Diabetic macular edema: a review of past, present, and future therapies

Current management of diabetic tractional retinal detachments

Twenty-five percent of diabetes-related vision loss stems from complications of proliferative diabetic retinopathy (PDR). Panretinal photocoagulation has been the preferred treatment of high-risk PDR for decades and more recently intravitreal injections of drugs that inhibit the actions of vascular endothelial growth factor have become popular. But despite these treatments PDR may progress uncontrollably to advanced pathologies such as traction retinal detachments (TRDs), combined traction/rhegmatogenous retinal detachments (TRD/RRDs), vitreous hemorrhages, rubeosis iridis, and traction maculopathies, which produce mild-to-severe loss of vision. TDR have long been the most common indication for PDR-related vitreoretinal surgery. Vitrectomy surgery is indicated for recent (<6 months duration) TRD involving the macula, progressive TRD that threatens the macula, and recent data suggest that chronic macula-involving TRDs (>6 months duration) may also benefit. Combined TRD/RRD represents a particularly challenging surgical condition but advances in surgical instrumentation, dissection techniques, and post-operative tamponade have produced excellent success rates. The recent development of small-gauge vitrectomy systems has persuaded most surgeons to switch platforms since these appear to produce shorter surgical times and quicker post-operative recoveries. Pre-operative injections of bevacizumab are frequently administered for persistent neovascularization to facilitate surgical dissection of pre-retinal fibrosis and reduce the incidence of post-operative hemorrhages. Recent trends toward earlier surgical intervention and expanded indications are likely to continue as surgical instrumentation and techniques are further developed.

Preoperative photocoagulation reduces corneal endothelial cell damage after vitrectomy in patients with proliferative diabetic retinopathy

Proliferative diabetic retinopathy (PDR) is a severe complication of diabetes and is a leading cause of visual decline and irreversible blindness. So we designed this study to investigate retrospectively the effect of preoperative photocoagulation on corneal endothelial cells after vitrectomy in patients with PDR.The study included 52 eyes of 46 patients with PDR complicated with vitreous hemorrhage, who underwent vitrectomy. Patients were apportioned to a photocoagulation group (26 eyes/23 patients) or nonphotocoagulation group (26/23 patients), according to their history of preoperative photocoagulation. A specular microscope was used to assess the corneal endothelial cell density and percentage of hexagonal cells (PHC) before surgery, and at 1 week, 1 month, and 3 months after surgery.The cell density was lower 3 months after surgery in the photocoagulation group, but at 1 month in the nonphotocoagulation group, all cases were significantly different from the preoperative value (P < .05 or P < .01). One week after surgery, the mean cell densities between the photocoagulation and nonphotocoagulation groups were not statistically different (P > .05). However, the mean cell densities at 1 and 3 months after surgery in the photocoagulation group were significantly higher than those in the nonphotocoagulation group (P < .05). The PHC values in the photocoagulation group at 1 week and in the nonphotocoagulation group at 1 week, 1 month, and 3 months were much lower than their respective preoperative values (P < .05 or P < .01). More importantly, at 1 and 3 months, the PHC had recovered to preoperative values in the photocoagulation group, but not in the nonphotocoagulation group. As for cell density and PHC, they were both significantly higher 1 and 3 months after surgery in the photocoagulation group than in the nonphotocoagulation group (P < .05).Photocoagulation before vitrectomy reduces subsequent corneal endothelial cell damage in PDR patients.

Two-year results of a randomized trial of intravitreal bevacizumab alone or combined with triamcinolone versus laser in diabetic macular edema

PURPOSE

The purpose of this study was to report the 24-month findings of a randomized clinical trial comparing intravitreal bevacizumab (IVB) injection alone or in combination with intravitreal triamcinolone acetonide (IVT) versus macular laser photocoagulation (MPC) as a primary treatment for diabetic macular edema.

METHODS

The eyes were randomly assigned to 1 of the 3 study arms: the IVB group, patients who received 1.25 mg IVB; the IVB/IVT group, patients who received 1.25 mg of IVB and 2 mg of IVT; and the MPC group, patients who underwent focal or modified grid laser. Of 150 eyes (50 in each group) in the primary trial, 123, 119, and 113 eyes completed follow-ups at 12, 18, and 24 months, respectively. A total of 39 (78%), 36 (72%), and 38 (76%) eyes in the IVB, IVB/IVT, and MPC groups remained in the study within 24 months, respectively. Retreatment was performed at 3-month intervals whenever indicated. Data from a 24-month follow-up are presented. Changes in best-corrected visual acuity and central macular thickness up to 24 months were the main outcome measures in this study.

RESULTS

Retreatment was required in 37 (94.9%), 27 (75.0%), and 31 (81.6%) eyes, respectively, in the IVB, IVB/IVT, and MPC groups up to 24 months. The significant superiority of visual acuity improvement in the IVB group, which had been noted at Month 6, did not sustain thereafter up to 24 months, and the difference among the groups was not significant at all visits. However, the mean visual acuity improvement was greater in the IVB group than the other groups and in the IVB/IVT group compared with the MPC group. The reduction of central macular thickness was more in the IVB group in relation to the other two treatment groups; however, the difference among the groups was not statistically significant at any of the follow-up visits.

CONCLUSION

In terms of vision improvement, the significant superiority of the IVB over the combined IVB/IVT and MPC treatment that had been observed at Month 6 did not sustain up to 24 months. This means that although IVB treatment may be a better choice than two other options in short term, the magnitude of this beneficial effect diminishes over time.

A phase 2/3, multicenter, randomized, double-masked, 2-year trial of pegaptanib sodium for the treatment of diabetic macular edema

PURPOSE

To confirm the safety and compare the efficacy of intravitreal pegaptanib sodium 0.3 mg versus sham injections in subjects with diabetic macular edema (DME) involving the center of the macula associated with vision loss not due to ischemia.

DESIGN

Randomized (1:1), sham-controlled, multicenter, parallel-group trial.

PARTICIPANTS

Subjects with DME.

INTERVENTION

Subjects received pegaptanib 0.3 mg or sham injections every 6 weeks in year 1 (total = 9 injections) and could receive focal/grid photocoagulation beginning at week 18. During year 2, subjects received injections as often as every 6 weeks per prespecified criteria.

MAIN OUTCOME MEASURES

The primary efficacy endpoint was the proportion gaining ≥ 10 letters of visual acuity (VA) from baseline to year 1. Safety was monitored throughout.

RESULTS

In all, 260 (pegaptanib, n = 133; sham, n = 127) and 207 (pegaptanib, n = 107; sham, n = 100) subjects were included in years 1 and 2 intent-to-treat analyses, respectively. A total of 49 of the 133 (36.8%) subjects from the pegaptanib group and 25 of the 127 (19.7%) from the sham group experienced a VA improvement of ≥ 10 letters at week 54 compared with baseline (odds ratio [OR], 2.38; 95% confidence interval, 1.32-4.30; P = 0.0047). For pegaptanib-treated subjects, change in mean VA from baseline by visit was superior (P<0.05) to sham at weeks 6, 24, 30, 36, 42, 54, 78, 84, 90, 96, and 102. At week 102, pegaptanib-treated subjects gained, on average, 6.1 letters versus 1.3 letters for sham (P<0.01). Fewer pegaptanib- than sham-treated subjects received focal/grid laser treatment (week 54, 31/133 [23.3%] vs 53/127 [41.7%], respectively, P = 0.002; week 102, 27/107 [25.2%] vs 45/100 [45.0%], respectively, P = 0.003). The pegaptanib treatment group showed significantly better results on the National Eye Institute-Visual Functioning Questionnaire than sham for subscales important in this population. Pegaptanib was well tolerated; the frequencies of discontinuations, adverse events, treatment-related adverse events, and serious adverse events were comparable in the pegaptanib and sham groups.

CONCLUSIONS

Patients with DME derive clinical benefit from treatment with the selective vascular endothelial growth factor antagonist pegaptanib 0.3 mg. These findings indicate that intravitreal pegaptanib is effective in the treatment of DME and, taken together with prior study data, support a positive safety profile in this population.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Pegaptanib Sodium versus Pegaptanib Sodium Combined with Macular Laser Photocoagulation or Laser Alone for Diabetic Macular Edema

Purpose. To report the outcomes after primary intravitreal pegaptanib sodium in patients with diabetic macular edema (DME). Methods. We conduced a retrospective analysis of eyes with DME treated with primary intravitreal pegaptanib sodium (Macugen) (intravitreal pegaptanib group). The results were compared with the ones of eyes treated with intravitreal pegaptanib sodium associated with macular laser photocoagulation (combined treatment group), and the ones of eyes treated with primary macular laser photocoagulation (macular laser photocoagulation group). Results. For the intravitreal pegaptanib group (13 eyes), we found significant changes in mean best-corrected visual acuity (BCVA) and reductions in mean central macular thickness (CMT) at the last follow-up visit (P = .0014 and P = .0001). For the macular laser photocoagulation group (15 eyes), we found no statistically significant changes in mean BCVA and CMT at the last follow-up visit (P > .05). For the combined treatment group (12 eyes), we found no significant changes in mean BCVA at the last follow-up visit (P > .05) despite significant reductions in mean CMT (P = .0188). Conclusion. Intravitreal pegaptanib treatment alone may be superior to macular laser photocoagulation alone and to combined intravitreal pegaptanib treatment associated with macular laser photocoagulation in patients with DME.

Intravitreal bevacizumab (avastin) injection alone or combined with triamcinolone versus macular photocoagulation as primary treatment of diabetic macular edema

PURPOSE

To report the efficacy of a single intravitreal bevacizumab injection alone or in combination with intravitreal triamcinolone acetonide versus macular laser photocoagulation (MPC) as primary treatment of diabetic macular edema (DME).

METHODS

In this randomized, three-arm clinical trial, 103 eyes of 97 patients with clinically significant DME and no previous treatment were enrolled. The eyes were randomly assigned to one of three study arms: the intravitreal bevacizumab (IVB) group, patients who received 1.25 mg of intravitreal bevacizumab (37 eyes); the IVB/IVT group, patients who received 1.25 mg of intravitreal bevacizumab and 2 mg of intravitreal triamcinolone (33 eyes); and the MPC group, patients who underwent focal or modified grid laser (33 eyes). Primary outcome measure was change in visual acuity.

RESULTS

Visual acuity changes +/- SD at 12 weeks were -0.22 +/- 0.23, -0.13 +/- 0.31, and + 0.08 +/- 0.31 logarithm of the minimal angle of resolution in the IVB, IVB/IVT, and MPC groups, respectively. The marginal regression model based on generalized estimating equation analysis demonstrated that the visual acuity changes in the groups were statistically significant at both 6 weeks (P < 0.0001) and 12 weeks (P = 0.024). The significant treatment effect was demonstrated at both 6 weeks and 12 weeks in the IVB group and only at 6 weeks in the IVB/IVT group. Significant central macular thickness (CMT) reduction was observed in eyes in the IVB and IVB/IVT groups only up to 6 weeks; however, CMT changes were not significant in the groups.

CONCLUSION

Up to 12 weeks, intravitreal bevacizumab treatment of patients with DME yielded better visual outcome than laser photocoagulation, although it was not associated with a significant decrease in CMT. No further beneficial effect of intravitreal triamcinolone could be demonstrated. Further clinical trials with longer follow-up are required to evaluate the long-term visual outcomes and complication profiles after primary treatment with such medications.

Association of manganese superoxide dismutase gene polymorphism (V16A) with diabetic macular edema in Korean type 2 diabetic patients

This study was designed to investigate whether V16A polymorphism of the manganese superoxide dismutase (Mn-SOD) gene is associated with the development of type 2 diabetes mellitus and with progression of diabetic retinopathy (DR) and diabetic macular edema (DME). We simultaneously analyzed insertion/deletion polymorphism of the angiotensin-converting enzyme (ACE) gene in the 16th intron to avoid its confounding effect. A total of 192 nondiabetic subjects and 304 type 2 diabetic patients were included in the study. Diabetic retinopathy was classified as nonretinopathy, nonproliferative retinopathy, and proliferative retinopathy. Diabetic macular edema was defined as thickening of the retina and/or hard exudates within a 1-disk diameter of the center of the macula. Diabetic macular edema was further classified into focal, diffuse, and ischemic types. The A allele frequency of the Mn-SOD gene was not different between nondiabetic and type 2 diabetic subjects, between the normotensive and hypertensive groups, between the DR (-) and DR (+) groups, and among the stages of DR. In the DR (+) group, the DME (+) group had a lower A allele frequency than that of the DME (-) group. In the DME (+) group, focal, diffuse, and ischemic types were found in 8, 23, and 6 patients, respectively. The A allele frequency of each type was 0.188, 0.109, and 0.0. The D allele frequency of the angiotensin-converting enzyme gene did not differ in any of the comparisons. Clinical and laboratory parameters of the A allele carriers were not different from those of the noncarriers except for the prevalence of hypertension and DME. Hypertension, diabetic duration, and insulin therapy were related to DR. The A allele, hypertension, and insulin therapy were associated with DME. In conclusion, our results suggest that V16A polymorphism of the Mn-SOD gene is not related to the development of diabetes and progression of DR, but is associated with DME in Korean type 2 diabetic patients.

A Pilot Study of Multiple Intravitreal Injections of Ranibizumab in Patients with Center-Involving Clinically Significant Diabetic Macular Edema

OBJECTIVE

To evaluate the biologic activity of multiple intravitreal injections of ranibizumab in patients with center-involving clinically significant diabetic macular edema (DME) and to report any associated adverse events.

DESIGN

Single-center, open-label, dose-escalating pilot study.

PARTICIPANTS

A total of 10 eyes of 10 patients (mean age, 69.3 years [range, 59-81]) with DME involving the center of the macula and best-corrected visual acuity (BCVA) in the study eye between 20/63 and 20/400.

INTERVENTION

Three intravitreal injections of ranibizumab (0.3 mg or 0.5 mg each injection) administered on day 0, month 1, and month 2, and observation until month 24.

MAIN OUTCOME MEASURES

Primary end points were the frequency and severity of ocular and systemic adverse events. Secondary end points were BCVA and measurement of retinal thickness by optical coherence tomography.

RESULTS

Of the 10 patients enrolled, 5 received 0.3-mg and 5 received 0.5-mg ranibizumab. Intravitreal injections of ranibizumab were well tolerated. No systemic adverse events were reported. Five occurrences of mild to moderate ocular inflammation were reported. At month 3, 4 of 10 patients gained > or =15 letters, 5 of 10 gained > or =10 letters, and 8 of 10 gained > or =1 letters. At month 3, the mean decrease in retinal thickness of the center point of the central subfield was 45.3+/-196.3 microm for the low-dose group and 197.8+/-85.9 microm for the high-dose group.

CONCLUSIONS

Ranibizumab appears to be a well-tolerated therapy for patients with DME. This pilot study demonstrates that ranibizumab therapy has the potential to maintain or improve BCVA and reduce retinal thickness in patients with center-involved clinically significant DME.

Diabetic vitrectomy: risks, prognosis, future trends

PURPOSE OF REVIEW

We review the current standards, risks, prognosis, and indications for diabetic pars plana vitrectomy and consider recent developments in surgical techniques. We also examine surgery's role as a treatment modality for diabetic eye disease among the other accepted and developing treatment options, such as systemic and intravitreal pharmacotherapy.

RECENT FINDINGS

Pars plana vitrectomy for diabetic macular edema and for traction retinal detachment is addressed. Techniques to decrease retinal swelling and ischemia are showing promising results. The use of the smaller 25-gauge and 23-gauge vitrectors is gaining acceptance and offers advantages such as less trauma, less postoperative discomfort, and quicker healing. Techniques are being developed and refined to help prevent postoperative vitreous hemorrhage using cryotherapy around sclerotomy sites and/or endolaser in a near-confluent pattern in an effort to quell fibrovascular ingrowth and subsequent hemorrhage. Finally, pharmacological advances include targeting three levels of intervention: achieving the best glycemic control, correcting altered retinal metabolism secondary to increased glucose availability, and employing neuroprotective and vasoprotective agents.

SUMMARY

The combination of therapies and interventions as they improve and evolve offers the potential to revolutionize the approach to the complications of diabetic eye disease and may soon render many current interventions obsolete. Diabetic pars plana vitrectomy continues to advance with better anatomic and visual success.