Reading Your Eye Examination Report: Refraction Numbers, Pressure and Retinal Images

The envelope from the optician arrives, and inside is a sheet that looks like a flight manifest: a grid of plus and minus signs, decimals to two places, the word AXIS beside a number that could be a compass bearing. Somewhere lower down, a line reads “IOP 17/18” and, stapled behind it, a glossy orange disc that is apparently the inside of your eye. You were told everything looked “fine.” You would like to know what fine means.

This is the guide to getting your eye exam results explained without a second appointment. It walks through the refraction numbers, the pressure reading and the retinal images in the order they appear on most reports, and it is honest about what each figure can and cannot tell you.

One caution before the decoding begins. A report is a snapshot taken by a trained person on a particular afternoon. The numbers matter; the trend across years, and the judgment of the clinician who took them, matter more.

What actually happens during an eye examination, step by step

Most routine examinations follow a similar rhythm, even though the equipment varies. The visit starts with history: what you notice, what medicines you take, whether anyone in your family has glaucoma, diabetes or macular degeneration. That conversation shapes everything that follows, so it is worth arriving with answers.

Next comes visual acuity, the letter chart. It measures the smallest detail your eye can resolve at a set distance, with and without your current glasses. Then refraction, the part where lenses are flipped in front of your eyes and you are asked “better one, or two?” Many clinics first use an autorefractor, a machine that estimates your prescription by bouncing light off the retina, and then a clinician refines the estimate by hand. According to MedlinePlus, a standard ophthalmic examination also checks eye movements, pupil responses and how the two eyes work together.

Eye pressure is measured either with a puff of air or with a small probe that briefly touches a numbed cornea. The clinician then looks inside the eye, often after dilating drops widen the pupil so the retina can be seen in full. Photographs or a scan may replace or supplement that direct look.

The Mayo Clinic describes a comprehensive exam as taking roughly an hour, though a simple glasses check can be far shorter. Every one of those steps produces a number or an image, and every number lands on the report you are now holding. The rest of this article follows them in that order.

How to read eye prescription lines: SPH, CYL and AXIS in plain language

The refraction block is the part most people stare at longest. It is organized by eye, and the abbreviations are Latin: OD (oculus dexter) is your right eye, OS (oculus sinister) your left, OU both. Some reports simply print R and L.

SPH, short for sphere, is the main lens power your eye needs, measured in diopters. A diopter is a unit of lens strength: a one-diopter lens brings parallel light to a focus one meter away. A minus sign means you are nearsighted, or myopic: distant objects blur because your eye focuses light in front of the retina. A plus sign means farsighted, or hyperopic: the focus falls behind the retina. The National Eye Institute explains these refractive errors as the most common vision problems worldwide.

CYL, for cylinder, records astigmatism. Astigmatism means the cornea or lens is curved more steeply in one direction than another, like the back of a spoon rather than a ball, so light focuses on two lines instead of one point. The CYL number is the extra power needed to correct that difference. If the box is blank or reads “DS” or “sphere,” you have no measurable astigmatism.

AXIS only appears when CYL does. It is an angle from 1 to 180 degrees telling the lab which way to orient the cylinder correction. It is not a power at all, so a high axis number is not “worse” than a low one. A prescription reading -2.00 -0.75 x 180 means two diopters of nearsightedness plus three-quarters of a diopter of astigmatism oriented horizontally. Read it as a shape, not a score.

What does +2.75 mean on an eye prescription?

A sphere of +2.75 means your eye needs 2.75 diopters of converging (plus) power to focus clearly. In everyday terms, that is a moderate degree of farsightedness. Whether it troubles you depends heavily on age.

A young eye has a flexible internal lens that can add focusing power on demand, a process called accommodation. Someone in their twenties with +2.75 may read a phone screen comfortably by working the lens harder, at the cost of eye strain or headaches after long tasks. The same number in a person in their late fifties usually means both distance and near vision are blurred without glasses, because the aging lens stiffens and can no longer make up the difference. The National Eye Institute lists this stiffening, presbyopia, as its own category of refractive error.

Plus numbers also appear in a different place on the report: the ADD line. ADD is the extra near-vision power added to the bottom of a bifocal or progressive lens, and it is always plus, typically ranging from about +0.75 to +3.00 depending on age and working distance. Do not confuse an ADD of +2.75 with a sphere of +2.75. The first says your reading segment is strong; the second describes your eye’s basic focus.

There is one more wrinkle. Some clinics write prescriptions in “plus cylinder” and others in “minus cylinder.” The same eye can be described as +2.75 -1.00 x 90 or +1.75 +1.00 x 180. Both are correct; they are two ways of writing one shape. If a new report seems to disagree with an old one, ask whether the notation changed before assuming your eyes did.

ADD, PD, prism and the small print at the bottom

Below the three main columns, most reports carry a few extra fields that decide how your glasses are built.

PD is pupillary distance: the space between the centers of your pupils in millimeters. Lens makers use it to place the optical center of each lens directly in front of your eye. It may be written as a single number for distance viewing or as two numbers, one per eye, because faces are rarely symmetrical. A wrong PD is a common reason new glasses feel “off” even when the powers are right.

PRISM and BASE appear only when the two eyes do not point in perfect alignment. A prism lens shifts the image sideways or vertically so the brain can fuse what each eye sees into one picture; BASE (up, down, in, out) describes the direction of that shift. Prism is prescribed after specific alignment testing and is more common in people with double vision or eye-muscle imbalance.

You may also see a note about lens type, tint, or whether the prescription is for distance, near or “intermediate” screen use. An expiry date is standard, because refraction drifts and a stale prescription can be filled with lenses that no longer suit you.

The NHS notes that after a sight test you are entitled to a copy of your prescription. Keep each one. Laid side by side over five or ten years, they show whether your nearsightedness has stopped progressing, whether astigmatism is stable, and how quickly the ADD has climbed. Those trends are often more useful than any single sheet.

What is 20/20 vision, and what is considered a bad vision score?

Visual acuity is written as a fraction. The top number is the testing distance, 20 feet in the United States; the bottom number is the distance at which a person with typical sight could read the same line. Someone with 20/40 vision sees at 20 feet what most people can see from 40. Countries using meters write the equivalent as 6/6 and 6/12. A decimal system (1.0 for 20/20, 0.5 for 20/40) is used in some regions.

So 20/20 is a reference standard, not perfection. Many healthy young adults read 20/15, and a few manage 20/10. Reading 20/25 or 20/30 is common and usually means a small refractive error, a bit of dryness or a smudged lens.

What counts as a “bad” score is really a question about function. Many US states set a driving standard around 20/40 in the better eye with correction, though rules vary. Legal blindness in the United States is defined as best-corrected acuity of 20/200 or worse in the better eye, or a visual field of 20 degrees or less, according to the National Eye Institute.

The phrase best-corrected is doing heavy lifting there. A person who reads 20/200 without glasses but 20/20 with them has a refractive error, not low vision. The number that matters medically is the one measured through the best possible lenses; if that number is reduced, the clinician looks for a cause beyond focus, such as cataract, macular disease or optic nerve damage. Your report may separate the two as “UCVA” (uncorrected) and “BCVA” (best-corrected).

What does 5.75 vision look like, and does the size of the number matter?

People often type a lone number into a search box and ask what that vision “looks like.” A sphere of -5.75 means moderate-to-high nearsightedness. Without correction, the world is sharp only within about 17 centimeters of the face (one divided by 5.75 meters), and beyond that faces blur into ovals and street signs dissolve. With glasses or contact lenses, the same eye can very often read 20/20.

That distinction is the whole point. Refraction numbers describe focus; acuity numbers describe what you can actually see once focus is corrected. A -5.75 eye and a -0.50 eye may have identical corrected acuity. The bigger number needs thicker lenses and more careful frame choice, but it is not “sicker” in itself.

Where magnitude does matter is risk over time. Higher degrees of myopia are associated in population studies with increased lifetime rates of retinal tears and detachment, certain forms of glaucoma and earlier cataract, because the eyeball is longer and its tissues are stretched thinner. The National Eye Institute discusses these associations without attaching a single threshold, and clinicians commonly describe roughly -6.00 and beyond as “high” myopia. If your sphere sits in that region, expect your clinician to look at the retinal periphery more carefully and to ask about flashes and floaters at each visit.

Clinicians loosely describe roughly -0.25 to -3.00 as mild, -3.00 to -6.00 as moderate and beyond -6.00 as high, but these are working labels rather than diagnoses, and the language on your report may differ.

What is the normal eye pressure range, and how is it measured?

Intraocular pressure, abbreviated IOP, is the fluid pressure inside the eyeball, maintained by the constant production and drainage of a clear liquid called aqueous humor. It is reported in millimeters of mercury (mmHg), the same unit as blood pressure, and there is one figure per eye.

According to MedlinePlus, a typical range is about 10 to 21 mmHg. A reading of 17/18, right eye then left, sits comfortably in that band. Values above 21 are flagged as ocular hypertension; values well below 10 are unusual and prompt a look for causes such as recent surgery or inflammation.

Two measurement methods appear on reports. Non-contact tonometry, the air puff, is quick and needs no drops but tends to read slightly high in some people. Applanation tonometry uses a numbed cornea and a small flat-tipped probe and is the reference method. Corneal thickness influences both: a thick cornea resists flattening and inflates the reading, a thin one deflates it, which is why some reports include a pachymetry figure in micrometers next to the pressure.

Pressure also varies through the day, often peaking in the early morning, so a single value is a rough guide. The NHS is clear that glaucoma, the group of conditions where the optic nerve is damaged, can occur at any pressure, and that raised pressure alone does not equal glaucoma. Roughly a third of people with glaucoma have never had a reading above 21. That is why the pressure line is read alongside the optic nerve images and, where indicated, a visual field test, never on its own.

What do retinal photographs and OCT scans show?

The orange disc stapled to your report is a fundus photograph: a wide picture of the back of the eye taken through the pupil. Its color comes from blood in the choroid, the vessel-rich layer beneath the retina. Three landmarks matter most. The pale circle toward the nose is the optic disc, where the optic nerve leaves the eye; the darker patch toward the center is the macula, responsible for reading and face recognition; the branching red lines are arteries and veins.

Clinicians look at the ratio of the pale central “cup” to the whole optic disc, written as C/D. Ratios around 0.3 to 0.4 are common; a large or enlarging cup, or one that differs markedly between eyes, is a glaucoma signal. They also check the vessel walls for signs of high blood pressure, the retina for the tiny hemorrhages of diabetes, and the macula for the yellow deposits called drusen that mark early age-related changes.

OCT, optical coherence tomography, is a different animal. It uses reflected light to build a cross-section of the retina, layer by layer, with a resolution of a few micrometers, roughly a hundredth of a millimeter. Reports often include a retinal thickness map in color, a graph of the nerve fiber layer around the disc, and a ganglion cell analysis, with your values plotted against an age-matched reference range. Green means within the range, yellow borderline, red outside it. Red on an OCT printout is a flag for closer review, not a diagnosis; artefacts, high myopia and normal anatomical variation can all color a square red. The National Eye Institute explains why a dilated view, with or without imaging, remains the anchor of this part of the exam.

Visual field tests, color vision and the other lines you may see

Not every report includes these, but when they appear they tend to confuse.

A visual field test maps how far you can see to the sides while staring straight ahead. You press a button each time a faint light appears, and the machine plots which points you missed. The printout shows a gray-scale map (darker means dimmer sensitivity) and two summary figures: mean deviation, how far your whole field sits below an age-matched norm, and pattern standard deviation, how irregular the loss is. A reliability index is printed too, because a tired or blinking patient produces a noisy test. Repeat testing is routine before anything is concluded from a single field.

Color vision is often screened with numbered plates. A result reading “14/14” or “normal” needs no action; a deficiency is usually inherited and stable, but a new change in one eye can point to optic nerve trouble and is followed up.

Cover testing and ocular motility describe how the eyes align and move. Words such as “orthophoric” (aligned) or “exophoria” (a tendency to drift outward when one eye is covered) are descriptive and, in small degrees, common.

Slit-lamp findings describe the front of the eye: cornea, iris, lens. Phrases like “trace nuclear sclerosis” mean early, mild lens clouding, which is near-universal by the sixties and does not by itself call for cataract surgery. The Mayo Clinic outlines these components as part of a standard comprehensive assessment. If a term is unfamiliar, the front-of-eye section is the one most often written in shorthand, so ask.

Eye exam results explained in one table

This table gathers the fields that appear on most reports, what each measures, and what a typical or commonly seen range looks like. Ranges are drawn from the sources cited in this article and are reference points, not pass-or-fail lines.

Field	What it measures	Unit	Commonly seen or typical range
SPH	Main focusing power needed (minus = nearsighted, plus = farsighted)	Diopters	0.00 = no correction; most adults fall between about -6.00 and +4.00
CYL	Astigmatism correction	Diopters	Blank or 0.00 = none; up to about 1.00 is very common
AXIS	Orientation of the astigmatism correction	Degrees	1 to 180; not a power, so no “good” or “bad” value
ADD	Extra near power for reading segments	Diopters (always plus)	About +0.75 to +3.00, rising with age
Visual acuity	Smallest letters read at 20 feet	Fraction	20/20 reference; 20/200 or worse best-corrected meets the US legal blindness definition
IOP	Fluid pressure inside the eye	mmHg	About 10 to 21
C/D ratio	Size of optic nerve cup relative to disc	Ratio	Often 0.3 to 0.4; asymmetry between eyes is the key flag
OCT RNFL	Thickness of nerve fiber layer around the disc	Micrometers	Plotted against age-matched norms; green within range

Two cautions when using it. The refraction rows describe focus, not eye health; a person with -7.00 can have a perfectly healthy retina and a person with 0.00 can have advanced glaucoma. And the pressure row is the most misread: a value inside the range does not exclude glaucoma, and a value just above it does not confirm it. Sources for these ranges include MedlinePlus and the National Eye Institute.

Who usually needs a full dilated exam, and who is often told they can wait

Not everyone needs the full battery every year, and a report that says “recall 24 months” is not a brush-off.

The NHS advises a sight test at least every two years for most adults, more often if your optometrist recommends it. The Mayo Clinic suggests a baseline comprehensive exam around age 40 for adults with no symptoms or risk factors, then every one to two years from age 60 onward. Children are typically screened at birth, again in the preschool years and before starting school, with follow-up set by what those screenings find.

Certain groups are usually asked to come every year and to have the pupils dilated each time. The National Eye Institute lists people with diabetes, those with a family history of glaucoma, African American adults over 40 and everyone over 60 as needing a dilated exam annually or as often as their clinician advises. High myopia, previous retinal problems and long-term use of certain medicines that can affect the retina also shorten the interval.

People asked to wait are generally younger adults with a stable prescription, no symptoms and no risk factors; for them, retinal photography without dilation may be judged sufficient at some visits. Dilation is occasionally deferred for practical reasons too, such as someone who has to drive straight home and could not arrange a lift, and rescheduled rather than skipped.

Whatever the interval on your report, the decision about frequency sits with the clinician who examined you, and it is reasonable to ask what specifically led to the recall date they chose.

What the following days and weeks usually look like

If your pupils were dilated, the hours after the exam are the strangest part. The National Eye Institute says the effects of dilating drops usually last about four to six hours, though they can persist longer in people with light-colored eyes. During that window, near vision is blurred, bright light is uncomfortable and driving is unwise. Sunglasses help; so does postponing the small print until evening.

New glasses bring their own adjustment. A modest change in sphere is often absorbed within a few days. Larger changes, a first pair of progressive lenses or a new astigmatism axis can make floors seem to tilt or doorframes bow for a week or two while the brain relearns the geometry. Most opticians suggest wearing the new pair consistently rather than switching back and forth, and returning if the effect has not faded after about two weeks, since a small manufacturing error or a mismeasured PD is easy to check.

If the report flagged something borderline, a raised pressure, a red square on the OCT or an unreliable visual field, the usual next step is a repeat measurement rather than treatment. Pressure may be rechecked at a different time of day; fields are commonly repeated because the first attempt is a learning run. This waiting period is not neglect. It separates a single noisy reading from a real trend.

Referral letters, when they are needed, move at different speeds depending on what was found: a suspected retinal tear is an urgent same-day matter, while a stable-looking early cataract may simply be noted for review at the next routine visit. Your report or your clinician should tell you which category you fall into; if it does not, ask before you leave.

What people often get wrong about eye exam results

Several myths survive because the report format encourages them.

“A bigger number means my eyes are getting worse.” A rising minus sphere means more nearsightedness, which is a change in focus, not in the health of the eye. The health information is in the pressure, the retinal images and the best-corrected acuity, none of which the sphere predicts.

“Wearing glasses weakens your eyes.” There is no mainstream evidence that correcting a refractive error accelerates it in adults. In children, current research on myopia progression is active and evolving; the National Eye Institute describes refractive errors as driven mainly by the shape of the eye and by genetics, with environmental factors under study.

“Normal pressure means no glaucoma.” The NHS is explicit that glaucoma can occur with pressure in the typical range. Pressure is one risk factor; the optic nerve appearance and visual field carry the diagnosis.

“Red on the OCT means disease.” The color coding compares you with a reference population. Tall people, very short people, those with high myopia and those with unusual disc shapes can fall outside the reference without anything being wrong. Clinicians look at the pattern and at change over time.

“20/20 means healthy eyes.” Acuity tests the central few degrees of vision. Early glaucoma, peripheral retinal tears and many other conditions leave 20/20 untouched until late. This is the single strongest argument for a dilated exam even when you see well.

“The air-puff test is the real glaucoma test.” It is a screening measure of pressure, useful but imprecise, and it is not a substitute for examining the nerve.

Questions to ask your care team before you leave

Ten minutes at the end of an exam is usually enough to turn a puzzling sheet into a plan. These questions cover the gaps that reports most often leave.

• Has my prescription changed since last time, and by how much? Is the change in sphere, cylinder or both?
• Are you writing this in plus or minus cylinder notation, so I can compare it with earlier copies?
• What was my best-corrected acuity in each eye, and is it what you would expect for my age?
• What was my pressure in each eye, which method did you use, and does my corneal thickness affect how you read it?
• How does my optic nerve look compared with my last visit? Is the cup-to-disc ratio stable?
• Did the retinal photograph or OCT show anything you are watching, and if so, what would change your mind about it?
• Do I need a visual field test, and if one was done, was it reliable enough to interpret?
• Which of my findings are simply age-typical, and which are risk factors that change how often I should be seen?
• When should I come back, and what specifically is that interval based on?
• Are there symptoms that should bring me in sooner than the recall date?
• May I have a copy of the images and scans as well as the prescription, for my own records?

Bringing the previous report helps enormously. The NHS notes you are entitled to your prescription after a sight test, and the same logic applies to imaging: comparing today’s OCT with one from three years ago answers more questions than any single scan. If a term on the report was not explained, point to it. Clinicians write in shorthand for each other and are generally glad to translate.

When to call your doctor: red-flag signs that should not wait for the next appointment

Most of what appears on an eye report is followed up at a measured pace. A few symptoms, however, override the recall date entirely, and the NHS and Mayo Clinic both advise urgent assessment for them.

Seek same-day care, through your eye clinic or an emergency department, if you notice a sudden shower of new floaters, flashes of light like a camera flash at the edge of vision, or a dark curtain or shadow moving across part of what you see. Together these can signal a retinal tear or detachment, which is time-critical. The risk is higher in people with high myopia or a previous detachment in either eye.

Sudden loss or blurring of vision in one eye, even if painless and even if it recovers within minutes, needs urgent evaluation because it can reflect a blocked retinal blood vessel or a transient ischemic event. A severe, aching eye with a red appearance, a cloudy or halo-ringed view of lights, nausea and a pupil that looks mid-dilated and fixed is the classic picture of acute angle-closure, a form of glaucoma in which pressure rises rapidly; the NHS lists this as a medical emergency.

Also call promptly, within a day or two, for new double vision, a drooping eyelid, a new blind spot you can map by covering one eye, eye pain with light sensitivity, or a red eye that follows an injury or contact lens wear. People with diabetes should report any new distortion or blurring rather than waiting for the annual retinal photograph.

None of these lists is exhaustive. When something about your vision changes abruptly, the safe default is to call the team that examined you and describe exactly what you are seeing. They will decide how quickly you need to be seen; that decision, like every other in this article, belongs with them.

Frequently asked questions

What does +2.75 mean on an eye prescription?

A sphere of +2.75 means the eye needs 2.75 diopters of plus (converging) power, which indicates moderate farsightedness. Younger eyes can often compensate by focusing harder, so the number may cause only eye strain; older eyes usually need the correction for both near and distance. If +2.75 appears on the ADD line instead, it refers to the reading segment of a bifocal or progressive lens, not the eye’s basic focus.

What does 5.75 vision look like without glasses?

A sphere of -5.75 is moderate-to-high nearsightedness. Uncorrected, objects are sharp only within roughly 17 centimeters of the face, and anything farther blurs heavily. With the right glasses or contact lenses, the same eye can frequently read 20/20. Higher myopia is associated in population studies with increased risk of retinal tears, so clinicians typically examine the retinal edges more carefully and ask about flashes and floaters.

What is the normal eye SPH, CYL and AXIS value?

A sphere and cylinder of 0.00, sometimes written plano, mean no correction is needed, and there is no axis without a cylinder. In practice most adults have some refractive error; spheres between about -6.00 and +4.00 and cylinders up to about 1.00 are common. Axis is simply an orientation from 1 to 180 degrees, so no value is more normal than another. What matters is whether the numbers are stable over time.

What is considered a bad vision score?

There is no single cutoff, because the meaningful figure is best-corrected acuity, what you see through the right lenses. Many US driving standards sit around 20/40, and legal blindness is defined by the National Eye Institute as 20/200 or worse in the better eye with correction, or a field of 20 degrees or less. Poor uncorrected acuity that improves to 20/20 with glasses is a refractive error, not a health problem.

What does SPH, CYL and AXIS mean on my report?

SPH (sphere) is the main lens power, minus for nearsightedness and plus for farsightedness. CYL (cylinder) is the additional power that corrects astigmatism, the condition where the eye’s surface is curved unevenly. AXIS is the angle, in degrees, that tells the lab which way to orient that cylinder correction. Together they describe the shape of the lens that focuses light on your retina.

What is 20/20 vision, and is 20/15 better?

20/20 means you read at 20 feet what a person with typical sight reads at that distance; it is a reference standard, not a ceiling. Reading 20/15 means you resolve at 20 feet what most people need to be 15 feet away to see, so yes, it is sharper, and it is common in healthy young adults. Acuity tests only central vision, so 20/20 does not rule out peripheral disease such as early glaucoma.

What is the normal eye pressure range?

MedlinePlus gives a typical intraocular pressure range of about 10 to 21 mmHg, measured with a puff of air or a small probe on a numbed cornea. Readings above 21 are called ocular hypertension and prompt monitoring, but pressure varies through the day and is influenced by corneal thickness. Glaucoma can develop within the typical range, so pressure is interpreted together with optic nerve appearance and, when needed, a visual field test.

What does the retinal photograph show, and why is it orange?

A fundus photograph is a picture of the back of the eye taken through the pupil. Its orange color comes from blood in the vessel-rich layer beneath the retina. Clinicians examine the optic disc and its central cup, the macula responsible for detailed vision, and the blood vessels for signs of diabetes or high blood pressure. It records a baseline so that changes can be spotted at later visits.

What is an OCT scan and what do the colors mean?

Optical coherence tomography uses reflected light to build a cross-section of the retina at a resolution of a few micrometers. The printout compares your retinal and nerve fiber layer thickness with an age-matched reference range: green is within range, yellow borderline, red outside it. Red flags an area for closer review rather than a diagnosis, because high myopia, unusual anatomy and scan artefacts can all produce readings outside the reference.

How often should adults have an eye exam?

The NHS recommends a sight test at least every two years for most adults, and the Mayo Clinic suggests a baseline comprehensive exam around age 40, then every one to two years from 60. The National Eye Institute advises an annual dilated exam for people with diabetes, a family history of glaucoma, African American adults over 40 and everyone over 60. Your clinician sets the interval based on your findings and risk.

References

• MedlinePlus – Standard ophthalmic exam
• MedlinePlus – Tonometry
• NHS – Glaucoma
• National Eye Institute (NIH) – Get a dilated eye exam

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.