IMPACT OF SUPERFICIAL KERATECTOMY ON CORNEAL TOPOGRAPHY, ABERRATION AND DENSITOMETRY IN SALZMAN NODULAR DEGENERATION.

To describe changes in corneal topography, wavefront analysis and densitometry changes after superficial keratectomy for Salzman nodular degeneration.

Salzmann’s nodular degeneration (SND) is a degenerative corneal pathology wherein hypertrophic nodules on the corneal epithelium can induce both visual and mechanical disturbances. Superficial keratectomy (SK) removes these nodules by debriding the corneal epithelium while preserving the Bowman’s layer, resulting in improved visual acuity, reduced pain and a smoother corneal surface.

This retrospective observational study at a tertiary care eye hospital examined patients who underwent superficial keratectomy (SK) for Salzmann Nodular Degeneration (SND) over five years. Eligible patients had pre- and post-operative corneal topography scans approximately three months post-surgery (Pentacam®, OCULUS, Inc). Data collected included visual acuity, refraction, keratometry (K) from the 4-map analysis, the Holladay EKR report, Zernike wavefront aberrations, and corneal optical densitometry (COD). Follow-up measurements were conducted at 3 months post-surgery to monitor changes in these values. Paired T-tests were used to evaluate statistical significance (P < 0.05).

A total of 21 eyes of 17 patients were included. There was an overall decrease in waverfront aberrations (WFA) across bothlower and higher order aberrations, but only changes in Constant term, Height (WFA back (P = 0.058), WFA cornea (P = 0.054), Tilt in X (WFA front (P = 0.011), WFA cornea (P = 0.012)), Astigmatism 45° (WFA front (P = 0.035), WFA cornea (P=0.032)), Koma 0° (WFA front (P = 0.017), WFA cornea (P = 0.016), Astigmatism 4th order 0° (WFA back (P = 0.021) and Koma 5th order 90° (WFA front (P = 0.052) were statistically significant. Mean central flat K significantly increased from 40.14D to 41.55D (P = 0.03) pre- to post- operation, while there was no statistically significant change in steep K (pre-op 43.62D to post-op 43.74D, P = 0.79) and average central K (39.88D to 42.65D, P = 0.201). Similarly, there was a statistically significant increase in flat K values in zones 4.5mm (40.17D to 41.07D, P = 0.037), 5 (40.23D to 41.2D, P = 0.013), 6 (40.57D to 41.6D, P = 0.0039) and 7mm (40.89D to 41.83D, P = 0.01) on the Holladay EKR report, while there was no difference in steep K and average K values across all zones. There was an overall reduction in corneal optical densitometry values across all zones; however only 2-6mm depth, in centre layer zones (pre-op mean 15.21µm, post-op mean 13.49µm, P = 0.054), total zones (18.76µm to 15.73µm, P = 0.042) and in overall total depth, in posterior (15.31µm to 13.22µm, P = 0.053) and total (24.85µm to 20.94 µm, P = 0.035).

There is an increase in flat keratometry, overall reduction in corneal aberrations and corneal optical densitometry values signifying an objective improvement in visual quality and corneal transparency after superficial keratectomy.