Defective ABCA4 leads to improper shuttling of vitamin A throughout the retina, and accelerated formation of toxic vitamin A dimers (also known as bisretinoids), and associated degradation byproducts. Vitamin A dimers and other byproducts are widely accepted as the cause of STGD1. As such, slowing the formation of vitamin A dimers might lead to a treatment for Stargardt. When vitamin A dimers and byproducts damage the retinal cells, fluorescent granules called lipofuscin in the retinal pigmented epithelium of the retina appear, as a reflecting such damage. In STGD4, a butterfly pattern of dystrophy is caused by mutations in a gene that encodes a membrane bound protein that is involved in the elongation of very long chain fatty acids (ELOVL4)

Diagnosis
Diagnosis is firstly clinical through history and examination usually with a Slit-lamp. If characteristic features are found the investigations undertaken will depend on locally available equipment and may include Scanning laser ophthalmoscopy which highlights areas of autofluorescence which are associated with retinal pathology. Spectral-domain optical coherence tomography, electroretinography and microperimetry are also useful for diagnostic and prognostic purposes. Fluorescein angiography is used less often than in the past. These investigations may be followed by genetic testing in order to avoid misdiagnosis. Other diseases may have overlapping phenotypic features with Stargardt Disease and the disease itself has multiple variants. In one study, 35% of patients diagnosed with Stargardt Disease through physical ophthalmic examination were found to be misdiagnosed when subsequent genetic testing was done.
Kubota Vision published the results of a dose range study of a drug known as Emixustat, with findings that will effect dose selection for their phase III trial set to complete in June 2022.Stem-cell therapy involves injecting cells with the potential to mature into differentiated and functioning retinal cells. This therapy has the potential stop disease progression and in the long term improve vision. To improve vision this technique will need to replicate the complex multi-layered and neurally  anatomy of the retina. There are a number of research groups working with stem cells one of which is Ocata Therapeutics.Alkeus Pharma is evaluating the potential of deuterated vitamin A as the drug ALK-001. The hope is that the deuterated vitamin A will reduce the build-up of toxic vitamin A metabolites in the retina and therefore slow rate of visual deterioration. To create deuterated vitamin A some of the hydrogen atoms are replaced with the isotope  deuterium  which has an extra neutron and is therefore twice the standard atomic weight of hydrogen. A Phase II clinical trial is taking place using ALK-001 with an estimated completion date of December 2024.MD Stem Cells, a research-physician clinical development company using autologous bone marrow derived stem cells (BMSC), has released results of the Stargardt Disease cohort within their ongoing Stem Cell Ophthalmology Study II (SCOTS2) clinical trial (NCT 03011541).