Radial keratotomy and glare effects on contrast sensitivity

Area of Science:

• Ophthalmology
• Visual Psychophysics

Background:

• Radial keratotomy (RK) is a surgical procedure to correct myopia.
• Some patients report experiencing 'glare' after RK surgery.

Purpose of the Study:

• To investigate the effects of a glare source on contrast sensitivity in patients who have undergone RK.
• To quantify 'glare loss' and compare it between the operated (RK) eye and the unoperated eye.

Main Methods:

• Contrast sensitivity was measured using gratings (0.7 and 2.9 cycles/deg) and flicker (8, 16, 32 Hz) in 15 unilateral RK patients.
• Contrast thresholds were determined with and without a surrounding glare source.
• 'Glare loss' was calculated as the reduction in contrast sensitivity with the glare source on.

Main Results:

• Both RK and unoperated eyes exhibited glare loss for gratings and flicker.
• Spectacle lenses increased glare loss for both stimulus types.
• RK eyes showed greater flicker glare loss but less grating glare loss compared to unoperated eyes.
• Larger pupil diameter correlated with increased glare loss in RK eyes.

Conclusions:

• Glare affects contrast sensitivity in both RK and unoperated eyes, with variations depending on stimulus type and pupil size.
• Spectacle lenses can worsen glare-related visual disturbances post-RK.
• Current psychophysical glare measurements did not correlate with patient-reported glare or a standard glare tester.