Refractive changes caused by hypoxia after laser in situ keratomileusis surgery

Area of Science:

• Ophthalmology
• Corneal Surgery
• Physiological Optics

Background:

• Laser in situ keratomileusis (LASIK) is a common refractive surgery procedure.
• Understanding potential refractive changes after LASIK is crucial for patient outcomes.
• The effect of environmental factors like hypoxia on post-LASIK refractive stability is not fully understood.

Purpose of the Study:

• To investigate whether ocular surface hypoxia induces refractive changes in individuals who have previously undergone LASIK surgery.
• To compare refractive and corneal changes in LASIK patients versus non-LASIK myopic controls under induced hypoxia.

Main Methods:

• A prospective paired eye clinical trial was conducted.
• Twenty LASIK subjects and 20 myopic non-LASIK controls participated.
• One eye per subject was exposed to hypoxia (nitrogen) for 2 hours, while the contralateral eye served as a control (21% oxygen).
• Keratometry, cycloplegic refraction, and pachymetry were measured before and after exposure.

Main Results:

• LASIK corneas exposed to hypoxia showed a statistically significant myopic shift compared to controls (P < 0.01).
• Corneal thickening increased significantly and symmetrically in both LASIK and control eyes under hypoxia.
• A non-significant trend toward corneal steepening was observed in the LASIK group.

Conclusions:

• Ocular surface hypoxia can induce a myopic shift in patients who have had LASIK surgery.
• Corneal thickening occurs in response to hypoxia in both LASIK and non-LASIK eyes.
• These findings highlight the potential for environmental hypoxia to affect visual outcomes after LASIK.