Retina & Retinal Disease

Retina & Retinal Disease

Retina

The retina is the delicate inner lining of the eye. It is about 1 millimeter thick and is composed of a number of layers. The retina acts like the film in a camera. When light strikes the retina, it "takes the picture" via a complex chain of chemical reactions that changes light rays into electrical impulses. The impulses are then transmitted to the brain through the optic nerve. If any part of the delicate retina is damaged, some degree of vision will be lost

The macula is the area in the retina responsible for central vision. It also allows recognition of fine detail and color. A diseased macula affects both close and distance vision, and is the cause of difficulty in such activities as reading books and looking at street signs. Light sensitive cells called cones, responsible for both central and color vision, are most common in the macula and are hardly found at all at the edge of the retina.

Rods are light-sensing cells in the retina that are responsible for night vision. They are numerous in the peripheral retina. If this region is damaged, it is difficult to move around without bumping into things or to fix one's gaze on a moving object.

The vitreous is the clear, gel-like substance that fills the eye. A healthy retina is necessary for good vision.

Retina & Retinal Disease

Retinal Disease

To examine the retina, an ophthalmologist will dilate your eyes during a comprehensive examination. To dilate, or widen, the eyes, drops are placed in them. A retina specialist then uses a special magnifying lenses to exam your retina. The dilation will reverse after several hours.

How does AMD occur?

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During normal aging, yellowish deposits, called drusen, form under the retina, which is the light-sensitive layer of tissue at the back of the eye that provides clear, sharp images As drusen increase in size and number, they can interfere with proper functioning of the retina, damaging or killing the light-sensitive cells of the macula.

Because the macula's light-sensitive cells provide the ability to have sharp, detailed vision, the results can be blurring of central vision and a devastating impact on the ability to enjoy activities of daily life, such as reading, driving, or even recognizing the face of a friend or family member. This form of age-related macular degeneration is called dry AMD. Dry AMD can be a precursor to wet AMD.

Wet AMD occurs when abnormal blood vessels behind the retina start to grow under the macula. These blood vessels often leak blood and fluid, damaging or killing light-sensitive cells—loss of vision occurs quickly.

Although approximately 80 percent of patients with age-related macular degeneration have dry AMD, wet AMD is responsible for 80 to 90 percent of severe loss of vision or legal blindness associated with this disease.

Symptoms

  • Need for brighter light when reading
  • Difficulty adapting to low light levels
  • Increased blurriness of printed words
  • Decrease in brightness of colors
  • Blurred spot in the center of the field of vision
  • Blank or black spot in the field of vision (spot will start small and grow over time, possibly leading to blindness
  • Abrupt decline in central vision
  • Visual distortions, such as straight lines appearing wavy, or objects appearing larger or smaller than they are
  • Quick image transfer via network, USB stick or DVD/CD.
  • Well-defined blind spot in the center of vision.

It is important to pay close attention to any decline in central vision—both near and distant. If you notice any of these signs or symptoms, schedule an examination with a retina specialist. Risk factors

  • Cigarette smoking
  • Obesity
  • Hypertension (high blood pressure)
  • Excessive sun exposure
  • Diet deficient in fruits and vegetables

Diagnostic tests

  • Dilated eye exam
  • Ocular coherence tomography
  • Amsler grid

Diabetic Retinopathy Hypertensive Retinopathy

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Diabetic retinopathy occurs as a result of high blood sugar, and can cause blindness if left untreated. Diabetic retinopathy is an eye condition that affects people with diabetes who have high blood glucose, or blood sugar, over a prolonged period of time. Too much blood sugar can damage the blood vessels in the back of the eye, preventing the retina from receiving the proper amount of nutrients it needs to maintain vision.

The retina is light-sensitive nerve tissue at the back of the eye. As light enters the front of the eye, the retina converts the light rays into electrical impulses that travel along the optic nerve to part of the brain called the visual cortex. The brain then combines images sent from both eyes to interpret them as a single, three-dimensional image. This allows us to perceive depth and distance. Without the retina, the eye cannot communicate with the brain, making vision impossible.

Diabetic retinopathy occurs when diabetes damages the tiny blood vessels in the retina. In the early stages of diabetic retinopathy, called non-proliferative retinopathy, these blood vessels leak fluid and distort sight. In the more advanced stage of diabetic retinopathy, called proliferative retinopathy, fragile new blood vessels grow around the retina and in the vitreous humour (a clear substance that fills the eye). If left untreated, these blood vessels may bleed, clouding vision or detaching the retina.

Anyone with diabetes -- either type 1 or type 2 diabetes -- is at risk of developing diabetic retinopathy. However, the type of diabetes a person has, how often their blood sugar fluctuates, how well-controlled their blood sugar is, and how long a person has had diabetes all affects his or her risk. The better you control your blood sugar levels, the lower your risk. The NHS estimates that 25% of people with type 1 diabetes or as many as 40% of people with type 2 diabetes will be affected by diabetic retinopathy.

What happens if diabetic retinopathy is not treated?

In untreated diabetic retinopathy scar tissue that forms on the back of the retina as a result of a contraction of the new blood vessels can cause the retina to pull away from the back of the eye. This is called a retinal detachment, or a detached retina. Retinal detachment can cause permanent blindness if left untreated.

Diabetic retinopathy can also cause macular oedema. The macula is the most central part of the retina that allows details to be seen. When fluid from blood vessels leaks into the macula, it can swell, making vision blurry.

Symptoms

There are often no early symptoms of diabetic retinopathy and sight may not be affected until the condition is severe. Sometimes loss of central vision when reading or driving, loss of the ability to see colour, and blurriness of vision are the only signs of diabetic retinopathy. Small spots or floaters may also indicate blood vessel leaks and may clear up in days, weeks or even months. However, because bleeding often occurs more than once, it is important to have an eye examination each year, and immediately if you experience any of these symptoms

Macular Hole/Pucker

What is a Macular Hole?

A macular hole commonly occurs when a proliferation of repair cells-called an epiretinal membrane- contracts, pulls on, and tears the central retina called the macula. Macular holes can also form as a result of the vitreous pulling up on the macula as it separates from the back of the eye or by trauma to the eye from decelerating injuries. In some cases, the exact cause of the macular hole is unknown. Macular holes have several stages ranging from a partial thickness (one that goes only part way through the macula) to a full-thickness defect (one that goes all the way through the macula).

Symptoms

  • Central blind spot
  • Blurry vision
  • Decreasing vision
  • Distortions
  • Central flashes
  • Double vision in affected eye

Risk factors

Age is the biggest risk factor for developing a macular hole and most cases occur in patients over 70 years old. Patients who have any of the following conditions, no matter the age, are at a higher risk of forming a macular hole:

  • Posterior Vitreous Detachment
  • Recent eye surgery or eye laser treatment
  • Diabetes
  • Vein Occlusions
  • Recent trauma to the eye
  • Inflammatory eye conditions

Dignostic Tests

  • Optical Coherence Tomography (OCT)
  • Fundus Photography
  • Fluorescein Angiography

Treatments available

A macular hole may stay the same size or it may get larger. It is important to get regular check-ups because the progress of a macular hole is hard to predict.

When a macular hole is an impending hole (not yet occurred), only observation is required to track changes in the membrane and its effect on vision.

Surgical intervention is necessary when a macular hole extends most of the way through the macula and/or if it affects vision or daily life activities. A vitrectomy and the placement of a gas bubble into the eye are used to close a macular hole. To prevent future complications, the top most layer of the retina (called the internal limiting membrane) is often peeled off.

Retinoblastoma

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Symptoms

  • White pupillary reflex (leukocoria), an abnormal white reflection from the retina
  • Lazy eye
  • Poor vision
  • In rare instances, retinoblastoma can present as an inflammation of the eye.

Causes

Retinoblastoma is caused by a gene mutation during cell division. In half of all retinoblastoma cases, there is no family history of eye cancer. However, if the gene mutation does run in the family, a child's chances of developing retinoblastoma increase substantially.

In most cases, diagnosed children are age 5 or younger, but retinoblastoma can occur as early as year 1

Risk factors

The greatest risk factor for retinoblastoma is having a first-degree relative having had the disease.

Complications

The life prognosis for retinoblastoma patients is usually good if the cancer has not spread to other parts of the body. Vision prognosis depends on the extent of the involvement in the eye and the location of the tumor.

Diagnostic tests

  • Ultrasonography (ultrasound)
  • Photos to document the tumor size, location, and response to treatment
  • Neuroimaging (MRI scanning) to evaluate whether there is involvement of the central nervous system
  • Neuroimaging (MRI scanning) to evaluate whether there is involvement of the central nervous system

Retinal-Detachment

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A retinal detachment occurs when the retina is lifted or pulled from its normal position in the eye. It may begin with a small tear or break that leads to a full detachment.

Signs of a detachment or tear include a sudden or gradual increase in floaters or specks that float in your field of vision. It may also begin with a curtain over the field of vision.

A retinal detachment can occur at any age, but it is more common in people over age 40. It affects men more than women and Whites more than African Americans.

A retinal detachment is a medical emergency and should be treated as one. If not treated promptly, it can result in permanent vision loss.

If you think you have suffered a retinal detachment, contact a retina specialist.

Repair of Retinal Detachment with Scleral Buckling

The surgery may be done under general anaesthesia (you will be sound asleep) or local anaesthesia (you will be awake but an injection will prevent any pain). The retina is reattached by freezing (cryosurgery) and with the placement of a permanent silicon patch (buckle) on the wall of your eyeball. The external stitches will melt away and do not have to be removed. Usually the eye responds to one operation; occasionally, additional surgery may be required. The eyelashes are cut before surgery but they always grow back. You will probably spend one or two nights in the hospital after the operation. Normally, only the operated eye is bandaged but, sometimes, both eyes may be bandaged for a few days. Most patients can return to work in four to five weeks.

Retinitis Pigmentosa

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Retinitis pigmentosa is an inherited retinal disorder that primarily affects the rods—the photoreceptors (light-sensing cells) responsible for peripheral (side) and night vision. The name retinitis pigmentosa refers to the characteristic finding of pigmentary (color) changes seen with a dilated eye examination.

Retinitis pigmentosa, or "RP," can be inherited in 3 ways:

  • An autosomal (non-sex-related) dominant chromosome (50% chance of inheritance)
  • An autosomal recessive chromosome (often a low chance of inheritance)
  • An X-linked (female-linked) chromosome, where inheritance often is demonstrated only in males and is passed through unaffected mothers, known as carriers

Symptoms

  • Night blindness
  • Loss of peripheral (side) vision
  • Cataracts
  • Loss of central vision

Causes

Retinitis pigmentosa is caused by defects in certain genes that result in damage to the retina. Risk factors

Retinitis pigmentosa can often run in families (autosomal dominant or X-linked forms), and is a genetic disease that affects 1 in 4000 in the United States.

Complications of retinitis pigmentosa include:

  • Cataracts
  • Macular edema (swelling of the retina in the macular area)
  • In rare instances, vitreous floaters or hemorrhage

Retinopathy Of Prematurity (ROP)

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Retinopathy of prematurity (ROP) is a disease that occurs in premature babies. It causes abnormal blood vessels to grow in the retina, the layer of nerve tissue in the eye that enables us to see. This growth can cause the retina to detach from the back of the eye, leading to blindness.

Some cases of ROP are mild and correct themselves, but others require surgery to prevent vision loss or blindness. Surgery involves using a laser or other means to stop the growth of the abnormal blood vessels, making sure they don't pull on the retina.

The inside of the eye, the retina is not fully developed in premature babies. Abnormal blood vessels can develop in such a retina. These abnormal blood vessels can cause internal bleeding and even retinal detachment. This is called Retinopathy of Prematurity (ROP). This condition results in low vision or blindness - both of which are irreversible.

Blood vessels grow from the center of a developing baby's retina 16 weeks into the mother's pregnancy, and then branch outward and reach the edges of the retina 8 months into the pregnancy. In babies born prematurely, normal retinal vessel growth may be disrupted and abnormal vessels can develop, which can cause leaking and bleeding in the eye.

ROP can stop or reverse itself at any point, so it often resolves as the baby grows. Sometimes, though, the disease may progress to cause scarring, which pulls the retina away from the rest of the eye.

ROP has no signs or symptoms. The only way to detect it is through an eye examination by an ophthalmologist.

Treatment

ROP surgery is used to stop the growth of abnormal blood vessels by focusing treatment on the peripheral retina (the sides of the retina) to preserve the central retina (the most important part of the retina). ROP surgery involves scarring areas on the peripheral retina to stop the abnormal growth and eliminate pulling on the retina.

Since surgery focuses treatment on the peripheral retina, these areas will be scarred and some amount of peripheral vision may be lost. However, by preserving the central retina, the eye will still be able to perform vital functions like seeing straight ahead, distinguishing colors, reading, etc. The most frequently used methods of ROP surgery are:

  • laser surgery
  • cryotherapy

For more-advanced cases of ROP where retinal detachment has occurred, these methods are used:

  • scleral buckling
  • vitrectomy

Caring for Your Child

If admission to the hospital isn't necessary, you'll be able to take your child home about an hour after the procedure. Follow-up care for ROP surgery includes giving your child eye drops (to prevent infection) for at least a week.

To make sure the eyes are healing properly and that ROP hasn't returned, eye exams should be scheduled based on instructions from the ophthalmologist. This is usually every 1-2 weeks. For scleral buckling, the ophthalmologist must examine the buckle every 6 months to account for your child's growing eye. The goal of surgery for retinopathy of prematurity is to stop the progression of the disease and prevent blindness. Although ROP surgery has a good success rate, not all babies respond to treatment. Up to 25% of babies who have ROP surgery might still lose some or all vision.

Keep in mind that for all types of ROP surgery, a degree of your child's peripheral (side) vision will be lost. And even if the ROP has stopped progressing, vision still can be affected. Since some vision loss and complications can occur, any child who has had ROP surgery should have regular, yearly eye exams well into adulthood.

Retinal Tear

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What are Retinal Tear?

The back cavity of the inner eye is filled with clear jelly called vitreous . When the vitreous jelly undergoes the natural aging process it deteriorates and becomes liquid. As the eyeball moves, small pockets of liquid vitreous can move around as well inside the vitreous cavity. This movement causes the vitreous to pull on the retina, causing flashing (photopsia).

Normally the jelly is only loosely adherent to the retina and easily peels away

from the retina during vitreous degeneration (syneresis). This event is called a posterior vitreous detachment (PVD) and again is a normal event occurring in most people sometime between 50 and 70 years of age.

However, occasionally, the vitreous jelly is so adherent to the retina and pulls so hard on it that it creates a tear. If this tear is along a blood vessel of the retina this may cause bleeding into the vitreous (called a vitreous hemorrhage) which could lead to a shower of floaters which cloud the vision. Acute retinal tears with or without flashes and floaters pose a risk because fluid can enter through the tear under the retina and lift the retina off, causing a retinal detachment, much like damp wallpaper peeling from the wall. Since PVDs are usually the initiating event of most retinal detachments, this is why PVDs are such a concern.

Retinal tears may be sealed with lasers or cryotherapy (a freezing treatment), or both, to prevent retinal detachment. These treatments are usually painless and seal the retina to the wall of the eye. Both of these procedures create a scar to seal the retina to the back of the eye. This prevents fluid from traveling through the tear and under the retina, and is thought to be helpful in preventing a retinal detachment.

A retinal tear is considered so serious because the vitreous liquid may leak through the tear, and pool under the retina. Gradually, the build up of liquid separates the retina from the wall of the eye, a condition called a Rhegmatogenous Retinal Detachment ( a retinal detachment associated with a hole or break in the retina). Retinal Detachments are a separation of the retinal tissue from the inside wall of the eye. Similar to wallpaper coming lose from a wall, the retinal tissue may develop folds or come completely away from its proper position along the interior of the eye resulting in loss of vision.

Symptoms

New Floaters: The presence of some floaters is common because the vitreous is not completely transparent or uniform in consistency. However, a sudden increase in the number and size of floaters perceived in your vision is a warning sign that a retinal tear could be in progress.

Flashes: The sudden appearance of flashes in vision may indicate that the vitreous material is pulling away from or tugging on the retina, which could be the first stage of a retinal tear or detachment.

Shadow or curtain over vision: The onset of a growing, dark shadow or the appearance of a curtain being pulled over a portion of the vision in one eye is an indication of a retinal detachment. These symptoms usually occur in the peripheral (side) vision. The growing shadow results from the increasing area of retinal tissue being pulled away from the back wall of the eye and no longer able to react to light.

Decreased vision: Another common symptom of a retinal tear or detachment is a sudden decrease in vision.

Many people experience flashes or floaters and these are not necessarily a cause for alarm. However if they are severe and seem to be getting worse, and/or you are losing vision then you should see an ophthalmologist immediately. An eye examination with dilated pupils will allow the determination of the source of your symptoms, as well as a recommendation for the appropriate treatment. Prompt treatment can often minimize the damage to your eye.


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