Light Disturbance Analyzer
This device analyses the size and shape of the halo/glare/disturbance surrounding a bright light against a dark background under dim illumination conditions.
The test consisted to identify a peripheral stimulus around a central LED stimulus. The subject was collocated at a distance of two meters from the centre of the central LED stimulus under low illumination surrounding conditions. The test was repeated for various semi meridians. At the end of the test, it was obtained a map of the size of the light disturbance (halo). The subject had to continuously maintain the fixation on the central LED stimulus.
The hardware contains an electronic board with a central larger LED source of bright light (2800 cd/m2) acting as a source of glare/disturbance surrounded by 240 small LEDs (6 cd/m2) acting as detection stimuli.
The software evaluates different indexes: Light Disturbance Index (LDI, %), Best fit Circle Irregularity (BFC Irreg, mm) and Best Fit Circle Irregularity Standard Deviation (BFC Irreg SD, mm). The LDI is the main parameter and is calculated as the ratio of the area of the points missed by the subject: the higher the LDI, the higher the light disturbance induced by the central source of light and the lower the ability to discriminate surrounding small stimuli. The Best Fit Circle Radius (BFCRadius) corresponds to the circle that best fits the distortion area. This area is delimited by all the external points not seen by the subject along each meridian. The irregularity of this distortion area obtained by the BFCRadius is called BFC Irregularity (BFC Irreg). The standard deviation of BFC Irreg called BFC Irreg SD determines how asymmetric the distortion area limited from a perfectly circular shape is.
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Fernandes P, Amorim-de-Sousa A, Queirós A, Escandón-Garcia S, McAlinden C, González-Méijome JM. Light disturbance with multifocal contact lens and monovision for presbyopia [published online ahead of print, 2018 Mar 22]. Cont Lens Anterior Eye. 2018;S1367-0484(17)30409-5. doi:10.1016/j.clae.2018.03.006
Santolaria-Sanz E, Cerviño A, González-Méijome JM. Corneal Aberrations, Contrast Sensitivity, and Light Distortion in Orthokeratology Patients: 1-Year Results. J Ophthalmol. 2016;2016:8453462. doi:10.1155/2016/8453462
Ferreira-Neves H, Macedo-de-Araújo R, Rico-Del-Viejo L, da-Silva AC, Queirós A, González-Méijome JM. Validation of a method to measure light distortion surrounding a source of glare. J Biomed Opt. 2015;20(7):75002. doi:10.1117/1.JBO.20.7.075002
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Santolaria Sanz E, Cerviño A, Queiros A, Villa-Collar C, Lopes-Ferreira D, González-Méijome JM. Short-term changes in light distortion in orthokeratology subjects [published correction appears in Biomed Res Int. 2015;2015:458706]. Biomed Res Int. 2015;2015:278425. doi:10.1155/2015/278425