We read with great interest the recent article by Okka et al.1 In their article, Okka and colleagues concluded that topical 0.005% and 0.01% latrunculin B were effective in reducing intraocular pressure (IOP) in ocular normotensive monkeys without adversely affecting the cornea. We would like to raise a few points that may broaden the discussion.
First, Okka and colleagues previously demonstrated that topical 0.02% latrunculin B was toxic to the monkey’s corneal endothelium, as evidenced by the increase in corneal thickness and permeability.2 In the current study,1 however, the conclusion that lower concentrations (ie, 0.005% and 0.01%) of topical latrunculin B did not adversely affect the cornea was based solely on the results of corneal pachymetry. Since a significant number of corneal endothelial cells needs to be lost before the cornea begins to swell, corneal thickness alone may not be sensitive enough to reveal the actual corneal damage. We believe that more sensitive methods, such as specular microscopy, vital staining (eg, with alizarin red and trypan blue), and scanning electron microscopy, should also be performed before concluding that topical latrunculin B is nontoxic to the corneal endothelium.
Fan H, Rao SK, Zhou YS, Lam DSC. Effect of Latrunculin B on Intraocular Pressure in the Monkey Eye. Arch Ophthalmol. 2005;123(10):1456-1457. doi:10.1001/archopht.123.10.1456-b