Retina & Vitreous
The Vitreoretinal Service at Abhinam Eye Care Centre offers expertise in diagnostic, medical. Diagnostics forming the backbone of every successful treatment, we provide fundus camera for Fundus Fluorescein Angiography, and a precise Optical Coherence Tomography system. Treatment of all retinopathies affecting the eye due to diabetes, hypertension, vascular malformations and age related macular degeneration is possible with laser and anti-VEGF injections or surgery depending on the requirement. The retina laser service houses an advanced Argon-Laser System for Retinal Photocoagulation.
The Retina is an extremely crucial structure for vision. It is located in the posterior segment (back of our eye). In lay terms it is called the curtain of the eye.
The retina can be divided into two regions: the central (macula) and the peripheral. The macula is a very small area in the centre of the retina upon which light rays are focused by the cornea and the lens of the eye. The macula being the most sensitive portion of the retina is responsible for acute (sharp) vision, – that is for reading, writing, threading a needle and other fine tasks. The periphery of the retina gives us vision to the side, which is called “peripheral vision”. This is what we refer to when we say, “I saw something from the corner of my eye.”
Common Retinal Disoders include-
AGE RELATED MACULAR DEGENERATION
Fluorescein Angiography (FA) A special dye (Sodium Fluorescein) is injected into your vein and serial photographs of the retina are taken. The photographs may reveal leaking new vessels (choroidal neovascular membrane), define its location in reference to the centre point and determine any associated finding i.e. hemorrhage, exudates. Fluorescein angiography is an important tool in planning treatment and a recent angiogram is essential at the time of treatment. Repeat angiograms after treatment are indicated to confirm the status of the lesion.
Indocyanine Green Angiography (ICGA) ICGA gives a better study of the deeper (choroidal) circulation. It is indicated in certain cases where the fluorescein angiography is inconclusive e.g. cases with ill-defined membranes, presence of hemorrhage, or polypoidal vasculopathy. It takes longer than fluorescein angiography as photographs are taken till 20 minutes after injection of dye.
Optical Coherence Tomography (OCT) This is a newer noninvasive test, which gives an accurate structural analysis of the retina. It is a non contact scan which provides very high resolution imaging without the need for any injection of any dye etc. At Shroff eye centre we have acquired the latest SPECTRAL DOMAIN OCT machines which have a resolution of 5 microns! It is helpful in diagnosis and very importantly in follow-up of the disease.
Medical Treatment Modalities
Laser Photocoagulation Laser for long has been the mainstay of treatment for many retina disorders as Diabetic Retinopathy, Vascular Occlusion, Age Related Macular Degeneration, Vascular Malformations and as a prophylaxis treatment for Retina Tears and Lattice Degenerations.
Oedema or swelling at the macula (The central fine vision area of the retina) known as Macular Oedema can be well treated with Anti-VEGF injections of Lucentis, Avastin and Triamcinolone Acetate. For years our patients have and are being treated with these injections at regular intervals with improvement in vision and decrease in oedema.
A novel intravitreal drug delivery system has been developed that gradually releases the steroid dexamethasone after it has been inserted into the eye through a small puncture. Since the implant eventually dissolves completely, sequential implants can be placed into the eye over time without the need for surgical removal. It has shown great benefit in treatment of macular oedema due to retinal vein occlusions.
DIABETES MELLITUS is a condition that impairs the body’s ability to use and store sugar (glucose). Sugar is excreted in the urine and the blood sugar is abnormally high. It causes changes in small blood vessels in various organs of the body. Diabetes can cause various changes in the eye as well, particularly in the retina. Diabetic eye disease can cause severe vision loss or even blindness.
When the retina is affected by diabetes, weakened blood vessels may leak fluid or blood, causing damage to the retina.
Conversely an eye with marked changes of Diabetic Retinopathy can have good vision and be totally free of symptoms. Hence it is important for all diabetics to undergo REGULAR EYE CHECK-UP INCLUDING RETINAL EXAMINATION THROUGH DILATED PUPILS especially for people who have been diabetic for a number of years. It is also true that diabetes is often detected in a person, when some changes of retinopathy are seen on routine examination of the eye.
Reduced central vision can occur if the macula gets edematous (swollen). Black spots (floaters) and cobwebs of sudden onset often point to a minor bleed inside the eye. Sudden total loss of vision may occur due to a large bleed into the vitreous.
Investigations for Diabetic Retinopathy
If diabetic retinopathy is noted, color photographs of the retina may be taken and FLUORESCEIN ANGIOGRAPHY performed. helps in identifying what structures and areas need treatment with laser.
OPTICAL COHERENCE TOMOGRAPHY (OCT), which is newer non-invasive diagnostic modality provides a cross-sectional view of the retina and helps in quantifying the amount and type of swelling and guides the treatment.
Treatment of Diabetic Retinopathy
PHOTOCOAGULATION involves the use of a LASER beam to seal leaking blood vessels and prevent growth of abnormal blood vessels.
Recently, along with laser treatment, certain medication when injected into the eye or just outside the eye has shown encouraging results. These medicines include intravitreal Avastin, lucentis as well as steroids. They often need to be repeated in order to keep the swelling in check. Being injected into the eye they are however to be used cautiously and judiciously.
If the vitreous is too clouded with blood or there is traction retinal detachment, laser treatment will not work. In this situation, a surgical procedure called VITRECTOMY needs to be performed. In this operation, opaque vitreous gel is removed from within the eye by a special instrument that simultaneously sucks and cuts the vitreous.
LOSS OF VISION FROM DIABETIC RETINOPATHY IS LARGELY PREVENTABLE.
EARLY DETECTION of diabetic retinopathy is the best protection against sight loss. This is possible by having a complete eye examination including retina check-up once a year or more frequently if advised. In most cases the ophthalmologist can then begin treatment before sight is affected.
Excellent control of diabetes and associated conditions like hypertension, increased blood lipids & cholesterol and renal (kidney) disease, is strongly recommended. However, good control in itself does not guarantee freedom from diabetic retinopathy
Age Related Macular Degeneration
Globally, Age Related Macular Degeneration (AMD) is the third most common cause of ‘legal’ blindness (WHO 2002) whilst in most western countries it is by far the commonest cause of blindness. Macular degeneration usually manifests after 50 years of age. With the rapid rise in the geriatric age group, which is the at risk group, the disorder could take epidemic proportions and become a major public health consideration. At Abhinam Eye Centre, we have a dedicated team of Vitreo-Retinal specialists committed to provide you with the best possible care to protect your vision.
Age Related Macular Degeneration (AMD) is a disease associated with aging, characterized by damage to the central part of the retina called macula. Before we talk about what can go wrong, it is important to understand how the eye works when it is working properly.
Dry AMD It is the most common form found in 90% of patients. Dry AMD occurs when the macular tissues get thin and slowly lose function. The most common symptom of dry AMD is blurred vision which causes difficulty in recognizing faces, increases light requirement for reading and other tasks. Visual deterioration is slow but usually not profound. About 10-20% of people with dry AMD advance to the wet form.
It is the less common but more aggressive form of AMD. If it is not treated it may get worse rapidly. Wet AMD is caused by proliferation of abnormal blood vessels under the retina which may exude or leak out fluid, or bleed and ultimately lead to the formation of a scar under the retina.
Symptoms of AMD
- Diminution of vision in an important symptom of macular degeneration. This lack of ability to see objects clearly affects ones ability to read, drive and see details.
- Straight lines appear crooked or wavy.
- A dark area appears in the centre of vision e.g. words in the central part of the page look smudged.
Risk Factors for AMD
Age – is the greatest risk factor. Although AMD can occur during middle age, studies show that people over 60 years of age are at great risk. The risk increases with increasing age.
Family History of AMD increases the risk.
Race – White populations are more predisposed to suffer vision loss from neovascular AMD than Asian or African populations.
Smoking has a definite correlation
History of hypertension, heart disease, or lung infection adds to risk.
Treatment Of Wet Age-Related Macular Degeneration
Wet AMD can be treated with laser photocoagulation, photodynamic therapy, intravitreal injections or a combination of these. The aim of treatment is to slow the rate of vision decrease or stop further vision loss but the disease some times may progress despite treatment. With the advent of anti-VEGF treatment there are greater numbers of patients who are showing visual improvement.
This outpatient procedure uses the conventional laser to destroy fragile, leaking blood vessels. A high energy beam of light aimed directly on the new blood vessels, destroys and inactivates them, preventing further loss of vision. However, laser treatment may also destroy some surrounding healthy tissue. Only a small percentage of patients where the membrane is away from the centre (fovea) can be treated by this modality. Re-treatments may be necessary. Recently in some cases we combine it with an anti-VEGF agent so as to decrease the chances of recurrence
Intravitreal Injections (Anti-VEGF Agents)
Abnormally high levels of Vascular Endothelial Growth Factor (VEGF) occur in eyes with wet AMD which promotes the growth of abnormal new blood vessels. Anti-VEGF agents block the effects of this growth factor. Treatment by this agent helps slow down vision loss from AMD and in some case improves vision. Multiple injections are often required for complete inactivation of the disease process.
Avastin (Bevacizumab) is an anti-VEGF agent approved for use in colorectal cancer. Ophthalmologists are using it “off label” in AMD and other vascular conditions for its anti-angiogenic property.
Macugen (Pegaptanib Sodium) is the first selective VEGF inhibitor which the FDA approved to treat the pathologic process underlying all subtypes of neovascular AMD.
Lucentis (Ranibizumab) is a recently FDA approved anti-VEGF agent that neutralizes all active forms of vascular endothelial growth factor. It is a recombinant homogenized monoclonal antibody.
Triamcinolone is a slow releasing steroid preparation which helps in reducing the swelling associated with the disease and also has some anti-angiogenic action..
Intravitreal injections are given with aseptic precautions in an operation theatre. The eye is numbed with anesthetic drops and then the injection is given. The procedure is relatively atraumatic but carries a small risk of post injection infection, raised or low intraocular pressure, cataract formation, vitreous hemorrhage, retinal detachment..
The following surgical procedures have been tried but with limited benefit:
Excision of Subfoveal CNVM
Smokers should ensure that the formulation they take does not contain Beta-Carotene as that may increase their risk of developing lung cancer.
- Yearly complete eye check up
- Regular Amsler monitoring once patient is diagnosed to have AMD.
- Anti-oxidants to decrease progression of AMD.
- Healthy DIET rich in green leafy vegetables and fish.
- Avoid smoking.
- Maintain normal BP
- Exercise and avoid obesity.
- If you have lost sight from AMD do not be afraid to use your eyes for reading, watching TV.
Occlusions of the retinal vascular system is the second most common retinal vascular disorder after diabetic retinopathy. They occur due to a blockage of the blood vessels which serve the retina.
Painless loss of vision
Diagnosis is generally clinical
They can be of 2 Types
Venous Occlusions are the more common of the two and has a better prognosis. The drop in vision in this disorder is generally due to thickening of the central part of the retina called the macula which is the area for fine vision
OCT is a useful non invasive diagnostic modality for diagnosing edema or swelling due to vascular occlusions. Fluorescein Angioigraphy is also performed to get to know about blood supply and to determine any risk of future bleeds in these eyes.
Recently intravitreal injections of anti VEGF agents and steroid injections/implants have shown good results in treating macular edema associated with venous occlusions. These may need to be repaeted frequently depending on the patients response to therapy.
Arterial occlusions are less common and are often associated with sever permanent vision loss.
Systemic factors like hypertension, cardiac history, high cholesterol and Diabetes are known to be associated with vascular occlusions. Your ophthalmologist may refer you to a physician or cardiologist in such cases.