Blindness is the condition of lacking visual perception due to physiological or neurological factors. Total blindness is the complete lack of form and visual light perception and is clinically recorded as NLP, an abbreviation for "no light perception."  Blindness is defined by the World Health Organization as vision in a person's best eye of less than 20/500 or a visual field of less than 10 degrees. The definition of blindness used in Nepal differs from that used by the WHO.Both use presenting visual acuity as basis for their definition but, in Nepal the threshold is at 6/60 whereas the WHO in ICD-10 uses 3/60.

Preventable blindness is defined as blindness which could be either treated or prevented by known, cost-effective measures or effective preventive or prophylactic measures e.g.  xerophthalmia, trachoma, and glaucoma. They are conditions that are amenable to primary prevention, i.e. where the condition causing blindness could have been entirely prevented. The major causes of preventable blindness are:

§  Cataract

§  Posterior segment disease

§  Glaucoma

§  Corneal scar

§  Trachoma

§  Uncorrected  Aphakia

§  Ophthalmia neonatorum [Disease transmission through the birth canal]

§  Use of harmful traditional eye remedies/medication

Major Risk factors for Preventable blindness:

 Age: Preventable Blindness is unequally distributed  across age groups ,as more than 82% of all blind people are 50 years of age or older. Prevalence of blindness among children is about 10 times lower than that among adults. However, Childhood blindness remains a high priority because of the expected number of years to be lived in Blindness .

Gender: It is estimated that females in every region of the world and  of all ages have a significantly higher risk of being visually impaired than males, mostly because of their longer life expectancy and ,in poorer societies, because of their lack of access to services.

Socio-economic status: More than 90% of the world’s visually impaired people live in developing countries.

Others: Tobacco use, smoke and exposure to ultraviolet radiation ,vitamin A deficiency, high body mass index and metabolic disorders.

Nepal is one of the first countries where a nation-wide population-based survey on blindness and visual impairment was done in 1980-81.Between 2006 and 2010 ,population based surveys on blindness and visual impairment were conducted in all fourteen zones of Nepal. The main purpose of these surveys was to assess the prevalence of blindness and visual impairment,to compare the present situation of blindness and visual impairment with the findings of the Nepal Blindness Survey(NBS) in 1981.It was done in order to evaluate the achievement and impact of the eye care system and to provide baseline data for future planning of eye care services in Nepal.

                      The eye care infrastructure in 1981 was minimal, with only one eye hospital and four eye departments in general hospital for the entire country .In 2010,there were 20 dedicated eye hospitals,19 eye departments and 63 primary eye care centres .The number of ophthalmologists increased from 7 to 147.

The impact of the expansion of eye care services between 1981 and 2011 is best visible in the reduction of the prevalence of blindness and visual impairment. In actual numbers the achievements are far less outspoken because the number of  people aged 50+ more than doubled between 1981 and 2011 and the life expectancy at birth increased from 48 to 66 years.