Clinical Evidence of Decreased Iris Resistance in Patients With Keratoconus

To compare the total energy required for producing patent neodymium:yttrium-aluminum-garnet laser peripheral iridotomy in patients with or without keratoconus (KC).

In this case-control study, 36 eyes from 36 patients with KC and 24 eyes from 24 patients with myopia with or without astigmatism (as control group) who were scheduled for phakic intraocular lens implantation underwent neodymium:yttrium-aluminum-garnet laser peripheral iridotomy 1 week before surgery. The total laser energy was recorded and compared between the 2 groups.

Mean total laser energy was significantly lower in patients with KC compared with the control group (114.7 ± 41.0 mJ and 263.9 ± 79.6 mJ, respectively, P < 0.01). Total laser energy was not correlated with patients' age, sex, race, refraction, maximum keratometry, or corneal thickness.

Lower tissue resistance may be present in other ocular structures, such as iris, in patients with KC. Our findings supported a generalized abnormality in patients with KC rather than a localized corneal disease, at least in some cases.