Tono-Pen versus Goldmann tonometry after excimer laser photorefractive keratectomy

To compare intraocular pressure (IOP) measurements by the Tono-Pen 2 tonometer and Goldmann applanation tonometer (GAT) in post-photorefractive keratectomy (PRK) patients.

Refractive Surgery Center, Assaf Harofeh Medical Center, Zerifin, Israel.

In 18 patients, IOP was measured by GAT and then by Tono-Pen 2 tonometer 2 to 18 months following PRK (mean 6.6 months +/- 5.1 [SD]). Photorefractive keratectomy had been performed in 1 eye of each patient; the fellow eyes served as controls. Corneal curvature and thickness were evaluated. Ten of the 18 patients were treated with topical steroids.

In the post-PRK eyes, mean GAT IOP was 1.8 +/- 3.1 mm Hg lower than mean Tono-Pen IOP (P = .012); there was no significant IOP difference in the control (fellow) eyes. In steroid-treated post-PRK eyes, mean GAT IOP (12.2 mm Hg) was 2.2 +/- 1.3 mm Hg lower than mean Tono-Pen IOP (14.4 mm Hg) (P = .0007). Mean Tono-Pen IOP in steroid-treated post-PRK eyes was 4.3 +/- 3 mm Hg higher than in the fellow eyes (P = .0014); mean GAT IOP was only 2.3 +/- 3.5 mm Hg higher (P = .04). In post-PRK eyes without topical steroid treatment, mean GAT IOP was 2.0 +/- 1.18 mm Hg lower than in the fellow eyes (P = .001); there was no significant difference in Tono-Pen IOP. There was a negative correlation between the difference in IOP values (Tono-Pen minus GAT) and corneal curvature in post-PRK eyes (r = 0.76, P = .0108, n = 15).

The Tono-Pen tonometer appeared to be less affected than the GAT by the relative flattening, thinning, and anterior stromal decreased rigidity of the central cornea that occur following PRK. Post-PRK steroid-induced IOP elevation may be masked by the artifactual decrease in GAT IOP.