Neuro-degenerative diseases

Vision problems are linked to many neurological conditions:-

Parkinson’s disease

Each year, about 60 000 people are diagnosed with Parkinson’s disease which involves the loss of specific neurons in a part of the brain called the substantia nigraWhile Parkinson’s is primarily characterized by tremors, rigidity, and postural instability, vague visual symptoms such as blurred and double vision, uncontrolled eye movements, light sensitivity, eye strain, and difficulty reading are common. Disruption of the visual system adds to the symptoms and limitations of difficulty with movement and coordination.

Mild ocular motor abnormalities occur in as many as 75% of patients with idiopathic Parkinson’s disease but often are left untreated. Yet because these symptoms can further reduce a patient’s already jeopardized quality of life and functionality, they warrant specialized treatment.

Alzheimer’s disease

Alzheimer’s disease is the most common form of dementia, and it is characterized by destroyed and damaged connections between neural cells.

Ocular degeneration in Alzheimer’s disease occurs as the retinal nerve fiber layer thins. Neurons responsible for visual processing tend to be damaged more than primary vision neurons, resulting in ambiguous vision symptoms in the early stages of the disease. Deficits in recognizing objects, seeing colors, and processing visual motion can occur at any stage, increasing the risk of accidents such as falls, lacerations, and burns. 

Vision rehabilitation includes stabilizing the oculomotor input to the visual system with the use of lenses and prism correction.

Multiple Sclerosis

A problem with vision is one of the most common symptoms of MS, and often one of the first that people with MS notice. The symptoms can include blurred vision, double vision (diplopia), optic neuritis, involuntary rapid eye movement and occasionally, a total loss of sight.

Problems with vision can result from damage to the optic nerve or from a lack of coordination in the eye muscles. The optic nerve connects the eye to the brain. Inflammation or demyelination in the optic nerve causes optic neuritis, which is experienced as a temporary loss or disturbance in vision and possibly pain behind the affected eye.

Typically, vision returns partially or fully within a few weeks. While it is quite rare for a person with MS to become totally blind, it is not at all uncommon for an individual to have recurrent episodes of optic neuritis over the course of the disease, usually in one eye at a time. Damage to the optic nerve can result in a blurring of vision, which may or may not totally resolve over time. Colour vision requires a great many nerve fibres from the eye for accurate transmission and is particularly susceptible to changes from demyelination.

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Macular degeneration

Age-related macular degeneration damages the macula (central area of the retina).  This can have a debilitating effect on a person as tasks that require central detailed vision, are difficult to perform.  These tasks can include reading, watching television and recognizing faces. 

Symptoms can include fuzzy, blurry, or distorted central vision. Dry AMD, the early stage of the condition, accounts for about 90 percent of cases.  Should the disease progress into wet AMD, bleeding, swelling, or fluid buildup can occur in the eye.

Certain patients with dry AMD can receive therapy to decrease the likelihood of developing vision loss associated with advanced disease.  Rehabilitation include the use of high powered lenses, telescopes, magnifiers and mobility training.