Mean Anisocoria ± Standard Deviation ( Range ) ( mm )

69 ABSTRACT PURPOSE: To report the incidence of anisocoria after unilateral excimer laser photorefractive kera-tectomy (PRK) for myopia and subsequent cortico-steroid therapy in a retrospective and prospective study and to explore possible etiologies. METHODS: The horizontal pupil diameter was determined in 6 patients (6 eyes) at 21.8 ± 12.6 months after unilateral wide-field excimer laser PRK (retrospective group) as well as in 8 consecutive patients (8 eyes) before and 3.4 ± 2.9 months after unilateral PRK (prospective group). The Schwind-Keratom wide-field excimer laser was used. Measurements were done in an examination room using Rosenbaum card comparison pupillometry and with a Goldmann perimeter at 31.5 asb. In the prospective group, the effect of fitting a hard contact lens of zero diopter power and the application of 0.1% pilocarpine were evaluated. RESULTS: Relative mydriasis was present in all treated eyes and the difference in pupil diameter between the two eyes measured 0.25 to 1.75 mm (retrospective group: +0.56 ± 0.82 mm; prospective group: +0.72 ± 0.29 mm). At the time of pupil measurement , the retrospective group had a significantly longer mean postoperative follow-up (21 mo) than the prospective group (3.4 mo) and significantly more eyes still received topical corticos-teroid treatment (retrospective group, 1 of 6 eyes; prospective group, 7 of 8 eyes). The amount of anisocoria did not correlate with the applied laser energy, ablation depth, or refractive change, but showed a negative correlation with increasing time after PRK. Neither hard contact lens fitting nor pilocarpine 0.1% reduced the amount of anisocoria significantly. CONCLUSION: Unilateral PRK with wide-field excimer laser ablation and subsequent application of topical corticosteroids regularly resulted in a relative pupillary mydriasis. Neither an altered corneal profile nor parasympathetic denervation is responsible for this. Weakening of the pupillary sphincter of the treated eye may cause this phenomenon. P hotorefractive keratectomy (PRK) has gained widespread acceptance for the correction of myopia. The procedure is considered to be reliable and safe with no evidence of potential risk to intraocular structures. Known complications such as corneal scarring and irregularities of the ablation are all limited to the cornea. 1,2 We occasionally observed a relative mydriasis of the treated eye after wide-field excimer laser PRK and subsequent topical corticosteroid application. We report the incidence of this phenomenon and evaluate possible explanations in retrospective and prospective studies. PATIENTS AND METHODS A single observer measured the horizontal pupil diameter, as well as the direct and …