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Eon Kim, Ravi C Bakaraju, Indrani Perera, Brien A Holden, Klaus Ehrmann; Power profiles measured on NIMO TR1504 (Lambda-X): repeatability and effects of lens decentration for single vision, bifocal and multifocal contact lenses.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):6072.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the repeatability of NIMO TR1504 (Lambda-X, Belgium) and investigate the effects of lens decentration on the measured power profiles for single vision (SV), bifocal (BF) and multifocal (MF) contact lenses.
Six types of contact lenses: Acuvue Advance SV, Clariti SV, Focus Night&Day SV, Acuvue BF, MiSight and PureVision MF (three lenses each) were measured five times using NIMO to calculate coefficient of repeatability (COR) of the instrument. The COR of each lens type was calculated and compared between SV, BF and MF, for different prescription powers (-6.00D, -1.00D and +1.00D) including high (+2.5D) and low (+1.5D) add for MF and BFs. One lens from each type was measured with a deliberate decentration up to ±0.5 mm in 0.1 mm steps.
The COR varied between 0.04 and 0.61D across the half chord of the optic zone. COR for the SV group was significantly lower compared to the BF/MF groups (p < 0.001). The COR for high minus (-6.00D) lenses measured significantly higher compared to other power lenses (p < 0.001). The COR for high adds measured significantly higher than low adds (p < 0.001). The shape of the measured power profiles were not affected when the lenses were deliberately decentered for all SV and PureVision MF. For Acuvue BF and MiSight lenses however, the shape of the measured power profiles flattened up to 1.00D.
The COR of NIMO across the half chord of the optic zone diameter were mostly within clinical relevance of ±0.25D for power measurements. The COR measures were dependent on the lens type, with BF/MFs producing higher COR than SV lenses. The effect of deliberate decentration on shape of measured power profiles was pronounced for BF/MF lenses where the profiles had a sharp transition of power.
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