What are the 2 basic forms of refractive surgery?

what are the 5 keratorefractive procedures?

Lasers

Incisions

Thermal

Implants

Non-Laser Lamellar surgery

what are the 2 lamellar (scleral) procedures?

Secondary Lenses

Scleral RElaxation or expansion

2 main lasers used in refractive surgery?

What is the range of correction for astigmatic refractive procedures (AK, PRK, & LASIK)?

AK:  0-2 ideal and 2-3 extended

PRK: 0-3 ideal and 3-4 extended

LASIK: 0-6 ideal and 6-8 Extended

What is the range for spherical correction for refractive procedures?

LASIK:+3 to-10 ideal & extended to +5 and -14

PRK: plano to -5 & extended to +4 and -10

LTK: plano to -3

RK: plano to -4

ICR: plano to -4

PHAKIC IOL: +4 to +10 & -9 to -22 and extended down to -5

RL: +4 to +10 & -9 to -30

What are the ocular surface disease considerations in refractive surgery?

1. Blepharitis and Chronic Blepharitis

2. Blepharoconjunctivitis

3. Meibomian gland dysfunction and meibomianitis

4. Acute bacterial keratitis 

5. Acute and Chronic bacterial Conjunctivitis

6. Viral Keratitis and Conjunctivitis

7. Dry Eye

8. Allergic Conjunctivitis (5 types)

Blepharitis

• Acute, chronic or blepharoconjunctivitis
• erythema ad ulceration of eyelid
• Staphylococcal etiology
• Tx with tobradex for 2 wks
• Chronic: typically seen w/ concomitant meibomianitis(tx w/ doxycycline); Symptoms of burning, FBS, and crusty lids in AM; Signs-fibrin collarette, thickening eyelid margin and madarosis(loss lashes
• Blepharoconjunctivitis: palpebral and/or bulbar hyperemia and limbal papillae or phlyctenules

Meibomian Gland dysfunction and meibomianitis - S/S and cornea involvment

Symptoms: Fluctating vision which changes with blinking, burning, FBS

Signs: Foamy tear film (esp outer fornix), insippiated meibomian glands (yellow thin column seen just under skin); hyperemia and thickening of eyelid margin

Cornea Involvment: Peripheral neovascular, Pannus (Flat corneal opacification w/ normal limbal blood vessels growing in it, usu at 3 and 8), Epi erosions, marginal ulceration, phlyctenular disease

Sebaceous gland dysfunction often seen with MGD-assoc w/ seborrheic dermatitis, rosacea, and acne vulgaris

Tx w/ doxyxyxline &/or erythromycin/bacitracin(cont post op)

Important b/c meibomian secretions thought responsible for diffuse lamellar keratitis

Acute Bacterial Keratitis

Typ caused by: Streptococcus, micrococcaceae, psuedomonas aeruginosa, & enterobacteriaceae

Varied course: epi keratitis to edema to hypopyon

Risk Factors: Trauma, HSV keratitis tx w/ corticosporins, persistent epi defect

Acute Bacterial Conjunctivitis

• Most common ocular suface organisms: Staphylococcus epidermidis and Corynebacterium
• Caused by: Staphylococcus aureus & streptococcus pneumoniae
• S/S: tearing, redness, mucopurulent discharge, crusty eyelids in AM; subconj hemorrhage; conjunctival membrane formation
• Tx: Bacitracin (gram positive antibiotic)

Chronic Bacterial Conjunctivitis

• Acute that last > 3 weeks
• Usually - Staph Aureus
• Can be: Moroxella lacunata, serratia marcescens, escherichia coli, proteus species

3 Major etiologic agents causing viral keratitis and conjunctivitis?

1. Adenovirus
2. Herpes Simplex
3. Varicella Zoster

Adenovirus can cause?

• Acute nonspecific follicular conjunctivitis: s/s=red, watery, irritation
• Epidemic KEratoconjunctivitis (EKC)
• Pharyngoconjunctivitis fever (PCF)

Epidemic Keratoconjunctivitis caused by?? s/s??

• Caused by: adenovirus 8, 19, and 37
• Usually bilateral
• Extremely contagious
• S/S: itch, red, watery, stuck shut eye in am
• can lead to vision loss
• 80% ptnts have corneal signs: diffuse SPK for 3-5 days amd SEI later
• Avoid topical steroids bc viral shedding
• CI if SEI's present

pharygoconjunctival fever caused by?? s/s??

• Caused by: adenovirus 3,4, and 7
• Usu mild and bilateral
• S/S: red, watery, irritation, fever, pharyngitis, lymphadenopathy
• Milder than EKC
• Corneal sign typically include mild SPK

Herpes simplex presentation and assoc w/??

• Corneal presentation ranges from SPK to dendritic KEratitis
• Assoc W/: Preauricular adenopathy, mild papillary or follicular conjunctivitis, uveitis
• CI: History of HSV keratitis
• If surgery, pre op tx w/ oral acyclovir BID 

varicella zoster disease entities??

• Herpes zoster: stromal keratitis, corneal scarring, neo, neurotrophic keratitis; ABSOLUTE CI for surgery
• Chicken pox

what are some etiologies for dry eye? 

Age, dry environment, hormones, meds, CL, blepharitis, lasik (corneal nerves severed), autoimmune (RA)

What are the factors contributing to inflammatory response of dry eye??

Abnormal tears lead to:

• Inc osmolarity of tear film
• Reduced turn over of tear film
• Ocular irritation
• Inc cytokines

What are the types of Dry Eye?

Evaporative dry eye

Tear-deficient dry eye: sjogren and non-sjogrens

Describe evaporative dry eye

blepharitis

rosacea and MGD

infrequent blink

eyelid disorders

ocular surface disease

environmental factors (low humidity, ac, fans, pollution, alcohol, CL)

meds (antihist, HTN, BCP, ulcer meds, visine, antidepressents)

describe sjogrens syndrome - tear deficient dry eye

Chronic systemic autoimmune affecting all moisture producing glands

Ptnts have dry mouth and dry eyes

SS-A or SS-B, ANA, or RF can be found

Various CT diseases(RA)

describe non-sjogrens syndrome-tear deficient dry eye

lacrimal gland dysfunction caused by various diseases (sarcoidosis, trachoma, vit A deficiency, trauma, etc)

other causes: diabetes, CL, age, previous herpetic keratopathy/conjunctivitis)

5 major categories of allergic conjunctivitis?

1. Seasonal Allergic conjunctivitis (SAC)
2. Perennial allergic conjunctivitis (PAC)
3. Vernal Keratoconjunctivitis (VKC)
4. Atopic Keratoconjunctivitis (AKC)
5. Giant Papillary Conjunctivitis (GPC)

1. Seasonal Allergic Conjunctivitis??

Symptoms  during defines period of year

     Spring-tree pollen

     Summer-grass pollen

     winter-Usu asymptomatic

Hallmark symptoms-Itching

Hallmark signs-conj injection, chemosis, eyelid edema

2. Perennial Allergic Conjunctivitis- when are symptoms?? what are allergens??

• Symptoms last Whole Year
• Allergens: pet dander, dust mite, Cockroaches

3. Vernal Keratoconjunctivitis- characterized by??, assoc w/?? S/S?? what are the 2 varieties??

• characterized by: chronic bilateral conjunctival inflammation
• Assoc w/: personal or family hx of atopy/ exclusively in warm climates
• Hallmark symptom: itch
• Symptoms: photophobia w or w/o blepharospasm, tearing, FBS
• Signs: usu seen in cornea and conj w/o eyelid involvment
• 2 varieties: Limbal and palpebral

3A. Palpebral VKC-hallmark sign??

• Hallmark sign: Giant papillae on upper tarsal conjunctiva W/O inferior involvment
• If large enough papillae can result in mechanical ptosis
• Mod to severe papillae make ropy mucous dischRge w/ lots of eosinophils

3B. Lmbal VKC-typically seen in who?? what type of papillae??info about?

usu in Dark skinned ppl

Gelatinous papillae

Horner-Trantas dots maybe w/i papillae

sheild ulcer from inflammatory mediators

SPK may coalesce to form large erosion

Vernal psuedogerontoxon (like arcus)

keratoconus usu from eye rubbing

4. Atopic Keratoconjunctivitis-defn? assoc w/?? onset?? prevelence in genders?? ocular symptoms?? ocular signs??

• defn: bilateral inflammation of conj and eyelids
• Assoc w/: atopic dermatitis (STRONG), asthma, and rhinitis
• Common hereditary disorder
• Oset: typ iin childhood, peak age incidence is 30-50, affects 3% population and 25% of those have ocular involvment
• Type I hypersensitivity
• Symptoms: itch, tearing, ropy discharge, burn, photophobia, dec vision
• Signs: chronic SPK, persistent epi defects, cornea scar or thinning, keratoconus, cataracts, symblepharon

5. GPC- defn?? classic finding?? symptoms? diagnosis?? soft vs GP cL area involved? other causes??

• defn: immune mediated inflammatory disorder of superior tarsal conj; GPC shows rxn to various FB
• Classic find: giant papillae w/ creamy white center
• Symptoms: dec CL tolerance, lots CL movement, high riding CL, itch, mucous, blur, conj injection
• diagnose: min diam 0.3mm+symptoms
• Soft CL: seen more at folf of everted lid
• GP CL: seen more at leading edge where interaction w/ GP is greatest
• Other causes: Ocular prostheses, extruding scleral buckles, exposed sutures, filter blebs

how many ppl in N america have refractive error??

prevalence of myopia and hyperopia??

Ocular refractive system?

• 40% ppl in N america have refractive error
• 29% mypoic and 49% hyperopic
• anatmy of refractive system: cornea (60-70%), Lens (30-40%), globe can grow in length up to 7mm in compensatory, disease can interfere with these

What is microcornea?

• corneal diameter <10mm
• microphthalmos-small eye and abnormal
• Nanophthalmos-small eye and normal
• Non progressive
• Unilateral or bilateral
• Flat cornea - leads to hyperopia
• risk for narrow angle glaucoma 

What is Megalocornea?

• cornea diam > or= 13mm w/ norm thickness adn curvature
• nonprogressive, bilateral and symmetrical
• 90% are MALE
• assoc w/: ectopia lentis, phacodenesis, Iridodenesis
• rule out: bupthalmos (from congenital glaucoma)

What is Sclerocornea?

• cornea becomes sclera
• can be peripheral or total
• excessive flat cornea: 20-35D
• Nonprogressive, bilateral and symmetrical
• assoc w/: cornea plana

What is Keratoconus?

• #1 thing look for before refractive surgery
• DEFN: ectasia secondary to progressive corneal thinning
• bilateral and symmetrical
• Hx of eye rubbing
• 16-25 yo
• Inf corneal steepening, irregular astig
• Fleishers ring-annular ring from hemosiderin
• Vogts striae-dissapears w/ pressure
• munsons sign-advanced cases, protruding lower lid in downgaze
• corneal hydrops-Decemets rupture, leads to edema, scar, and dec VA

what is keratoglobus?

• entire globe protrudes forward present at birth
• bilateral and nonprogressive
• entire cornea thins till 1/3 or 1/5 of norm
• K's are 50-60D
• maybe corneal hydrops
• corneal rupture from excessive thinning
• Penetrating keratoplasty typically needed

What is Pellucid Marginal Deeneration?

• bilateral, ASYMMETRIC, noniflammatory PERIPHERAL ectatic disorer
• typ starts inferior and extendes 4-8 oclock on cornea
• corneal protrusion sup to thinning
• charecterized by: irregular ATR, CRAB CLAW topo, inf thinning

Absolute CI for refractive surgery

• NEVER DO REFRACTIVE SURGERY
• Systemic immunologic: SLE, RA, polyarteritis nodosa(affects arterys and vessels), pregnancy(check 2 months post pardum), AIDS, uncontrolled diabetes
• Ocular disorders: Severe Dry Eye, chemical burns, keratoconus(maybe do intracorneal ring), all ectatic disorders, IRREGULAR ASTIG, cataract(Case dependent)

Relative CI for refractive surgery

• Steroid or vascular glaucoma, need to be very careful with IOP spikes
• Cataract-weigh risk/benefit
• Monocularity
• Patients 18-21-only do if stable refraction
• diabetes
• corenal dystrophies and degenerations
• mild dry eye

what are the 8 preop exam requirements?

1. stable refraction

2. removal CL- soft:3-7days, soft toric: 7-0 days, GP:2-3 weeks, PMMA:4-6weeks

3. Keratometry: primary and up gaze, 36 to 48

4. Corneal topography: NO irreg astig or keratoconus or ectatic disease

5. Ocular dominance-esp for monovision

6. Pupil size: measure in mesopic and scotopic, avoid pupils > 6.5mm w/ traditional lasik (if do traditional rx alphagan P to dec pupil size at night)

7. Wavefront measurement: determine need for custom, ID's higher order abberations

8. Pahymetry: corneal thickness must be >500microns

Min stromal bed thickness needed after surgery = 250microns

most commonly used topo map in refractive surgery is??

tangential-want to know every ups and downs of the cornea

what is prolate and oblate?

prolate-steepest in center

oblate-flattest

Elevation Topography

• most popular-Orbscan
• calculated elevation change on ant and post cornea from a best fit sphere (ant=8.33 and post=6.88)
• If posterior flot is >0.04 than suspect keratoconus and do NOT do surgery

What can occur if do surgery with a posterior float > 0.04?

2 main types of abberations?

1. Chromatic: refractive index, color/freq

2. Monochromatic:

    primary:spherical (myopia and hyperopia), astig, coma, field curvature, distortion.

    Higher order: secondary astig, glare, shadows, halos

when is emmetropic eye free of abberations?

when pupil diam = 2.5mm

Wavefront Aberrometry

• determines optical abberations of an eye by calculating the exiting light from the eye
• the cutom lasik uses these results for refractive surgery
• Lasik and other surgerys can actually induce aberrations

what are the 2 basic type of microkeratomes?

laser and mechanical

each type has unique flap size, flap thickness, and hinge

What is the Mechanical Microkeratome?

• Peripheral part: suction ring, cutting head, central unit
• raises IOP 60-70mmHg
• Less expensive
• complications: free caps, buttonhole caps, epithelial erosions, diffuse Lamellar keratitis
• Flap thickness=160microns

What is the laser microkeratomes?

• AKA INTRALACE
• delivers ultrashort pulses at a wavelength of 1053nm (infared, which does NOT affect cornea)
• these pulses form cavitation bubbles which seperates the tissue
• Only raises IOP 30mmHg
• flap thickness=110microns
• Advantage: better control of flap thick, hinge can be put anywhere, size easily adjusted
• disadvantages: more cost, more pain

What are the 4 types of interactions btwn cornea and laser radiation?

• absorbtion-main effect when wavelength is <350nm (photoablation)
• transmission-
• refleaction-no effect to cornea
• dispersion-no effect to cornea

Photoablation

• effect for refractive surgery
• uses UV light
• very superficial bc short wavelengths
• Tissue is Vaporized
• "flying spot" excimer laser reduce any thermal effect bc of very short pulsesand varying distances btwn spots
• thermal effect NOT strong enough to cauterize therefore bleeding occurs after application

Beam Delivery Systems - Full Beam

• early generation, less regular ablation surface,
• Adv: RAPID, low sensitivity to decentering
• Disadv: thermal effects
• Produces SHOCK WAVE
• refractive mask must be used (like a cookie cutter)

Beam Delivery Systems - Scanning Slit

• still has thermal effects
• rectangle beam created with diaphragm
• attached to rotary and scans in all directions
• all types refractive error can be treated
• adv: rapid and low sensitivity to decentering

Beam Delivery Systems - Flying Spot Delivery System

• uses center of a small circular beam
• tissue is ablated with many pulses
• spots are aeperated - AVOID thermal affects
• VERY sensitive to decentering - so use eye tracking
• Adv: produce asymmetric ablation profiles

Myopia LASIK

• Most common technique
• Cornea FLATTENED
• Ablation depth very important with high myopes
• following surgery cornea is OBLATE shaped
• increase in positive spherical aberrations

how much does traditional and custom laser remove?

traditional: 15 microns/diopter

Custom: 20-40 microns/diopter

Hyperopia LASIK

• Central cornea is steepened
• more challenging
• ablation zone around center-donut shaped
• edge of OZ thinnest
• has transition zone to blend
• outcomes best if <+4.00D
• corneal aberrations inc significantly , largest inc with spherical one
• PROLATE shaped after surgery

Custom LASIK

• used to dec aberattions
• Topography guided: used w/ flying spot, used when aberrations are mainly from corneal surface
• Wavefront Guided: used when aberrations are from all parts of the eye, creates "perfect eye"

Preoperative LASIK complications??

SPK or epi defect from allergic rxn from topical anesthetic

Microkeratome Complications?

1. irregular or incomplete flap formation: need to wait 3-6 months before another flap

2. Free Cap: blade passes all way through cornea, NO sutures needed, bandage CL

3. Buttonhole flap: blade come to surface and returns back under and creates hole in flap, WORST OUTCOME, provide chanel for epi ingrowth, abort procedure

4. Corneal Performation

5. Corneal epi defects-secondary to loose epi from excess anestheic or dry cornea, bandage CL

6. Corneal Bleeding: when blade contacts limbal vessels

7. Edematous Flap-excessive manipulation of flap

Photoablation Complications??

1. Central Islands-mostly caused by laser plume, classify by mm wide and D high, symptoms include irreg astig, monoc diplopia, loss BCVA, glare, Can also be from acoustic shock waves, bad laser, wound healing problems

2. Decentered Ablation Zone-can be mild, mod, or severe; symptoms are monoc diplopia, glare, halos; caused by eye drift or misligned laser

3. Flap Wrinkling-Intraoperative(surgeon misaligned flap) or postoperative (Patient by rubbing or pressure)

4. Interface Debris-caused by conj or skin epi cells, MEIBOMIAN SECRETIONS, swab debri, blade fragments, ocular surface mucous, lift flap and irrigate

Early Postoperative Complications

1. undercorrection-most common

2. Overcorrection-most common after retreatment for undercorrection

3. Dislodged Flap-most common w/i 24 hours; still susceptible 2-3months later

4. DIFFUSE LAMELLAR KERATITIS: "sands of sahara"; appears 1-3 days post op; Caused by interface debris; INFLAMMATION, use STEROIDS; symptoms include FBS, photophobia, tearing, pain. appears as white granular opacities NOT stains; has 4 stages

5. Bacterial Keratitis: most common caue is gram+ bacteria and mycobacteria; symptoms include pain, photophobia, dec VA, halos; tx 4th generation flouroquinolone

6. Epi Ingrowth-w/i one month post op; well defined edges

what are the 4 stages of DLK??

Stage 1: 1:50; Peripheral, 1-3 days post op; Tx 1% prednisolone

Stage 2: 1:200; Central diffuse; occurs 2-3 days post op; tx 1% prednisilone

stage 3: 1:500; central clumping; can occur 2-3 days post op; risk of inflammatory mediators and collagenolytic enzymes from PMN's; Tx lift flap, irrigate, also topical 4th generation flouroquinilone

Stage 4: 1:5000; Stromal Melt, can occur w/i one week post op

Late Post Operative Complications

1. Regression: usu hyperopic; bc wound ealing, latrogenic keratectasia, compensatory epi hyperplasia, lenticular nuclear sclerosis

2. Latrogenic Keratectasia: weakening of cornea's strength, 1wk to 2 years post op; myopic shift

3. Night Vision complaints: mainly glare or halos, pupils to big; Tx with alphagan P

PRK

• nonLASIK
• scaps off entire cornea, no flap
• if >70 microns removed need to rx Mitomycin C (MMC) to dec haze

LASEK

• non LASIK procedure uses alcohol to loosen surface cells, and are moved aside.
• 50 micron flap-no stroma only EPI

Epi-LASIK

Incisions

• RK-radial keratotomy
• late 70-80's; many spoke incisions made around cornea
• weakened peripheral cornea
• not done anymore

Implants

• ICR-Intraconeal Rings
• make tunnel in stroma and place rings
• corrects low myopia and if put onyl inferior corrects keratoconus