Main causes of blindness

Dr. Katia Cabrero Feria, Micro-surgeon Ophthalmologist, glaucoma sub-specialty. Ophthalmology of the General Hospital of the Plaza de la Salud.

Blindness is the total or partial loss of light sensitivity. The main causes of blindness worldwide are cataracts, glaucoma, age-related macular degeneration, diabetic retinopathy, trachoma and childhood eye conditions, such as those caused by vitamin A deficiency.

Age-related blindness and that due to uncontrolled diabetes are increasing worldwide, while infectious-cause blindness is decreasing thanks to public health measures.

According to the World Health Organization (WHO) the estimated number of people with visual impairment is 253 million: 36 million with blindness and 217 million with moderate to severe disability.

Statistics indicate that 90% of the world's blind are in developing countries. And African and Asian women make up 2/3 of the total.

Three quarters of cases of blindness are preventable or treatable.

Among the causes of blindness we have those that can be reversed with medical or surgical treatment, such as cataracts, and irreversible ones, such as glaucoma.

The population with the greatest risks is that of patients over 50 years of age, since they are more predisposed to suffer visual impairment due to chronic eye diseases, and at the other extreme we have those under 15 years old. It is estimated that the number of children with visual impairment amounts to 19 million, of which 12 million suffer from it due to refractive errors.

Approximately 1.4 million children under 15 suffer irreversible blindness and need access to visual rehabilitation services to optimize their functioning and reduce disability.

As we mentioned, many of these causes can be determined with a complete ophthalmologic examination performed by a medical professional. In it, the ophthalmologist will not only determine if the patient needs corrective glasses, but observe signs of possible asymptomatic alterations that could cause an irreversible loss of vision. It is also possible to detect alterations secondary to systemic diseases such as diabetes and hypertension and even signs of brain tumors.

According to WHO, there are four levels of visual acuity (VA): normal vision, moderate visual impairment (VA <20/40), severe visual impairment (VA <200) and blindness (AV <20/400).

The majority of blind people in developing countries live in rural areas, while the majority of ophthalmological services and hospitals are located in cities. 90% of blind people in developing countries cannot work, which causes a reduction in social status and decision-making capacity.

Life expectancy is half or less if we compare with people without visual impairment.

About cataract, glaucoma ...

Waterfall: It is the opacity of the natural lens of the eye called crystalline. It is normal for it to appear with age, although there may be congenital or secondary causes of diseases and trauma.

Glaucoma: It is a disease that damages the optic nerve in a slow, progressive and silent way, bringing with it a deterioration in the visual field. It is usually caused by an increase in intraocular pressure, and is the leading cause of irreversible blindness worldwide.

Diabetic retinopathy: It is the involvement of the retinal microvasculature caused by diabetes mellitus. It can cover a broad spectrum of damage, from the dilation of small blood vessels (micro aneurysms) to extensive intraocular bleeding that causes retinal detachment and painful inflammatory glaucoma.

Age-related Macular Degeneration (AMD): It is a disease of the retina that affects the central area of vision (the macula). The patient has a significant deterioration in functions such as reading and visualization of fine details such as colors and contrast.

Ametropias: Refractive defects (myopia, farsightedness, astigmatism) should be detected in children. A difference in refractive error between one eye and another that can lead to amblyopia or lazy eye, which implies an abnormal development of vision.

Trachoma: It is an infection caused by a bacterium that causes opacification of the cornea.

Treatment of the causes of blindness.

The world of ophthalmology has been revolutionized with the emergence of high technology and the introduction of lasers and equipment that allow the patient to operate in safer conditions and with higher quality.

Advances in femtosecond lasers for cataract surgery and correction of refractive defects have increased efficiency in these surgeries.

For the treatment of glaucoma, which represents the first cause of irreversible blindness, topical therapy with drops is the most used. There is also surgical treatment with a wide range of new minimally invasive intraocular drainage devices.

The innovation in intraocular drugs and retinal equipment have made possible better treatments for diabetic retinopathy, although systemic control of the disease remains the cornerstone in preventing its deterioration.

Regarding AMD, there are intravitreal drug treatments for the wet variety. Unfortunately, there is currently no treatment for dry AMD. However, patients could benefit by taking certain combinations of vitamins and minerals.

The causes of blindness of infectious origin such as trachoma, which is more endemic to poor countries, have been reduced with the use of antibiotics and environmental improvement campaigns.