Cataracts cannot grow back after they are removed. But in some rare instances, a secondary (or new) cataract can form.
Secondary cataracts are sometimes also called after-cataracts. This is a condition that starts after a cataract surgery; the clinical name for this condition is posterior capsular opacification (PCO).
Like cataracts, symptoms of PCO include blurry vision, dimness of vision, and flares of light. This is caused by some lens epithelial cells (LECs) remaining in the capsule. They migrate down to the bottom and clump together, creating another cataract.
There may be additional steps your ophthalmologist can take to lower your risk of developing secondary cataracts.
What Are Secondary Cataracts?
If you develop cataracts and undergo cataract surgery, there is a small risk that you may develop another condition called secondary cataracts or after-cataracts.
The medical term for this condition is posterior capsular opacification (PCO). This occurs when the membrane around the lens capsule, which was not removed during cataract surgery and now contains the artificial lens or intraocular lens (IOL), becomes cloudy and begins to impair vision in a way similar to the cataract. Proteins change, and new cells begin to grow on the back of the capsule, obscuring your range of vision.
There are two basic types of secondary cataract: pearl and fibrous. Pearl PCO consists of normally differentiated LECs in the equatorial lens regions, whereas fibrous PCO involves abnormal propagation of LECs. A combination of these can be seen in some cases, but pearl is responsible for the majority of vision loss related to secondary cataracts.
When this condition is diagnosed, it will look like a wrinkled area on the back of the lens capsule, near the site of fusion of the top and bottom parts of the capsule. For PCO to develop, lens epithelial cells must:
- Proliferate, or grow more of the problem cell.
- Migrate, or move from one area to the problem area.
- Differentiate from the residual lens epithelial cells (LECs) into a problem type of cell.
This complication may be frustrating, but it typically takes months or, more often, years to develop after your first cataract surgery. Unfortunately, there is no way to know for sure who will develop secondary cataracts after surgery or how long it will take for this condition to progress.
For years, about half of people who had undergone cataract surgery developed secondary cataracts at some point; however, thanks to technological improvements, particularly in laser surgery, incidence rates have declined to between 4 and 12 percent of patients. Researchers are examining ways to prevent or reduce the risk of PCO developing, but it is still the most common complication after primary cataract surgery.
Some Conditions Increase the Risk of Secondary Cataracts
Some secondary cataracts have been linked to other diseases or steroid use. Factors that increase the risk of nonmodifiable secondary cataracts include:
- Younger people are at a higher risk.
- At a one-year follow-up, people who had diabetes had higher incidence of PCO development.
- Uveitis. This is an inflammation, redness, and itching of the middle part of the eye, called the uvea. People who have this condition are more likely to develop secondary cataracts after their cataract surgery.
- Myotonic dystrophy: This is an inherited disease that is part of the muscular dystrophy group, typically setting in during adulthood. It causes prolonged muscle contractions and difficulty relaxing certain muscle groups. Another symptom of this condition is cataracts, and people with myotonic dystrophy often require multiple capsulectomies after their initial cataract surgery.
- Retinitis pigmentosa: This is the breakdown and loss of cells in the retina, starting with trouble seeing at night and a loss of peripheral vision. People with this condition have a higher incidence of secondary cataracts.
- Traumatic cataracts: When the original cataract is caused by trauma to the head or eye, the person is much more likely to develop secondary cataracts after their original cataract surgery. At a three-year follow-up, one study found that incidence was as high as 92 percent.
Can Secondary Cataracts Be Avoided?
Although you cannot fully prevent secondary cataracts from forming, there are some steps your ophthalmologist can take to reduce the likelihood of this condition.
Additionally, research is learning more about why secondary cataracts are such a common side effect after surgery, so new medical approaches can treat this problem before it starts.
Some changes to how intraocular lenses (IOLs) are designed improve performance overall and reduce risk of side effects like secondary cataracts. For example, square-edged IOLs have been found to reduce the risk of PCO development, although they are not successful at preventing it. Changes to the surface chemistry of the IOL can also reduce the risk of PCO development. For example, UV/ozone treatment modifies the surface of the IOL with no safety issues involved in the materials.
Changes to the capsulotomy procedure may help to prevent secondary cataracts. Some researchers are investigating whether to leave the initial incision in the capsular bag open after implanting the IOL. This way, fluid in the eye can flow around the artificial lens, diluting and washing out remaining lens epithelial cells.
New research published in 2017 looked into the molecular causes of secondary cataracts, to reduce the risk of PCO development. Researchers found that old cells from the lens, after it is broken up and removed from the capsule, may remain on the epithelium of the capsule and begin to grow at the back. These cells may transform into two types of cells that can cause problems: lens fiber cells and myofibroblasts. The lens fiber cells will develop proteins called crystallins, causing light to scatter across the back of the eye as though it is being refracted through a crystal. Myofibroblasts create a matrix of molecules on the outside of the cell, wrinkling the lens capsule so vision becomes obstructed.
The study investigated why epithelial cells from the old lens differentiate into these two different types of problematic cells. TGF-beta, a growth factor chemical, becomes active in response to surgery because the area must be healed. Typically, this is a wound-healing response, but an excess of activated TGF-beta in the area can influence these lens cells to migrate into other places before they begin to grow into different types of cells.
Some drugs that suppress TGF-beta are being tested to determine if they can prevent the formation of secondary cataracts, but the Food and Drug Administration (FDA) has not approved prescription drug treatments to prevent this condition yet. The main medication being tested is a leukemia drug called rebastinib. TGF-beta is also active in some types of cancers, and suppressing it can stop tumor growth.
Again, these steps cannot altogether prevent the formation of secondary cataracts, but they can decrease the likelihood that they will develop.
How Are Secondary Cataracts Treated?
Although developing secondary cataracts is frustrating, treatment is relatively simple. It is a procedure called YAG laser capsulotomy, when a laser makes a smaller opening in the clouded capsule so light can shine through to the retina.
This surgery is painless and takes about five minutes, so less time even than the well-understood first cataract surgery. You may remain for about an hour in the eye doctor’s office to ensure that there are no immediate negative effects, especially increased eye pressure; afterward, you will experience improved vision within a few days.
The capsulotomy procedure typically works like this:
- Your eye will be numbed with special drops.
- A special laser will be pointed at the back of the lens capsule.
- When the laser turns on, it will create a small opening in the clouded part of the capsule.
- You can typically return to normal activities, including driving, as soon as the procedure is finished.
- You may receive prescription eye drops to be used for one week after the operation.
There are some complications associated with this procedure, including:
- Retinal detachment.
- Damage to the IOL.
- Partial dislocation of the IOL.
- Cystoid macular edema.
- Corneal edema.
- Increasing intraocular pressure.
- Hemorrhage in the iris.
- Worsened localized endophthalmitis, inflammation in the interior of the eye.
These risks are very low since the procedure does not take long, requires no incisions, and may not even require local anesthesia, depending on how your ophthalmologist will need to position the laser. Some of these side effects are more likely to happen if you are very nearsighted or have a pre-existing eye condition like glaucoma. However, if you develop any new symptoms — especially new “floaters,” seeing flashing lights, or a dark curtain moving up or down your vision — go back for a follow-up with your eye doctor immediately.
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Retinitis Pigmentosa. National Eye Institute (NIH).
Preventing Secondary Cataract and Anterior Capsule Contraction by Modification of Intraocular Lenses. (January 9, 2014). Expert Review of Medical Devices.
Researchers Focus on Preventing Secondary Cataract. (May 5, 2016). Optometry Today.
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