LAUSR

F irst of all, we would like to thank Dr Yolcu and Dr. Civan for their interest and comments regarding our article on ‘Effect of topical prostaglandin (PG) analogues on corneal hysteresis’ recently published in Acta Ophthalmologica (Bolivar et al. 2015). As they correctly point out in their letter, there has been a great interest in the relationship between corneal viscoelastic parameters [such as central corneal thickness (CCT), corneal hysteresis (CH), etc.] and glaucoma. PG analogues seem to induce a minor change in the CCT, as Yolcu et al. correctly point out (Yolcu & Civan 2015), but it was out of scope of our study to measure the changes in CCT. Our work (Bolivar et al. 2015) was focused just on the change of the CH in newly diagnosed, previously untreated glaucomatous eyes, after topical treatment with PG analogues monotherapy. Nevertheless, the reported PG treatment induced decrease in the CCT is quite small, thus making unlikely that this minimal change, by itself, can modify the corneal response to a stress (compression by a jet of air or applanation by the Goldmann tip) (Maruyama et al. 2014). Furthermore, a change in the CCT must be induced by a change either in the stroma, in the epithelium or in both structures. In fact, Rosa et al. (2014) suggested that if it is found that PG analogue treatment does change the CH, this fact would suggest that it is not the epithelium, but the stroma, the part of the cornea affected by these drugs. In fact, our finding that CH does change in this scenario, strongly supports their hypothesis. Furthermore, the anecdotal report of a case of rapid progression of a previously stable keratoconus induced by topical treatment with latanoprost (Amano et al. 2008) further suggests that PG analogues, probably due to the upregulation of stromal metalloproteinases induced by them, do affect the stromal viscoelastic properties, at least to some extent. We completely agree with Yolcu et al. that more studies are needed to fully understand the effects of PG analogues and glaucomatous disease on the cornea.