Does Dementia Affect Your Eyesight?

For many people, 'dementia' is synonymous with memory loss. However, it is a complex syndrome caused by progressive disorders that affect the brain, and its effects can extend far beyond cognition. A crucial area often overlooked is vision.

Dementia doesn't typically damage the eyes themselves, but rather the parts of the brain responsible for interpreting the visual information from the eyes. This leads to difficulties in visual processing and perception, which can be profoundly confusing the individual and their carers. Furthermore, it is important to note that many common age-related eye conditions also coexist with dementia, complicating the issue.

1. Cerebral Visual Impairment: The Problem is in the Brain

The most significant way dementia affects 'eyesight' is by causing a condition known as Cerebral Visual Impairment (CVI) or perceptual problems. In this scenario, the eye may be perfectly healthy and have excellent visual acuity (sharpness), but if the brain cannot correctly process the signals, the person will still experience profound sight problems. It’s a disconnect between "seeing" and "understanding."

These difficulties arise from the progressive degeneration or damage to the neurons in the parts of the brain—particularly the posterior cortical regions (the occipital and parietal lobes)—that handle visual information and spatial awareness.

Key Visual Processing Issues in Dementia

• Loss of Depth Perception (Stereopsis) - Difficulty in judging how far away objects are or changes in elevation. This can result in falls, difficulty using stairs, missing a cup when reaching for it, anxiety with escalators.
  

• Reduced Contrast Sensitivity - Trouble distinguishing between objects and their background when colours or shades are similar. For example, this makes it hard to pale food on a pale plate. It can also make reading black text on a dark background difficult.
  

• Visuospatial Disorientation - Trouble understanding the relationship between objects in a space. This increases the risk of getting lost in familiar environments, bumping into furniture or door frames and misjudging distances when walking or driving.
  

• Object/Face Recognition (Agnosia) - Difficulty recognising familiar objects, people (Prosopagnosia - face blindness), or places, even though they can physically see them. This could manifest by mistaking a coat rack for a human being or failing to recognise a close family member.
  

• Akinetopsia (Motion Blindness) - An inability to perceive smooth movement, seeing motion as a series of still images. Making it difficult to track moving vehicles or follow a conversation in a busy environment.
  

• Pattern and Glare Sensitivity - Increased discomfort or confusion from shiny surfaces, busy patterns, or bright light/glare. Shiny floors may be perceived as wet or as a painful glare, while patterned carpets can look like a hole in the ground or a surface that moves.

2. Posterior Cortical Atrophy (PCA): The Vision-First Dementia

One specific and rare form of dementia, Posterior Cortical Atrophy (PCA) (sometimes known as Benson’s syndrome or the 'visual variant' of Alzheimer's disease), is often characterised by vision problems being the first and most prominent symptoms, sometimes years before significant memory loss occurs. PCA primarily damages the back of the brain (the occipital and parietal lobes), which are key centres for visual and spatial processing.

The symptoms of PCA are a heightened expression of the visual processing difficulties listed above, and can include:

• Simultanagnosia: An inability to see more than one object at a time. The person may only see a single tree, but not the whole forest.
  

• Optic Ataxia: Problems with eye-hand coordination, where the person cannot accurately reach for or point to an object they can see.
  

• Oculomotor Apraxia: Difficulty voluntarily moving the eyes to follow an object or a line of text.

People with PCA frequently visit optometrists and ophthalmologists repeatedly in the early stages, believing the problem lies with their eyes, leading to misdiagnosis and delayed treatment for dementia.

3. The Coexistence of Ocular Disease and Dementia

It is vital to consider that dementia is most common in older adults, who are also more susceptible to age-related eye conditions. For a person living with dementia, having both cognitive decline and sight loss from an eye disease can significantly increase confusion, disorientation, and the risk of falls.

Common eye conditions that frequently occur alongside dementia include:

• Cataracts: Clouding of the eye's lens, leading to blurry vision, difficulty seeing in dim light, and reduced colour vibrancy. Cataract surgery is often very successful and can dramatically improve a person's quality of life and decrease confusion.
  

• Age-related Macular Degeneration (AMD): Damage to the central part of the retina causing a loss of central vision, which affects tasks like reading and recognising fine detail.
  

• Diabetic Retinopathy: Damage to the blood vessels in the retina caused by diabetes, leading to blurry or patchy vision.

Furthermore, studies have suggested a link between certain eye conditions (particularly cataracts and diabetic retinopathy) and an increased risk of developing dementia. Whether one causes the other, or if they share common biological risk factors (such as inflammation or vascular changes), is a subject of ongoing research.

4. Practical Support and Environmental Adaptations

Understanding the visual challenges faced by a person with dementia is the first step towards providing effective support. Since the vision problems are rooted in the brain, environmental adjustments are often the most successful interventions.

• Maximise Contrast - Use high-contrast colours for important items: e.g. a dark-coloured plate on a light placemat. This will help overcome reduced contrast sensitivity and poor depth perception.
  

• Simplify the Environment - Remove unnecessary clutter, busy patterns, or objects that might be misinterpreted. Less visual information will make it easier for the brain to process the most important elements.
  

• Improve Lighting - Ensure there is bright, even lighting throughout the home to minimise confusing shadows and dark corners which can appear as holes. This will help mitigate shadows, which can be too readily misinterpreted as obstacles.
  

•  Reduce Glare - Use blinds or net curtains to soften direct sunlight and avoid overly shiny or reflective surfaces (like highly polished floors or large mirrors). This will help reduce the pain and disorientation of light sensitivity prompted by glare.
  

• Check Eyesight Regularly - Regular, adapted eye tests will ensure glasses prescriptions are up-to-date and will check eye health.

Living with dementia

A person with dementia may find that their surroundings look distorted, giving rise to confusion and possibly, fear. By addressing both underlying eye health concerns and adapting the environment to mitigate cerebral visual impairment, carers and healthcare professionals can make a significant difference to their daily life, safety, and well-being.