EYES:THE LIGHT OF THE BODY (Continue)

VISION TESTING/GRADING OF VISION

VISION: This is the ability to see and seeing is a function of the eye,(it's diopteric apparatus and retina), optic nerve, visual tracts and the brain.

THE EYE

VISION ASSESSMENT:
1) Visual Acuity- most important
2) Visual Fields
3) Color Vision.

Visual acuity testing is usually done using the SNELLEN'S chart at a distance of 6m/20ft
for distance vision and near vision chart at a distance of 30cm .



BLINDNESS
Blindness and visual impairment varies widely globally i.e fro one region of the world to anther. Overall prevalence is about 0.7% worldwide. Ranging btw 0.3%-1.4% between developed and underdeveloped countries.

Avoided blindness (i.e treatable and preventable blindness) constitutes about 75-85% of blindness.  1:40 global population are either blind or visually impaired. Giving a figure of about 32mm blind and 110m with visual impairment.

In Nigeria Blindness Prevalence in people of 40 years and above is 4.2% presenting vision and 3.4% corrected vision.

Several visual impairment 1.5% presenting, vision, 0.8% corrected vision.
for all age groups prevalence is about 0.78% 1.13M blind, 2.7M Moderate VI, 0.4M severe VI total of 4.25M, 84% are due to Avoidable blindness.

CAUSES OF BLINDNESS
1) CATARACT (43%)

CATARACT

A cataract is an opacity of the normally clear lens which may develop as a result of aging, metabolic disorders, trauma or heredity.


2) GLAUCOMA(16.7%)

3) UNCORRECTED APHAKIA(8.4%)
4) CORNEAL SCARS(7.8%)
5) TRACHOMA(4.2)
6) OPTIC ATROPHY(3.79%)
7) PHTHISIS BULBI/ABSENT GLOBE(2.3%)
8) MACULAR DEGENERATION(1.8%)