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Eye test for glasses in Vasco: what happens and why it matters

What does a spectacle power test check?

A spectacle power test, often called an eye number check, finds out whether light focuses correctly inside your eye and which lens corrects it. It looks for four common conditions:

• Short sight (myopia): far things look blurred. It is corrected with minus power lenses.
• Long sight (hypermetropia): the eye has to work harder to focus, especially for near work. Young people may see clearly but get tired eyes or headaches. It is corrected with plus power lenses.
• Astigmatism: the front of the eye is curved more in one direction than the other, so things look blurred or stretched at every distance. It is corrected with cylinder power.
• Presbyopia: from the early 40s, the lens inside the eye slowly loses its ability to focus up close, and reading and phone work need extra power.

What happens during the test?

1. A few questions. What trouble you have, what work you do (driving, computer work, sewing, mending nets), whether you have diabetes or high blood pressure, which medicines you take, and whether anyone in the family has glaucoma.
2. Reading the chart. Each eye is tested on its own, then both together, for distance and near. If you do not read English letters, say so: the test can be done with symbols.
3. A starting estimate. The power is first estimated with an instrument or by shining a light into the eye (retinoscopy).
4. Fine-tuning with trial lenses. Lenses are changed in front of your eye and you are asked which is clearer. There are no wrong answers; if you are unsure, say so and the choice is checked again.
5. Near and middle distance. If you are over 40, or work long hours at a computer, the power for reading, phone and screen distance is checked too.
6. Measurements for your spectacles. The distance between your pupils is measured, and for progressive lenses the height of your pupils in the frame you choose.

Why have the test inside an eye hospital?

If your vision cannot be made fully clear with lenses, the cause is in the eye itself, not in the power. Cataract, diabetic changes in the retina, glaucoma, dry eye and problems of the optic nerve can all blur vision. A power test done in an eye hospital means the eye doctor can examine your eyes at the same visit, and a complete eye check-up adds the eye pressure test and a look at the retina. This is especially worth doing after 40, if you have diabetes, or if your power has changed quickly. Our page on when to change spectacles lists the warning signs.

About one adult in four in Goa has diabetes (ICMR-INDIAB study, 2023). High or swinging blood sugar can change spectacle power for days or weeks. If your sugar has been high, or has only just been brought under control, the eye doctor may advise waiting until it is steady before new lenses are made, so that you do not pay for glasses that soon feel wrong.

Eye tests for children

Children's eyes can focus so strongly that they hide their real power during a test. For an accurate reading, children are often given drops that relax focusing for a while. These drops blur near vision and make the eyes sensitive to light for several hours, and with some drops until the next day or longer. Plan the test for a time when your child does not have school work or exams right after. Our parents' guide to spectacles for children explains what comes next.

What if drops are used to widen the pupils?

When the eye doctor needs a detailed look at the retina, drops may be used to widen (dilate) the pupils. Your vision will be blurred and bright light will feel harsh for a few hours. Do not drive a car or ride a scooter home yourself after these drops: bring someone with you, or plan to take a taxi or bus. Sunglasses help on the way home.

How to read your prescription

• RE / LE (or OD / OS): right eye and left eye.
• SPH (sphere): the main power. A minus sign means short sight and a plus sign means long sight, for example -1.50 or +2.00.
• CYL (cylinder) and AXIS: the power and direction of the astigmatism correction. The axis is a number from 0 to 180 and is not a measure of how bad the eye is.
• ADD: extra plus power for reading, usually from the 40s onwards, used in reading glasses, bifocals and progressives.
• PD: the distance between your pupils, used to centre the lenses.

A spectacle prescription is not a contact lens prescription; contact lenses need their own fitting. Once you have your prescription, the next choice is the lens itself: see types of spectacle lenses.

Testing for computer glasses

A computer screen is usually further away than a book and closer than the road. If you are over 40 and use a screen for many hours, tell us how far your screen is from your eyes, or measure it at work. The middle-distance power can then be checked, and office or computer lenses made for that distance. Younger people with eye strain at screens often need only an accurate distance power and better screen habits.

Eye tests for a driving licence, a job or school

Vasco is a port, Navy and airport town, and many job forms ask for a vision and colour vision report. ReNew Vision issues eye fitness certificates for a driving licence, jobs and school after the eye check-up. Bring the form with you, and your spectacles if you already wear them.

How to prepare for your visit

• Bring your present spectacles, including reading glasses, and any old prescriptions.
• If you wear contact lenses, ask when you call whether to leave them out before the test, and bring your spectacles.
• Bring a list of your medicines and, if you have diabetes, your recent sugar reports.
• Come during the eye OPD, Monday to Saturday, 4 pm to 7 pm. The OPD is closed on Sunday. Directions are on our visit page.

When the test is done, the Vision Correction Centre in the same eye hospital can help you choose frames and lenses. See the Vision Correction Centre page for everything it provides.

Questions patients ask

How long does an eye test for glasses take?

The power test itself does not take long, but a full visit can take an hour or more, especially if drops are used to relax focusing or widen the pupils. Please come within the OPD hours, Monday to Saturday, 4 pm to 7 pm.

Can I drive after an eye test?

If no drops were used, usually yes, with your spectacles on. If drops were used to widen your pupils, do not drive a car or ride a scooter for a few hours, until your vision is clear again. Bring someone with you.

Can spectacles be made from a machine reading alone?

A machine reading is only a starting point. The final power is fine-tuned with trial lenses while you say what looks clearer and more comfortable, and children often need drops for an accurate result.

How often should I have my eyes tested for glasses?

Most adults should have a check every one to two years, or sooner if vision changes. Children with spectacles usually need a check every 6 to 12 months. People with diabetes need an eye check-up every year, even if their glasses feel fine.

Do I need to remove contact lenses before an eye test?

Often yes, for some hours before the test, so that the front of the eye is in its natural shape. Ask when you call 072489 88039, and bring your spectacles and your contact lens box or details.

This page is general eye-health information, not personal medical advice. Your eye doctor advises you after examining your eyes.