Short answer
A cataract is a clouding of the eye's natural lens. It develops over years and without pain, which makes it easy to ignore — the first sign is often glare at night, or new glasses that no longer give a sharp picture. No drop or supplement restores the lens. The only treatment is a lens exchange, and the timing is decided by how much the cataract takes out of your day, not by how dense it looks under the microscope.
Have you noticed that the world around you seems increasingly blurry, hazy or washed out, as if you are looking through a foggy or dirty window? Do oncoming headlights create blinding glare and halos during night driving, or do bright colours appear faded and yellowed?
If these symptoms sound familiar, you may be experiencing a cataract. Cataracts are the leading cause of reversible vision loss worldwide. While they develop naturally as part of the eye's ageing process, advanced surgical techniques make them completely treatable. Modern cataract surgery — also known as refractive lens exchange — not only restores optical clarity but can simultaneously correct pre-existing nearsightedness, farsightedness, astigmatism and reading vision loss.
Optical anatomy and how cataracts develop
The human eye functions much like a camera. Located directly behind the pupil and iris is the eye's natural crystalline lens. The primary job of the lens is to refract incoming light rays and focus them sharply onto the retina at the back of the eye.
In a young, healthy eye, the natural lens is perfectly clear and flexible. As we age, metabolic changes cause the protein fibres within the lens to break down and clump together. These protein clumps create cloudy, opaque patches inside the lens.
This progressive clouding of the natural lens is defined as a cataract. As the cataract grows denser, it blocks and scatters light passing through the eye, preventing a sharp image from reaching the retina. As a result, vision becomes foggy, dim and distorted.
Signs and symptoms
Cataracts typically develop slowly and painlessly over several years. In the early stages, slight cloudiness may not cause noticeable visual disruption, but as the condition progresses the symptoms become clearer.
- Progressive blurry or cloudy visionDistance and near vision lose sharpness and contrast. When reading, it feels as if there is never enough light.
- Glare and halos around lightsIncreased sensitivity to bright sunlight and distracting glare or starburst halos around streetlights and headlights while driving at night.
- Faded or yellowed colour perceptionColours appear dull, brownish or less vibrant because the clouded lens acts as a yellow filter. Blues and greens go first.
- Double vision in a single eyeUneven lens clouding causes incoming light rays to split, creating ghost images or double outlines. In medical terms, monocular diplopia.
- Temporary "second sight"Nuclear cataracts can temporarily increase the lens's refractive power — a myopic shift — allowing someone who has worn reading glasses for years to read without them. This is temporary, and distance vision deteriorates at the same time.
- Frequent changes in eyeglass prescriptionsNew prescription glasses no longer provide sharp clarity, because the issue is lens transparency, not focal power.
Types and causes
Cataracts are categorised based on where the cloudiness forms within the lens. The most common form is age-related, present in more than 60% of people over 60.
- Nuclear cataractsForm in the centre, the nucleus, of the lens. They progress slowly and cause a myopic shift.
- Cortical cataractsBegin at the outer edge, the cortex, of the lens as wedge-shaped spokes pointing toward the centre, causing significant glare.
- Posterior subcapsular cataractsDevelop directly beneath the back capsule of the lens on the visual axis. They progress rapidly and impair reading vision and vision in bright light. More common in diabetes and with steroid use.
Key risk factors. Ageing, the most common factor over 60. Prolonged exposure to ultraviolet sunlight without eye protection. Medical conditions such as diabetes and hypertension. Previous eye injuries, inflammation or eye surgery. Long-term use of corticosteroid medication. Smoking and excessive alcohol consumption.
Diagnostic assessment
- Visual acuity testMeasures distance and near vision sharpness under varying light conditions.
- Slit-lamp examinationA specialised microscope illuminates and enlarges the structures at the front of the eye, letting the doctor evaluate the location and density of lens clouding.
- Intraocular pressure testRules out elevated eye pressure, that is glaucoma.
- Dilated eye examEye drops widen the pupil to inspect the retina and optic nerve for co-existing retinal conditions such as macular degeneration.
- Optical biometry and corneal topographyPrecision instruments measure the length of the eyeball and the curvature of the cornea to calculate the exact power of the new intraocular lens.
Treatment: micro-surgical lens replacement
There are no eye drops, exercises, diets or medications clinically proven to reverse or prevent cataracts. The only effective, permanent treatment is cataract surgery, during which the clouded natural lens is removed and replaced with a clear, permanent intraocular lens.
Modern phacoemulsification procedure
- Anaesthetic eye drops are applied; the procedure is completely painless.
- A tiny micro-incision, 1.8 to 2.2 mm, is made at the edge of the cornea.
- An ultrasound or laser probe gently breaks the cloudy lens into microscopic pieces, which are removed while the natural lens capsule is preserved.
- A flexible, foldable artificial intraocular lens is inserted into the capsule, where it unfolds into its permanent position.
- The procedure takes 15 to 20 minutes, requires no stitches, and patients return home the same day.
Types of intraocular lenses
The choice of intraocular lens determines visual quality and freedom from glasses after surgery. The choice is not made by which lens costs more, but by the distances you actually need to see in your day.
Monofocal IOL · a single focal point
Has one focal point, usually set for clear distance vision.
Advantage. The standard lens option covered by health insurance. Provides sharp distance clarity.
Limitation. Reading glasses are required for close-up tasks.
Toric monofocal IOL · with cylinder power
Incorporates astigmatism-correcting cylinder power into the lens.
Advantage. Corrects both the cataract and corneal astigmatism at the same time.
Limitation. Clear distance vision without astigmatism glasses; reading glasses still needed for near tasks.
Multifocal or trifocal IOL · several focal points
Splits light into multiple focal points: distance, intermediate and near.
Advantage. Suits driving, computer work, the theatre and reading without changing glasses.
Limitation. Splitting light across several focal points can bring more glare and halos on night drives.
EDOF IOL · extended depth of focus
Creates a continuous, extended field of vision from distance to intermediate range.
Advantage. Good contrast sensitivity and less glare at night than a multifocal.
Limitation. Removes glasses for distance and computer work; weak reading glasses may still be needed for tiny text.
Refractive lens exchange, and what KSA does
Although a cataract is mainly a condition of later life, refractive lens exchange is increasingly performed in patients aged 45 to 50 and over who do not yet have a full cataract but live with presbyopia or a high refractive error. When the biological lens is replaced before a cataract forms, a cataract cannot develop later, because an artificial lens does not cloud.
How it works at KSA
KSA handles the diagnosis, the staging, the decision on timing and the lens counselling. The pre-operative work-up and the follow-up are at KSA, so the same team follows your eye throughout. When the time for the operation comes, we plan it together with you.
The path starts with the Audit eye examination, which maps the retina, corneal topography, intraocular pressure and the structure of the lens. Only after those measurements can anyone say whether your cataract needs replacing and which lens matches your day.
If the cataract is early and there is no reason to operate yet, there is a cataract monitoring package: lens density measured with a Scheimpflug camera, macular OCT, biometry, and the doctor's assessment of when a lens exchange is worth considering. You do not have to guess for years whether it is time.
First step: the Audit eye examination
The route to clear vision starts with a thorough diagnosis. The Audit eye examination is a comprehensive examination in Tallinn and Tartu, where experienced optometrists and ophthalmologists assess the lens, the length of the eyeball, 3D topography and intraocular pressure, and tell you what your eye needs now.
We examine in Tallinn and Tartu.
Closely related: presbyopia and reading glasses, astigmatism and hyperopia.