Objective: Confocal in vivo real-time microscopy was applied to study the corneal morphology in long-term contact lens wearers.
Design: In a cross-sectional study, patients with a history of long-term contact lens wear underwent corneal confocal microscopy. The authors investigated 13 patients with a history of up to 26 years of soft contact lens wear, 11 patients with a history of up to 25 years of rigid gas permeable contact lens wear, and a control group of 29 normal subjects without a history of contact lens wear.
Intervention: Scanning slit-confocal microscopy was performed with a 50x/1.0 NA water immersion objective. Corneal optical sections were recorded in real time without further digital processing and reviewed frame by frame.
Main outcome measures: Video frames selected from all corneal layers were evaluated qualitatively. The new finding of panstromal microdot deposits was quantitated in a scoring system ranging from 0 to 4+. Corneal endothelial cell densities were counted with the fixed frame technique.
Results: Epithelial microcystic changes and alterations of endothelial cell morphology were found to a variable extent as described previously. A new finding was there were highly reflective panstromal microdot deposits in the corneal stroma. For this new disease, a scoring system ranging from 0 to 4+ was established. In the control group, 0 of 29 patients had stromal microdot deposits. In the soft contact lens group, 13 of 13 patients had panstromal microdot deposits with a mean score of 3.1 (range, 1-4), and in the hard contact lens group, 11 of 11 had a mean score of 1.9 (range, 1-4) for corneal microdot deposits.
Conclusions: With confocal microscopy, a new type of chronic stromal change has been observed in all subjects with long-term contact lens wear. Because subjects with soft contact lens wear had a more pronounced corneal degeneration than did subjects with gas permeable lenses, the authors assume the deposits to be induced by chronic hypoxia. The condition of stromal microdot degeneration as observed with confocal microscopy may be the early stage of a significant corneal disease, which eventually may affect large numbers of patients after decades of contact lens wear.