Ординатура / Офтальмология / Английские материалы / Diabetes and Ocular Disease Past, Present, and Future Therapies 2nd edition_Scott, Flynn, Smiddy_2009

Figure 8.14. A 47-year-old man with proliferative diabetic retinopathy presented with macular tractional retinal detachment in his left eye. Preoperative color appearance showing extensive tractional fibrotic membranes and macular TRD (top, left). Preoperative spectral domain OCT (SD-OCT) revealing extensive subretinal fluid and epiretinal membrane (top, right). The central subfield retinal thickness in the macula was 1003 microns. Postoperative appearance showing removal of tractional epiretinal membrane and retinal reattachment (bottom, left). Postoperative SD-OCT showing resolution of this fluid, absence of the membrane, and retinal reattachment (bottom, right). The central subfield retinal thickness in the macula was 338 microns postoperatively. (Source: Adapted from Kay et al., Ophthalmic Surg Lasers Imaging [61].)

[58]. Pathologic vitreous adherence to the macula and posterior pole is now a wellrecognized cause of vision loss in diabetics [57–60].

PROLIFERATIVE DIABETIC RETINOPATHY (PDR)

Proliferative diabetic retinopathy (PDR) is best evaluated with clinical examination, fluorescein angiography and, in cases with media opacity, B-scan ultrasonography. Extraretinal neovascularization and vitreous hemorrhage in PDR are traditionally evaluated and monitored with serial fundus photographs or echography before and after intervention (e.g., panretinal laser photocoagulation, pars plana vitrectomy). Left untreated, neovascular complexes often result in the development of complex tractional retinal detachment (Figs. 8.9–8.15). OCT can help determine macular involvement of the traction retinal detachment and further characterize the nature and extent of the traction [35–37]. In addition, vision loss

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Figure 8.15. These images are of a 53-year-old diabetic man who underwent pars plana vitrectomy, membrane peeling, and silicone oil injection for management of proliferative diabetic retinopathy with traction retinal detachment. The color fundus photograph (top, left) demonstrates peripheral laser ablation and an attached macular with typical silicone oil light reflex (normal artifact in eyes with silicone oil). The optical coherence tomography (OCT) radial line scan demonstrates the ability of OCT to visualize the macula through silicone oil, revealing a relatively normal appearing macular contour that is free of vitreoretinal traction, cystoid macular edema, or subretinal fluid. Visual acuity is 20/400. The yellow hyper-reflective line anterior to the fovea is characteristically seen on OCT Scans of eyes harboring silicone oil.

following panretinal laser photocoagulation can be evaluated with OCT to determine whether a serous retinal detachment, new or exacerbated cystoid macular edema, or new preretinal hemorrhage (Fig. 8.13A) may be present and accounting for the vision fluctuation.

If surgical repair of a complex traction retinal detachment requires silicone oil, OCT is useful to assess for post-silicone oil visual acuity fluctuations. This information is often helpful when determining the proper time for silicone oil removal, because a macular cause for visual loss can be ruled out in most cases. Physicians should know that a normal artifact of OCT scans from eyes with silicone oil consists of a characteristic linear or crescentic hyperreflective focus just above the fovea, representing the posterior silicone oil/retina junction (Fig. 8.15).

SUMMARY

In conclusion, OCT has become an essential tool in the evaluation of patients with diabetic retinopathy. Along the wide spectrum of the disease, OCT has clinical utility, but its greatest application is in the diagnosis and management of patients with DME. Quantifying macular thickness and monitoring response to treatment are two features of this technology that make it so popular amongst vitreoretinal specialists. Its ability to assess vitreoretinal tractional abnormalities is also quite valuable, especially when these are unsuspected. More severe diabetic retinopathy that is associated with traction retinal detachment can be better characterized with OCT, insofar as subtle and progressive involvement of the macula can be ascertained.

OCT is continually being validated and it has been shown to be a reproducible technology. Virtually all new clinical trial protocols have included OCT outcomes—in addition to visual acuity—as one of their main outcome measures. Clinical examination, fundus photography, fluorescein angiography, and ultrasonography all remain important tools in the management of diabetic retinopathy. OCT has not, and likely will not, replace any of these useful diagnostic modalties, but instead it serves to enhance our understanding of this difficult disease in new ways. Technological advancements in OCT have incorporated image registration with an accompanying fundus photograph (ability to superimpose the scan on the fundus image), ultra-high-resolution image quality, entire macular capture at one sitting (compared to the individual radial line scans captured now), and three-dimensional topographical image rendering. All of these improvements are anticipated to improve the reliability and reproducibility of the technology as well as the longitudinal comparison of the patient over time. Enhanced understanding of the dynamics of the vitreomacular relationship is also anticipated.

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PHOTOCOAGULATION

Blindness from PDR was recognized as a growing public health problem in the 1960s. Although a number of possible treatments were tried, there was general uncertainty as to the best approach for treating diabetic retinopathy [8]. Introduced by Meyer-Schwickerath, photocoagulation was initially used to coagulate patches of new vessels on the surface of the retina [9]. During the 1960s, it became apparent that extensive retinal photocoagulation seemed to have a beneficial, but unexplained, indirect effect on both neovascularization and macular edema [10]. By the early 1970s, a few small clinical trials had indicated that photocoagulation might be an effective treatment [11].

Diabetic Retinopathy Study, 1971–1978. Because of the public health importance of the disease and the collective doubt as to its treatment, the Diabetic Retinopathy Study (DRS) was organized in 1971 to test the effect of photocoagulation on diabetic retinopathy (Table 9.1). This was the first randomized, multicenter, collaborative clinical trial sponsored by the newly formed National Eye Institute of the National Institutes of Health. The DRS enrolled 1742 patients with PDR or severe nonproliferative diabetic retinopathy (SNPDR) and visual acuity of 20/100 or better in each eye [12]. The age distribution of the population was bimodal, with 23% in the 20 to 29 years age group and 27% in the 50 to 59 group. The majority of DRS patients were male (56%) and white (94%).

One eye of each patient was randomly assigned to receive photocoagulation, and the fellow eye was observed without treatment. One of two photocoagulation techniques, using either the xenon arc or the newly developed argon laser, was randomly selected. All treated eyes received both direct and scatter (panretinal) photocoagulation and the treatment techniques, using either photocoagulation modality, were similar.

Table 9.1. Diabetic Retinopathy Study

Study Question

Is photocoagulation (argon or xenon) effective for treating diabetic retinopathy?

Eligibility

Proliferative diabetic retinopathy or bilateral severe nonproliferative diabetic retinopathy, with visual acuity 20/100 or better in each eye

Randomization

1742 participants, one eye randomly assigned to photocoagulation (argon or xenon), and one eye assigned to no photocoagulation

Outcome Variable

Visual acuity less than 5/200 for at least 4 months

Result

Photocoagulation (argon or xenon) reduces risk of severe visual loss compared with no treatment

Direct treatment involved the placement of photocoagulation burns over abnormal new vessels. All neovascularization elsewhere (NVE) was treated directly with either modality, but neovascularization of the disc (NVD) was treated directly only with the argon laser. Direct treatment was also applied to microaneurysms or other lesions thought to be causing macular edema. Scatter photocoagulation consisted of photocoagulation burns that avoided the macula and optic nerve, with each burn separated from its neighbors by one-half burn width. This resulted in a polka-dot pattern of burns in the retina that extended from the temporal vascular arcades to beyond the equator. In general, the argon laser burns were smaller and less intense than the xenon arc burns.

Analysis of follow-up data from that study demonstrated a 50% reduction in severe visual loss in eyes that had received photocoagulation (Fig. 9.1) [13]. Severe visual loss was defined as visual acuity <5/200 at two or more consecutively completed follow-up visits, which were scheduled at 4-month intervals. In addition to demonstrating that photocoagulation was effective, the DRS identified retinopathy features associated with a particularly high risk of severe visual loss [14–17]. Treatment was recommended for eyes with these high-risk characteristics, which can be summarized as either neovascularization accompanied by vitreous hemorrhage or obvious neovascularization on or near the optic disc (Fig. 9.2), even in the absence of vitreous hemorrhage.

After 24 months of follow-up in the DRS, the rates of severe visual loss for eyes with high-risk characteristics in the control group and treated groups were 26% and 11%, respectively. Eyes with PDR but without high-risk characteristics had a much lower risk of developing severe visual loss by 2 years in both the control group and the treated group (7% and 3%, respectively); these rates were even lower for the eyes with nonproliferative diabetic retinopathy (NDPR).

Harmful effects of treatment were greater in the xenon group, as shown in Table 9.2. Of the xenon-treated eyes, 25% suffered a modest loss of visual field, and an additional 25% suffered a more severe loss. Loss of visual field was much less in the argon-treated group, with only 5% of eyes suffering a modest or severe loss as measured using the largest test object (Goldmann IVe4). About 19% of

Figure 9.1. Diabetic Retinopathy Study results: Cumulative incidence of severe visual loss (visual acuity worse than 5/200 at two consecutive 4-month follow-up visits) for untreated eyes (N = 1681), argon-treated eyes (N = 835), and xenon-treated eyes (N = 847); P < 0.001 for both treated groups versus control group.