Retinoblastoma (intra-ocular tumor)

Retinoblastoma is the most common intra-ocular tumor of childhood. The underlying pathology involves inactivation of the Rb suppressor gene, which may be familial or sporadic.
It is highly malignant tumor, and failure to diagnose and treat the disease early may lead to death from liver and brain metastases. The other manifestations of the disease may include strabismus, decreased vision, ocular inflammation, eye pain, glaucoma, and orbital cellulitis. The diagnosis is highly suspected with Ultrasound or CT scan findings of a mass with calcifications.

Tumor suppressor gene : Rb
Associated tumor : Retinoblastoma , Osteosarcoma
Gene product : Inhibits E2F; blocks G1 -> S phase.

Diagnostic findings : 

Circular grouping of dark tumor cells surrounding pale neurofibrils
Homer-Wright rosettes (neuroblastoma, medulloblastoma, retinoblastoma)

Extraocular Muscles : Function and Innervation

Eye Movement Control Systems

Extraocular Muscles : Function

Superior Oblique muscle : can depress and abduct the eye from the neutral position. From the adducted position, it is the only muscle that can depress the eye

Inferior Oblique muscle : can elevate and abduct the eye from the neutral position.From the adducted position, it is the only muscle that can elevate the eye

Superior rectus muscle : can elevate and adduct the eye from neutral position. it is the only muscle that can elevate the eye from the abducted position

Inferior rectus muscle : can depress and adduct the eye from the neutral position. From the abducted position , it is the only muscle that can depress the eye.

The Lateral rectus muscle can abduct the eye.

Innervation:

Cranial Nerve III :

• Medial rectus : adducts eye
• Superior rectus : elevate, intorts, adducts eye
• Inferior rectus  : depresses, extorts, adducts eye
• Inferior Oblique: elevates, extorts, abducts eye

Cranial Nerve IV : 

• Superior Oblique : depresses, intorts , abducts eye

Cranial Nerve VI : 

• Lateral rectus: Abducts eye.

Glaucoma

“Glaucoma,” a Principal Cause of Blindness. Glaucoma is one

of the most common causes of blindness. It is a disease

of the eye in which the intraocular pressure becomes

pathologically high, sometimes rising acutely to 60 to

70 mm Hg. Pressures above 25 to 30 mm Hg can cause

loss of vision when maintained for long periods.

Extremely high pressures can cause blindness within

days or even hours. As the pressure rises, the axons of

the optic nerve are compressed where they leave the

eyeball at the optic disc.This compression is believed to

block axonal flow of cytoplasm from the retinal neuronal

cell bodies into the optic nerve fibers leading to

the brain. The result is lack of appropriate nutrition of

the fibers, which eventually causes death of the involved

fibers. It is possible that compression of the retinal

artery, which enters the eyeball at the optic disc, also

adds to the neuronal damage by reducing nutrition to

the retina.

In most cases of glaucoma, the abnormally high pressure

results from increased resistance to fluid outflow

through the trabecular spaces into the canal of Schlemm

at the iridocorneal junction. For instance, in acute

eye inflammation, white blood cells and tissue debris

can block these trabecular spaces and cause an acute

increase in intraocular pressure. In chronic conditions,

especially in older individuals, fibrous occlusion of the

trabecular spaces appears to be the likely culprit.

Glaucoma can sometimes be treated by placing drops

in the eye that contain a drug that diffuses into the

eyeball and reduces the secretion or increases the

absorption of aqueous humor.When drug therapy fails,

operative techniques to open the spaces of the trabeculae

or to make channels to allow fluid to flow directly

from the fluid space of the eyeball into the subconjunctival

space outside the eyeball can often effectively

reduce the pressure.

Glaucoma is a condition of increased fluid pressure inside the eye. The increased pressure causes compression of the retina and the optic nerve which can eventually lead to nerve damage. Glaucoma can cause partial vision loss, with blindness as a possible eventual outcome.

Cataracts

“Cataracts” are an especially common eye abnormality

that occurs mainly in older people.A cataract is a cloudy

or opaque area in the lens. In the early stage of

cataract formation, the proteins in some of the lens

fibers become denatured. Later, these same proteins

coagulate to form opaque areas in place of the normal

transparent protein fibers.

When a cataract has obscured light transmission so

greatly that it seriously impairs vision, the condition can

be corrected by surgical removal of the lens.When this

is done, the eye loses a large portion of its refractive

power, which must be replaced by a powerful convex

lens in front of the eye; usually, however, an artificial

plastic lens is implanted in the eye in place of the

removed lens.

A cataract is a cloudy or opaque area in the lens of the eye. Cataracts usually develop as a person gets older and may run in families. Other environmental factors such as smoking or exposure to toxic substances can also accelerate the development of a cataract. Cataracts can cause visual problems such as difficulty seeing at night, seeing halos around lights, and sensitivity to glare.

Astigmatism

Astigmatism is a refractive error of the eye that causes the visual image in one plane to focus at a different distance from that of the plane at right angles. This most often results from too great a curvature of the cornea in one plane of the eye.

Astigmatism is the most common refractive problem responsible for blurry vision. You may also hear astimatism called a refractive error.Most of the eyeball's focusing power occurs along the front surface of the eye, involving the tear film and cornea (the clear 'window' along the front of the eyeball). The ideal cornea has a round surface. Anything other than round contributes to abnormal corneal curvature -- this is astigmatism. Here's a good way to demonstrate the effects of astigmatism. Look at your reflection in the curved surface of a round soup spoon and compare it with your reflection in an oval teaspoon.The cornea is the transparent window over the colored part of the eye. It bends (refracts) light rays and helps focus the light onto the retina in the back of the eye so people can see. When the cornea is oblong shaped, it causes light rays to focus on two different points on the retina, instead of just one. As a result, people with significant astigmatism may have distorted or blurry vision.

Signs and symptoms of astigmatism may include:

• Distortion in portions of your visual field
• Blurred vision
• Eyestrain
• Headaches

Presbyopia

As a person grows older, the lens grows larger and thicker and becomes far less elastic, partly because of progressive denaturation of the lens proteins.
The ability of the lens to change shape decreases with age. The power of accommodation decreases from about 14 diopters in a child to less than 2 diopters by the time a person reaches 45 to 50 years; it then decreases to essentially 0 diopters at age 70 years. Thereafter, the lens remains almost totally non accommodating, a condition known as “presbyopia.”
Once a person has reached the state of presbyopia, each eye remains focused permanently at an almost constant distance; this distance depends on the physical characteristics of each person’s eyes. The eyes can no longer accommodate for both near and far vision.
To see clearly both in the distance and nearby, an older person must wear bifocal glasses with the upper segment focused for far-seeing and the lower segment focused for near-seeing (e.g., for reading).

Eye Diseases

Eye Diseases
Some eye problems are minor and fleeting. But some lead to a permanent loss of vision. Common eye problems include
Cataracts - clouded lenses
Glaucoma - damage to the optic nerve from too much pressure in the eye
Retinal disorders - problems with the nerve layer at the back of the eye
Conjunctivitis - an infection also known as pinkeye

Your best defense is to have regular checkups, because eye diseases do not always have symptoms. Early detection and treatment could prevent vision loss. See an eye care professional right away if you have a sudden change in vision or everything looks dim or if you see flashes of light. Other symptoms that need quick attention are pain, double vision, fluid coming from the eye and inflammation.


At the age of 6, one child out of three has ametropia. This word refers to well-known disorders such as long-sightedness, astigmatism and short-sightedness. They can affect one eye or both of them. These disorders are easily corrected ! Besides, some can disappear as we get older, such as long-sightedness.



Long-sightedness :
The eye is too short : the image which is received gets impressed behind the retina and not on it. The eye needs to compensate by permanent accommodation which tires it.


Short-sightedness :
The eye is too long : the image which is received gets impressed in front of the retina and not on it. The distance between the retina and the cornea is too big and the eyes cannot focus on distant objects.
Astigmatism : The curvature of the cornea is very irregular. Instead of being round, it is oval, like a rugby ball ! In some rarer cases astigmatism is due to a fault in the crystalline lens. In both cases the objects appear distorted.

Maintaining Good Eyesight

Good eyesight plays an important role in your mobility and the enjoyment of life, so it's important to follow these basic steps to keep your eyes seeing clearly.

Visit Your Eye Doctor
You should visit your eye doctor for an eye exam at least once every one to two years to help maintain good eyesight. See your ophthalmologist if you experience eye infections or symptoms of disease like loss of or blurred vision, light flashes, eye pain, redness, itching, swelling and irritation around the eye or eyelid.

Practice Disease Prevention
Disease of the eye is the number one cause of blindness. Most diseases that cause blindness, like glaucoma and diabetes, can be treated or their progression slowed down with the proper diagnosis and management. While there is no cure for some eye conditions, there have been major medical advances for age-related macular degeneration, glaucoma, and cataracts. By visiting your eye doctor on a regular basis, you can catch any eye problems in their early stage when they are easier to treat.

Protect Your Eyes From the Sun's Harmful Rays
Constant exposure to ultraviolet light can damage your eyes. Too much exposure increases pigmentation in the eye, causing a discoloration known as "brown" or "sunshine" cataracts. Some eye diseases, such as macular degeneration, have been linked to UV exposure.

Wear Protective Gear and Eyewear During Work and Sporting Events
Wearing safety glasses and protective goggles while playing sports or working with hazardous and air-born materials lowers your risk for eye injury, impaired vision and complete loss of sight.

regards by
Dr.M M ADNAN
contact id:danieddy20006@hotmail.com