EYES Diseases

EYE DISEASES
Allergy

The most common causes of eye allergies are seasonal allergies to pollen and mold spores. People with seasonal hay fever (allergic rhinitis) normally notice their symptoms worsen when they go outdoors on days with high pollen counts.

Indoor allergens, such as dust mites and pet dander, can also cause eye allergies year-round. If you suffer from this type of allergy, you may notice your symptoms worsen during certain activities such as cleaning your house or grooming a pet.

Symptoms and Diagnosis
If your symptoms are related to an eye allergy, chances are you will have problems in both eyes. Typical symptoms include:
• Watery eyes
• Itchiness
• Sensitivity to light
• Redness
• Grittiness
• Eyelid swelling

These symptoms can occur alone or along with allergic rhinitis nasal symptoms. They typically appear shortly after exposure to the allergen.

An allergist / immunologist, often referred to as an allergist, has specialized training and experience to determine which allergens are causing your symptoms and discuss which treatment options are right for you. An allergist / immunologist can also offer valuable advice for avoiding your triggers.

Your allergist will take a detailed health history, perform a physical exam and then most likely test you for allergies. Skin prick tests may show the results within 20 minutes, though delayed reactions may take longer to appear. Blood tests and conjunctival challenge tests may also be considered.

An allergist performing a conjuctival challenge test will apply either dry materials or liquid materials, containing allergen concentrations, to one eye and apply a placebo to the other eye to serve as a control.

EYE DISEASES
Amblyopia

Amblyopia, commonly known as lazy eye, causes more visual loss in the under 40 age group than all the injuries and diseases combined in this age group.
Amblyopia, commonly known as lazy eye, is the eye condition noted by reduced vision not correctable by glasses or contact lenses and is not due to any eye disease. The brain, for some reason, does not fully acknowledge the images seen by the amblyopic eye. This almost always affects only one eye but may manifest with reduction of vision in both eyes. It is estimated that three percent of children under six have some form of amblyopia.

Summary:
Lazy Eye is an eye condition in which there is blurry or reduced vision that is not correctable by glasses, contact lenses or eye surgery
Lazy eye can cause loss of vision, including loss of depth perception and two-eyed 3D vision.
Lazy eye treatment can yield improvements at any age, but early detection and treatment still offer easier treatment and the best chances for a cure.
Scientific research has proven that lazy eye treatment can be successful in older children, teenagers, and adults. Neuroscience has established that the human brain can change at any age (neuroplasticity).
Comprehensive vision examinations are needed for infants, toddlers, and pre-school children. A pediatrician's eye exam or a 20/20 eye chart screening is not adequate for the detection of amblyopia and other visual conditions which are related to or mistakenly called lazy eye.

EYE DISEASES
Cataract

Cataracts is the clouding of the lens that leads to blurriness. Cataract can be caused by age, trauma, diabetes, toxic substances, certain medicines or by birth.
Symptoms:
Blurry vision, sensitivity to light, double vision, trouble in distinguishing colors such as blue or purple, frequent changes to glasses or contacts prescriptions.
Treatment:
At Laser Vision Centre, treatment is performed via phacoemulsification (phaco) where the doctor makes a tiny incision in the eye and breaks up the lens using ultrasound waves. The lens is removed, and an intraocular lens (IOL) is put in its place. The pricing is based on the type of lens implanted and we provide Eyecryl (Indian Lens), Iriflex (German lens), Rayner (British lens) and Alcon (American lens).
Signs and symptoms vary depending on the type of cataract, though considerable overlap occurs. People with nuclear sclerotic or brunescent cataracts often notice a reduction of vision. Nuclear cataracts typically cause greater impairment of distance vision than of near vision. Those with posterior subcapsular cataracts usually complain of glare as their major symptom.[13]

The severity of cataract formation, assuming no other eye disease is present, is judged primarily by a visual acuity test. Other symptoms include frequent changes of glasses and colored halos due to hydration of lens.

EYE DISEASES
Corneal Disease

The images we see are made up of light reflected from the objects we look at. This light enters the eye through the cornea, which acts like a window at the front of the eye. The amount of light entering the eye is controlled by the pupil, which is surrounded by the iris – the coloured part of the eye.

Because the front part of the eye is curved, it bends the light, creating an upside down image on the retina. The brain eventually turns the image the right way up.

The retina is a complex part of the eye, and its job is to turn light into signals about images that the brain can understand. Only the very back of it is light sensitive: this part of the retina is roughly the area of a 10p coin, and is packed with photosensitive cells called rods and cones.

Cones are the cells responsible for daylight vision. There are three kinds, each responding to a different wavelength of light: red, green and blue. The cones enable us to see images in colour and detail. Rods are responsible for night vision. They are sensitive to light but not to colour. In darkness, the cones do not function at all.
The lens is a clear disc-like structure that helps to focus light on the retina. It can do this because it is adjustable, and uses a muscle called the ciliary muscle to change shape and help us focus on objects at different distances. The automatic focusing of the lens is a reflex response and is not controlled by the brain.

Once the image is clearly focused on the sensitive part of the retina, energy in the light that makes up that image creates an electrical signal. Nerve impulses can then carry information about that image to the brain through the optic nerve.

Other parts of the eye include the aqueous humour, a liquid which sits in a chamber behind the cornea, and the vitreous humour, the clear gel that fills the space between the lens and the retina. The sclera is the white part of the eye, forming an outer layer that protects everything inside, while the choroid is the layer of the eye that lies between the retina and the sclera. It is made up of layers of blood vessels that nourish the back of the eye.

EYE DISEASES
Glaucoma

The condition can be difficult to diagnose because symptoms don’t appear straight away – instead, they develop slowly over many years. This means many patients only seek treatment when they notice they’re losing their sight, when significant damage has already occurred.

Glaucoma is a group of conditions caused by normal fluid in the eye that hasn’t drained properly. This creates pressure that damages the optic nerve connecting the eye to the brain, resulting in sight loss. Although it’s not clear exactly why this happens, factors such as age, family history, racial background and other medical conditions such as diabetes and short-sightedness can increase the risk. It can affect people of all ages, but it’s most common in adults.

There are different types of glaucoma, and treatment will depend on the type a patient has. Glaucoma can’t be cured, and vision that has already been lost cannot be restored. But further sight loss can be prevented via medication or surgery. Each glaucoma patient requires lifelong management for best results.
Yet the challenge is that patients often don’t seek treatment for glaucoma until it is too late to save their sight. This is why we are working with partners in Africa to introduce pilot programmes to prevent and treat glaucoma.
Our aim is to make sure glaucoma is diagnosed and treated as part of local eye health services, to ensure patients’ sight can be saved.

EYE DISEASES
LASIK

LASIK eye surgery is the best known and most commonly performed laser refractive surgery to correct vision problems. Laser-assisted in situ keratomileusis (LASIK) can be an alternative to glasses or contact lenses.

During LASIK surgery, a special type of cutting laser is used to precisely change the shape of the dome-shaped clear tissue at the front of your eye (cornea) to improve vision.

In eyes with normal vision, the cornea bends (refracts) light precisely onto the retina at the back of the eye. But with nearsightedness (myopia), farsightedness (hyperopia) or astigmatism, the light is bent incorrectly, resulting in blurred vision.

Glasses or contact lenses can correct vision, but reshaping the cornea itself also will provide the necessary refraction.
Nearsightedness (myopia). When your eyeball is slightly longer than normal or when the cornea curves too sharply, light rays focus in front of the retina and blur distant vision. You can see objects that are close fairly clearly, but not those that are far away.
Farsightedness (hyperopia). When you have a shorter than average eyeball or a cornea that is too flat, light focuses behind the retina instead of on it. This makes near vision, and sometimes distant vision, blurry.
Astigmatism. When the cornea curves or flattens unevenly, the result is astigmatism, which disrupts focus of near and distant vision.

EYE DISEASES
Low Vision

It is normal to be a carrier for a handful of genetic disease without it impacting your daily life. In fact, most individuals are carriers for genetic disease despite no history of disease within their family. What is important to know, is if you are your partner or future spouse are carriers for the same genetic disease. When two people are carriers of the same disease, they can unknowingly have a child that is affected by a genetic condition. Learning about which genetic disease you are a carrier for before pregnancy allows you to take steps to plan for your future family.

Genetic diseases differ in the way that they can be inherited. Carrier screening is performed for genetic diseases that are inherited in an Autosomal Recessive or X-linked manner. Your chance of passing on a condition to your child depends on your carrier status, the carrier status of your partner as well as the mode of inheritance for each specific disease.

Autosomal Recessive:

The majority of the conditions included in Carrier Screening are inherited in an autosomal recessive pattern. This means that the disease is equally found in males and females and that it must be inherited from both parents in order for future generations to be affected. An individual that is a carrier of an autosomal recessive disease inherited one disease-causing copy of the gene and one health copy of the gene from their parents. If two individuals are carriers for the same autosomal recessive disease, they have a 25% chance of both passing on a disease-causing copy of the gene to their child.
X-linked conditions are inherited exclusively from mother to child and are more often seen in males than in females. X-linked disease are caused by mutations found on the X chromosome. Because males (XY) only have one X chromosome, if they inherit a disease-causing copy of the X chromosome from their mothers, they are more greatly affected than females (XX). This is because males (XY) receive no compensation of the affected traits from another X chromosome. In order for a male to be affected by an X-linked condition, they must receive only one disease-causing copy. If the female partner is a carrier of an X-linked genetic disease, the couple's chance of having an affected male child is 50%.

EYE DISEASES
Neuro Ophthalmology diseases

Neuro-ophthalmology are vision problems that relate to the nervous system. Vision disturbances can be caused by disorders of the optic nerve, central nervous system (brain and spine), eyeball movement and pupil abnormalities.

The optic nerve connects the eye to the brain and acts like an electrical cable bringing visual information from the eye to the brain for processing. Optic nerve disorders include:

Compression
Eye movement disorders:
Diseases of the orbit cause restricted movement
Diseases affecting the nerves to the muscles cause weakness
Diseases can affect the transmission (sending) of signals between the nerve and muscle
Diseases can affect the muscle
Diseases can affect the parts of the brain that control movement
Not enough blood supply (ischaemia)
Inflammation (swelling)
Trauma (injury)
Raised pressure in the brain
Raised pressure in the eye (glaucoma)

Causes:
The causes of neuro-ophthalmology disorders depend on the type:

Compression may be caused by a tumour
Reduced blood supply may be caused by hypertension, diabetes, hyperlipidaemia or smoking
Inflammation (swelling) is often related to diseases that can affect other parts of the body, like connective tissue disease and multiple sclerosis

EYE DISEASES
Orbital Diseases

The orbital cavity (eye socket) is the bony cavity that encloses the bulb and accessory organs of the eye, including the ocular muscles, lacrimal glands, nerves, vessels, and retrobulbar adipose tissue. Diseases of the orbital cavity include Graves ophthalmopathy, orbital cellulitis, rhabdomyosarcoma, and lacrimal sac disorders. Typical symptoms associated with these diseases include exophthalmos and diplopia. Treatment differs according to the underlying disease and includes conservative measures (antibiotics), surgery, radiotherapy, and chemotherapy.Disorders of the lacrimal system are discussed in a separate learning card.

EYE DISEASES
Refractive Errors

Overuse of the eyes does not cause or worsen refractive error. The causes of the main types of refractive error are described below:

Myopia (close objects are clear, and distant objects are blurry)
Also known as nearsightedness, myopia is usually inherited and often discovered in childhood. Myopia often progresses throughout the teenage years when the body is growing rapidly. Watch a video explaining myopia.
Hyperopia (close objects are more blurry than distant objects)
Also known as farsightedness, hyperopia can also be inherited. Children often have hyperopia, which may lessen in adulthood. In mild hyperopia, distance vision is clear while near vision is blurry. In more advanced hyperopia, vision can be blurred at all distances. Watch a video explaining hyperopia.
Presbyopia (aging of the lens in the eye).
After age 40, the lens of the eye becomes more rigid and does not flex as easily. As a result, the eye loses its focusing ability and it becomes more difficult to read at close range. This normal aging process of the lens can also be combined with myopia, hyperopia or astigmatism. Watch a video explaining presbyopia.
Astigmatism Astigmatism usually occurs when the front surface of the eye, the cornea, has an asymmetric curvature. Normally the cornea is smooth and equally curved in all directions, and light entering the cornea is focused equally on all planes, or in all directions. In astigmatism, the front surface of the cornea is curved more in one direction than in another. This abnormality may result in vision that is much like looking into a distorted, wavy mirror. Usually, astigmatism causes blurred vision at all distances.

EYE DISEASES
Retinal Diseases

Retinal diseases vary widely, but most of them cause visual symptoms. Retinal diseases can affect any part of your retina, a thin layer of tissue on the inside back wall of your eye.

The retina contains millions of light-sensitive cells (rods and cones) and other nerve cells that receive and organize visual information. Your retina sends this information to your brain through your optic nerve, enabling you to see.

Treatment is available for some retinal diseases. Depending on your condition, treatment goals may be to stop or slow the disease and preserve, improve or restore your vision. Untreated, some retinal diseases can cause severe vision loss or blindness.

Retinal disease care at Mayo Clinic

Symptoms:
Many retinal diseases share some common signs and symptoms. These may include:

Seeing floating specks or cobwebs
Blurred or distorted (straight lines look wavy) vision
Defects in the side vision
Lost vision
You may need to try looking with each eye alone to notice these.

When to see a doctor
It's important to pay attention to any changes in your vision and find care quickly. Seek immediate medical attention if you suddenly have floaters, flashes or reduced vision. These are warning signs of potentially serious retinal disease.

EYE DISEASES
squint

A squint, or strabismus, is a condition in which the eyes do not align properly. One eye turns inwards, upwards, downwards, or outwards, while the other one focuses at one spot.

It can happen all the time or intermittently.

This usually occurs because the muscles that control the movement of the eye and the eyelid, the extraocular muscles, are not working together.

As a result, both eyes are unable to look at the same spot at the same time.

It can also happen because a disorder in the brain means that the eyes cannot correctly coordinate.

Strabismus also makes binocular vision impossible, so it is harder for the person to appreciate depth perception.
There are different types of strabismus. They can be described by the cause or by the way the eye turns.

The following terms describe strabismus by the positions of the eye:

Hypertropia is when the eye turns upwards
Hypotropia is when the eye turns downwards
Esotropia is when the eye turns inwards
Exotropia is when the eye turns outwards

EYE DISEASES
Uveitis

Uveitis is a form of eye inflammation. It affects the middle layer of tissue in the eye wall (uvea).

Uveitis (u-vee-I-tis) warning signs often come on suddenly and get worse quickly. They include eye redness, pain and blurred vision. The condition can affect one or both eyes. It primarily affects people ages 20 to 50, but it may also affect children.

Possible causes of uveitis are infection, injury, or an autoimmune or inflammatory disease. Many times a cause can't be identified.

Uveitis can be serious, leading to permanent vision loss. Early diagnosis and treatment are important to prevent the complications of uveitis.

The signs, symptoms and characteristics of uveitis include:

Eye redness
Eye pain
Light sensitivity
Blurred vision
Dark, floating spots in your field of vision (floaters)
Decreased vision

EYE DISEASES
Eye Cancer

If the cancer starts inside the eyeball it's called intraocular cancer. The most common intraocular cancers in adults are melanoma and lymphoma. The most common eye cancer in children is retinoblastoma, which starts in the cells of the retina. Cancer can also spread to the eye from other parts of the body.
Cancers that affect the eye itself are called intraocular (within the eye) cancers.

Cancers that start in the eye are called primary intraocular cancers, and secondary intraocular cancers if they start somewhere else and spread to the eye.

In adults, the most common primary intraocular cancers are:

Melanoma (Intraocular melanoma is the focus of our information on eye cancer)
Non-Hodgkin lymphoma (See Non-Hodgkin Lymphoma (NHL) for more information on primary intraocular lymphoma.)
In children, the most common primary intraocular cancers are:

Retinoblastoma, a cancer that starts in cells in the retina (the light-sensing cells in the back of the eye)
Medulloepithelioma (This is the second most common,but is still extremely rare.)
These childhood cancers are discussed in Retinoblastoma.

Secondary intraocular cancers (cancers that start somewhere else in the body and then spread to the eye) are not truly “eye cancers,” but they are actually more common than primary intraocular cancers. The most common cancers that spread to the eye are breast and lung cancers. Most often these cancers spread to the part of the eyeball called the uvea.

EYE DISEASES
Color Blindness

Nearly all people who are “color blind” can see colors but have difficulty distinguishing between certain colors. Not all people who are color blind have trouble with the same colors – most cannot distinguish between reds and greens; some cannot separate blues from yellows; and a very small group have a condition called monochromatism which only allows them to see black and white.

Color blindness of various kinds affects roughly 8% of men – and less than 1% of women.

What Causes Color Blindness?
Color blindness is a genetic condition caused by a difference in how one or more of the light-sensitive cells found in the retina of the eye respond to certain colors. These cells, called cones, sense wavelengths of light, and enable the retina to distinguish between colors. This difference in sensitivity in one or more cones can make a person color blind.

Symptoms of Color Blindness:
The symptoms of color blindness are often observed by parents when children are young. In other cases, symptoms are so slight, they may not even be noticed. Common symptoms of color blindness include:

Difficulty distinguishing between colors
Inability to see shades or tones of the same color
Treatment for Color Blindness:
There is no known cure for color blindness. Contact lenses and glasses are available with filters to help color deficiencies, if needed. Fortunately, the vision of most color-blind people is normal in all other respects and certain adaptation methods are all that is required.