Orthokeratology study with a null-screen portable topographer (TOCO)

Abstract

Purpose : The aim of this study is to analyze the results of orthokeratology applied to two ametropic eyes of informed subjects using a custom-built null-screen corneal topographer (TOCO). The anterior corneal surface as well as its overall topography is evaluated before and after the change induced by orthokeratology.

Methods : A portable corneal topographer (TOCO) using a cylindrical null-screen is used to determine the variation of the radius of curvature when a rigid contact lens is adapted on ametropic eyes with the orthokeratology technique. In addition, the corneal topographer is used to obtain the topography maps pre- and post- orthokeratology treatment. We compare the results to those of a mechanical finite-element model (Comsol^TM) of the cornea before and after orthokeratology treatment.

Results : The anterior corneal topography is determined by zonal integration of the TOCO signal to obtain the elevation map and corresponding dioptric power. We validate the method for 2 ametropic eyes of one informed subject. The radii of curvature and eccentricity obtained before of the implementation of the orthokeratology technique were for the right eye: CR_1right= 7.71 mm, eccentricity (e)=0.53, and left eye: CR_1left= 7.72 mm, eccentricity (e)=0.60. The same parameters obtained after the orthokeratology technique were, right eye: CR_2righ= 7.86 mm, eccentricity (e)=0.72, left eye: CR_2left = 8.36 mm, eccentricity (e)=0.85.

Conclusions : Orthokeratology techniques applied on two ametropic eyes produce variations in the radius of curvature in the central zone of the anterior corneal surface; also, the variation of the eccentricity of the surface after the treatment is evident. The dioptric power and the elevation maps are shown to complete the test.

We acknowledge the financial support for this project from DGAPA-UNAM (PAPIIT) (IA106823, IT103823,), PAPIME (PE109023), and FESI-PAPCA 2021-2022-43. The principal author is grateful to the company BLEPS VISION.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.