[Validity and reproducibility of sensor contact lens profiles in comparison to applanation tonometry in healthy eyes]

Purpose: The aim of this study was to check the validity of the profiles gained by a sensor contact lens in one eye. We compared these values with measurements done by applanation tonometry in the other eye. The measurements were done in different body postures and head positions. All examinations were repeated 2 to 8 weeks afterwards to check the reproducibility.

Patients, material and methods: Five young healthy individuals with normal eyes had the intraocular pressure (IOP) of their right eye measured by applanation tonometry (Goldmann and Perkins) in different postures (45 minutes upright, 30 minutes supine, 20 minutes head-body down and 30 minutes upright). Simultanously the left eye had a sensor contact lens, which measured the changes of the corneal curvature due to changes of the IOP within intervals of 5 minutes. Within 2-8 weeks all examinations were repeated completely in the same manner.

Results: After 45 minutes in upright position the mean IOP remained unchanged (14 mmHg), increased after 30 minutes in supine position (20 mmHg), increased again after 20 minutes in head-body-down position (22.4 mmHg) and came back to 14 mmHg after 30 minutes in upright position. A very similar profile was obtained in the repeat examinations. In contrast, the mean profiles gained by the sensor contact lens were not in a positive slope-like shape, but the mean values showed a flat or surprisingly, an even downward profile (head-body-down position). No statistical differences were found between all mean values of the first and repeat examinations.

Conclusions: Intraocular pressure measurements gained by applanation tonometry showed the expected physiological positive slope profile during changes of the body and head positions (upright, supine, head-body-down). None of the profiles simultaneously gained by the sensor contact lens had a slope-like shape, but were flat or even downward. The reasons for the lacking validity between applanation tonometry and sensor contact lens cannot be explained. This makes the interpretation of Triggerfish profiles uncertain and they should therefore be done with caution. The reproducibility of the applanation tonometry values as well as of the sensor contact lens values was good and showed no significant differences.