Retinal nerve fiber layer thickness changes after an acute increase in intraocular pressure

To determine whether the increase in intraocular pressure (IOP) for 45 seconds during laser in situ keratomileusis (LASIK) suction can induce a decrease in retinal nerve fiber layer thickness (RNFLT) assessed by a confocal scanning laser polarimeter.

Jules Gonin Hospital, University of Lausanne, Lausanne, Switzerland.

Eleven normal volunteers were enrolled in the study. The optic disc of each eye was analyzed by the GDx(R) Nerve Fiber Analyzer (Laser Diagnostic Technologies, Inc.), version 1.0.14. Using the standard circle that appears as a 10-pixel green circle on the GDx display, the system assessed the RNFLT at 1.75 disc diameter from the outer edge of the optic nerve head. To further evaluate the possible retinal nerve fiber layer (RNFL) loss, the 360-degree circumference was divided into 36 segments measuring 10 degrees each and the RNFLT was calculated for each sector. All subjects had a GDx assessment before 100 mm Hg ocular compression of 1 eye for 45 seconds and then 2 minutes and 1 month after compression.

Before compression, the mean RNFLT was 69.09 microm +/- 10.96 (SD); it was 69.27 +/- 10.98 microm after 2 minutes and 67.00 +/- 10.58 microm after 1 month. No statistically significant difference was found between the before and after measurements.

A 45-second acute increase in IOP, such as during LASIK suction, did not decrease the RNFLT in normal eyes.