Visual impairment is an alteration in the visual apparatus that causes highly reduced visual acuity and has a considerable effect on one’s daily life.
There may be a variety of causes (congenital or acquired).
The term "visual impairment" can be used to describe very different vision disorders, from blurred vision, to a narrowing of the visual field (like looking through a tube), to the appearance of dark spots.
Those who are visually impaired have a reduced visual and spatial acuity, usually meaning that the visual field is limited.
There are many conditions that may bring about this disorder:
- Senile and juvenile macular degeneration: the vision worsens due to the appearance of a central scotoma
- Retinitis pigmentosa: atrophy of the rods, the photoreceptors needed for night and peripheral vision, causing a significant reduction in night vision and of the visual field.
- Diabetes: it can cause a serious retinal oedema with a consequent reduction in central visual acuity.
- Corneal abnormalities: advanced stage Keratoconus, opacity in the cornea of the eye, leukoma.
- Albinism: reduced central visual acuity, photophobia due to the absence of iris melanocytes and a high refractive error.
- Toxoplasmosis: if a central chorioretinitis appears, there is a significant decrease in visual acuity.
- Glaucoma: in extreme cases it creates an optic subatrophy with a subtotal lesion in the visual field.
The right corrective method is chosen according to two main criteria:
- Reduced visual acuity: optical and non-optical aids are used to enlarge images.
- Reduction in the visual field: optical aids are used to create an apparent increase in the angle of vision.
Reduced visual acuity
Magnifying aids are used to increase the dimensions of an image in different ways.
Angular magnification is the ratio between the angle of the object observed and the angle of the related image as provided by the optical aid.
Visual rehabilitation requires the collaboration of various professionals working as a team: the eye doctor, the orthoptist, the visual impairment technician.
Visual rehabilitation requires stimulation of the residual retinal function (the part that is still healthy) using light flashes (IBIS, ...); in addition our professionals try to find further aids which can improve the autonomy of those who are visually impaired.
Visual rehabilitation requires the use of magnifying devices and other aids. The objective is to be able to read, write and provide a better quality of life for the visually impaired patient (including the ability to use a computer).
It involves re-educating patients to carry out visual activities that they are no longer able to do, to improve eye movement and hand-eye coordination.