Short-term variation in ocular anterior chamber angle using Scheimpflug photography

Abstract

Purpose: To investigate short-term variation of ocular Anterior Chamber Angle (ACA) within and across the different meridians of young, healthy eyes.Method: Scheimpflug photography (via an Oculus Pentacam) was used to repeatedly measure the anterior segment of the right eyes of three young females, all aged 22 years. For each individual, ten consecutive maps were determined over a short time period and each map contained information for the chamber angles of different meridians across the eye involved, roughly at 70 intervals. Each meridian in an eye was thus measured 10 times in total permitting analysis of short-term variation both within and across the meridians concerned. Parametric and non-parametric statistical methods used to understand short-term variation of ACA included meridional plots of medians andlower and upper quartiles (Q1 and Q3) and various polar plots (of raw observations, of means and 95%confidence regions, and of standard deviations).Results: Over, at least, short periods of time, Scheimpflug photography provided fairly repeatable results for ACA both within and across the meridians of the eyes involved. However, occasionally outliers increased variability for some meridians. While short-term variation within meridians was relatively small assuming exclusion of a limitednumber of outliers, variation across the meridians of specific eyes was greater (probably relating to the usual anatomical structure of eyes with ACA in the inferior quadrants being mostly larger than that for the superior quadrants). Friedman ANOVA confirmed for each of the three eyes concerned thamedian ACA was significantly different across thvarious meridians.Conclusion: Scheimpflug photography allows for comprehensive, non-invasive and rapid measurement of ACA through 3600. Repeatability of measurements appears satisfactory over the short-term, despite potential limitations relating to this photo-graphic method for measuring ACA. The holistic and quantitative approach to ACA used here may be useful also in diabetic, neoplastic or other disease of the anterior segment of the eye. This methodology could provide better understanding of the potential risk for acute or chronic angle-closure glaucoma through more complete evaluation of ACA. The methods also could be usefully applied to measurement of ACA using techniques such as anterior segment optical coherence tomography or ultrasound biomicroscopy. (S Afr Optom 2010 69(1) 35-47)