Is It OK to Have Cataract Surgery on One Eye Only?

Having cataract surgery on just one eye is not only OK, it is extremely common and often the standard first step. Many people experience significant improvements in vision, safety, and quality of life after a single operation, and some never need or choose to have the second eye done at all. Whether stopping at one eye makes sense for you depends on factors like the difference in cataract severity between your eyes, your tolerance for any visual imbalance, and how your daily activities are affected. The decision is more nuanced than a simple yes or no, and the evidence on what you gain and what you might miss is worth understanding.

What First-Eye Surgery Delivers on Its Own

The practical gains from operating on one eye are substantial. A study tracking older women found that first-eye cataract surgery cut the rate of falls by about a third compared to a control group that did not have surgery, and fractures dropped from 8% in the unoperated group to 3% in those who had the procedure.¹ A separate study confirmed this, reporting a 33% reduction in falls after first-eye surgery and finding that poorer vision in the dominant eye was strongly linked to fall risk.² For someone whose daily life is limited by a dense cataract in one eye, that single surgery can be transformative.

Contrast sensitivity, which matters for things like reading signs in dim light and navigating uneven terrain at dusk, also improves after cataract removal. Research on eyes with cataracts showed that contrast visual acuity improved under both bright and low-light conditions after surgery, with the strongest correlation between surgical results and overall visual acuity occurring in dim settings.³ Even if that study focused on a specific retinal condition, the principle that removing a cloudy lens restores contrast applies broadly. If your worse eye is the one holding you back in everyday situations, fixing it alone can make a real difference.

Driving Gets Safer, Even After One Eye

Driving is one of the biggest practical concerns people have when weighing cataract surgery. The evidence here is encouraging for single-eye procedures. In a driving simulator study, crash and near-crash rates fell by about 36% after first-eye surgery and by 47% after the second eye was also done.⁴ That means the first operation captured a large share of the safety improvement, and the second added a smaller but still meaningful further benefit.

A real-world analysis of motor vehicle crashes found an even more dramatic pattern: first-eye surgery was linked to a 61% reduction in crash frequency, while second-eye surgery added a further 23% reduction on top of that.⁵ These numbers flip a common worry on its head. Rather than asking whether one-eye surgery is “enough” for safe driving, the data suggest that first-eye surgery is where most of the safety gains live. Second-eye surgery helps, but the leap from pre-surgical vision to one operated eye is far larger than the leap from one operated eye to two.

The Gap Period and Visual Imbalance

If you do plan to eventually have both eyes done, the time between the first and second surgery can be awkward. Your operated eye now has a clear artificial lens, while the other still has its cloudy natural lens. That mismatch can create a noticeable difference in image brightness, color perception, and focus between the two eyes. Patients who went through delayed sequential bilateral surgery reported visual imbalance, difficulty driving, and a general sense of things not matching up during the gap period.⁶ Many of those patients said the waiting time between surgeries should be shortened.

The imbalance is more than just subjective discomfort. When the two eyes have meaningfully different refractive power, a condition called aniseikonia can develop, where each eye perceives images at slightly different sizes. Research on patients with significant preexisting differences in eye length found that if the surgeon aims for perfect focus in the operated eye, the resulting image-size difference can reach 4% or more, which is enough to cause visual discomfort and interfere with how the brain fuses the two images.⁷ The good news is that surgeons can plan for this. When only one eye is being operated on, the lens power can be chosen to minimize the mismatch rather than to aim for theoretically perfect vision in the surgical eye alone.

One study comparing bilateral and unilateral implantation of multifocal lenses found that image-size differences at both distance and near were significantly less after both eyes received lenses than after just one eye did.⁸ This does not mean unilateral surgery is a bad idea, but it does mean the surgeon needs to think carefully about the target refraction when only one eye is being treated.

Depth Perception After One Versus Two Eyes

Stereopsis, the fine depth perception that comes from both eyes working together, does improve after first-eye cataract surgery, but it improves more after both eyes are done. A randomized controlled trial found that both groups (one eye and two eyes operated) showed better stereopsis scores after surgery. However, at the end of the study, patients who had both eyes done showed significantly better fine depth discrimination than those who had only one.⁹

How much this matters depends on your life. If you are an active driver, play sports that require judging distances, or have a job that demands precise hand-eye coordination, the better stereopsis from bilateral surgery is worth pursuing. If you are primarily concerned with reading, watching television, and general mobility, the depth perception from one operated eye plus one reasonably functional fellow eye is usually sufficient. The brain is remarkably good at using monocular depth cues like relative size, shadows, and motion parallax to compensate for reduced stereopsis.

Satisfaction Scores Tell a Mixed Story

Interestingly, patient satisfaction does not always track perfectly with the objective measurements. A prospective study comparing monocular and binocular trifocal lens implantation found no statistically significant difference between the two groups in visual function scores or satisfaction questionnaire results, even though binocular implantation theoretically provides more consistent vision.¹⁰ The surgical eyes themselves performed similarly regardless of whether the other eye was also implanted.

This finding suggests that much of the satisfaction from cataract surgery is driven by the improvement in the worse eye, not by achieving perfect symmetry between both eyes. If your operated eye reaches good acuity and your fellow eye still functions reasonably well, you may not notice a difference in day-to-day satisfaction compared to having both done. The clinical measurements may detect a gap, but your lived experience might not.

Choosing a Lens When Only One Eye Is Being Done

Lens selection matters more when you are operating on just one eye, because whatever lens goes in has to play well with the natural lens still in the other eye. Standard monofocal lenses targeted for distance are the simplest choice and create the least potential for visual conflict. Premium lenses like extended depth-of-focus or multifocal models add complexity.

Research on an extended depth-of-focus lens mixed with either a monofocal implant or a natural lens in the fellow eye found no significant difference in corrected visual acuity at distance or near between the mixed groups and the bilateral implant group, and no group reported troublesome visual disturbances like halos or glare.¹¹ Separately, a study evaluating a “mix and match” approach with two different types of multifocal lenses reported good binocular acuity at all distances.¹² In short, the fear that a premium lens in one eye and a different optical system in the other will create havoc is not well-supported by the evidence, provided the surgeon plans the combination thoughtfully.

There are also situations where intentional mismatch is the goal. A case report described a patient with thyroid eye disease who had persistent double vision. The surgeon deliberately targeted significant nearsightedness in the operated eye to functionally suppress the second image. At six months, the patient reported resolution of the double vision and improved comfort.¹³ This kind of creative unilateral approach would not work if both eyes were being treated the same way.

Why Many People Stop at One Eye

A large proportion of cataract patients never return for the second eye. Studies from different countries show second-eye surgery rates around 20% to 30% within two years of the first operation.^{14 15} This means the majority of patients in these settings were living with one operated eye for at least two years, and many indefinitely.

The reasons are overwhelmingly practical rather than medical. A study examining factors behind delay found that the most common reasons were loss of work or income (33%), feeling the fellow eye still had good enough vision (24%), and lacking someone to accompany them to the hospital (19%). Fear and lack of awareness were not the primary drivers.¹⁶ The fact that a quarter of patients explicitly cited adequate vision in the other eye as their reason for not returning reinforces the point that one-eye surgery can feel like “enough” for many people.

Cost-Effectiveness of the Second Eye

From a health economics standpoint, both first-eye and second-eye cataract surgery are considered among the most cost-effective procedures in all of medicine.¹⁷ But the incremental value of the second eye is smaller than the first. One analysis estimated that second-eye surgery produced about 0.92 additional quality-adjusted life years per patient at a cost of roughly $2,727 per quality-adjusted year gained, which is well below thresholds used to define good value.¹⁸ A UK study of older women found a less favorable ratio over a one-year trial period, but when modeled over a patient’s expected lifetime, the cost per quality-adjusted year came down to about £17,300, still within accepted thresholds.¹⁹

If cost or access is a concern, these numbers are reassuring in both directions. Doing one eye is already a great investment. Doing the second eye remains cost-effective by standard measures but delivers a smaller additional bump in quality of life, so forgoing it is not a medical catastrophe.

Same-Day Bilateral Surgery as an Alternative

If you decide you want both eyes done but dread the in-between period, immediate sequential bilateral cataract surgery, where both eyes are operated on the same day as two completely separate procedures, has grown in acceptance. A Cochrane review found moderate-certainty evidence that refractive outcomes were no different between same-day and delayed bilateral surgery, and complication rates did not significantly differ either.²⁰ A separate systematic review confirmed comparable safety profiles between the two approaches, with some studies noting slightly higher patient satisfaction and faster overall recovery with same-day surgery.²¹ Same-day surgery also tends to cost less per patient overall, since it avoids duplicate facility and anesthesia fees. It does not eliminate the question of whether to do one or both eyes, but it does remove the gap-period problems as a factor in the decision.

When You Have Only One Functional Eye

A genuinely different situation arises when you are functionally one-eyed, meaning the fellow eye is already blind or severely impaired. Operating on your only seeing eye carries higher emotional and practical stakes, but it does not carry prohibitively higher surgical risk. A cohort study of 100 one-eyed patients found a 5% intraoperative complication rate, and 73% of patients achieved a final acuity of 20/40 or better.²²

However, another study found that the complication rate was significantly higher in one-eyed patients whose fellow eye had been lost due to a prior surgical complication, compared to those whose fellow eye was lost from non-surgical causes. The overall surgical complication rate in the one-eyed group was about 15%, versus 4% in a control group with two functional eyes.²³ The elevated risk in the subgroup whose other eye was lost to surgery may reflect underlying anatomical factors that made both eyes more prone to complications. If you are in this situation, a thorough discussion with your surgeon about your individual risk profile is especially important.

Anesthesia Considerations for Older Adults

Most cataract surgeries are performed under local anesthesia with mild sedation, making them well-tolerated by the vast majority of patients, including those in their 80s and 90s. Still, age-related changes like reduced cardiovascular reserve, increased sensitivity to sedatives, and impaired respiratory function can raise the risk of complications such as blood pressure drops during the procedure and temporary confusion afterward.²⁴ For a frail older adult, undergoing one procedure instead of two means one exposure to sedation rather than two, which can be a valid reason to limit surgery to the more affected eye.

Children With Cataracts in One Eye

Unilateral cataract surgery takes on a completely different character in children. A child born with or developing a cataract in one eye faces deprivation amblyopia, where the brain essentially gives up on the blurry eye and wires itself around the clear one. This makes early surgery critical, but the visual outcomes remain challenging. A study of infants with unilateral cataracts found that the median final acuity in the affected eye was around 20/500, and nearly all developed strabismus.²⁵ Earlier surgery correlated weakly with better results, but outcomes have not dramatically improved over recent decades despite advances in technique.

Children operated on at older ages (2 to 7 years) tended to fare better, with 41% achieving acuity better than 20/40, fewer adverse events, and no cases of glaucoma in one study, compared to much higher complication rates in infants.²⁶ The key difference from adult surgery is that removing the cataract is only the beginning. Aggressive amblyopia treatment with patching and optical correction of the operated eye must continue for years. Choosing the target refraction also requires accounting for the child’s eye growth. Surgeons must factor in the child’s age and the fellow eye’s refraction to minimize long-term imbalance between the two eyes.²⁷

How the Brain Responds to Restored Vision

One of the more striking findings in recent years is that cataract surgery does not just fix the eye; it appears to reverse changes in the brain caused by prolonged poor vision. Research using brain imaging showed that within three months of cataract surgery, patients had significant functional improvements in brain regions related to both vision and cognition. By six months, grey matter volume in those regions had measurably increased, and brain function had become comparable to that of healthy controls who never had cataracts.²⁸ This recovery happened after unilateral surgery, suggesting that restoring clear input from even one eye is enough to trigger meaningful neurological remodeling. For older adults concerned about cognitive decline, this is an underappreciated benefit of not leaving a dense cataract untreated.