OCT detects glaucomatous damage up to 8 years before visual field
Researchers were able to assess the thickness of the retinal nerve fiber layer utilizing optical coherence tomography to detect glaucoma before the appearance of visual field defects, according to a study recently published inOphthalmology.
Kuang and colleagues conducted an observational cohort study to evaluate the diagnostic accuracy of retinal nerve fiber layer (RNFL) thickness measurements from OCT as well as gained lead time.
The study consisted of 75 eyes of 75 patients suspected of having glaucoma and 75 eyes of 75 healthy subjects. Researchers analyzed RNFL thickness measurements, which were taken when the earliest standard automated perimetry (SAP) defect was detected and yearly before field loss development.
Results showed that when visual field defects were detected, average RNFL thickness was 90.6±8.0 μm in healthy eyes and 75.0±9.8 μm in glaucomatous eyes. Researchers noted that significant differences in RNFL thickness were discovered up to 8 years before the presence of visual field defects.
“For example, at 95% specificity cutoff, up to 44% of subjects had abnormal average RNFL thickness at 2 years before development of a field defect,” they stated. “This number reduced to 35% at 4 years and to 19% at 8 years. Although 19% may be seen as an apparently small proportion, it is important to consider that 8 years is a relatively large amount of time, and such lead time could have significant management implications to a significant group of patients.”
The authors concluded: “Assessment of RNFL thickness with OCT was able to detect glaucomatous damage before the appearance of visual field defects on SAP. In many subjects, significantly long lead times would be gained when applying OCT as an ancillary diagnostic tool……