Purpose
To compare the rates of retinal nerve fiber layer (RNFL) loss in patients suspect of having glaucoma who developed visual field damage (VFD) to those who did not develop VFD, and to determine whether the rate of RNFL loss can be used to predict who will develop VFD..
Design
Prospective observational cohort study
Participants
Glaucoma suspects, defined as having glaucomatous optic neuropathy or ocular hypertension (Intraocular pressure (IOP)>21 mmHg) without repeatable VFD at baseline from the Diagnostic Innovations in Glaucoma Study, and the African Descent and Glaucoma Evaluation Study.
Methods
Global and quadrant RNFL thickness (RNFLT) were measured with the Spectralis spectral-domain optical coherence tomography (SD-OCT). VFD was defined as having 3 consecutive abnormal visual fields. The rate of RNFL loss in eyes developing VFD was compared with eyes not developing VFD using multivariable linear mixed-effects models. A joint longitudinal survival model utilized the estimated RNFLT slope to predict the risk of developing VFD, while adjusting for potential confounding variables.
Main Outcome Measures
The rate of RNFL thinning and the probability of developing VFD.
Results
Four hundred and fifty-four eyes of 294 glaucoma suspects were included. The average number of SD-OCT examinations was 4.6 (range, 2–9) with median follow-up time of 2.2 (0.4–4.1) years. Forty eyes (8.8%) developed VFD. The estimated mean rate of global RNFL loss was significantly faster in eyes developing VFD compared with eyes that did not (−2.02μm/year vs. −0.82μm/year, P<0.001). The joint longitudinal survival model showed that each 1μm/year faster rate of global RNFL loss corresponded to a 2.05 times higher risk of developing VFD (Hazards Ratio (HR)=2.05, 95% Confidence Interval (CI): 1.14–3.71; p=0.017).
Conclusions
The rate of global RNFL loss was more than twice as fast in eyes developing VFD compared with eyes that did not develop them. Joint longitudinal survival model showed that a 1μm/year faster rate of RNFLT loss corresponded to a 2.05 times higher risk of developing VFD. These results suggest that measuring the rate of SD-OCT RNFL loss may be a useful tool to help identify patients who are at a high risk of developing visual field loss.
Objective
To determine whether focal abnormalities of the lamina cribrosa (LC) are present in glaucomatous eyes with localized retinal nerve fiber layer (RNFL) defects.
Design
Cross-sectional observational study.
Participants
20 eyes of 14 subjects with localized RNFL defects detected by masked grading of stereophotographs and 40 eyes of 25 age-matched healthy subjects recruited from the Diagnostic Innovations in Glaucoma Study (DIGS) at the University of California, San Diego.
Methods
All eyes had stereoscopic optic disc photography and in vivo LC imaging using enhanced depth optical coherence tomography (EDI-OCT). Two masked graders identified focal LC defects defined by a standardized protocol using 48 radial scan EDI-OCT images. The Kappa coefficient was calculated as a measure of the reliability of interobserver agreement.
Main Outcome Measures
The number of focal LC defects and the relationship between the location of LC defects and the location of localized RNFL defects.
Results
15 of 20 eyes with a localized RNFL defect (75%) had at least one LC defect compared to only 1 of 40 healthy eyes (3%). 13 eyes with localized RNFL defects had 1 LC defect, 1 eye had 2 LC defects and 1eye had 3 LC defects. The largest area LC defect was present in a radial line EDI-OCT scan corresponding to a localized RNFL defect in 13/15 (87%) of eyes. There was good agreement between graders as to whether an eye had a LC defect (Kappa=0.87, 95% CI 0.73–1.00, P<0.001) and the location of the largest defect (Kappa=0.72, 95% CI 0.44–1.00, P<0.001).
Conclusions
Focal defects of the lamina cribrosa were frequently visible in glaucomatous eyes with localized RNFL defects. Focal abnormalities of the LC may be associated with focal retinal nerve fiber damage.
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