Correlation between intraocular pressure level and optic disc changes in high-tension glaucoma suspects

Abstract

Purpose: To assess the correlation between intraocular pressure (IOP) and future optic disc changes in eyes of patients suspected of having high-tension glaucoma and to determine the target pressure in eyes of patients suspected of having high-tension glaucoma.

Design: Prospective, comparative, observational case series.

Participants: Fifty-seven eyes of 57 patients suspected of having high-tension glaucoma selected from 226 consecutive patients with glaucoma or suspected glaucoma.

Intervention: The status of the optic disc and visual fields was evaluated during an initial examination by confocal laser ophthalmoscopy and automatic perimetry, respectively. Fifty-seven eyes were followed up for at least 2.5 years and then underwent a final examination. IOP was measured every 3 months.

Main outcome measures: The correlation between changes in optic disc status and IOP control during follow-up was determined. Changes in the optic disc were evaluated by using the percentage change in total contour area, neuroretinal rim area, and cup-to-disc ratio. The control IOPs were evaluated on the basis of the percentage of time during which IOP was <18 mmHg (%<18 mmHg control) and <21 mmHg (%<21 mmHg control) during follow-up in each eye. The correlation between visual field changes and IOP control was also analyzed.

Results: Results from 48 (84.2%) of 57 participants were included. Patients were followed up for a mean 4.4 years. The %<21 mmHg control was significantly correlated with changes in neuroretinal rim area (r = 0.40; P = 0.0055) and in cup-to-disc ratio (r = -0.40; P = 0.0051) by linear regression analysis. The correlations were also significant if the difference in the length of follow-up was adjusted by multivariate regression analysis. There was no significant correlation between %<18 mmHg control and changes in disc parameters. Seven (14.6%) of 48 eyes had glaucomatous visual field defects at the final examination. The %<21 mmHg control was significantly lower in eyes with visual field changes compared with eyes with no changes (P = 0.0153; unpaired t test). In contrast, %<18 mmHg control was not significantly different between eyes with and without visual field changes (P = 0.3886).

Conclusions: The IOP level correlates with topographic changes in the optic disc in eyes of patients suspected of having high-tension glaucoma. The target pressure for such eyes may need to be between 18 and 21 mmHg, and <18 mmHg is a safe target level in the treatment of patients suspected of having high-tension glaucoma to delay topographic optic disc changes.