Fig. 10.1
Position of macula 512 × 128 B scans for multi-view technique
Because this protocol relies upon the advanced image tracking capabilities of modern OCT scanners, a slight difference in position from visit to visit is acceptable when the software can match the images based on vessel topography and branching. If automatic registration fails, manual registration can also be used. The technique is currently restricted to the posterior pole due to the ability of a factory specification OCT scanner to image these areas most accurately. Imaging locations outside the arcades may require further adaptation of the OCT scanner, something not available to every ophthalmologist.
Figure 10.2 demonstrates the ability of the multi-view imaging technique to show uveitis recrudescence with steroid tapering, through the detection of angiographically proven paravascular leakage. In this example there is minimal macula oedema, and therefore the macula B-scan (not shown) does not appear to change between visits, demonstrating how macular oedema is a poor surrogate for disease activity in some uveitis patients.
Fig. 10.2 Disease recrudescence in a 59 year old BCR patient during a systemic corticosteroid tapering regimen. (a) Fundus photograph—characteristic deep lesions and vascular sheathing. (b) Late FA (10 min) at visit 1—asymptomatic patient using 20 mg oral prednisolone. (c) Late FA (10 min) at visit 2—2 months later following taper of oral prednisolone to 7.5 mg and return of symptomatic floaters. Increased leakage from posterior pole vessels is seen (white arrow). (d) Multi-view OCT thickness map at visit 1. (e) Multi-view OCT thickness map at visit 2. (f) Thickness comparison OCT map between visit 1 and 2 demonstrating perivascular retinal thickening
In the examples used, the four multi-view images taken as described have been manually composited for presentation, but their visual impact is just as powerful when viewed individually on the standard OCT imaging software. The further ability of OCT software to display a retinal thickness comparison map, when analysing the difference between scans from two patient visits, allows quick visual identification of perivascular thickening or thinning (Figs. 10.2f and Fig. 10.3e). Figure 10.3 illustrates a patient with posterior uveitis and retinal vasculitis who improves markedly on initiation of steroid therapy. There is no need to repeat the angiogram at the second visit as the change on multi-view OCT, and other clinical signs, is dramatic enough to confirm treatment success. It is important to remember that this technique is not yet fully validated, and it should be noted that this could miss peripheral leakage for which a true ultrawide-field angiogram may be the most appropriate investigation (see Chap. 3).
Fig. 10.3 Treatment effect in a newly diagnosed patient with BCR and retinal leakage. (a) Fundus photograph at initial presentation (treatment naïve) demonstrating haze due to vitritis, vascular sheathing and a hyperemic optic disc. (b) Late FA (7min) showing extensive vascular leakage from the posterior pole vessels, relatively mild macula edema and optic disc leakage. (c) Multi-view OCT thickness map at visit 1 showing severe perivascular thickening. (d) Multi-view OCT thickness map at visit 2 after 1 month treatment with oral corticosteroid. (e) Thickness comparison OCT map shows dramatic reductions in perivascular thickening & generalised retinal thinning
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