Comparison of endothelial cell density estimated by contact and non-contact specular microscopy

Purpose: To compare a contact and a non-contact specular microscope in the determination of endothelial cell density. Subjects and methods: One hundred and twenty-one eyes from 70 patients who had undergone various degrees of photorefractive keratectomy for myopia wer e included. The endothelium was imaged by contact (Konan Clinical Specular Microscope) and non-contact (Topcon SP-1000) specular microscopy and the en dothelial cell density estimated. Results: The average endothelial cell density achieved by the contact specu lar microscope was 3011+/-298 cells/mm(2) (mean+/-SD, n=121) and by the non -contact specular microscope 3015+/-265 cells/mm(2) (n=121), The difference in endothelial cell density between the contact and the non-contact specul ar microscope (contact minus non-contact) was -4+/-175 cells/mm(2) (t=0.26, 2p>0.05 in a paired t-test), The sampling error on the estimated endotheli al cell density was 76 cells/mm(2) for the contact specular microscope and 74 cells/mm(2) for the noncontact specular microscope, \Conclusion: The average endothelial cell density and the precision of the measuring technique mere similar for the contact and the non-contact specul ar microscope. Furthermore, the endothelial cell densities estimated by the two instruments at various values of anterior central corneal refractive p ower and central corneal thickness were similar, The two instruments can be used interchangeably.