Retina co-morbidity for the anterior segment surgeon
Consider the macula in pre-op cataract patients

Dr. Fung drawing Lucentis (Genentech, South San Francisco)
Dr. Fung consults with a patient
Dr. Fung performs an injection on a patient Source: Anne Fung, M.D.

Retina specialists offer advice on what to look for in order to attain best vision

Surgical complications arise, even in cataract surgery, which reportedly has one of the highest success rates. Yet despite all the various pre-op tests that are performed to ensure a successful operation—from measuring the eye and cornea to deciding on the best IOL fit—there are always potential problems that may be overlooked during the procedure, especially from the back of the eye.
The most common missed maculopathies that result in unhappy cataract patients are vitreoretinal interface abnormalities, such as epiretinal membranes and vitreoretinal traction, according to Michael D. Ober, M.D., Retina Consultants of Michigan, Southfield.
"Those are probably the most common disorders, but age-related macular degeneration closely follows," Dr. Ober said.
What is a clinician to do pre-op to ensure these retina issues won't pop up or cause vision problems after surgery? Three specialists spoke to EyeWorld about imaging the back of the eye and testing for visual acuity before going into the operating room.

Imaging the back of the eye

Dr. Ober said if there is suspicion from pre-op testing that a maculopathy may be present, "an OCT [optical coherence tomography] is probably the best screening tool. It will give you a lot of information. It's not going to help you with a patient who has dry macular degeneration that is not high risk or affecting the central vision, but it will give you a much better idea of the vitreoretinal surface, and it will also tell you whether there is subretinal fluid or macular edema that's pre-existing."
Suspicions may include a family history of the disease or if the patient's pre-op vision is not what the doctor would expect based on the level of cataract present.
The OCT can help clinicians determine beforehand if there's a macular pathology that could lower the patient's visual potential, whereas biomicroscopy or other tests might not pick up on those subtle changes.
"OCT evaluation is important to look at the structure of the retina, particularly the macula," said Elias Reichel, M.D., professor and vice chair of ophthalmology, Tufts University, Boston. "It is important as a pre-op assessment because even if our view is good, often we can miss subtle maculopathy. Occasionally, we find choroidal neovascularization from wet age-related macular degeneration that hasn't been seen before. In diabetic patients, we see diabetic maculopathy that's difficult to view through a visually significant cataract."
Dr. Reichel said assessing the macula in cataract surgery patients is "critical for a patient's high expectations."
"I don't think it makes a difference whether we're using a multifocal IOL or a standard IOL or a toric IOL," Dr. Reichel continued. "I think they all need careful macular evaluations. I think the questions are, can we account for visual acuity and can we be sure there is no underlying maculopathy that may explain part of the vision loss?"
Although it might not be feasible to have every cataract patient undergo OCT examination, especially if health insurance or Medicare won't pick up the tab, Dr. Reichel said it's important to have a good working relationship with a retina specialist or access to the device to keep track of changes in the back of the eye.
"In general, if you're a comprehensive ophthalmologist or do a lot of cataract surgery, I think it's good to document the structural changes in the macula," he explained. "It's good medicine because it's for documentation of changes, and we want to educate our patients and say, 'We're going to do cataract surgery. I expect this much improvement in vision, but there may be a problem that limits the improvement in vision, or there may be underlying pathology with the human eye that requires vitreoretinal intervention.'"

Vision's potential tested

Surgeons can use a potential acuity meter (PAM) test to estimate how much a cataract is affecting a patient's vision loss, as well as to assess the patient's potential visual acuity after surgery.
The test projects a Snellen chart onto the eye through a small "pinhole" in the cataract. A chart of letters or numbers is then imaged onto the macula to measure its acuity.
Prior to the PAM test, a doctor should examine the anterior segment to find the clearest areas of the cataract. The PAM mounts onto the slit lamp, and the background illumination should be used at a low level, according to the device's operating manual.
The microscopic beam of light is focused on the iris of the patient's right eye, and the operator moves the dot into the pupil while looking through the slit lamp. The patient then reads the lines of the chart as far as he or she can.
"When a difficult line is reached, it may be necessary to slowly move the light beam to other areas," the manual states. "Alternately, a new quadrant or even the center of the pupil may be slowly scattered. Further encouragement and repositioning of the beam should be made until the examiner is confident that the patient cannot read any smaller numbers or letters."
Clinicians remain divided on whether the PAM test is ultimately reliable.
"I find it relatively reliable. It does help differentiate patients, meaning a lot of patients do get that much better," said Anne Fung, M.D., Pacific Eye Associates, California Pacific Medical Center, San Francisco. "It is reflective of the post-cataract outcome in my experience."
Dr. Ober said he uses the PAM test, but he considers it "a rough test."
"There's a lot of things that could make a PAM give an underestimate of the vision," he said. "Rarely I've had it overestimate vision, although it's hard to tell if there wasn't some other factor that changed during the surgery. I think it's a rough estimate, but we can sometimes get better vision with a PAM in a patient who has macular edema than we could without the PAM, even after cataract surgery."
Dr. Reichel said he falls in the "not terribly reliable" camp when it comes to the PAM test.
"A negative PAM test doesn't necessarily mean we are going to have an unexpected poor visual result after cataract surgery," he cautioned. Still, he said, it is the "best test for determining visual acuity that's related to cataract, although if the patient has a maculopathy, his vision could still be poor, despite doing the test."

Editors' note: Drs. Fung, Ober, and Reichel have no financial interests related to this article.

Contact information

Fung: 415-923-3918,  annefungmd@yahoo.com
Ober: 757-622-2200, obermike@gmail.com
Reichel: 617-636-1648,  ereichel@tuftsmedicalcenter.org