With age, the cornea becomes more prolate, but with little change in both anterior and posterior corneal asphericity (Q), according to a study published in Ophthalmic Physiological Optics.
Researchers analyzed the data from 4961 students (eyes, 4961; mean age, 12.38 years; 53.5% boys) to assess anterior and posterior Q changes over a 3-year period. The investigation occurred over 2 phases — phase 1 was conducted in 2015 and phase 2 in 2018. Students attended an interview to provide demographic and medical information and underwent ophthalmic examinations, which included visual acuity assessment, corneal imaging, and ocular biometry. The presence of 1 clinical sign (Fleischer ring, Vogt striae, Munson sign, apical thinning or Rizzuti sign) and 2 or more abnormal topographic characteristics constituted a diagnosis of keratoconus.
According to the report, the mean [SD] anterior and posterior Q values for an 8-mm chord diameter were −0.38 [0.11] (95% CI, −0.39 to −0.38) and−0.32 [0.12] (95% CI, −0.33 to −0.32), respectively, for the first phase of the study. The mean [SD] 3-year changes in anterior and posterior Q values were 0.00 [0.08] (95% CI: 0.00–0.00) and−0.01 [0.06] (95% CI: −0.01 to −0.01), respectively.
Variables associated with anterior Q prolation included advancing age (β , −0.002; 95% CI, −0.003 to −0.001), 3-year increase in mean keratometry (β , −0.04; 95% CI, −0.06 to−0.02), central corneal thickness (β, −0.001; 95% CI, −0.001 to −0.000), lens thickness and anterior chamber depth. Increased axial length was associated with a decrease in Q (β, 0.02; 95% CI, 0.004-0.03).
Female sex (β, −0.004; 95% CI, −0.007 to −0.001) was significantly associated with a more prolate posterior Q value, while rural residence (β, 0.005; 95% CI, 0.002-0.009]) was associated with a more oblate posterior Q.
“In cross-sectional analysis of the first phase results, increasing age was associated with a more oblate corneal shape,” the study authors note. “In addition, the 3-year changes in both anterior and posterior surface Q values were small.”
A short duration of follow-up is a recognized limitation to the research.
Hashemi H, Khabazkhoob M, Jamali A, Emamian MH, Fotouhi A. Three-year change in corneal asphericity in children at the age of emmetropisation. Ophthalmic Physiol Opt. Published online October 2, 2022. doi:10.1111/opo.13056