Evaluating Risk Factors of Post-LASIK Ectasia

Study Overview
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Brief Summary
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Ectasia after refractive surgery is a relatively rare complication which can lead to sight-threatening complications if not detected and treated in time. It is important to continue our quest to improve our methods of identifying absolute and relative risk factors of ectasia following various keratorefractive surgical procedures.

Detailed Description
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Surgical correction of refractive errors is becoming increasingly popular. In the 1990s, the excimer laser revolutionized the field of corneal refractive surgery with PRK and LASIK, refractive lenticule extraction (ReLEx) of intracorneal tissue using only a femtosecond laser, and lately ReLEx smile (SMILE). The term LASIK (Laser in situ keratomileusis) was first used in 1990 by Pallikaris, in which a microkeratome was used to cut a hinged corneal flap, followed by excimer ablation of the stromal bed and flap repositioning . LASIK is known to be a safe refractive surgical procedure, with good refractive efficacy and predictability and is associated with rapid visual recovery with minimal risk of complications. Most of complications are flap related and include a free cap, a button hole, an incomplete cut, flap striae, interface debris, diffuse lamellar keratitis (DLK), and epithelial ingrowth. Other complications include undercorrection, overcorrection, decentered ablation, irregular ablation, and ectasia. Corneal ectasia is a sight-threatening complication of laser refractive surgery characterized by progressive steepening and thinning of the cornea.It is defined as progressive stromal thinning and steepening of the cornea, resulting in refractive aberrations and visual deterioration. The incidence of post- LASIK ectasia is estimated to be between 0.04% and 0.6%.Corneal ectasia has been observed to occur as early as 1 week and as late as several years after LASIK. The main purpose of assessing risk is to determine what group or groups of people present a higher chance to develop post-LASIK ectasia. The development of postoperative ectasia varies between LASIK centers and depends on the screening tools used to screen candidates, the experience and technical skill of the surgeon, and the tools used during the surgery. Risk factors for the development of post-LASIK ectasia include young age, a personal or family history of keratoconus, forme fruste keratoconus (FFKC), high myopia, low-residual stromal bed (RSB), and deep primary keratotomy resulting in a thick flap. Although several risk factors have been identified for the likelihood of ectasia development after keratorefractive surgeries, some cases have been reported to develop in an enigmatic way, without the prescence of any of these risk factors.

Official Title
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Risk Assessment for Corneal Ectasia Following Laser in Situ Keratomileusis

Conditions
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Corneal Ectasia

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: All subjects presented with ectasia following LASIK Exclusion Criteria: Any associated ocular pathology. Any previous ocular surgeries other than LASIK. Corneal opacities. Ocular trauma.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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All

Study Plan
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How is the study designed?
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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Post-LASIK Ectasia | Evaluating back elevation of cornea (in numbers) , corneal curvature (in diopters) , and curvature map (in diopters) using Pentacam oculizer | 5 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Absolute and relative risk factors of ectasia and their cut-off values. | Degree of refraction error (in diopters) using Autorefractometer , corneal pachymetry (in micrometers) , residual stromal bed (in micrometers) , flap thickness (in micrometers) , ablation depth (in micrometers) using Pentacam oculizer , and time between LASIK and diagnosis of ectasia (in days) | 5 minutes |