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B. Lee, D.-U. Bartsch, I. Kozak, L. Cheng, W. R. Freeman; Comparison of a Novel Confocal Scanning Laser Ophthalmoscopic Macular Topography Algorithm Using the HRT3 With Stratus Oct in the Measurement of Macular Volume and Thickness. Invest. Ophthalmol. Vis. Sci. 2007;48(13):115.
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© ARVO (1962-2015); The Authors (2016-present)
To present a rapid and potentially more reproducible method to determine macular volume and thickness using a novel HRT3 algorithm and to compare with StratusOCT. This new retina module of HRT3 software can provide topographic information on macular volume and thickness.
Forty-nine randomly selected eyes were examined using HRT3 and Stratus OCT on the same day within 30 minutes. This study included 18 patients (23 eyes) with age-related maculopathy (AMD), 4 patients (6 eyes) with diabetic macular edema(DME), 4 patients (4 eyes) with other retinal disease causing subretinal fluid, and 10 normal subjects (16 eyes) without macular abnormalities. AMD included CNV (n=16), dry AMD with extensive drusen (n=4), retinal pigment epithelial detachment (n=2) and geographic atrophy (n=1). The macular thickness and volume were evaluated using the retina module of the HRT3, and compared with the corresponding macular thickness and volume determined by Stratus OCT. The HRT3 software employs an estimation of the eye’s point spread function to calculate retinal thickness using maximum likelihood estimation.
In normal eyes, the mean macular volume and thickness were 2.50±0.22 mm3 and 215±41 µm for HRT vs 2.45±0.06 mm3 and 214±16 µm for OCT. The two instruments were in good agreement and statistically no difference (p>0.33 and p>0.89). Similarly in DME, the two instruments correlated well: the mean macular volume and thickness were 3.12±0.79 mm3 and 316±111 µm for HRT vs 2.83±0.36 mm3 and 311±72.9 µm for OCT (p>0.35 and p>0.8). In AMD, the mean macular volume and thickness were 3.28±0.59 mm3 and 370±84.3 µm for HRT vs 2.26±0.41 mm3 and 206±64.7 µm for OCT. Thus HRT overestimated macular volume and thickness by 1.0 mm3 and 164 µm respectively (p<0.0001, p<0.0001). Other retinal diseases will be discussed.
This study has shown that confocal SLO topographic scanning and analysis using a novel HRT3 algorithm can be used to measure retinal thickness and volume. No significant difference between HRT3 and OCT parameters was found in DME and normal eyes. Larger volumetric and thickness measurements were found with HRT3 especially in the eyes with neovascular AMD. This discrepancy may be based on the nature of the HRT3 algorithm that measures both retinal and subretinal thickness as opposed to OCT whose automated thickness and volume algorithm does not typically measure subretinal and sub-RPE pathology.
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