LAUSR

Dear Editor, We read with great interest the article by López-Miguel et al. comparing specular microscopy with ultrasound pachymetry before and after cataract surgery [1]. We would like to congratulate the authors for their interesting and nice paper, because a precise corneal thickness measurement is very important, for example, in evaluating the intraocular pressure [2] but we would like to make some comments on this article, because in our opinion there are some points that need to be clarified. In a previous paper we found that corneal thickness obtained with Topcon SP-3000P was thinner than the measurements obtained with Pentacam, and we proposed a regression formula to make the measurements comparable [3]. We wonder if one of the reasons for thinner corneas found in López-Miguel’s paper could be related to the fact that SP 3000Pmeasurements are absolutely thinner compared to other devices. Moreover, the authors performed the US pachimetry after the instillation of one drop of topical anesthesia (0.1% tetracaine and 0.4% oxybuprocaine, Alcon, Barcelona, Spain), and stated that this could have been the reason for the thicker central corneal thickness found with US compared to Topcon SP-3000P. They reported that the use of topical anesthesia has been described as causing corneal thickening [4]. This is partially incorrect, because not all the anesthetic drops cause a corneal thickening, in fact, in a previous paper we found no significant changes in cornel thickness utilizing oxybuprocaine eye drops [5]. However in our opinion the differences between the two devices could account for two other reasons: