Vision problems are one of the most common physical conditions in the general populationAnd it is estimated that the vast majority of people suffer or will suffer from some type of visual problem throughout their lifetime. However, such a vision problem should not involve any degree of blindness.
There are certain criteria that make it possible to consider a vision difficulty as blindness or visual impairment. Throughout this article, we’ll talk about what blindness is, the different types that exist, and their associated symptoms, causes, and treatments.
What is blindness or visual impairment?
Blindness, also known as visual impairment or vision loss, is a physical condition that results in decreased ability to see to varying degrees and causes a number of difficulties that cannot be fully compensated for by it. use of glasses or contact lenses.
To be more exact, the term blindness is used to define that condition in which the loss of vision is complete or almost complete.
Vision loss can come on suddenly or suddenly, or develop gradually over time. Outraged, vision loss may be complete or partial; that is, it can affect both eyes or only one respectively. It can even be partial because it affects only certain parts of the visual field.
The range of causes that can lead to vision loss is extremely diverse and ranges from those that directly affect the eyes to those that involve the brain’s visual processing centers.
Outraged, vision disturbances usually become more common over the years, The most common risk factors are the development of physical conditions such as glaucoma, diabetic retinopathy, age-related macular degeneration or cataracts.
According to data from the World Health Organization (WHO), it is estimated that 80% of visual impairments are preventable or curable with treatment, including those caused by cataracts, infections, glaucoma, non-refractive errors. corrected, some cases of childhood blindness, etc.
In all other cases, people with a significant or complete degree of blindness may benefit from vision rehabilitation programs, environmental modifications and assistive devices.
Finally, in 2015, there were 246 million visually impaired people and 39 million blind people worldwide. Most of these people live in developed countries and are over 50 years old, but this may be due to a lack of data in developing countries.
Types of visual impairment
There are different types of visual impairment depending on the degree of impairment in the ability to see. This meaning can range from partial vision to complete blindness or visual impairment. The World Health Organization (WHO) has developed the following classification of the different types or degrees of visual impairment.
To measure the degree of disability, the vision of the better eye is taken into account, with the best possible correction of the lens. With this in mind, the classification is as follows:
- 20/30 to 20/60: slight vision loss or near normal vision
- 20/70 to 20/160: moderate visual impairment or moderate low vision
- 20/200 to 20/400: severe visual impairment or severe low vision
- 20/500 to 20/1000: almost total visual impairment or almost total blindness
- Lack of light perception: total blindness
In addition, depending on the specific vision conditions, visual impairment can also be classified as follows:
- Poor visual acuity and full visual field
- Moderate visual acuity and reduced field of vision
- Moderate visual acuity and severe loss of visual field
To better understand these terms, it should be noted that visual acuity is the resolution with which we see. In other words, the ability to perceive and differentiate visual stimuli. Whereas the field of view is the observable extent at a given time.
finally legal blindness or extremely poor visual acuity is considered such when the person has a visual acuity of 20/200, Even after with lens correction. There are a large number of people diagnosed with “legal” blindness who are able to distinguish shapes and shadows but cannot appreciate the details.
What about night blindness?
A very little known type of blindness is night blindness, also known as nyctalopia. This type of blindness is a condition that causes great difficulty or inability to see in relatively low light.
It can also be described as insufficient adaptation of vision to the dark and can be a symptom of various eye diseases such as retinitis pigmentosa, retinal detachment, pathological myopia or a side effect of certain drugs like phenothiazines. , among many other causes.
Causes of visual impairment
There are many common causes of visual impairment and blindness. However, their incidence varies considerably between the two conditions. The main causes of visual impairment to any degree can be:
- genetic defects
- Eye injuries
- Brain damage (cortical blindness)
- eye infections
- Poisoning or poisoning by methanol, formaldehyde or formic acid
- Other causes such as amblyopia, corneal clouding, degenerative myopia, diabetic retinopathy, retinitis pigmentosa, etc.
There are certain treatment options that can help correct vision defects and minimize possible major degeneration. The choice of one of these treatments will depend on the following considerations:
- Degree of visual impairment or blindness
- Causes of visual impairment
- Person’s age and level of development
- General state of health
- Existence of other conditions
- Patient expectations
Possible treatments or aids for the management of both visual impairment and blindness include:
- Control of the disease underlying the visual impairment
- Magnification systems such as lenses, telescopes, prisms or mirror systems
- Mobility aids such as canes, guide dogs or guide dogs or geolocation-based systems
- Reading aids such as braille, optical recognition applications, audiobooks, or reading devices that convert printed text into sound or braille
- Technological systems such as screen readers or amplifiers and Braille keyboards
- Brian, G. and Taylor, H. (2001). Cataract blindness: challenges for the 21st century. Bulletin of the World Health Organization, 79 (3): 249–256.
- Lehman, SS (2012). Cortical visual impairment in children: identification, evaluation and diagnosis. Current Opinion in Ophthalmology, 23 (5): 384–387.