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Mohammed A. Khan, Francis C. DeCroos, Carl D. Regillo, Julia A. Haller, David S. Boyer; Visual Acuity Agreement Between The Standard Early Treatment of Diabetic Retinopathy Study (ETDRS) Chart And A Hand Held Illuminated ETDRS Equivalent Chart In Eyes With Retinal Disease. Invest. Ophthalmol. Vis. Sci. 2012;53(14):985.
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Accurate, reproducible measurement of visual acuity is of central importance in clinical studies exploring retinal disease. The Early Treatment of Diabetic Retinopathy Study (ETDRS) chart is considered the gold standard for measurement of visual acuity in such investigations, however various limitations prevent universal utilization. This study characterized agreement in visual acuity measurement between a handheld internally illuminated ETDRS (RAM-EDTRS) chart and a standard back illuminated EDTRS chart.
Visual acuity in patients with various retinal diseases were prospectively measured using both the ETDRS chart and the RAM-ETDRS chart after best protocol refraction. The main outcome measured was agreement between RAM-EDTRS and ETDRS visual acuity as measured in individual letter units. Visual acuity measurements were performed in the same room by a trained refractionist. ETDRS visual acuity, RAM-ETDRS visual acuity, age, gender, race, eye involved, lens status and clinical diagnosis were recorded. Inclusion criteria include age greater than 18 years and clinical diagnosis of retinal disease in at least one eye. Exclusion criteria include significant cataract, posterior capsular opacity, or uveitis.
ETDRS and RAM-ETDRS visual acuities of 39 eyes of 20 patients were compared. Acuities ranged from 20/20 (55 letters) to 20/200 (5 letters), with the mean number of letters seen found to be 41.8 (standard deviation or SD = 13.6 letters) and 41.8 letters (SD = 13.2 letters) for the ETDRS chart and RAM-ETDRS chart, respectively. The total number of letters seen was 1626 for the ETDRS chart and 1629 for the RAM-ETDRS chart, with mean difference per eye between the ETDRS and RAM-ETDRS chart found to be 2.6 letters (SD = 2.5 letters). Paired Student’s t test revealed no significant difference between ETDRS and RAM-ETDRS chart acuities (p=0.965). Correlation coefficient (r) of 0.963 demonstrated a strong positive linear correlation between ETDRS chart and RAM-EDTRS chart acuities.
We observed a strong positive correlation between visual acuity obtained by the standard ETDRS chart and the RAM-ETDRS chart in patients with retinal pathology. Measurement of visual acuity with the RAM-ETDRS chart may serve as useful tool in future clinical studies of retinal disease.
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