Signs and symptoms affecting the retina, optic nerve and posterior afferent visual system could be a useful early manifestation for ophthalmologists to diagnose the Alzheimer's diseasea progressive and debilitating condition that is the most common form of dementia.
Early diagnosis of Alzheimer's is certainly a win-win situation, both for patients and healthcare professionals. Indeed, although there is still no treatment that can prevent progression or resolve this condition, early recognition and intervention on known risk factors can reduce both the severity of the disease and its rate of progression.
Currently, however, there is no screening dedicated. Moreover, cognitive decline is gradual and can often go unnoticed in the early stages. For this reason, patients frequently present themselves to the clinician in more advanced stages of the disease.
Ophthalmic symptoms of the disease
Dr. Sergott, director of the Neuro-Ophthalmology Service at Wills Eye Hospital and founder and CEO of the Annesley EyeBrain Center at Thomas Jefferson University in Philadelphia, Pennsylvania, in a recent article published in Ophthalmology Times, emphasised the importance of assessing signs and symptoms, which are often difficult to interpret, in patients aged 55 years and older. With diseases such as Alzheimer's and Parkinson's disease, in fact, patients often resort to consulting an ophthalmologist first rather than a neurologist because of the associated visual disturbances.
The ophthalmic manifestations of Alzheimer's disease present with a wide variety of symptoms, including difficulty in perceiving movement or recognising objects and colours. Difficulties in reading and orientation may also occur, appearing in patients who are on average 50-65 years old. Symptoms also include loss of depth perception and dysfunction of the photoreceptors, manifested by glare and night blindness.
Visual-spatial function as a cognitive marker
Recent studies suggest precisely that in Alzheimer's disease, visuospatial disorders develop before memory problems, and thus may represent an early diagnostic tool. In particular, visual-spatial dysfunctions are thought to be among the earliest manifestations of this disease and are present in 20-43% of patients, and it has been suggested that the decline in these functions may even be present five to six years before diagnosis.
Visual-spatial function could, therefore, be a potential marker cognitive for the detection of Alzheimer's before it has reached its clinical manifestation.
Certainly, along with these visual symptoms, it is crucial to recognise patients who also present with memory impairments, which could suggest a more global deficit in visual processing. Other diseases similar to Alzheimer's disease, such as Lewy body dementia and prion disease, may also present with similar visual symptoms.
The multifocal electroretinogram (ERG), which allows the electrical response of the macular region to be isolated in cases of central visual function deficit, does not associated with visible retinal changes on fundus examination, is the most sensitive test for identifying retinal abnormalities in patients with dementia syndromes.
Physicians are therefore advised to pay attention to patients with visual field defects who have problems with the automated perimetric test. Another clinical condition that should alert ophthalmologists and neurologists to the possible diagnosis of Alzheimer's disease is the presence of homonymous hemianopsia, detected with a normal MRI scan.
In conclusion, although there are currently no treatments available to cure Alzheimer's disease, the increasingly effective drugs available for this condition bode well for the future, but there is no doubt that early intervention can improve patients' prognosis.
This is precisely why the role of ophthalmologists in recognising early symptoms of Alzheimer's can be so valuable for diagnosis and for ensuring a better quality of vision and life for patients.
Bibliography
- Lynda Charters, Diagnosing Alzheimer's disease: Ophthalmologists have role in early detection, Digital Edition, Ophthalmology Times: June 15, 2021, Volume 46, Issue 10
- Paris Dickens and Kanna Ramaesh, The Evolving Role of Ophthalmology Clinics in Screening for Early Alzheimer's Disease: A Review, Vision 2020, 4, 46; doi:10.3390/vision4040046
Dr. Carmelo Chines
Direttore responsabile
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