Causes of blindness and visual impairment in population aged 0-49 years

Important causes of blindness and visual impairment were different among people aged 0-49 years as compared to those aged more than that.

Out of 8 cases of blindness, 3 were due to other corneal opacity, 2 due to globe/ CNS abnormalities, 1 due to phthisis. There were 2 cases of blindness of which any cause could not be determined. Out of 8 cases of severe visual impairment, 3 were of globe/CNS abnormalities, 2 of non-trachomatous corneal opacity and one each of untreated cataract, cataract surgical complications and for one case cause could not be determined.

Definition of various categories of visual impairment
Blindness

Presenting visual acuity < 3/60 in better eye

Severe Visual Impairment (SVI)

Presenting visual acuity < 6/60 – 3/60 in better eye

Moderate Visual Impairment (MVI)

Presenting visual acuity < 6/18 – 6/60 in better eye

Early Visual Impairment (EVI)

Presenting visual acuity < 6/12 – 6/18 in better eye

Moderate Severe Visual Impairment (MSVI)

Presenting visual acuity <6/18-3/60 in better eye

Visual Impairment

Presenting visual acuity < 6/18 in better eye

Functional Low Vision

A person with impairment of visual functioning even after treatment and/or standard refractive correction, and a visual acuity of less than 6/18 to light perception, or a visual field of less than 10 degree from the point of fixation.

Cataract Surgical Coverage (Person) indicates how many persons received cataract surgery (one or both eyes) among all who were bilaterally pinhole blind due to cataract.
The numerator includes persons with one operated and one pinhole blind eye and persons with bilateral (pseudo) aphakia. The denominator includes the numerator, plus persons bilaterally pinhole blind due to cataract. Besides this, the indicator can also be calculated separately for PinVA <6/60 and <6/18.

Cataract Surgical Coverage (Eye) measures the proportions of eyes pinhole blind due to cataract, which have been operated so far.
The numerator includes all (pseudo) aphakic eyes. The denominator includes the numerator, plus eyes pinhole blind due to cataract. Besides this, the indicator can also be calculated separately for PinVA <6/60 and <6/18.

Table : Causes of blindness and visual impairment in population aged 0-49 years

Principal CauseBlindness (%)SVI (%)MVI (%)MSVI (%)EVI (%)VI (%)
Uncorrected refractive error0.00.038.233.388.729.6
Aphakia uncorrected0.00.00.00.00.00.0
Cataract untreated0.012.530.928.65.425.4
Cataract surgical complications0.012.50.01.60.01.4
Trachomatous corneal opacity0.00.00.00.00.00.0
Non-trachomatous corneal opacity37.525.09.111.10.014.1
Phthisis12.50.00.00.00.01.4
Glaucoma0.00.00.00.00.00.0
Diabetic retinopathy0.00.00.00.00.00.0
Age related macular degeneration0.00.00.00.00.00.0
Other posterior segment disorders0.00.03.63.20.62.8
Globe/CNS abnormalities25.037.510.914.31.815.5
Others/Undetermined25.012.57.37.93.69.9