Tuesday, November 8, 2011

Vitreous Retina

The Retina is the light sensitive film in the back of the eye. The image is perceived here and transmitted to the brain by the optic nerve. The vitreous is the clear gel that fills the back of the eye. Diseases of the retina can affect any age.

Premature infants can be affected by a disease called - ROP (Retinopathy of pre-maturity). Heredity and age related degenerations can affect the retina - especially the central most sensitive part of the retina called 'macula'.

The retina can detach from the back of the eye - a condition called 'Retinal Detachment'. The Vitreous gel can become opaque due to blood - a condition called 'Vitreous hemorrhage’ this condition can occur in diabetes, following injury and in other conditions too.

FFA (FUNDUS Fluorescein Angiography) Fluorescein angiography, is a clinical test to look at blood circulation inside the eye, it aids in the diagnosis of retinal conditions associated with diabetes, age-related macular degeneration, and other eye abnormalities.

Fluorescein, an orange-red dye, is injected into a vein in the arm. The dye travels through the body to the blood vessels in the retina. A special camera with a filter flashes a blue light into the eye and takes multiple photographs of the retina and also helps to monitor the course of the disease and its treatment. It may be repeated on multiple occasions. No X-rays are involved.

If there are abnormal blood vessels, the dye leaks into the retina or stains the blood vessels. Damage to the lining of the retina or a typical new blood vessels may be revealed as well.

These abnormalities are determined through a careful interpretation of the photographs by an ophthalmologist.

INDOCYANINE GREEN ANGIOGRAPHY (ICG)

An Indocyanine Green study (ICG) is a special dye test used to evaluate the circulatory system of the choroid; the layer just behind the retina.

ICG reacts to light with a longer wavelength than fluorescein dye, allowing the doctor to pinpoint the location of leaking vessels deeper within the eye that may not be apparent with Fluorescein Angiography.

OPTICAL COHERENCE TOMOGRAPHY III

OCT with maximum resolution gives an excellent cut section optical view for in depth analysis of the retina.

We at Aditya Jyot began the use of this diagnostic modality for macular diseases for the first time in India.

OCT is a non-invasive, non-contact, trans-pupillary imaging technology which can image retinal structures in vivo, with a resolution of 10 to 17 microns. Cross sectional images of the retina are produced using the optical backscattering of light in a fashion analogous to B scan ultra sonography.

The anatomic layers within the retina can be differentiated and retinal thickness can be measured. Besides this the optic disc and nerve fiber layer can be assessed in cases of Glaucoma.

HEIDELBERG RETINAL ANGIOGRAPHY

Is a State- of- the- art system to perform Fluorescein and Indocyanine Green Angiography in patients with retinal disorders. An HRA-movie of the early phase of the angiogram can be taken. Very useful for the central pathology with facility of highlighting 10°, 20°, 30° of central macula.

ELECTRORETINOGRAM (ERG)

ERG is the diagnostic procedure to evaluate and confirm diffuse retinal degenerations with the help of mass electric response generated by the retina when subjected to flashes of light.

MULTIFOCAL ELECTRORETINOGRAM (MFERG)

THE MULTIFOCAL ERG which has been introduced for the first time in Mumbai, is used to study local responses from the retina and to determine focal retinal degenerations and lesions.

ELECTRO-OCULOGRAM (EOG)

Is the only means of understanding the measure of retinal function that depends upon the integrity of retinal pigment epithelium layer of the retina.

MULTIFOCAL VISUAL EVOKED POTENTIAL (VEP)

Is useful to objectively evaluate visual acuity and aid in perfect diagnosis by topographically mapping brain activity and determining the presence of visual field and visual acuity deficits.

PREFERENTIAL HYPERACUITY PERIMETER (PHP)

The most sensitive method in the world to detect the beginning of wet age related macular degeneration in the most severe form of ARMD and designed to detect and monitor the progression of the disease in a non-invasive manner.

The PHP examination is easy to administer and takes just 3-5 minutes providing a comprehensive examination covering 14° of the macular area.

TREATMENTS:

1. Laser for Diabetic Retinopathy, Central Retinal Vein Occlusion (CRVO), Branch Retinal Vein Occlusion (BRVO), Retinal Holes, Lattice Degeneration, Central Serous Retinopathy (CSR) and more.
2. Micro pulse diode laser-low intensity red laser for macula.
3. Photodynamic Therapy where a combination of a dye-like substance and laser are used to reduce the leakage from abnormal vessels (choroidal neovascularization) under the macula. The patient is injected with verteporfin which selectively collects in the abnormal leaking vessels under the fovea, the part of the eye that is responsible for our color vision and ability to see detail. A non-thermal laser is then used to "activate" the dye in the leaky vessels. Because the laser used in photodynamic therapy is less intense than that used for laser photocoagulation, this treatment is believed to prevent damage to the retina and fovea.
4. Transpupillary Thermotherapy is an alternative therapy for choroidal neovascularization. This procedure involves the use of a special lens that is placed over the cornea. A laser beam is then passed through the lens to treat leaking vessels.
5. Endoscopic Vitreo Retinal Surgery the first of its kind in Asia.
6. All types of simple and complex Vitreo Retinal Surgeries.

CONDITIONS :

Lattice Degeneration

Lattice degeneration is the thinning and weakening of the retina, the light-sensitive layer of cells lining the back of the eye that can lead to a retinal tear.

The vitreous, a clear gel-like substance that fills the inside of the eye, is contained in a sac loosely attached to the retina. As one grows old; the vitreous takes on a more fluid consistency and the sac sometimes separates from the retina. In lattice degeneration, there are places where the sac is strongly attached to the retina and pulls on it. This pulling weakens the retina and creates lattice lesions that look like white crisscrossing lines on the retina.

If part of the vitreous sac becomes detached from the retina, the friction and pulling where it is still attached can create a tear in the retina. Lattice degeneration can sometimes cause retinal detachments when holes or tears in the lattice formation permit vitreous fluid to get under the retina.

Fortunately most people with lattice degeneration do not develop a retinal detachment.

Though preventive treatment of lattice degeneration has not been shown to prevent retinal detachment lattice degeneration should be monitored. If you have a history of lattice degeneration, you should be aware of the symptoms of retinal tears and detachment.

Detached and Torn Retina

A retinal detachment is a very serious problem that almost always causes blindness unless treated. The appearance of flashing lights, floating objects, or a gray curtain moving across the field of vision are all indications of a retinal detachment. If any of these occur see an ophthalmologist immediately.

As one gets older the vitreous; the clear gel-like substance that fills the inside of the eye, tends to shrink slightly and take on a more watery consistency. Sometimes as the vitreous shrinks it exerts enough force on the retina to make it tear.

Retinal tears increase the chance of developing a retinal detachment. Fluid vitreous passing through the tear lifts the retina off the back of the eye like wallpaper peeling off a wall. Laser surgery or cryotherapy (freezing) is often used to seal retinal tears and prevent detachment.

Myopic Degeneration

Myopic degeneration is an uncommon condition characterized by progressive stretching of the eye that damages the retina, the layer of light-sensitive cells that lines the back of the eye. People with severe nearsightedness (high myopia) are at greater risk for myopic degeneration.

Myopic degeneration commonly occurs during young adulthood with a gradual decrease in central vision. Vision can decrease more abruptly, but typically vision loss is gradual. Although central vision may be lost, side (peripheral) vision usually remains unaffected. Remaining sight can still be very useful and with the help of low-vision optical devices the patient can continue normal activities.

The causes of myopic degeneration are not clearly understood but may include biomechanical abnormalities or hereditary factors. The biomechanical theory assumes that the retina, in a myopic eye, is stretched over a larger than normal area because the eye is longer than usual. Over time, the outer coat of the eye, known as the sclera, also stretches in response to forces like internal eye pressure. This stretching of the sclera is thought to lead to retinal degeneration. In the hereditary theory, the retinal changes are thought to be an unavoidable, inherited process.

The only treatment for myopic degeneration is surgery to reinforce the scleral wall. This has been performed with varying degrees of success.

Macular Edema

Macular edema is the swelling of the macula, the small area of the retina responsible for central vision. The edema is caused by fluid leaking from retinal blood vessels. Central vision, used for reading and other close detail work, is affected.

Because the macula is surrounded by many tiny blood vessels, anything affecting them, such as a medical condition affecting blood vessels elsewhere in the body or an abnormal condition originating in the eye, can cause macular edema.

Retinal blood vessel obstruction, eye inflammation, diabetes, and age-related macular degeneration have all been associated with macular edema. The macula may also be affected by swelling following cataract extraction, though typically this resolves itself naturally.

Eye drops, injections of cortisone around the eye or laser surgery can be used to treat a macular edema. Recovery depends on the severity of the condition causing the edema.