Abstract
Purpose: :
The sub–basal nerve fiber layer of the corneal epithelium provides innervation to the corneal epithelial surface. Corneal sensitivity has previously been shown to decline due to contact lens–induced hypoxia. Silicone hydrogel contact lenses reduce the hypoxic effect of contact lens wear on the eye. This study compared the corneal epithelial sub–basal nerve fiber layer of silicone hydrogel contact lens wearers with that of a group of normal, healthy non–contact lens wearing control participants.
Methods: :
The corneal epithelium of 20 asymptomatic silicone hydrogel contact lens wearers was assessed over 2 months using slit lamp biomicroscopy and confocal microscopy. Contact lens wearers were 26 years old on average and had been wearing soft lenses for approximately 7 years. Previous silicone hydrogel lens use averaged 17 months. Confocal microscopy was performed using the ConfoScan3, a scanning slit clinical confocal microscope (Nidek Technologies, Italy). Images of the corneal epithelial sub–basal nerve fiber layer were analyzed and compared to that of 10 healthy, non–contact lens wearing, control participants of average age 25 years.
Results: :
Neural orientation of the corneal epithelial sub–basal nerve fibers was vertical centrally, and became progressively more oblique or horizontal in the mid– peripheral and peripheral corneal regions (p<0.05). Neural density was greatest in the central corneal region and then declined in the mid–peripheral and peripheral cornea (p<0.05). These trends were the same in lens wearers and controls. For both contact lens and non–contact lens wearers, the neural width ranged from 2.8 µm to 3.6 µm.
Conclusions: :
The corneal epithelial sub–basal nerve fiber layer of asymptomatic silicone hydrogel contact lens wearers has neural features similar to those of non– contact lens wearers.
Keywords: contact lens • cornea: epithelium • nerve fiber layer