In the news: DHA Linked to Alzheimer’s Retinopathy; Vitamin D May Help Stabilize Keratoconus

DHA Linked to AD-Associated Retinopathy

In addition to the hallmarks of Alzheimer’s disease (AD), memory loss and cognitive impairment, changes in visual function have also been reported. AD may directly affect the retina in the form of Alzheimer’s disease associated retinopathy. This condition can include structural and functional alterations in the retina.

Studies suggest these retinal alterations may mirror changes that are happening in the brain. The retina and the brain both contain high amounts of docosahexaenoic acid (DHA). DHA is concentrated in the retina and is vital for photoreceptor cell health.

Deficiency of DHA, frequently seen in AD, is related to several ocular disorders, such as age-associated macular degeneration, diabetic retinopathy, and retinitis pigmentosa.

In the present study(1), researchers evaluated retinal DHA concentration and function in a mouse model of AD (5xFAD). The percentage of DHA in the retina were determined at 3, 6, 9 and 12 months and amyloid accumulation and retina thickness were measured. ERGs and OCT were performed at 3 months.

Results showed that the total retinal DHA content was 40-50% lower in the AD model mice compared to control littermates at all time points measured.

The controls had very low levels of amyloid beta vs. the AD model mice, who had significant reductions in ERG a- and b-wave amplitudes and marginally decreased retinal thickness at 3 mo. v controls.

The investigators concluded that targeting DHA may provide a novel approach for treating or preventing Alzheimer’s disease associated retinopathy.

Vitamin D & Progression of Keratoconus

Keratoconus is a progressive eye disease characterized by corneal thinning, bulging of the cornea and irregular astigmatism. The result can be blurred vision, greater sensitivity to light and glare, and impaired night vision.

Keratoconus is typically diagnosed in young people, often during adolescence or early adulthood, and can progress through the third and fourth decade of life.

Researchers from the departments of Neuroscience and Ophthalmology of San Raffaele Scientific Institute in Milan, conducted a prospective pilot intervention to assess whether vitamin D supplementation affects keratoconus progression(2).

Forty patients aged 12 to 20 years, with vitamin D insufficiency and diagnosed with keratoconus in at least one eye, were included in the study. Participants received vitamin D supplements for six months.

The main outcome measure was the percentage of patients with a kmax progression less than 1 diopter (i.e. stable patients). In keratoconus, kmax refers to the steepest curvature of the cornea, measured in diopters.

The investigators report that vitamin D stabilizes the cornea and reduces keratoconus progression. Kmax progressed less than one diopter in 75% of eyes after 12 months, with BCVA and corneal thickness rates remaining stable.

Patients who responded to treatment showed a downregulation of inflammatory and platelet activation pathways and upregulation of proteoglycan (extra-cellular matrix) biosynthesis. Collagen degradation decreased as inflammation was modulated in patients supplemented with vitamin D.

According to the authors, these findings support the hypothesis that vitamin D supplementation can affect keratoconus progression in adolescent patients with low levels of the vitamin. They state that the results “strongly suggest that keratoconus may be the ocular manifestation of a systemic disorder”.

References

1. Dhavamani S, et al. Docosahexaenoic acid deficiency is linked to Alzheimer’s disease associated retinopathy and affects retinal function. ARVO Ann Meeting Abstract, 66, 2328. June 2025.
2. Bartolomeo N, et al. The effects of vitamin D on Keratoconus progression. Am J Ophthalmol. 276: 235-251, 2025.