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Related Experiment Video

Updated: May 12, 2026

Correction of Presbyopia by Monocular Bi-Aspheric Ablation Profile

Published on: September 20, 2024

Angle kappa changes after photorefractive keratectomy for myopia.

Siamak Zarei-Ghanavati¹, Hamid Gharaee, Alireza Eslampour

¹Eye Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.

International Ophthalmology

|April 10, 2013

Summary

Photorefractive keratectomy (PRK) for myopia does not significantly alter the angle kappa or its corneal intercepts. This suggests PRK surgery does not change corneal vertex locations after treatment for myopia.

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Published on: September 16, 2025

Area of Science:

Ophthalmology
Corneal Surgery
Optometry

Background:

Angle kappa, the misalignment between the visual and pupillary axes, is a crucial parameter in refractive surgery.
Understanding its stability after corneal procedures like photorefractive keratectomy (PRK) is essential for predicting visual outcomes.

Purpose of the Study:

To investigate the changes in angle kappa and its corneal intercepts following wavefront-guided PRK for myopia.
To determine if PRK influences the relationship between the visual and pupillary axes on the corneal surface.

Main Methods:

A prospective study evaluated 48 myopic patients (96 eyes) undergoing aspheric wavefront-guided PRK.
Angle kappa and its intercepts were measured preoperatively and at 1 and 6 months postoperatively using Orbscan IIz.
Manifest refraction and visual acuity were also assessed.

Main Results:

No statistically significant differences were found in the mean angle kappa values before and after PRK (6 months: 4.97° ± 1.24° vs. 4.99° ± 1.10°).
Horizontal (x-intercept) and vertical (y-intercept) corneal intercepts of angle kappa also showed no significant changes post-PRK.
Average horizontal intercepts were -0.562 ± 0.074 mm preoperatively and -0.554 ± 0.055 mm at 6 months postoperatively.

Conclusions:

Photorefractive keratectomy (PRK) does not induce significant changes in angle kappa or its corneal intercepts.
The findings suggest that PRK preserves the corneal vertex locations relative to the visual and pupillary axes.