Cataract Surgery in Diabetes

This growing patient demographic poses some special challenges.

By Steven Safran, MD

Given that people with diabetes are more likely to develop cataracts than the general population and that some of the interventions they may require (vitrectomy, intraocular injections of steroids) are cataractogenic by nature, it is clear that cataract surgeons need to be aware of the special issues involved in dealing with these patients.

The diabetes patient is more likely to have ocular surface disease,¹ endothelial dysfunction,² glaucoma,³ poorly dilating pupils⁴, pupils that come down during surgery,⁵ anterior capsule contraction,⁶ zonular instability or capsule damage due to previous vitreoretinal surgery, retinopathy motility disorders and stroke. Thus it is fair to say that in patients with diabetes, every part of the eye and the whole visual system really needs to be considered when planning cataract surgery, in ways that are not necessary in nondiabetic patients. Here is a review of what the surgeon needs to keep in mind.

Their Surgical Outlook is Actually Bright

Despite the above-mentioned factors, there is very good evidence that diabetes patients with cataracts benefit greatly from modern cataract surgery. While the risk of progression of retinopathy does exist with modern cataract surgery, it is much lower with small-incision phacoemulsification than it was in the past with ICCE and ECCE.⁷ In fact, the visual outcome for diabetics with mild or moderate retinopathy but no macula edema has been demonstrated to be the same as that for nondiabetics.⁸ It appears that patients who have cataract surgery before the onset of macula edema and neovascular changes are much less likely to have progression of retinopathy and complications related to the surgery. This brings into question the old paradigm of waiting as long as possible to do surgery on people with diabetes.

In fact, these patients may benefit from an earlier rather than later consideration of performing their cataract surgery. Performing surgery before the onset of macula edema and neovascular changes may make the surgery more straightforward and less likely to lead to complications than waiting until retinopathy and other problems already exist. This is especially true if the patient will require vitreoretinal surgery in the future, which may lead to compromised zonules, poor dilation and denser nuclei.

One recent study suggested that cataract surgery may in fact not lead to any progression of early retinopathy, but simply unmask retinopathy that lens opacities had previously hidden.⁹ If this were indeed the case, one could argue that earlier cataract removal may lead to better treatment of the retina problems that may occur and thus should be advocated.

Increasing the Odds for Success

With that in mind, diabetic patients with cataracts potentially clearly have much to gain from our surgery. So what are some of the things we can do to stack the odds in our favor?

■ IOL selection is key. The first factor to consider is implant selection. I believe it is important to temper the urge to use premium IOLs in “borderline” situations with diabetics for a number of reasons. Obviously, when dealing with a patient with florid retinopathy, it takes little common sense to know that a multifocal implant would be a poor choice; however, when the patient is younger and has no sign of retinopathy, the choice is less clear.

I believe that with every diabetic patient we need to do an actuarial analysis of the risk and benefit of using any premium lens. We need to ask not only if the lens will benefit the patient in the near future, but also if it could actually harm her or him down the road. A 40-year-old insulin-dependent diabetic with no retinopathy is very likely to develop issues in time. The lens that the patient is thrilled with today may become a liability in 10 or 20 years.

While I do believe that the choices of toric IOLs are usually clear cut and should be considered routine in diabetics with good visual potential and significant astigmatism, the use of presbyopia-correcting IOLs should be reserved and done in a very circumspect manor — especially because LRIs, by reducing cornea sensation, are more likely to worsen ocular surface problems in diabetics already at much greater risk of having them.

While I avoid multifocals in glycemic medication-treated diabetics altogether, I will consider a Crystalens in a well-controlled, non-insulin dependent diabetic with no ocular surface issues or retinopathy, a normal OCT, good HbA1C and no signs of autonomic dysfunction. In these cases I will usually place a CTR to give some protection for the patient down the road should vitreoretinal surgery be required. In general, I discourage the use of presbyopia-correcting lenses for diabetics at significant risk of having retinopathy or autonomic dysfunction in the future.

■ Consider the ocular surface. When performing implant calculations on diabetics, it is important to be aware that these patients may have ocular surface issues that interfere with accurate keratometry. Decreased cornea sensation and tear film abnormalities are more common in diabetes and can lead to bad data affecting IOL calculations before the surgery, as well as decreased vision after. It is important to recognize and treat these problems before surgery and to carefully review the keratometry before selecting the implant. Looking at the mires on topography or doing manual keratometry is an excellent screening measure for the ocular surface on these patients.

■ Take advantage of OCT. The advent of OCT has made it much easier to screen the retina on diabetic patients to better plan for surgery. OCT can be used to tell the surgeon whether there is clinically significant diabetic macula edema that needs to be treated prior to surgery. After surgery, it can be used to quantify CME if it occurs or DME if it progresses. OCT can help monitor the response to treatment of both DME and CME. The technology lets the surgeon know of atrophic macula changes responsible for decreased visual potential that may not be apparent on examination. Vitreomacular interface abnormalities, which can exacerbate diabetic maculopathy, can often only be appreciated with SD-OCT. Finally, OCT can also be used to look at the status of the optic nerve and help to localize the cause of unexplained poor vision in diabetics who are either being considered for or who have recently had cataract surgery.

What the Retina Reveals

The information you gain from OCT will be invaluable in determining how you proceed with surgery. Patients with diabetes who have no pre-existing DME have an excellent prognosis for an uncomplicated postoperative course after cataract surgery. In fact, one study demonstrated macular thickness changes after cataract surgery in diabetic patients with no retinopathy similar to those in nondiabetics.¹⁰ If diabetic macula edema is seen prior to surgery, it is important to treat it aggressively with focal laser — prior to surgery. Should PRP be required, the surgeon may wish to wait at least six months, and up to a year, to do cataract surgery. The risk of macula edema in patients who have had PRP within six months of cataract surgery was more than 50% in one study.¹¹

The surgeon should also consider the use of a pars plana triamcinolone or anti-VEGF agent at the time of cataract surgery. Many studies have now demonstrated potential for benefit in preventing both CME and progression to neovascularization with the use of one or both of these agents at the time of cataract surgery.^12,13 I will routinely inject triamcinolone through the pars plana at the conclusion of cataract surgery in patients with active retinopathy, and I have found this to make a huge difference in keeping the inflammatory “dog on the leash” and preventing complications. If the patient has glaucoma, I will sometimes add glaucoma surgery and inject steroids at the same time. Another option is to avoid the use of steroids and inject bevacizumab, particularly if the patient is a steroid responder and one wishes to avoid the need for glaucoma surgery.

If I see vitreomacular traction on the OCT prior to surgery with a macula edema pattern “pointing” at the vitreomacular traction (Figure 1), I am quick to refer the patient to a retina colleague. In my experience, these patients are at elevated risk for macula edema after cataract surgery in the region of the vitreomacular interface abnormality. The patient may benefit from pars plana vitrectomy or enzymatic vitreolysis with an agent such as microplasmin prior to cataract surgery.¹⁴

Figure 1: Diabetic macula edema with VM adhesion in area of edema. The VM interface may be exacerbating the focal edema here.

A Word About Expectations

In general, when there is retinopathy present it's a good idea to have a retina colleague working with you to help temper the high expectations for cataract surgery that patients may have with a second voice of caution and reason. No matter how many times you tell some diabetics they should not expect the smooth ride they may have heard some of their friends tell about, you will face questions that need to be answered again and again if a patient develops poor vision due to macula edema after surgery. It's a good idea to let these patients know that you are doing a “full court press” for them by getting a retina specialist involved in their care even if you are comfortable doing much or all of the treatment yourself.

Inflammation and Surgery

In performing the cataract surgery itself, it is important to do everything possible to reduce inflammation and protect endothelial cells. Diabetics have a higher rate of inflammatory mediators (Interleukin (IL)-2, IL-10, IL-12, interferon-alpha (IFN-a), and tumor necrosis factor (TNF-a) measurable in the aqueous prior to cataract surgery¹⁵ and will be more prone to develop problems related to inflammation as a result. They also have lower endothelial cell functional reserve, so a dispersive viscoelastic and nucleus disassembly techniques that reduce stress on the endothelium should be considered. Additionally, there is a greater risk of the pupil dilating poorly and coming down during surgery, so the surgeon needs to be prepared and willing to use iris retractors or pupil expanders during surgery.

Pre-treatment of the eye with topical NSAIDs is wise to reduce inflammation and prevent intraoperative miosis. One report showed that diabetics have a higher rate of anterior capsule contracture after cataract surgery.⁶ In my experience, the use of aggressive anterior capsule polishing virtually eliminates this risk by removing the lens epithelial cells most likely to undergo metaplastic transformation into myofibroblasts and cause this contraction.

In fact, I believe that the use of an anterior capsule-polishing instrument such as the “Singer Sweep” (Epsilon EP- 68) has done more to improve my cataract outcomes across the board than any other modification I've made in my surgery in the past few years. In my experience, this instrument reduces capsule contraction, provides better refractive outcomes due to a more stable and predictable effective lens position after surgery, and also reduces postoperative inflammation. I recommend meticulous anterior capsule polishing on all diabetics (Figure 2).

Figure 2: This is a well-controlled diabetic high myope six months after Crystalens implantation with CTR placement and aggressive LEC cleanup using the “Singer Sweep.” High axial myopes may have less risk of developing diabetic retinopathy.¹⁶ This patient had no retinopathy prior to surgery and developed no complications after.

Postoperative Management

After cataract surgery, I tend to be a bit more aggressive with topical steroids to control inflammation. Further, I believe all diabetics should have a dilated exam of the retina a few months after surgery and again six months later at a minimum to make sure there has been no development or progression of diabetic retinopathy. OCT is again useful here in managing these patients.

In patients who have had previous pars plana vitrectomy for diabetic retinopathy, you can expect poor dilation, dense cataracts and poor zonules to be the norm. Be prepared with Vision Blue, pupil expanders, CTRs and, if needed, alternative methods of fixating the implant, such as a Cionni ring or CTR in combination with a CTS sutured to sclera. I prefer scleral fixation to iris fixation in general in the absence of capsular support, but in cataract patients with diabetes I feel even more strongly rooted to this preference. I often will order a one-piece PMMA implant with holes in the haptics for suturing, such as the Alcon CZ70BD, as a backup lens to have on hand in these cases.

I avoid and advise against the use of anterior-chamber implants in patients who have had proliferative diabetic retinopathy requiring vitrectomy, but have had excellent success with scleral-fixated PCIOLs where required. In some cases with profound advanced retinopathy and severe cataracts, I have actually chosen not to place an implant when capsule support is lost at the time of surgery. Instead, I wait and evaluate the patient to see if she or he would even visually benefit from the use of an implant. In a few cases where the patient could see no better with aphakic correction than without it, a decision was made to simply leave the patient aphakic rather than expose her or him to the risk of suturing an implant at all.

If in doubt, it never hurts to come back and “fight another day” by returning to do a sutured secondary implant rather than risk a surgery you are not set up for, prepared for psychologically or even sure would benefit the patient (suturing a scleral fixated implant at the time of primary cataract surgery).

Keeping Expectations Realistic

In summary, it is important for the cataract surgeon to be aware of all the problems — from the ocular surface to the visual cortex — that can potentially affect patients with diabetes prior to recommending and planning surgery. It is crucial to educate these patients so that they have a realistic understanding of what their expectations can and should be.

The surgeon needs to be prepared before, during and after surgery for all these potential problems. We now have more tools than ever at our disposal to deal with this group of patients. As a result we can offer cataract patients with diabetes a better chance for visual improvement with our surgery than ever before. OM

References

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12. Salehi A, Beni AN, Razmjoo H, Beni ZN. Phacoemulcification with Intravitreal Bevacizumab Injection in Patients with Cataract and Coexisting Diabetic Retinopathy: Prospective Randomized Study. J Ocul Pharmacol Ther. 2011 Dec 1. [Epub ahead of print]
13. Udaondo P, Garcia-Pous M, Garcia-Delpech S, Salom D, Diaz-Llopis M. Prophylaxis of macular edema with intravitreal ranibizumab in patients with diabetic retinopathy after cataract surgery: a pilot study. J Ophthalmol. 2011;2011:159436. Epub 2011 Jun 16.
14. Stalmans P, Delaey C, de Smet MD, van Dijkman E, Pakola S. Intravitreal injection of microplasmin for treatment of vitreomacular adhesion: results of a prospective, randomized, sham-controlled phase II trial (the MIVI-IIT trial). Retina. 2010 Jul-Aug;30(7):1122-7.
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16. Lim LS, Lamoureux E, Saw SM, Tay WT, Mitchell P, Wong TY. Are myopic eyes less likely to have diabetic retinopathy? Ophthalmology. 2010 Mar;117(3):524-30. Epub 2010 Jan 19.

Steven G. Safran, MD, is in private practice in Lawrenceville, NJ. He is often referred difficult cataract cases that are complicated by retinal and other issues. He can be reached via e-mail at safran12@comcast.net.