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Validation of a new clinical system for the fast measure of defocus curves with iPad

Poster Details

First Author: M.Rodriguez Vallejo SPAIN

Co Author(s):    A. Tauste   C. Albarran   I. Basterra   D. Pinero   J. Fernandez        

Abstract Details


To validate a new iPad application (App) for the automated measure of Visual Acuity (VADC) and Contrast Sensitivity (CSDC) defocus curves, which halves the time required for measuring a defocus curve.


Qvision, Ophthalmology Department Vithas Virgen del Mar Hospital


59 eyes/subjects implanted with bifocal and trifocal intraocular lenses were measured at far vision with an ETDRS chart for visual acuity and with a test for measuring contrast sensitivity function (CSF) at 3, 6, 12 and 18 cycles per degree (cpd). Defocus curves were later measured with the App from �.00 D to -4.00 D, in -0.50D steps. The VADC consisted of a crowded Snellen E which changed its size in 0.1 logMAR steps and the CSDC was based on the same optotype which changed its contrast in 0.1 log units, maintaining the size constant (0.3 logMAR).


A mean difference of 0.007 [Limits of Agreement (LoAs), 0.16] was obtained between the App and the ETDRS, the 96.6% of eyes differing in less of 1 line. The mean difference between the App and the CSF test varied depending on the spatial frequency: -0.91 [LoAs, 0.44] for 3 cpd; -0.97 [LoAs, 0.44] for 6 cpd; -0.64 [LoAs, 0.53] for 12 cpd; and -0.22 [LoAs, 0.53] for 18 cpd. The correlation between the tests difference for contrast sensitivity and the spatial frequency was fitted to a power function (r-square: 0.6). Estimated best correlated spatial frequency was 20 cpd.


The new App for measuring VADC with an automated procedure showed a good agreement with the conventional measure of visual acuity through the gold standard (ETDRS). The CSDC underestimated the contrast sensitivity in comparison to all the measured spatial frequencies with sinusoidal gratings. Our study predicted that for a particular optotype size of 0.3 logMAR, the best agreement would be obtained for a spatial frequency of 20 cpd (70 lp/mm) instead of the theoretical 15 cpd (50 lp/mm).

Financial Disclosure:

gains financially from product or procedure presented

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