A cataract is a clouding of the eye’s natural lens. This cloudiness progressively interferes with light transmission to the retina, causing blurred vision, faded colors, and increased glare sensitivity. Currently, surgery is the only effective treatment, involving the removal of the opaque lens and its replacement with a clear artificial lens, known as an intraocular lens (IOL). Modern cataract surgery is one of the most common procedures performed globally, consistently showing a high success rate. When both eyes are affected, the question of whether both eyes require surgery, and the timing of those procedures, becomes a primary concern.
Determining the Need for Cataract Surgery
The decision to proceed with cataract surgery is based on the degree to which the cataract impairs a person’s ability to perform daily activities. An ophthalmologist determines the need for surgery by assessing both objective visual measurements and the patient’s subjective experience of functional impairment. A common objective benchmark is a best-corrected visual acuity of 20/40 or worse in the affected eye.
This visual acuity threshold is not the only factor, as some patients experience significant disability even with better vision. A person may complain of difficulty driving, reading small print, or experiencing debilitating glare and halos, which are all signs of a functionally significant cataract. In cases where visual acuity is better than 20/40, specialized tests such as contrast sensitivity or glare testing, often using a brightness acuity test (BAT), can be employed to objectively confirm the reduction in visual quality.
Why Simultaneous Bilateral Surgery is Avoided
Operating on both eyes during the same session, known as immediate sequential bilateral cataract surgery (ISBCS), is generally not the standard of care. The primary reason for performing procedures sequentially is to mitigate the risk of a complication affecting both eyes. Any adverse event that occurs in the first eye is contained, leaving the second, unoperated eye unaffected.
The most serious concern is the rare but potentially devastating risk of bilateral endophthalmitis, a severe internal eye infection. If both eyes were infected simultaneously, the patient could face total vision loss. Surgeons also aim to avoid the risk of toxic anterior segment syndrome (TASS), which is an acute inflammatory reaction caused by a contaminant in the surgical solution or equipment. TASS could affect both eyes if the same instruments or solutions were used without proper separation.
To minimize risk, a delayed sequential approach is standard, allowing time to detect and address any complications in the first eye before proceeding with the second. Strict protocols for ISBCS exist, involving treating each eye as a completely separate surgery with entirely different batches of supplies and equipment. However, the possibility of a shared environmental or product-related issue remains a deterrent for most surgeons.
The Typical Timeline for Second Eye Surgery
Following the first procedure, the standard practice is to wait typically between one and four weeks before operating on the second eye. This waiting period allows the first eye to fully stabilize and begin its initial recovery.
A delay of several weeks also allows the ophthalmologist to accurately assess the refractive outcome of the first surgery, which is the final power and clarity of the implanted IOL. This information is used to fine-tune the lens calculation for the second eye, ensuring the best possible visual result. If the first eye had an unexpected refractive result, the second eye’s surgical plan can be adjusted accordingly.
Prioritizing the First Eye for Treatment
When a patient needs surgery on both eyes, the surgeon decides which eye to treat first based on clinical considerations. Often, the eye with the significantly worse vision is chosen first, as operating on it provides the greatest immediate visual benefit and functional improvement. Alternatively, some surgeons prefer to operate on the non-dominant eye first, allowing the patient to retain the best possible functional vision in their dominant eye during the initial recovery period. The final decision is a collaborative one, balancing the eye with the greatest need against the patient’s individual recovery tolerance and desire for a specific visual outcome.