Post-keratoplasty topography-guided photorefractive keratectomy (TG-PRK) is safe and effective, resulting in significant visual acuity, refractive, and keratometric improvements, according to a study published in Cornea.
Often, the vision of patients undergoing penetrating keratoplasty (PK) is limited by 4 D to 5 D of corneal astigmatism, according to investigators. In fact, postkeratoplasty astigmatism is greater than 5 D in 15% to 30% of patients. Most patients require glasses or contact lenses to correct astigmatism or ametropia, or both. However, when the astigmatism is irregular, standard interventions often don’t adequately correct vision.
Excimer laser photoablation is a potential treatment of both astigmatism and spherical refractive error postkeratoplasty. TG-PRK allows physicians to target the specific corneal irregularity. Previous small studies have found that the procedure is safe and effective. In this large, retrospective interventional study, researchers examined the long-term visual, refractive, and safety outcomes of TG-PRK for managing postkeratoplasty refractive error using a high-speed laser with an enhanced beam profile.
Patients in the study underwent TG-PRK with mitomycin C. The goal of the study was to correct both ametropia and high astigmatism. Patients who underwent postkeratoplasty TG-PRK (1 or more times) for any level of astigmatism, with at least 12 months of postoperative follow-up, were included. Eyes that had another surgical corneal intervention for astigmatism before TG-PRK, eyes that underwent partial laser ablation treatment, treatment on a different laser platform before 2014, eyes in which TG-PRK was combined with corneal collagen cross-linking, eyes that couldn’t be tracked because of pupil abnormalities, and those with advanced pellucid marginal degeneration were excluded.
The procedure was used on 54 eyes of 50 patients who underwent previous corneal transplants. Unaided distance visual acuity (UDVA), best corrected visual acuity (BCDVA), manifest refraction, mean central keratometric value, mean keratometric astigmatism, and postoperative complications were reviewed. Final follow-up was at a mean of approximately 31 months. During the study, 16.7% of eyes underwent more than 1 surface ablation. Mean UDVA improved (from 0.96 ± 0.06 LogMAR preoperatively to 0.46 ± 0.05 LogMAR of resolution at the final follow-up; P <.0001). Mean UDVA improved by 4.4 Snellen lines. Improvement in BCDVA was not significant, according to investigators, although a significant improvement was noted when eyes with preoperative CDVA worse than 20/40 were analyzed separately (P =.005). Mean astigmatism improved (from -4.4 D ± 0.26 D preoperatively to -2.4 ± 0.26 D at the final follow-up, P <.0001), whereas mean SEQ improved (from -2.5 D ± 0.39 D preoperatively to -1.1 D ± 0.25 D, P =.02). In total, 9% at the preoperative visit and 55% at the final visit had less than 2 D of astigmatism, respectively. Keratometric astigmatism decreased (from 5.24 ± 0.36 D preoperatively to 2.98 ± 0.34 D at the final follow-up, P < 0.0001). No eyes developed clinically significant haze, 14.8% developed regression, and 13% had a reduction of 2 or more BCDVA lines.
“In line with previous studies, our study gives strong evidence for the role of TG-PRK in improving refraction, topographic keratometry measurements, and visual acuity,” the study shows.. “An important finding in this study is that most eyes do not require more than 1 TG-PRK treatment.”
Researchers noted a few limitations with their study, including the absence of a control group, the retrospective nature, and missing aberrometry data.
Disclosure: Several study authors declared affiliations with the biotech and pharmaceutical industries. Please see the original reference for a full list of authors’ disclosures.
Bizrah M, Lin DTC, Babili A, et al. Topography-guided photorefractive keratectomy for postkeratoplasty astigmatism: long-term outcomes. Cornea. 2021;40(1):78-87. doi:10.1097/ICO.0000000000002403.