Amblyopia is commonly known as'lazy eye. It is a vision development disorder, which affects eyes and the brain during infancy and childhood. It signifies that the eye does not achieve a normal visual acuity even with refractive correction in form of glasses or contact lens. During normal visual development, the eye and brain learns to'see' and develop binocularity, that is the ability to perceive depth (stereoacuity). This occurs in the first 8 to 10 years of life. 

Each eye transmits a clear and identical image from retina to the brain, which fuses the two images into a single image with 3 dimensions (adding depth). When the image is formed on the retina of two eyes is too dissimilar, the brain cannot fuse the two images and suppresses the more blurred image. As a result, the worse eye does not learn to'see' and becomes'lazy. This condition is seen in 1-4% of population.

The common causes for dissimilar images or amblyopia are:
1. Misalignment of the eyes or squint: it is the primary reason for amblyopia is misalignment of the eyes. In case, both your eyes are not aimed in the same direction, the image captured by each eye is different, resulting in diplopia. The brain will see from the dominant eye and suppress image from the other eye. Over a prolonged period of time, the eye dissociates from the visual cortex of the brain.

2. Refractive amblyopia:
A. Unequal refractive error in both eye. When the eye power of both eyes differ by more than 1.5d of spherical equivalent, which results in dissimilar images between the two eyes. As a result, the visual development in restricted in the worse eye.
B. High refractive error or astigmatism in both eyes, since there is a blurred image in both eyes, the normal vision development does not occur in either eyes resulting in bilateral lazy eyes.

3. Cloudiness in visual system or visual deprivation amblyopia: any kind of obstruction or cloudiness in the normal visual axis of the eye tissues can lead to amblyopia. Disorder of any kind, which blocks a clear image from being focused blocks the formation of a clear image on your retina. Commonly due to congenital or developmental cataracts or corneal opacities or prolonged closure of one eye in early childhood (drooping of one eyelid, eyelid swelling, patching of one eye).

Treatment for amblyopia
For treatment of amblyopia, a child must be compelled to utilize his affected, weaker eye. This can be done by correction of causative factor such as, treating refractive error with glasses, surgical correction of misalignment of eyes followed by patching and vision therapy, cataract surgery.

Patching or occlusion of the good eye
This is done to force the brain to pay attention to visual input from the worse eye. This allows nerve connections between affected eye and brain to develop due to, which the eye'learns to see. Eye drops such as atropine are also used for blurring the vision of the good eye. Some form of vision therapy may also be required to train both eyes to see together and develop some degree of depth perception.

To be effective, treatment should be implement as early as possible, within the period of normal visual development best within first 8 years of life. Some visual gain has been seen in selected patients up to age of 14 to 18 years. This also highlights the importance of a comprehensive eye examination as a routine in young children.

About Amblyopia or Lazy Eye

Astigmatism is an eye condition where there is an imperfection in the curvature of the cornea. The cornea and lens are smooth and equally curved in all directions, which helps to focus the light rays to the retina. But if there is an imperfection in the curvature, then you will suffer from a refractive error. Astigmatism is not an eye disease. It is simply a condition where the eye is not able to focus the light. 

Causes: 
Irregular shape of the cornea is the main cause for astigmatism. It might also be caused because of the imperfect shape of the lens. Suffering from astigmatism is very common. You are either born with the condition or you might have developed it after an eye surgery. It is an incorrect concept that watching too much of television or reading without enough light causes astigmatism.

Types: 
There are three different types of astigmatism:
1. Myopic astigmatism: When the principal meridians of the cornea are nearsighted.
2. Hyperopic astigmatism: When the principal meridians of the cornea are farsighted.
3. Mixed astigmatism: When one of the principal meridians is nearsighted and the other is farsighted.

It can also be classified in two other types:
1. Regular astigmatism: When the principal meridians are perpendicular to each other.
2. Irregular astigmatism: When the principal meridians are not perpendicular to each other.

Symptoms: 
Blurry or distorted vision, strain in the eye, eye discomfort, squinting and headaches are a few symptoms of astigmatism

Diagnosis:
If you notice the symptoms stated above, make sure you pay a visit to your ophthalmologist. If you are suffering from astigmatism, your doctor will do an eye test to check how much your eye is able to focus on light. After conducting his tests, he will determine how much power you have and you will have to wear glasses of that power. Apart from the option of wearing glasses or artificial lenses, you can also go for a surgery to correct the condition. LASIK is an option among the many other options of surgeries available.

Diet: 
Eat foods rich in sulphur. Foods like fish, green vegetables, pineapple, garlic, onion, olive oil, etc are rich in sulphur. Hence, eating these will help you battle astigmatism.

All About Astigmatism

Night blindness is also called nyctalopia.It's a type of vision impairment. People with night blindness experience poor vision at night or in dimly lit environments. It is not a disease in itself, but rather a symptom of an underlying problem, usually a retina problem.

What Causes Night Blindness?
A number of eye conditions can cause night blindness, including:
1. Nearsightedness or blurred vision when looking at faraway objects.
2. Cataracts or clouding of the eye's lens.
3. Retinitis pigmentosa, which occurs when dark pigment collects in your retina and creates tunnel vision.
4. Vitamin A Deficiency
5. Zinc Deficiency
6. Dry Eyes
7. Diabetes

Are the Symptoms of Night Blindness?
The sole symptom of night blindness is difficulty seeing in the dark. You're more likely to experience night blindness when your eyes transition from a bright environment to an area of low light, such as when you leave a sunny sidewalk to enter a dimly lit restaurant. You're likely to experience poor vision when driving due to the intermittent brightness of headlights and streetlights on the road.

How can I Prevent Night Blindness?
You can't prevent night blindness that's the result of birth defects or genetic conditions, such as Usher syndrome. You can, however, properly monitor your blood sugar level and eat a balanced diet to make night blindness less likely. 

Orange colored foods are excellent sources of vitamin A, including:
1. Cantaloupes
2. Sweet potatoes
3. Carrots
4. Pumpkins
5. Butternut squash
6. Mangoes

What are the Treatment Options for Night Blindness?
The treatment will depend on its causes.
1. Nutrient deficiency (Vitamin A and Zinc) is the easiest to treat. 
2. If the cause is cataract, you can go for cataract surgery to remove the clouded lens and replace it with artificial intraocular lens. Vision is usually dramatically improved after surgery. 
3. For dry eye syndrome, lubricate your eyes with artificial tear drops as they provide instant relief. Just make sure that they are without preservatives. 
4. Diabetic retinopathy can be prevented with tight control over blood sugar, active lifestyle and good dietary habits.
5. As for retinitis pigmentosa, unfortunately there are no treatments available. Thankfully, new research is showing that vitamin A might have a slowing effect on the progression of this eye disease.

Night Blindness: Causes and Symptoms

Glaucoma is a group of diseases that causes damage to your eye's optic nerve and gets worse over time. The optic nerve is a bundle of millions of nerve fibres which carry visual impulse from the retina at the back of eye to the brain. The increased eye pressure, called intraocular pressure, can damage the optic nerve and fasten the natural nerve fibre loss. Since nerve cells can't regenerate this damage is permanent and irreversible.

Without treatment, glaucoma can cause total permanent blindness within a few years. Because most people with glaucoma have no early symptoms or pain from this increased pressure, it is important to see your eye doctor regularly so that glaucoma can be diagnosed early and treated before significant functional visual loss occurs.

If you are over age 40 and have a family history of glaucoma, you should have a complete eye exam with an eye doctor every one to two years. If you have any risk factors, you may need to visit your eye doctor more frequently.

What are the symptoms of glaucoma?

For most people, there are usually few or no symptoms of glaucoma. The first sign of glaucoma is often the loss of peripheral or side vision, which can go unnoticed until late in the disease. This is why glaucoma is often called the" sneak thief of vision" or" silent thief of eye sight.

If you have any of the following symptoms, seek immediate medical care:

Seeing halos around lights
Vision loss
Redness in the eye
Eye that looks hazy (particularly in infants)
Nausea or vomiting
Pain in the eye
Narrowing of vision (tunnel vision)
Risk factors-

There are several risk factors, which may lead to glaucoma, such as

Age of the individual
Ethnicity- african, caribbean, hispanics and asians are at higher risk
Increased eye pressure or iop history of glaucoma in family or relatives
Presence of myopia or hyperopia
Previous eye injuries
Use of steroids- as injections, tablets, eye or ear drops or ointments or protein supplements for muscle building in gyms or inhalers
Previous history of anemia
Individuals conditions affecting blood flow like hypertension, diabetes or high blood sugar, migraine etc are also at risk.
Treatment-

The treatment for glaucoma relies on the nature and seriousness of every case. Generally, glaucoma cannot be totally cured, but it can be controlled. Eye drops, pills, laser strategies, and means of surgery are utilized to maintain and prevent further harm from happening. Talk to your eye doctor to find out if you are at risk of developing glaucoma.

Are You at a Risk of Glaucoma? What You Need to Know?

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?

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?

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