Quantitative evaluation of corneal epithelial oedema by confocal microscopy

To develop a novel quantitative index for evaluation of corneal epithelial oedema, the pixel intensity of confocal microscopic images was measured derived from the basal cell layer (BCL) of the corneal epithelium in normal eyes, eyes before and after cataract surgery, and eyes affected by bullous keratopathy.

Five eyes of five normal volunteers, 14 eyes of 11 cataract patients and 12 eyes of 12 bullous keratopathy patients were examined by confocal microscopy. The cataract patients underwent cataract surgery, and they were examined by confocal microscopy, corneal pachymetry, and anterior fluorometry both before and at various times after surgery. The pixel intensity of BCL images obtained by confocal microscopy was measured and expressed as the BCL index.

The coefficient of variation for repeated (five times) measurement of the BCL index in each of the five normal eyes was 3.4%. The BCL index was 54.8 5.3 (mean SD) before surgery, increased significantly to 65.2 10.0 on the day after surgery, and gradually decreased thereafter in the cataract patients. The time-course of the BCL index coincided well with that of corneal thickness and anterior fluorometry value. The BCL index in eyes affected by bullous keratopathy was significantly increased at 95.0 6.4.

The BCL index was increased after cataract surgery and in eyes affected by bullous keratopathy, conditions associated with corneal epithelial oedema. This quantitative measure obtained by confocal microscopy may prove useful in the clinical evaluation of corneal epithelial oedema.