Impact of Intraocular Pressure Control on Rates of Retinal Nerve Fiber Layer Loss in a Large Clinical Population

Abstract

Purpose: To investigate the impact of intraocular pressure (IOP) control on rates of change of spectral-domain OCT (SD-OCT) retinal nerve fiber layer (RNFL) thickness in a large clinical population.

Design: Retrospective cohort study.

Participants: A total of 85 835 IOP measurements and 60 223 SD-OCT tests from 14 790 eyes of 7844 patients.

Methods: Data were extracted from the Duke Glaucoma Registry, a large database of electronic medical records of patients with glaucoma and suspected disease followed over time at the Duke Eye Center and satellite clinics. All records from patients with a minimum of 6 months of follow-up and at least 2 good-quality SD-OCT scans and 2 clinical visits with Goldmann applanation tonometry were included. Eyes were categorized according to the frequency of visits with IOP below cutoffs of 21 mmHg, 18 mmHg, and 15 mmHg over time. Rates of change for global RNFL thickness were obtained using linear mixed models and classified as slow if change was slower than -1.0 μm/year; moderate if between -1.0 and -2.0 μm/year; and fast if faster than -2.0 μm/year. Multivariable models were adjusted for age, gender, race, diagnosis, central corneal thickness, follow-up time, and baseline disease severity.

Main outcome measures: Rates of change in SD-OCT RNFL thickness according to levels of IOP control.

Results: Eyes had a mean follow-up of 3.5±1.9 years. Average rate of change in RNFL thickness was -0.68±0.59 μm/year. Each 1 mmHg higher mean IOP was associated with 0.05 μm/year faster RNFL loss (P < 0.001) after adjustment for potentially confounding variables. For eyes that had fast progression, 41% of them had IOP <21 mmHg in all visits during follow-up, whereas 20% of them had all visits with IOP <18 mmHg, but only 9% of them had all visits with IOP <15 mmHg.

Conclusions: Intraocular pressure was significantly associated with rates of progressive RNFL loss in a large clinical population. Eyes with stricter IOP control over follow-up visits had a smaller chance of exhibiting fast deterioration. Our findings may assist clinicians in establishing target pressures in clinical practice.

Figure 2.

Proportion of Eyes, Mean Intraocular Pressure (IOP), and Mean Rates of Change of Spectral-Domain Optical Coherence Tomography (SD OCT) Retinal Nerve Fiber Layer (RNFL) Thickness According to the Percentage of Visits with IOP Below 21mmHg, 18mmHg, and 15mmHg During Follow-up. Capped Spikes Represent 95% Confidence Intervals.

Figure 3.

Proportion of Eyes Classified as Slow, Moderate, and Fast Progressors According to the Rates of Change of Spectral-Domain Optical Coherence Tomography (SD OCT) Retinal Nerve Fiber Layer (RNFL) Thickness. Eyes Are Grouped According to the Percentage of Visits with Intraocular Pressure (IOP) Below (A) 21mmHg, (B) 18mmHg and (C) 15mmHg During Follow-up. Rates of SD OCT global RNFL thickness change: slow, if slower −1.0 μm/year; moderate, if between −1.0 and −2.0 μm/year; fast, if faster than −2.0 μm/year.

Figure 5.

(A) Proportion of Eyes, (B) Mean Intraocular Pressure (IOP) and (C) Mean Rates of Change for Each Category of Average IOP During Follow-up, and (D) the Proportion of Eyes Classified as Slow, Moderate, and Fast Progressors Within Each Category According to the Rates of Change of Spectral-Domain Optical Coherence Tomography (SD OCT) Retinal Nerve Fiber Layer (RNFL) Thickness. Capped Spikes Represent 95% Confidence Intervals. Rates of SD OCT global RNFL thickness change: slow, if slower than −1.0 μm/year; moderate, if between −1.0 and −2.0 μm/year; fast, if faster than −2.0 μm/year.