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Cataract and Other Diseases
The development of a cataract creates an additional challenge when you already have macular degeneration, diabetic retinopathy, glaucoma or retinitis pigmentosa. Your ophthalmologist must determine which condition is most responsible for your visual difficulties. Before you decide to have surgery, consider the interaction of cataracts with any other eye condition and the possibility that your postoperative vision may not meet your expectations.
Cataract and macular degeneration
There is no relationship between macular degeneration and the development of a cataract other than the fact that both are common in the aging eye and impair vision. Macular degeneration distorts central vision, but if you don't have a cataract you can rely on your peripheral vision to travel safely and to read with magnifying glasses. With the additional development of a cataract, peripheral vision also becomes blurry and reduces your ability to see.
Your optometrist or ophthalmologist will usually perform various tests (glare, contrast) and may evaluate your potential visual acuity with a special vision testing device called a potential acuity meter. If these tests show that the cataract contributes significantly to your visual difficulty, then the removal of the cataract will restore your peripheral vision to its former clarity.
However, cataract surgery won't change the visual difficulties caused by macular degeneration. You will most likely continue to benefit from magnifiers for reading, and your eye doctor will suggest sunglasses to protect your eyes from ultraviolet light. The risk of cataract surgery (extracapsular or phacoemulsification)is the same whether or not macular degeneration is present. However, in cases of "wet" macular degeneration (where fluid or blood collects under the retina), there have been instances of macular hemorrhage weeks or months after cataract surgery. Although there is no proven relationship between the procedure and the hemorrhage, ophthalmologists may be more conservative in recommending surgery in this situation. With the advent of intraocular injections for "wet" AMD, the risk factor of hemorrhage is considerably reduced.
Cataract and diabetic retinopathy
Most people with diabetes eventually develop cataracts. With a cataract, your vision may be blurry for distance and for near objects, especially reading. But, just as importantly, your ophthalmologist's view into the eye is also hazy or cloudy, so that details of the blood vessels, retina or optic nerve aren't clear. Cataract surgery is often recommended so that the ophthalmologist may have an unobstructed view of the retina in order to observe and treat the retinal changes that often occur with long-term diabetes. People with diabetes can undergo a successful surgical procedure. However, the visual results depend on the health of the retina. Once a clear view of the retina is possible after surgery, the final visual outcome depends on the type of further retinal treatment the ophthalmologist considers necessary. Your doctor will recommend sunglasses to protect your eyes from ultraviolet light and, if appropriate, optical devices may be prescribed to help make the most of your vision.
Cataract and glaucoma
People with glaucoma are more likely to get a cataract soon after an acute attack of narrow angle glaucoma. However, in long-standing cases of chronic glaucoma, a cataract usually develops slowly, resulting in blurred reading vision. The recommendation to do surgery is more complex because other considerations influence the doctor's decision: adequate control of eye pressure, size of the visual field and the history of previous laser or filtering surgery to reduce pressure within the eye. If the pressure within the eye (intraocular pressure) can't be controlled, the ophthalmologist may have to consider a combined procedure, such as cataract removal plus a filtering operation.
People with glaucoma are accustomed to having their peripheral or side vision (visual field) checked periodically because one of the long-term effects of glaucoma is gradual loss of peripheral visual field. If peripheral vision decreases enough to cause tunnel vision, there's a possibility that cataract surgery, although technically successful, may result in further field or vision loss. This loss is due to subtle changes in the blood circulation during surgery. The ultimate visual result depends on the degree of damage to the optic nerve from the glaucoma. Corrective lenses and sunglasses assure the best possible result.
Finally, previous glaucoma filtering surgery makes cataract removal somewhat more technically difficult. The ophthalmologist has to select an area away from the filtering procedure for the incision, and deal with a small pupil and possibly weak zonules that normally support the lens capsule. Occasionally, in the latter situation, the entire lens including the capsule is removed and the implant sutured onto the iris. When possible, second opinions from a glaucoma specialist are suggested prior to cataract surgery so that you are well-informed about the possible risks as well as the potential benefits.
Cataract and retinitis pigmentosa
People with retinitis pigmentosa (RP) often experience visual impairment in youth or in their early adult years from the retinal disease, which gradually constricts or damages the outer or peripheral field of vision. In addition, cataracts may begin to form at a relatively early age, often during the 30s or 40s. The cataracts typically seen in RP are posterior subcapsular, that is, a small opacity in the center of the back capsule of the lens. The opacity may remain the same size for years, but its effect on vision, which may be negligible in the early stages of RP, may eventually interfere with sight as the peripheral field constricts.
The question ultimately arises about timing of cataract surgery. Traditionally, surgery has been postponed because of the small opacity in an otherwise clear lens. However, the decision to operate is related as much to the cataract as it is to the area of the central field. If the field is less than 10 degrees, the opacity may interfere markedly with visual acuity. At this stage, the lens should be removed and replaced with an implant lens. The presence of RP has no effect on the choice of surgical procedure (extracapsular extraction or phacoemulsification) or the rate of healing.
The visual results are gratifying in that the person now has clarity within the limited field. Ultraviolet protective lenses and reading glasses are prescribed after the surgery. The ultimate visual result depends upon the health of the macula.
Cataract and stroke
For people who have had a stroke, the decision to proceed with cataract surgery depends mostly on the individual's underlying medical conditions. A person with uncontrolled diabetes, hypertension, or someone with a history of cardiac failure may not be a good candidate for surgery. The ophthalmologist will generally consult with the internist or cardiologist to obtain background information as well as provide information about the eye problem. Ultimately, the person's internist or cardiologist should make the decision.
Cataract and previous retinal detachment surgery
As a complication of extensive or multiple retinal detachment surgical procedures, the lens of the eye may become opaque requiring cataract surgery. In addition, people who have had successful repair of a retinal detachment may develop a cataract in later years. In these situations, questions of timing, safety and type of procedure must be addressed. The theoretical danger of redetaching the retina is remote with the improved technology of both extracapsular surgery and phacoemulsification. Careful observation of the surgical site of the previous surgery through a widely dilated pupil is recommended. Many ophthalmologists prefer an extracapsular extraction in these situations. However, if the ligaments (zonules) that hold the lens in place are normal, phacoemulsification can be done.
By Eleanor E. Faye, MD, FACS; Bruce P. Rosenthal, OD, FAAO; and Carol J. Sussman-Skalka, CSW, MBA