Evaluation of myopic corneal diameter with the Orbscan II Topography System.
BACKGROUND
To assess the myopic corneal diameter with Orbscan II Topography System (Bausch & Lomb, Orbtek Inc., Salt Lake City, UT, USA).


METHODS
Four hundred sixty-two eyes of 231 myopic patients and 129 emmetropic eyes were measured with the Orbscan II system. Eyes were divided into four groups according to the spherical equivalent(SE) as follows: group 1 [emmetropic group, spherical equivalents between -0.50 D and +0.50 D (-0.50<SE ≤ +0.50)]; group 2 [low myopia group, spherical equivalent between -0.50 D and -3.00D (-3.00<SE ≤ -0.50)]; group 3 [median myopia group, spherical equivalent between -3.00 and -6.00D (-6.00<SE ≤ -3.00)]; and group 4 [high myopia group, spherical equivalents of -6.00D or less (≤-6.00)]. Manifest refraction results and the Orbscan II corneal topographic maps were reviewed retrospectively. Horizontal corneal diameters (white-to-white [WTW] distance) were measured with the Orbscan II system. Subjects in different groups were matched to be comparable in terms of spherical equivalents.


RESULTS
The corneal diameter in all myopic eyes was 11.49 ± 0.36 mm. There were no significant differences between right and left eyes in the t-test for paired samples (t = -0.119, P = 0.906). Differences among four groups proved to be significant in the ANOVA (F = 4.487, P = 0.004).


CONCLUSIONS
This article provides a detailed description and analysis of Orbscan II corneal diameter of a normal myopic population. High degree of mirror image symmetry existed in myopic corneal diameter. Spherical equivalents made a difference in corneal diameter.
The Second Affiliated Hospital of Wenzhou Medical College, 109 Xueyuan Road, Wenzhou, Zhejiang, China. zha_yi@hotmail.com
Yi
Y
Zha
Wangqiang
W
Feng
Xiaohui
X
Han
Jianqiu
J
Cai
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D002648:Child; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D058453:Emmetropia / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009216:Myopia / Q000175:diagnosis*; D009929:Organ Size; D012029:Refraction, Ocular / Q000502:physiology; D012189:Retrospective Studies; D017678:Sex Distribution; D055815:Young Adult