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.
Novolin is the brand name of three distinct insulin-containing products manufactured by Novo Nordisk:

Novolin 70/30, an insulin preparation containing mixed NPH and regular insulin, respectively
Novolin N, an insulin preparation containing NPH insulin
Novolin R, an insulin preparation containing regular insulin

See also
Insulin (medication)


== References ==