Angle Kappa Measurements: Normal Values in Healthy Iranian Population Obtained With the Orbscan II

BACKGROUND: The angle kappa is important in proper centration of corneal ablation in keratorefractive surgery. Orbscan II device is widely used preoperatively in photoablation surgeries and can be used to measure the angle kappa. OBJECTIVES: This study aimed to determine the mean angle kappa and its intercepts in healthy young Iranian adults. PATIENTS AND METHODS: In this cross-sectional study, orthotropic patients (age range, 18-35 years) who were referred to the Khatam Eye Hospital (Mashhad, Iran) were included. Exclusion criteria were as follows: history of any eye deviation or strabismus with or without orthoptic or surgical treatment; any intraocular, corneal, or keratorefractive surgery; contact lens use; any corneal anomaly; any ophthalmic or systemic drug consumption; and hyperopic spherical refraction > + 3.00 diopters (D), spherical refraction > -5.00 D, or cylindrical refraction > 2.00 D. All of the parameters were measured by the same operator through an Orbscan II device. RESULTS: A total of 977 healthy participants who aged 18 to 45 years were included consecutively. The study population consisted of 614 females and 363 males. The average angle kappa was 5.00º ± 1.36º at 240.21º ± 97.17º in males and 4.97º ± 1.30º at 244.22º ± 94.39º in females (P = 0.63). The average horizontal (x-axis) angle kappa was -0.02º ± 0.49º, with a mean of -0.02º ± 0.50º in males and -0.02º ± 0.49º in females (P = 0.93). The average vertical (y-axis) angle kappa was -0.09º ± 0.32º, with a mean of -0.09º ± 0.33º in males and -0.09º ± 0.32º in females (P = 0.74). CONCLUSIONS: By using the normal angle kappa determined in this study, pseudodeviations can be identified more precisely in those who might undergo keratorefractive surgery.