Enantiomorphism Of The Human Cornea Based On Corneal Topography 3D Atlas Analysis

Abstract

 

Purpose:

 

To characterize and quantify mirror symmetry (enantiomorphism) between the right and left corneas using an integrated analysis of Orbscan corneal topography 3D Atlases.

 

Methods:

 

This study was conducted on 7752 eyes of 3876 normal consenting subjects, including 1883 females and 1992 males (1 missing information), with no history of ocular disease, ocular surgery, or recent contact lens wear. Orbscan II (Bausch and Lomb, Rochester, New York, USA) corneal topography was performed on all eyes and several topographic parameters were analyzed. A 3D shape atlas was created for all right corneas and another atlas for all left corneas. Using a left-right (naso-temporal) mirror transformation (reflection), left corneas were then numerically swapped into "right corneas" and difference maps were generated to compare right and swapped-left corneal atlases, with corresponding p-value maps (paired two-tailed Student’s t-test).

 

Results:

 

The right and left 3D corneal atlases showed remarkable mirror symmetry. Although statistically significant mainly because of the large sample size, most of the observed differences between the right (OD) and the left corneas transformed into "right corneas" (OSt) ranged below the threshold of clinical significance: Thinnest corneal pachymetry (TCP) (mean±SEM: OD: 585±0.6 µm; OSt: 585±0.6 µm; p = 0.0178), TCP "x" coordinate (OD: 0.29±0.01mm nasal to BFS apex; OSt: 0.33±0.01mm nasal to BFS apex; p < 0.001), TCP "y" coordinate (OD: 0.03±0.01mm below BFS apex; OSt: 0.11±0.01mm below BFS apex; p < 0.001), Mean anterior surface power in the 0-3 mm radius central zone (OD: 43.85±0.02 D; OSt: 43.80±0.02 D; p < 0.001), Mean anterior surface power in the 3-5 mm annular zone (OD: 43.58±0.02 D; OSt: 43.52±0.02 D; p < 0.001), Maximum keratometry (Max K) (OD: 44.38±0.02 D; OSt: 44.31±0.02 D; p < 0.001), Max K meridian (OD: 93.1±0.5°; OSt: 89.5±0.6°; p < 0.001), Keratometric astigmatism (OD: 1.03±0.01 D; OSt: 1.00±0.01 D; p < 0.001).

 

Conclusions:

 

This study showed that the left cornea tends to be a mirror image of the right cornea, as characterized by Orbscan corneal topography 3D Atlases.

 

Keywords: topography • cornea: clinical science • imaging/image analysis: clinical