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Daniel Martins Rocha, Solange Rios Salomao, Sung Eun Song Watanabe, Josenilson M Pereira, Paula Y Sacai, Adriana Berezovsky; FREQUENCY AND CAUSES OF NEGATIVE ELECTRORETINOGRAM OVER A 10-YEAR PERIOD IN A UNIVERSITY HOSPITAL IN BRAZIL. Invest. Ophthalmol. Vis. Sci. 2014;55(13):343.
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© ARVO (1962-2015); The Authors (2016-present)
To provide an overview of the frequency and causes of negative electroretinograms (ERGs) over a 10-year period in a University Hospital in Brazil.
A retrospective review was performed of all full-field ERGs performed from March 2004 to November 2013 under ISCEV standard conditions in the Laboratory of Clinical Electrophysiology of Vision, Hospital Sao Paulo, Brazil. All participants had their monocular visual acuity (VA) measured using the ETDRS chart. Negative ERG was defined as a waveform evoked by a bright flash under scotopic conditions with a larger a-wave than b-wave resulting in a b/a ratio below 1.0 in at least one eye. Clinical information as age, gender, presenting VA, history of consanguinity and diagnosis were considered.
A total of 1645 patients had both eyes tested during the study period, with 41 (2.49%) showing negative ERG. Ages ranged from 0.5-78 years (mean=33.8±20.7; median=32); 22 (54%) males and 19 (46%) females. Negative ERGs were found in 14 children (5 females and 9 males) and 27 adults (14 females and 13 males). Frequencies of negative ERG were 1.64% for adults and 0.85% for children (< 18 years of age). Bilateral negative ERG was found in 27 (66%) patients and unilateral in 14 (34%). The most common diseases associated with bilateral negative ERGs were photoreceptor dystrophies (n=17), X-linked juvenile retinoschisis (n=3), congenital stationary night blindness (n=1), inflammatory eye diseases (n=1), diabetic retinopathy (n=1) and undetermined (n=4). In unilateral cases the main causes were photoreceptor dystrophies (n=7), inflammatory eye diseases (n=4), diabetic retinopathy (n=1) and undetermined (n=2). History of consanguinity was found in 9 (23.1%) patients, with two with unilateral negative ERGs. Mean VA in the better-seeing eye was 0.55 ±0.55 logMAR (20/70) and 0.88±0.69 logMAR (20/150) in the worse-seeing eye.
The frequency of negative ERGs over a 10-year period from a large university public hospital in Brazil, was marginally below the 3-5% range described in the literature. A possible factor contributing to this result is the unavailability of ERGs under sedation in our service decreasing the number of young children tested. Predominantly male children showed negative ERGs. The most likely diagnosis for both bilateral and unilateral cases was photoreceptor dystrophies (rod-cone and cone-rod).
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