Trends of causes of blindness and visual impairment over the years in population aged ≥ 50 years

Cataract continue to be the major cause of blindness and responsible for 66.2% of blindness. Refractive error was the most important cause of visual impairment and second important cause of blindness in 2001 but the current survey showed that refractive error is not an important cause of blindness. Corneal blindness emerged as the second important cause of blindness. Beside this, the proportion of blindness due to complications of cataract surgery have also increased.

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.