Skip to Main Content

We have a new app!

Take the Access library with you wherever you go—easy access to books, videos, images, podcasts, personalized features, and more.

Download the Access App here: iOS and Android. Learn more here!

Abbreviations and symbols commonly used in ophthalmology are listed in the accompanying box.

|Download (.pdf)|Print
Abbreviations & Symbols Used in Ophthalmology
A or Acc Accommodation
Ax or x Axis of cylindric lens
BI or BO Base-in or base-out (prism)
CF Counting fingers
Cyl Cylindric lens or cylinder
D Diopter (lens strength)
E Esophoria (latent convergent squint)
EOG Electro-oculography
EOM Extraocular muscles or movements
ERG Electroretinography
ET Esotropia (manifest convergent squint)
H Hyperphoria (latent vertical squint)
HM Hand movements
HT Hypertropia (manifest vertical squint)
IOP Intraocular pressure
IPD Interpupillary distance
J1–J20 Test types (Jaeger) for testing near vision
KP Keratic precipitate
LogMAR Logarithm of minimum angle of resolution (scale for testing visual acuity)
LP Light perception
L Proj Light projection
N5-N48 Test types (Faculty of Ophthalmologists) for testing near vision, equivalent to printer's points
NLP No light perception
NPC Near point of convergence
OD (R, or RE) Oculus dexter (right eye)
OS (L, or LE) Oculus sinister (left eye)
OU Oculi unitas (both eyes)
PD Prism diopter (strength)
PH Pinhole
PRRE Pupils round, regular, and equal
S or Sph Spherical lens
VA Visual acuity
VER Visual evoked response
X Exophoria (latent divergent squint)
XT Exotropia (manifest divergent squint)
+ Plus (convex) lens
Minus (concave) lens
Infinity (6 meters [20 feet] or more distance)
° Degree (measurement of strabismus angle)
Δ Prism diopter (PD)


Corrected (with glasses, contact lens, or pinhole) distance visual acuity should be tested for each eye in turn, using a Snellen or logMAR (EDTRS) chart. Snellen visual acuity is traditionally measured at 20 feet (6 meters in Europe) or nearer if vision is poor. LogMAR acuity is tested at 13 feet (4 meters), 10 feet (3 meters), or 3 feet (1 meter) when accuracy of test distance and provision of (1 D) refractive correction for presbyopic patients become important. Snellen visual acuity is expressed as a fraction—the test distance over the figure, determined by the distance at which the respective line can be read by a normal individual, assigned to the lowest line the patient can read. If the patient is unable to read the top line even when standing close to the chart, acuity is categorized as counting fingers (CF), hand movements (HM), perception of light (LP), or no light perception (NLP). In general, corrected acuity less than 20/30 (6/9, 0.67) is abnormal but 20/20 (6/6, 1.0) may be abnormal, especially if reduced in comparison to the other eye. LogMAR acuity, which increases as vision deteriorates, is recorded as the total of the values, determined by their size, of all the letters correctly identified with 0.00 being equivalent to 20/20 (6/6, 1.0) and 1.00 being equivalent to 20/200 (6/60, 0.1). For the Visual Acuity Rating (VAR), which decreases as vision deteriorates, each letter identified correctly scores 1, from a baseline of 20/2000 (6/600, 0.01) such that 50 is equivalent to ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.