Visual, Topographic and Aberrometric Outcomes After Phototherapeutic Keratectomy (PTK) for Salzmann Nodular Degeneration

Purpose: The aim of this paper is to study the visual outcomes, changes in higher order aberration (HOA) and corneal densitometry after debridement and excimer laser phototherapeutic keratectomy (PTK) for the treatment of Salzmann nodular degeneration (SND). Methods: This monocentric study includes 69 eyes from 54 patients who underwent debridement and PTK for SND (mean follow-up time of 447.1 ± 597.7 days post-operatively). The following parameters were measured before and after PTK: best corrected visual acuity (BCVA) in logMAR, sphere, cylinder, calculated spherical equivalent (SPHQ), mean and maximum refractive power, astigmatism, HOA, corneal density and thickness. Patients were divided into two cohorts depending on additional visual acuity limitations (VAL). Results: Mean visual acuity improvement was 0.16 ± 0.21 logMAR (p < 0.001), independent of additional VAL, and was associated with normalization of the cornea (hyperopic reduction by 2.13 ± 2.60 dpt, p < 0.001), reductions in cylinder (1.49 ± 2.44 dpt, p < 0.001) and corneal astigmatism (3.01 ± 3.39 dpt, p < 0.001). HOA was reduced by 0.77 ± 1.11 µm (p < 0.001) and corneal density by 6.08 ± 16.45 gray scale units (GSUs) in the center (p = 0.019) and by 9.32 ± 12.08 GSUs in the mid-periphery (p < 0.001). Haze occurred in 26.1% of patients (15.9% mild; 10.1% moderate). Re-PTK was necessary in 5.8%. Conclusions: PTK is a low-complication method for visual improvement in patients with SND, regardless of additional VAL, and is associated with a normalization of corneal parameters. HOA, corneal density and K_max were reduced significantly and showed a correlation with visual acuity, implying that these objective parameters may have a good predictive value for visual acuity.