A patient-focused guide to vision testing, eye pressure, retinal scans, corneal measurements and the questions worth asking at your appointment.
A prescription may say 6/6 or 6/12. An eye-pressure reading might be 18 mmHg. A retinal scan may have unfamiliar colours and numbers. If you have received results like these, it is reasonable to ask what they mean and whether you need treatment. Yet a single number rarely provides the full answer. Eye tests measure different parts of the visual system, and an ophthalmologist interprets them alongside your symptoms, examination and medical history.
For people searching for an eye hospital in Delhi, understanding the examination process can make the first visit more productive. This article explains commonly used eye tests in plain language, what each test can reveal, and why an abnormal-looking report is not necessarily a diagnosis. It also explains how to prepare for a consultation in New Delhi and what to ask before agreeing to follow-up tests or treatment.
Why an eye test report is not the same as a diagnosis
Vision depends on several structures working together: the cornea and natural lens focus light, the retina receives it, and the optic nerve transmits information to the brain. An eye chart checks how clearly you can recognise detail. An eye-pressure test measures a possible risk factor for glaucoma. A retinal scan examines tissue structure. These tests answer different questions.
Two people can have the same spectacle number and very different eye health. Likewise, a person may read the smallest line on an eye chart and still have early retinal or optic-nerve disease. The medical decision comes from patterns across findings, not an isolated value. Repeat measurements may also be necessary because results can vary with testing conditions, eye-surface quality and patient cooperation.
If you are comparing eye care options, ask whether the consultation can assess the problem you actually have. Bharti Eye Foundation lists cataract, refractive surgery, glaucoma, retina, cornea and paediatric eye care among its services in East Patel Nagar, New Delhi. Details are available on its official website: https://bhartieyefoundation.in/
1. Visual acuity: what 6/6, 6/9 and 6/12 mean
Visual acuity describes how clearly you see standard letters or symbols at a defined testing distance. In India, many reports use the metric Snellen system. A result of 6/6 means you can identify at six metres what a reference observer with standard acuity identifies at six metres. A result of 6/12 means you identify at six metres what that reference observer can identify at twelve metres. A larger denominator generally indicates lower distance acuity under those conditions.
Acuity may be tested without glasses, with your existing glasses, and after refraction to find the most useful lens correction. The distinction matters. “Unaided 6/18, corrected 6/6” suggests that spectacles can improve the measured clarity, although it does not by itself exclude eye disease. If vision remains reduced despite an appropriate correction, further examination may be needed.
Near vision is measured separately and may use different notation. A good distance reading does not guarantee comfortable reading vision, especially as near focusing changes with age. Ask which eye was tested, whether the result was with or without correction, and whether the doctor considers it consistent with your symptoms.
2. Refraction: understanding SPH, CYL and AXIS
The spectacle prescription is a measurement of lenses that improve focus. SPH, or sphere, represents the amount of correction for nearsightedness or farsightedness. Negative sphere numbers generally indicate myopia; positive numbers often indicate hyperopia. CYL, or cylinder, describes the lens power used to correct astigmatism, and AXIS shows its orientation in degrees.
A prescription can change because of normal growth, age-related shifts, accommodation, or changes in the eye. Small differences do not automatically mean a condition is worsening. For contact lens fitting and for refractive surgery planning, spectacle numbers alone are not enough. Corneal curvature, eye-surface health, prescription stability and other clinical findings matter.
Patients exploring LASIK should understand that the purpose of a refractive evaluation is to determine eligibility and safety, not to guarantee an operation. Bharti Eye Foundation’s service page describes its LASIK offering: https://bhartieyefoundation.in/lasik-eye-surgery.html
3. Eye pressure (IOP): why one reading cannot confirm glaucoma
Intraocular pressure, often abbreviated IOP, is commonly recorded in millimetres of mercury (mmHg). It can be measured with instruments that briefly contact the eye or use a puff of air. Pressure is relevant because elevated IOP is an important modifiable risk factor for glaucoma, a group of disorders that can damage the optic nerve.
However, pressure within a commonly cited reference range does not rule out glaucoma, and a reading above that range does not by itself establish the disease. Corneal thickness, the measuring method, time of day, previous readings, optic-nerve appearance, visual-field results and the patient’s overall risk profile all affect interpretation. Some individuals have ocular hypertension without detectable glaucomatous damage, while others develop glaucoma without markedly high measured pressure.
If a report contains a single eye-pressure value, ask whether a repeat check, optic-nerve evaluation, corneal thickness test or visual-field assessment is indicated. The clinical objective is to understand your individual risk and monitor relevant changes over time. Hospital information about this specialty: https://bhartieyefoundation.in/glaucoma-treatment.html
4. Dilated retinal examination: looking beyond the spectacle number
During dilation, eye drops enlarge the pupils so the doctor can better view the retina and optic nerve. This examination may reveal changes related to diabetes, retinal disease, macular problems or other abnormalities that are not apparent from a routine spectacle check. Not every visit requires dilation, but it is particularly relevant in many retinal assessments and in patients with certain risk factors.
The drops may cause temporary light sensitivity and blurred near vision. The duration varies. Avoid driving until your vision has returned to a safe level, and arrange a ride if you expect dilation. Tell the team about any previous reaction to eye drops or eye condition that could affect the plan.
Diabetes deserves special attention. Diabetic retinal disease can develop before a person notices symptoms, so clear vision alone is not a reason to skip recommended screening. The schedule should be individualised with your ophthalmologist and treating physician. To understand the hospital’s retina-related services, see https://bhartieyefoundation.in/retina-surgery.html
5. OCT scan: what retinal and optic-nerve images show
Optical coherence tomography, called OCT, uses light to create cross-sectional images of tissue. A retinal OCT can help a specialist examine the layers of the retina and identify structural changes in the macula. OCT assessment of the optic nerve and related nerve-fibre layers can provide useful information in glaucoma evaluation and monitoring.
Reports often show coloured maps, thickness values and comparison ranges. Colours are not a stand-alone traffic-light diagnosis. Age, anatomy, scan quality, the instrument’s reference database and conditions other than the suspected disease may influence the display. A “red” section on a printout needs clinical explanation; a “green” section does not prove that everything is normal.
Serial OCT scans can be valuable because change over time may matter more than one result. When attending follow-up, bring earlier images and reports if available, ideally from the same device type. Ask whether the scan is technically reliable, what specific structure the doctor is tracking and whether the findings match your examination.
6. Visual-field test: measuring side vision
A visual-field test maps the sensitivity of your central and peripheral vision. During an automated test, you look at a fixed point and press a button when you notice light signals. It is widely used during glaucoma assessment and may be used for certain neurological or retinal concerns.
The task can feel difficult at first. Fatigue, loss of concentration, poor fixation and eyelid position may affect the output. For that reason, a first abnormal field is sometimes repeated before conclusions are drawn. Specialists compare field patterns with the optic-nerve examination, pressure history and relevant imaging.
A visual-field result is not a test of how “hard you tried.” If you struggled, mention it. Your clinician can explain whether the reading is reliable enough to guide a decision or needs confirmation.
7. Corneal topography and pachymetry: examining the front surface of the eye
Corneal topography maps the shape and curvature of the cornea, the transparent surface at the front of the eye. Some instruments provide more extensive tomographic information about both corneal surfaces and thickness distribution. Pachymetry specifically measures corneal thickness. These tests may be important when assessing irregular corneal shape, keratoconus or suitability for a laser vision-correction procedure.
A colourful corneal map is not a self-explanatory verdict. Contact lens wear, dryness and test quality may affect measurements. Before a refractive procedure, the surgeon considers multiple findings, including prescription, stability, tissue measurements and individual risk. Being unsuitable for one technique does not establish suitability for another; any alternative also requires its own assessment.
People researching LASIK, SMILE, CLEAR or ICL in New Delhi should ask the doctor which tests informed the recommendation, whether there are signs of corneal instability, and what the alternatives are, including continuing with glasses or contact lenses. Do not compare procedures on the basis of a single scan or an advertised technology.
8. Cataract measurements and biometry: why planning is individual
When cataract surgery is being considered, measurements of the eye help the surgeon select the power of the artificial intraocular lens. Biometry may measure eye length and corneal curvature, alongside other parameters depending on the instrument and case. These are planning measurements, not a promise of a particular final spectacle number.
Existing astigmatism, retinal conditions, previous refractive surgery and the health of the eye can influence the plan and the expected result. Patients should discuss the benefits and limitations of proposed lens types, the likelihood of needing glasses after surgery, and the risks and follow-up requirements.
Bharti Eye Foundation’s cataract information is available at https://bhartieyefoundation.in/cataract.html. A meaningful decision requires a surgeon’s assessment, not just lens-power figures from a report.
9. When normal-looking reports still need attention
A normal-looking printout should be interpreted in context. If your vision has suddenly changed, you have severe eye pain, there is an injury, or you notice new flashes, many new floaters or a curtain-like shadow, seek urgent eye or emergency medical evaluation rather than waiting for a routine appointment. These symptoms may indicate time-sensitive conditions. Call the facility first if you are unsure whether immediate assessment is available.
Persistent symptoms also deserve consideration even when initial acuity is good. For example, dry-eye symptoms, intermittent double vision, glare or difficulty focusing may require targeted examination rather than a new spectacle prescription alone. Your clinician may recommend specific testing or follow-up when the first examination does not fully explain what you experience.
10. How to prepare for an eye consultation in Delhi
A practical appointment starts with a short description of the problem: when it began, whether it affects one or both eyes, whether it is constant or intermittent, and what makes it better or worse. Bring previous prescriptions, eye test reports, scans and operative notes, if any. A medicine list is helpful, particularly when you use prescribed eye drops or have diabetes, hypertension or other ongoing conditions.
If you wear contact lenses, tell the clinic before tests such as corneal mapping or refractive-surgery screening. You may need to stop wearing lenses for an appropriate period before certain measurements; the clinic should give instructions based on lens type and planned testing. Do not independently stop prescribed medicines.
A useful appointment conversation can begin with five direct questions: What is the working diagnosis? Which findings support it? Is any result uncertain or worth repeating? What are the treatment and observation options? What symptoms should prompt an earlier return? Those questions help you understand the decision rather than leaving with unexplained numbers.
Understanding the next step: observation, further testing or treatment
Not every difference on a report requires immediate treatment. An updated glasses prescription may solve a refractive problem. A suspicious measurement may warrant repeat testing. A confirmed disorder may require medicine, laser treatment, surgery, or structured monitoring. The appropriate approach depends on the disease, its severity, symptoms, other health conditions and the patient’s preferences.
For progressive conditions, follow-up plans should specify the approximate review interval and which results will be compared. For elective treatment, ask what outcome is realistically expected, what limitations apply and what might happen if you delay. Shared decision-making is more reliable than choosing a procedure simply because it is new or frequently advertised.
Frequently Asked Questions
1. Does 6/6 vision mean my eyes are completely healthy?
No. It describes measured visual clarity under particular test conditions. Some retinal and optic-nerve disorders may be present despite good chart vision, so other examination findings and risk factors matter.
2. Is an eye-pressure reading of 18 mmHg normal?
It can fall within a commonly used reference range, but a single value cannot diagnose or exclude glaucoma. Your eye doctor interprets it with the optic nerve, corneal measurements, risk factors and, when appropriate, visual-field or OCT results.
3. Why did the doctor recommend pupil dilation when I only wanted new glasses?
Dilation may be recommended to inspect the retina and optic nerve or investigate symptoms and risk factors. The need depends on your clinical assessment, rather than the reason you initially booked.
4. Can an OCT scan show whether I need surgery?
An OCT can reveal structural information useful for diagnosis and follow-up. The need for surgery or another intervention depends on the whole clinical picture and cannot be decided from the scan alone.
5. What does a red or yellow area on my OCT printout mean?
Many devices compare measurements with a reference database and apply colour codes. Colours can be affected by anatomy, image quality and other conditions; ask your clinician to explain the actual measurement and its relevance.
6. Is corneal topography required for every eye check-up?
No. It is more often used when the corneal shape needs assessment, such as suspected keratoconus or evaluation for certain refractive procedures. Your doctor determines which tests are necessary.
7. Why would I need to repeat a visual-field test?
A first test may be affected by learning, fatigue, fixation or reliability problems. Repetition can help distinguish a consistent pattern from an unreliable result.
8. Can I drive after a dilated eye examination?
Dilating drops can blur near vision and increase light sensitivity for several hours. Do not drive while your vision is affected; consider arranging transport in advance.
9. Do I need LASIK, ICL or CLEAR if my spectacle power is high?
Not automatically. Eligibility depends on several measurements and health factors. Glasses and contact lenses may remain appropriate, and a refractive specialist should explain whether any procedure is suitable.
10. Where is Bharti Eye Foundation located and how can I book?
Bharti Eye Foundation lists its address as 1/3 East Patel Nagar, New Delhi – 110008. Appointment and contact information is available at https://bhartieyefoundation.in/contact.html; patients can confirm timing and the appropriate specialty before visiting.
Book an eye consultation at Bharti Eye Foundation, New Delhi
Bharti Eye Foundation is located at 1/3 East Patel Nagar, New Delhi – 110008. Its official website lists consultations across multiple ophthalmic specialties. For appointments or to confirm available tests and clinicians, call 011-35577127 or 011-43584748, or check https://bhartieyefoundation.in/contact.html. The website lists Monday to Saturday, 9:00 am to 6:00 pm, with Sunday closed; confirm current timings before travel. For sudden vision loss, severe pain or an eye injury, seek urgent medical care without waiting for a standard booking.
Conclusion: ask what a result means for your eyes
The value of an eye examination is not the number of machines used or the number of pages printed. It is the clinical explanation that connects your symptoms and risk factors with the right tests and a sensible next step. If you are looking for an eye hospital in Delhi, arrive prepared, ask which results matter, and seek an individual interpretation before making a treatment decision. A clear explanation is part of informed eye care.
Clinical reference used for general patient education: National Eye Institute, “Get a Dilated Eye Exam”: https://www.nei.nih.gov/eye-health-information/healthy-vision/finding-eye-doctor/get-dilated-eye-exam