[Optical power of the corneal epithelium]

The refracting power of the corneal epithelium is relatively unknown. We measured the keratometric refracting power of the cornea in two series of 10 fresh bank eyes and on five cat eyes with and without epithelium. The readings were performed at the 2 and 3.6 mm optical zones with an automated keratometer and with a videokeratoscope (TMS-1). The mean change was +1.30 D (0.55-1.85 D) at the 2 mm optical zone and 0.85 D (0.2-1.6 D) at the 3.6 mm optical zone in the first series of 10 eyes. The optical power of the epithelium was most significant within the central cornea. By removing the epithelium there was an increase in corneal refracting power and a change in the power and axis of astigmatism. We discuss the consequences of these findings and how they might affect the outcome of photorefractive keratectomy or other similar keratorefractive procedures.