The WHO Global Initiative to Eliminate Avoidable Blindness, “VISION 2020: The Right to Sight”, aims to eliminate these diseases as a public health problem by the year 2020. These diseases, along with uncorrected refractive errors, may be controlled since they have effective strategies for elimination and control. The most important of these is cataract, and other diseases include glaucoma (12.3%), age-related macular degeneration (AMD) (8.7%), corneal opacities (5.1%), diabetic retinopathy (4.8%),
Cataract is the leading cause of visual impairment worldwide (47.9%), except for certain developed countries. Cataract results from a clouding of the lens of the eye, causing decrease in vision. Cataract is normaally an age related change in the lens, but disease such as diabetes, and trauma, can accelerate cataract formation. Cataracts can affect any age group, even newborn children.
Cataracts are easily curable with surgery, and the newer cataract surgical techniques are safe and effective. Since many people do not have access to medical care, cataract remains a significant public health care burden.
Glaucoma usually results when the fluid pressure inside the eyes slowly rises, damaging the optic nerve. It is usually asymptomatic in the initial stages, and a comprehensive eye exam alone can detect it.
There are two kinds of glaucomas, angle closure being more common in south-east Asians, while the open angle variant is more common in Caucasians. The incidence of blindness due to angle closure disease is almost three times that of the more common open angle glaucoma. As of now, there is no “cure” for glaucoma but early diagnosis and treatmentcan control the disease process so that blindness may be prevented.
Age-related macular degeneration (AMD) results due to the development of abnormal blood vessels at the macula (Wet AMD), or death of light-sensitive cells at the macula (Dry AMD). The macula is the most light sensitive part of the centre of the retina, which is responsible for perception of finer details and central vision. AMD therefore results in loss of central vision, unlike glaucoma which affects peripheral vision first. The disease is not preventable, but can be treated. Treatment of AMD involves injections into the eye (Lucentis and Avastin; Ranibizumab and Bevacizumab, respectively) and/or lasers.
Corneal diseases result in corneal scarring, and decrease/ loss of vision, especially in children and young adults. The main causes include trachoma, trauma, onchocerchiasis and corneal ulcers. Most of these diseases are preventable and curable in the early stages with relatively minor interventions. The WHO programs for the prevention and management of trachoma and onchocerciasis aims at providing eye health care to vulnerable groups, especially in parts of Asia and Africa. Visual rehabilitation of these patients usually requires a corneal transplant.
Diabetic retinopathy is usually asymptomatic, and it is therefore essential for diabetics to undergo an annual dilated retinal evaluation.
Diabetes can cause abnormalities in the small blood vessels in the retina, including new blood vessel formation,resulting in leakage and bleeding from these vessels. If this leakage is at the macula, the most sensitive part of the retina, loss of vision results. Diabetic retinopathy may be treated with lasers, injections into the eye, and/or surgery. Blindness due to diabetes is largely preventable with timely interventions and adequate blood sugar, blood pressure and cholesterol control.
The WHO database from 2002 provide the first estimates of global burden of visual impairment:
- Globally, in 2002 more than 161 million people were visually impaired, of whom 124 million people had low vision and 37 million were blind.
- In this statistic, refractive error as a cause of visual impairment has not been included, which means that the actual magnitude of visual impairment is significantly more.
- For each person who is blind, an average of 3.4 people have low vision (regional variation ranging from 2.4 to 5.5).