There are several classic fundus findings (Table). In the early stages, these findings are subtle or entirely absent funduscopically.1,2,4-10 In intermediate stages, fundus findings become apparent and include a loss of retinal clarity (grayish perifoveal sheen), telangiectatic macular vessels, retinal pigment epithelium hypertrophy, blunted right-angled vessels, and superficial retinal crystalline deposits.2,4-11 Right-angled vessels may have a greater association with choroidal neovascularization, with growth into the outer retina in particular being a marker of disease progression.9 The crystalline deposits have been hypothesized to be the footplates of degenerated Müller cells.6
An important vision-threatening complication of MacTel2 is progression to proliferative disease.1,2,5-10 Choroidal neovascularization is present in a minority of cases and is associated with rapid vision loss.2,6 It is often accompanied by subretinal hemorrhage and lipid exudation.6,7,9 If untreated, the result can be disciform scarring and fibrosis.2,5,6 Additional complications of MacTel2 are foveal atrophy and full thickness macular holes.1,2,4-8, Macular holes secondary to MacTel2 respond poorly to pars plana vitrectomy with inner limiting membrane (ILM) peel.2,6
Diagnostic Testing
Diagnostic retinal imaging is invaluable in the diagnosis of MacTel2. The OCT can detect hyporeflectivity within the ellipsoid zone in early disease corresponding to ellipsoid zone loss, which increases as the disease progresses.1-8,10 This loss most often begins in the temporal parafoveal region and correlates with the progression of both relative and absolute scotomas perceived by affected individuals.2,3,5,8
Intraretinal foveal hyporeflective spaces on the OCT represent cavity formation after Müller cell and photoreceptor loss and do not correlate with increased thickness.1,2,4,6,7 This is important in differentiating from diabetic macular edema, which will often show thickening.6 In most cases of MacTel2, foveal thickness is decreased.4-6 The ILM remains intact overlying this space and is referred to as ILM drape.6,7 This can cause blunting or absence of the foveal light reflex and mimic the appearance of a macular pseudohole.4
The OCT-A allows visualization of capillary changes through every layer of the retina, which could not otherwise be appreciated, allowing early detection as well as precise staging of the disease.2,6-10 Anastomoses present in late-stage disease also can be imaged using OCT-A.7,9 These anastomoses can be seen as hyperreflective vasculature present between the retinal layers where there is little to no vasculature visible in normal eyes.7
A lesser-known occurrence in MacTel2 is the depletion of macular luteal pigment, with many eyes possessing an abnormal distribution.2,4,6-8,10 This depletion and abnormal distribution can be visualized with FAF. In particular, short wavelength fundus autofluorescence (SW-FAF) is the most effective at highlighting these changes.10 The characteristic finding is a hyperreflective halo surrounding the fovea.2,6 Fluorescence life imaging ophthalmoscopy (FLIO) is a recent development in FAF that measures FAF lifetime, which is the duration of time a structure autofluoresces.8 A cross-sectional study published in 2018 showed prolonged FAF lifetime in the temporal fovea of patients with early and moderate stage MacTel2 when compared with normal patients.8 More advanced stages showed a ring encircling the entire fovea.8
Classic FA findings in MacTel2 include early hyperfluorescence of temporal foveal telangiectatic capillaries and late-stage leakage with sparing of the central fovea.1,2,4,6,7,11
Management and Prognosis
Management of MacTel2 depends on the stage of the disease. In the absence of proven treatment, management in nonproliferative stages is conservative.2,6 Intravitreal anti-VEGF does not offer any benefit in nonproliferative disease.2,5,6 Indeed, as VEGF may have a neuroprotective effect on the retina, anti-VEGF may result in more harm than benefit in earlier disease stages.5 In proliferative stages, intravitreal anti-VEGF can help limit scarring and prevent vision loss.2,5
Long-term prognosis of MacTel2 is variable with VA typically better than 20/100.2 Vision loss in MacTel2 most often begins paracentrally; it can then progress centrally, leading to significant reduction in VA.12 The progression of this functional vision loss and corresponding structural damage is typically slow.3 VA worse than 20/100 is usually a result of proliferative disease; in such cases, there is potential for severe central vision loss and legal blindness.1
Conclusions
This case of MacTel2 underscores the subtle retinal findings in the earliest stages of the disease and the importance of a complete retinal examination and diagnostic imaging with macula OCT, OCT-A, and FAF to establish the correct diagnosis.
