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Christopher M Pruet, Kanwal Matharu, Alice Chuang, Gene Kim; A Comparison of the Casia SS-1000 Keratometry and Atlas 9000 SimK Topography Values. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1625.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the agreement of keratometry measured by the CASIA SS-1000 Anterior Segment Ocular Coherence Tomography (ASOCT; Tomey, Nagoya, Japan) with SimK values measured by Atlas 9000 (Carl Zeiss Meditec, Dublin, CA).
: A retrospective chart review was performed of patients who had undergone both ASOCT 'Corneal Map' mode imaging and ATLAS topography. Eyes were excluded if they had anterior segment abnormalities precluding topography measurements. If both eyes were eligible, one eye was randomly selected. Demographics were recorded. Eyes were classified into three groups based on the ocular history: eyes without corneal diseases (group 1), eyes with keratoconus (KCN) or pellucid marginal degeneration (PMD) (group 2), and eyes with prior corneal surgery (group 3). Bland-Altman agreement plot was used to evaluate the mean difference between ASOCT and Atlas and limits of agreement.
Seventy-one eyes were included. The mean age was 46.8 (± 19.1) years with 31 (43.7%) male, 35 (49.3%) White, 18 (25.4%) Black and 10 (14.1%) Hispanics and 36 (50.7%) right eyes. Seventeen eyes (23.9%) were in group 1, 29 (40.8%) in group 2 and 25 (35.2%) in group 3. Previous corneal surgeries included 7 (9.9%) Descemet’s stripping automated endothelial keratoplasty (DSAEK), 16 (22.5%) full thickness penetrating keratoplasty (PKP), and 2 (2.8%) LASIK. Figure 1 showed Atlas keratometry readings average 0.19 D lower, 0.60D lower, and 1.62D higher for the steep measurements in groups 1, 2, and 3 respectively,and 0.14 D lower, 0.11 lower, 0.73 D lower for groups 1, 2, and 3 for flat measurements. The limits of agreement showed a 95% variation within 1.85D, 4.7D and 12.02 D on steep keratometry for groups 1, 2, and 3 respectively, and 2.15 D, 3.00 D, and 10.91 D on flat keratometry for groups 1, 2, and 3 respectively.
There is generally good agreement between the Casia SS-1000 and the Atlas 9000 topographies when eyes are without prior surgery or ectatic disease. Agreement between the devices decreased somewhat with ectasic disease and substantially with prior corneal surgery.
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