Humans are able to see the world with a pair of eyes. The beauty of the world can be enjoyed with eye vision. This blessing in disguise is often a thing that is taken for granted. It is important for humans to take care of their eyes so that they can continue to enjoy what the world can offer. However, not everyone is lucky to have good eye vision. Some may have visual disturbance or even impairment. In this DoctorOnCall’s article, we will be learning if low vision is the same as blind.
Before learning about low vision and blind, it is worth knowing how exactly humans are able to see. First, light passes through the cornea (the clear front part of the eyes). Some of the light enters through an opening known as the pupil. The iris (the coloured part of the eyes) controls the amount of light entering the eyes. The light then passes through the lens (a transparent part of the eyes). Lens and cornea work simultaneously to focus light onto the retina. Light needs to be focussed on the retina (layer of tissue at the back of the eyes) in order for the brain to perceive the image seen. There are many photoreceptors, special cells on the retina that turn light into electrical signals. These electrical signals travel from the retina to the brain through the optic nerve. The brain will translate these signals into images.
When there is disruption in the way humans see images, problems such as low vision or blindness may occur. There are many reasons that cause these visual problems to occur. Among these reasons are are-related, diabetes and other eye problems such as cataracts, glaucoma and eye cancer. Trauma to the eyes or brain injury may also become the causes. Inherited disorders may also contribute to vision issues. Uncorrected refractive errors can lead to low vision or blindness when left unattended for a long period of time.
The question now is, is low vision the same as blindness. No, it is not the same thing. It is important to differentiate between the two as these two conditions have different outcomes and need different management. Low vision is defined as visual acuity between 3/60 to 6/18 or when the visual field is less than 20 degrees in the better eye despite the best possible corrections. Blindness is defined as visual acuity less than 3/60 or visual field less than 10 degrees in the better eye with the best possible corrections. A person with visual acuity of 6/18 will only be able to see an object at 6 metres while those who have normal vision will see the same object in the same way when they are at 18 metres from the object.
To better understand low vision and blindness, knowing the definition and the effect it has on people can help give better understanding. Low vision is defined as fully corrected vision that is insufficient or interferes with the ability to perform daily life routine. Blindness is divided into 2 kinds which are legally blind and total blindness. Legally blind is defined by vision that is 20/200 or less in better eyes that cannot be corrected with standard glasses or contacts. Total blindness is defined as complete lack of form and light perception.
Vision loss that cannot be corrected is known as low vision. However, because some of the vision function still remains, low vision is not considered to be blindness. A person with low vision may have blurred vision, blind spots or have poor night vision. People with low vision can live and be independent with the help of tools and devices. Examples of tools or devices to help patient with low vision are optical device such as magnifiers or telescope, non-optical aids such as extra illumination, typoscope, books with enlarged text, writing guides, clock with large numbers and keyboard with large letters, electronic devices such as talking wristwatches and portable devices, environmental modifications such as self-threading needles and orientation with mobility training. Optometrist may prescribe all types of low vision glasses such as bioptic and full diameter telescope glasses, microscopic glasses, prism glasses and filters.
People with blindness may have to face more difficulty compared to those with low vision. Treatments available may offer help for some people but this is of course depending on the cause and progression of the vision loss. New treatments such as gene and stem cell therapies are hoped to be the future for those with blindness. For many causes of blindness, prevention is still the best option.
According to the World Health Organization (WHO), 285 million people are estimated to be visually impaired worldwide with 39 million are blind and 246 million have low vision. It is important to take care of the eyes as carefully as possible by taking preventative measures. Getting regular eye exams can help detect early eye problems before resulting in vision disturbances.