Refractive Surgery Flashcards by Oliver Fischer

Diagnosis

epithelial ingrowth

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When can epithelial ingrowth be observed?

peripheral nests of epithelial cells

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What is keratophakia

central lamellar keratectomy with placmement of a plus-powered lens intrastromally

corrects hyperopia and presbyopia

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occurs 10 years after radial keratotomy (RK)

progressive hyperopia

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What change in an arcuate keratotomy procedure might result in overcorrection

incision placed at a smaller optical zone

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Candidate for LASIK?

No, KCN is CI to refractive surgery

(inferior steepening on corneal topography)

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Why is laser refractive surgery CI in patients with poorly controlled connective tissue dusorders? Examples

unpredictable wound healing

SLE, RA

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Are collagen vascular diseases an increased risk of ectasia

NO!

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Stromal bed thickness (RSB) in which ectasia are more likely to occur

less than 250 um, however thicker RSB is not a guarantee that ectasia will not develop

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Pregnancy and refractive surgery

Wait 3 months after delivery and cessation of breastfeeding

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Diagnosis

Treatment

Stage IV Diffuse Lamellar Keratitis

lifting the LASIK flap, irrigating, starting corticosteroid drops

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Stage 1 DLK

scattered interface opacities in the periphery

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Stage 2 DLK

scattered interface opacities centrally

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Stage 3 DLK

scattered interface opacities that have coalesced

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Stage 4 DLK

corneal scarring or melting

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Treatment for Stage 3 and 4 DLK

lifting flap, irrigating, intensive topical corticosteroid treatment

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Disorder that disrupts Placido disk-based topography measurements of the corneal curvature

DRY EYE

quality of the air-tear film interface

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Risk factor for myopic patient undergoing refractive lens exchange with a monofocal lens

increased risk of retinal detachment

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Definition of nanophthalmos and risk factors

AL < 18mm

choroidal detachment

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High myopia

axial length of 26 mm or greater

risk for RD

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Biomechanical property of cornea is responsible for greater effect of refractive ablation under lamellar flap compared to surface ablation

nonuniform load

(200 lamellae of collagen fibrils; packing is denser in anterior 2/3 of cornea

anterior also stronger because of differences in glycosaminoglycans

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When offering monovision who desires near and distance vision. What refractive error differential typically provides a well-tolerated balance of distance and near vision

Dominant eye: distance

Non-dominant eye: target of -1.25 D to -2.50 D

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Clinical trials on conductive keratoplasty have found what on the long-term effectiveness and stability of this procedure

Regression was found in treatment of hyperopia and presbyopia

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Piggyback lenses developes a visually significant interlenticular membrane. Treatment?

removal of lenses

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Interlenticular membranes occur between these types of implanted lenses

2 acrylic IOLs, especially if both implanted in capsular bag

Corneal inlays are approved by the US FDA for treatment of what condition?

early to moderate presbyopia

What characterizes pressure-induced stromal keratitis (PISK)?

**It is a steroid response with elevated IOP after LASIK**

Diagnosis Treatment

**Pressure-induced stromal keratitis** (figure) fluid cleft in the flap interface resulting in artificially low pressure when checked by applanation. **Tx**: rapid tapering or D/C steroid drops and starting IOP lowering drops If untreated -\> results in severe glaucomatous visual loss

Orthokeratology involving overnight use of RGP lenses can help with temporary reduction of what problem?

low amounts of myopia (up to -6.00 D) low astigmatism 1.75 D

What feature is commonly found in patients with LASIK flap macrostriae

Macrostriae involve the full thickness of the LASIK flap

Diagnosis

**macrostriae** occur when a LASIK flap is not positioned correctly or slips postoperatively involve FULL-THICKNESS undulating stromal folds of lasik flap

mechanism of femtosecond laser interaction with tissue

photodisruption

Expected in infectious keratitis but not diffuse lamellar keratitis

infectious: inflammation extending beyond the flap edge. 2-3 days s/p LASIK DLK: infalmmation at periphery of flap decreases towards center

Binocular diplopia s/p LASIK

decompensated phoria

Keratometry readings that result in poor-quality vision after refractive surgery

\<34.00D and higher than 50.00 D

Why are IOL calculations difficult to accurately obtain in someone who has had laser refractive surgery?

Relationship between anterior and posterior cornea has changed

MOA KAMRA corneal inlay for near vision

pinhole effect

Diagnosis Definition

**Diffuse lamellar keratitis (DLK)** is a sterile inflammatory response seen in flap interface after LASIK Cause: response to variey of mechanical and toxic insults

What post-IOL implantation complication is less likely

**RARE: cataract formation** **Common:** endothelial cell loss, glare, starbursts, halos

Primary difference between femtosecond lenticule extraction (FLEx) and small-incision lenticule extraction (SMILE)

**flap creation** SMILE - femtosecond, avoids flap FLEx - femtosecond, flap

Tx for this condition

**Buttonhole s/p LASIK** replacement of flap and bandage contact lens attempt LASIK after 3 months with thicker flap or PRK

Myopic patient shows 1.5 D more myopia on wavefront measurement than on MR. Why?

Patient is **accommodating** during analysis Should be within 0.75 D of each other. If not, repeat

post-LASIK myopic shift with onset of with-the-rule astigmatism

post-LASIK ectasia

Patient with free cap after attempted cutting of LASIK flap, what treatment would you recommend?

Place corneal cap in moist chamber and proceed with tretment if stromal bed is large enough BCL placed until endothelial pump can secure cap

Excimer laser removes corneal tissue by what light-tissue interaction, what wavelength of light

**Photoablation; 193 nm** ## Footnote argon-fluoride excimer

IOP in post-LASIK patient

true IOP may be higher | (Goldman assumes CCT of 520 microns)

Increased rate in spherical aberration in patients with postoperative keratometry in these values

less than 34.00 D or greater than 50.00 D

Tx for persistent epi defect following PRK

punctal occlusion

Waelength of energy when applied to cornea is characterized by high energy and precision, low penetration of tissue and limited thermal spread

193 nm Highly suitable for ocular surface - photoablation

transforms tissue into plasma with high pressure and temperature and leads to rapid tissue expansion

femtosecond laser generates 1053 nm

Wavelength of collagen cross-linking

365 nm (ultraviolet A)

wavelength and laser-tissue interaction of Holmium-YAG laser

2.13 um - photothermal effect

How does conductive keratoplasty affect the cornea

it works by **increasing the curvature of the central cornea**

Material intrastromal corneal ring segments are made from

polymethyl methacrylate (PMMA)

how long should patients be advised to avoid using rigid contact lenses soft CL?

**3 weeks** for RGP **2 weeks** soft toric **3 days to 2 weeks** for soft CL

1 week s/p PRK. Diagnosis

sterile infiltrates AW postoperative CL use and topical NSAID drops

Inadequate suction is mostly to cause what complication during construction of a LASIK flap with mechanical microkeratome?

**an incomplete flap**

To improve vision associated with myopic astigmatism caused by post-LASIK corneal ectasia, what is an appropriate initial option

**rigid gas-permeable contact lens**

gold standard for correction of reduced vision due to ectasia

RGP contact lenses

used to reduce the incidence of corneal haze after PRK

mitomycin C

1 month s/p bilateral LASIK 25 yo M c/o 3-days pain and redness Treatment?

**Lift LASIK flap and obtain cultures - including fungi and mycobacterium** (note: K infiltrate, diffuse haze under flap, hypopyon suspicious for post-lasik microbial keratitis

Major differences between arcuate keratotomy (AK) and limbal relaxing incisions (LRIs)

Arcuate incisions are made at a **greater relative corneal depth** made in midperiphery (7-9 mm optical zone)

Role of vitamin B2 in corneal crosslinking

Riboflavin (Vitamin B2) generates singlet oxygen and superoxide anion free radicals

Variable affects the depth of laser ablation required to treat a given degree of myopia

**optical zone diameter** Munnerlyn formula Ablation Depth (um) ~Degree of myopia (D) x (optical Zone diameter)^2 (mm)/3

Condition alloplastic corneal inlays are used to treat

**presbyopia**

Cx a/w posterior chamber phakic intraocular lenses (IOLs)?

**endothelial cell loss** ## Footnote Cataract formation, endothelial cell loss, RD - all reported in patients who undergo posterior chamber phakic IOLs