Inherited retinal dystrophies (IRD)

What is it?

This is a heterogeneous group of ocular pathologies, genetically determined, in which, due to the participation of various genes and etiopathogenetic mechanisms, there is a progressive degeneration of retinal photoreceptors (rods and cones). They fall into two broad categories depending on whether rods (rod-cone dystrophies, incorrectly called peripheral forms) or cones (cone-rod dystrophies, incorrectly called macular dystrophies) are initially involved.

The initial symptoms are different: rod-cone forms are characterized by night blindness and a decrease in the visual field, while cone-rod forms have an earlier loss of central vision, acquired color vision deficiency, glare. In the terminal stages, if the damage has spread to all photoreceptors, the forms can overlap and are difficult to distinguish even with instrumental studies. In some cases, changes in the retina are a sign of syndromic diseases (that is, they affect several parts of the body), and in these cases, a polyspecific classification of the patient is necessary (in particular, an otolaryngologist, neurologist, clinical geneticist).

Inherited retinal dystrophies can be transmitted by any mode of inheritance (autosomal recessive, autosomal dominant, X-linked, mitochondrial). Among the main pathologies, we distinguish peripheral forms: retinitis pigmentosa (typical and atypical forms) and central forms: Stargardt's macular dystrophy, Best's macular dystrophy, X-linked retinoschisis, progressive cone dystrophy.

How is it diagnosed?

Diagnostics is clinical and instrumental (in particular, OCT, autofluorescence and electroretinography) and in some cases can be supplemented with biomolecular diagnostics (for example, RHO, ABCA4). For syndromic forms, a multidisciplinary examination is required.

How is it treated?

Basically, no effective treatment has been found. In some cases of syndromic forms (for example, Refsum disease), treatment of the underlying disease is necessary (for example, a targeted diet). Numerous studies and experimental therapeutic protocols have been conducted or are ongoing (vitamin A supplementation is the main one), which, however, must always be carefully evaluated on a case-by-case basis for potential side effects. Finally, there are also numerous studies (with preliminary results, albeit "encouraging") on gene therapy. However, patients can be helped by prescribing filter lenses and optical aids (at centers for the visually impaired) to optimize residual vision and relieve symptoms in certain aspects. Patients should then undergo periodic full specialist examinations to diagnose and treat any complications (such as macular edema, retinal neovascularization, cataracts).

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