Study of changes and the correlations of the corneal sensitivity after wearing orthokeratology lens

Objective To investigate the changes of the corneal sensitivity and thickness at 5 different points of the cornea and the relationship between them after wearing orthokeratology lens, and to observe the difference of the changes between the degree of myopia and different lens designs. Methods Seventy-six patients (142 eyes) with mild and moderate myopia aged 8-18 (11.96± 2.68) years were fitted into orthokeratology. The corneal sensitivity values of the 5 points (the center of the pupil and the superior, the inferior, the nasal and the temporal with a distance of 3mm to the pupil center) after wearing orthokeratology for one night and one hour after taking off the lens, wearing orthokeratology for one week, three months and the corneal thickness of the corresponding points after wearing orthokeratology for one week, three months were observed. Results Compared to the initial values (58.91±4.69, 57.81±7.19, 58.13±7.40, 57.22±8.54, 58.31±7.19)mm, the corneal sensitivity values of the 5 points were decreased after wearing orthokeratology for one night and one hour after taking off the lens, wearing orthokeratology for one week, three months. Among which the values of the 5 points (49.98 ± 12.63, 48.07 ± 14.85, 47.40 ± 14.32, 47.89 ± 13.92, 47.19 ± 14.42)mm were the lowest after wearing orthokeratology for one night, and had significant difference when compared to the values (51.46±12.48, 49.03±14.60, 49.94±13.35, 49.91±13.25, 49.76±13.37)mm at the time one hour after taking off the lens. Compared to the initial values (546.52 ± 31.88, 661.77 ± 42.38, 618.82±39.36, 643.10±39.93, 614.99±36.68)um, the corneal thickness of the pupil center was decreased after wearing orthokeratology for one week (539.79±27.87)um and three months (540.70± 23.60)um, while the corneal thickness of the other four points were thickened (670.36±37.53, 627.67± 35.19, 652.41±32.34, 620.10±33.28 and 678.29±32.98, 636.30±24.03, 648.92±25.57, 623.03±26.93)um. With the correlation coefficient r being -0.032, -0.044 and -0.002, P being 0.39, 0.25 and 0.96, the corneal sensitivity and thickness at 5 different points of the cornea had no significant correlation before and after wearing orthokeratology for one week and three months. The changes of the corneal sensitivity and thickness at 5 different points of the cornea had no significant difference between mild myopia and moderate myopia (P >0.05). The changes of the corneal sensitivity and thickness had no significant difference between different lens designs (P >0.05). During following up time, the rate of corneal fluorescein staining was 2.1% (3 eyes), and all occurred within one week after wearing the orthokeratology and were less than Ⅱ level and all improved after using artificial tear eyedrops. No other severe complications were observed. Conclusions Compared to the initial values, the corneal sensitivity values are decreased, the corneal thickness of the pupil center is decreased, while the corneal thickness of the other four points are thickened after wearing orthokeratology for three months. There is no relevance between the corneal sensitivity changes and the corneal thickness changes after wearing orthokeratology for three months. The changes of the corneal sensitivity and thickness have no relevance with the degree of myopia and different lens designs. Key words: Corneal sensitivity; Corneal thickness; Orthokeratology; Myopia