |
|
|
Term
| What three potential causes of retinal detachment? |
|
Definition
vitreal hemorrhage (blood clots and contracts --> loss of vitreous pressure against the retina)
vitreal degeneration
inflammation with vascular exudation of fluid and/or cells |
|
|
Term
| What physical exam findings are pathognomonic for retinal detachement? |
|
Definition
| vascular membrane visible within the pupil on direct examination (pupil of usually dilated because loss of sensory information from the detached retina is interpreted as a lack of light) |
|
|
Term
| What are the two types of inherited canine retinal dystrophies (aka. progressive retinal atrophy/ PRA) and what is the difference in their clinical presentations? |
|
Definition
photoreceptor dysplasia <-- early onset
photoreceptor degeneration <-- later onset
*** both have bilateral uniform tapetal hyperreflectivity (consistent with retinal degeneration/thinning) and present initially as night blindness (nyctalopia) because rods are the first and most severely affected photoreceptors--> progressive to total blindness (cones and rods affected)
eventually retinal vascular attenuation, decreased myelination of optic nerve head (smaller and more darkly colored) and pupil size may be enlarged with decreased but present PLR (requires very few numbers of functional photoreceptors)
NO TX |
|
|
Term
Which breed of dog is more likely to experience hemeralopia (day blindness) secondary to inherited retinal dystrophy?
**as opposed to all other breeds, where nyctalopia (night blindness) is more common |
|
Definition
| Malamutes (cone degeneration occurs before rod degeneration) |
|
|
Term
| What canine retinal dystrophy is associated with vitamin E deficiency? |
|
Definition
Retinal pigmented epithelial dystrophy <-- multifocal accumulation of lipofuscin pigment surrounded by areas of tapetal hyperreflectivity, central visual field is compromised first --> may or may not progress to complete blindness
**more common in Europe, no TX, however vit E supplementation may slow or prevent progression in animals with defficiencies |
|
|
Term
| What are two histological appearances associated with congenital retinal dysplasia? |
|
Definition
retinal folding (neurosensory retina affected)
geographic retinal dysplasia (variable thickening and thinning of the retina --> predisposed to retinal detachment esp. if extensive) |
|
|
Term
| T/F: retinal dysplasia is an inherited disease so animals with this phenotype should NOT be bred |
|
Definition
TRUE
**caveat: retinal dysplasia can occur from intrauterine or neonatal infectious disease (feline panleukopenia, canine herpes/parvo, Bovine viral diarhea), also trauma, toxin, and vit A deficiency but these causes are rare compared to genetic |
|
|
Term
| What is the impact of retinal dysplasia of vision? |
|
Definition
It depends,
mildly affected animals: small regions of dark (opaque white on non-tapetal fundus) dots/linear/vermiform lesions surrounded by hyperreflective tapetum, often these animals have clinically normal vision
geographic dysplasia is a more severe form of retinal folding in which individuals are predisposed to retinal detachment and blindness |
|
|
Term
This lesion is suggestive of what disease:
bilateral, present since birth, choroidal hypoplasia often located temporal to the optic nerve head, abnormally tortuous choroidal vessels, optic nerve coloboma, in a herding dog |
|
Definition
Collie eye anomaly
if just choroidal hypoplasia often clinically normal vision, optic nerve coloboma is associated with blindness, retinal detachment with intraocular hemorrhage |
|
|
Term
| What signalment and clinical signs are associated with sudden acquired retinal degeneration syndrome? |
|
Definition
middle aged female dog with sudden onset of bilateral blindness +/- clinical signs associated with hyperadrenocorticism (Pu/Pd, weight gain and polyphagia)
**due to acute and complete photoreceptor death, etiology unknown, no tx, blindness is permanent |
|
|
Term
| What diagnostic finiding is consistent with sudden acquired retinal degeneration syndrome (SARDS)? |
|
Definition
completely extinguished electroretinogram
**confirms loss of photoreceptor function |
|
|
Term
| What is the most common form of inflammation in the posterior segment of the eye? |
|
Definition
chorioretinitis (primarily a choroidal inflammation that affects the retina due to the close anatomic proximity of these two structures) may have no external signs or may be associated with panuveitis (all tunics of the eye affects) <-- redness, corneal edema, aqueous flare, miosis
W |
|
|
Term
| What is the difference in appearance of active inflammatory fundic lesions, compaired to inactive (ie. chorioretinal scars)? |
|
Definition
Active lesions are characterized by regions of tapetal HYPOreflectivity and grey colored areas with indistinct boarders +/- raised <-- retinal or subretinal accumulation of inflammatory debris
Inactive lesions/scars are characterized by distinct regions of teptal HYPERreflectivity +/- pigment clumping and optic nerve atrophy (pallor) <-- retinal degeneration/thinning |
|
|
Term
| What are some general infectious causes of chorioretinitis? |
|
Definition
viral (K9 distemper/herpes, FIV/FIP, BVDV)
bacterial (associated with septicemia <- lepto, brucella, borellia)
Rickettsial (ehrlichia and anaplasma)
fungal (blasto, crypto, aspergillus)
parasitic (toxoplasma, neospora, leishmania) |
|
|
Term
| What are three immune mediated diseases associated with chorioretinitis? |
|
Definition
uveodermatologic syndrome
immune mediated vasculitis
immune mediated thrombocytopenia with retinal hemorrhage |
|
|
Term
| What are three metabolic syndromes associated with chorioretinitis? |
|
Definition
systemic hypertension (esp. in cats --> retinal and vitreal hemmorhage, retinal detachment and edema)
hyperviscosity syndrome
hypoprotinemia (-->retinal detachment) |
|
|
Term
| What are the two main treatment considerations for chorioretinitis? |
|
Definition
identify and treat the underlying primary cause (infectious, immune mediated, metabolic, neoplastic, idiopathic)
Treat the INFLAMMATION (systemic anti-inflammatories, NSAIDs/steroids/immunosupressants <-- depending on etiology) |
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Term
| What is the most important factor to consider when determining visual prognosis in a case of chorioretinitis? |
|
Definition
| degree of chorioretinal scarring (flat, sharply marginated regions of tapetal hyperreflectivity +/- pigment clumping/optic nerve pallor) AND response to treatment |
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Term
| What fundic appearance is consistent with optic nerve hypoplasia/aplasia? What is the etiology and tx for this condition? |
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Definition
| very small/darkly colored optic nerve head, this congenital defect is hertiable but can also spontaneously occur, uni or bilaterally, no TX |
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Term
| non-inflammatory optic disc swelling associated with increased intracranial pressure is called _______. |
|
Definition
papilledema
**not associated with visual deficits, identify and tx underlying disease |
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Term
| What clinical presentation is often associated with optic neuritis? |
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Definition
acute onset of blindness with fixed dilated pupils
**if only the retrobulbar section of the optic nerve is affected fundic exam will be normal, if intraoccular inflammation optic disk is usually swollen and hyperemic with indistinct margins |
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Term
| Many of the differentials for optic neuritis are the same as those for chorioretinitis; however, what immune mediated disease is commonly implicated in cases of optic neuritis? |
|
Definition
| Granulometous meningoencephalits (GME) |
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Term
| Optic nerve head cupping occurs secondarily to what chronic ocular disease process? |
|
Definition
glaucoma
**optic disk appears dark, round, and depressed, poor prognosis for vision |
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Term
| What other congenital anomaly is often associated with chorioretinal and optic nerve colobomas in cats? |
|
Definition
eyelid agenesis
** chorioretinal and optic nerve colobomas are more rare in cats than dogs |
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Term
| What infectious disease is associated with retinal dysplasia in cats? What other neurologic abnormalities are present in affected individuals? |
|
Definition
feline panleukopenia virus
affected kittens often have cerebral and cerebellar dysplasias as well |
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Term
| What essential amino acid is necessary for normal photoreceptor function? |
|
Definition
taurine
**deficiency --> feline central retinal degeneration (FCRD) |
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Term
| In patients with feline central retinal degeneration what other organ system should be assessed? How effective is treatment? |
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Definition
cardiovascular system should be assessed as taurine deficiency can cause DCM in cats
Taurine supplementation will prevent progression of the disease but nothing can be done to reverse retinal damage that has already occurred |
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Term
| What drug can cause dose-dependent retinal degeneration in cats? |
|
Definition
enrofloxacin (aka. baytril) and other flouroquinolones
**esp at high IV doses, patients present with mydriasis and/or acute blindness +/- patchy copper discoloration of tapetum |
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Term
| What type of wound closure is indicated for eyelid lacerations? |
|
Definition
primary closure in two layers
-deep intradermal near inner conjunctival surface but careful not to go full thickness --> predisposes to corneal ulceration
-figure eight at eyelid margin, and then superficial skin sutures along haired surface
careful to preserve eyelid margins, can use saline and dilute betadine to clean (NO SCRUB near cornea)
**tissue is so well vascularized that infection is uncommon even in contaminated wounds, important to preserve tissue to MINIMAL TO NO debridement |
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Term
| What is the definition of proptosis? |
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Definition
| equator of the globe lie anterior to palpebral fissure <-- often pressure of the eyelids on the proptosed globe further contributes to venous congestion and swelling |
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Term
| What species are more susceptible to proptosis and why? |
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Definition
carnivores have an incomplete bony orbit and are therefor more susceptible to proptosis than herbavores.
**also brachycephalic dog breeds are especially prone due to their shallow orbits |
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Term
| What are negative prognostic indicators associated with proptosis? |
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Definition
optic nerve transection
rupture of 3 or more extraocular muscles (compromised vascular integrity to the globe)
corneaoscleral laceration
+/- hyphema |
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Term
| What are some positive prognostic indicators associated with proptosis? |
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Definition
Positive consensual PLR (indicates intact retina and optic nerve)
voluntary movement of proptosed globe (integrity of extraocular muscles and therefore vasculature) |
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Term
| What surgical procedure can be done to aid in repairing a proptosis in cats or dolicocephalic dogs? |
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Definition
| lateral canthotomy (extend the palpebral fissure at the lateral canthus of the eye) |
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Term
| What is temporary tarsorrhaphy used to treat? Describe the surgical procedure. |
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Definition
Temporary tarsorrhaphy is used to replace proptosed eyes that have a good prognosis for vision and comfort (consensual PLR and voluntary movement of the proptosed globe)
Pull eyelids up over the globe with three horizontal mattress sutures and stents (distribute suture tension across lid margin to reduce pressure necrosis)
***DO NOT attempt to push globe back into the socket, normal position should be resumed once inflammation resolves |
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Term
| How long should a temporary tarsorrhaphy be left in place? What medical treatments should be given during this time? |
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Definition
Temporary tarsorrhaphy should be left in place for 2-3 wks
medical management includes systemic antibiotic and anti-inflammatories, and topical antibiotics and atropine applies to the medial canthus
*** + e-collar |
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Term
| Which has a better prognosis following surgical replacement (temporary tarsorrhaphy) of a proptosed globe, vision or preservation of the globe? |
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Definition
| Better prognosis for preservation of the globe, visual prognosis dependent upon serverity of underlying injury |
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Term
| What is the most common orientation of strabisumus following globe proptosis and why does this develop? |
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Definition
| superiolateral strabismus is most common as the medial rectus and ventral oblique muscles are most commonly traumatized in cases of proptosis |
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Term
| What is the etiology of primary lens luxation? |
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Definition
anatomical abnormality lead to break down of zonular fibers that normally suspend the lens
**terriers are predisposed |
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Term
| Lens luxation can occur secondarily to what 4 pathologies? |
|
Definition
uveitis (inflammatory destruction of lens zonules)
cataracts (resorbing cataracts contract away from the ciliary body increasing tension on the zonules which can lead to rupture and lens luxation)
Glaucoma (increased tension on the zonules secondary to buphthalmos)
Trauma (usually SEVERE) |
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Term
| What opthalmic exam findings are consistent with anterior lens luxation? |
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Definition
| lens equator anterior to iris, cannot identify pupil margin, absent to very shallow anterior chamber (1st and 2nd purkinje images are very close together) |
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Term
| What opthalmic exam finding is present in cases of both anterior and posterior lens (sub)luxation? |
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Definition
| aphakic crescent (crescent shaped area within the pupil that is devoid of lens) |
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Term
| What does the term irdodonesis describe? |
|
Definition
shaking/quivering of the iris with movement of the eye
**secondary to lens luxation |
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Term
| What does the term phacodonesis describe? |
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Definition
shaking/quivering of the lens with eye movement
**secondary to lens luxation |
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Term
| What are two potential sequelae to primary lens luxation? |
|
Definition
uveitis and glaucoma (pupillary block or narrowed iridocorneal angle)
**emergency, can rapidly lead to blindness |
|
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Term
| T/F: chronic primary lens luxation or secondary (sub)luxation is a surgical emergency |
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Definition
FALSE
**by the time these patients present eye is no longer visual |
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Term
| What is an acceptable site for venipuncture in small mammals (mice, guinea pig etc.) |
|
Definition
| orbital venous plexus (located in the medial orbit) <-- can result in excessive hemmorrhage during enucleation so subconjunctival approach is preferred |
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Term
| What are three unique features to the lacrimal system in rabbits? |
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Definition
| harderian gland contributes to tear production, tears have a milky appearance, lack a superior nasolacrimal punctum |
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Term
| Why are rabbits predisposed to dacryocystitis (inflammation of the nasolacrimal system)? |
|
Definition
the nasolacrimal duct is torturous with abruptly narrow regions where it passes through foramen in the maxilla and courses dorsal to tooth roots <-- often inflammation extends from tooth root to duct, or malocclusion retropulses tooth roots into the maxilla impacting the duct
**purulent ocular discharge that can be expressed from the inferior puntum |
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Term
| How do you diagnose and treat dacryocystitis in a rabbit? |
|
Definition
note purulent occular discharge that can be expressed from inferior punctum -->cannulate inferior punctum and flush duct with saline --> collect sample for culture and sensitivity -->infuse duct with gentamicin/fluoroquinolone opthalmic solution + topical antibiotic solution + systemic antibiotics (enrofloxacin)
**may need to flush nasolacrimal duct multiple times to resolve |
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Term
| What is another name for Rabbit Pseudopterygium? What impact does this condition have on vision? |
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Definition
| aka. aberrant conjunctival overgrowth (a fold of conjunctive grows over the surface of the cornea <-- non-adherent but can compromise vision if extensive) |
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Term
| What treatment options exist for Rabbit pseudopterygium? |
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Definition
surgical excision
likely to regrow, topical cyclosporine A may help prevent recurrence |
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Term
| T/F: "fatty eye" and "pea eye" in guinea pigs are benign conditions that do not require treatment |
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Definition
TRUE
fatty eye = subconjunctival fat deposits
pea eye = hyperplastic lacrimal or salivary gland nodules <-- if irritated can be treated with lubricating solution/ointment |
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Term
| T/F: every time a snake undergoes ecdysis (shed their scales) the spectacle overlying the eye should also be shed |
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Definition
FALSE
**superficial keratin layer overlying the spectacle is shed with ecdysis but the spectacle itself remains |
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Term
| What is the typical presentation of nasolacrimal obstruction in a snake? |
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Definition
pseudo buphthalmos due to accumulation of lacrimal secretions within the subspectacular space
**often occurs secondary to oral disease as nasolacrimal duct drains into the mouth in snakes |
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Term
| What is the most common etiology of retained spectacle in snakes? |
|
Definition
HUSBANDRY (low temp, low humidity)
also generalized skin disease, mite/tick infestation, previous spectacle trauma |
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Term
| What is the best treatment for retained spectacle in a snake? |
|
Definition
mist or soak, increased environmental humidity
**not recommended to remove with forceps as too much risk for ocular trauma |
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Term
| What is the pathognomonic presentation of a turtle with hypovitaminosis A? |
|
Definition
eyelid edema --> severe perioccular swelling, chemosis, conjunctival hyperemia
due to squamous metaplasia and dyskeratosis of orbital lacrimal and harderian glands with obstruction, swelling and dry eye, very prone to developing secondary bacterial conjunctivits |
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Term
| What differences in PLR are noted in avian species compared to mammals? |
|
Definition
brisk direct PLR (iris sphincter muscle is skeletal in birds)
No indirect PLR (100% decussation of nerve fibers at optic chiasm)
**if an indirect response is noted it's due to direct stimulation of contralateral retina by light passing through the very thin interorbital septum |
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|
Term
| What are three features unique to avian eyelids? |
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Definition
| no meibomian glands, filoplumes instead of cilia along lid margins, lower eyelids are more mobile that upper |
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Term
| What is the anatomic term for the leading edge of a bird's third eyelid? |
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Definition
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Term
| T/F: birds usually blink with just their third eyelids |
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Definition
True
**can also be unilaterally or bilaterally |
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Term
| What anatomic structure is responsible for the variable unique shapes of the globe that are present in birds (flat,globose, or tubular)? |
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Definition
scleral ossicles (composed of interdigitating pneumatic bones that form a ring at the anterior globe)
**may need to fracture these bones in order to perform an enucleation |
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Term
| Because birds have a striated iris sphincter muscle (as brisk PLR) how can you achieve mydriasis in these species? |
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Definition
NOT atropine (anticholinergic)
General anesthesia, curariforms (muscle blocking agents <-- administered via intracameral injections), topical phenylephrine (risk of systemic adverse effects)
**usually not necessary for routine fundoscopy (and too risky) |
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Term
| What is a normal structure in birds located in the posterior uvea at the optic nerve head? |
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Definition
| Pectin (we don't really know what it does) |
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Term
| What are four differentials for exophthalmos in birds? |
|
Definition
infraorbital sinusitis (bacterial or fungal)
vitamin A deficiency (hyperkeratotic sinus granulomas)
Cysts
Neoplasia |
|
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Term
| Keratoconjunctivitis and lime green urates in a bird are consistent with what bacterial infection? |
|
Definition
Chlamydophila psittaci
**Zoonotic and Reportable, DX with conjunctival/cloacal/choanal swabs and PCR/cytology (intracytoplasmic inclusion bodies) |
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Term
| Proliferative scaly lesions located periorbitally, on the beak, vent, and legs in a parakeet are most likely due to what parasite? |
|
Definition
| knemidokoptes pilae (aka scaly face mite) |
|
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Term
| What features of the equine eye allow for such a wide visual field (350 degrees)? |
|
Definition
nasal extension of the retina
lateral position of the orbits
horizontal shape of the pupils |
|
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Term
| What two colors can horses see? |
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Definition
|
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Term
| What are two locations for nerve blocks in order to facilitate the ophthalmic exam (esp. IOP) in horses? |
|
Definition
palpebral branch of auriculopalpebral nerve (blocks motor function to orbicularis oculi muscle <-- blink)
frontal nerve aka. supraorbital nerve(blocks sensory to upper lid) |
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Term
| What structure is very important to assess in equine pre-purchase exams? |
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Definition
| Always retropulse the globe to examine the 3rd eyelid for squamous cell carcinoma |
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Term
| T/F: KCS is uncommon in horses |
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Definition
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Term
| What are two historical and PE findings consistent with fungal keratitis in horses? |
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Definition
eyes are very painful even though pathologically they don't look that bad
history of topical steroid administration
(also, often multiple ulcers/satellite lesions, melting ulcers, "cake frosting" <-- mat of fungal hyphae) |
|
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Term
| What is the defining feature of an equine corneal stromal abscess? |
|
Definition
Flourescein negative at presentation
**inciting trauma innoculates corneal stroma with bacteria or fungi, surface epithelial defect heals over, 1-2 week and stromal abscess develops) |
|
|
Term
| What is the best medical treatment for equine bacterial stromal abcesses? |
|
Definition
chloramphenicol (broad spectrum, can penetrate the intact corneal epithelium)
**medical tx alone is often prolonged (3-4 months) and risk to owner of aplastic anemia from chloramphenicol (wear gloves when administering) |
|
|
Term
| What can you add to topical antifungals to increase their penetrating ability when treating equine corneal stromal abscesses? |
|
Definition
|
|
Term
| When is surgical treatment of stromal abscesses indicated? |
|
Definition
| if the lesion is <10 mm in diameter |
|
|
Term
| How can you lower the risk of corneal ulceration developing secondary to subpalpebral lavage tube placement? |
|
Definition
| place in the inferior-medial eyelid --> footplate is prevented from contacting the cornea by the third eyelid |
|
|
Term
| What is the most common corneal tumor/location in horses and cows? |
|
Definition
| Squamous cell carcinoma, located at the temporal limbus |
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|
Term
| What fundic lesion is commonly seen in association with equine recurrent uveitis? |
|
Definition
| chorioretinal scarring distributed around the optic nerve head in a "butterfly lesion" |
|
|
Term
| What can be a negative prognostic indicator for vision in horses with equine recurrent uveitis? |
|
Definition
| positive leptospira titers (this bacteria has antigen epitopes similar to those of lens and cornea proteins--> can incite an autoimmune response) |
|
|
Term
| What steroid should never be used to treat inflammation in the eye? |
|
Definition
hydrocortisone (too weak to penetrate the globe of the eye)
**use prednisolone or dexamethasone instead
******but NO steroids if cornea is ulcerated**************** |
|
|
Term
| What is a surgical treatment that can be used to prevent and/or reduce recurrence of uveitis in ERU horses? |
|
Definition
sustained-release cyclosporine implant
**intraocular delivery of immunosuppressant drug for 2-3 years <-- can place a second implant at this time if it is effective |
|
|
Term
| What is the number one cause of cataracts in horses? |
|
Definition
| Post-inflammatory (so...ERU) |
|
|
Term
| What is a common cause of traumatic optic neuropathy in horses? |
|
Definition
blunt trauma to the head (esp. poll) causes optic nerve stretching secondary to countre coup of the brain within the calvarium
**guarded prognosis for vision |
|
|
Term
| What optic nerve head change is an incidental finding in aged horses and has no impact on vision? |
|
Definition
proliferative optic neuropathy
(white/grey material extending into the vitreous from the optic nerve head in a normally visual eye) |
|
|
Term
| What are three occular manifestations of systemic hyperlipidemia/hpyerlipoprotinemia? |
|
Definition
arcus lipoides (accumulation w/in cornea, sparkly white, typically bilateral)
lipid aqueous (blue grey aqueous flare secondary to break down of blood-aqueous-barrier and leakage of serum lipids into the aqueous chamber)
lipemia retinalis (retinal vessels look pink and creamy)
DX: serum chemistry, 12 hr fasted lipid panel |
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|
Term
| T/F: diabetic retinopathy is uncommon in dogs and cats, this disease is characterized by multifocal retinal hemorrhages with infarction and edema |
|
Definition
TRUE
**takes 3-5 years to develop |
|
|
Term
| What is the earliest visible indication of a forming diabetic cataract? |
|
Definition
| lens vacuoles --> these cataracts are rapidly progressive, often separated Y sutures are appreciable due to fluid accumulation within the lens (ie. intumescent cataract) |
|
|
Term
| What is the rate limiting enzyme in lens glucose metabolism? |
|
Definition
|
|
Term
| What is the pathogenesis of hypertensive chorioretinopathy? |
|
Definition
Protein exudes through vascular walls (secondary to systemic hypertension) which become thickened (box-caring and increased tortuosity of retinal vessels), subretinal serosal fluid accumulates (raised hyopreflective areas of the tepetum) --> retinal detachement (vascular membrane visible within the pupil on direct examination)
**usually occurs in older cats |
|
|
Term
| T/F: controlling blood pressure in patients with hypertensive chorioretinopathy may result in retinal reattachment and restoration of vision (if caught early enough <3 wks) |
|
Definition
TRUE
**caveat: retina may still slowly degenerate over time |
|
|
Term
| What is one of the most common causes of conjunctivitis in small animals? |
|
Definition
atopy
**tx allergies systemically + topical antihistamines and frequent cleaning to flush antigens out of the eyes |
|
|
Term
| What two clinical signs are indicative of uveodermatologic syndrome? What is the tx? |
|
Definition
bilateral panuveitis with exudative retinal detachement
depigmentation of the skin and hair (often muzzle and oral mucus membranes)
tx with long term systemic immunosuppression |
|
|
Term
| What species is prone to ocular involvement of metastatic pulmonary carcinoma? |
|
Definition
| cats ---> results in ischemic chorioretinopathy (large irregular areas of tapetal necrosis, hemorrhage, and retinal detachment secondary to infarction (choroidal vessels are occluded by neoplastic cells)) |
|
|
Term
| What is the most common ocular manifestation of neoplasia in a dog? |
|
Definition
lymphoma
eyelid mass, conjunctival infiltrate, iris lesions, anterior and posterior segments of the eye, optic neuritis (often perivascular distribution to the metastatic lesions) |
|
|
Term
| What infectious agent is responsible for Blue Eye in dogs? |
|
Definition
Canine adenovirus type 1
**arthus rxn (immune-complex)within corneal endothelium --> anterior uveitis and corneal edema (BLUE)
no longer very common due to CAV-2 being used in vaccines at this point |
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|
Term
| For ALL ophthalmic solutions how many drops is one dose? |
|
Definition
|
|
Term
| What formulation of topical ocular medication is to be avoided in cases with present or impending perforation? |
|
Definition
ointment
**also apply ointments last because they impede absorption/delivery of solutions once they have been applied to the eye |
|
|
Term
| What topical antibiotics should be avoided in cats? |
|
Definition
|
|
Term
| T/F: a good way to treat infectious uveitis is with topical antibiotics |
|
Definition
FALSE
**must use systemic antibiotics!! |
|
|
Term
| T/F: DO NOT combine bacterio -statics and -cidals |
|
Definition
|
|
Term
| What is the only effective way to manage fungal uveitis? |
|
Definition
| Systemic antifungal therapy |
|
|
Term
| Why should you not used proparacaine or other topical anesthetics for analgesic treatment of painful corneal diseases? |
|
Definition
| repeated application of these drugs is toxic to the corneal epithelium --> melting to perforative ulcers |
|
|
Term
| What are contraindications to the use of mydriatics (pupil dilators)? |
|
Definition
glaucoma (dilated pupil compresses the irdocorneal angle)
KCS (anticholinergics decrease lacrimal secretions) |
|
|
Term
| T/F: topical corticosteroids can be used in conjunction with topical NSAIDs and/or systemic steroids/NSAIDs |
|
Definition
|
|
Term
| T/F: topical NSAIDs are useful for the medical management of chorioretinitis |
|
Definition
FALSE
**topical NSAIDS can penetrate the cornea to tx anterior uveitis but systemic anti-inflammatories are necessary to address problems in the posterior segment of the globe
****note, topical NSAIDs to delay corneal wound healing, but nothing like corticosteroids |
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