Visual Impairment: Types, Causes, Symptoms, Treatment, Diagnosis
What is Visual Impairment?
Visual Impairment can be defined as a condition in which an individual's capacity to see things are not normal. This means that the function of the eye for numerous reasons may become limited. Visual Impairment can be anything ranging from not being able to see near or far off things to partial or complete blindness. The ability of an individual to see objects clearly is termed as the visual acuity of the person and is a criterion for diagnosing an individual with Visual Impairment.
A visual field of an individual is the area that the can cover which an individual can see clearly. This is yet another criterion for an individual to be diagnosed with Visual Impairment. Some of the other conditions that fulfill the criteria for Visual Impairment are photophobia which is inability to clearly see in light, diplopia where an individual has double vision, visual distortion where images of objects feel distorted, visual perceptual difficulties where an individual finds it difficult to gauge the depth or length of an object. Blindness is a form of Visual Impairment in which the visual acuity of an individual is extremely poor along with the visual field where the individual is not able to see any object.
What are the Different Types of Visual Impairments?
- Hypermetropia or far sightedness is a type of visual impairment where an individual is not able to see objects that far away from him or her.
- Myopia or near sightedness another type of visual impairment in which an individual is not able to see clearly the objects that are near to him or her.
- Complete blindness is a condition in which an individual is not able to see anything at all from both eyes.
- Partial Blindness is a condition in which an individual is able to see to some extent from one eye
- Impairment due to other medical conditions like diabetes causing diabetic retinopathy which damages the retina to an extent that the ability of an individual to see gets significantly affected.
- Age related visual impairment such as macular degeneration in which as a result of natural wear and tear there is degeneration of the eyes resulting in a decreased ability of an individual to see.
What Causes Visual Impairment?
There are numerous causes for Visual Impairment of which some are mentioned below in which some are acquired and some are congenital. Some of the causes of Visual Impairment are:
Eye Injury: A direct blow or injury to the eye while at work or in sports or in a motor vehicle crash may result in Visual Impairment, especially injuries to the cornea which are quite common.
Inherited Conditions: There are also some cases in which Visual Impairment is an inherited condition. One such medical condition which is an inherited Visual Impairment is retinitis pigmentosa
Eye Infections: There are certain eye infections such as German Measles which if transmitted from mother to child may result in visual impairment in the child. Trachoma of the eyes caused by a contagious microorganism known as Chlamydia Trachomatis tends to also affect the eyes. This infection is mostly seen in countries with poor hygiene and sanitary conditions.
Cataract: This is yet another common cause for Visual Impairment. This is a medical condition in which there is buildup of calcium in the lens of the eyes resulting in Visual Impairment. This is more seen in the elderly population and is mostly due to natural aging and wear and tear of the eyes. In the United States, cataract is one of the leading causes of blindness in the elderly population.
Diabetic Retinopathy: This condition is only seen in diabetics in which the blood sugar becomes significantly uncontrolled that the condition affects the retina of the eye causing Visual Impairment and ultimately leading to complete blindness in some cases.
Glaucoma: This is a medical condition which is caused by increased pressure on the optic nerves and thus damaging the optic nerve resulting in Visual Impairment. This condition is seen mostly in the elderly population but is also seen in babies who are born with this condition.
Macular Degeneration: This is a medical condition which develops as one ages and there is progressive loss of vision in one eye or both and is caused due to natural degeneration of the macula.
How is the Cause of Visual Impairment Diagnosed?
The diagnosis of the cause of Visual Impairment begins with a history taking of the patient in which the physician inquires about when the symptoms started and how bad is the eye sight. In order to do this, the ophthalmologist will carry out a series of tests to identify the cause of the Visual Impairment and formulate the best treatment plan for the patient. The next step will be to conduct an examination of the eyes in which the ophthalmologist will inspect the eyelids, conjunctiva, cornea, and lens.
Depending on what the ophthalmologist observed on the examination the following tests may be carried out:
Snellen's Test: This is also known as a test for the visual acuity which is a determination on how well an individual is able to see an object. In this a Snellen chart is used which contains random alphabetical letters which are printed in a progressively shortened manner and it is placed at a distance of approximately five meters away from the patient. The patient is asked to read the letters with each eye separately first and then both eyes together. How well the patient is able to recognize the letters and speak out gives an idea of the visual acuity of the patient.
The test score for Snellen's Test is made of two numbers. The first number suggests how near the patient was when he or she was able to recognize the letters correctly and the second number is how far the patient can be from the chart in order to read out the letters on the chart correctly. If the patient scores for example 6/60 then it suggest that the patient is able to read the letters from 6 meters which an individual with normal eyesight can read correctly from 60 meters away. These scores determine how bad eyesight an individual has.
Visual Field Test: This is a test in which the visual field of the patient is tested. The visual field of an individual is defined as the range of vision that an individual has without moving or tilting his or her head. It is a test to measure the peripheral vision of the eye. In this test, a device is strapped over the patient's eyes and lights are flashed on and off in the periphery of the patient's vision. The patient is asked to press the button on the device whenever they observe lights flashing. If there is a problem with the visual field of the patient then there will be gap between pressing of buttons.
Tonometry Test: This is basically a test to evaluate for the presence of glaucoma affecting the vision of the patient. It determines the fluid pressure inside the eye and the results determines whether there is an increased fluid pressure in the eyes affecting the vision of the patient.
These tests are good enough to diagnose the cause of Visual Impairment.
How is Visual Impairment Treated?
The treatment of Visual Impairment depends on the following:
- The extent of Visual Impairment
- The exact cause of Visual Impairment
- Age and general health of the patient
Diabetic Control: It is essential for diabetics to maintain strict control of their blood sugars to avoid complications like a diabetic retinopathy which may lead to severe Visual Impairment. In cases where the diabetes has already advanced to an extent that there is development of diabetic retinopathy then there is little that can be done to improve the condition.
Cataract Surgery: If cataract is a cause for Visual Impairment of an individual then cataract surgery is the best treatment. Earlier, cataract surgery was an inpatient procedure but now with the advancement in medical science cataract surgery has become a relatively easy procedure and can be done as an outpatient without even making an incision with the help of laser technique. Postsurgery, an artificial lens is put in place of damaged lens for vision correction.
Magnification Systems: In this type of treatment for visual impairment, appropriate lens, glasses, prisms are used to magnify the images so that the patient is able to see better and there is a significant improvement's in patient's Visual Impairment.
Medications: These are basically prescribed to attempt to improve Visual Impairment caused due to condition like glaucoma. The medications used for this purpose are Latanoprost or Travoprost which are quite effective in controlling glaucoma and improving an individual's Visual Impairment. Glaucoma can also be managed with surgical procedures and laser techniques as well.
As of now there is no specific treatment for macular degeneration causing Visual Impairment.
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