For the first time, an international standard definition of blindness was developed and included in ICD-9 in 1975 [Table 1]. In this classification, the best corrected VA on the best eyes was used to divide VI into five categories: categories 1 and 2, which involve low vision, and categories 3 to 5, which involve blindness. The blindness criteria were better corrected VA below 20/400 in the best eye or visual field <10° around a central fixation. The aim was to facilitate the collection of international statistical data on CEW and blindness in a uniform manner that could be compared at the global level. Countries were advised to define blindness according to their own social and economic conditions, but to report internationally according to ICD-9 categories. [8,9] This classification system has been maintained in ICD-10, although the final diagnostic codes have been revised in accordance with ICD-10 conventions. Following the resolution adopted by the International Council of Ophthalmology in 2002 to revise ICD-10, WHO formed a consultation group recommending substantial changes to the classification. [10,11] These amendments were ratified in October 2006 for inclusion as a revision in ICD-10. [12] It was recommended to measure the va with both eyes open, with correction if necessary.

The limit for the definition of blindness was maintained, and patients with a VA of less than 20/400 or a field of view not exceeding 10° within a radius around the central attachment point in the best eye were assigned to blindness category 3. As part of this revision, the term “visual impairment” was replaced by two categories (1 and 2) of VI. Category 1 referred to descriptive VI <20/70–20/200 in the best eye (moderate VI) and category 2 to descriptive VI <20/200–20/400 in the best eye (severe VI). [12] This is the internationally accepted definition of blindness. 2) Expert Group on Vision Loss of the Global Burden of Disease Study. Trends in the prevalence of blindness and vision disorders from far and near over 30 years: an analysis for the Global Burden of Disease Study. Lancet Global Health 2020. doi: 10.1016/S2214-109X(20)30425-3 A review of the relevance of the current definition of blindness under the National Blindness Control Programme (NPCB), Government of India. Online search for published scientific literature and peer-reviewed guidelines using PubMed, World Health Organization (WHO) IRIS and Google Scholar with the keywords blindness and visual impairment, as well as offline review of reports from national and international organizations and their cross-references, was carried out until December 2016 to identify relevant documents for the definition of blindness. Evidence on the historical and currently adopted definition of blindness among the NPCB, WHO and other countries was reviewed. Differences between NPCB and WHO definitions were analysed to assess the impact of blindness and visual impairment on epidemiological status in India.

Differences in blindness criteria according to NPCB and WHO definitions lead to an overestimation of the prevalence of blindness in India. These variations are also associated with an over-representation of refractive errors as a cause of blindness and an under-representation of other causes as defined by the NPCB. The goals of eliminating blindness will also become much more difficult to achieve according to the NPCB definition. Ignoring the differences in definition when comparing the global and Indian prevalence of blindness leads to incorrect interpretations. We recommend that you make appropriate changes to the NPCB definition of blindness to bring it into line with the WHO definition. The bank also said it is the duty of the Medical Council of India to “take progressive measures so that a person suffering from CVD does not feel alienated from the concept of equality, which is the foundation of our constitution”. L`amicus curiae, M. Vishwanathan, argued that since color blindness is not considered a disability under the Persons with Disabilities Act 1995 or the Rights of Persons with Disabilities Act 2016, the nature and severity of color blindness and the corresponding topics it might practice must be studied. Inflammatory and infectious causes of blindness can be treated with drugs in the form of drops or pills.

Treatment for blindness depends on the cause of blindness. Differences in the definition of blindness affect not only the extent, but also the proportion of causes of blindness and VI. Uncorrected refractive errors are believed to be the most common cause of VI worldwide. In the Indian definition, severe component VI is included in the definition of blindness and, therefore, the proportion of uncorrected refractive errors is over-represented as a cause of blindness in India. Because of this distinction, other causes of blindness such as glaucoma, corneal morbidity and diseases of the posterior segment are underrepresented. The proportion of blindness due to uncorrected refractive errors in the 2001 National Survey was estimated at 19.7%. [26] The proportion of blindness due to uncorrected refractive error was one-quarter to 15% lower than that of blindness assessed compared to the 20/400 limit. The proportion of glaucoma blindness was 5.9% and 8.0% respectively for the NPCB and WHO thresholds.

[27] Legal blindness is a term used by ophthalmologists to determine eligibility for vocational training, education, rehabilitation, visual aids, disability benefits and tax exemption programs. This does not determine what a person can and cannot see. Legal blindness can be defined as a visual acuity of 20/200 or less in the eye that sees better with the best conventional correction. If you can only read the first line 20 feet away on the graph of Snellen`s eye, visual acuity is recorded at 20/200. If this is the case, the person is considered legally blind. If you are concerned that your child may have vision problems, you can always contact a specialized pediatrician to determine if your child is experiencing visual impairment, legal blindness, or any other eye problem that can be treated to restore your child`s vision.