Corneal Characteristics in Myopic Patients
Sabong Srivannaboon, MD*, Suksri Chotikavanich, MD*
Affiliation : * Department of Ophthalmology, Faculty of Medicine, Siriraj Hospital, Mahidol University
Objectives : To evaluate the characteristics of the cornea in myopic patients.
Materials and Methods : A retrospective study of 420 eyes in 210 patients who visited the Excimer Laser Surgery
Clinic at Siriraj Hospital, Mahidol University from January 1999 to June 2002 was conducted. All cases that
were eligible for myopic refractive surgery were included in the present study. A preoperative ocular examina-
tion was done in a fashionable method, including manifest refraction and Orbscan Topography to evaluate
corneal thickness, corneal curvature and corneal diameter. Statistical analysis was performed to identify the
characteristics of the cornea in the patients.
Results : The mean age of the patients was 31.66 + 7.77 years. (ranging from 16-51). The mean manifest
refraction (spherical equivalent) was -4.9 + 2.29 diopters (ranging from -0.50 to -13.75). The mean corneal
diameter (white to white) was 11.60 mm + 0.37 mm (ranging from 10.8-12.9). The thinnest point of the cornea
varied from 409 to 597 microns (mean = 522.55) and located mostly in the infero-temporal quadrant of the eye
(23.69% in the right and 32.05% in the left). The mean curvature of the corneal was 44.6 + 13.8 diopters
(ranging from 39.05-47.65). The mean corneal astigmatism was 1.34 + 0.71 diopters and 93.96% were with
the rule astigmatism. Positive angle kappa was found in 408 eyes (97%) but all cases were within a 0.5 mm
horizontal and 0.3 mm vertical radius from the pupillary axis.
Conclusion : Characteristics of the cornea in Thai myopic patients were demonstrated in the present study.
Most of the cornea showed with the rule astigmatism with positive angle kappa and the thinnest point located
at the infero-temporal quadrant.
Keywords : Cornea, Myopia, Thickness, Curvature
