Confocal microscopic observations of the human cornea following overnight contact lens wear

摘要

Background: Striae and folds are observed with a slitlamp biomicroscope in the corneaudfollowing overnight contact lens wear. These phenomena are poorly understood. Theudaim of this study is to employ confocal microscopy to observe and document these andudother morphological changes in the human cornea following overnight contact lensudwear.udMethods: Slitlamp biomicroscopy, slit-scanning confocal microscopy and ultrasonicudpachometry were performed on both eyes of 13 subjects (3M, 10F, age 24 ± 3 years)udbefore and after eight hours overnight wear of a -3.00 D Bausch & Lomb one dayuddisposable soft contact lens (Dk/t = 15.1 x 10-9 {cm/sec} x {ml O2/ml x mmHg}) in oneudeye; the other non-lens-wearing eye acted as a control.udResults: Following sleep, both corneas were swollen (lens-wearing eye 11.8 ± 3.8 perudcent; control eye 2.1 ± 1.9 per cent) and the stroma of both corneas displayed an apparentudreduction in keratocyte density (lens-wearing eye 21 per cent; control eye 10 perudcent). Folds were observed with the slitlamp biomicroscope and long, straight, dark,udorthogonal lines were observed with the confocal microscope, in the posterior stromaudof the oedematous lens-wearing eyes. Such features were not observed in the controludeyes. The keratocytes appeared less distinct with greater levels of corneal oedema.udConclusion: The apparent loss of keratocytes following overnight lens wear is an opticaludartefact that can be explained in terms of corneal oedema causing volumetric tissueudexpansion and a loss of optical clarity, which hampers keratocyte detection. These findings place the onus on researchers postulating a loss of stromal keratocytes following clinical interventions, such as contact lens wear, to account for the effects of oedema.