Objectives: To assess the usefulness of measuring in primary care the intraocular pressure (IOP) of diabetics as a glaucoma screening test, validating the Schiörtz tonometer for this end. To analyse the prevalence of glaucoma and associated risk factors in our diabetic population.
Design: An observational crossover study.
Setting: Primary Care. Concentaina Health Centre.
Patients: 144 patients in our centre's diabetes mellitus health programme.
Measurements and main results: There were 31 cases of IOP over 20 mmHg measured with the Schiörtz tonometer, on whom the ophthalmologist repeated the measurement with the Perkins tonometer, i.e. viewing the back of the eye to confirm the existence of papillary cupping consistent with the presence of Glaucoma. We chose a group with normal IOP, homogeneous with the group with high IOP to validate the Schiörtz tonometer, using as confirmation the results obtained by the ophthalmologist with the Perkins tonometer; and as confirmation in the detection of glaucoma, finding papillary excavation in the binocular ophthalmoscopy. Prevalence of glaucoma was 11%, which was 75% in the newly diagnosed cases. The positive predictive value of the Schiörtz tonometer in detecting increases in IOP was 87.1%, and with respect to the detection of glaucoma, it was 35.5%.
Conclusions: The high prevalence of glaucoma in diabetic patients justifies the systematic study of this risk factor. The Schiörtz tonometer is a useful and valid method, that can be used in primary care for glaucoma screening in this population group.