Cataracts are detected through a comprehensive eye exam that includes a visual acuity test and a microscopic examination of your lens. You cannot diagnose a cataract at home, but you can recognize the visual changes that signal it’s time to get checked. Most cataracts develop gradually, so knowing what to watch for and what happens during a professional exam puts you in a good position to catch them early.
Visual Changes That Point to Cataracts
Cataracts cloud the natural lens inside your eye, and the symptoms tend to creep in slowly enough that you might not notice them right away. The most common signs include:
- Blurred, cloudy, or dim vision that doesn’t improve with new glasses
- Needing brighter light for reading and close-up tasks
- Trouble with glare from sunlight or bright indoor lighting
- Difficulty seeing at night, especially while driving
- Halos or starbursts around lights after dark
- Fading or yellowing of colors, as if looking through a tinted window
- Double vision in one eye
- Frequent prescription changes in your glasses or contacts
Not all of these show up at once. Some people first notice that night driving feels harder, while others realize they’re cranking up every lamp in the house to read. If colors look duller than they used to, or you’re squinting more in sunlight than the people around you, those are worth paying attention to.
What Happens During a Professional Exam
An eye doctor checks for cataracts using two main tests, both done in a single office visit that typically lasts under an hour.
Visual Acuity Test
This is the familiar letter chart. Your doctor measures how well each eye can see at various distances and determines whether your current glasses or contacts still correct your vision adequately. A drop in acuity that can’t be fixed with a stronger prescription often points to a cataract, though this test alone isn’t enough to confirm one.
Slit-Lamp Exam
This is the key diagnostic tool. You sit with your chin on a rest while the doctor looks through a specialized microscope that projects a thin, bright beam of light into your eye. The light illuminates the structures of your eye in cross-section, like slicing through layers, allowing the doctor to see the lens in fine detail. Any clouding, discoloration, or opacity in the lens shows up clearly under this magnification. The doctor also examines the nerves at the back of your eye and other structures to rule out additional problems.
Your pupils will usually be dilated with eye drops beforehand, which makes the lens easier to examine. Dilation takes about 20 to 30 minutes to kick in and can leave your vision blurry and light-sensitive for a few hours afterward. Bring sunglasses and consider having someone else drive you home.
Three Types of Cataracts Look Different
Not all cataracts form in the same part of the lens, and the type affects both how it’s detected and how it impacts your vision.
Nuclear cataracts develop in the center of the lens. They cause the core to become increasingly dense and yellow, eventually turning brown in advanced cases. These are the most common age-related type and tend to affect distance vision first. Interestingly, in early stages, a nuclear cataract can temporarily improve your near vision, a phenomenon sometimes called “second sight,” before overall clarity declines.
Cortical cataracts start as wedge-shaped opacities around the outer edge of the lens, resembling spokes on a wheel. They gradually extend inward. Because they scatter light as it enters the eye, glare is often the dominant complaint. Your doctor spots these using a technique called retroillumination, shining light through the pupil so the spokes stand out against the red reflex from the back of your eye.
Posterior subcapsular cataracts form on the back surface of the lens, right in the path of light heading toward the retina. They tend to develop faster than other types and disproportionately affect reading vision and vision in bright light. This type is more common in younger people, those who take corticosteroids, and people with diabetes. Even a small opacity in this location can cause noticeable symptoms.
Why Home Tests and Apps Fall Short
Online vision tests and smartphone apps can measure how sharp your eyesight is, but they cannot examine the physical structure of your lens. That distinction matters. A cataract is a physical change inside the eye, and confirming one requires magnified, direct observation.
One AI-powered smartphone app designed for cataract screening showed 96% sensitivity in a field study, meaning it caught most cataracts. But its specificity was only 25%, meaning it incorrectly flagged three out of four people who didn’t actually have cataracts. A tool that produces that many false positives creates unnecessary anxiety and follow-up visits.
Online vision tests also have significant limitations for anyone over 40, which is exactly the population most likely to develop cataracts. These tests can approximate your glasses prescription under controlled conditions, but they don’t detect eye diseases that may not yet cause obvious symptoms. Annual or biannual professional eye exams remain the only reliable way to catch cataracts and other conditions like glaucoma early.
Who Should Get Screened Earlier
Most cataracts are age-related and show up after 60, but certain factors push the timeline earlier. If any of the following apply to you, it’s worth scheduling regular eye exams sooner rather than later:
- Diabetes, which accelerates lens changes and increases the risk of posterior subcapsular cataracts
- Long-term corticosteroid use, whether oral, inhaled, or as eye drops
- Previous eye injury or surgery
- Heavy UV exposure over the years without consistent sunglasses use
- Smoking, which roughly doubles cataract risk
- Family history of early cataracts
For people between 18 and 39 with no risk factors, a comprehensive eye exam every five to ten years is generally sufficient. After 40, the interval should tighten to every two to four years, and after 60, annual exams are standard.
What Happens After a Cataract Is Found
A cataract diagnosis doesn’t automatically mean surgery. Many cataracts are small and slow-growing, and the only “treatment” for years may be updated glasses, better lighting, and anti-glare coatings on your lenses.
The decision to move toward surgery is based on how much the cataract affects your daily life, not on hitting a specific score on a vision chart. Guidelines from the UK’s National Institute for Health and Care Excellence explicitly state that access to surgery should not be restricted based on visual acuity alone, because that measurement often misses problems like glare, poor contrast sensitivity, and washed-out color perception that significantly affect quality of life. The conversation with your doctor should focus on whether your vision problems interfere with driving, reading, working, or other activities that matter to you.
If you do reach the point of surgery, Medicare Part B covers it in both outpatient hospital and doctor’s office settings. After meeting your annual deductible, you’re responsible for 20% of the approved amount. Medicare also covers one pair of standard-frame glasses or one set of contact lenses after cataract surgery that includes a lens implant. Private insurance coverage varies, but most plans treat cataract surgery as medically necessary once functional impairment is documented.