Comparison of intraocular pressure measurement between Goldmann applanation tonometer and Tonopen

Background: Primary open-angle glaucoma (POAG) is a chronic optic neuropathy causing visual field loss and open angles. It accounts for 90% of glaucoma cases and is linked to raise intraocular pressure (IOP). POAG is the most common type of glaucoma. It is a chronic, progressive optic neuropathy that leads to characteristic optic nerve damage and visual field loss, often associated with elevated IOP. IOP is currently the only modifiable risk factor in POAG that can be affected by family. The Goldmann applanation tonometer (GAT) is the international standard. Aims and Objectives: The objective is to compare IOP measurement by GAT and Tonopen in diagnosed glaucoma suspect patients. Materials and Methods: This is a hospital-based cross-sectional study done in the glaucoma clinic of Lumbini Eye Institute and Research Centre. A total of 88 Glaucoma suspect patients were recruited using a convenience sampling technique. IOP was measured in one eye, calibrated daily, and repeated if readings differed by more than 5 mmHg. Topical anesthesia was used. Results: The majority of participants in the study, representing 55.7% of the 88 patients, were female. About 58% of the study participants were from India, making up the majority. The largest percentage of participants (38.8%) was in the 25–40 age range. The mean corneal thickness was higher in men (544.41±27.69 μm) than in women (535.71±36.05 μm). In both eyes, the mean IOP readings are higher with Tonopen than GAT. Conclusion: IOP measurements obtained with the Tonopen often show higher readings compared to those from the GAT. While the Tonopen cannot replace GAT as the gold standard, it works as a valuable screening tool, especially in peripheral areas or in resource-limited settings.