Documenting visual acuity follows a specific format: you record the eye tested, whether correction was worn, the chart used, and the smallest line the patient could read. A properly written entry looks something like “ccOD 20/30,” meaning the right eye sees 20/30 with corrective lenses. Getting each piece right matters for tracking changes over time and communicating clearly across providers.
The Standard Testing Setup
Distance visual acuity is tested at 20 feet (6 meters) using a Snellen chart or similar optotype chart. If your exam room is shorter than 20 feet, projecting the chart onto a mirror can simulate the correct distance. The chart needs adequate illumination, ideally between 80 and 320 candelas per square meter, which translates to a well-lit room without glare on the chart surface.
Test one eye at a time, starting with the worse eye while the better eye is fully covered. Ask the patient to read from the top line down. The smallest line they can read is their visual acuity for that eye. Then repeat with the other eye.
Abbreviations You Need to Know
Every visual acuity entry uses a set of standard abbreviations:
- OD: right eye (from the Latin “oculus dexter”)
- OS: left eye (“oculus sinister”)
- OU: both eyes together
- CC: with correction (glasses or contacts worn during testing)
- SC: without correction
- PH: pinhole
These abbreviations combine into a single compact entry. For example, “scOS 20/40” means the left eye tested at 20/40 without glasses. “ccOU 20/20” means both eyes together measured 20/20 while wearing corrective lenses. Always specify whether the patient was tested with or without their correction, because the distinction changes how the result is interpreted.
Recording Partial Lines
Patients often read most of a line but miss a letter or two, or they get a couple of letters on the next smaller line. You document this with plus and minus notation. If someone reads the 20/30 line but misses two letters, you write “20/30-2.” If they read all of the 20/30 line and get one letter on the 20/25 line, you write “20/25+1.” The base fraction is always the smallest line where the patient read the majority of letters, and the plus or minus indicates how many they got beyond that line or missed on it.
When to Use a Pinhole
If a patient’s acuity is reduced and they aren’t wearing glasses, testing through a pinhole occluder helps determine whether the problem is refractive (fixable with lenses) or something else. The pinhole blocks scattered light and mimics the effect of a corrective lens. If acuity improves with the pinhole, the deficit is likely refractive. If it doesn’t improve, the cause may be a problem with the eye itself.
Document pinhole results with “PH” in your notation. For example, “phOD 20/25” means the right eye tested at 20/25 through a pinhole. Keep in mind that pinhole testing has more variability than a formal refraction, so it works as a screening tool rather than a precise measurement of best-corrected vision.
Documenting Near Vision
Near visual acuity is tested at a working distance of 16 inches (40 centimeters). The preferred way to record it uses M-units rather than the older Jaeger (J-number) system, which lacks standardization across card manufacturers. A near acuity entry looks like “1.25M @ 40cm,” specifying both the letter size and the distance at which it was read.
If the patient holds the card at a distance other than the standard 16 inches, always document the actual working distance. Writing “1.0M @ 30cm” tells the next provider that the patient pulled the card closer, which changes the clinical meaning of the result.
Snellen, LogMAR, and Metric Notation
The Snellen fraction (20/20, 20/40, etc.) is the most familiar format in the United States. The top number is the testing distance in feet. The bottom number is the distance at which a person with normal vision could read that same line. So 20/40 means you need to be at 20 feet to read what someone with normal vision reads at 40 feet.
Outside the U.S., metric notation is common: 6/6 replaces 20/20, since the testing distance is 6 meters instead of 20 feet. LogMAR notation expresses acuity on a logarithmic scale and is preferred in research because it allows cleaner statistical analysis. On the LogMAR scale, 0.00 equals 20/20, higher numbers indicate worse vision (1.0 equals 20/200), and negative numbers indicate better-than-average vision (-0.10 equals 20/16). Some common conversions:
- LogMAR 0.00: 20/20 (normal acuity)
- LogMAR 0.30: 20/40
- LogMAR 0.50: 20/63
- LogMAR 1.00: 20/200 (legal blindness threshold in the U.S.)
Whichever format you use, note the type of chart (Snellen, ETDRS/LogMAR) in your documentation. Results aren’t perfectly interchangeable between chart designs because letter spacing and sizing progression differ.
Recording Very Low Vision
When a patient can’t read any line on the chart, you switch to a descending hierarchy of tests, each documented with its own abbreviation:
- CF (counting fingers): hold up fingers at a measured distance and ask the patient to count them. Record as “CF @ 3ft” or whatever distance they succeed at.
- HM (hand motion): the patient can detect a hand moving in front of them but cannot count fingers.
- LP (light perception): the patient can tell when a light is on or off but cannot see hand motion. Note whether the patient can identify the direction the light comes from, sometimes written as “LP with projection.”
- NLP (no light perception): the patient cannot detect light at all.
This hierarchy matters because it captures meaningful differences in residual vision. A patient with CF at 4 feet has significantly more functional sight than one with LP only, and that distinction affects clinical decisions.
Charts for Children and Non-Verbal Patients
Standard letter charts don’t work for young children or patients who can’t identify the alphabet. Several alternatives exist, each suited to a specific age range:
- LEA Symbols: uses simple shapes (circle, square, house, apple) that children match to a card. Designed for ages 2 to 4.
- Allen Cards: flash cards with schematic figures identified from various distances. Also for ages 2 to 4.
- HOTV test: uses only the letters H, O, T, and V, which children can match even if they don’t know the full alphabet. Suited for children older than 4.
- Tumbling E: shows the letter E rotated in four directions, and the patient points the direction the “arms” face. Works for ages 4 and up, including adults who are illiterate or unfamiliar with the Latin alphabet.
When documenting acuity from any of these charts, always note which chart was used. Writing “20/30 (LEA Symbols)” tells the reader that the result came from a symbol-matching test rather than a standard letter chart, which is important context for comparing measurements over time.
Putting a Full Entry Together
A complete visual acuity record includes the correction status, the eye, the result, and the chart type. A thorough chart note might look like this:
- scOD 20/40-1 (Snellen)
- scOS 20/30 (Snellen)
- phOD 20/25 (Snellen)
- ccOU 20/20 (Snellen)
- Near: 1.0M @ 40cm OU
This tells any provider exactly what was tested, under what conditions, and with what result. If you document acuity this way consistently, the record becomes a reliable baseline for detecting changes at future visits.