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Visual or vision impairment (VI or VIP) is the partial or total inability of visual perception.In the absence of treatment such as corrective eyewear, assistive devices, and medical treatment, visual impairment may cause the individual difficulties with normal daily tasks, including reading and walking. [6]
Vision rehabilitation (often called vision rehab) is a term for a medical rehabilitation to improve vision or low vision. In other words, it is the process of restoring functional ability and improving quality of life and independence in an individual who has lost visual function through illness or injury.
The term neurological visual impairment (NVI) covers both CVI and total cortical blindness. Delayed visual maturation, another form of NVI, is similar to CVI, except the child's visual difficulties resolve in a few months. Though the vision of a person with CVI may change, it rarely if ever becomes totally normal.
Cortical blindness-Cortical blindness is the total or partial loss of vision in a normal-appearing eye caused by damage to the brain's occipital cortex. [ 7 ] Retrobulbar neuritis - Retrobulbar neuritis cause of visual loss with normal fundus but there will be relative afferent pupillary defect (RAPD) and abnormal visually evoked responses .
Low vision is both a subspeciality and a condition. Optometrists , Opticians and Ophthalmologists after their training may undergo further training in Low vision assessment and management. There are various classifications for low vision, this varies from country to country and even from state to state.
The majority of patients will progress to legal blindness, which means that central reading vision will be lost. However, perimetry and microperimetry studies indicate that the peripheral light sensitivity is preserved over a long time in a significant fraction of all patients (i.e., >50%).
In NPCB survey (2001–2002) Corneal opacity was the 6th major cause of blindness in India, which accounts for 0.9% of total blind population. In the RAAB (Rapid Assessment of Avoidable Blindness) survey (2006–2007) Corneal opacity including Trachoma was mentioned as the second major cause of blindness, which accounts for 6.5% of total blindness.
ONH is the single leading cause of permanent legal blindness in children in the western world. [12] The incidence of ONH is increasing, although it is difficult to estimate the true prevalence. Between 1980 and 1999, the occurrences of ONH in Sweden increased four-fold to 7.2 per 100,000, while all other causes of childhood blindness had declined.