A cataract is a common condition where the naturally clear lens of the eye becomes cloudy, which causes vision to become blurred, hazy, or less colorful. Cataract surgery is a highly successful procedure designed to treat this condition by removing the clouded lens and replacing it with an artificial intraocular lens, or IOL. While it is technically possible for a surgeon to operate on both eyes during the same visit, the standard and most frequently practiced approach involves staggering the procedures. The decision between operating on one eye or both simultaneously involves balancing patient convenience against specific safety considerations.
Understanding the Standard Approach
The current worldwide standard is known as Delayed Sequential Bilateral Cataract Surgery (DSBCS), which involves a planned separation between the two operations. The procedures are typically spaced apart by a period ranging from one to four weeks, though sometimes longer. This waiting period is primarily a safety measure that allows the first eye to fully stabilize and confirms the absence of any immediate complications.
Allowing the first eye to heal provides a chance to monitor for rare but serious issues, such as infection or unexpected inflammation. The outcome of the first surgery is also used for refractive adjustment. The final vision result provides the surgeon with real-world data to refine the intraocular lens power calculation for the second eye, aiming for the most accurate visual outcome. This staggered timing minimizes the risk that any error or unexpected reaction would affect both eyes simultaneously.
Simultaneous Bilateral Surgery
The procedure that addresses both eyes on the same day is called Immediate Sequential Bilateral Cataract Surgery (ISBCS). This approach is carried out during a single operating room session but is treated as two entirely separate surgical events. To maintain sterility and mitigate risks, the surgeon uses a completely new set of sterile instruments, gloves, gowns, and surgical solutions for the second eye.
ISBCS is considered a specialized approach reserved for patients who would benefit significantly from the single visit. This includes patients traveling long distances or those who have severe vision imbalances, known as aniseikonia, which can cause discomfort and depth perception issues. It is also preferred for patients who may struggle with anesthesia or logistics for two separate trips, such as those with certain physical or mental disabilities.
Risks Specific to Operating on Both Eyes at Once
The primary reason DSBCS remains the norm is the fear of bilateral complications, where a single adverse event could impact vision in both eyes. The most feared complication is bilateral endophthalmitis, a severe, sight-threatening infection inside the eye. While the risk of endophthalmitis in a single eye is extremely low—approximately 1 in 1,000 to 1 in 10,000 procedures—its occurrence in both eyes simultaneously could be devastating.
Another concern is Toxic Anterior Segment Syndrome (TASS), a non-infectious inflammatory reaction resulting from a contaminant in surgical solutions or improperly sterilized equipment. Since TASS is often linked to the surgical environment, an outbreak could affect both eyes if procedures are performed back-to-back. Delaying the second surgery prevents a potential equipment or solution issue from simultaneously affecting both eyes.
A specific risk involves the refractive outcome, which is the final prescription achieved after the IOL implant. If an unexpected refractive error occurs in the first eye of an ISBCS patient, the surgeon cannot adjust the IOL power for the second eye based on that result. This lack of adjustment could lead to both eyes having an inaccurate outcome, potentially requiring corrective lenses.
Recovery and Post-Operative Care
The general recovery process following cataract surgery is the same regardless of whether one or both eyes were operated on. Patients are instructed to use antibiotic and anti-inflammatory eye drops for approximately four weeks to prevent infection and control swelling. Initial vision may be blurry or hazy for a few days, and patients should avoid strenuous activity, heavy lifting, and environments with dust or dirt for several weeks.
Protective eye shields are often required, especially at night, to prevent accidental rubbing or pressure on the healing eyes. For patients undergoing DSBCS, the unoperated eye still functions during the recovery of the first eye, making daily life significantly easier. However, with ISBCS, the patient faces immediate bilateral restrictions, which is logistically challenging as they lose the use of both eyes for driving and other activities requiring clear vision.