Diabetic Retinopathy: the role of inflammation

Visual and functional outcomes

Pubblicato il

Thursday, 4 February 2021

Argomento

Retina

Role of inflammation in the pathogenesis of diabetic retinopathy (DR)

Over the past ten years, several studies have shown molecular changes within the retinal structure, consistent with the role crucial of inflammation in the onset of this disease. Many inflammatory cytokines and chemokines have been detected in samples - both ocular (vitreous and aqueous humour) and serum - in diabetic patients with DR. Furthermore, several studies have shown that activation of Müller glial cells (a type of retinal cells) could contribute to the early onset of inflammation in the eye, the latter process being responsible for retinal damage in the later stages of the disease.

Incidence and classification of diabetic retinopathy

Diabetic retinopathy (DR) is the main cause of visual impairment in the population of diabetic patients of working age in the western world. It constitutes one of the three most serious and frequent microvascular complications of the eye related to diabetes mellitus, along with nephropathy and neuropathy. The prevalence rate for DR for all adults with diabetes aged 40 years and above is 34.6% worldwide (93 million people), with the prevalence set to increase.

Diabetic retinopathy is classified according to the presence of ophthalmoscopically visible vascular lesions. DR can be classified into non-proliferative phase (NPDR - non-proliferative diabetic retinophaty) characterised by retinal vascular tortuosity, retinal haemorrhages, microaneurysms and lipid exudates; and a proliferative phase (PDR - proliferative diabetic retinophaty), characterised instead by the formation of new, fragile and aberrant blood vessels. (https://www.oculistaitaliano.it/articoli/retinopatia-diabetica-e-edema-maculare-diabetico/). DR, at an advanced stage, can progress to diabetic macular oedema (EMD), which leads to abnormal retinal thickening and, often, cystoid oedema of the macula. EMD may occur in all levels of severity of DR, both NPDR and PDR, and is the most common cause of loss of sight in diabetic patients.

With advances in diagnostic tools, it has been shown that patients with diabetes present the first signs of altered neuroretinal function even before the appearance of microvascular lesions in the eye. Currently, however, there are no therapies that can be used in the early stages of the disease to prevent neuroretinal alterations and thus preserve visual function.

Role of inflammation in retinal neurodegeneration

In addition to vascular changes, the neurosensory retina is deeply affected by the effects of diabetes. An emerging issue and focus of attention in DR research is, in fact, the precise relationship between inflammatory conditions and loss of neuronal function. The mechanisms underlying retinal degeneration are multiple and range from hyperglycaemia to oxidative stress (accumulation of chemical species that are toxic to the body).

RD and EMD: outcomes on visual and functional abilities

Diabetic eye diseases are associated with a deterioration of the quality of life of the affected person, as they limit activities considered 'normal' including work, driving, walking and reading. Moreover, vision loss has a considerable psychological impact. Recent studies have shown, in fact, that people with diabetic retinopathy are at greater risk of experiencing symptoms of anxiety e depression and are unable to live with their pathological condition. Surveys of patients with DR have reported discomfort at work due to reduced vision, resulting in a 'loss' of 20%-23% of time compared to the normal condition. Another study showed that people with severe DR have greater difficulties in several activities, such as reading, finding objects on a crowded shelf, walking down steps, stairs or pavements and driving.

Bibliography:

Dr. Carmelo Chines
Direttore responsabile