Practical Lessons from Protocol I for the Management of Diabetic Macular Edema

Protocol I, a multicenter randomized clinical trial, compared the visual outcomes of patients treated with 0.5 mg intravitreal ranibizumab with either prompt or deferred (by 24 weeks laser), 4 mg intravitreal triamcinolone with prompt laser, or sham injection with prompt laser for the treatment of center-involving diabetic macular edema (DME). A total of 854 adult patients with type I or II diabetes and any level of non-proliferative diabetic retinopathy or proliferative retinopathy with adequate panretinal photocoagulation, with best-corrected visual acuity (BCVA) of 78 to 24 ETDRS letters (Snellen equivalent of 20/32 to 20/320) and visual loss attributed to macular edema, or retinal thickening with central subfield thickness of at least 250 µm by OCT were enrolled. The main outcomes relevant for practicing clinicians are as follows. (1) Intravitreal ranibizumab treatment provides superior visual outcomes compared to conventional laser treatment. (2) Adjunctive laser treatment does not appear to provide substantial visual benefit compared to ranibizumab treatment alone, but may reduce the number of injections required to resolve DME. Deferral of laser is likely beneficial in patients with worse initial visual acuity. (3) Intravitreal triamcinolone provides similar visual outcomes compared to intravitreal ranibizumab in pseudophakic patients but is associated with a clinically important increased risk of increased intraocular pressure (IOP), need for glaucoma medications, and need for glaucoma surgery. (4) Delayed initiation of intravitreal ranibizumab therapy provides improved visual outcome among patients initially treated with conventional laser photocoagulation or triamcinolone, but the magnitude of the benefit is not as great as is observed when ranibizumab treatment is initiated promptly. (5) The number of ranibizumab injections required to achieve the desired visual outcome decreases substantially after the first year, with the majority of patients not requiring further treatment after 3 years. (6) Patients who do not have a rapid response to ranibizumab still display long-term benefit to continued therapy, although perhaps less than those with immediate improvement. (7) Intravitreal ranibizumab is not only effective in reducing retinal edema and improving BCVA among patients with DME, it is also a disease modifying therapy and induces improvement of the diabetic retinopathy severity score by 2 or more steps in approximately one third of patients. Triamcinolone injection also induces improvement in diabetic retinopathy severity in DME patients, but perhaps to a lesser degree. (8) No increased risk of systemic adverse events was observed among patients treated with intravitreal ranibizumab compared to sham-injected controls or triamcinolone-treated patients, but the low frequency of adverse events, restrictive enrollment criteria, and specific posology employed in this study limit the generalization of this conclusion to patients routinely encountered in clinical practice. (9) There was no clinically important increased risk of major ocular complications among patients treated with intravitreal ranibizumab (including the risk of glaucoma), although endophthalmitis is a potentially devastating outcome should it occur. In addition to the risk of endophthalmitis, intravitreal triamcinolone injection was associated with clinically important increased risk of cataract progression and increased IOP.