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!

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 most common vision problems are shortsightedness and farsightedness. Shortsightedness is when a person sees close objects clearly while distant objects appear blurry. It is more common than farsightedness and affects about 70% of the Asian population.

When there is a refractive issue, the prescription usually has a plus/minus with it and also a number. A  minus  symbol is used to represent shortsightedness; the greater the number of the glasses, the higher the shortsightedness. High myopia is a more severe form of shortsightedness where the power is -6.0 or higher.

Symptoms: 

As mentioned, the person will be able to see nearby objects but will have difficulty seeing far off objects.

Difficulty reading signs and boards
Squinting
Straining to reduce the strain on the eye
Tired and fatigue due to this eye strain, especially when in constant move like playing sports or travelling
How it happens?

Vision can be explained by a physical process where light passes through a lens and falls on the retina in the posterior portion of the eye where it forms an image. This is then sent to the brain where it is read and interpreted as a particular object. When the lens becomes elongated, the image that is formed is distorted in that it is formed in front of the retina and not on the retina. Though it gradually settles down with adulthood, in most cases, it progresses and requires corrective lenses. The corrective lenses ensure the image falls on the retina and visual perception is improved.

Treatment:

Corrective glasses are the most commonly used measure for nearsightedness. The lenses could be used either as spectacles or as contact lenses.
Laser surgery can also be used to correct the problem. A thin layer of the cornea is removed and the image formation is corrected.
Artificial intraocular lenses are also being used to treat this condition. They work like contact lenses and may need periodic replacement.
The most common technique, especially for high myopia is the use of surgery to correct the problem. This is a one-time correction and is a more durable solution than the earlier mentioned options.
Appropriate calculations are done to identify the lens to be used so that proper vision is restored.
Complications: 

Though not common, retinal detachment and variable postoperative refractive error can occur during the surgery.
It is very important to set realistic expectations with the patient in terms of what to expect before, during, and after surgery. If only one eye is going for repair, the chances of mismatch in vision could be present in the early stages. Being clear about what to expect will help in successful correction.

Myopia or Nearsightedness - How It Can Be Treated?

While spectacles are a fashion statement for some people, for others they are an uncomfortable necessity. Though contact lenses may be a little more aesthetically pleasing they too can be quite uncomfortable and cannot be worn throughout the day. Thankfully, there is a third way to correct vision. Laser surgery or LASIK, it is a popular refractive procedure that can correct common vision problems, such as nearsightedness, farsightedness and astigmatism. This procedure aims at reshaping the cornea so that light entering the eyes can be focused onto the retina for the person to have a clearer vision. 

Laser surgery is pain-free and quick in most cases. Usually, it does not take more than 15 minutes to correct vision in both eyes. The results of this surgery can be seen in as little as 24 hours. 

The first step of laser surgery to correct vision is to create a thin, circular flap in the cornea. This is then folded back to access the stroma or underlying cornea. An excimer laser is then used to remove some of the corneal tissue. For people suffering from nearsightedness, the cornea is flattened while for people suffering from farsightedness, the cornea is made steeper. In cases of astigmatism, an irregular cornea is smoothened. Once the correct gradient has been achieved the corneal flap is put back into place and the cornea is allowed to heal naturally. There are no stitches or bandages required in a laser eye surgery. You may feel a temporary burning or itching sensation in your eyes immediately after the procedure. It is important not to rub your eyes or place any pressure on them. Your vision may also be cloudy or blurred for the first few hours. A doctor will usually advise you to rest for a few days after the surgery so that your cornea can heal properly. In a few days, your eyesight should stabilize, though, in a few rare cases, it may take a little longer. You should also avoid any form of strenuous exercising for a few days after the surgery. 

Though LASIK surgery has a very high success rate, there are very rare occasions where spectacles may still be needed even after the surgery. Thus LASIK is a choice of treatment for many who seek freedom from glasses.

LASIK - Say No to Boring Glasses! 

Cataract can be defined as the clouding of the natural lenses in the eyes. This is caused by the clumping of protein in the eye lens. Cataract is a common eye disorder and the leading cause of loss of vision in people who are past their fortieth birthday. Cataract can occur in one or both eyes. When diagnosed properly, cataract can be treated with surgery to prevent blindness.

Depending on where and how they develop, there are many types of cataract. The most common amongst these are:

1.        Subcapsular cataract

These occur at the back of the eye lens. Diabetic patients are very susceptible to this kind of cataract.

2.        Nuclear cataract

Yellowish-brown cataract that form in the center of the lens are called nuclear cataract. This is usually seen in cataract caused by ageing.

3.        Cortical cataract

Cataract in the lens cortex are known as cortical cataract. These are wedge shaped and whitish in color. Spokes protruding out of these opaque wedges can be seen moving towards the center of the eye.

4.        Congenital cataract

Though they are not common, babies can also have cataract. Cataract formed at birth or within the first year of a baby's birth are known as congenital cataract.

5.        Secondary cataract

Cataract is one of the known side effects of diabetes and glaucoma. Some steroids and medicines are also linked to cataract.

6.        Traumatic cataract

If your vision becomes cloudy years after an eye injury, it could be a traumatic cataract. It can take several years for this to happen.

7.        Radiation cataract

Exposure to radiation can also lead to cataract. This is seen sometimes in patients who have undergone radiation therapy to fight diseases like cancer.

Though the type of cataract might differ from person to person, the symptoms are usually the same. Some of the common symptoms of cataract are:

1. Blurred vision
2. Reduced night vision
3. Increased sensitivity to light and glare
4. Seeing halos around lights
5. Colors appearing faded
6. Double vision

A reading test is the first step towards diagnosing cataracts. This is followed by tests to measure the eye pressure. Your doctor will also need to dilate the pupil to check the condition of the optic nerves and retina.

Surgery is the safest way to remove a cataract. Surgery is usually recommended when cataract begin inhibiting your daily life such as preventing you from driving, interfering with reading etc.
 
In most cases, this can be done as an outpatient procedure. The earlier it is diagnosed, the easier it is to treat. Hence, if you notice any of the symptoms mentioned above, get your eyes checked at once. The surgery is a day-care surgery only, so a person can go home the same day.

Is Your Vision Clouded? It Could Be Cataracts

Blurred vision is most often a sign that you need corrective spectacles for near sightedness, far sightedness or astigmatism but it could also be a sign of a bigger problem including eye diseases or neurological problems. Blurred vision involves the loss of sharpness of vision and objects appearing hazy and out of focus. It can affect one eye or both eyes simultaneously.

Whatever be your age, it is a good idea to consult a doctor as you begin to experience a blurred vision. To measure the extent of your vision problem, a doctor will do a comprehensive eye examination including spatial contrast sensitivity and a standard eye chart test. Some of the factors that trigger blurred vision are:

1. Myopia or nearsightedness
2. Hypermetropia or farsightedness
3. Astigmatism caused by an irregularly shaped cornea
4. Presbyopia - the diminished ability to focus on objects due to the hardening of the lens in the eye
5. Dry eyes or the lack of lubrication on the surface of the eyes
6. Hormonal changes during pregnancy
7. Migraine headaches
8. Temporary floaters in the eye formed by the liquefying of the gel in the eyes
9. After effects of lasik surgery
10. Eye drops or medication
11. Overuse of contact lenses
12. Diabetes

Blurred vision can also be a symptom of a serious condition such as cataract, glaucoma, macular degeneration, diabetic retinopathy and cardiovascular diseases.

Treatment for blurred vision depends on the factors triggering it. Wearing corrective glasses can cure blurred vision caused by myopia, hypermetropia and astigmatism. These conditions can also be treated by lasik surgery. For blurred vision related to diabetes, check your blood sugar and get it into its optimal range.

Exercises for the eye muscles can also help sharpen vision and lower the rate of eye muscle degeneration. Some of these exercises are:

1. Alternately focus on an object close to you and another far from you for ten seconds each.
2. Blink your eyes and hold for two seconds
3. Roll your eyes clockwise and anticlockwise. Repeat 15-20 times.
4. Rub your palms together to generate heat and place over your eyes to relax them.

A healthy diet with plenty of vitamin a can help keep your eyes healthy and prevent blurring of vision. Wearing sunglasses can also protect your eyes from harmful uv radiation and lower their rate of wear and tear. Lastly avoid reading in moving vehicles and holding a book too close to your face.

Is Your Vision Blurry? What Should You Do?

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