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Thesis

Comparison of Sagittal Height Measurement Methods in Scleral Contact Lens Fitting

9 November 2015

Abstract

Purpose: This study compared 3 methods of measuring sagittal height of the eye (Zeiss Visante anterior segment OCT, Eaglet Eye Surface Profiler (ESP), and Medmont E300 Corneal Topographer Estimated Sagittal Height (ESH) software) and evaluated the ability of each to predict central clearance of a scleral contact lens.

Methods: Sagittal height at a chord of 15mm was measured on 52 normal eyes with each of 3 methods. Visante OCT corneal sections were measured with calipers, Eaglet software analyzed ESP corneal sclera maps, and Medmont ESH software utilized composite corneal topography for calculations. A random subset of 30 eyes was selected to wear an ICD 16.5 (Valley Contax) 4400µm lens, and central clearance was measured on Visante OCT scans taken within 5 minutes of lens insertion.

Results: Sagittal height measurements differed by method [F(2,102)=8.12, p<0.001]. Eaglet ESP values were significantly lower than Zeiss OCT and significantly lower than Medmont ESH (p’sp 0.29).

Conclusions: Medmont ESH module sagittal height measurements do not significantly differ from Visante OCT, a highly specialized imaging instrument. Eaglet ESP sagittal height measurements were significantly lower than both Medmont ESH and Visante OCT. As Placido ring topographers are common in clinical practice, the addition of software such as the Medmont ESH may empower more clinicians to make precise measurements to aid the process of scleral lens fitting.


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