Three pieces of paper tend to leave people confused after an eye appointment: the prescription, the summary of findings, and whatever the insurance sends weeks later. All three are written in shorthand that nobody explains.
Below are the terms that actually turn up on those documents, grouped the way you meet them rather than alphabetically. Knowing what a word means will help you ask a better question at your next visit.
The shorthand on your glasses prescription
A prescription is a set of measurements, not a grade. Higher numbers mean more correction, not worse eyes.
- OD and OS mean right eye and left eye. OU means both.
- Sphere (SPH) is the main strength. A minus number corrects nearsightedness, a plus number corrects farsightedness.
- Diopter (D) is the unit those numbers are measured in.
- Cylinder (CYL) and axis describe astigmatism: how much extra correction is needed, and at what angle. Axis runs from 1 to 180 and is a direction, not a strength.
- Add is the extra reading power in bifocals, progressives, or reading glasses. It is usually the same in both eyes.
- Prism and base appear when the eyes need help lining up together.
- PD is pupillary distance, the space between your pupils, used to center the lenses.
- Plano or PL means no correction is needed in that spot. DS means sphere only, with no astigmatism correction.
Contact lens prescriptions add a few more
A contact lens prescription is a different document from a glasses prescription and cannot be swapped for it. It includes base curve (BC), the curvature of the lens, and diameter (DIA), its width, plus a specific brand and material because a contact lens sits on the eye and the fit matters. Toric lenses correct astigmatism, multifocal lenses handle near and distance, and most prescriptions carry an expiration date.
Words from the exam itself
- Visual acuity is the sharpness measurement written as 20/20, 20/40, and so on. The second number is the distance at which someone with typical vision could read the same line.
- Refraction is the part of the exam where you compare lens options and the doctor settles on your prescription.
- Dilation means drops widen the pupil so the retina can be examined. Cycloplegic drops also relax focusing, which is common when testing children.
- Tonometry measures eye pressure, reported as IOP, intraocular pressure.
- Slit lamp is the microscope used to examine the front of the eye. Fundus refers to the back of the eye, including the retina and optic nerve.
- Cup-to-disc ratio describes the shape of the optic nerve head, tracked over time in glaucoma monitoring.
- OCT is a scan that images the layers of the retina. Visual field testing maps your side vision.
Condition names you may hear
The four refractive errors are myopia (nearsightedness), hyperopia (farsightedness), astigmatism (an unevenly curved cornea or lens), and presbyopia (the age-related loss of close focus). Emmetropia means no refractive error at all.
Beyond those, the names that come up most often include cataract, clouding of the eye's natural lens; glaucoma, damage to the optic nerve often linked to pressure; macular degeneration, changes in the central retina with age; and diabetic retinopathy, damage to retinal blood vessels from diabetes.
Surface and lid conditions have their own vocabulary. Dry eye covers a range of tear film problems, often involving meibomian gland dysfunction, the oil glands in the lids. Blepharitis is lid margin inflammation, conjunctivitis is inflammation of the clear membrane over the white of the eye, and keratitis is inflammation of the cornea.
Two terms sound frightening but usually are not. Floaters are the specks that drift across your vision. Posterior vitreous detachment is a common age-related change in the gel inside the eye. Both can be normal, but a sudden increase in floaters, new flashes of light, or a shadow moving across your vision needs same-day attention, as does sudden vision loss, real eye pain, or any chemical splash or injury.
Lens and correction vocabulary
These are the words that come up while you are choosing eyewear, when the price starts to move.
- Single vision lenses have one power throughout. Bifocal lenses have two zones with a visible line. Progressive lenses blend distance to near with no line.
- High index means a denser lens material that makes strong prescriptions thinner.
- Polycarbonate and trivex are impact-resistant materials, commonly recommended for children and sports.
- Anti-reflective coating cuts reflections off the lens surface, which helps with night driving and screen glare.
- Photochromic lenses darken in sunlight. Polarized lenses cut glare off flat surfaces like water and roads.
Insurance and billing words
This is where most of the confusion lives, because vision plans and health insurance cover the same visit in different ways.
- A routine exam checks vision and eye health with no complaint driving it, and usually goes through a vision plan. A medical exam addresses a problem such as dry eye or diabetes monitoring, and usually goes through health insurance.
- Copay is your fixed share at the visit. Deductible is what you pay before coverage starts, and coinsurance is a percentage you owe after that.
- Allowance is a dollar amount your plan puts toward frames or contacts. Anything above it is yours to pay.
- In network providers have a contract with your plan. Out of network usually means paying up front and filing for partial reimbursement.
- Benefit period or frequency is how often the plan will pay again, often every 12 or 24 months.
- A refraction fee is a separate charge some offices bill for determining your prescription, because certain plans do not cover it.
- An EOB, or explanation of benefits, is a summary of what was billed and paid. It is not a bill.
Common questions
Why is my prescription different at a new office?
Small differences are normal, since refraction involves your responses and slightly different technique. A large jump is worth asking about directly.
Does 20/20 mean my eyes are healthy?
No. It measures sharpness at distance on a chart. Pressure, the retina, and the optic nerve are checked separately, and several serious conditions start with no change in acuity.
Why was I charged when my exam was covered?
Usually a refraction fee, a materials charge above your allowance, or a visit that was billed as medical rather than routine. The office can tell you which.
Take your paperwork to your next appointment and ask about anything you cannot decode. If you would rather start with an office that already takes your coverage, you can match your vision plan to eye doctors in your area.