Abstract
Purpose: :
To evaluate sensitivity (Sn) and specificity (Sp) of thickness measurements of ganglion cell layer (GCL) and ganglion cell complex (GCC, from the internal limiting membrane to the outer border of inner plexiform layer) in the macular area using a spectral-domain optical coherence tomography (SD-OCT; 3D OCT-1000, Topcon, Inc.) for diagnosis of preperimetric or early glaucoma.
Methods: :
In 41 eyes with early glaucoma (EG, mean deviation of HFA 24-2 SITA-s > -5 dB ), 18 with preperimetric glaucoma (PG, apparent retinal nerve fiber layer defects but no significant change on HFA 24-2 SITA-s), and 42 normal eyes, retinal imaging was performed with the SD-OCT with a vertical raster scan protocol in a 6 x 6 mm squared macular area, and thickness of GCL and GCC was determined with an automated segmentation algorithm of the retinal layers in 5 x 5 mm squared area centered on the automatically detected foveal center. The 1st-percentile value in each parameter in other 100 normal eyes was applied as a cutoff value for the diagnosis. If mean thickness was less than the cutoff value in at least one grid, the eye was diagnosed as glaucoma.
Results: :
When using the total average thickness in the 5 x 5 mm area, Sn of EG was 53.7%, Sn of PG 11.1%, and Sp 100% for the GCL thickness; and those were 61.0%, 5.6%, and 100% for the GCC thickness measurement. When the area divided into smaller grids, Sn increased, while Sp decreased. The best performance was obtained when dividing into 8 x 8 grids (each grid was a 0.63x 0.63 mm square), with which Sn of EG was 92.7%, Sn of PG 90.7%, and Sp 91.5% for the GCL thickness; and those were 94.4%, 94.3%, and 84.5% for the GCC thickness.
Conclusions: :
Sn and Sp of GCL measurement for diagnosing EG and PG were comparable to those of GCC measurement. The best performance was obtained when using 0.6 x 0.6 mm grids in the macular area.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • ganglion cells