Blindness is not a disease but a condition caused by many eye diseases, and defined by a threshold of visual acuity or visual field.
The notion of visual impairment was defined and classified by the World Health Organization (WHO) based on two criteria that are objective acuity and visual field. It has defined five categories of visual impairment numbered I to V.
Classes I and II correspond to the so-called low vision:
- Category I : corrected binocular visual acuity less than 3/10th and 1/10th or higher with a visual field of at least 20 °.
- Category II : binocular corrected visual acuity less than 1/10th and 1/20th or greater. In practice, subjects count fingers at three meters.
The three categories correspond to the notion of blindness:
- Category III : corrected binocular visual acuity less than 1/20th and 1/50th or greater. In practice, the subject counting fingers at one meter but can only do three meters.
- Category IV : corrected binocular visual acuity less than 1/50th light perception but preserved. In practice, the subject does not count fingers at one meter or visual field less than 5
- Category V : absolute blindness. No light perception. A fortiori no eye.
Eyes Test (img thanks to telegraph.co.uk)
The blind or visually impaired deep would be about 207,000 (ie blind or have limited residual vision to distinguish the silhouettes of which 61 000 are blind complete). The visually impaired assets would be 932,000, with a severe visual impairment in distance vision (much difficulty or complete inability to recognize a face to four meters) or in near vision (much difficulty or complete inability to read, write or draw ). Finally, just over 560,000 people are visually impaired light.
The symptoms of blindness may be different depending on the pathology. Macular Degeneration Age-related (AMD) causes a loss of more or less profound central visual acuity, but patients retain an effective peripheral visual field. Vision loss in glaucoma the contrary, begins with an alteration in the peripheral visual field, and the achievement of central vision will be late. For patients with retinitis pigmentosa, an early clinical signs is night blindness, that is to say excessively difficult to see when it’s dark. Then came a loss of peripheral visual field. Vision loss in diabetic retinopathy is more complex and can have numerous causes: macular edema, macular ischemia, vitreous hemorrhage, retinal detachment.
Diseases purveyors of visual impairment and blindness in individuals over 60 years are numerous. They are not the same in industrialized and developing. In industrialized countries, AMD, diabetic retinopathy and glaucoma are the three main sources of pathologies severe visual impairment.In developing countries, cataract, trachoma and glaucoma are the leading causes of blindness.
Before the age of 60, the leading cause of blindness in industrialized countries is diabetes. Other causes such as retinal detachment, retinitis pigmentosa, trauma or congenital defects are rare.
Some of these potentially blinding diseases can be detected by regular examination by an ophthalmologist. These are low noise operating conditions for many years. Their screening and early treatment can prevent functional visual loss. This is the case of diabetic retinopathy for example, who should be screened by an annual review of the fundus, or chronic glaucoma, detected by the systemic pressure in the eye at every visit from 40 years . The appearance of a complicated form of AMD can be prevented, in subjects at risk, by a diet rich in fresh fruits, green vegetables and oily fish, and by taking supplements.
Once blindness or low vision is installed, there is not yet currently available cure, but many opportunities for rehabilitation are however possible. Low vision is the subject of much scientific research, and retinal implants are beginning to emerge. Patients who have benefited from this surgery were in research protocols, and this type of implant is not yet available to the general public.
For deficits of central vision, as in the AMD instance, the use of magnifying system or magnifier are valuable aids to distinguish the large print. These systems are available at centers specializing in optical “low vision”. It is also possible to perform an orthoptist with low vision rehabilitation, which is to center the view by setting the retina near the macula.
Deficits of peripheral vision, like retinitis pigmentosa, are sources of travel problems. Rehabilitation of locomotion with an instructor can learn to move avoiding obstacles.
Braille, finally, is a tactile method of reading for the blind, severely visually impaired reserved. This method requires good motor and cognitive functions.
Blindness, What can i do?
Driving is regulated by a decree of December 21, 2005. It is not allowed if the binocular visual acuity is less than 5/10, or if one of the two eyes acuity zero or less than 1/10 and the other eye to a visual acuity less than 6/10. For truck drivers, visual acuity in the better eye must be greater than or equal to 8/10, and at least one good eye greater than or equal to 5/10.
When traveling by public transport, the issue of a disability card by the MDPH can provide special rates and to recognize their rights.
Pedestrian traffic can be helped by using a white cane, and for people with total blindness, by using a guide dog.
Current means of communication can limit the sense of isolation. Phones and laptops are adapted to the visually impaired. Their keys are bigger, their simplified functions and voice recognition allows easy access to contacts in the phonebook or dial a number. Recently commercialized touch pads have proven to be a powerful means of communication for the visually impaired.
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