Photopic ERG
Scotopic ERG
Multifocal ERG
Stargardt
N/↓
N/↓
↓
Cone dystrophies
↓↓
N
↓↓
Cone-rod dystrophies
↓↓
↓
↓↓
Late-onset Stargardt
The misunderstanding is that patients with an age at onset 50 years or above cannot have a retinal dystrophy and are thus most likely diagnosed with AMD.
Moreover, the clinical phenotype of foveal sparing is not exclusively found in late-onset Stargardt. Geographic atrophy in AMD, mitochondrial retinal dystrophy (MIDD) associated with the m.3243A>G mutation, central areolar choroidal dystrophy (CACD), and pseudo-Stargardt should also be considered and differentiated by genetic testing.
In addition, two autosomal dominant types of macular dystrophy exist that resemble STGD1:
3.7 Treatment
There is currently no treatment available for Stargardt disease. Gene replacement and stem cell therapy is under development.
Because of the pathogenesis of Stargardt disease (mutations in the ABCA4 gene), sunlight protection by wearing sunglasses should be advised, as well as having a normal diet without inappropriate prescription of vitamin A supplements. These are the only preventive measures for slowing down the progression of disease. Regular ophthalmologic evaluations are recommended.
3.8 Remark
Due to the high clinical variability, prognosis depends on different parameters (in particular age at onset, severity of ABCA4 mutations, and electroretinographic findings) (Table 3.2) that may help the clinician provide the patient with an indication of the course of disease. Stargardt disease may progress rapidly over a few months rather than several years, leading to a severe decrease in visual acuity (Fig. 3.1). Peripheral vision is not affected, even though some patients progress to a cone-rod phenotype that does affect the peripheral retinal function.
Table 3.2
Overview of types of Stargardt disease
Age at onset | Typical abnormalities at fundoscopy | Visual acuity decline | End-stage visual acuity (Snellen) | ERG abnormalities | ABCA4 mutations |
|---|---|---|---|---|---|
Early (mean, 7 years) | None/bull’s-eye/central atrophy | Fast | Hand movement | Cone-rod | Severe–severe |
Intermediate (mean, 23 years) | Yellowish flecks/fundus flavimaculatus | Moderate | 20/1200–20/200 | Cone | Severe–mild |
Late (mean, 55 years) | Foveal sparing | Slow | 20/100–20/40 | None | Mild–mild |
Fig. 3.1
Overview of disease progression in subtypes of Stargardt disease. Subtypes have distinctive disease onsets, indicating the severity of disease. The visual acuity decline is fast in early-onset Stargardt, whereas in late-onset Stargardt, visual acuity is affected only several years after disease onset
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