Geometrical characterization of the corneo-scleral transition in normal patients with Fourier domain optical coherence tomography.

Purpose: To characterize the geometry at the corneo-scleral transition for a normal population and its correlation with other anatomic parameters of the eyeball.

Methods: Transversal epidemiologic study on a sample of 100 individuals (right eye) in different ethnic groups (Africans and Caucasians). All of them were examined with Fourier domain optical coherence tomography, auto-refractometer, topographer, and biometer to obtain the corneo-scleral angle (CSA) and additional clinical parameters. The dataset was analyzed to determine correlations between different anatomical parameters and nasal (CSAn) and temporal CSA (CSAt) values.

Results: The CSAt presents a significant but low correlation with the anterior chamber depth-ACD (r = 0.25; p = 0.024), the white-to-white (W-W) distance (r = 0.27; p = 0.022), and the anterior chamber volume (r = 0.25; p = 0.016). CSAn did not correlate significantly with any clinical variable, with all values being lower than 179° (concave). Ethic groups presented significant differences for pachymetry (Pac) and corneal volume (p = 0.033 and p = 0.014), being greater for Caucasians, and temporal corneo-iridial angle (p = 0.006), being greater for Africans. CSA presented and inverse correlation with age.

Conclusions: The CSAn presents a more concave profile for the normal population, whereas the CSAt presents a planar-convex profile with a great influence of age. In particular, the older the patient, the more convex the CSAt is. This age-related evolution of the CSAt and the concavity on the nasal direction must be considered when prescribing scleral contact lenses or when performing limbal incisions during refractive interventions.