Key medical criteria to assess functional restrictions

In looking at the question of disability in the visually impaired, we are assessing three main criteria:

• Binocular visual acuity for distant vision, corrected with spectacles or lenses.
• Binocular visual acuity for near vision, corrected with spectacles or lenses.
• Visual fields.

We would regard for a mild visual impairment, a visual acuity for distant vision to be better than 6/18, for a moderate visual impairment, a visual acuity to be 6/18 or more, but better than 6/36, (or registered partially-sighted), and for a severe visual impairment, a visual acuity of 6/36, or worse (or registered blind).

For near vision, corrected binocular visual acuity for mild impairment would be up to, and including N24, for moderate, worse than N24, up to N36, and for severe, worse than N36.

With visual field loss, the different types of loss are considered:

• Peripheral field loss in absolute value (or percentage loss) in full binocular visual field. That is, blindness on the edge of vision,
• OR hemianopia (blindness in half the field of vision),
• OR binocular central field loss, that is, blindness in the centre of vision.

Mild, moderate or severe impairment, and subsequent disability depends on the amount of visual field that is missing.

This information is most readily available from the Optician or Ophthalmologist.

The question of registration of blindness and partial sight will also be raised.

Disabling effects of visual acuity loss, or visual field loss, on the individual’s activities of daily living are assessed, bearing in mind the diagnosis, treatment, and likely prognosis.