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G.M. Saleh, R.J. Allen, D.W. DeWit; An electromagnetic characterization of cellular phone interference with ophthalmic equipment and its clinical implications . Invest. Ophthalmol. Vis. Sci. 2004;45(13):5609.
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Purpose:Many hospitals have restrictive policies with respect to cellular phone usage on site. This study aims to identify and quantify the degree of interference cellular phones inflict on ophthalmic equipment and assess its clinical relevance. Methods:The investigation was performed based on the UK Medical Devices Agency electromagnetic compatibility testing protocol for medical devices. Evaluation of cellular phone interference was performed at 10 different distances (0m to 2m) and three settings (standby, connected call and ringing/dialing), with field strength quantification of each of these combinations determined using a spectrum analyzer. Two cellular phones, operating at 900MHz and 1800MHz carrier frequencies, were used to test the following ophthalmic equipment: Argon & YAG lasers, separate A & B scanners, Humphreys & Henson Field Analyzers and a Pneumotonometer, whilst each device was on standby then operational. Results:The field strength emitted by the phones (in milli Watts of peak power above background random noise) ranged from 10.18mW to 243.82mW. Interference was only demonstrated with two pieces of equipment. First, the B scanner (Ultravision) showed horizontal banding on the display screen at 0m test distance (phones touching scanner), with both the 900MHz and 1800MHz frequencies, present only in the dialing and connected (not standby) modes. Second, the YAG laser (Alcon YAG 2500) emitted a buzzing sound when the 900MHz phone was within 10cm in connected and dialing modes. The 1800MHz phone did not cause any problems with this device. There was no evidence that the interference induced any clinically significant malfunctioning whilst the devices were operational. Conclusions:Cellular phone usage around ophthalmic equipment appears to be relatively safe with interference only occurring at <10cm on two machines and even then being of no detectable clinical significance.
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