Central versus thinnest pachymetry of the cornea and thinnest point vector length: impact of ocular side, refractive state, age, and sex

PURPOSE: To quantify the difference in corneal thickness between the central and thinnest point (ΔCCT-TPCT) and the distance between the center of the cornea and its thinnest point (TPCT vector length) and to explore the impact of ocular side, refractive state, age, and sex.

METHODS: Multicenter, retrospective, cross-sectional study. Medical records of 8054 eyes of 4027 refractive surgery candidates were reviewed. The correlation between ΔCCT-TPCT and TPCT vector length (Pentacam) and the variables refractive state, age, and sex were assessed. Spearman correlations, t tests, analysis of variance, analysis of covariance, and multiple regression models were used.

RESULTS: ΔCCT-TPCT was higher in the left eyes of myopic (3.03 ± 2.29 µm) and hyperopic (4.97 ± 3.19 µm) subjects compared with myopic (2.39 ± 2.28 µm) and hyperopic (4.77 ± 3.97 µm; P < 0.05) right eyes. ΔCCT-TPCT was higher in hyperopic than in myopic (P < 0.001) eyes. TPCT vector length was 0.62 ± 0.28 mm for the right eye and 0.69 ± 0.24 mm for the left eye (P < 0.001). TPCT vector length tended to increase with advancing age. Age had the strongest independent effect on TPCT vector length in myopic (η = 0.018; P < 0.001) and hyperopic (η = 0.028; P = 0.006) right eyes. No difference was observed between male and female subjects. The correlations between ΔCCT-TPCT and TPCT vector length were strong (r > 0.8; P < 0.001).

CONCLUSIONS: As a result of the significant differences found, normative data on ocular side, refractive state, and age should ideally be incorporated into ΔCCT-TPCT and TPCT vector length reference values.