Unseen Dimension of Cognitive Decline

Gisbi Susan Shaji, M. Optom

Junior Research Fellow, Manipal Academy of Higher Education, Manipal, India

Dementia has always caught the attention of researchers and physicians, as a complicated maze of neurological nuances. In the context of cognitive decline, the visual pathway serves as an informative indicator. Changes in the visual system, such as retinal thinning, altered contrast sensitivity, and compromised motion perception, contribute to a non-verbal narrative of cognitive decline. These observable alterations in visual function provide valuable insights into the progression of cognitive disorders. ⁽¹⁾ The visual system acts as a silent biomarker and can be instrumental in understanding and monitoring the aspects of cognitive decline. ⁽²⁾

In dementia studies, the visual system has generally been dominated by cognitive features, yet it emerges as a major point in our investigation. ⁽³⁾ Contrary to popular opinion, the impact of dementia extends beyond eye problems, posing a variety of challenges in the absence of ocular disorders.

Can Your Retina Reveal Secrets About Your Brain?

The eye is considered an extension of the brain, it shares neurons and derives from a neural tube. Consider the retina as a crucial player in capturing the essence of our visual world. It is a complex neurosensory tissue lining the inner surface of the eye and serves as a critical component in visual processing. The retina comprises multiple layers of specialised cells, including photoreceptors, bipolar cells, ganglion cells, and glial cells, working in concert to convert light signals into neural impulses. Photoreceptors, namely rods and cones, play a fundamental role in capturing and transducing light stimuli, initiating the visual information processing cascade. ⁽⁴⁾

Can retinal thinning be a prelude to cognitive decline?

Retinal thinning refers to a reduction in the thickness of the retinal layers, a process that can occur independently of ocular diseases. ⁽⁵⁾ While the anatomical intricacies of the retina are traditionally associated with visual acuity, recent investigations reveal that retinal thinning may be a notable marker in the context of cognitive decline associated with dementia. Studies have shown that individuals with dementia exhibit retinal thinning even in the absence of clinically diagnosed ocular pathologies. The correlation between retinal alterations and cognitive decline suggests a potential connection between neuro-degenerative processes affecting the central nervous system and changes in the eye. ⁽⁶⁾ While the exact mechanisms remain under investigation, several hypotheses propose that neuron-inflammatory processes, alterations in blood flow regulation, and the accumulation of abnormal protein aggregates may contribute to retinal thinning. ⁽⁷⁾ These changes could reflect broader neuro-degenerative processes shared between the eye and the central nervous system. The observation of retinal thinning in dementia has implications for early detection and monitoring of cognitive decline. Changes in the retina may precede cognitive symptoms, offering a potential avenue for identifying individuals at risk of developing dementia before clinical manifestations become apparent. The integration of advanced imaging technologies and an understanding of the potential mechanisms underlying retinal thinning opens new avenues for early detection, monitoring, and a deeper comprehension of the complex interplay between the eye and the brain in neurodegenerative processes.

Conclusion

With the use of cutting-edge imaging technologies like optical coherence tomography (OCT), eye care professionals like optometrists and ophthalmologists can detect important biomarkers during routine screenings, identify people who may be at risk of cognitive decline before symptoms appear, and monitor the course of the disease over time. They aid in the creation of novel approaches to early identification and intervention by conducting observational studies, clinical trials, and multidisciplinary research projects. By developing early detection and intervention strategies, they strive to improve outcomes and quality of life for individuals at risk of cognitive decline.

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