Screening for keratoconus suspects among candidates for refractive surgery

Abstract

This review examines methods for estimating the risk of post‐surgical ectasia in candidates for refractive surgery by establishing a diagnosis of keratoconus suspect as a contraindication for proceeding with surgery. Notwithstanding the desirability of achieving 100 per cent sensitivity, any associated reduction in specificity and increased numbers of false positives might deny some candidates the opportunity to proceed with refractive surgery. The introduction of a model for the risk of ectasia involving both pre‐ and post‐surgical findings has been followed by a plethora of attempts to achieve the same purpose based on topographic and/or tomographic evaluation before surgery. The desirability of being able to depend on objective assessment using one type of instrument needs to be weighed against the possibility that subjective assessments may contribute significantly to screening success. For example, consideration of ethnicity, family history of keratoconus, a history of atopy or ocular allergies in particular, a history of significant exposure to corneal trauma associated with abnormal rubbing habits or with vocational, leisure or geographically increased exposure to ultraviolet radiation or with contact lens wear trauma or a history of significant exposure to activities which elevate intraocular pressure may improve screening success. To the extent that these factors could contribute to increased risk of the development of keratoconus, they may be useful in estimating the risk of post‐surgical ectasia. If any combination of these factors helps to explain the development of keratoconus in normal or even thicker than normal corneas, they may have more significance for those corneas, which have been thinned surgically.

Epigenetic Mechanisms Might Help Explain Environmental Contributions to the Pathogenesis of Keratoconus

“…TGFBI is a cytokine that interacts with the extracellular matrix proteins and plays a role in tissue injury and repair. 27 Sporadic KC cases, by definition, do not have a genetic basis or influence on their disease development. 10 A genetic diagnostic tool is desirable.…”

“…10 A genetic diagnostic tool is desirable. 27 Ideally, family members who do not have or are not at risk for developing KC and who can be used as controls in studies of familial KC could be identified with confidence. 27 Sporadic KC cases, by definition, do not have a genetic basis or influence on their disease development.…”

“…The majority of patients with clinical KC are described as having a sporadic form of the disease, 1,9,10 but this description may need to be modified to less of a majority or even less than a majority by the use of more sensitive and extensive methods of examination, which detect hitherto unidentified KC suspects in KC families. 27 The use of loose terms, such as family members or immediate family members, 28 to describe research procedures might raise questions about the associated findings. 25 Also needed is a clear indication of the scope for family contributions to KC genetics.…”

“…27 Sporadic KC cases, by definition, do not have a genetic basis or influence on their disease development. 27 It is possible that increased susceptibility to environmental mechanisms helps determine KC development. Thorough investigations for the presence of KC in family members do not appear to have been conducted.…”

Evaluation of the risk of corneal ectasia

“…This complication is of serious concern because patients undergo LASIK surgery with practically healthy eyes and have other options for vision correction. The methods used to estimate the risk of post-surgical ectasia have been well documented in the literature [2][3][4]. Despite good ability to predict this complication, current studies continue to report cases of iatrogenic keratectasia [5,6].…”