Most people recognise when blurry vision starts interfering with daily life. Road signs become harder to read, a menu needs to be held farther away, or the text on a phone keeps getting larger. Those changes are difficult to ignore.
Eye disease can be much quieter. Some conditions develop gradually, cause no pain, and leave central vision feeling normal in their early stages. A person may continue reading, working, and driving without realising that something has changed.
Daniel M. Cotter, MD, is an ophthalmologist and eye surgeon at Eye Care & Vision Associates [1]. During a comprehensive examination, the assessment extends well beyond reading an eye chart. Depending on a person’s age, health history, and previous findings, the examination may include checks of eye pressure, peripheral vision, the optic nerve, the retina, and the lens [9].
An eye can look different during an examination long before daily vision feels different.
Pain is not a reliable measure of eye health
Pain can be a useful warning elsewhere in the body. Many chronic eye conditions, however, do not hurt.
Open-angle glaucoma is one example. It damages the optic nerve and usually begins without noticeable symptoms. Vision loss often starts at the edges of the visual field rather than in the sharp central vision used for reading and recognising faces. Because the change can happen slowly, people may continue with familiar activities without realising that part of their side vision has been affected [2].
Someone with glaucoma may feel that nothing is wrong while damage is developing. Measuring eye pressure, examining the optic nerve, and testing the visual field can reveal changes that comfort and visual sharpness do not show [2, 9].
Diabetic retinopathy may also progress without an obvious warning. Changes in the retinal blood vessels can be present even when a person sees clearly. The condition can reach a vision-threatening stage before symptoms appear, which is why screening recommendations are based on diabetes history and examination findings rather than on how the eyes feel [5].
Cataract symptoms may develop slowly enough to be dismissed at first. Someone might blame poor lighting, dirty glasses, tired eyes, or unusually bright headlights. Instead of recognising a vision change, they may begin using stronger lamps or avoiding night driving.
Not every small inconvenience points to disease. Still, an absence of pain does not confirm that the structures inside the eye are healthy. That is information an examination is designed to provide.
One eye can compensate for changes in the other
Most daily activities are performed with both eyes open. The brain combines the information from each eye into one view, helping with depth perception and awareness of the surrounding area.
That combined view can also hide a developing problem.
Suppose one eye has lost sensitivity in part of its peripheral field while the other still sees that area well. Information from the stronger eye may partly cover the gap. Research involving people with glaucoma has found that defects that do not overlap between the two eyes can leave the combined visual field looking relatively intact, even though each eye has measurable loss [3].
The stronger eye cannot replace every function of the weaker one. In a study that simulated unequal peripheral vision loss, worsening vision in the weaker eye slowed performance during a visual-search task even though the better eye remained unchanged. Participants also made more eye and head movements as the simulated loss became more severe [4].
Gradual changes can lead to small adjustments that soon feel normal. A person might turn their head more often, move closer to a screen, avoid dim settings, or rely on familiar driving routes without thinking much about why.
Covering one eye and then the other may reveal a large difference, but it cannot detect every problem. Small blind spots, reduced contrast sensitivity, early retinal changes, and optic-nerve damage may not be apparent during a casual home check.
This is why the eyes are tested separately during a comprehensive examination. Each one may be functioning differently, even when vision with both eyes open seems comfortable.
Diabetes, blood pressure, and medications can affect the eyes
Eye health is connected to the health of the rest of the body. The retina contains a network of small blood vessels, while the optic nerve depends on healthy circulation and nerve function. Conditions that affect blood vessels or metabolism may affect vision as well.
For people with diabetes, examination timing is based on more than symptoms. The American Diabetes Association recommends an initial dilated, comprehensive eye examination when type 2 diabetes is diagnosed. Adults with type 1 diabetes should generally have their first examination within five years after the condition begins. Later intervals depend on retinal findings, blood-glucose control, pregnancy, and other risk factors [5].
High blood pressure can affect the eyes even when it causes no visual warning. Uncontrolled hypertension can injure the small vessels supplying the retina, sometimes leading to swelling or reduced blood flow. Visual symptoms may not appear immediately, so people with high blood pressure should ask whether it changes their recommended examination schedule [6].
Certain medicines require attention as well. Extended use of some steroid eye drops can raise pressure inside the eye in susceptible people and contribute to a cataract near the back of the lens. Drug-label guidance recommends monitoring eye pressure when these medicines are used for prolonged periods [7].
Hydroxychloroquine, which is prescribed for several autoimmune conditions, can damage the retina in some long-term users. Current guidance recommends a baseline retinal examination soon after treatment begins. Screening commonly uses optical coherence tomography, which creates detailed cross-sectional images of the retina, and fundus autofluorescence, which can show changes in retinal tissue. Annual testing may be deferred during the first five years when no significant risk factors are present [8].
These medicines may be essential for managing serious conditions. Patients should not stop them or change a dose without speaking to the prescribing clinician. An accurate list of prescription medicines, eye drops, over-the-counter products, and past steroid use gives the eye doctor important context.
Family eye-health history is another useful part of the record. Having a close relative with glaucoma, age-related macular degeneration, or retinal detachment may increase your own risk [2, 10, 12].
How to decide when your next exam should be
There is no single examination schedule for every adult. Age offers a general starting point, but medical history, family history, medications, previous injuries, and earlier examination results may be equally important.
The American Academy of Ophthalmology’s 2026 guidance suggests that adults without symptoms or known risk factors receive comprehensive medical eye evaluations every five to ten years before age 40. Suggested intervals narrow to every two to four years from ages 40 to 54, every one to three years from ages 55 to 64, and every one to two years beginning at age 65 [9].
Those intervals are not intended to replace personal advice. Someone with diabetes, a family history of glaucoma, an existing eye condition, medication-related risk, or an abnormal previous finding may need more frequent care.
A few details can help shape the discussion with an eye doctor. When was the last comprehensive examination rather than a basic vision screening? Has a close relative been diagnosed with an eye disease? Are diabetes, high blood pressure, an autoimmune condition, an old eye injury, or long-term medication use part of the medical history? Changes such as increased glare, difficulty in dim light, reduced contrast, or a noticeable difference between the eyes are also worth mentioning.
Routine scheduling is only one side of eye care. Some symptoms require faster action.
A sudden increase in floaters, flashes of light, or a curtain-like shadow can be associated with retinal detachment and requires immediate evaluation [10]. Sudden, painless loss of vision in one eye may result from a blockage in the retinal circulation and should also be treated as an emergency [11]. Intense eye pain with redness, nausea, or blurred vision may occur with acute angle-closure glaucoma and needs urgent care [2].
In Western New York, Dr. Cotter’s practice provides this type of evaluation across four offices and treats conditions including cataracts, glaucoma, macular degeneration, and diabetic retinopathy. That range can be useful when an examination identifies a change that requires further evaluation or continued monitoring [1].
Even a normal examination has value. It documents how the eyes look and function now, creating a record that can be compared with future findings.
If you are unsure when your next comprehensive eye examination is due, ask an eye-care professional rather than waiting for your vision to change.
References
[1] ECVA. (n.d.). Daniel M. Cotter, MD. https://www.ecvaeyecare.com/daniel-cotter/
[2] National Eye Institute. (2025, November 26). Glaucoma. https://www.nei.nih.gov/eye-health-information/eye-conditions-and-diseases/glaucoma
[3] Joao, C. A. R., Scanferla, L., & Jansonius, N. M. (2021). Binocular interactions in glaucoma patients with nonoverlapping visual field defects: Contrast summation, rivalry, and phase combination. Investigative Ophthalmology & Visual Science, 62(12), Article 9. https://doi.org/10.1167/iovs.62.12.9
[4] Chow-Wing-Bom, H., Dekker, T. M., & Jones, P. R. (2020). The worse eye revisited: Evaluating the impact of asymmetric peripheral vision loss on everyday function. Vision Research, 169, 49-57. https://doi.org/10.1016/j.visres.2019.10.012
[5] American Diabetes Association Professional Practice Committee for Diabetes. (2026). Retinopathy, neuropathy, and foot care: Standards of Care in Diabetes-2026. Diabetes Care, 49(Supplement 1), S261-S276. https://doi.org/10.2337/dc26-S012
[6] American Heart Association. (2024, May 8). How high blood pressure can lead to vision loss. https://www.heart.org/en/health-topics/high-blood-pressure/health-threats-from-high-blood-pressure/how-high-blood-pressure-can-lead-to-vision-loss
[7] U.S. National Library of Medicine. (2025, March). Prednisolone acetate ophthalmic suspension USP, 1% [Drug label]. DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8d8e8f9b-4d65-426f-8c57-451001cdd849
[8] Marmor, M. F., Ahn, S. J., Ehlers, J. P., Melles, R. B., Mieler, W. F., Sarraf, D., & Yusuf, I. H. (2026). Special AAO report: Recommendations on screening for hydroxychloroquine retinopathy (2025 revision). Ophthalmology, 133(4), 439-450. https://doi.org/10.1016/j.ophtha.2025.11.001
[9] Wallace, D. K., Flaxel, C. J., Gedde, S. J., Jacobs, D. S., Kopplin, L. J., Lee, B. S., Mah, F. S., Oetting, T. A., Varu, D. M., & Musch, D. C. (2026). Comprehensive adult medical eye evaluation Preferred Practice Pattern. Ophthalmology, 133(4), P202-P236. https://doi.org/10.1016/j.ophtha.2025.12.031
[10] National Eye Institute. (2025, November 5). Retinal detachment. https://www.nei.nih.gov/eye-health-information/eye-conditions-and-diseases/retinal-detachment
[11] Mac Grory, B., Schrag, M., Biousse, V., Furie, K. L., Gerhard-Herman, M., Lavin, P. J., Sobrin, L., Tjoumakaris, S. I., Weyand, C. M., & Yaghi, S. (2021). Management of central retinal artery occlusion: A scientific statement from the American Heart Association. Stroke, 52(6), e282-e294. https://doi.org/10.1161/STR.0000000000000366
[12] National Eye Institute. (2021, June 22). Age-related macular degeneration. https://www.nei.nih.gov/eye-health-information/eye-conditions-and-diseases/age-related-macular-degeneration
