Optical coherence tomography-derived corneal thickness asymmetry indices: Clinical reference study of normal eyes

PURPOSE: To determine 3-dimensional corneal pachymetry distribution characteristics in a large pool of healthy normal patients. SETTING: Private practice, Athens, Greece. DESIGN: Prospective case series. METHODS: Spectral-domain anterior segment optical coherence tomography (AS-OCT) was used for measurements of central (CCT) and minimum corneal thickness, thickness asymmetry indices for superonasal-inferotemporal (SN-IT) and superior-inferior (S-I), and focal thinning indices (Min-Med focal thinning, Min-Max thickness range). RESULTS: The study enrolled 561 eyes. The mean values were CCT, 537.17 mu m +/- 30.99 (SD) (range 447.0 to 654.0 mu m); minimum corneal thickness, 529.01 +/- 30.02 mu m (range 435.0 to 644.0 mu m); SN-IT, 26.32 +/- 15.06 mu m (range -23.0 to 97.0 mu m); S-I, 25.34 +/- 15.06 mu m (range -36.0 to 93.0 mu m); Min-Med, -20.70 +/- 5.99 mu m (range -7.0 to -50.0 mu m); Min-Max, -59.79 +/- 16.55 mu m (range -156.0 to -23.0 mu m). There were significant age-related differences; the mean SN-IT was 22.19 +/- 12.40 mu m (range -6.0 to 63.0 mu m) in the younger group and 30.44 +/- 15.07 mu m (range -4.0 to 97.0 mu m) in the older group (P=.002). The mean S-I was 21.47 +/- 12.92 mu m (range -5.0 to 70.0 mu m) and 29.76 +/- 16.27 mu m (range -8.0 to 93.0 mu m), respectively (P=.001). CONCLUSIONS: Corneal-thickness asymmetry distribution in a healthy eye population obtained by Fourier-domain AS-OCT showed increased asymmetry in the older group; the asymmetry was not sex dependent. These findings may provide a benchmark for future comparative studies.