Contact Lenses III MT 1 - Dr. T's material
Contact Lenses III - Dr. T's material
 Study
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 Review All
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 Quiz!
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Radial incisions (4-8, 16, or 32) in the cornea with a scalpel to reduce its curvature describes what procedure? |
Radial Keratotomy (RK) |
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RK involves the reduction of the ___ height. |
sag |
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What does AK stand for? What is involved? |
Astigmatic Keratotomy. Same technique as RK, but to fix astigmatism. |
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Your patient said she had AK done a few years ago - you see horizontal incisions at the 6:00 and 12:00 positions. Was this a WTR or ATR cornea? |
WTR |
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What are the problems with AK and RK? |
- Less predictability (K depth) |
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T/F - Excimer lasers involve lots of heat therefore require constant irrigation to cool off the cornea. |
False - it is a "cool" laser |
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T/F - Ablation involves evaporation. |
False - ablation involves breaking of bonds |
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What does ASA stand for? What it is also known as? |
Advanced Surface Ablation, aka PRK (Photorefractive Keratectomy) |
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How does ASA work? |
Alcohol is used to loosen the epithelium, then an excimer laser is used to remove the epithelium. |
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What is the refractive error limit of ASA? |
Myopia up to -7.00 |
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(Review pros and cons of each surgery type) |
Just a reminder |
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T/F - ASA is ok for thin corneas. |
True |
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How long does the epithelium take to heal after ASA? |
1-2 weeks |
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What is the biggest and most frequent complication of ASA? |
Stromal haze |
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Which has a higher risk of infection and inflammation - ASA or LASIK? |
ASA |
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Which procedure involves the patient on steroids longer - ASA or LASIK? |
ASA |
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What is Mitomycin-C used for in ASA? |
Decreases occurrence of post-op corneal haze. |
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What does LASEK stand for? |
Laser Epithelial Keratomileusis |
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Describe the LASEK procedure. |
Alcohol soln is used to loosen the epithelium, then the epith is lifted back, the excimer laser sculpts the cornea, then a bandage CL is used until the epith heals (~1 wk). |
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Describe Epi-LASIK |
Same as LASEK but instead of alcohol soln, a blunt oscillating blade is used to create the corneal flap. |
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In order, which has the longest to shortest recovery in ASA, LASIK, and LASEK/Epi-LASIK? |
Longest to shortest recovery: ASA, LASEK/Epi-LASIK, LASIK |
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List in order of worst to best patient comfort: ASA, LASIK, LASEK/Epi-LASIK. |
Wost to best: ASA, LASEK/Epi-LASIK, LASIK |
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Describe the LASIK procedure. |
A microkeratome slices a flap of corneal tissue, which is folded back and an excimer laser reshapes the tissue. |
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What types of refractive error can LASIK be used for? |
Myopia, hyperopia, and astigmatism; hyperopia not as recommended as myopia. |
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How soon is vision functional in LASIK? How about full vision recovery? |
24 hrs for functional vision, 1 week for full recovery. |
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What is IntraLase? |
A bladeless technique that uses an infrared light beam to cut tissue (photodisruption); the laser forms microscopic bubbles of CO2 and water vapor - the bubbles interconnect to create a dissection plane. Basically a way to make the flap w/o a blade. |
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What are the advantages of IntraLase? |
- More ctrl w/ flap thickness & size; less flap thickness variability |
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What does CK stand for? |
Conductive Keratoplasty |
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What procedure was mentioned in the slides that is FDA approved for correcting presbyopia? |
Conductive Keratoplasty (CK) |
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How does CK work? |
Uses radio frequency energy to shrink areas of peripheral corneal collagen (due to its electrical resistance causing heat buildup); applied at points in a circular pattern, causing steepening of the cornea. |
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What refractive error range is CK approved for? |
+0.75 to +3.00 D with up to +0.75 D astig. |
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T/F - CK takes a long time for recovery. |
False - immediate recovery |
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T/F - CK has good patient comfort, besides FB sensation. |
True |
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T/F - CK requires AB and steroids for a long period after Tx. |
False - short term ABs and steroids |
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T/F - CK requires re-treatment. |
True - lasts only 3-5 yrs |
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T/F - CK involves corneal leukomas (scarring). |
True |
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T/F - CK involves a large optic zone in higher Rx's. |
False - a SMALL optic zone |
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What are INTACS? How does the procedure go? |
Intracorneal Rings Segments; two channels made in peripheral cornea by intralase or manual dissector, and small curved PMMA segments inserted into these tunnels. |
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What are INTACTS used for? |
Tx K thinning disorders e.g. keratoconus, PMD & Post-LASIK ectasia. Attempts to flatten and center the KC cone - arc shortening effect, and helps with rigid lens centration. Basically enables pt to fit RGPs. |
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What is the max K-value indicated for INTACS? |
57D |
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T/F - INTACS help halt/reverse progression of keratoconus. |
False |
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T/F - INTACS does not require additional visual correction. |
False |
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What does CLE stand for? |
Clear Lens Extraction |
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How does CLE work? |
Internal lens of eye is removed (as in cataract extraction) and a lens implant of another power is inserted. |
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When is CLE indicated? |
Pts over 40 w/ hyperopia (high myopia?) |
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What does PIOL stand for? |
Phakic Intra-Ocular Lens |
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How does PIOL work? |
The crystalline lens is still there, but an IOL is placed in front of or behind the iris; basically an internal CL. |
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What types of refractive error can PIOL correct? |
Hyperopia, myopia, and low astig. |
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What does CE stand for? |
Cataract extraction |
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What is custom LASIK? |
An aberrometer measures the amount of higher order aberrations (HOAs) and uses these measurements with the laser to correct the HOAs. |
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Compare wavefront guided vs wavefront optimized ablation. |
Guided = Tx refract error and pre-op HOAs; removes 22 um/D |
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What is active eye tracking? |
Maintains alignment of laser with eye movement |
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What is iris registration? |
Helps account for cyclorotation of the eye (since eye is cyclorotated when lying down) |
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What are the power ranges of LASIK and ASA (according to pg 10)? |
-11.00 sph and 6.00 cyl Depends highly on K thickness |
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Higher Rx corrections are indicated with which procedures? |
Clear lens extraction and phakic IOLs. |
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What is the typical treatment zone in conventional LASIK? |
6 mm |
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How much K thickness is removed per diopter in conventional LASIK? |
1 D = 12 um |
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What is the ideal flap thickness? |
125 um (intralase = 90 um) |
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What is the ideal corneal bed thickness? |
250 um |
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What is the ideal residual corneal thickness? |
125 um (flap thickness) + 250 um (corneal bed thickness) = 375 um |
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Larger Tx zones and custom ablations will remove (less/more) tissue. |
more |
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Your patient has a CCT of 475 um. His Rx is -6.00 OD, -8.50 OS. Can this pt get LASIK? |
OD: 6D x 12 = 72 |
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Your patient who is interested in LASIK has a 0.50 D increase in minus in his right eye. Should you wait it out or is it ok to proceed with LASIK? |
Wait for stability if you see a 0.50 D or greater change. |
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T/F - Diabetes is an absolute CI to refractive surgery. |
False - a relative CI |
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T/F - Dry eyes is an absolute CI to refractive surgery. |
True if severe |
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T/F - Irregular topography is a relative CI to refractive surgery. |
True - wait for stability |
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T/F - Previous corneal surgery is an absolute CI to refractive surgery. |
False |
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How soon should you wait for refractive surgery after pregnancy? Nursing? |
6 mo after birth or |
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How long do SCL wearers must be weaned off their lenses prior to refractive surgery? RGP wearers? |
SCL = 2-4 wks or until refraction is stable |
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T/F - It is not appropriate to make recommendations for ophthalmologists. |
True - we DO NOT make recommendations! |
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What is considered "stable"? |
2-3 repeatable refractions and topography, 2-3 wks apart |
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T/F - ABs are indicated the day before surgery. |
True - Zymar/Vigamox QID |
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How soon do you return to the surgical site after surgery? |
The next day for f/u |
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Outline the routine post-op schedule. |
1 day, 1 wk, 2 wks (optional), 1 mo, 3 mos, 6 mos; after this, yearly exams and DFE are highly recommended |
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What are common post-LASIK problems after 1 day? |
Dislodged flap, macro/micro-striae, dry eyes (severe w/ diffuse SPK), surgical debris |
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What are common post-LASIK problems after 1 week? |
DLK, epithelial ingrowth, under/overRx, glare/halos, dry eyes |
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What are common post-LASIK problems after 1 month or more? |
Regression, dry eye |
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When is GAT ok to do after the surgery? |
One week after. |
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If VAs are worse than 20/40 on day 1, what should you do next? |
Follow more closely |
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What kind of meds should be taken post-op? Dosage/length? |
ABs and steroids qid x 1 wk, ATs q2h |
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How long can you not rub your eyes after surgery? |
1 month |
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How long can you not swim/get water in your eyes after surgery? |
1 week |
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When can you start using eye makeup again after surgery? |
1 week |
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T/F - No heavy lifting >25 lbs within one month of surgery. |
False - one week |
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T/F - No running or any rigorous physical activity within one week after surgery. |
False - 3-4 days |
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T/F - A dislodged flap after will resolve itself. |
False - should be sent back to MD right away; encourage pt to keep eyes closed, NO proparacaine or cycloplegics. |
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How do you Tx macro-striae? |
If no visual disturbances, can be left alone. If decr BCVA, then flap must be refloated and smoothed. |
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What Sx is involved w/ macro-striae? |
Irreg astig, glare/halos, decr BCVA. |
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What Sx is involved w/ micro-striae? |
Usually no Sx |
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What is the biggest complication post-LASIK? |
Dry eyes |
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T/F - Dry eyes can cause the pt's pre-op Rx to come back. |
True - this is regression |
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T/F - If surgical debris is not affecting vision or healing, you can leave them alone. |
True - otherwise, flap is lifted and interface is cleaned |
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Why is it important to carefully monitor IOPs in the post-op follow-ups? |
Pt has been taking steroids. |
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What is DLK? |
Diffuse Lamellar Keratitis - granular material in the interface causing inflammation; results in progressively decreased VAs |
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How does DLK appear with staining? |
1+ = inferior SPK |
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How do you Tx DLK 1+? |
Can resolve w/o Tx, but can also increase steroid gtt regimen (Pred Forte 1% q2h) |
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T/F - DLK 2+ does not involve a decrease in BCVA. |
False - BCVA decreases slightly and also involves a mild hyperopic shift |
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How do you Tx DLK 2+? |
Pred Forte 1% : |
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T/F - DLK 3+ involves a further drop in BCVA and more (-) |
False - more (+) |
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How do you Tx DLK 3+? |
Immediate surgical intervention - float flap, irrigate, Tx w/ steroids |
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How does DLK 4+ present? |
Dense corneal haze; end stage, cornea melting or scarring (no AC rxn or hypopyon); BCVA 20/60 or worse (hyperopic irregular astig). |
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How do you Tx DLK 4+? |
Immediate surgical intervention - float flap, irrigate, Tx w/ steroids (same as DLK 3+) |
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What is epithelial ingrowth? |
Presence of epithelial cells in the lamellar surface post-LASIK usually within 1 wk to 3 mos; white to gray speckles, lines, strands, sheets. |
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What are the three methods of how epithelium is introduced to the interface (epithelial ingrowth)? |
1) Growth of solid sheet of peripheral epith beneath flap |
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How soon do you see epithelial ingrowth?* |
Can't detect until at least 1 week from surgery |
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T/F - Epithelial ingrowth is due to poor flap adhesion or alignment. |
True |
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What illumination is best for seeing epithelial ingrowth? |
Retroillumination |
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T/F - Epithelial ingrowth is always aggressive. |
False - can be sedentary or aggresive |
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T/F - Since the epithelium is growing over the flap in epithelial ingrowth, there is no staining. |
False - staining at the edge |
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1+ epithelial ingrowth is within __mm of flap edge, while 2+ is greater than ___mm of the flap edge. |
2, 2 |
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T/F - 2+ epithelial ingrowth involves no demarcation line. |
True - this indicates progression |
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How often should you follow up on a 2+ epithelial ingrowth?* |
q 1-2d |
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T/F - 2+ epithelial ingrowth involves necrosis. |
False - 3+ involves necrosis |
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T/F - 2+ epithelial ingrowth has no rolled edges, but 3+ has rolled edges. |
False - both 2+ and 3+ involves rolled edges (3+ has corneal melt and 2+ doesn't however) |
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T/F - 3+ epithelial ingrowth is urgent and recurrences are common.* |
True - requires close f/u |
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How do you Tx 3+ epithelial ingrowth? |
Lift the flap, scrape off epith cells, replace flap and place bandage CL; pt on ABs on steroids x1wk |
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T/F - Higher likelihood of over/undercorrections with higher Rx. |
True |
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T/F - over/undercorrections are usually found on the next day.* |
False - no enhancement done less than 8 wks after surgery |
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Glare and halos are common within how long from the surgery? |
Common in first 3 mos |
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What causes glare and halos in post-op? |
Caused by flap healing - fluid in interface ("edema"); vision improves as flap binds to cornea base |
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T/F - Glare and halos can be caused by dry eyes, not only by flap healing. |
True |
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What is normal UCVA at day 1 and beyond day 1?* |
Day 1 = 20/40 or better |
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What is normal BCVA at day 1 and beyond day 1?* |
Day 1 = 20/25 or better |
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How does a normal flap look like at day 1 and beyond day 1?* |
Day 1 = slight staining around edge possible |
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How does a normal epithelial surface look like post-op?* |
Clear and smooth |
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How does a normal interface look like at day 1 and beyond day 1?* |
Day 1 = trace edema, debris possible, no granular WBCs |
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What is the extent of glare and halos post-op?* |
Day 1 to 2 mos = expect night Sx w/ improvement over time |
