Effect of long-term wear of soft contact lenses on corneal transparency in myopes

Objective

To investigate the influence of long-term wear of soft contact lenses on corneal transparency.

Methods

A cross-sectional study was conducted.The corneal optical density of female myopic patients who planned to undergo corneal refractive surgery in Jinan Mingshui Eye Hospital from January 2018 to December 2020 was examined.The patients were divided into ≥2-<5 years group, ≥5-<10 years group, and ≥10 years group according to the duration of wearing contact lenses.Age- and sex-matched patients without wearing soft contact lenses were enrolled as a control group.There were 50 eyes from 50 cases in each group.The cornea was divided into 0-2, 2-6, 6-10, and 10-12 mm corneal vertex-centered annuli.The cornea over each annulus was divided into a superficial layer (≤120 μm from the outer surface of the cornea), a deep layer (≤60 μm from the inner surface of the cornea) and a central layer (between the superficial and deep layers). Measurements of the right eye were taken for analysis.The corneal optical density of different layers over different corneal ring regions was compared.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Jinan Mingshui Eye Hospital (No.2018-005). Written informed consent was obtained from each subject before any medical examination.

Results

The corneal optical density tended to decrease as the wearing duration of corneal contact lens extended.The corneal optical density values of control group, ≥2-<5 years group, ≥5-<10 years group, and ≥10 years group were 18.51±1.79, 18.25±2.10, 18.16±1.89 and 17.83±1.65, respectively, showing no significant difference (F=1.152, P=0.329). There was no significant difference in the corneal optical density of the superficial layer over 0-2, 2-6, and 6-10 mm annuli among the four groups (F=2.077, 2.080, 2.229; all at P>0.05). There was a significant difference in the corneal optical density of the superficial layer over 10-12 mm annulus among the four groups (F=5.016, P=0.002), and the corneal optical density of the superficial layer was greater in ≥5-<10 years group than in ≥2-<5 years, and greater in ≥10 years group than in control group, showing statistically significant differences (both at P<0.05). There were significant differences in the corneal optical density of the central layer over 0-2 and 6-10 mm annuli (F=3.808, 2.813; both at P<0.05), and the corneal optical density of the central layer was lower in ≥10 years group than in control group, showing a statistically significant difference (P<0.05). There were significant differences in the corneal optical density of the deep layer over 0-2, 2-6, 6-10 and 10-12 mm annuli (F=5.485, 5.625, 3.398, 2.775; all at P<0.05). The optical density of the deep layer was lower in ≥5-<10 years than in control and ≥2-<5 years groups over 0-2, 2-6, and 10-12 mm annuli, lower in ≥5-<10 years group than in control group over the 6-10 annulus, and lower in ≥10 years group than in control group over 0-2, 2-6, and 6-10 mm annuli, and the differences were statistically significant (all at P<0.05).

Conclusions

For women, the long-term wear of soft contact lenses for 5 years does not affect corneal transparency, and long-term wear for more than 5 years can cause a decrease in the transparency of the superficial peripheral cornea.

Myopia; Contact lenses, soft; Cornea; Densitometry; Transparency