Although many patients with diabetes experience little more difficulty during cataract surgery than the average patient, others suffer persistent inflammation, CME, or even rapidly progressive retinopathy postoperatively. As a result, the cleanest cataract procedure can be anything but routine in patients with diabetes.
In this article, several vitreoretinal surgeons pull from their experience to offer tips on how best to prepare for and manage these challenging patients. Although the presence of diabetes makes it impossible to avoid the problems associated with the disease entirely, anticipating their potential occurrence can lessen their impact.
THE PREOPERATIVE EXAMINATION
According to the surgeons consulted, the most reliable indicator of the postoperative outcome in patients with diabetes is the preoperative status of their retinopathy.
“It's amazing how often that's overlooked,” comments C.P. Wilkinson, MD, of Baltimore, Maryland, “and, if there's any doubt, … they ought to be referred to a retinal specialist.”
Adds Los Angeles surgeon Edgar Thomas, “The biggest risk is missing proliferative diabetic retinopathy and having the eye bleed immediately postoperatively because of changes in intraocular pressure during cataract surgery so that the patient, not only has some blurred vision from potential macular edema, but has major vitreous hemorrhage” (Figure 1).
According to Mandi Conway, MD, FACS, of New Orleans, Louisiana, it's crucial that the patient's macula be as dry as possible before cataract removal. Laser treatment for diabetic macular edema helps the retinal pigment epithelial cells remove the fluid, she says. Without maximal treatment preoperatively, cataract surgery can result in massive capillary incompetence and, ultimately, perhaps in a permanent loss of vision, she asserts. Also important, she adds, is detecting the presence of capillary closure in the macula, or nonperfusion.
For these reasons, even if they do not appear to have much leakage, Dr. Conway advocates referring all patients with diabetes to a vitreoretinal specialist prior to cataract surgery for an angiogram and any necessary laser treatment. In specific, Karen Gehrs, MD, of Iowa City, Iowa, recommends that macular edema be resolved for 3 months and that proliferative disease have completely regressed prior to cataract surgery. When the cataract is too dense to allow photocoagulation, she recommends that a thorough retinal exam and laser treatment, as indicated, follow the cataract procedure in 2 to 3 days if the patient has active proliferative disease or active macular edema. Pretreatment is preferable whenever possible, however, she comments.
“Unfortunately, I've been involved as an expert witness in several cases in which patients got a delay in treatment of the retinopathy, because they had intercurrent cataract surgery,” says Dr. Thomas. “… [Diabetic retinopathy] doesn't come up overnight, so, if somebody 2 weeks after cataract surgery has some major diabetic complications, it's hard to say it wasn't there before, because usually it was.”
Assessing Visual Acuity
In addition to demanding extremely careful preoperative examinations and, oftentimes, preoperative laser treatment of the patient, the presence of diabetes also necessitates that cataract surgeons use different standards of visual acuity as indicators for surgery than they would in the average patient.
“[Don't] be too eager to do the diabetic cataract, because these eyes have a higher incidence of complications like CME than a normal eye,” cautions Dr. Conway. “While you might do a normal eye at 20/40, I might wait until 20/50 or 20/60 to do a diabetic, because, if that eye gets a retinal complication, there's no guarantee it's going to see better after surgery than before [it].”
San Francisco surgeon J. Michael Jumper concurs, commenting that it is usually wisest to wait for visual acuity to decrease to 20/60 in a patient with diabetic retinopathy. That number, he says, is “based on some studies that have shown in patients who have pre-existing retinopathy that they have a higher likelihood of having progression of their disease and that the chance of their final vision's being better than 20/50 is not as high as patients who aren't diabetic.”1,2
The Cause of Vision Loss
Dr. Gehrs acknowledges that, because a posterior subcapsular cataract usually obscures the view of the retina, sometimes the only way to assess a diabetic patient's retina is via cataract extraction. With a nuclear sclerotic cataract, it becomes more difficult to determine how much the cataract affects the patient's vision, she says. In such a case, Dr. Gehrs will turn to potential acuity meter testing in an effort to get a general sense of whether or not the patient's visual acuity will improve with cataract surgery, and she will, of course, obtain a fluorescein angiogram to look at the profusion of the macula and as a basis of comparison with previous angiograms. If the patient's circulation looks fairly good and she believes cataract extraction will improve his or her visual acuity, she will recommend the surgery, but, “if his whole macular circulation is wiped out, then, unless the cataract is quite dense, … [the patient is] probably not going to be helped with surgery.”
Dr. Jumper agrees, commenting that, oftentimes, “poor vision is mistakenly attributed to cataract in patients who are diabetics, in whom the real cause of vision loss is diabetic disease in their eye, like retinal changes, the diabetic retinopathy.” The importance of this differential diagnosis, he says, necessitates a thorough preoperative examination of the retina, particularly the macula.
Several of the retinal specialists stress the need for cataract surgeons to educate patients preoperatively about their higher risk for complications, because they have witnessed these individuals' deep disappointment after surgery.
“If you consider cystoid macular edema, which is probably the most common complication following uncomplicated cataract surgery, it's more common in patients with diabetes, even if they don't have retinopathy,” says Dr. Wilkinson. “I think the patients need to know that. I think it should be part of the informed consent.”
Reasonable expectations on the part of both cataract surgeon and patient make it far more likely that the latter will be happy postoperatively, comments Dr. Jumper. To that end, it's worthwhile to remember that the mindset of patients with diabetes echoes that of the lay public in general, Dr. Gehrs points out. They think that cataract surgery is quick and easy and that everybody's vision improves, she says.
“Their friends have gotten better,” she explains, “so they are disappointed when they have ... totally successful cataract surgery, but their vision isn't perfect.”
Waiting for 6 months after photocoagulation and resolution of edema in an appropriately counseled patient who has a reasonable potential for improvement does not spell an end to potential disaster. The following simple changes to the standard procedure can make an enormous difference.
In the patient with diabetes who requires bilateral cataract surgery, Mark E. Chittum, MD, of Colorado Springs, Colorado, advocates spacing out two unilateral procedures by 4 months. The delay, he says, allows enough time to ensure that no complications develop in the first operated eye due to worsening diabetic retinopathy, and it allows the cataract surgeon to make any modifications in the management of the second eye that are necessary to reduce the risk of its developing maculopathy postoperatively.
If a patient with a diabetic vitreous hemorrhage has a cataract so dense that the vitreoretinal surgeon cannot see through it to operate, Dr. Gehrs believes the ideal option for the patient is a combined procedure, during which the vitreoretinal and cataract surgeons remove the lens, perform the vitrectomy, and implant an IOL. For these patients in particular, a single surgery is preferable to multiple procedures whenever possible.
On the topic of lens material, all but one of the surgeons interviewed objected to the use of silicone, but none insisted on the implantation of a PMMA lens. In Dr. Gehrs' experience, silicone lenses have been more prone to deposit formation, and she has found that, in pseudophakic diabetic patients who later need vitreous surgery, these IOLs make air-fluid exchanges during vitrectomy difficult due to vision-obscuring condensation.
“You don't want a silicone lens, because, if we have to do a diabetic vitrectomy and peel a lot of membranes, the patient may need silicone oil in the eye, and the silicone oil will adhere to the silicone lens in droplets,” Dr. Conway further explains. “It never comes off, so the patient has little droplets that refract light and knock the vision down. You can't see in well, and the patient can't see out.”
While she prefers a PMMA lens, all of the vitreoretinal surgeons consulted consider the use of a foldable acrylic IOL acceptable in patients with diabetes. They did, however, express a desire that cataract surgeons implant the largest optic possible. One reason, says Dr. Jumper, is that a bigger optic “leaves more area for us to see in the eye to do laser or vitrectomy procedures.” To Dr. Gehrs, the benefits of small-incision surgery outweigh those of a PMMA lens. She advocates the use of a 6-mm optic (6.5-mm whenever possible), because she has found that diabetic patients receiving smaller optics frequently develop peripheral capsular fibrosis, which makes it difficult to treat the peripheral retina via laser or to see the peripheral retina during vitreous surgery.
Dr. Thomas differed from his colleagues by asserting that cataract surgeons should choose the lens that works best in their hands, rather than change their technique according to whether the patient might require silicone oil in the future.
“If a patient has severe diabetic retinopathy, ends up with multiple holes in the retina, and needs silicone oil, to remove a silicone plate haptic IOL is not a big deal, …” he counters. “Many times, these are not going to be very well-functioning eyes anyway, if you're going to silicone oil. Even though we've had it for a long time now, we use it mostly for eyes in which there is not a lot of other potential.”
One exception Dr. Thomas cites is a case in which the cataract surgeon knows the patient will need a vitrectomy for more than a simple diabetic vitreous hemorrhage; for example, the patient has traction detachment, which increases the chance that silicone oil will be required. He also refers to the potential case of a patient with enough nuclear sclerosis that intravitreal infusion will worsen the cataract intraoperatively. Dr. Thomas would have to remove the lens in such a patient, but leaving him or her aphakic would produce more problems with the anterior segment, he says. In this instance, he would advocate implanting an acrylic or PMMA lens, since it would be needed later.
Both Dr. Chittum and Dr. Jumper remark that small capsulotomies lead to later problems with visualization in patients with diabetes.
“Contraction of the anterior capsule leads to a very small opening, making adequate evaluation and management of diabetic retinopathy sometimes more difficult,” explains Dr. Chittum.
A larger capsulotomy, therefore, is preferable.
Dr. Conway adds that, because diabetic endothelial cells leak, the proteins and cells from the blood seep into the aqueous after cataract surgery, and this results in a significant inflammatory reaction immediately postoperatively. To combat this complication, she strongly recommends the use of dexamethasone 64 µg/mL in the infusion fluid during phacoemulsification, and she notes that this amount may be increased up to 128 µg/mL. She says that those anterior segment surgeons who have followed this advice have reported no inflammation on the first postoperative day, and she adds that this step is also important in eyes with uveitis.
Another important point about phacoemulsification, says Dr. Chittum, is that cataract surgeons need to exercise extra care to minimize trauma to the iris of patients with diabetes.
“Damage to the iris does not allow the pupil to dilate adequately postoperatively, making management of the diabetic maculopathy more difficult,” he says.
In a case of capsular rupture, Dr. Chittum advises against the use of an anterior chamber IOL, which he says increases a diabetic patient's risk for anterior segment inflammation and, therefore, postoperative macular edema. He recommends a sulcus-fixated IOL instead.
Dr. Wilkinson advises cataract surgeons to keep in mind that the retinopathy of a subset of patients with diabetes, even after pristine cataract surgery, will progress quickly, particularly in eyes with severe nonproliferative disease and in surgical cases that were complicated. He adds that postoperative dilation is particularly desirable in these patients, because it helps ensure that their pupils will be able to dilate well in the future.
In addition to CME, postoperative neovascularization of the anterior segment is a distinct possibility in patients with diabetes. Dr. Thomas points to anterior segment inflammation as a red flag for the potential growth of new blood vessels in the iris. It calls for a careful slit lamp examination and aggressive treatment, and a lack of response merits gonioscopy to look for vessels in the angle, he says. In patients with diabetic retinopathy who develop iris neovascularization, Dr. Gehrs suggests dilating the eye after performing gonioscopy in order to determine if the patient has “commensurate progression of retinopathy,” which often accompanies neovascularization of the angle. If the amount of peripupillary iris neovascularization is small, and several examinations over the next few weeks or months do not reveal any change in the iris neovascularization or development of neovascularization of the angle, retina, or optic nerve, she suggests simply following the patient. Larger amounts of or enlarging neovascularization, or neovascularization located in the angle, requires panretinal laser photocoagulation and close observation for the development of neovascular glaucoma.
The consensus among the surgeons consulted is that postoperative treatment should be aggressive in patients with diabetes. Because some patients who have had diabetic macular edema (DME) experience a recurrence of DME after cataract extraction, Dr. Gehrs often recommends prophylactically placing patients with a history of DME on Pred Forte (Allergan Inc., Irvine, CA) or Acular (Allergan) for 6 weeks postoperatively in an effort to prevent the occurrence of edema (Figure 2). Although she acknowledges the lack of any randomized clinical trials to support this practice, Dr. Gehrs states that she has observed a response to the topical steroid/nonsteroidal combination in patients who developed what appeared to be recurrent DME. Dr. Thomas also notes that clinical experience is beginning to show that combinations of nonsteroidal agents and steroids postoperatively effectively reduce retinal swelling. He himself has been impressed by the efficacy of alternating the two as often as four to six times per day in patients with edema.
Dr. Conway prefers that patients be referred back to her directly following cataract surgery for care. She will administer topical steroids, most often Pred Forte, every half-hour while awake over the course of 3 to 4 weeks, and then check the IOP. If there is no pressure spike, she will give a subTenon's injection of depot steroid every 4 to 6 weeks and reduce the administration of topical steroid drops to four times per day. She will treat any postoperative CME aggressively for approximately 6 months. If it doesn't resolve in that time, she alters her treatment to that for DME.
“The difference is that the CME treatment is aimed at interfering with the inflammatory cascade, and the diabetic macular edema treatment is aimed at laser, to increase the RPE pumping,” she explains. “… There is some new evidence that diabetic macular edema may, in fact, be inflammatory.”
It is for that reason that researchers are focusing on the use of steroids, including intravitreal triamcinolone acetonide, to interfere with the inflammatory component of DME.3 In a study soon to be published in the Journal of Cataract and Refractive Surgery, for instance, Dr. Conway and her fellow researchers looked specifically at the use of intravitreal triamcinolone for refractory pseudophakic CME. While excitement is growing among retinal specialists about its use for the prevention or reduction of macular edema, they remain divided as to the current appropriateness of its routine use.
Dr. Conway uses intravitreal triamcinolone regularly and has found it to be very effective. Drs. Thomas and Jumper also use the steroid, and Dr. Thomas has been impressed by its apparent degree of safety so far. Both surgeons emphasize that it is not their first choice of treatment, however.
“Because of the potential complications of its use, including glaucoma, … I think it should be reserved for a second- or third-line therapy, in that routine laser therapy should be tried first,” Dr. Jumper asserts. “But, I've seen amazing results from it.”
When asked to characterize the ideal patient in whom to use intravitreal triamcinolone, he describes a person who has already undergone laser therapy and has severe macular edema, but who has otherwise fairly good systemic control of his or her blood pressure and diabetes.
Both Dr. Wilkinson and Dr. Gehrs assert a need for controlled, prospective, masked, randomized trials of the use of the intravitreal steroid in the management of DME. Until such controlled trials establish a benefit of this type of therapy, Dr. Gehrs will not advocate this treatment routinely, but she does encourage cataract surgeons to refer patients for such trials if any are ongoing in their area.
Although cataract surgery in patients with diabetes is hard work, the rewards of a job well done are high, affirms Dr. Jumper.
“It can help us greatly in caring for their eyes, because a lot of times it gets to the point where we can't see the retina to treat it,” he says.
It is also quite important, Dr. Jumper adds, in patients who have lost vision after vitrectomy due to cataract: “They've oftentimes had a lot of laser [treatment]. They're sick patients. They may be on anticoagulation. A good, successful [cataract] surgery is just a godsend, and they forget about all the retinal surgery they've had. … They're just happy to get that good vision back.”
Mark E. Chittum, MD, is in private practice in Colorado Springs, Colorado. He may be reached at (719) 473-9595; firstname.lastname@example.org
Mandi D. Conway, MD, FACS, is Professor of Vitreoretinal Surgery and Uveitis, Tulane University. She may be reached at (504) 988-1122; email@example.com
Karen M. Gehrs, MD, is Associate Professor of Clinical Ophthalmology, University of Iowa. She may be reached at (319) 356-3185; firstname.lastname@example.org
J. Michael Jumper, MD, is in private practice in San Francisco, California. He may be reached at (415) 441-0906; RetinaSF@aol.com
Edgar Thomas, MD, is in private practice in Los Angeles, California. He may be reached at (213) 483-8810; email@example.com
C.P. Wilkinson, MD, is Chairman, Department of Ophthalmology, Greater Baltimore Medical Center, and Professor, Department of Ophthalmology, Johns Hopkins University. He may be reached at (443) 849-2645.
1. Jaffe GJ, Burton TC, Kuhn E, et al: Progression of nonproliferative diabetic retinopathy and visual outcome after extracapsular cataract extraction and intraocular lens implantation. Am J Ophthalmol 114(4):448-456, 1992
2. Jaffe GJ, Burton TC: Progression of nonproliferative diabetic retinopathy following cataract extraction. Arch Ophthalmol 106(6):745-749, 1988
3. Martidis A, Duker JS, Greenberg PB, et al: Intravitreal triamcinolone for refractory diabetic macular edema. Ophthalmology 109(5):920-927, 2002