Characterization of Corneoscleral Geometry Using Fourier Transform Profilometry in the Healthy Eye

Abstract

Objective: To characterize peculiarities of the corneoscleral geometry in healthy eyes. Methods: This is a prospective case series including 88 healthy eyes of 88 patients with an age ranging from 21 to 73 years. A complete ocular examination was performed with emphasis on the analysis of the corneoscleral topographic profile with the Fourier transform profilometer Eye Surface Profiler (Eaglet-Eye BV, Houten, the Netherlands). The distribution of different topographic parameters was evaluated, as well as the correlations between corneal and scleroconjunctival parameters. Results: Mean values of 8.64±0.37 (range, 7.81–9.50 mm), 6.06±0.52 (4.88–7.63 mm) and 11.93±1.32 mm (8.17–15.89 mm) were obtained for inner, limbal, and outer best-fit sphere, respectively. Mean values of 8.54±0.38 (7.86–9.66 mm) and 13.35±1.29 mm (11.05–17.31 mm) were obtained for mean corneal and scleral radius, respectively. Regarding tangent angles at limbus, mean values of 35.31±6.55°, 38.76±5.90°, 32.75±7.04°, and 25.91±8.99° were obtained for nasal, temporal, superior, and inferior angles, respectively. Mean difference between temporal and nasal sagittal heights increased from −1.48±120.70 μm for a chord of 11 mm to 73.53±236.55 μm for a chord of 14 mm. A weak but statistically significant correlation was found between corneal and scleral radii (r=0.325, P=0.004). The maximum sagittal height for a diameter of 12 mm was significantly correlated with flattest keratometry, astigmatism, corneal diameter, and corneal eccentricity (R2: 0.77, P<0.001). Conclusions: The scleroconjunctival surface in the healthy eye presents some level of nasotemporal asymmetry that is higher with increasing diameters of analysis.