Association between Intraocular Pressure and Rates of Retinal Nerve Fiber Layer Loss Measured by Optical Coherence Tomography.

PURPOSE: To evaluate the relationship between intraocular pressure (IOP) and rates of retinal nerve fiber layer (RNFL) thickness change over time measured by spectral-domain (SD) optical coherence tomography (OCT). DESIGN: Observational cohort study. PARTICIPANTS: The study involved 547 eyes of 339 patients followed up for an average of 3.9±0.9 years. Three hundred eight (56.3%) had a diagnosis of glaucoma and 239 (43.7%) were considered glaucoma suspects. METHODS: All eyes underwent imaging using the Spectralis SD OCT (Heidelberg Engineering GmbH, Heidelberg, Germany), along with IOP measurements and standard automated perimetry (SAP). Glaucoma progression was defined as a result of "Likely Progression" from the Guided Progression Analysis software for SAP. Linear mixed models were used to investigate the relationship between average IOP during follow-up and rates of RNFL thickness change, while taking into account potential confounding factors such as age, race, corneal thickness, and baseline disease severity. MAIN OUTCOME MEASURES: The association between IOP and rates of global and sectorial RNFL thickness loss measured by SD OCT. RESULTS: Forty-six eyes (8.4%) showed progression on SAP during follow-up. Rates of global RNFL thickness change in eyes that progressed by SAP were faster than in those that did not progress (-1.02 vs. -0.61 µm/year, respectively; P = 0.002). For progressing eyes, each 1-mmHg higher average in IOP during follow-up was associated with an additional average loss of 0.20 µm/year (95% confidence interval [CI]: 0.08 to 0.31 µm/year; P < 0.001) of global RNFL thickness versus only 0.04 µm/year (95% CI: 0.01 to 0.07 µm/year; P = 0.015) for nonprogressing eyes. The largest associations between IOP and rates of RNFL change were seen for measurements from the temporal superior and temporal inferior sectors, whereas the smallest association was seen for measurements from the nasal sector. CONCLUSIONS: Higher levels of IOP during follow-up were associated with faster rates of RNFL loss over time measured by SD OCT. These findings support the use of SD OCT RNFL thickness measurements as biomarkers for the evaluation of the efficacy of IOP-lowering therapies to slow down the rate of disease progression.

Predicting progression of glaucoma from rates of frequency doubling technology perimetry change.

PURPOSE: To evaluate the ability of longitudinal frequency doubling technology (FDT) to predict the development of glaucomatous visual field loss on standard automated perimetry (SAP) in glaucoma suspects. DESIGN: Prospective, observational cohort study. PARTICIPANTS: The study included 587 eyes of 367 patients with suspected glaucoma at baseline selected from the Diagnostic Innovations in Glaucoma Study (DIGS) and the African Descent and Glaucoma Evaluation Study (ADAGES). These eyes had an average of 6.7 ± 1.9 FDT tests during a mean follow-up time of 73.1 ± 28.0 months. METHODS: Glaucoma suspects had intraocular pressure (IOP) >21 mmHg or an optic disc appearance suspicious of glaucoma. All patients had normal or nonrepeatable abnormal SAP at baseline. Humphrey Matrix FDT (Carl Zeiss Meditec, Inc, Dublin, CA) testing was performed within 6 months of SAP testing. The study end point was the development of 3 consecutive abnormal SAP test results. Joint longitudinal survival models were used to evaluate the ability of rates of FDT pattern standard deviation (PSD) change to predict the development of visual field loss on SAP, adjusting for confounding variables (baseline age, mean IOP, corneal thickness, and follow-up measurements of SAP PSD). MAIN OUTCOME MEASURES: The R(2) index was used to evaluate and compare the predictive abilities of the model containing longitudinal FDT PSD data with the model containing only baseline data. RESULTS: Sixty-three of 587 eyes (11%) developed SAP visual field loss during follow-up. The mean rate of FDT PSD change in eyes that developed SAP visual field loss was 0.07 dB/year versus 0.02 dB/year in those that did not (P < 0.001). Baseline FDT PSD and slopes of FDT PSD change were significantly predictive of progression, with hazard ratios of 1.11 per 0.1 dB higher (95% confidence interval [CI], 1.04-1.18; P = 0.002) and 4.40 per 0.1 dB/year faster (95% CI, 1.08-17.96; P = 0.04), respectively. The longitudinal model performed significantly better than the baseline model with an R(2) of 82% (95% CI, 74-89) versus 11% (95% CI, 2-24), respectively. CONCLUSIONS: Rates of FDT PSD change were highly predictive of the development of SAP visual field loss in glaucoma suspects. This finding suggests that longitudinal FDT evaluation may be useful for risk stratification of patients with suspected glaucoma.

Optical coherence tomography of the retina and optic nerve - a review.

Optical coherence tomography (OCT) is a rapid non-contact method that allows in vivo imaging of the retina, optic nerve head and retinal nerve fibre layer (RNFL). Since its introduction in Ophthalmology approximately a decade ago, the use of this technology has disseminated into the clinical practice. OCT has proven to be a useful ancillary tool for assessing retinal diseases because of its capability to provide cross-sectional images of the retina, and also to perform quantitative analysis of retinal morphology. In glaucoma, the OCT represents one of the methods capable of documenting and analysing optic disc and RNFL morphology in attempt to diagnose and monitor glaucomatous optic neuropathy. Recently, the spectral domain OCT became available, a new technique that allowed major improvements particularly regarding image acquisition speed and image resolution. Future studies will address how these major technological advances will impact the use of the OCT in research and clinical practice.