Corneal densitometry after photorefractive keratectomy, laser-assisted in situ keratomileusis, and small-incision lenticule extraction

Abstract

PurposeThe aim of this study was to gain greater insight into the corneal densitometry changes occurring as a result of refractive surgery and to compare these changes across three widely used surgical techniques, namely, photorefractive keratectomy (PRK), laser-assisted in situ keratomileusis with a femtosecond laser (LASIK-FS), or ReLEx small-incision lenticule extraction (ReLEx SMILE).Patients and methodsThree hundred and thirty-six patients (184 male and 152 female patients) participated in this study. They were split into three groups according to the refractive surgery technique they had undergone: LASIK-FS (74 patients), PRK (153 patients), and ReLEx SMILE (109 patients). All participants underwent an exhaustive eye examination both before and after surgery. Pre- and postoperative corneal densitometry was measured using an Oculus Pentacam system.ResultsThe mean postoperative total corneal densitometry values were 16.53±1.94 for the LASIK-FS group, 15.53±1.65 for PRK, and 16.10±1.54 for ReLEx SMILE. When corneal densitometry was analyzed for specific corneal areas, the values corresponding to the 0-2, 2-6, and 6-10 mm annuli were similar across the three surgical techniques. The only region in which differences were found was the peripheral area (P<0.05), but these variations across techniques were not statistically significant.ConclusionsCorneal densitometry can be used as an objective metric to assess corneal response to refractive surgery, and to monitor patients over time. Corneal densitometry was not negatively affected by any of the refractive surgical procedures under evaluation.

Figure 1

Screen data output of the Scheimpflug optical densitometry assessment. The 12-mm-diameter area is subdivided into four concentric radial zones (0–2, 2–6, 6–10, and 10–12 mm). The output is also subdivided based on corneal depth into anterior (anterior 120 μm), central, and posterior (the most posterior 60 lm of the cornea) layers.

Figure 2

Corneal densitometry measurements according to corneal ring zones postoperative values. There were no statistically significant differences between surgical techniques in any radial segment of the cornea (a). Corneal densitometry measurements according to corneal depth postoperative values. There were no statistically significant differences between surgical techniques in any corneal depth (b).

Figure 3

Corneal densitometry dispersion in relation with spherical equivalent and LASIK-FS surgery. Pearson’s correlation coefficient: 0.170 (P<0.001; a). Corneal densitometry dispersion in relation with spherical equivalent and PRK surgery. Pearson’s correlation coefficient: 0.205 (P=0.002; b). Corneal densitometry dispersion in relation with spherical equivalent and ReLEx SMILE surgery. Pearson’s correlation coefficient: 0.258 (P=0.001; c).