Identification of risk factors in the progression from ocular hypertension to glaucoma

Objective: The aim of this thesis was to evaluate structural and functional changes in the optic nerve and retinal nerve fiber layer (RNFL) in patients followed with a diagnosis of ocular hypertension (OHT), and to identify risk factors associated with conversion to glaucoma. Materials and Methods: In this study, 46 eyes of 46 patients diagnosed with OHT and followed regularly in our clinic for at least five years were included. Demographic data, systemic disease histories, and detailed ophthalmologic examination findings were recorded. Structural assessment was performed using spectral-domain optical coherence tomography (SD-OCT) with RNFL measurements, while functional assessment was conducted using visual field testing (Humphrey Visual Field Analyzer, Carl Zeiss Meditec, Dublin, CA, USA). Visual field progression was analyzed using the Save Sight Years (SSY) engine. Glaucomatous progression was defined based on changes detected in the visual field and/or RNFL measurements. Statistical analyses were performed using SPSS version 18.0, and a p value <0.05 was considered statistically significant. Results: The mean age of the patients was 46.52±15.93 years, and the mean follow-up duration was 8 years. No glaucomatous progression was observed in 58.7% of the patients, whereas 6.5% showed progression only in the visual field, 26.1% showed progression only in the RNFL, and 8.7% demonstrated progression in both the visual field and RNFL. The mean age of patients with visual field progression was significantly higher than that of patients without progression (p=0.049). In addition, baseline mean deviation (MD) and visual field index (VFI) values were significantly worse in patients who developed visual field progression compared to those without progression (p=0.012; p=0.008). In patients who showed glaucomatous progression based on RNFL measurements, both the maximum intraocular pressure (IOP) and mean IOP values recorded during follow-up were significantly higher than in patients without progression (both p=0.001). Furthermore, in patients who demonstrated progression according to any assessment method, refractive error, maximum IOP, and mean IOP during follow-up were significantly higher compared to patients without glaucomatous progression (all p<0.05). To identify risk factors associated with conversion to glaucoma in patients with OHT, a model including age, mean IOP, and baseline cup-to-disc (C/D) ratio was constructed. According to this model, each 1-unit increase in age increased the risk of glaucoma conversion by 1.083-fold, each 1 mmHg increase in mean IOP increased the risk by 1.835-fold, and each 0.1-unit increase in baseline C/D ratio increased the risk by 2.279-fold (Nagelkerke R² = 0.526). In addition, exfoliation, pigment dispersion, and degenerative myopia were observed more frequently in patients who developed glaucomatous damage. Conclusion: This study demonstrated the rates of glaucoma conversion and identified clinical and imaging-based risk factors associated with this conversion during long-term follow-up of patients with OHT. Advanced age, higher mean IOP, increased baseline C/D ratio, and worse baseline visual field MD values were identified as independent risk factors for glaucoma conversion, consistent with findings from the Ocular Hypertension Treatment Study (OHTS) and similar risk models. The higher frequency of RNFL progression compared to visual field progression is consistent with the literature indicating that structural damage precedes functional loss. Combined evaluation of structural and functional parameters in the follow-up of patients with OHT may contribute to earlier detection of damage and the determination of appropriate treatment strategies.