Tono-Pen determination of intraocular pressure in patients with band keratopathy or glued cornea

Aims-To evaluate the intraocular pressure (IOP) measurements in patients with band keratopathy or glued corneas obtained from affected and non-affected areas. Methods-15 patients with band keratopathy or glued corneas were prospectively recruited. When both eyes were affected, only the right eye was analysed. Tone-Pen readings of IOP were obtained sequentially from the affected and non-affected corneal surface. Additionally, Goldmann applanation tonometry was attempted. Results-Determination of IOP with the Tone-Pen was possible in all cases, while Goldmann tonometry was not performed in three patients because of severe corneal irregularities. The average of the Tono-Pen readings obtained from the affected cornea (34.8 (SD 14.0) mm Hg) was consistently and significantly higher (p<0.001) than mean IOP obtained by the Tone-Pen from the non-affected area (14.8 (4.3) mm Hg). The average of Goldmann tonometry readings (14.4 (6.1) mm Hg) did not differ significantly from the Tono-Pen values obtained from the non-affected corneal area (p=0.47) but was significantly lower than the Tone-Pen measurements obtained from the affected area (p<0.001) Conclusion-In patients with band keratopathy or glued corneas determination of IOP by Tone-Pen tonometry varies from affected to non-affected area. The Tono-Pen overestimates the level of IOP when it is applied to areas with band keratopathy or with glue.