Can Cataracts Affect One Eye More Than the Other

Why Can Cataracts Be Worse in One Eye?

Cataracts develop when the normally clear lens inside the eye becomes cloudy. Age-related changes are the most common cause, but several other factors can contribute.

The two eyes are exposed to many of the same ageing processes, but they do not necessarily develop cataracts identically.

1. Natural differences between the eyes

The lenses in your two eyes can undergo age-related changes at different rates.

As a result, one eye may have a more advanced cataract while the other has only an early cataract.

2. Previous eye injury

An injury to one eye can increase the risk of developing a cataract in that particular eye.

This is one reason a person may have a noticeable cataract in one eye while the other eye remains relatively clear.

3. Previous eye surgery or inflammation

Certain previous eye procedures and eye conditions can increase the likelihood of cataract formation.

Long-term inflammation inside the eye can also contribute to cataract development.

4. Diabetes and other health factors

Diabetes is associated with a higher risk of cataracts, particularly when blood sugar levels are not well controlled.

Other factors associated with cataract development include long-term steroid use, smoking and prolonged exposure to sunlight without adequate eye protection.

5. Differences in the eye’s prescription

Sometimes the vision difference between two eyes is not caused entirely by the cataract.

A difference in glasses power, astigmatism or other eye conditions can make one eye appear substantially worse than the other.

This is why a comprehensive eye examination is important before assuming that cataracts are the only reason for unequal vision.

What Does It Feel Like When One Eye Has a Worse Cataract?

One of the most noticeable signs is a difference in visual quality between the two eyes.

You may still feel that you can see reasonably well because your stronger eye is compensating for the weaker one.

Common symptoms include:

• Blurred or cloudy vision in one eye
• Difficulty seeing clearly at night
• Increased glare from headlights or bright lights
• Halos around lights
• Faded or less vibrant colours
• Difficulty reading small print
• Frequent changes in glasses prescription
• Difficulty recognising faces from a distance
• Reduced contrast, making objects appear less distinct

Cataract symptoms generally develop gradually, so some people adapt to the changes without realising how much their vision has deteriorated.

A simple way to notice a difference

If you suspect one eye is worse, cover one eye at a time and compare how clearly you can see.

This can help you notice a difference, but it cannot diagnose a cataract. An ophthalmologist needs to examine the eye to determine whether a cataract is present and whether another condition may be contributing to the vision change.

Can a Cataract in One Eye Affect Both Eyes’ Vision?

It can affect how you experience vision overall, but a cataract in one eye does not physically spread to the other eye.

Your brain normally combines information from both eyes to create a single visual experience. When the image from one eye becomes significantly blurrier, the difference between the two eyes can become noticeable.

You may experience difficulty with:

• Judging distances
• Seeing clearly in low light
• Driving at night
• Reading or using digital screens
• Switching between near and distance vision
• Performing tasks that require accurate depth perception

The stronger eye may compensate for some of the reduction in the weaker eye, which is one reason people sometimes underestimate how much a cataract is affecting them.

Does a Cataract Get Worse Faster in One Eye?

It can.

There is no requirement for cataracts in both eyes to progress at the same speed. One cataract may remain mild for a long time while the other becomes more visually significant.

This is why an eye specialist may recommend monitoring one eye while discussing treatment for the other.

The decision is generally based on factors such as:

• How clear your vision is
• How much the cataract affects your daily activities
• Your ability to work or read
• Difficulty with night driving
• Glare and light sensitivity
• Your overall eye health
• Whether another eye condition is affecting vision

Cataract surgery is generally considered when the cataract is interfering with your quality of life or normal activities, rather than simply because a cataract is visible during an examination.

When Should You Consider Cataract Surgery in One Eye?

You do not necessarily need cataract surgery simply because a cataract has been diagnosed.

Early cataracts may cause few or no symptoms. In some cases, updated glasses, better lighting and regular monitoring can be helpful for a period of time.

Surgery may become appropriate when the cataract starts interfering with activities that matter to you.

For example, you may find that you:

• Struggle to drive safely at night
• Cannot read comfortably despite updated glasses
• Have persistent glare or halos
• Find work or household activities increasingly difficult
• Notice a significant difference between your two eyes
• No longer feel that glasses provide adequate vision

Cataract surgery involves removing the cloudy natural lens and replacing it with an artificial intraocular lens, commonly called an IOL. It is currently the definitive treatment for a visually significant cataract.

What If One Eye Needs Cataract Surgery but the Other Does Not?

This is quite common.

If the cataract in one eye is significantly affecting vision while the other eye still sees well, your ophthalmologist may recommend surgery only for the affected eye.

An important part of planning is considering the difference between the two eyes after surgery.

For example, if the two eyes have very different glasses powers, the surgeon may take this into account when selecting the artificial lens and planning the procedure.

Your surgeon will assess your eye measurements, existing prescription, visual needs and overall eye health before recommending the appropriate approach.

If cataracts eventually become significant in both eyes, treatment may be performed separately or, in selected circumstances, according to the surgeon’s recommended approach.

Can Glasses Correct a Cataract That Is Worse in One Eye?

Glasses can sometimes improve vision when a cataract is still mild, particularly if there has also been a change in your glasses prescription.

However, glasses cannot remove the cloudiness inside the natural lens.

As the cataract becomes more significant, changing the glasses prescription may no longer provide enough improvement. At that stage, an ophthalmologist can discuss whether cataract surgery would be beneficial.

There are currently no routine eye drops or medicines that can remove an established cataract. Surgery is the treatment that removes the cloudy natural lens.

How Is a Cataract in One Eye Diagnosed?

An ophthalmologist can usually identify a cataract during a comprehensive eye examination.

The assessment may include:

1. Visual acuity testing – checks how clearly you can see at different distances.
2. Refraction – determines whether a change in glasses power could improve your vision.
3. Slit-lamp examination – allows the doctor to examine the structures at the front of the eye, including the lens.
4. Dilated eye examination – helps evaluate the retina and other structures at the back of the eye.
5. Additional tests when necessary – may be recommended if another eye condition is suspected or before cataract surgery.

This comprehensive assessment is particularly important when there is a large difference in vision between the two eyes.

Is It Normal for One Eye to Have More Cataract Than the Other?

Yes.

It is entirely possible for cataracts to be present in both eyes but have different levels of severity.

One eye may have:

• An early cataract with minimal symptoms

while the other may have:

• A more advanced cataract causing significant visual problems.

The presence of a cataract does not automatically mean surgery is immediately necessary.

What matters most is how the cataract affects your vision and everyday life.

Can Cataracts Cause Different Glasses Powers in Each Eye?

Yes, cataract-related changes can sometimes be accompanied by changes in the glasses prescription.

You may notice that one eye’s prescription changes more than the other’s. Some people temporarily experience an improvement in near vision as the lens changes with cataract development, although this does not mean the cataract is improving.

If you are experiencing repeated prescription changes, blurred vision or a noticeable difference between your eyes, an eye examination is worthwhile rather than simply ordering stronger glasses.

How Can You Protect Your Eye Health?

You cannot prevent every age-related cataract, but healthy eye habits can help reduce avoidable risk factors and support overall eye health.

Consider:

• Getting regular comprehensive eye examinations.
• Managing diabetes and other long-term health conditions appropriately.
• Wearing sunglasses that provide UV protection when outdoors.
• Avoiding smoking.
• Using protective eyewear when there is a risk of eye injury.
• Taking prescribed medicines, including steroids, only as directed.
• Having persistent changes in vision assessed rather than repeatedly changing glasses without an eye examination.

Regular eye examinations are especially useful because cataracts are not the only condition that can cause gradual vision loss.

When Should You See an Eye Specialist?

Make an appointment for an eye examination if you notice that one eye is becoming noticeably different from the other.

This is particularly important if you have:

• New or worsening blurred vision
• Increasing glare
• Difficulty seeing at night
• A sudden change in vision
• Persistent double vision
• A significant change in your glasses prescription
• Difficulty performing your usual activities

A cataract usually develops gradually. Sudden vision loss, flashes of light, a sudden increase in floaters, or a curtain-like shadow over your vision should not simply be assumed to be a cataract and requires urgent eye assessment.