Angle κ Measurement and Its Correlation with Other Ocular Parameters in Normal Population by a New Imaging Modality.

Significance: This study obtained normative database for angle κ using Orbscan 3. The average angle κ values were 2.3 ± 1.34° in the whole sample, 2.23 ± 1.36° in myopic eyes, and 3.3 ±1.5° in hyperopic eyes. This is very important to optimize refractive surgery outcomes.

Purpose: The aim of this cross-sectional study was to obtain the value of mean angle κ in normal eyes of patients seeking laser vision correction, by the Orbscan 3.

Methods: The study was conducted on healthy eyes of people seeking laser refractive surgery. A total of 1815 eyes of 908 candidates were included. These were examined as a part of pre-operative assessment. Orbscan 3 was used to measure angle κ and its XY intercepts, keratometry readings, central corneal thickness, thinnest location, white-to-white diameter, and corneal asphericity of front surface (Qf) and back surface (Qb).

Results: The mean ± standard deviation angle κ in all eyes was 2.3 ± 1.34°. The values were 2.23 ± 1.36° in myopic eyes, 3.3 ±1.5° in hyperopic eyes, and 2.9 ±1.6° in emmetropic eyes. Positive correlation was found between angle κ and age, spherical equivalent, subjective sphere, and white-to-white diameter. On the other hand, axial length, average keratometry, central corneal thickness, pupil diameter, and asphericity Q front were negatively correlated with angle κ.

Conclusions: The mean ± standard deviation angle κ value measured by the Orbscan 3 was 2.3 ± 1.34°. This could be attributed to different software used, in addition to the relatively high axial length in the studied eyes.