Yuta Ueno1, Takahiro Hiraoka2, Maki Miyazaki3, Mutsuko Ito4, Tetsuro Oshika2. 1. Department of Ophthalmology, University of Tsukuba Hospital, Ibaraki, Japan. Electronic address: yu_ueno71@yahoo.co.jp. 2. Department of Ophthalmology, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan. 3. Department of Ophthalmology, University of Tsukuba Hospital, Ibaraki, Japan. 4. Ito Eye Clinic, Ibaraki, Japan.
Abstract
PURPOSE: To analyze the influence of corneal thickness profile on posterior corneal astigmatism (PA). DESIGN: Prospective, observational study. SUBJECTS: We included 418 normal subjects (213 men and 205 women) ranging in age from 6 to 93 years (49.0 ± 23.4 years, mean ± standard deviation) in this study. METHODS: Anterior and posterior corneal topography were evaluated using 3-dimensional anterior segment optical coherence tomography. Pericentral corneal thickness (PCT) in each quadrant (superior, inferior, nasal, and temporal) was measured, and average PCT in the vertical (superior + inferior) and horizontal (nasal + temporal) directions was calculated. Posterior corneal astigmatism was calculated as (1) assumed PA based on the anterior corneal curvature measurement and the keratometric index and (2) actual PA derived from the direct measurement of posterior corneal curvature. MAIN OUTCOME MEASURES: Corneal thickness distribution and the difference between assumed and actual PA. RESULTS: The PCT was significantly greater in the vertical (546.0 ± 31.8 μm) than in the horizontal direction (542.6 ± 31.7 μm) (P < 0.0001), and the difference between them was significantly correlated with subject age (r = 0.518, P < 0.0001). The difference between assumed and actual PA significantly correlated with the discrepancy between vertical and horizontal PCT (r = 0.819, P < 0.0001), as well as subject age (r = 0.533, P < 0.0001). CONCLUSIONS: Corneal thickness is greater in the vertical than in the horizontal direction, making the PA more against-the-rule pattern than calculated on the basis of the anterior corneal curvature measurement only. Such discrepancy is more prominent in older patients.
PURPOSE: To analyze the influence of corneal thickness profile on posterior corneal astigmatism (PA). DESIGN: Prospective, observational study. SUBJECTS: We included 418 normal subjects (213 men and 205 women) ranging in age from 6 to 93 years (49.0 ± 23.4 years, mean ± standard deviation) in this study. METHODS: Anterior and posterior corneal topography were evaluated using 3-dimensional anterior segment optical coherence tomography. Pericentral corneal thickness (PCT) in each quadrant (superior, inferior, nasal, and temporal) was measured, and average PCT in the vertical (superior + inferior) and horizontal (nasal + temporal) directions was calculated. Posterior corneal astigmatism was calculated as (1) assumed PA based on the anterior corneal curvature measurement and the keratometric index and (2) actual PA derived from the direct measurement of posterior corneal curvature. MAIN OUTCOME MEASURES: Corneal thickness distribution and the difference between assumed and actual PA. RESULTS: The PCT was significantly greater in the vertical (546.0 ± 31.8 μm) than in the horizontal direction (542.6 ± 31.7 μm) (P < 0.0001), and the difference between them was significantly correlated with subject age (r = 0.518, P < 0.0001). The difference between assumed and actual PA significantly correlated with the discrepancy between vertical and horizontal PCT (r = 0.819, P < 0.0001), as well as subject age (r = 0.533, P < 0.0001). CONCLUSIONS: Corneal thickness is greater in the vertical than in the horizontal direction, making the PA more against-the-rule pattern than calculated on the basis of the anterior corneal curvature measurement only. Such discrepancy is more prominent in older patients.