Accuracy and predictability of the compensatory function of Orbscan II in intraocular pressure measurements after laser in situ keratomileusis

Purpose: To evaluate the usefulness of the compensatory function of Orbscan II (Orbtek, Bausch & Lomb) for measuring postoperative intraoperative pressure (IOP) in laser in situ keratomileusis (LASIK) patients. Setting: Department of Ophthalmology, Ilsan Paik Hospital, Inje University, Ilsan, Korea. Methods: Two hundred ten patients had LASIK using the Hansatome® microkeratome (Bausch & Lomb) and the MEL 70 G-scan laser (Aesclepion-Meditec) and were examined retrospectively. The patients included in the study were divided into 2 groups: Group 1, 123 eyes with less than –6.0 diopters (D) of myopia; Group 2, 60 eyes with more than –6.0 D of myopia. The IOP was measured preoperatively and 2 and 4 weeks after LASIK using a noncontact tonometer (NCT CT-60, Topcon). The results were corrected with the Orbscan II program. Results: The mean IOPs in Group 1 were 16.35 mm Hg ± 2.90 (SD) preoperatively, 10.80 ± 2.21 mm Hg at 2 weeks, and 10.63 ± 2.28 mm Hg at 4 weeks. After compensation with Orbscan II, the 2-week and 4-week values were 16.81 ± 3.14 mm Hg and 16.68 ± 3.22 mm Hg, respectively. The mean IOPs in Group 2 were 17.63 ± 2.93 mm Hg, 10.07 ± 1.55 mm Hg, and 10.43 ± 1.84 mm Hg, respectively; after compensation, they were 18.40 ± 4.09 mm Hg and 18.05 ± 4.09 mm Hg, respectively. After compensation with Orbscan II, there were no statistically significant differences between the preoperative and postoperative IOPs. Conclusions: Orbscan II may help predict actual IOP values after LASIK and avoid the misinterpretation of high IOPs as normal IOPs.