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JAMA Ophthalmol. 2017 Jun 1;135(6):651-653. doi: 10.1001/jamaophthalmol.2017.0932.

Visual Acuity Reporting in Clinical Research Publications.

Author information

Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland2Editor, JAMA Ophthalmology.



Visual acuity results in publications typically are reported in Snellen or non-Snellen formats or both. A study in 2011 suggested that many ophthalmologists do not understand non-Snellen formats, such as logarithm of the Minimum Angle of Resolution (logMAR) or Early Treatment Diabetic Retinopathy Study (ETDRS) letter scores. As a result, some journals, since at least 2013, have instructed authors to provide approximate Snellen equivalents next to non-Snellen visual acuity values.


To evaluate how authors currently report visual acuity and whether they provide Snellen equivalents when their reports include non-Snellen formats.


From November 21, 2016, through December 14, 2016, one reviewer evaluated visual acuity reporting among all articles published in 4 ophthalmology clinical journals from November 2015 through October 2016, including 3 of 4 journals that instructed authors to provide Snellen equivalents for visual acuity reported in non-Snellen formats.

Main Outcomes and Measures:

Frequency of formats of visual acuity reporting and frequency of providing Snellen equivalents when non-Snellen formats are given.


The 4 journals reviewed had the second, fourth, fifth, and ninth highest impact factors for ophthalmology journals in 2015. Of 1881 articles reviewed, 807 (42.9%) provided a visual acuity measurement. Of these, 396 (49.1%) used only a Snellen format; 411 (50.9%) used a non-Snellen format. Among those using a non-Snellen format, 145 (35.3%) provided a Snellen equivalent while 266 (64.7%) provided only a non-Snellen format.

Conclusions and Relevance:

More than half of all articles in 4 ophthalmology clinical journals fail to provide a Snellen equivalent when visual acuity is not in a Snellen format. Since many US ophthalmologists may not comprehend non-Snellen formats easily, these data suggest that editors and publishing staff should encourage authors to provide Snellen equivalents whenever visual acuity data are reported in a non-Snellen format to improve ease of understanding visual acuity measurements.

[Indexed for MEDLINE]
Free PMC Article

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