Contrast sensitivity measured by 2 methods after photorefractive keratectomy

Area of Science:

• Ophthalmology
• Refractive Surgery
• Visual Neuroscience

Background:

• Flying-spot excimer laser photorefractive keratectomy (PRK) is a surgical procedure to correct refractive errors.
• Assessing visual function post-PRK, particularly contrast sensitivity, is crucial for understanding patient outcomes.
• Contrast sensitivity, the ability to discern subtle differences in brightness, is a key indicator of visual performance.

Purpose of the Study:

• To evaluate changes in contrast sensitivity following flying-spot excimer laser PRK.
• To compare subjective (Vision Contrast Test System [VCTS] 6500) and objective (visual evoked potential [VEP]) methods for measuring contrast sensitivity post-PRK.
• To investigate the relationship between contrast sensitivity and the degree of myopic correction.

Main Methods:

• Contrast sensitivity was assessed in 26 eyes before and at 3, 6, and 12 months after PRK.
• Measurements were taken using both the VCTS 6500 (subjective) and VEP (objective) methods.
• Contrast threshold and VEP amplitude were analyzed in relation to myopic correction levels.

Main Results:

• Significant changes in contrast threshold and VEP amplitude were observed over the 12-month postoperative period (P <.001).
• A significant decline in contrast sensitivity was noted at 3 months post-PRK, with partial recovery by 6 months.
• Patients with higher myopia (>-6.0 diopters) reported greater impairment in contrast sensitivity and lower VEP amplitudes.

Conclusions:

• PRK leads to a temporary reduction in contrast sensitivity and VEP amplitude, with partial recovery observed.
• A significant portion of patients, especially those with high myopia, experience persistent difficulties with low-contrast vision.
• The findings highlight the importance of considering contrast sensitivity deficits in the long-term visual outcomes of PRK.