It is a common experience in middle age to have vision problems, get the eyes tested and be fitted with prescription glasses. Most of us will start seeing well again. However, some individuals are found to have normal vision on standard eye test, even when they continue to experience difficulties with vision. Their declining vision could be one of the early signs of a lesser known visual variant of Alzheimer’s disease, known as Posterior Cortical Atrophy (PCA).
PCA is a progressive degenerative condition characterized by the loss and dysfunction of brain cells in the outer layer (cortex) of the back of the brain (posterior) which is responsible for processing visual information received through the eyes.
The most common underlying cause of PCA is Alzheimer’s disease. Rarely other neurodegenerative diseases such as Lewy body dementia, corticobasal degeneration and Creutzfeldt-Jakob disease may cause PCA.
Symptoms of PCA are commonly seen at an earlier age than classical Alzheimer’s disease, with the earliest symptoms presenting in early-mid fifties or early sixties. However, it can also affect older people.
The person may simply say that their vision is blurry, or that they cannot clearly see. The most common feature of PCA is subtle problems with visual perception and spatial orientation of objects.
Some of the common initial symptoms of PCA include difficulty reaching out and getting objects, difficulty differentiating objects from the background, filling out forms, difficulty driving, and having problems assessing distance and depth.
In course of time persons with PCA might find it difficult to wear a seat belt, button their shirt, and do things with their hands. They might also bump into door frames and glass doors.
As the disease progresses, over a period of two to three years, the person may develop problems with cognition such as word-finding difficulty and short-term memory loss, similar to Alzheimer’s disease.
Persons with PCA are usually seen by the optician or the eye specialist first because of their vision problems. Since PCA is not an eye problem, the vision tests are often normal. Sometimes it takes about three to four years to get the correct diagnosis.
There is no single test to diagnose PCA. In order to help physicians diagnose the condition early, an International Consensus on the first diagnostic guidelines for PCA has been developed recently.
Diagnosis is made on the basis of symptoms, detailed eye exam, blood tests to rule out metabolic causes of dementia, CT/MRI of the brain, special scans such as FDG-PET, and SPECT to assess the glucose uptake and blood flow in the different parts of the brain respectively, and cognitive assessment.
Currently there is no cure for PCA; however, medications that are used to treat Alzheimer’s disease, such as Aricept, Exelon, and Reminyl, can be tried in persons with PCA. Non-medical interventions to slow down the progression of cognitive symptoms, including physical and mental exercises, Mediterranean diet, stress reduction strategies, and treatment of high blood pressure, diabetes and depression are also an integral part of treatment.
Home improvements such as increasing lighting while decreasing glare, using coloured plates and cups, painting door handles, frames and light switches, and using stained glass or stickers on patio doors and glass doors, help the person to maintain their functioning and independence.
Assistive technology and visual aids including talking clocks and watches, mobile phones with simplified displays, cooking aids with sensors to alert the person when food starts burning, audio books, iPad reading app etc. also help support persons with PCA.
Padmaja Genesh, who holds a bachelor degree in medicine and surgery as well as a bachelor degree in Gerontology, has spent several years teaching and working with health care agencies. Please send your comments to padmajaganeshy@yahoo.ca