Thickness changes in the corneal epithelium and Bowman's layer after overnight wear of silicone hydrogel contact lenses

Abstract

Background: To investigate thickness changes in the corneal epithelium and Bowman's layer after overnight silicone hydrogel contact lens (CL) wear by using ultra-high resolution optical coherence tomography (UHROCT).

Methods: Eleven subjects without CL wearing history were recruited for this study. An UHROCT was used to measure the thickness of the epithelium (ET), Bowman's layer (BT), stroma (ST), and total cornea (CCT) at the center of both eyes. A silicone hydrogel CL was inserted in the right eye of each subject, and the fellow non-CL wearing left eye served as the control. The lens was inserted at 9:30 pm and removed at 8:00 am the next morning. The subjects were evaluated at 9:00 pm (baseline), 9:30 pm (lens insertion), 10:00 pm (before sleep), 7:00 am (waking), 7:30 am, and 8:00 am (lens removal).

Results: Compared to the lens insertion level, the ET of the lens-wearing eye increased by 5.73% at eye opening (P = 0.001). The ET of the non-CL wearing eye and the BT in both eyes did not change after overnight CL wear. Compared to baseline, the CCT of the lens-wearing eye increased by 2.87% upon waking (P = 0.003) and recovered 30 min later (P = 0.555). In contrast, compared to baseline, the CCT of the non-CL wearing eye did not increase upon waking (P = 0.105).

Conclusions: By using UHROCT, we found that overnight CL wear induced different swelling responses in the various sublayers of the cornea.

Trial registration: Retrospectively registered. Registration number: ChiCTR1800015115 . Registered 07 March 2018.

Keywords: Bowman’s layer; Contact lens; Epithelium; Overnight; Thickness.

Fig. 1

Optical coherence tomography (OCT) image of one 29-year-old subject and longitudinal reflectivity profile. Left: OCT image of the cornea center at baseline. a: Epithelium; b: Bowman’s layer; c: Stroma. Right: Longitudinal reflectivity profile after removing the strong reflectivity at the center. The distance between peaks a and b was the thickness of the epithelium; the distance between peaks b and c was the thickness of Bowman’s layer; the distance between peaks c and d was the thickness of stroma; and the distance between peaks a and d was the total corneal thickness

Fig. 2

A questionnaire was used to rate ocular comfort. Very poor comfort was defined as 0, and excellent comfort was defined as 50

Fig. 3

Corneal epithelial thickness after overnight contact lens (CL) wear. Compared to the lens insertion level, the epithelial thickness of the lens-wearing eye increased at eye opening (P = 0.001). The epithelial thickness of the non-CL-wearing left eye did not change at waking (P > 0.05).*: P < 0.05, compared with the lens insertion level

Fig. 4

Bowman’s layer thickness after overnight contact lens (CL) wear. The thickness of Bowman’s layer in both eyes did not change significantly after overnight CL wear (P > 0.05)

Fig. 5

Total corneal thickness after overnight contact lens (CL) wear. Compared to baseline, the total corneal thickness of the lens-wearing right eye increased at waking the next day (P = 0.003) and recovered 30 min later (P = 0.555). In contrast, the total corneal thickness of the non-CL wearing left eye did not increase at waking (P = 0.105). *: P < 0.05, compared with baseline

Fig. 6

Stromal thickness after overnight contact lens (CL) wear. Compared to baseline, the stromal thickness of the lens-wearing right eye increased at waking (P = 0.005) and recovered 30 min later (P = 0.383). In contrast, the stromal thickness of the non-CL-wearing left eye did not increase at waking (P = 0.467). *: P < 0.05, compared with baseline

Fig. 7

Ocular comfort ratings after overnight contact lens (CL) wear. Ocular comfort decreased after lens insertion (P = 0.007) and remained low during CL wear. *: P < 0.05, compared with baseline