Dr Sayan Das MS, FRCS

Dr Sayan Das MS, FRCS Ophthalmologist. Specialises in Phaco, LASIK, Cornea, Medical Retina and Glaucoma

05/05/2025

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Chapter in a just published book
07/12/2024

Chapter in a just published book

REFRACTIVE SURGERY (LASIK / PRK / SMILE / PHAKIC IOL)Refractive surgery is for individuals who cannot (for occupation-re...
02/08/2024

REFRACTIVE SURGERY (LASIK / PRK / SMILE / PHAKIC IOL)

Refractive surgery is for individuals who cannot (for occupation-related reasons) or do not wish to wear spectacles. (Contact lens is another option, which we have discussed in another post). These procedures correct the refractive error (more commonly known as "power" or "number" in the eye).

There are two groups of procedures. In the first group, laser is used to reshape the cornea (the transparent portion in the front of our eyes, which appears black in colour from outside) without entering inside the eye. LASIK, PRK and SMILE belong to this group. In the second group, a lens, called a Phakic Intraocular Lens is placed inside the eye.

For all such procedures, it is essential that the refractive error stabilises before the procedure is done. For this, the patient's age should be at least 18 years of age (but for safety some doctors consider 22 years as minimum) and the power of spectacles must be stable for at least one year. Refractive surgery, as well as contact lenses, can correct the refractive error, but cannot stabilise it. So, for example, if a patient has a refractive error of -3 D (dioptre) today, and undergoes refractive surgery today for that -3 D, his/her refractive error will become nearly 0 today. But if, the refractive error was to increase from - 3 D today to - 5 D suppose 3 years later, refractive surgery done today will make the power nearly 0 today, but 3 years later refractive error will become - 2 D. This is why waiting for attainment of adequate age and stabilisation of refractive error is so important before refractive surgery is done.

Before refractive surgery, several diagnostic eye tests are done to take measurements of the eye for performing the surgery accurately. For this, a patient used to wearing contact lenses, should discontinue wearing the contact lenses (2 weeks for soft contact lenses, and 3 weeks for rigid contact lenses) before getting the diagnostic tests done. This is because contact lenses can change the shape of the cornea and make the measurements taken during the diagnostic tests inaccurate.

Another important issue is the suitability of the patient for a laser refractive procedure (LASIK / PRK / SMILE). The two most important criteria in this respect are (i) individuals with an abnormal cornea (keratoconus, corneal scar) should not undergo laser refractive surgery, and (ii) the thickness of the cornea must be sufficient to allow for necessary reshaping of the cornea, and a minimum thickness (between 250-300 microns) of the cornea should remain following the surgery, so that the cornea does not become weak and change its shape abnormally in the long-term following the procedure. In these situations, refractive error correction with Phakic IOL is indicated, as it spares the cornea during the procedure.

All refractive surgery procedures are most commonly done for correction of refractive error at distance. Correction of refractive error for near work (which appears after 40 years of age) are available with some machines, but the results, with respect to quality of vision, are still questionable.

LASIK is a laser refractive surgery in which a thin flap is lifted from the cornea (by a blade called microkeratome, or with another laser called femtosecond laser) and the portion of the cornea beneath the flap is reshaped with the excimer laser. For patients with myopia (minus power) the cornea is flattened, and for patients with hypermetropia (plus power) the cornea is steepened. Correction for astigmatism (cylindrical power) can also be performed.

In PRK. which is also a laser refractive procedure, no flap is lifted, and after removing the epithelium (the "skin" of the cornea), excimer laser is applied to the cornea.

In SMILE, after application of a femtosecond laser within the cornea, a portion of cornea is removed from inside the cornea, through a very small incision in the cornea. Proponents of SMILE procedure claim that discomfort in the eyes following the procedure is less compared to LASIK, but hard evidence is still lacking.

In Phakic IOL, a specially designed intraocular lens is implanted in the eye to correct refractive error. These are not the much more commonly used intraocular lenses implanted after cataract removal. Phakic IOLs are usually reserved for patients who cannot undergo laser refractive surgery, as we have discussed above.

Following refractive surgery, almost all the standard measures for protection of the eye following any eye surgery. are also recommended, but this may vary from doctor to doctor.

Most common problem after laser refractive surgery is irritation of the eyes which usually disappear within a few weeks to months. More serious problems, which fortunately seldom occurs, include wrong correction of refractive error, infections, inflammation, and ectasia (abnormal change in shape of the cornea in the long run).



15/12/2022

PHACO (PHACOEMULSIFICATION CATARACT SURGERY)

(With answers to common concerns and queries of patients)

Currently, phacoemulsification (or phaco) is the gold standard of cataract surgery worldwide. This is because it has the following benefits (i) small (less than 2-3 mm) entry wounds in the eye (ii) rapid post surgical recovery for the patient (iii) less interference with the cylindrical power of the eye which can happen with cataract surgery with large entry wounds. In skilled hands, risk associated with phaco is as low as any other form of cataract surgery.

Phaco uses ultrasound energy (delivered by the phaco machine) to liquefy the solid cataract. Following liquefaction, the liquefied material is sucked out from the eye by the machine. Because the solid cataract (which is approximately 10 mm in size when intact) is liquefied, it can get sucked out through a small entry wound, just big enough to insert the instrument (delivering the ultrasound energy) into the eye.

Cataract is the loss of transparency of the natural lens of our eyes. This lens is located in a bag like structure inside the eye. During the surgery, the eye is entered at the junction of the cornea (the part which looks black in color, but is actually transparent) and the sclera (the remaining white part of the eye). Then the front layer of the bag is opened to reach the natural lens, which has become a cataract, inside that bag. Then ultrasound energy is used to break the cataract into small pieces, liquefy those small pieces, and suck them out. ("Phaco" = lens, and "emulsification" = "liquefaction"). After the bag is completely cleaned of cataract, an artificial intraocular lens is placed inside the empty bag. That completes the surgery, which usually takes less than 10 minutes.

An intraocular lens (IOL) is required to substitute the power which the original natural lens provided to the eye, for focussing images of the objects we see. The IOL power is so customised for the patient that he/she, after surgery, is usually able to see at distance clearly, without the need for any spectacles. This measurement of IOL power is done during biometry test before surgery. Other tests usually done before surgery include blood sugar, blood pressure, ECG and checking for any blockage of the passage which drains tears from the eye to the nose.

There are several types of IOLs. One type of IOL (called monofocal IOL) attempts to provide distance vision without spectacles, but patients will need to wear spectacles for near work (reading, using mobile, sewing, etc). Another type of IOL (multifocal IOL) attempts to provide vision for both distance objects and near work, without the need for spectacles. However, these multifocal IOLs have their own drawbacks of decreased contrast sensitivity (decreased ability to distinguish between two very close shades of the same color – and so is not recommended for patients with other eye issues like diabetic retinopathy and age related macular degeneration) and difficulty in driving at night. Another type of IOL (toric IOL) corrects any cylindrical power of the eye, and is available as either monofocal (for distance) or multifocal (for distance and near) IOL.

Common queries of patients planning to undergo cataract surgery:

1) To avoid pain during surgery, there are two methods of anesthesia. Most common is anesthesia obtained using anesthetic eyedrop. This avoids pain during surgery in most patients. But with this method, the patient is still able to move his/her eyes. So, with this type of anesthesia, the patient has to keep his/her eyes steady during surgery and avoid moving them, and for this, he/she is asked to keep looking at a light source during surgery. Most patients feel the eye is being touched (without perceiving pain), and are able to see, during surgery with eyedrop anesthesia. The other method of obtaining anesthesia is with an injection just before surgery. With injection anesthesia, the patient is no longer able to move his/her eyes, usually does not feel any pain/touch sensation, and usually does not see anything during surgery. Injection anesthesia has its own set of risks, and is usually not preferred. However, patients who are anxious, who are not able to co-operate, or who have hearing problems so as to be unable to understand instructions during surgery, are usually given injection anesthesia.

2) Regarding medicines which the patient takes regularly, the patient is asked to continue all medicines before, on the day of, and after surgery, without interruption, particularly those related to blood sugar, blood pressure and cardiac problems. Blood-thinners (such as aspirin and clopidrogel) are not usually required to be discontinued, if the surgery can be done with eyedrop anesthesia. For patients who need injection anesthesia, these medicines need to be stopped for a specific period of time, under the guidance of a physician. Patients taking drugs for prostate-related urinary problems must notify the surgeon regarding their use, because these drugs may create certain problems (floppy iris syndrome) during surgery, which may need preparation and precaution on the part of the surgeon, for a smooth surgery

3) The usual sequence on the day of surgery is as follows. The patient is taken in to the operating zone/theatre. Eyedrop/injection anesthesia is given and the eye is cleaned. The patient is asked to lie down on the table. The eyes are usually cleaned again. Then a cover is placed over the head and upper part of the body, so as to isolate the eye to be operated from the nearby skin of the face. This is very important in order to prevent infection from happening during surgery. Special care is taken so that patient can breathe normally and easily during surgery. The patient is asked to not move his/her head or eyes and to keep looking steadily at a light source focussed on the eye. Then the actual surgery starts.

4) Post-operative care: There is a lot of variation among different surgeons about the post-operative care regimen they prescribe to their patient, although the surgical steps they perform are essentially the same. Here an attempt is made to mention what most surgeons consider standard. Immediately after surgery, usually a dark glass is given (however, some surgeons prefer to cover the operated eye with a pad and patch for a few hours immediately after surgery, before giving dark glasses) for continuous wearing during waking hours. The main purpose of this dark glass is to protect the eye from anything going inside it. The patient is asked to avoid exposure of the operated eye to water, dust, smoke, fingers or anything else. An eye-guard should be applied to cover and protect the eye when the patient lies down to sleep. The operated eye needs to be cleaned in a very hygienic way, at least once daily, as instructed by the surgeon or his/her associate. While applying eyedrops, care needs to be taken so that the dropper tip does not touch the eye, fingers or anything else. The patient, and his/her family members, are required to follow these instructions for a particular period of time, most commonly 7 days. After this period, all these instructions no longer need to be followed and the patient can go back to his/her normal lifestyle, just as before surgery. Even before this period of restrictions is over, there is no restriction for the patient to watch TV, use electronic devices like mobile phone, or read (with his previous glass). There is no dietary restriction after surgery. The patient is given spectacle power, as necessary, at the end of this period.

5) After the recovery period (usually 7 days) is over, most patients do not need to visit their eye doctor anymore, except if they develop any new complaints such as pain or decreased vision (see below). However, patients with other eye issues, such as diabetic retinopathy, glaucoma, age-related macular degeneration, need to be under regular follow up with their eye doctor, even after cataract surgery.

6) Regarding risks of cataract surgery, just like any other surgery, cataract surgery has its own set of complications. The chance of having a complication, during or after phaco, is less than 5 percent. Even after developing a complication, with appropriate care during and after surgery, the predominant majority of patients have good, if not full, visual recovery. However this may require changing the IOL (instead of the IOL which was planned pre-operatively) and/or a second surgical procedure. The major complication, where the outcome becomes uncertain, is infection (called endophthalmitis), and it is expected to occur in less than 2 out of 1,000 patients.

7) Laser cataract surgery (LRCS - Laser refractive cataract surgery, or FLACS - Femto laser assisted cataract surgery) is a variation in which a femtosecond laser is used to perform the initial steps of the surgery which the surgeon does manually, after which conventional ultrasound energy from a standard phaco machine is used to liquefy and suck out the cataract. It increases the precision and accuracy of the procedure, but it also increases the cost of the procedure tremendously. However, large studies on numerous patients have not yet been able to establish significant difference in visual results, between conventional phaco (as described in the beginning of this article) and laser-assisted phaco.

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29/08/2022

CONTACT LENSES:
PROBLEMS AND DO's-&-DONT'S

Refractive error (or “eye/spectacle power” as we call it) is the most common cause of decreased vision. To correct refractive error for clearer vision, we commonly have three options: spectacles, contact lenses, or surgery (in the form of LASIK or phakic IOL). Spectacles are a universally good choice, because they require little maintenance and they can provide significant amount of protection against eye injury. But many people, because of job/sports requirement, cannot or do not wish to wear spectacles. For them, the choices are contact lens and surgery. Surgery does have its inherent risks (although very low), but once the procedure is over, very little attention is required to maintain the benefits of surgery. On the other hand, contact lenses need significant and continuous care and maintenance. Otherwise contact lens may play havoc with the eye. In this article, we are going to discuss a few of those risks, and general maintenance and care to reduce those risks.

The most dreaded risk of contact lenses is infection of the cornea (also called corneal ulcer). It has the potential to cause significant and permanent loss of vision, and in extreme cases, loss of the eye can also occur. The risks of corneal ulcer are due to the contact-lens (or the eye wearing the contact lens) coming in contact with tap water, unclean fingers (used to insert/remove the lens) or any particle entering the eye. Wearing contact lens beyond the prescribed daily time-limit, particularly forgetting to remove the contact lens and wearing them during sleep overnight, significantly increases the risk of corneal ulcer. The most common symptoms of corneal ulcer are intense pain, redness, and discharge. If any of these problems happen, you have to consult an eye doctor immediately.

The other major complications are due to overwear (persistently wearing the contact lens beyond the prescribed daily time-limit) and allergy. Contact lens overwear leads to continuous lack of oxygen for the cornea. This causes encroachment of small blood vessels over the cornea, gradually decreasing the transparency of the cornea, and thus reducing vision. Once established, this condition is very difficult to treat. The other major issue is allergy due to the contact lens material itself or due to deposits accumulating on the contact lens. It is characterised by persistent itching of the eyes.

There are certain universal guidelines for the maintenance and care of contact lenses, which are meant to reduce the risk associated with contact lens wear:

1) Never sleep with contact lenses in your eyes.

2) Do not allow water to get into your eyes, while wearing contact lenses. Do not swim or shower with contact lenses on.

3) Follow instructions from the contact lens prescriber (regarding maximum daily time-limit of wear, duration of use, and contact lens cleaning), contact lens manufacturer, and contact lens solution manufacturer.

4) If you have not worn a pair of contact lens for 30 days at a stretch, re-disinfect it, or better still, discard that pair and use a new pair.

5) Cleaning contact lenses: Wash your hands with soap and water, dry them with lint-free towel, before touching contact lenses. Take out the contact lens from the eye, “rub” the contact lens with your clean fingers, then wash the contact lens with the prescribed solution, before keeping the lens in the contact lens case.

6) Contact lens case care: Every-time you wear the lenses, change the prescribed solution in the case. Regularly clean the case with the prescribed solution and then dry the case. Change the case every three months, or earlier if it is cracked or damaged.

7) Contact lens solution care: Always keep the bottle capped after use. Do not allow the tip of the nozzle to come in contact with anything, not even your fingers. Never keep the solution in any container, other than the bottle in which it was dispensed by the pharmacy. Never dilute the solution with any other liquid. Never use any other liquid (tap water, home-made saline, or even saliva) to clean/wet the contact lens.

If there are new eye problems (pain, redness, irritation, difficulty looking towards light, excessive watering/discharge) while wearing contact lens, consult an eye doctor immediately.

Two types of contact lenses need special mention. Unlike most people wearing contact lenses as an alternative to spectacles (and thus actually for cosmetic reasons), these special contact lenses are actually needed by the patient for comfort or good vision, which spectacles cannot provide for his/her eyes. One type is called scleral contact lenses, which are meant for eyes with very abnormally shaped cornea, in whom spectacles cannot provide adequate vision. The other type is called bandage contact lens, which is meant to provide comfort in painful/irritating corneal diseases, which are otherwise not easily treatable. Bandage lenses are very thin, and unlike all other contact lenses, are meant to be worn continuously (including overnight), for a couple of months or so, and then discarded and replaced. However, bandage lenses cannot improve vision.


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14/07/2022

KERATOCONUS FAQs

Q. My spectacle power is changing quiet frequently. Even with a new pair of spectacles, I am not seeing clearly. For several years now, my eyes have been itching on a daily basis. I am in my late-teens (or early-twenties). What can it be?

A. These are the typical complaints of someone with an eye condition called keratoconus.

Cornea is the portion of the front-wall of the eyeball which appears black from outside. It is actually crystal clear and transparent. Its normal shape nearly resembles portion of a sphere. Both its transparency and its normal shape are vital to its normal functions of allowing light to enter inside the eye and focus these light rays perfectly on the nerve layer on the back-wall of the eye.

In keratoconus, the shape of the cornea gradually resembles a cone. As a result of this conical shape, light rays are no longer focussed perfectly. This error in focus, unlike the common errors of focus called myopia and hypermetropia, cannot be corrected by spectacles. As a result, even with a new pair of spectacles, the patient does not see clearly.

Keratoconus starts in early teens and usually stabilises by late-thirties and early-forties. During this time, there is a slow worsening of vision. Relatively small number of keratoconus cases are hereditary. Many keratoconus cases have no underlying cause. But remaining almost half of all keratoconus patients have underlying eye allergy with itching. It is this constant RUBBING of eyes, for a prolonged period of time over several years, which alters the shape of the cornea from spherical to conical.

To diagnose keratoconus definitively, we need to do a test called corneal tomography. The devices used for this purpose are Pentacam, Orbscan and Sirius.

Treatment consists of two parts (i) preventing further worsening of the condition, and (ii) improving the defect in vision.

For preventing further deterioration of the condition, the current standard of treatment is Collagen Cross Linking (CXL). It is strongly recommended when it has been established by sequential examinations, or by past records, that the condition is worsening. Also, there is a certain minimum requirement of corneal thickness, below which CXL cannot be done. In CXL, the cornea is first soaked with a dye (riboflavin) and then exposed to a particular ultraviolet radiation for a specified time. This results in strengthening of cornea. It has been seen that, after CXL, more than 90% of patients do not worsen further. There are two important issues which a patient undergoing CXL must understand.(i) First, CXL is a stabilising procedure, which means that it does not reverse the condition and thus does not improve vision. The vision remains the same as immediately before the procedure. It only prevents further worsening of vision. This itself is all-important, because the condition may worsen to the point where corneal transplantation, whose success rate is only moderate, becomes necessary. (ii) Second, almost all patients undergoing CXL experience a further mild drop of vision immediately after the procedure, which in a couple of months, restores back to pre-CXL vision in almost all patients. In addition, eye-rubbing has to be avoided to prevent worsening of the condition.

The second part of the treatment is about improving the vision. This must be done only after CXL, if necessary, has been performed to stabilise the condition. Only very mild keratoconus can be corrected with spectacles. Most keraconus patients need contact lenses for visual correction. These are not routine contact lenses. They are special contact lenses meant specifically for keratoconus and related corneal diseases. Those keratoconus patients whose vision does not satisfactorily improve with these specialised contact lenses may need to undergo corneal transplantation.

27/06/2022

EYE INJURY - DO'S AND DONT'S

The eye, being a very sensitive and an extremely delicate organ, is very likely to be injured by external objects coming in contact with it. These injuries have the potential to permanently decrease vision, even if partially. Although we may think that injuries to the eye can occur only during outdoor activities, such as work or sports, surveys have shown that almost half of all eye injuries occur at home. Simple preventive measures and prompt first-aid treatment may go a long way in protecting the eye and preserving vision.

Common ways in which the eye gets injured are blows (from hand/elbow/fist/ball/stick etc), scratches (nails/paper-edges/pen/pencil etc), fast moving flying particles (hammer-chisel/bullets etc) and chemicals (detergents/cleaners/Holi-colours/tear-gas etc). Any of these modes of injury can also occur at home. Children are particularly vulnerable, both to get injured and to have permanent impairment of sight.

After any eye injury, the general first-aid measures include (1) avoiding rubbing, touching or putting pressure on the injured eye, (2) avoiding any attempt to remove any object stuck inside the eye, (3) consulting an eye doctor as soon as possible, and (3) avoiding application of any eye-drop on the eye without consulting an eye doctor. Some eye medicines, particularly steroids, are readily suggested by other people for immediate relief, but can cause serious damage to the eye later.

If the object causing injury is not known to be sharp, two measures which are advised include (1) repeatedly and gently blinking the eye, which may eject a small particle inside the eye with the natural flow of tears, and (2) flushing the eye with clean running tap-water.

If the object causing the injury is sharp (such as knives, scissors, forks, pencil, arrow-tip while playing with bow and arrow, bird-beak etc), then the eyelids should be closed and the eye should be covered with a pad and bandage. In this situation, flushing with water, squeezing the eyes, and application of any eye-drops are to be avoided. If immediate consultation with an eye doctor is not possible, the eye is to be kept covered, tetanus injection is to be given, and antibiotic tablets should be started after consulting with a general physician.

Flushing the eyes with clean running tap-water is absolutely vital, if the agent causing the injury is a chemical. In this situation, the more the amount of water used to flush the eyes, the better it is. An amount equivalent to ten to fifteen litres may be considered to be adequate. The nature of the chemical must be noted and reported to the eye doctor.

Household activities which have the potential to injure the eyes include cleaning (chemicals), gardening (leaves, branches, stones) and home-improvement activities (hammer, nails, screws). Wearing eyeglasses for protection during these activities go a long way in preventing most of these injuries. Falling down, particularly prone being small children and elderly seniors, may cause eye injuries by striking the eye against corners of furnitures, taps, etc. While playing with fireworks, eye injuries with exploding pellets are commonly seen during festivals; wearing protective eyeglasses and following standard protective measures for fireworks are a must. When opening corks of bottles under high pressure, the cork should be directed away from the eyes of anyone in the vicinity, and covered with a cloth while opening as a further preventive measure.

Children, particularly small children, are very vulnerable to eye injuries and to permanent damage of eyesight. Several preventive measures help to protect their eyes and vision.
1) Items which should be kept out of their reach include (a) chemicals and sprays, (b) sharp objects like knives, scissors, safety-pin and the like, (c) fireworks, and (d) pets
2) Teaching children how to safely use paper, pencil, pen and other school/study materials
3) Avoiding/covering sharp edges in furnitures, etc
4) Only allowing age-appropriate toys/games
5) Avoiding projectile toys like darts, bow and arrow, and toy-gun
6) Wearing spectacles with polycarbonate lenses when playing contact sports
7) Appropriate use of restrainers, such as seat-belts, in vehicles

A little awareness about eye injury, and taking appropriate preventive and first-aid measures, does help tremendously in protecting the eyes and preserving our eyesight.

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19/05/2022

DIABETIC RETINOPATHY FAQs

Q: I am suffering from diabetes. Why did my physician, who is controlling my diabetes, ask me to get my eyes checked?

A: The main cause of loss of vision, directly due to diabetes, is diabetic retinopathy, which occurs in the retina of the eye. The retina may be considered to be a part of the brain which is inside the eye. Being a part of the brain, it consists of nerve cells in many layers and is situated on the inside of the back part of the eye. Whenever we look at an object, an image of that object is focussed on the retina. The healthy nerve cells of the retina then transmits a signal, corresponding to the image on the retina, to the visual area in the back part of the brain, where the sensation of vision is created. The blood vessels of the retina carry nutrition to the nerve cells of the retina. If the blood vessels of the retina get damaged, then the nerve cells of retina are damaged, and vision gets impaired.

It is precisely these blood vessels of the retina upon which diabetes inflicts damage. Just as diabetes may damage blood vessels of any other part of the body (such as kidney, heart, legs, etc), it also affects the blood vessels of the retina. The two main damaging effects of diabetes on the blood vessels of the retina are (1) the retinal blood vessels becoming leaky, causing accumulation of watery fluid in the retina (called 'edema'), and (2) the retinal blood vessels getting blocked (called 'ischemia'). Both cause loss of vision.

The severity of diabetic retinopathy, a diabetic patient will have, depends mainly on (1) the duration of diabetes, and (2) the extent to which blood sugar (and other related factors like blood pressure, cholesterol, kidney status and hemoglobin) is kept under rigorous control. There is convincing evidence, beyond reasonable doubt, that those patients, in whom these parameters (blood sugar, blood pressure, cholesterol, kidney status and hemoglobin) are not tightly controlled over the long term, have a much higher chance of developing vision-threatening diabetic retinopathy, much earlier than those who have these parameters under rigorous control over the long term.

In the early stage of diabetic retinopathy, vision is not affected, but there are changes in the retina which an eye doctor can identify, and alert the patient and his treating physician for more rigorous control of diabetes. If there is no diabetic retinopathy, the eye doctor usually advises the patient to get his eyes checked once every year.

During these examinations, the eye doctor usually applies an eyedrop to have a better view inside the eye. The examination is usually done 30 minutes after application of the drop. After application of this drop, vision (particularly vision for near) becomes blurred for 4-5 hours. During this time, the patient may have particular difficulty in moving about in bright light. This is why the patient should not himself/herself drive to the clinic and should be accompanied by another person during the visit.

During the examination, if the eye doctor finds edema, he/she usually advises one diagnostic test called OCT. This test shows the presence and the amount of the edema, and also shows the response of the edema to treatment. Another diagnostic test, which is much less commonly performed nowadays after the advent of OCT, is DFA (also called FA or FFA). The current standard of treatment for edema are injections given inside the eye. Multiple injections may be required over several years. A variety of injections are available, and there is a significant difference in cost involved among them.

Although ischemia may be less common than edema in diabetic retinopathy, the damage to vision due to ischemia has a higher chance of being more severe and irreversible. Due to ischemia, blood supply to the area of the retina having ischemia is severely reduced or absent, and consequently the nerve cells die. The dead nerve cells are not replaced by healthy cells, and vision through that area of ischemic retina gets permanently destroyed. In addition, ischemia of large areas of the retina leads to formation of new blood vessels in areas of the retina still having intact blood vessels. These new blood vessels add insult to injury. They may cause severe bleeding (called 'vitreous hemorrhage') inside the eye and/or displacement of the retina (called 'retinal detachment), both of which cause severe loss of vision. If the eye doctor finds only new blood vessels, with or without slight bleeding, he/she usually advises laser treatment of retina, with or without injection to be given inside the eye. The same injections, which are used to treat edema, are given as they also cause these new vessels to become inactive. If there is significant bleeding and/or retinal detachment, the patient is usually advised vitreo-retinal surgery. Both edema and effects of ischemia may co-exist in the same eye, and the patient then requires a combination of treatment accordingly.

Even in these situations, where the patient is undergoing eye treatment for diabetic retinopathy, the other parameters (blood sugar, blood pressure, cholesterol, kidney status and hemoglobin) need to be rigorously kept under control over the long term, so as to reduce further assault of diabetes on the retina.

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