Visual field assessment in low vision

A visual assessment is a direct evaluation of the properties of a physical asset that are visible by the naked eye and can be evaluated directly in the field. Low vision is both a subspeciality and a condition. Visual condition inspections are suitable for a wide range of assets.

Experts define low vision as “A person who has impairment of visual  functioning even after treatment and/or standard refractive correction, and has a visual acuity of less than 6/18 to light perception, or a visual field less than 10degrees from the point of fixation, but who uses, or is potentially able to use, vision for the planning and/or execution of a task for which vision is essential.”

Causes of visual impairment

Congenital blindness occurs in babies, whereby they are born blind. Congenital blindness can be caused by a number of things- it can be inherited, for instance, or caused by an infection (like German measles) that’s transmitted from the mother to the developing fetus during pregnancy.

Amblyopia is reduced vision in an eye caused by lack of use of that eye in early childhood. Some conditions cause a child’s eyes to send different messages to the brain, for instance, one eye might be working better than the other. The brain may then turn off or suppress images and vision from the weaker eye and then stops developing normally, this is also known as a “lazy eye.”

Trachoma occurs when a very contagious microorganism known as Chlamydia trachomatis causes inflammation in the eye. It is often found in poor rural countries that have overcrowded living conditions and limited access to water and sanitation.

Cataracts are cloudy areas in part or all of the lens of the eye. In people without cataracts, the lens is crystal clear and allows light to pass through and focus on the retina. Cataracts prevent light from easily passing through the lens, thereby causing loss of vision. Usually elderly people are affected by cataracts the most and sometimes babies are also born with congenital cataracts.

Glaucoma is an increase in pressure in the eye. The increased pressure impairs vision by damaging the optic nerve. Glaucoma is mostly seen in older adults, although babies may be born with the condition and teens can sometimes develop it as well.

Tests for vision impairment

When someone goes for an examination, the doctor thoroughly examines the structure of the person’s eye. The doctor will also perform a variety of tests, including- visual acuity test, visual field test and tonometry test.

Visual acuity test– the doctor makes you read an eye chart to measure how well he or she sees at various distances. Visual acuity refers to your ability to discern the shapes and details of the things you see. No risks are associated with visual acuity tests, and you don’t need any special preparation.

Visual field test– ophthalmologists use this test to measure side, or peripheral, vision. A visual filed test can determine if you have blind spots (called scotoma) in your vision and where they are.

Tonometry test– this test determines the fluid pressure inside the eye to evaluate for glaucoma. The most common type of tonometry test is called the “Goldmann applanation tonometry test.” It involves the use of flat-tipped probe that is gently pressed against he surface of your eye.

If your doctor determines that you have an eye condition that is likely to cause visual impairment, many treatments are recommended. Options may include eyeglasses, contact lenses or eye drops. Surgery maybe required in some cases. For instance, cataracts are often treated by removing the clouded lens and replacing it with an intraocular lens (an artificial plastic lens that requires no special care and restores vision).