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We can consider the eye to be like a camera. The camera has a system of lenses in front which focus light on a film or digital sensors on the back. In the same way the eye has a system of lenses in front which focus light onto a layer at the back called the Retina. This layer has living sensors to sense the light form and send a signal to the brain which interprets these signals as the image we see. The retina is connected to the brain though a living cable which is called the optic nerve.
Retina has a very complex structure having ten layers. The light detector cells (photoreceptora) of the retina are called rods and cones. Cones help more with daylight vision and colour sensing whereas rods are primarily responsible for night vision or vision in low light conditions.
The central part of the retina called the macula has the maximum light sensitivity and resolution ability.
So any disease process which distorts the retina or makes it thicker/thinner or reduces the functional ability of the cells of the retina gravely affect the vision.
To diagnose various retinal diseases certain tests are done such as Fluorescein Angiography and Optical Coherence Tomography. These tests and some common retinal diseases are described in this section. |
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Fluorescein Angiography is an investigation to further investigate the cause of the retinal disease. In this test a dye is injected into a vein on the patient's arm. As the dye reaches the blood vessels of the retina (It takes only 10 seconds!!), sequential photographs are taken using a sophisticated digital camera. The abnormal leakage of dye or absence of normal pattern of dye gives the doctor clues regarding the diagnosis and severity of the retinal disease.
This test is simple with generally no significant side-effects. |
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| Optical Coherence Tomography (OCT) is a tool by which highly magnified photographs of the retina can be taken to study its microscopic structure. The patient has to just sit in front of a machine for a few minutes and look at a particular light while these special images are acquired. It also helps to measure the retinal thickness in microns. So the doctor can determine if the retina is getting thicker or thinner. Also which layers of the retina are getting more affected can be evaluated and the response to treatment can be judged by serial examinations. |
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Retinal Detachment |
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What is retinal detachment? |
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| Retina normally is present at the back of the eye. Forward movement of the neurosensory retina from its usual location is called retinal detachment. This cuts the retina off from its blood supply and nutrition. The retina will degenerate and lose its ability to function if it stays detached long enough. Most commonly a retinal detachment occurs when fluid moves behind a retinal tear to push the retina forwards. |
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| The retina may tear at certain points due to pull by the vitreous gel. Vitreous is a clear gel like substance present in front of the retina. A child's vitreous has the consistency of egg white. and is firmly attached to the retina at certain points. Usually with changes in hydration of the vitreous, it separates from the underlying retina. This separation usually is trouble and symptom free. but may cause tears in the retina at times. This allows fluid to seep under and elevate the retina. |
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What are the types of retinal detachment? |
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There are three major types of retinal detachment:
- Rhegmatogenous (Break)
A break in the sensory layer can cause the fluid to seep in and lift the retina off. This is more commonly seen in eyes weakened by HIGH MYOPIA, EYE INJURY or PREVIOUS EYE SURGERY.
- Tractional
This is the kind of detachment that develops when strands of vitreous or scar tissue pull on the retina as happens in Diabetics.
- Exudative
This kind of detachment results when any inflammatory disease of the eye or some diseases of the body like uncontrolled hypertension or severe anaemia result in collection of fluid under the retina.
Each of these would need a different approach and comprehensive care facility to treat the patient as a whole and not an isolated episode of sight threat.
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How can you tell if you could be having a retinal detachment? |
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There is usually quite a typical presentation of a retinal detachment:
- Flashes of light
- Wavy or watery vision
- Sudden decrease of vision
- 'Sudden shower of floaters' - black spots in front of the eye
- curtain covering the vision and obstructing it
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Who is at risk for retinal detachment? |
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- Myopia- Those who wear minus power glasses are myopic. These people have more chance of developing weak areas in the retina. LASIK surgery to correct the 'number' may rid one of glasses but it does so by altering the shape and /or thickness of the cornea. IT DOES NOT ALTER THE RISK OF RETINAL DETACHMENT in a 'corrected' eye. Even myopes who have had refractive surgery MUST visit an ophthalmologist for a quarterly eye exam to track the retina.
- Ocular trauma- Places the eye at high risk for a detachment.
- Retinal detachment in the other eye- This signifies a weak retina.
- Previous eye surgery- This may be as routine as cataract surgery!
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- Retinal detachment is an OCULAR EMERGENCY. It is critical to report early.
- If you are having flashes and floaters, it may not be a detachment yet. It might just be a tear in the retina. If detected early this can be lasered and a surgery can be avoided.
- PERIODIC EYE EXAM by an OPHTHALMOLOGIST is likely to pick up early the predisposing changes in the retina. The preventive steps can then be taken and retinal detachment can be averted.
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What are the tests you may have to undergo ? |
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- Direct and indirect ophthalmoscopy
- Vision and refraction
- Slit lamp examination
- Intraocular pressure measurement
- Ultrasonography of the eye in some cases
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What are the treatment options available? |
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All rhegmatogenous retinal detachments need immediate specialist consult. All fresh RD's MUST be treated surgically as early as possible.
Exudative RDs usually resolve spontaneously with appropriate management of the underlying condition.
Traction RDs would generally require surgery.
Small tears or breaks may be managed by LASER photocoagulation or cryopexy. |
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1 ) Pneumatic Retinopexy
In this technique the retinal break is treated by cryotherapy (sealing with cold) and a gas is injected into the eye to push back the retina. It is generally done for retinal detachments with small breaks in the upper part of the retina.
2) Scleral Buckling Surgery
This is the most common surgery done for retinal detachments. The retinal tear is first repaired with cryopexy, the fluid behind the retina drained out and thereafter, a silicone buckle is used to indent the sclera at the point of retinal break to help it attach back in place.
3) Vitreo-Retinal Surgery
This is a highly complex surgery done for retinal detachments with multiple tears or complicated/ old retinal detachments. In this procedure the gel like fluid (vitreous) in front of the retina is first removed by a technique called vitrectomy. This requires specialised equipment. Following vitrectomy any other traction on the retina is relieved then the fluid behind the retina is drained and laser is done to seal the retinal tears. Finally a special gas or silicon oil is injected in the eye to push back (tamponade) the retina till firm adhesions form around the tears. Following the surgery the patient has to maintain a particular posture to ensure proper tamponade. In case oil is injected it needs to be removed by a minor surgery at a later date decide by the doctor. In case gas is injected it absorbs on its own in 1-1.5months, however air-travel is not permissible till there is gas in the eye. |
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What can you expect after the surgery? |
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- Strict head and eye positioning will be required in the immediate postoperative period and is critical for the result. Some amount of redness of the eye, watering and discomfort would be there till the sutures absorb.
- The "curtain" that got you to the doctor in the first place may not immediately disappear. As the retina regains its perfusion and heals, the curtain gradually fades and the vision may clear significantly depending upon the severity and the type of RD and the timely intervention.
- Time of surgical intervention is of critical importance and cannot be overemphasized. The earlier the surgery is done, the more are the chances of visual recovery.
- Unfortunately, all retinas may not reattach by one surgery alone or may re-detach following a successful surgery due to formation of scar tissue. However, with present technology the results are encouraging. Still a few cases might not re-attach and such eyes would continue to lose vision.
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Can my other eye be affected ? |
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| Patients who have had a retinal detachment in one eye are at a higher risk of developing a detachment in the other eye. They must get their other eye screened by a retina specialist for any weak areas in the retina which can be treated to prevent a detachment. |
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Age Related Macular Degeneration |
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Age Related Macular Degeneration (ARMD) is degeneration of the most sensitive part of the retina (sensory part of the eye) called macula. It is mostly seen in people over the age of 50 years.
Initially it is a silent disease and can affect one eye to begin with. At this stage it might be detected by an ophthalmologist on routine retina evaluation. Gradually vision loss increases mainly in the center allowing vision at sides, but makes reading or close work difficult without the use of special low vision aids.
The early stages of ARMD typically start with appearance of deposits beneath the retina called Drusen. These do not affect vision very much by themselves and most people with Drusen will never have a serious loss of vision. However, certain changes may occur that lead to the late stage of ARMD which leads to marked visual loss. |
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What causes it and who is at risk ? |
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The exact cause of macular degeneration is not known though following risk factors have been identified: age, heredity, sex (women more affected then men), light ocular pigmentation, hypertension, cardiovascular diseases, diabetes, photo toxicity and cigarette smoking.
Types: There are 2 types of ARMD: "Dry" and "Wet".
Dry ARMD is the most common form accounting 80-90% of all cases and is associated with ageing. It is caused by degeneration in visual cells leading to yellow-white deposits in layers of retina called drusen or formation of atrophic areas in macula. Overtime dry ARMD may develop into wet type.
Wet or Exudative ARMD is the more severe variety where abnormal blood vessels form beneath the macula which leak fluid and blood under the retina. Blood under the retina is toxic to the photoreceptors and can lead to severe loss of function of retina. |
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What are the sign & symptoms? |
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| If only one eye is affected to begin with, the symptoms may not be noticeable in early stages. Gradually as disease progresses or if both eyes are involved, reading or close work may become difficult. Common symptoms are distortion of objects which are looked at directly eg. curved appearance of a straight door, distorted print lines in book, missing of letters or words while reading, a dark or blank spot in the center of vision, or fading of colors specially blue. |
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As initially it is a silent disease, mostly it is picked up in a routine retina examination by an ophthalmologist .The retinal examination done by an ophthalmoscope will show the findings of this disease process. To assess the condition in detail, certain other test are done:
- Amsler Grid: It is a test paper with graphic picture to be used at reading distance with near glasses on. This is used to check for extent of sight loss, dark spot, distortion or missing of straight lines and also is given to the patient to take home so that he can monitor his symptoms at home and report immediately if there is worsening.
- Fluorescin Angiography / ICG: the photographs of macula are taken after injecting a dye in patient's arm. The dye reaching the eye helps to clarify the type and extent of disease, including detail of abnormal vessels, leaks and membrane formations.
- Optical Coherence Tomography: In this test photographs of the retina are taken to show its microscopic detail. So it can help detect any early thickening of the retina in wet ARMD. Also it can delineate the abnormal blood vessels ( choroidal neovascularisation ) from where the blood oozes. Changes of dry ARMD such as drusen can also be demonstrated. Also it is an excellent tool to follow up after treatment to assess the effect of the treatment done and need for re-treatment.
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How can it be prevented ? |
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There is no prevention of ARMD. Early detection is the key to prevent severe loss of vision. All individuals above 50, especially if there is a family history of ARMD, history of cardiovascular disease, light ocular pigmentation, should get yearly retinal check up for the same. Anyone experiencing following symptoms should consult an ophthalmologist immediately:
- Straight lines appearing distorted- specially in the center of vision
- Dark blurry or white patch in the center of vision
- Color perception changes
Smoking is a risk factor and should be avoided at all costs if any of the risk factor is present.
According to some recent international multicentric trials, multivitamins may slow down progression of dry ARMD. However, excess of fat soluble multivitamins can have their own side-effects and thus consult your doctor before regularly taking multivitamin pills. |
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There is no permanent cure for Dry ARMD. The aim of management is to keep a vigilant check on progression of disease and take measures to improve functional capability of the patient.
- Nutrition: Eat fresh fruits, dark green leafy vegetables. The role of antioxidants/zinc in retarding the progression is not very clear but supplementation with Vitamins A, C and E, zinc and selenium may have a positive effect. A multicentric international trial has demonstrated that Multivitamins slow progression of moderate dry ARMD to severe dry ARMD.
- Sunlight: Blue rays of the spectrum seem to accelerate macular degeneration. Sunglasses with good UV filters for outdoor activities are recommended.
- Smoking: Quit smoking as this accelerates the process of ARMD.
- Early detection: Monitoring of vision by Amsler grid-report immediately to eye surgeon if any change noticed (the development of wet type may need urgent treatment).
- Low vision aids and lighting: These are devices, which can improve quality of living by improving vision for day-to-day activities, specially reading. Special optical devices like magnifiers (hand held, desktops or in spectacles) can be used in various ways. Adequate lighting will make reading more comfortable with 50-watt indoor bulb in metal shade then fluorescent light.
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The mainstay of treatment of Wet ARMD at present is injection of anti-VEGF drugs into the eye. These are special molecules designed to stop further development of blood vessels. So once the abnormal vessel growth under the retina gets inhibited the leakage of fluid and blood also reduces. However at present these injections need to be repeated at regular intervals as once the effect of the drug wanes off the abnormal vessels star growing again. The two main such drugs being used at present are AVASTIN & LUCENTIS. Presently we do not have a drug which can altogether end the process of this abnormal neovascularisation. A lot of research is ongoing to find a permanent cure for ARMD.
Other treatment modalities available for wet ARMD are-
Photodynamic therapy (PDT)- This involves treating the abnormal vessels with a LASER after injecting a dye which selectively enhances LASER energy absorption by only the new vessels thus preventing damage to the overlying retina. This therapy may also be required to be repeated upto 3 times or more. International studies using this dye have found it to prevent further loss of vision in many cases but it is also not hundred percent effective. Moreover, it does not improve vision but aims to stabilise it, whereas the anti-VEGF injections can improve vision also.
Conventional laser treatment- This procedure uses a high-energy laser beam to destroy the fragile leaking blood vessels. This will also not improve vision but may reduce further progressive vision loss. However since the high energy laser also destroys retina, it can only be done for lesions away from the central most sensitive part of the retina called macula.
Combinations treatments combining anti-VEGF injections, intraocular steroid injections and PDT are also being tried in some cases.
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Retinal photograph of a case of Wet ARMD showing a bleed at the centre of the retina |
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Flashes and Floaters |
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Do you see floating black dots in front of your eyes ? |
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Do you see sparks of light in front of your eyes ? |
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| If the answer to the first question is yes then you are suffering from floaters and if the answer to the second question is yes then you are having flashes of light. |
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Yes and No
There are many causes of floaters in the eye of which some may be dangerous while others may not.
A retinal evaluation can help detect any sight threatening lesion.
A sudden shower of multiple floaters should always be investigated.
Flashes are due to pull on the retina (the inner layer of the eye on which images are formed, something like the film of a camera) by vitreous (a gel like substance present inside the eye in front of the retina). This gel normally starts contracting with age and usually lifts off the retina without causing damage. In medical terminology this is called a posterior vitreous detachment (PVD). This generally occurs over the age of 60 years, but can start earlier also especially in myopes (people who wear minus power glasses). During the process of PVD this vitreous gel causes some pull on the retina which causes sensation of light or sparks for some time. This may resolve without causing damage if the vitreous separates smoothly. But, if this pull is strong enough to cause a break in the retina it is usually followed by floaters and can sometimes lead to severe loss of vision by resulting in detachment of the retina.
The floaters are generally due to particles (cells) in the vitreous or due to degeneration of the vitreous itself.
If after a retinal examination the doctor finds no defect in your retina then generally no treatment is required. However, if a retinal break is detected it must be treated immediately. Treatment consists of sealing of the break with LASER to prevent retinal detachment. Retinal detachment means lifting off of retina from its normal position due to seepage of fluid beneath the retinal break. This can lead to a marked fall in vision and blindness if left untreated. Presently retinal detachment is managed by specialized surgery. So to prevent a retinal detachment the retinal breaks must be detected early and treated appropriately with LASER. |
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Diabetic Retinopathy |
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Diabetes is a disease, which affects the small blood vessels of all the organs of the body. As the disease progresses it inevitably involves the microvascular architecture i.e. the blood supply of the retina (sensory part of the eye) also. This manifestation of diabetes is called as diabetic retinopathy.
To simplify- It is a disease of the blood vessels of the retina due to diabetes. |
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What causes it & who are at risk? |
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The main cause is long standing diabetes.
- Among younger-onset patients with diabetes, upto 8% of individuals will have this disease after 3 years of diagnosis and 25% at 5 years, 60% at 10 years, and 80% of diabetics will have this eye problem by 15 years.
- In older type 2 diabetics up to 21% of patients have diabetic retinopathy at the time of first diagnosis of diabetes, and most develop some degree of retinopathy over time.
Uncontrolled diabetes, High blood pressure, High cholesterol, Kidney disease and Low Haemoglobin worsen diabetic retinopathy. |
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What are the symptoms & signs? |
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It may be asymptomatic for a long time.
Once the macula, i.e. the central part of the retina, develops swelling there would be deterioration in eyesight.
If there is bleeding within and in front of the retina, floaters would be seen or the vision may be drastically reduced. Floaters means seeing black spots or lines moving in front of the eye.
Once the central retina is detached the vision loss becomes severe and chances of recovery even after surgery become less. |
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It can be diagnosed by a simple dilated eye examination to see the retina in detail. If significant changes are found then investigations like Fluorescein Angiography and Optical Coherence Tomography may be done.
Fluorescein Angiography: Involves taking photographs of the retina after injecting a dye in a vein in the patient's arm. The dye reaching the eye helps to clarify the type and extent of disease, including detail of abnormal vessels and leakage.
Optical Coherence Tomography: In this test photographs of the retina are taken to show its microscopic detail. So it can help detect any early thickening of the retina in areas of leakage. The type and amount of thickening can be delineated and an assessment of any pull on the retina can also be made. It is an excellent tool to follow up after treatment to assess the effect of the treatment done and need for re-treatment. |
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The gold standard of therapy is LASER photocoagulation.
LASER can help to prevent a bleed in the eye and also decrease swelling of the retina. However, it cannot usually restore vision lost due to the retinal damage. It has to be appropriately timed.
Other options now available are injecting drugs like steroids, AVASTIN and LUCENTIS into the eye. These drugs also aim to reduce the swelling in the retina and help in drying up of the abnormal blood vessels. These are quite effective and can even improve vision in some cases. A major drawback is the effect of these drugs is time limited and many patients require re-injections.
Combination therapy of LASER and injections is also being done. |
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What are the surgical options? |
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Advanced cases with non-resolving bleed in the eye or retinal detachment require advanced microsurgery.
This involves highly complex Vitreo-Retinal surgical procedures.
Today with highly advanced technology, some amount of visual recovery can be achieved in a large number of advanced cases also. |
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| Cases which present early and are adequately lasered generally maintain good vision. A good control of diabetes is most important to slow the progression of disease. A combination of injectable drugs and laser has improved the outcome in moderately advanced cases also. The outcome may not be very good in advanced cases even after surgery, however still some useful vision can be retained. |
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What are the complications? |
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Complications of diabetic retinopathy are non resolving swelling of the retina, bleeding into the eye and detachment of the retina.
Complications of LASER are minimal. In some cases the swelling of the retina might increase initially, but this also normalizes in most patients.
Complications of AVASTIN per se are also minimal , but the main risk is of infection during the injection procedure. To prevent infection we routinely perform the injection in our operation theatre , taking all aseptic precautions.
Complications of steroid injection can again be infection, rise in eye pressure (glaucoma) and cataract.
Complications of surgery can be repeat bleeding into the eye or damage to the retina. |
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Most importantly to slow the progression of diabetic retinopathy the following parameters must be strictly maintained -
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| Mild Non-Proliferative Diabetic Retinopathy |
Mild Non-Proliferative Diabetic Retinopathy |
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| Severe Non-Proliferative Diabetic Retinopathy |
Proliferative Diabetic Retinopathy |
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