Correlation between retinal nerve fiber layer thickness and IOP variation in glaucoma suspects and patients with primary open-angle glaucoma

Purpose: To analyze the relationship between retinal nerve fiber layer thickness (RNFLT) and intraocular pressure (IOP) variation in glaucoma suspects (GS) and patients with primary open-angle glaucoma (POAG). Methods: Thirty-one GS and 34 POAG patients underwent ophthalmologic examination and 24-h IOP measurements. GS had IOPs ranging from 19 to 24 mmHg and/or suspicious appearance of the optic nerve. POAG patients had reproducible abnormal visual fields. We only included patients who presented with short-term IOP fluctuation >6 mm Hg ( increment IOP). Only one eye per patient was included through a randomized process. Peripapillary RNFLT was assessed by spectral-domain optical coherence tomography. We correlated RNFLT with IOP parameters. Results: Mean IOP was similar between GS and POAG groups (15.6 +/- 3.47 vs 15.6 +/- 2.83 mmHg,p = 0.90) as was IOP peak at 6 AM (21.7 +/- 3.85 vs 21.3 +/- 3.80 mmHg,p = 0.68). Statistically significant negative correlations were found in POAG group between IOP at 6 AM and RNFLT in global (r(s) = -0.543;p < 0.001), inferior (r(s) = -0.540;p < 0.001), superior (r(s) = -0.405;p = 0.009), and nasal quadrants (r(s) = -0.561;p < 0.001). Negative correlations were also found between increment IOP and RNFLT in global (r(s) = -0.591;p < 0.001), and all other sectors (p < 0.05). In GS IOP at 6 AM correlated only with inferior quadrant (r(s) = -0.307;p = 0.047). Conclusion: IOP at 6 AM and increment IOP had negative correlations with RNFLT quadrants in POAG. In GS this correlation occurred between IOP at 6 AM and inferior quadrant. These findings may indicate potential risk factors for glaucoma progression.

Automated summary

There were negative correlations between IOP at 6 AM and increment IOP with RNFLT quadrants in POAG patients, while in GS patients, only IOP at 6 AM was negatively correlated with the inferior quadrant. These findings suggest potential risk factors for glaucoma progression.