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Despite the Health Organization's successful efforts to combat hunger in recent years, undernutrition remains a significant global public health concern. Globally, it was estimated that 9.8% of the population was undernourished in 20221. The incidence of undernutrition varies across regions, with higher prevalence among individuals with lower socioeconomic status2,3,4. Additionally, some individuals, especially young people, lose weight excessively in pursuit of a perfect body shape. Malnutrition, in all its various forms, affects every country in the world5.
Being underweight is associated with negative clinical outcomes, including infections, immune dysfunction, delayed wound healing, and growth and developmental retardation6,7,8,9. A malnourished state is one of the leading risk factors for premature death and the loss of disability-adjusted life years10,11,12. Studies have shown that the lowest body mass index (BMI) is associated with the poorest binocular ability13. Furthermore, research has demonstrated that undernutrition is linked to various ocular issues, such as macular degeneration, decreased dark adaptation, optic atrophy, keratitis, dry eye, and retinoblastoma14,15,16,17,18.
The retina, with its multiple layers and cell types, is a complex tissue, while the choroid is a highly vascularized structure that provides nutrients to the outer layer of the retina and removes metabolic waste19. The retina and choroid, as critical structures of the eyeball, can be affected by systemic pathologies or physiological conditions20,21. They have been found to play a significant role in the pathogenesis of specific ocular diseases, including macular degeneration, polypoidal choroidal vasculopathy, uveitis, glaucoma, and myopia-related chorioretinal atrophy22,23,24,25,26. Therefore, ocular function depends on both anatomically and functionally normal retinas and choroids.
While undernutrition has various effects on the eye, there is limited information available on the relationships between malnutrition and retinal or choroidal thickness in different genders. This study aims to assess potential changes in retinal or choroidal thickness in malnourished adults using the swept-source optical coherence tomography (SS-OCT) technique, which represents a significant advancement in retinal and choroidal imaging27. This technology is particularly effective in accurately identifying the choroidal scleral interface (CSI) in eyes with thicker choroids, thanks to its high penetration capabilities through the retinal pigment epithelium (RPE).
In this study, participants were categorized into two groups based on their BMI: the underweight group (BMI < 18.50 kg/m2) and the normal group (18.50 ≤ BMI < 25.00 kg/m2). The study included 996 right eyes of 996 underweight adults and an equal number of age- and gender-matched normal-weight subjects. The average BMI was 17.48 ± 0.75 kg/m2 in the underweight group and 21.30 ± 1.75 kg/m2 in the normal group.