Cataract surgery in patients with diabetes

Editorial Cataract Surgery in Patients with Diabetes Cataracts are disproportionately likely and their surgical correction more problematic in diabetic than in nondiabetic patients.‘,* Classic diabetic snowflake cortical opacities in young patients are rare. The vast majority of lens opacities in adult diabetics are nuclear sclerotic in type, but they do progress more rapidly and become symptomatic at a younger age than in nondiabetics. Insulin-dependent diabetics of longstanding have many times the risk of visually significant cataract and of undergoing cataract surgery as do nondiabetics of comparable age.‘,’ The preoperative cataract evaluation of a diabetic should include a potential acuity meter measurement, retinal assessment, and, when deemed necessary, a fluorescein angiogram. Liaison with the patient’s diabetologist regarding systemic problems and perioperative insulin management may be indicated. Pre-existing active retinopathy with macular edema portends poor visual results.4 Intraoperative difficulties include increased endothelial and iris pigment epithelial fragility, increased vascular leakage and inflammation, fibrin deposition, and increased vulnerability to operating microscope light injury. Postoperative problems may include increased risk of synechia formation and pupillary block, cystoid macular edema, rapid development of capsular thickening, and increased risk of vitreous hemorrhage.5 Many of these complications may hinder or prevent panretinal photocoagulation (PRP). Open-angle or neovascular glaucoma (NVG) coexisting with cataract pose management dilemmas.6 In NVG presenting acutely with pain, cornea1 edema, and moderate cataract, medications and serial paracenteses may provide media clearing sufficient for PRP. Many such eyes will demonstrate remarkable remission of iris and angle new vessels with improvement in intraocular pressure over subsequent weeks, permitting temporary deferral of glaucoma and cataract management decisions. Unremitting symptoms and media opacities in some cases of NVG may necessitate urgent pars plana vitrectomy with lensectomy and endolaser treatment of retinopathy. Recent studies have recommended delaying cataract surgery in diabetics, especially if macular edema is present, until visual acuity and function have dropped to levels below those usually considered an indication for surgery in nondiabetics.‘-” However, besides visual rehabilitation, a substantial percentage of diabetics require lens extraction to permit proper diagnosis and treatment of retinopathy. If the implications of ongoing prospective studies using intraoperative fluorescein angiography are verified, earlier cataract extraction in diabetic patients, before macular edema develops, may help stabilize retinopathy-associated macular edema and improve the long-term visual prognosis.‘” In cases with open-angle glaucoma, the need to visualize the optic disc and obtain visual fields may be additional indications for cataract surgery. A classification of diabetic retinopathy, including maculopathy, has been correlated with visual outcome in a recent meta-analysis of extracapsular cataract extractions that analyzed proportions of eyes achieving 20/40 or better central acuity.” In this study involving 546 procedures from 10 previously published series, outcomes were analyzed as belonging to 1 of 6 preoperative groups: eyes with no diabetic retinopathy (87% achieved 20/40 or better vision); eyes with nonproliferative diabetic retinopathy without clinical maculopathy (80% achieved 20/40 or better); eyes with quiescent proliferative diabetic retinopathy (57% achieved 20/40 or better); eyes with nonproliferative diabetic retinopathy with macular edema (41% achieved 20/40 or better); and eyes with quiescent proliferative diabetic retinopathy and macular edema (only 11% of these achieved 20/40 or better vision). No cases with active proliferative retinopathy, the most severely affected group, reached 20/40 visual acuity postoperatively. Besides developing practical methods to predict visual outcome after cataract surgery in diabetics, we encourage the comparative analysis of visual outcome using percentages of eyes that gain or lose 2 Snellen lines of vision. It may also be of interest to calculate the average vision improvement for the entire group or for subsets of eyes in various preoperative categories. Even minimal improvement in functional vision will be greatly appreciated by a nearly blind patient. A recent prospective study of 223 eyes, almost all followed for at least 6 months, has reassured us that phacoemulsification and posterior chamber lens implantation in diabetics do not aggravate retinopathy.” In this study, only one eye of each patient was operated on and the preoperative retinopathy was categorized as one of three grades: no clinically evident retinopathy; nonproliferative retinopathy; and proliferative retinopathy, all of the latter having previously undergone retinal laser treatment or cryotherapy. None of the patients had been previously treated for macular edema. All eyes received a one-piece polymethylmethacrylate (PMMA) lens in the bag via a capsulorrhexis, approximately 7 mm, using a scleral tunnel or clear corneal incision. Over the 6-month observation period, similar percentages of eyes (18.4% of eyes operated on and 14.4% of control eyes) without diabetic retinopathy at baseline developed background changes. There was no obvious adverse influence of capsular opening on retinopathy among eyes requiring neodymium:YAG (Nd:YAG) capsulotomy within the follow-up period. The incidence of focal or diffuse macular edema during follow-up was similar in both control and operated groups, and symmetrical between paired eyes in the majority of cases. A generally more favorable visual outcome in this series compared to those previously reported was attributed to preoperative treatment of retinopathy when indicated and the use of newer cataract surgery techniques, including phacoemulsification.” 949

Ophthalmology

Volume 105, Number

6, June 1998

A recent retrospective report is also reassuring with regard to the safety and efficacy of phacoemulsification in diabetic cataract surgery, noting fewer postoperative complications (with the exception of transient cornea1 edema) than in previous extracapsular series.12 In this consecutive series of 74 eyes with a mean follow-up of 2.61 years, there were no differences in visual outcome, progression of retinopathy, operative complications, or rates of capsulotomy between the study group and a control group of cases operated on previously with the extracapsular technique. In deference to the increased risk of endothelial injury, phacoemulsification power and time should be minimized and viscoelastic used to protect the endothelium. Covering the cornea with an opaque shield, dimming the light source, and using off-axis illumination when possible should minimize the risk of light injury to the retina. Because of visibility limitations due to adherence of silicone intraocular lenses (IOLs) to silicone oil during subsequent vitreous surgery, some authors strongly recommend one-piece PMMA or acrylic IOLs in any eye at risk for complicated retinal detachment, including eyes of diabetics. A relatively large diameter capsulorrhexis and large diameter optics facilitate subsequent peripheral retinal visualization. A 6.5-mm IOL provides a 39.7% larger optic area than does a 5.5~mm IOL. In theory, avoiding capsular tears may decrease the anterior diffusion of vasoproliferative factors. Meniscus IOLs have the advantage of creating less refractive disturbance when the vitreous cavity is filled with air, other gases, or silicone oil. In-the-bag IOL installation is desirable to minimize iris chaffing and pigment dispersion. The choice of incision for phacoemulsification, whether clear cornea1 or scleral pocket, may not impact visual outcome, although a scleral pocket incision has appeal as possibly creating less risk of defective wound healing and infection. The longterm likelihood of needing filtering surgery is higher in diabetic than in nondiabetic patients, making a temporal location for small incision cataract surgery desirable. Postoperative care should include frequent fundus examinations, fluorescein angiography when necessary, and prompt photocoagulation or supplementation of previous laser for any active retinopathy. Advances in diagnostic and treatment techniques, including the development of panfunduscopic lenses, have improved our ability to manage diabetic retinopathy. As the quality of life and lifespan of diabetic patients improve, ophthalmologists will increasingly confront cataract management decisions in these patients. The complexities involved in achieving the best possible long-term visual outcomes justify extra attention and continual modification of surgical approaches as new information becomes available about the unique characteristics of the diabetic eye. References I. Klein BEK, Klein R, Moss SE. Incidence of cataract surgery in the Wisconsin epidemiologic study of diabetic retinopathy. Am J Ophthalmol 1995; 119:295-300. 2. Krupsky S, Zalish M, Oliver M, Pollack A. Anterior segment complications in diabetic patients following extracapsular cataract extraction and posterior chamber intraocular lens implantation. Ophthalmic Surg 199 1; 22526-30. 3. Klein R, Klein BEK, Moss SE. Visual impairment in diabetes. Ophthalmology 1984;91:1-9. 4. Benson WE, Brown GC, Tasman W, et al. Extracapsular cataract extraction with placement of a posterior chamber lens in patients with diabetic retinopathy. Ophthalmology 1993; 100:730-8. 5. Ionides A, Dowler JGF, Hykin PG, et al. Posterior capsule opacification following diabetic extracapsular cataract extraction. Eye 1994;8:535-8. 6. Hykin PG, Gregson RM, Hamilton AM. Extracapsular cataract extraction in diabetics with rubeosis iridis. Eye 1992;6:296-9. 7. Harding JJ, Egerton M, van Heyningen R, Harding RS. Diabetes, glaucoma, sex and cataract: analysis of combined data from two case control studies. Br J Ophthalmol 1993;77:2-6. 8. Schatz H, Atienza D, McDonald HR, Johnson RN. Severe diabetic retinopathy after cataract surgery. Am J Ophthalmol 1994;117:314-21. 9. Pollack A, Leiba H, Bukelman A, Oliver M. Cystoid macular oedema following cataract extraction in patients with diabetes. Br J Ophthalmol 1992;76:221-4. 10. Dowler JGF, Hykin PG, Lightman SL, Hamilton AM: Visual acuity following extracapsular cataract extraction in diabetes: a meta-analysis. Eye 1995;9:313-17. 11. Wagner T, Knaflic D, Rauber M, Mester U. Influence of cataract surgery on the diabetic eye: a prospective study. Ger J Ophthalmol 1996;5:79-83. 12. Antcliff RJ, Poulson A, Flanagan DW. Phacoemulsification in diabetics. Eye 1996; 10:737-41. 13. Apple DJ, Federman JL, Krolicki TJ, et al. Irreversible silicone oil adhesion to silicone lenses. A clinicopathologic analysis. Ophthalmology 1996; 103:1555-61.

DON MINCKLER, MD Los Angeles, California ARTHUR ASTORINO, MD Newport Beach, California A.M. Peter HAMILTON, FRCS, FRCOphth London, England

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