Visual acuity outcomes in eyes with flat corneas after PRK

Area of Science:

• Ophthalmology
• Refractive Surgery
• Corneal Biomechanics

Background:

• Photorefractive keratectomy (PRK) is a common refractive surgery procedure.
• Corneal curvature is a critical factor influencing visual outcomes after PRK.
• Understanding the impact of postoperative corneal steepness is essential for predicting visual acuity.

Purpose of the Study:

• To investigate the relationship between postoperative corneal curvatures (less than 35 diopters) and visual acuity outcomes following myopic PRK.
• To determine if specific postoperative corneal curvature thresholds predict visual acuity loss.
• To evaluate the impact of flat and steep meridians on corrected distance visual acuity (CDVA) after PRK.

Main Methods:

• Retrospective analysis of 5,410 eyes that underwent PRK between January 2006 and November 2010.
• All PRK procedures were performed using the Allegretto 200Hz excimer laser platform.
• Main outcome measures included postoperative CDVA and CDVA loss, analyzed in relation to postoperative corneal curvature (flat and steep meridians).

Main Results:

• Eyes with postoperative flat or steep meridians less than 35 diopters (D) showed worse CDVA compared to those with meridians of 35 D or more (P ≤ .021).
• However, eyes with flatter preoperative curvatures also had worse preoperative CDVA (P ≤ .024).
• Postoperative corneal curvature (flat or steep meridian) did not significantly impact CDVA loss (P ≥ .074).

Conclusions:

• Postoperative corneal keratometry values, specifically flat and steep meridians below 35 D, do not predict the risk of visual acuity loss after myopic PRK.
• The Allegretto 200Hz excimer laser platform's outcomes are not negatively influenced by these flatter postoperative curvatures in terms of visual acuity loss.
• These findings suggest that while initial curvature matters, postoperative values below 35 D do not serve as a reliable predictor for visual acuity decline post-PRK.