Abstract
Purpose:
Recently, the cone mosaic images can be obtained using the commercially available adaptive optics fundus camera (rtx1TM: Imagine eyes, France). More recently, the cone counting software “AO detect TM” (Imagine eyes, France) has become available. Because the accuracy of this software has not been studied, the purpose of this study is to evaluate the accuracy of this software.
Methods:
The cone mosaic images were obtained using rtx1TM from 1 to 5.5 degree temporal from the fovea. Cone packing density at 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, and 5.5 degree temporal from the fovea was calculated using AO detect TM. Cone packing density in the same images was also calculated manually using ImageJ (National Institutes of Health, USA). Cone packing density calculated using AO detect TM alone (ACD) and counted manually (MCD) were compared.
Results:
Normal 17 eyes of 17 subjects (age 21 to 46 years; axial length 22.78 to 26.70 mm) were evaluated. ACD was highest at 2 degree and decreased with increasing eccentricity from 2 degree (mean±SD : 2.08±0.42 x104, 2.37±0.41 x104, 2.53±0.32 x104, 2.40±0.28 x104, 2.14±0.27 x104, 1.94±0.19 x104, 1.73±0.19 x104, 1.58±0.15 x104, 1.46±0.17 x104, 1.41±0.15 x104 cells/mm2 at 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, and 5.5 degree respectively). MCD was higher close to the fovea and decreased with increasing retinal eccentricity (mean±SD: 3.75±0.46 x104, 3.58±0.34 x104, 3.04±0.38 x104, 2.66±0.31 x104, 2.28±0.27 x104, 2.02±0.20 x104, 1.79±0.19 x104, 1.63±0.16 x104, 1.51±0.17 x104, and 1.44±0.15 x104 cells/mm2 at 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, and 5.5 degree respectively). The mean±SD percentage of the cones detected by AO detect (ACD/MCD ratio) was the lowest at 1 degree and it increased with increasing retinal eccentricity (57.7±5.8, 66.4±10.1, 83.5±8.5, 90.4±4.5, 93.7±3.1, 95.8±1.7, 96.6±2.0, 97.2±1.8, 98.2±1.1% at 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, and 5.5 degree respectively).
Conclusions:
At the macula nearer than 2.5 degree from the fovea, “AO detect TM” underestimate the cone packing density significantly and the manual counting is necessary. The automatic cone counting software “AO detect TM” is clinically useful when the retinal eccentricity is more than 2.5 degree in the healthy eyes.