People may suffer from visual impairment even though their eyes are perfectly normal. Such loss of vision may result from neurological impairment.

Vision is the combination of image formation and perception of various attributes of the image by the brain. When the brain is not able to perceive images or various attributes of images, the patient may suffer from neurological impairment of vision. Such impairment owes its origin to the nervous system.

Causes of Visual Impairment:

There are various areas in the brain that process some or the other attribute of the image that has formed on the retina. Occipital cortex, the area situated at the rear side of the brain is a very important site. It is responsible for processing visual stimuli and allowing people to make an idea about shape, distance, movement, color, etc. The severity of loss of vision depends on the extent and location of damage in the brain.

Neurological loss of vision may result from acquired brain injury, difficulties with visual perception, impairment in coordination of the eyes, etc. All these may stem from damage areas in the brain that are responsible for vision. There are many areas in the brain that are responsible for vision.

These areas can get damaged from various accidents like:

Stroke: If a person suffers a stroke, a part of his or her brain is likely to get damaged due to a haemorrhage or a blocked blood vessel.

Traumatic Brain Injury: A traumatic brain injury such as in a car accident or a violent fall can damage visual perception of the brain.

Infections: Infections such as meningitis attack the brain and may impair various areas of it.

Lack of Oxygen: People may suffer from lack of oxygen if they experience accidents like a near-drowning episode or a heart attack or something else, which has the effect of interrupting blood flow to the brain.

Diseases: Diseases such as brain tumors, multiple sclerosis etc. can precipitate neurological vision loss.

Symptoms of Visual Impairment:

Symptoms of neurological vision loss depend on the type of vision impairment and the location of damage in the brain. It may include:

Blurry vision: In Blurry vision, a person will not see things clearly or may see something in light but find it difficult to see them in dim light.

Double vision: In double vision, the patient sees a single object as two and cannot merge them as one.

Problems with depth perception of objects

Problem with bright light: In this type of problem, a person experiences difficulty seeing an object in a bright light. One may also feel pain or discomfort in the eye in bright light.

Difficulty with interpreting the object the person is looking at

Partial loss in the visual field: In this problem, half of the visual field in each eye is missing.

Treatment of Visual Impairment:

There is hardly any treatment for such vision loss since the rectification of visual acuity is of no help. Depending on the location and degree of neurological impairment, vision may improve over time. Some children with acquired brain injury or impairment in the coordination of the eyes and difficulties with visual perception also tend to improve with age.

Conclusion:

This is a type of vision loss where glasses, contact lenses, surgeries, or eye drops are not going to help. Such vision loss is usually permanent. Children with similar symptoms need to be presented with pictures, bright light, etc., which may help to form an idea about the object.

Visual Impairment Related To Nervous System!

Cataract is clouding of clear natural lens present inside the eye, this is a major cause of decreased vision in elderly. Cataracts can occur in one or both eyes, usually developing very slowly. Things look blurry, hazy, less colourful and less sharp with cataract. 

Most cataracts are related to ageing, however many other factors can either increase the rate of formation or cause cataract formation. 

Causes of Cataract Formation-

Ageing: Most common cause. As the proteins present in the lens of the eye degenerates over the years ( just like any other organ) cataract is formed. If you are having Diabetes or hypertension, the rate of formation gets accelerated.

Radiation: Prolonged exposure to ultraviolet rays, especially UV-B rays, results in cataract in your eyes. Wearing sunglasses in the daytime helps in slowing down the process of cataract.

Genes: Many genetic disorders can result in congenital cataract ( cataracts present since birth) or early formation. Like in Lowe syndrome or Down's syndrome. 

Lifestyle Choices: Cigarette smoking, long hours of sun exposure regularly, antioxidant, poor diet etc. are responsible for the onset of cataract.

How To Detect Cataract?

Certain signs and symptoms suggest the existence of cataract in the eye. Depending on the type and level of cataract, problems in vision occurs. The main symptom is foggy cloudy vision as if seeing through a dirty glass window. 

Other Symptoms are- 

inability to see clearly in bright light (during the day) which becomes better in dim light ( evening and night) and vice versa. 
watery, tired eyes - mild pain in and around eyes. 
yellow tinge in vision 
Halos around light bulbs or bright light. 
If you are experiencing above symptoms and having problems in viewing things clearly, visit an ophthalmologist and get your eyes checked.

Foggy and Cloudy Vision - A Sign Of Cataract?

People are well aware of the harmful effects that UV rays have on the skin, but very few know that UV rays can damage their eyes as well. The tissue that human eye is made up of is one of the most sensitive tissues in the body and hence, the most vulnerable. The increasing level of UV radiation reaching the Earth s surface every minute has made it indispensable to take the required precautionary measures to protect the eyes.

What are UV rays?

Sunlight consists of 3 types of radiations - Infrared, Visible light and UltraViolet. Artificial sources like lasers, tanning beds and welding machines also emit UV radiation.

There are three types of UV radiations - UV-A, UV-B and UV-C. 

UV-C is absorbed by the ozone layer and does not possess any risk. It is UV-A and UV-B radiations that adversely affect the eyes and vision.

Impact of UV rays on  eyes

Too much exposure to UV rays can affect vision, harm the eyes, and deteriorate overall eye health. There are various eye problems that are aggravated by excessive exposure to UV radiation:

Macular Degeneration: It is caused by damage to the retina over time by UV rays. It leads to age-related blindness. Too much exposure to UV rays increases the risk of developing macular degeneration.
Cataract: It is the clouding of eye s natural lens - the part of the eye that focuses the light we see. Too much exposure to UV rays increases the risk of developing cataracts. 
Pterygium: Often known as  surfer s eye , pterygium is a pink, non-cancerous growth that is formed on the conjunctiva. UV rays are believed to be responsible for the development of this growth.
Skin Cancer of the Eyelids: Too much exposure to UV rays can cause skin cancer in and around the eyelids.
Photokeratitis: Popularly known as corneal sunburn or  snow blindness , photokeratitis is caused due to excessive short-term exposure to UV-B rays. Photokeratitis occurs when you spend long hours at the beach or skiing. It sometimes leads to temporary vision loss. 
How to protect the eyes from harmful UV rays?

Here are some tips to help ensure that eyes are protected against harmful UV rays:

Always use quality sunglasses that block out 99-100 percent of both UV-A and UV-B radiation when outdoors.
Stay away from tanning beds, and if you use them occasionally, always wear eye protection. 
Wrap around frames should be used if you spend a lot of time outdoors.
Be sure to see your doctor at least every two years.

UV Rays - Are They Damaging Your Eyes?

A common headache can have a number of reasons behind it, such as defective vision, hetrophoria or convergence deficiency, etc. Now, the question arises as to how they can cause headache. Read on to know more...

Q. Why should defective vision cause headache?

To attain a perfect vision, eyes with defective vision have to make sustained extra efforts, which results in headache. Even if the refractive error is very small, it can be the cause of headache. More prolonged the working and smaller the print, higher the incidence of headache.

Q. Can this occur at all ages?

Yes, it can occur at all ages. However, with age, the resistance decreases and hence elderly people are more prone to get headache. More the use of computer, mobiles, TV or prolonged studies precipitates headache

Q What is Hetrophoria?

Normally, both eyes always remain parallel, but in some cases, eyes have slight tendency to develop minor squint, may be convergent or divergent. This is called Hetrophoria or Latent squint. Such patients have to take extra strain to keep the eyes straight

Q. What is convergence deficiency?

For reading, both eyes have to converge and if there is weakness of convergence, extra strain has to be put on the eyes, which cause headache.

Q. What is the ideal method of refraction in young patients, I,e below 40 years?

Ideal method is to dilate the pupil with Tropicasyl plus drops. This has the advantage that the doctor can see the retina and Optic Disc. This is important to exclude any involvement of brain as the cause of headache. It also relaxes accommodation and hence provides correct refraction. In cases of Hypermetropia, it is extremely essential to dilate the pupil.

Q. What is the role of Autorefractmeter (a computer) in refraction?

It is a very important instrument to provide correct refraction, but it cannot be totally relied upon. Some opticians rely on it and give wrong numbers.

Q. What is acceptance Test?

You have refracted the eyes with Autorefractmeter or Streak Retinoscope but exact power is what a patient accepts. This is very important.

Q. What is astigmatism?

There is a difference in refraction in different meridians and it is important that a cylinder number is prescribed in correct axis. This is a difficult task and needs lot of experience.

Q. Is it important to correct astigmatism?

To relieve headache and strain on the eyes, it is very important that exact cylinder is prescribed.

Q. What is the role of exact centring of Optical Lenses?

You may give correct number, but if the centre of the Optical lenses and cornea do not coincide, satisfactory results are not obtained. To dispense correct lenses is a big art and the Optician must be qualified and well experienced.

Q. Does the quality of lens affect the visual comfort?

Yes, it is important that quality of lenses should be good, preferable fibre lenses which are Ant reflect coated. Crizal coating with capability to block the UV rays are very popular.

Conclusion: Refractive errors are important cause of headache and needs proper examination of the eyes, preferably after dilating the pupil. Astigmatic error even if too small may be the cause of headache. Spectacle dispensing is an art and a patient must select proper optician. Spectacles if advised for constant use must be used constantly to get full relief.

Defective Vision - Can it be a Cause of Your Headache?

The ability to see is one of our greatest powers and it needs to be valued and looked after. Sometimes this involves wearing glasses to improve our vision. Spectacles not only help us see better but also prevent straining and further deterioration of the eye muscles. Here are a few signs to watch out for that will indicate your need for spectacles. Keep in mind however that a comprehensive eye exam is the only way to determine the power required for your spectacles. 

-  Blurred vision
Blurred vision or the inability to focus on something in the distance is one of the first signs or eye deterioration. When it comes to children, watch out for complaints of inability to read the writing on class blackboards.

-  Frequent headaches
Unexplained headaches that come and go could be a sign that you need glasses. These headaches can usually be felt at the end of a long day or after watching television. 

-  Constant squinting
Squinting is a natural way to improve vision. This is because the act of squinting reduces extra light and light scattering thus allowing us to see something clearer. Thus, if you notice yourself squinting more than usual it is time to schedule an eye exam.

-  Difficulty working on a computer
Struggling to read figures and words on a computer screen is usually a sign of poor vision. Try adjusting your screen angle and the distance of the screen from your eyes to see if your vision improves or worsens. 


-  Difficulty adjusting to lights
Sudden increased sensitivity to lights can be a sign of many eye disorders with vision problems being the most common. 


-  Eye strain
Occasional pain in the eyes after a long day or as a result of an allergic reaction is nothing to worry about. However, if this pain persists for a few days, it could be an indication that you need spectacles. 
Deterioration of vision is usually a very gradual process and so you may not realize when it begins. However, the earlier you start wearing corrective glasses to improve your vision the easier it will be to control the deterioration of the eye muscles and you may even be able to rectify your condition completely. So, do not ignore any of these warning signs. Even if you do not have any of these symptoms, it is a good idea to get a thorough eye examination at least once a year.

Common Signs You Need Glasses

Glaucoma is a leading cause of blindness in people across the globe. It damages the optic nerve that carries sensory images from the retina to the brain. A faulty eye pressure is responsible for damaging the very delicate optic nerve fiber causing small blind spots in the retina. Unfortunately, for most patients this disease only gets diagnosed when the number of blind spots is on the higher side.

Types of Glaucoma

Open angle: This is a type of Glaucoma which results from the blockage of the drainage angle of the eye resulting into an increased eye pressure.
Angle closure: This is the kind of Glaucoma which results from the narrowing down of the drainage angle leading to complete blockage.
Target segment of Glaucoma

Family history: Inheritance surely plays a role in case of Glaucoma too. If Glaucoma runs through families of an individual, there are higher chances of getting this disease. Although there is no hard and fast rule about it, the risks of inheriting this disease are on the higher side.
Eye injury: If there is any history of previous eye injuries, the probability of the onset of Glaucoma cannot be turned down. Specially, if the injury is related to optic nerve, there are very high risks involved.
Bilateral Oophorectomy: Dual Ovary removal before the age of 40 results in deficiency of estrogen resulting in Glaucoma. Although most surgeons warn their patients of the possible risk of these procedures, many surgeries such as these have resulted in patients losing eyesight in the form of Glaucoma.
Patient with Diabetes: In case of acute diabetes, retina gets damaged and the eye starts producing new blood vessels on the iris resulting into an increased eye pressure. This condition often leads to Glaucoma due to blockage of fluid flow in the eye.
Eye Conditions: Myopia, multiple surgeries to the eye, blunt trauma etc. can lead to Glaucoma. A patient who has undergone any kind of eye surgeries suffers from inflammation. However, major inflammation is often found twisting blood flow in the eye resulting into Glaucoma.
If a patient is 40 or above: After a person reaches 40 years of age, a lot of diseases start cropping in to the body. Studies show that Glaucoma has a higher frequency in people who is more than the age of 40 or above.
High eye pressure: A patient with an eye pressure of above 21 mm HG is also at a very high risk of getting glaucoma. For a normal person the IOP lies between 10 to 21 mm HG.
Blood flow related disease: Diseases such as acute migraine, hypertension and low blood pressure which involves blood flow related problem often aggravate to glaucoma.
Ethnic Background: Statistics show that people from Afro American, Hispanics, Asian and Caribbean background have greater chances of being affected by Glaucoma.

Glaucoma - Are You at Risk?

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