16.11Case 11: Diabetic Macular Edema with a Subfoveal Scar

A 65-year-old woman with type 2 diabetes and hypertension for 15 years sees you with a complaint of bilateral blurred vision for 2 years. Her best corrected visual acuitybilaterallyis20/200.Sheisbilaterallyphakicwith 2+ nuclear sclerotic cataracts. She is an immigrant to the United States and has had no previous ophthalmic care. The left eye is shown (Figs. 16.42 and 16.43); the right eye is similar. How would you manage the paracentral DME in the presence of the subfoveal scar?

Fig. 16.42 The left eye has a subfoveal scar with surrounding macular edema

16.11.1 Discussion

The patient described has had a devastating consequence of neglected DME with dense central

Fig. 16.43 An OCT radial line scan shows the nodular subfoveal scar with surrounding macular edema

macular exudates evolving into subfoveal fibrosis. There is no proven treatment to prevent this complication after exudates have collected in the subfoveal space. In fact, some have proposed surgical removal of these exudates to prevent this type of scarring.84 The patient should be educated regarding her guarded prognosis and referred for low vision counseling and services.

The goal of treatment at this point is to limit the extent of perifoveal DME and attempt to reduce the size of her central scotoma. The Early Treatment Diabetic Retinopathy Study showed that treatment of DME by focal/grid laser decreased the risk of moderate vision loss, but cases such as this were not addressed in that study. Additional macular laser may further degrade this patient’s macular visual field. Recent reports from the Diabetic Retinopathy Clinical Research Network revealed that focal laser was more effective in preventing vision loss than serial injections of intravitreal triamcinolone for clinically significant macular edema, but patients such

as this with subfoveal scarring were not included in the study.47,85 This patient is phakic, making

the use of intravitreal triamcinolone with its cataractogenic side effect less attractive. Anti-vascu- lar endothelial growth factor (VEGF) therapy has demonstrated efficacy in patients with diabetic

macular edema and lacks the side effect of cataract progression.86–90 Therefore, in this case intra-

vitreal anti-VEGF (e.g., bevacizumab) therapy may be the first step and if the edema proved to be recurrent, then combination therapy with bevacizumab plus focal/grid laser could be recommended.k

As a wide variety of treatment options exist for the treatment of diabetic macular edema (DME), consideration may be given to altering the therapeutic approach based on the severity of the edema. Although macular photocoagulation has withstood the test of time in the form of focal/grid laser treatment, intravitreal injection of triamcinolone aceto-

nide (IVT) and bevacizumab (IVB) has gained popularity.29,48,91 In the following cases (Figs.

16.44, 16.45, 16.46, 16.47, 16.48, and 16.49), a range of DME severity is presented. All examples are from patients with type 2 diabetes with ages ranging from 45 to 60 years. None have been treated previously. How should each case be managed?

Fig. 16.44 Red-free fundus photograph of the left eye of case 1. A circinate lipid ring surrounding a few microaneurysms is present temporal to the center of the macula

16.12.2 Discussion

The clinical management of diabetic macular edema requires the application of an extensive body of knowledge with the understanding that this information is incomplete. Therefore, it is not surprising

that there are differences of opinion in treatment recommendations. Table 16.2 summarizes the opinions of four authors of this book. No additional clinical information was provided, which may have altered the responses. For example, several doctors indicated they obtain fluorescein angiograms to

detect capillary nonperfusion and to guide laser treatment. As the individual responses were elicited in a masked fashion, there was no discussion among the participants. Such discussion frequently results in less divergence of opinion, especially as assumptions regarding the clinical presentation are revealed.

CASE 1: In the case of limited macular edema and exudates within 500 mm from the foveal center with fairly good visual acuity, there was general agreement to employ macular photocoagulation. Given the lack of stereoscopic fundus photographic demonstration of retinal thickening, the doctors made the assumption that clinically significant macular edema was present in this case. However, macular edema detected by optical coherence tomography does not equate with clinically significant macular edema.92 The central subfield macular thickness in this case was greater than 250 mm and, therefore, would have qualified for treatment in the Diabetic Retinopathy Clinical Research Network study.48 Doctor C offered the option of initial observation with a review of the general medical status of the patient. It may have been assumed by the others that the issue of managing the metabolic syndrome had already been undertaken. Doctor C was also reluctant to risk the creation of paracentral scotomata with laser in an eye with 20/25 vision. If the patient was symptomatic from macular edema, Doctor C recommended very light treatment sparing the FAZ in an effort to avoid adverse effects. Doctor B anticipated the need for treatment close to the fovea and, therefore, recommended warning the patient of post-laser blind spots. None of the respondents recommended IVT or IVB for this case. In the litera-

ture there appears to be a similar impression that focal DME may not require adjunctive therapy.93–95

CASE 2: In the case of extensive macular edema with profound central macular thickening (OCT central subfield macular thickness = 641 mm) and

visual acuity of 20/125, there was unanimous agreement to apply focal or grid macular photocoagulation. This agreement is consistent with the findings of the Early Treatment Diabetic Retinopathy Study (ETDRS) and the Diabetic Retinopathy Clinical Research Network (DRCR.net) reports.29,48 The recommendations regarding the adjunctive use of intravitreal injections covered the spectrum of options. Doctor A did not recommend the use of IVB or IVT. Doctor C considered the adjunctive use of IVT/IVB at the initial treatment session in order to speed the recovery of vision, depending on patient preference and need. There is support for this approach in the literature; however, the advantages of speeding the recovery of vision need to be

balanced by the well-known adverse effects of therapeutic intravitreal injection.91,96,48 Doctor B

recommended the use of IVB/IVT along with additional laser if persistent macular thickening remained four months following initial meticulous focal laser guided by fluorescein angiography. This approach suggests a step-up in therapy based on an unsatisfactory response to initial laser treatment. The results of the DRCR.net suggest that this patient likely would require more than one laser treatment in order to resolve the edema.48 Doctor D routinely performs IVT 1–2 weeks prior to modified grid laser. Prelaser IVT may decrease shortterm inflammation/edema from laser and may be of value in reducing the amount of laser energy required for macular photocoagulation via IVTinduced thinning of the macula.97,98 Doctor C expressed concern about the possibility of permanent central visual loss from inspissation of exudates into the fovea following resolution of the macular edema. Therapy of existing foveal plaques and exudates appears to be of limited benefit.99,100 Therefore, the possibility of prevention is appealing. Rapid resolution of exudates has been reported following IVT.101 In addition, the anti-fibrotic