Corneal Wavefront-Guided T-PRK Offers Advantage for Patients With High-Order Aberrations

In eyes with preoperative ablations larger than 0.35 µm, corneal wavefront-guided (CWFG) transepithelial photorefractive keratectomy (T-PRK) can leave patients with superior visual and refractive outcomes, and fewer high-order aberrations (HOAs) than the procedure’s wavefront-optimized (WFO) approach, according to a study published in the Journal of Cataract & Refractive Surgery.

T-PRK is a trending alternative to conventional PRK. While corneal topography-guided surgeries can improve pre-existing HOAs, little research has explored HOAs greater than 0.35 μm. In this study, researchers compared the WFO T-PRK approach with the CWFG T-PRK and reviewed the contrast sensitivity outcomes for patients with these large preoperative HOAs.

The prospective, controlled design included 71 individuals with myopia and myopia including astigmatism. Patients were randomly assigned to receive either WFO (36 eyes) or CWFG (35 eyes) T-PRK. Surgeries took place between July 2019 and October 2020, and follow-ups were conducted after 1 day, 3 days, 1 week, 1 month, 3 months, and 6 months. Participants’ ages ranged from 18 to 33 years. All participants had 1-year refractive stability, myopia (<-10.0 D), and astigmatism (<-6.0 D). Postoperatively, patients received soft bandage contact lenses, topical prescriptions, and instructed to take oral vitamin C, and wear UV-protective glasses.

CWFG provided good visual quality, as this group “had significantly better improvement in contrast sensitivity compared with the WFO group at spatial frequencies of 3, 6, 12, and 18 cpd at 6 months postoperatively (P =.005, P =.007, P =.001, and P <.001, respectively).”

At 6 months after the procedure, no large differences resulted at 6 mm pupil size for corneal or total ocular spherical aberrations (SA) or trefoil, but the CWFG cohort had significantly less total corneal HOAs than WFO participants (P =.006), as well as total ocular HOAs (P =.026). Corneal coma values were also better for individuals receiving CWFG, compared with the WFO group (P <.001), along with total ocular coma (P =.001).

Although more tissue was removed with CWFG, postoperative SA and refraction were comparable between cohorts. No important differences resulted for uncorrected distance visual acuity (UDVA), but significantly different outcomes were noted for corrected distance visual acuity (CDVA) — at 6 months, the WFO group averaged -0.05±0.04 logMAR, compared with individuals who received CWFG, -0.07±0.05 logMAR (P =.039). Also, no haze or other adverse events occurred in either group.

Prior studies have shown coma is associated with starburst and double vision, as well as reported a correlation between aberrations and larger pupil in low light. Postoperative HOAs may reduce scotopic contrast sensitivity as light enters at the transition zone outside the ablation-treated area. Notably, research involving participants with small HOAs reveal only slight dissimilarities between techniques. “Therefore the surgical method might be selected in terms of the size of HOAs,” the analysis explains, adding that for individuals with large aberrations, CWFG is indicated.

“We can conclude that the CWFG profile has advantages in the correction of coma and HOAs,” according to the researchers.

The study design did not include questionnaire data reflecting vision quality in daily life, or explore instances where corneal aberrations exceeded total ocular aberrations, representing potential limitations. 

Reference

Shao T, Li H, Zhang J, et al. Comparison of wavefront-optimized and corneal wavefront-guided transepithelial photorefractive keratectomy for high-order aberrations (>0.35 μm) in myopia. J Cataract Refract Surg. Published online July 15, 2022. doi:10.1097/j.jcrs.0000000000001012