Retinal structural changes more prominent in pediatric subjects with vitamin D deficiency: AJO

Vitamin D receptors and some enzymes related with vitamin D metabolism and pathways have been found in the retina and choroid. Some studies have suggested the potential role of vitamin D in the functional and anatomical properties in the retina, and its pathological mechanisms in some retinal diseases

Pediatric vitamin D deficiency is relatively common in developing countries and is associated with multifactorial properties including genetic, geographic, and dietary properties.

The aim of this study carried by Emre Aydemir and team was to quantitatively evaluate the retinal structural parameters, including the peripapillary retinal nerve fiber layer (RNFL), central macula, retinal layer, and choroidal thicknesses, central retinal artery equivalent (CRAE), and central retinal vein equivalent (CRVE), in pediatric patients who were determined to have a deficiency of vitamin D.

It was a Prospective, cross-sectional study. Retinal structural parameters, including the peripapillary retinal nerve fiber layer (RNFL), central macula, retinal layer, and choroidal thicknesses, central retinal artery equivalent (CRAE), and central retinal vein equivalent (CRVE), in pediatric subjects with vitamin D deficiency (Group 1) and those without (Group 2) were compared.

• Group 1 comprised 70 individuals, while Group 2 comprised 80 individuals.

• The mean peripapillary RNFL [except for the nasal superior sector (p =0.037)], central macula, and retinal layer thicknesses were also determined to be similar in both of the groups (p >0.05 for both groups).

• The mean choroidal thickness was lower in the subfoveal (p =0.006) and nasal 3000-µm-diameter areas (p =0.004) in Group 1.

• The mean CRAE was determined to be lower (p =0.031) and the CRVE was higher in Group 1 (p =0.005); it was determined that there was a significant correlation between the vitamin D level and both the CRAE (r = 0.447, p<0.001) and CRVE (r = –0.320, p =0.013).

There has been some evidence of the neuroprotective role that vitamin D plays in the central nervous system. Vitamin D restricts damage in cellular and mitochondrial membranes by decreasing of nitric oxide synthase activation and reactive oxygen species production. A breakdown in neuroprotective and immunoregulatory mechanisms may contribute to neurodegenerative damage in the optic nerve axons and ganglion cell bodies.

According to the results of this study, the peripapillary RNFL (except in the nasal superior sector) was not altered by vitamin D deficiency.

Because they have higher metabolic activity, the photoreceptor cells in the retina are the most vulnerable to oxidative stress. Photoreceptor degeneration can develop due to a lack of protection from reactive oxygen species. The antioxidant function of vitamin D has been a relatively well-illuminated issue; however, when considering the results of this study, vitamin D deficiency did not seem to be a particular reason for the decrease in the central macula and retinal layer thicknesses in the pediatric population.

Studies have demonstrated that vitamin D deficiency or single nucleotide polymorphisms in enzymes related with the metabolism of vitamin D cause some changes in the retina, which can be considered as preceding findings for age-related macular degeneration. Vitamin D deficiency that exists in the pediatric age for a long time is probably an independent risk factor for some retinal structural degenerations in the elderly.

The one of the most important results of this study was the finding of thinner choroidal parameters in pediatric subjects with vitamin D deficiency. These parameters were statistically significant in the subfoveal and nasal 3000-µm-diameter areas. Additionally, in the subfoveal, temporal 1500-µm-, and temporal 3000µm-diameter areas, the choroidal thickness parameters were significantly correlated with the vitamin D level, and thinner results were obtained in the subjects who had lower vitamin D levels.

Vitamin D is a potent inhibitor of endothelial cell sprouting, elongation, and proliferation, which is induced by vascular endothelial growth factor. It also inhibits the replication of vascular smooth muscle cells and reduces vascular mitogenic response to stimulatory factors. Vitamin D has an effect on the renin-angiotensin system and improves endothelial cell-dependent vasodilation. Vascular dysregulation caused by vitamin D deficiency may alter vascular structure and function, and micro-vessel circulation and ocular blood flow may decrease. In a situation where vitamin D deficiency exists for a long time, choroidal thinning may occur. The clinical or functional importance of these statistically significant results in the structural parameters presently unknown. This finding is likely associated with future ischemic/vascular or degenerative diseases of the retina. Diabetic retinopathy, as well as age-related macular degeneration, are two important diseases that are known to have a relationship with vitamin D deficiencyChoroidal thinning should be considered as a potential mechanism in vitamin D-associated pathogenesis for these diseases.

"Choroidal thinning, a decrease in the CRAE, and increase in the CRVE were some structural changes that occurred in the pediatric subjects who had vitamin D deficiency. The alterations in these parameters became more prominent in pediatric subjects who were determined to have lower vitamin D levels."

Source: Emre Aydemir , Cagri Ilhan , Gozde Aksoy Aydemir et al Evaluation of Retinal Structure in Pediatric Subjects with Vitamin D Deficiency, American Journal of Ophthalmology (2021),

doi: https://doi.org/10.1016/j.ajo.2021.06.031