False corneal ectasia in patients referred for corneal crosslinking, topography-guided photorefractive keratectomy, and intrastromal corneal rings

Objective: To determine the misdiagnosis of ectasia in patients referred for corneal crosslinking and possible topography-guided photorefractive keratectomy (PRK) or intrastromal corneal rings. Setting: Bochner Eye Institute, Toronto, Ontario, Canada. Design: Retrospective data review. Methods: Chart review of consecutive cases referred for corneal crosslinking to determine the number of cases of misdiagnosis of ectasia. Examination findings were reviewed consisting of best-corrected spectacle distance acuity, slit lamp examination, and computerized tomography. Results: The study analyzed 1000 consecutive records of patients referred with a presumed diagnosis of keratoconus, pellucid marginal degeneration, and ectasia after laser vision correction that were examined between January 1, 2010 and November 1, 2016. There were 26 eyes without ectasia detected in 20 patients. The etiology of these misdiagnoses was epithelial basement membrane dystrophy (9 eyes), superficial punctate keratitis (7 eyes), amblyopia secondary to high astigmatism (3 eyes), amiodarone keratopathy (2 eyes), corneal warpage from rigid gas permeable lenses (2 eyes), corneal scars (1 eye), and measurement or alignment error with topography (2 eyes). Conclusion: Analysis of data detected a misdiagnosis of ectasia in 20 patients (26 eyes), a finding of 2.0%(20 of 1000) of referred cases that did not satisfy the diagnostic criteria of corneal ectasia. These conditions are considered a contraindication to corneal crosslinking and there is usually no benefit to topography-guided PRK or intrastromal corneal rings. It is important that clinicians recognize the clinical findings of these conditions and differentiate from true keratoconus, pellucid marginal degeneration, or ectasia after laser vision correction.