Using 24-hr ocular dimensional profile recorded with a sensing contact lens to identify primary open-angle glaucoma patients with intraocular pressure constantly below the diagnostic threshold

Purpose: To evaluate the use of a 24-hr ocular dimensional profile recorded with a contact lens sensor (CLS) combined with a single tonometric intraocular pressure (IOP) reading to indicate the potential for exceeding the diagnostic threshold for normal tension glaucoma (NTG) in Japanese patients.

Methods: Intraocular pressure (IOP) of untreated Japanese NTG patients was measured with tonometry every 3 hr from 9:00 to 24:00. The subsequent day a 24-hr CLS (SENSIMED Triggerfish, Sensimed AG, Lausanne, Switzerland) profile was recorded on the same eye. Patients initially diagnosed as NTG were reclassified as NTG when the measured IOP values were consistently <20 mmHg or as primary open-angle glaucoma (POAG) when IOP was ≥20 mmHg in at least 1 measurement. For each patient and each IOP time-point, IOP values were combined with information provided by the CLS profile ('classifier') to indicate the potential for exceeding the diagnostic threshold value. Statistical analyses were performed for each classifier.

Results: A total of 65 patients, 28 males and 37 females (mean ages: 50.8 ± 14.6 years and 52.6 ± 10.2 years, respectively), were analysed. Following IOP diurnal measurement, five patients (7.7%) were reclassified as POAG. Two classifiers (15:00 CLS and 18:00 CLS) showed high sensitivity and negative predictive value (100%), identifying all the POAG patients.

Conclusion: Contact lens sensor information can be used in conjunction with a single tonometric reading to determine patients' potential of having IOP levels exceeding the diagnostic threshold within a 24-hr period, without the need to perform a 24-hr tonometric curve. This would allow clinicians to identify POAG patients who may otherwise be eventually misclassified as NTG.