Abstract
Purpose::
To compare the retinal thickness measurements using high-speed, high-resolution, Fourier-domain optical coherence tomography (FD-OCT) retinal images of retinal dystrophy patients to those of normal controls.
Methods::
Patients with retinal dystrophy and normal controls (age and gender matched) underwent imaging with the RTVue FD-OCT scanner (Optovue, Inc) which operates at 26,000 axial scans/second and 5 microns resolution. Vertical and horizontal 8 mm cross scans of 1024 lines/ cross section were obtained. The internal limiting membrane (ILM), inner plexiform layer (IPL), outer plexiform layer (OPL) and inner retinal pigment epithelium(RPE) boundaries were drawn on the OCT images. The total retinal thickness, inner retinal thickness (IRL) and outer retinal layer thickness (ORL) measurements were calculated. The inner retina thickness (IRL) was the sum of nerve fiber layer (NFL), ganglion cell layer (GCL) and inner plexiform layer (IPL) thicknesses. Whole retinal thickness (RT) was measured from the ILM to the RPE. Outer retinal thickness (ORL) was calculated by subtracting IRL thickness from RT. Fovea RT is measured at the central fovea. RT, IRL and ORL at 5mm are averaged from a 5 mm zone.
Results::
14 patients (7 retinal dystrophy patients and seven normal controls) underwent high resolution OCT imaging. Patients ranged in age from 33 to 84 years old. Retinal dystrophy diagnoses included retinitis pigmentosa (4), end-stage macular dystrophy (1), cone-rod degeneration (1) and Stargardts disease (1). The following thickness values reported are mean +/- standard deviation. Foveal RT = 66.3 +/- 5.8 µm normals and 31.2 +/- 12.3 µm dystrophy (p<0.001). IRL = 32.1 +/- 2 µm normals and 26.8 +/- 5.5 µm dystrophy (p<0.008). ORL= 63.2 +/- 2 µm normals and 32.1 +/- 6 µm dystrophy (P<0.001). RT at 5 mm diameter = 95.3 +/- 3.3 µm normals and 58.9 +/- 9.7 µm dystrophy (p<0.001).
Conclusions::
Eyes with retinal dystrophy had a small (16%) decrease in IRL and severe (48 %) decrease in ORL compared to normals. The higher resolution and definition of the RTVue FD-OCT technology facilitated measurements of the thickness of retinal sublayers.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical • retinal degenerations: hereditary