Retinitis pigmentosa and ocular blood flow

Retinitis pigmentosa (RP) encompasses a large group of hereditary diseases of the posterior segment of the eye characterised by degeneration, atrophy and finally loss of photoreceptors and retinal pigment epithelium (RPE), leading to progressive visual loss. The term ‘retinitis’ refers to an inflammatory component. Indeed, most dystrophic and degenerative diseases are accompanied by low-grade inflammation. The term ‘pigmentosa’ refers to the pigmentary changes with a perivascular ‘bone-spicule’ configuration in the fundus of the eye (Figure 1).The fact that a number of different mutations affecting different genes [1] lead to the clinical picture described phenomenologically as RP explains the heterogeneity of the phenotypes, including age of onset, rate of progression and severity of the disease. Even though the disease has a genetic background, we assume that additional factors influence the manifestation of the disease. One potential modifying factor is disturbed ocular blood flow (OBF). Indeed, reduced OBF in RP patients has been described [2-4]. Blood flow is more or less always reduced in atrophic tissue, secondary to a decreased demand for supply. However, in this review, we summarise and focus on findings indicating an additional primary component of OBF reduction and explore the potential causes of such a primary component. Finally, we discuss the potential benefit of a vascular evaluation of RP patients with regard to prophylactic and supportive treatment in selected patients.As mentioned above, RP refers to a group of diseases of progressive retinal degenerations characterised by loss of photoreceptors and RPE with corresponding loss of function. The disease has a hereditary basis. The prevalence of RP is estimated to be one case among 3,000–5,000 individuals, with a total of about two million affected persons worldwide [5]. The disease starts typically (but not always) with night blindness followed by bilateral, symmetric, progressive concentric constric