Cataract surgery is one of the safest and most commonly performed operations in medicine, but it is not risk-free. Serious complications occur in a small percentage of cases, and minor side effects are more common than many patients expect. The type and likelihood of complications depend on factors ranging from the density of your cataract and the anatomy of your eye to medications you take and systemic diseases you may have. Understanding these risks in practical terms helps you prepare for what to watch for before and after the procedure.
What Happens During Surgery That Can Go Wrong
The most significant intraoperative complication is a tear in the posterior capsule, the thin membrane that holds the natural lens in place and later supports the artificial lens implant. When this membrane ruptures, the gel-like vitreous inside the eye can come forward into the surgical field, a problem called vitreous loss. One study of over 760 eyes found an overall vitreous loss rate of about 8%, though this was heavily influenced by surgeon experience: residents had a rate roughly five times higher than fellows.1PubMed Central. Risk Factors for Posterior Capsule Rupture and Vitreous Loss during Phacoemulsification In large national databases and experienced surgeons’ hands, the rate is considerably lower. Risk factors that increase the chance of capsule rupture include older age, small pupils, dense cataracts, a history of eye trauma, and a condition called pseudoexfoliation, where flaky protein deposits weaken the structures that hold the lens in place.2PubMed Central. Risk factors for posterior capsule rupture in mature cataract surgery: A study of 1302 cases
The timing of capsule rupture matters for how it is managed. A large study found that about 60% of posterior capsule ruptures happen during the main ultrasound step that breaks up the lens, roughly a quarter occur during the irrigation and aspiration phase that follows, and smaller fractions happen during lens implantation or later steps.3Eye. Timing of posterior capsular rupture during cataract surgery If a piece of the cataract drops into the back of the eye during a capsule rupture, a second surgery by a retinal specialist may be needed to retrieve it.4PubMed. Management of retained lens fragments after cataract surgery with and without pars plana vitrectomy
Floppy Iris Syndrome and Medications to Mention
If you take or have ever taken tamsulosin, a medication commonly prescribed for an enlarged prostate, your surgeon needs to know. Tamsulosin causes a condition called intraoperative floppy iris syndrome, where the iris billows, constricts unexpectedly, and tends to prolapse toward the surgical instruments. This occurred in roughly 2% of a cataract surgery population in the study that first identified the link.5PubMed. Intraoperative floppy iris syndrome associated with tamsulosin Other medications in the same class of alpha-1 blockers can cause similar behavior, though tamsulosin has the strongest association.6PubMed. ASCRS White Paper: clinical review of intraoperative floppy-iris syndrome
The critical point is that stopping the medication before surgery does not reliably prevent floppy iris syndrome. The changes to the iris muscle appear to persist even after the drug is discontinued. Surgeons who know about the history can use pupil-expanding devices and modified techniques that reduce the risk of complications. The problem comes when patients do not mention the medication or when it does not appear in their medical records. This is one of the most preventable sources of surgical difficulty in cataract surgery, and it hinges entirely on disclosure.
Infection After Surgery
Endophthalmitis, a severe infection inside the eye, is the complication patients fear most. The good news is that modern prevention strategies have pushed the rate remarkably low. Injecting antibiotics directly into the eye at the end of surgery has become standard practice in many countries, and a meta-analysis of over five million procedures found that this approach reduced endophthalmitis risk by about 69% compared to no antibiotic injection.7AJO International. Effectiveness of intracameral antibiotics in reducing postoperative endophthalmitis risk after cataract surgery: A meta-analysis One analysis estimated that about 2,500 patients need to be treated with intracameral antibiotics to prevent a single case of endophthalmitis, which gives you a sense of how rare the infection already is.8PubMed. Intracameral antibiotics during cataract surgery: efficacy, safety, and cost-benefit considerations
When endophthalmitis does occur, it typically presents within the first few days after surgery with rapidly worsening pain, redness, and vision loss. It requires emergency treatment, usually involving injection of antibiotics directly into the eye cavity and sometimes a surgical procedure called a vitrectomy. Outcomes are better the sooner treatment begins, which is why any sudden deterioration after cataract surgery warrants an urgent call to your surgeon.
Toxic Anterior Segment Syndrome
A condition that can mimic infection but has a completely different cause is toxic anterior segment syndrome, or TASS. This is a sterile inflammatory reaction, meaning there are no bacteria involved. It typically shows up within the first 12 to 48 hours after surgery with decreased vision, corneal swelling that extends from edge to edge, and inflammation in the front of the eye.9PubMed Central. Toxic anterior segment syndrome (TASS): A review and update The causes are wide-ranging: residue from sterilization chemicals on instruments, preservatives in solutions, contaminants in irrigation fluids, or even degraded viscoelastic material. In over half of reported cases, the exact trigger is never identified.10PubMed Central. Toxic anterior segment syndrome-an updated review
Distinguishing TASS from endophthalmitis is critical because the treatments differ. TASS generally responds well to aggressive steroid drops, while endophthalmitis requires antibiotic injections. TASS tends to appear sooner after surgery and causes more prominent corneal swelling than a typical infection. When outbreaks of TASS occur at a surgical center, they often affect multiple patients in a short period, which is a telltale sign of a contamination source in the operating facility rather than a patient-specific problem.
Posterior Capsule Opacification
The most common delayed complication after cataract surgery is posterior capsule opacification, sometimes called a “secondary cataract” although it is not actually a new cataract forming. After the original lens is removed and replaced with an artificial one, the remaining capsular bag can develop cloudy cell growth on its back surface over months or years. This is the most frequent long-term issue patients face.11PubMed Central. An Overview of Nd:YAG Laser Capsulotomy
The fix is straightforward: a quick laser procedure called YAG capsulotomy creates an opening in the cloudy membrane, restoring clear vision. It takes a few minutes, is done in the office, and has a high success rate. The type of artificial lens implanted can influence how capsule opacification develops afterward. In one study, eyes with acrylic lenses showed no worsening after the laser treatment, while some eyes with hydrogel lenses experienced complete closure of the laser opening, requiring retreatment.12PubMed. Influence of intraocular lens material on regeneratory posterior capsule opacification after neodymium:YAG laser capsulotomy Modern lens designs with sharp-edged optics have significantly reduced the rate of capsule opacification compared to older designs, though they have not eliminated it entirely.
Swelling in the Macula
Cystoid macular edema, or swelling in the central part of the retina, is another complication that can emerge weeks after surgery. You may notice blurry or distorted central vision when reading or looking at faces. The standard first-line treatment is anti-inflammatory eye drops, typically nonsteroidal anti-inflammatory drugs alone or combined with steroid drops.13PubMed Central. Incidence, Pathogenesis, Risk Factors, and Treatment of Cystoid Macula Oedema Following Cataract Surgery: A Systematic Review Most cases resolve with topical treatment. When drops do not work, injections of steroids around or behind the eye have shown significant improvement, especially in stubborn cases.
People with diabetes face a higher risk of macular swelling after cataract surgery. A systematic review and meta-analysis found that diabetic retinopathy progression was about 46% more likely after cataract surgery compared to the fellow eye that did not have surgery, and the risk of progression to sight-threatening complications like clinically significant macular edema or proliferative disease was roughly 84% higher.14PubMed. Incidence and Progression of Diabetic Retinopathy After Cataract Surgery: A Systematic Review and Meta-Analysis For patients who already have diabetic macular edema before surgery, the risk of worsening or recurrence afterward is considerably elevated.15PubMed Central. Optimizing treatment for diabetic macular edema during cataract surgery This does not mean diabetic patients should avoid cataract surgery, which generally improves their vision substantially. But it does mean closer monitoring afterward, especially in the first few months.
Retinal Detachment Risk
Cataract surgery modestly increases the long-term risk of retinal detachment, and this risk is amplified in people with high myopia (severe nearsightedness). In very highly myopic eyes, one study found retinal detachment in 8% of eyes that had cataract surgery compared to about 1.2% of similar eyes that had not.16PubMed. Cataract surgery as a risk factor for retinal detachment in very highly myopic eyes The pattern of detachment also differed: in eyes that had surgery, posterior detachments were the most common type, while non-operated eyes more often had peripheral detachments.
Even in non-myopic patients, the risk of retinal detachment is slightly elevated in the years following cataract surgery compared to the general population. Symptoms of retinal detachment include a sudden increase in floaters, flashes of light, or a curtain-like shadow moving across your vision. These symptoms after cataract surgery require same-day evaluation, regardless of how long ago your surgery took place.
Unwanted Visual Phenomena After Lens Implantation
Many patients experience unexpected visual symptoms from the artificial lens itself, collectively called dysphotopsias. These come in two flavors. Positive dysphotopsias are extra light that should not be there: glare, halos, starbursts, streaks, or arcs of light, especially around point sources like oncoming headlights. Negative dysphotopsias are the opposite: a dark crescent-shaped shadow, usually in the side vision on the temple side, as though something is blocking part of the visual field.
The numbers are striking for how common these are early on. Up to about two-thirds of patients may notice positive dysphotopsias in the initial period after surgery, though this drops to around 2% who still have persistent symptoms at one year. Negative dysphotopsias affect up to roughly a quarter of patients initially but settle to somewhere between 0.1% and 3% by a year out.17PubMed Central. Dysphotopsias or Unwanted Visual Phenomena after Cataract Surgery Surgery to exchange or reposition the lens is needed in fewer than 0.1% of cases.
Lens design plays a significant role. Lenses with sharp square edges made from high-refractive-index acrylic material tend to produce more dysphotopsias than lenses with rounded edges made from other materials.18PubMed. Positive and negative dysphotopsia in patients with acrylic intraocular lenses The irony is that those same sharp-edged designs are better at preventing posterior capsule opacification. So there is a genuine tradeoff between reducing long-term clouding and minimizing unwanted light effects. Research into how off-axis light creates intense focal spots at the nasal edge of the lens has pushed manufacturers toward designs that try to balance both goals.19PubMed. Off-axis edge glare in pseudophakic dysphotopsia
Pseudoexfoliation and Why It Matters So Much
Pseudoexfoliation syndrome deserves special attention because it is common, frequently underdiagnosed, and makes cataract surgery substantially more complicated. In this condition, a dandruff-like material accumulates on the lens capsule and the fibers (zonules) that suspend the lens inside the eye, weakening them. Patients with pseudoexfoliation face poor pupil dilation during surgery, weak zonular support for the lens, and an elevated risk of the lens or lens fragments dropping into the vitreous.20PubMed Central. Cataract surgery in patients with pseudoex-foliation syndrome: current updates
In one study, 75% of pseudoexfoliation patients had poor pupil dilation during surgery, compared to about 12% of controls.21PubMed Central. Cataract Surgery and Possible Complications in Patients with Pseudoexfoliation Syndrome A large retrospective analysis from England confirmed that pseudoexfoliation patients were more likely to experience zonular dialysis, dropped lens fragments, postoperative corneal swelling, elevated eye pressure, and lens implant dislocation, and were more likely to need a second operation within 90 days.22Journal of Cataract & Refractive Surgery. Outcomes of cataract surgery in pseudoexfoliation syndrome in England: 10-year retrospective cohort study Surgeons use techniques like capsular tension rings and specialized iris-expanding devices to manage these cases, but the risk profile remains meaningfully higher than average.
Pseudoexfoliation can also lead to late lens dislocation years after an otherwise successful surgery. As the weakened zonules continue to degenerate, the entire capsular bag with the implanted lens can shift or fall out of position. One reported case involved dislocation occurring more than two years after surgery, requiring a complex vitrectomy procedure for removal.23PubMed. Surgical management of late dislocated lens capsular bag with intraocular lens and endocapsular tension ring If you have been diagnosed with pseudoexfoliation, long-term follow-up matters even after your surgery is considered successful.
Corneal Health and Endothelial Cell Loss
The cornea, the clear window at the front of the eye, relies on a single layer of cells on its inner surface to keep it clear by pumping fluid out. Cataract surgery inevitably damages some of these cells through ultrasound energy and fluid turbulence. The amount of corneal swelling on the first day after surgery strongly predicts how many of these cells have been permanently lost.24American Journal of Ophthalmology. Postoperative Corneal Swelling Correlates Strongly to Corneal Endothelial Cell Loss After Phacoemulsification Cataract Surgery For most patients, the remaining cells compensate and the cornea clears within days to weeks. But patients who start with a low cell count, such as those with a condition called Fuchs endothelial dystrophy, may develop persistent corneal swelling that can require a corneal transplant down the road.
This is one reason surgeons measure corneal cell counts before surgery in patients they suspect may be borderline. Dense, hard cataracts that require more ultrasound energy to break up tend to cause more cell loss than softer cataracts, adding another variable to surgical planning.
Autoimmune Disease and Wound Healing
Patients with autoimmune conditions like rheumatoid arthritis or Sjögren’s syndrome face a different set of risks. The corneal surface in these patients is often compromised by chronic dryness and inflammation, making it vulnerable to complications that healthy eyes rarely experience. In severe cases, the cornea can develop a sterile melt at the surgical wound site, where the tissue thins and threatens to perforate.25PubMed. Sterile corneal melting and necrotizing scleritis after cataract surgery in patients with rheumatoid arthritis and collagen vascular disease Necrotizing scleritis, a destructive inflammation of the white of the eye, is another rare but serious possibility.
A study of cataract surgery outcomes in patients with rheumatoid arthritis and Sjögren’s syndrome documented cases including a paracentral corneal melt and a case of endophthalmitis that resulted in complete vision loss.26PubMed Central. Post-Operative Complications After Cataract Surgery in Patients with Rheumatoid Arthritis and/or Sjögren’s Syndrome These outcomes are uncommon even in this population, but they underscore the importance of coordinating care between your ophthalmologist and rheumatologist. Optimizing control of the underlying disease before surgery, using preservative-free eye drops afterward, and monitoring closely for signs of wound-healing problems all help reduce risk.
Femtosecond Laser-Assisted Surgery
Femtosecond laser-assisted cataract surgery uses a laser to perform some of the steps that the surgeon would otherwise do by hand, including making the corneal incision, creating the circular opening in the lens capsule, and pre-fragmenting the cataract. One multicenter study found an overall complication rate of 1.8% for the laser-assisted approach compared to 5.8% for conventional surgery.27PubMed Central. Comparing the intraoperative complication rate of femtosecond laser-assisted cataract surgery to traditional phacoemulsification That sounds compelling, but the story is more complicated than a single comparison suggests.
A large meta-analysis pooling data from both randomized trials and observational studies found no significant differences in most major complications, including anterior capsule tears, corneal edema, macular edema, vitreous loss, or uncontrolled eye pressure. The laser approach actually showed higher rates of some complications unique to the laser step itself, including pupil constriction during the procedure, corneal surface defects, corneal haze, and small hemorrhages under the conjunctiva.28PubMed Central. Safety of femtosecond laser-assisted cataract surgery versus conventional phacoemulsification for cataract: A meta-analysis and systematic review Another meta-analysis limited to randomized trials confirmed no significant differences in overall complications, visual outcomes, or patient-reported outcomes.29Scientific Reports. Femtosecond laser-assisted cataract surgery versus conventional phacoemulsification cataract surgery: a meta-analysis of randomized controlled trials
The practical takeaway is that the laser can be a useful tool in specific situations, particularly in eyes where a very precise and circular capsule opening matters (such as when using premium multifocal or toric lens implants). But for the average patient, the laser adds cost without a clear safety advantage. The surgeon’s skill and experience remain a much stronger predictor of outcome than the technology used.
Getting the Prescription Right
One complication that does not involve tissue damage at all but frustrates patients enormously is a refractive surprise, ending up with a glasses prescription significantly different from what was planned. The artificial lens power is calculated from measurements of the eye’s length and the curvature of the cornea, but numerous factors introduce small errors that add up. Prior LASIK or PRK, an irregularly shaped cornea, dense cataracts that interfere with accurate measurements, or unusual eye anatomy can all throw off the calculations.30PubMed Central. Refractive Outcomes after Cataract Surgery Newer formulas and optical biometry devices have improved accuracy, but a residual refractive error requiring glasses is still the norm rather than the exception. Patients considering premium lens implants that promise reduced dependence on glasses should understand that the “error budget” in lens power calculations is tight, and the promised spectacle independence does not always materialize perfectly.
Eye Drop Compliance After Surgery
An underappreciated source of complications is simply not using postoperative eye drops correctly. After cataract surgery, patients are typically prescribed antibiotic drops to prevent infection and anti-inflammatory drops to control swelling, often on a tapering schedule that lasts several weeks. Missing doses, stopping too early, contaminating the bottle tip, or confusing multiple drop bottles all increase the risk of preventable complications like infection, persistent inflammation, and cystoid macular edema.31PubMed Central. Factors of noncompliance with prescribed eye drops in patients undergoing cataract surgery
Some surgical centers have moved toward “dropless” cataract surgery, injecting long-acting antibiotic and steroid medications inside the eye at the time of surgery to eliminate the need for postoperative drops altogether. This approach can be especially helpful for patients with arthritis or other conditions that make squeezing a small bottle and aiming drops into the eye physically difficult. If you are worried about managing a complex drop regimen, ask your surgeon whether a dropless or reduced-drop protocol is an option for your case.