Purpose: The aim of this study was to retrospectively investigate the utility of a proposed grading system based on pterygium end position relative to corneal diameter by evaluating the correlation between preoperative corneal irregularity and postoperative corneal shape recovery period.
Methods: Corneal topographic data of 552 eyes (454 patients) that underwent primary pterygium excision obtained at preoperatively and 12 months postoperatively were used to calculate mean refractive power, astigmatic power, the surface regularity index (SRI), and higher-order irregular astigmatism (HOI). Progress rate (%) was defined as the ratio of the distance between the corneal limbus and the pterygium end position to the corneal diameter. A progress rate of 1/3 or less of the corneal radius was considered mild (G1), that over 1/3 but 2/3 or less was considered moderate (G2), and that over 2/3 was considered severe (G3). The mean refractive power, astigmatic power, SRI, and HOI were compared between the grade. After excision surgery, the period to stabilize to the 12-month postoperative level was defined as the restoration period.
Results: The progress rate ranged from 2% to 56% (mean, 28.3%), consisting G1 in 41 eyes, G2 in 391 eyes, and G3 in 120 eyes. Preoperative mean refractive power, astigmatic power, and HOI significantly increased with the grade (p<0.001), while SRI only increased in G3 eyes (p<0.001). At 12 months postoperatively, no differences between grades were found in the mean refractive power or SRI, but astigmatic power and HOI significantly increased in G3 eyes (p<0.045). The restoration period was within 3 months for G1 eyes, 6 months or longer for SRI, within 3 months for other parameters in G2 eyes, within 6 months for mean refractive power and SRI, and within 3 months for astigmatic power and HOI in G3 eyes.
Conclusions: Although the proposed grading system based on progress rate was a relatively simple method, it well reflected the state of corneal irregularity. The grades were correlated with the restoration periods. It followed that this grading system could be useful in the clinical practice.
Nippon Ganka Gakkai Zasshi (J Jpn Ophthalmol Soc) 122: 586-592, 2018.