A secondary cataract, medically termed Posterior Capsule Opacification (PCO), is a common development that occurs months or even years following successful cataract removal surgery. This condition involves a clouding of the membrane that holds the artificial lens in place. Since the initial surgery is one of the most frequently performed procedures, PCO is considered its most common complication, affecting up to 20% of patients. A secondary cataract is a treatable condition that does not indicate a failure of the original procedure.
How Secondary Cataracts Form
The biological mechanism behind a secondary cataract starts with the eye’s natural healing response to the initial surgery. During cataract surgery, the natural lens is removed from its clear sac, called the lens capsule, and an artificial intraocular lens (IOL) is inserted into this sac. The posterior capsule is the thin membrane at the back of this sac that is intentionally left in place to support the new IOL.
PCO occurs when microscopic remnants of lens epithelial cells (LECs), which are not fully removed during the initial procedure, begin to migrate and multiply on the posterior capsule. This cellular proliferation and transformation cause the clear membrane to become opaque or fibrotic over time. As this tissue thickens, it prevents light from passing clearly through the IOL to the retina, leading to a gradual deterioration of vision.
This clouding of the capsule results in symptoms very similar to those of the original cataract. Patients may notice blurred or hazy vision, increased sensitivity to light, and difficulty seeing in low-light conditions. Seeing halos or glare around lights at night is also a common complaint.
Secondary Cataract vs. Primary Cataract
A secondary cataract is fundamentally different from a primary one. The primary cataract involved the clouding of the eye’s natural lens, which was completely removed during surgery. The artificial lens, or IOL, is made of a synthetic material like acrylic or silicone and cannot develop a cataract.
PCO is not a clouding of the artificial lens itself, but rather the formation of scar-like tissue on the posterior membrane left behind to hold the IOL. The IOL remains perfectly clear and functional, but the capsule behind it has become opaque due to the cellular growth. Understanding this distinction is important, as the artificial lens is permanent, and the clouding is limited to the surrounding support structure.
Treatment: YAG Laser Capsulotomy
The standard treatment for a secondary cataract is a quick, non-invasive procedure called YAG laser capsulotomy. The term “YAG” refers to the yttrium aluminum garnet material used in the specialized laser that performs the procedure. This treatment is typically performed in the ophthalmologist’s office and involves minimal preparation.
Before the procedure, the eye is numbed with drops and the pupil is dilated to give the surgeon a clear view of the cloudy capsule. The YAG laser then emits precise, rapid pulses of energy that create a small, centered opening in the opacified posterior capsule. This action vaporizes the cloudy tissue, clearing the visual axis and allowing light to pass unobstructed to the retina.
The entire procedure is painless, usually taking less than five minutes, and is successful in restoring clear vision. Patients can typically resume their normal activities the following day. Vision often improves within 24 hours, and the treatment is considered curative because once the opening is created, the clouding cannot recur in that spot.