Distance doubling visual acuity test: a reliable test for nonorganic visual loss.

Background: To determine the value of the distance doubling visual acuity test in the diagnosis of nonorganic visual loss in a comparative observational case series.

Methods: Twenty-one consecutive patients with nonorganic visual acuity loss and 21 subjects with organic visual loss as controls were included. Best corrected visual acuity was tested at the normal distance of 5 meters using Landolt Cs. The patient was then repositioned and best corrected visual acuity was tested with the previous optotypes at double the distance via a mirror.

Results: Nonorganic visual acuity loss was identified in 21 of 21 patients. Sensitivity and specificity of distance-doubling visual acuity test in functional visual loss were found to be 100% (CI; 83%-100%) and 100% (CI; 82%-100%), respectively.

Conclusion: Distance doubling visual acuity test is widely used to detect nonorganic visual loss. Our results show that this test has a high specificity and sensitivity to detect nonorganic visual impairment.