Q: 
I have a patient whos considering LASIK, but someone she knows experienced post-LASIK ectasia. Now, shes uneasy about proceeding. What risk factors should I discuss with her? Can we minimize the risk of post-LASIK ectasia?
A: Factors that put patients at risk are abnormal corneal topography, very high spectacle correction, a very thin cornea, a very steep cornea and younger age, says Randy J. Epstein, M.D., of Chicago Cornea Consultants, Ltd.1 Each is a risk factor for developing ectasia. Even one of them is cause enough for significant concern.2,3
Some cases have occurred with no apparent predisposing factors.2 One retrospective study analyzed such patients preoperative characteristics and determined a rubric by which to measure patients likelihood to develop ectasia following correction.1 It found that patients who developed ectasia were more likely to have abnormal preoperative topographies, be significantly younger, be more myopic, have thinner corneas prior to surgery and have less residual stromal bed thickness.1 The authors assembled a scoring system based on their findings (see Ectasia Risk Scoring).1,3
Ectasia Risk Scoring1,3 Points/ Parameter 4 3 2 1 0 Risk Category Recommendations Comments
Topography
Abnormal*
Inf. steep./SRA*
ABT*
Normal/SBT*
Residual Stromal Bed
<240m
240m-259m
260m-279m
280-299m
>300m
Age
18-21 yrs.
22-25 yrs.
26-29yrs.
>30 yrs.
Corneal Thickness
<450m
451m-480m
481m-510m
>510m
Manifest Refraction
>-14D
-12D to -14D
-10D to -12D
-8D to -10D
-8D or less
Score
0 to 2
Low
Proceed with LASIK.
3
Moderate
Proceed with caution; consider special informed consent.
Consider refraction stability, astigmatism, between-eye topographic asymmetry and family history.
4+
High
Do NOT perform LASIK.
* Abnormal: forme frust keratoconus, keratoconus, pellucid marginal degeneration.
Inferior steepening: 1D or more in some areas, but an inferior/superior value of less than 1.4.
SRA: skewed radial axis, with or without inferior steepening.
ABT: asymmetric bowtie--asymmetric steepening less than 1D with no skewed axial radius.
SBT: symmetric bowtie.
Other red flags are if the patient has a difference of 1.00D or more between eyes, or if he or she presents with Vogts striae, Munsens sign or steep Ks (above 48), says Paul Karpecki, O.D., of Lexington, Ky.
Measure candidates corneas conservatively, Dr. Epstein says. If patients are carefully screened, its becoming less likely (especially with IntraLase) that they will get ectasia."
"When judging the cornea, adds Dr. Karpecki, remember that for each diopter of correction, about 15m of cornea is removed. You want to keep the cornea thicker than 410m. Less than that is risky.
Patients may present with ectasia weeks to years post-LASIK. Some patients corneas are only thick enough for the original procedure, Dr. Epstein says. A follow-up may be too much. Especially, dont be too aggressive in recommending enhancements in patients with high myopia.
If the patient develops ectasia, he or she has several treatment options: gas-permeable (GP) contact lenses, spectacles, corneal collagen cross-linking with riboflavin, Intacs, and others.3,4
One study found that GP lenses provided functional vision in 80% of those patients who opted for it.4
Another option, for patients with high refractive error: a phakic IOL. Optical quality is generally better, and there is no risk of ectasia or dry eye, Dr. Epstein says.
If a patient is still concerned, discuss other procedures with him or her. To minimize the risk of ectasia in borderline cases, says Dr. Epstein, consider surface ablation instead of LASIK.
1. Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk assessment for ectasia after corneal refractive surgery. Ophthalmology 2008 Jan;115(1):37-50.
2. Klein SR, Epstein RJ, Randleman JB, Stulting RD. Corneal ectasia after laser in situ keratomileusis in patients without preoperative risk factors. Cornea 2006 May;25(4):388-403.
3. Kent C. Update: managing and predicting ectasia. Rev Ophth 2007 Sept;14(9):49-59.
4. Woodward MA, Randleman JB, Russell B, et al. Visual rehabilitation and outcomes for ectasia after corneal refractive surgery. J Cataract Refract Surg 2008 Mar;34(3):383-8.
