Abstract
Purpose::
To determine if the glaucoma diagnostic ability can be enhanced by measuring the inner retinal layer thickness using the newly-developed fourier domain optical coherence tomography (FD-OCT).
Methods::
RTVue FD-OCT (Optovue, Inc) is a high speed, high resolution FD-OCT with 2X resolution and 65X acquisition speed compared to the Stratus time-domain OCT (TD-OCT). Unlike the Stratus TD-OCT which allows only total macular thickness measurements, the RTVue FD-OCT is capable of automatic retinal layer segmentation analysis in addition to providing total macular thickness using a new macular scan pattern called Macular Mapping 7mm (MM7). The FD-OCT MM7 scan allows measurement of the inner retinal layer (IRL) thickness, which was the sum of nerve fiber, ganglion cell and inner plexiform layers, which are the retinal layers preferentially affected in glaucoma. The data was obtained from the USC portion of the Advanced Imaging for Glaucoma Study (www.AIGStudy.net), a multi-center, prospective, longitudinal observational study. Normal (N) and perimetric glaucoma (PG) eyes were scanned on both the RTVue and Stratus OCT. Area under receiver operating curve (AROC) was used to assess the ability to discriminate between N and PG eyes.
Results::
Forty-four N and 47 PG eyes were included in this analysis. Statistically significant thinning was found in the macular IRL and whole retina in the PG group relative to normal eyes. The AROC for FD-OCT IRL (0.93±0.03) was statistically better than total retinal thickness (AROC=0.85±0.04 on FD-OCT, p=0.01,AROC= 0.84±0.04 on Stratus TD-OCT, p=0.01). Additionally, the average fractional loss map (PG - N / N) showed a pattern of inferior and superior arcuate bundle pattern of inner retinal thinning.
Conclusions::
FD-OCT enhanced the ability to discriminate normal eyes from glaucomatous eyes using the new retinal layer segmentation providing IRL thickness measurements. The FD-OCT measured IRL thickness was found to be better than total retinal thickness for glaucoma diagnosis by either FD-OCT or Stratus TD-OCT. The FD-OCT macular IRL also showed a characteristic bi-arcuate pattern of loss. The faster speed of FD-OCT allows high density scanning over a larger region of the macula with less motion artifact that provides greater detail and improved measurement of the ganglion cell-related layers that are preferentially affected in glaucoma.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • macula/fovea • ganglion cells