Showing posts with label Surgery. Show all posts
Showing posts with label Surgery. Show all posts

Tuesday, June 2, 2009

Indications for Glaucoma surgery:A Review of Recent Clinical Trials

Glaucoma surgery is indicated when target pressures are not achieved, or when neural tissue or visual function is progressively lost despite maximally tolerated medical and laser therapies.
Target pressure is generally accepted to be the pressure at which progression of glaucomatous
optic neuropathy is unlikely to continue. It is an attempt to prevent progression in a prospective manner. Target pressures need to be re-evaluated periodically and re-set at a
lower level if progression continues.

At the present time, the success of target pressure estimates can only be determined in a retrospective manner after many years of treatment.Recent multi-center, randomized controlled trials have demonstrated the efficacy of lowering intraocular pressure (IOP) in reducing both the risk of developing glaucoma and progression of the disease, and provide some help in choosing the initial target pressure.

Studies clearly show the benefit of IOP reduction in the management of glaucoma and selected patients with ocular hypertension, and help us to set initial target pressures. Lower pressures 12–15 mmHg clearly result in a lower risk of progression,but even reducing IOP by 20% has a protective effect. Advanced disease requires lower pressure when compared with early disease in order to halt or minimize the risk of of progression. It is for this latter group that surgery should be considered sooner than later.

The risk of progression posed by IOP must always be balanced with the risks of treatment. This is especially true when surgery is being considered. There is even some 4 Sit and Trope discussion as to whether patients are being over-treated in the zeal to reach the target pressure, particularly with early glaucoma. It is instructive to consider that the OHTS
found that 90% of untreated ocular hypertensives did not progress over 5 years.

Clearly, however, patients with advanced disease require aggressive therapy. However,not all glaucoma patients require an IOP of 12–14 mmHg. For example, an 85-year-old with a 0.75 cup-to-disc ratio and an IOP of 18 mmHg will likely not go blind from progressive optic neuropathy despite this IOP level. However a 55-year-old with a 0.9 cup-to-disc ratio and the same IOP level with a life expectancy of at least another 20 years is at greater risk of blindness if IOP is not dropped into the low teens. Spaeth has suggested that the goal of treatment is not to prevent disease progression, but to prevent patients from becoming symptomatic or from becoming more symptomatic

Common Misconceptions of Glaucoma


One of the reasons so many patients with glaucoma get worse is that they have serious misunderstandings and misconceptions about it. Here are some of the more common ones.


Misconception #1: People with glaucoma lose peripheral vision.



It is a misconception that patients with glaucoma lose peripheral vision. "Peripheral vision" for most people means vision off to the side. That is, when a person is looking straight ahead, peripheral vision means vision way off to the right side and way off to the left side. But that kind of "side" vision is, in fact, the last part of the vision to be lost in people with glaucoma.



In most people, the initial damage to vision is a mild generalized loss of sensitivity for contrast. The first area of vision that is lost is on the nasal side of the visual field; that is, for example, for the right eye, the earliest visual loss would be just a little bit to the left-hand side of straight-ahead vision. Since this area of vision is also served by the left eye, the loss is not usually noted until most of the field is gone in one eye or a similar area is damaged in both eyes.





Misconception #2: Glaucoma is a well-defined condition.



"Glaucoma" encompasses such a wide variety of different conditions that the word itself is almost meaningless. For example, some patients with glaucoma can become totally blind within a period of a half an hour. Others can be damaged by the glaucomatous process so slowly that even after 20 years, there is still no awareness of any decrease in visual function.



Some types of glaucoma, such as the ordinary "primary open-angle glaucoma" almost always involve both eyes, whereas other types, such as Chandler's syndrome, never involve both eyes.



Some types of glaucoma are so strongly hereditary that 50% of the members of a family are likely to be affected, whereas others have absolutely no familial tendencies at all.



To tell a person that he has "glaucoma" doesn't really tell the person anything meaningful. Rather, the physician should try to explain as carefully as possible what the patient should expect: "You have a condition that has already caused a major amount of damage; if nothing is done, it is likely to get worse over the next three or four years," or: "With your type of glaucoma you probably won't have any discomfort or have any other clues that it's getting worse until the damage is marked. So, you need a glaucoma specialist to monitor your condition."



In short, it is not the glaucoma that is treated, it is the person who needs to be treated, because it is the disease's effect on the person that is the only important consideration.





Misconception #3: People who have glaucoma have to use their drops forever.



It is a misconception that once individuals "start on drops" they must use them for the rest of their lives. However, behind that misconception is a truth that frequently does apply: specifically, that the tendency always to get worse is present in many types of glaucomas and, therefore, vigilance may be necessary for the person's entire life.



In some people, the need for medications to control the intraocular pressure may spontaneously disappear. If drops or other medications need to be continued, it is not because the person is taking the drops that the drops need to be continued. Rather, it is because the underlying problem with the glaucoma continues to exist and some means to manage it continues to be necessary.





Misconception #4: Surgery is appropriate only in desperate cases.



The idea that one starts with weaker drops, progresses to stronger medicine, and only as a last resort becomes a candidate for surgery is another misconception about glaucoma.



This misconception is related to the variety of ways in which glaucoma presents itself. Some types of glaucoma are best treated right from the start with surgery. For example, the commonest type of glaucoma that occurs in infants usually responds well to surgery but never responds adequately to medicines.



On the other hand, with certain types of glaucoma, it is best to avoid surgery, because the risk associated with the surgery is far greater than the potential damage that would occur if the surgery weren't done.





Misconception #5: We can tell whether or not glaucoma is being controlled by monitoring the level of the intraocular pressure.



It is a misconception to think that control of glaucoma is measured in terms of the intraocular pressure. It is true that glaucoma is damage to the tissues of the eye that is at least partially caused by pressure higher than the eye can tolerate.



Nevertheless, people can go blind even though their intraocular pressure is fairly constantly as low as 12 mm Hg, well below the so-called "normal" level of pressure. Others can maintain pressures of 25 mm Hg -- much higher than "normal" -- for many, many years and yet never develop any damage at all.

Control of glaucoma can be defined only in terms of whether or not there is increasing damage. Where the damage is increasing, the glaucoma must be defined as "uncontrolled," regardless of the pressure. Where it is not increasing, the glaucoma must be defined as "controlled," regardless of the pressure.





Misconception #6: What the glaucoma patient does doesn't really make very much difference.



A particularly tragic misconception about glaucoma is that what the patient does doesn't really make very much difference. In fact, how a person manages his or her life is probably the single most important factor determining whether that person maintains his or her sight.



Choosing a competent doctor is an important part of that management, as is helping the doctor do his or her job competently. The patient is really the senior partner and the physician the junior partner. The patient has the responsibility of being alert to how he or she is doing, both from the point of view of general health, quality of life, and visual function, and of passing that information on to the physician. The physician has the responsibility of listening, understanding, and drawing appropriate conclusions.



Patients are responsible for educating themselves, using the physician to help them in that process. The more a patient knows, the better it is.



An important example is patient awareness that general health significantly affects the course of glaucoma damage. For example, to help maintain vision, the overweight person should lose weight and the sedentary person should exercise.



Perhaps the most important thing to understand about glaucoma is that each case is different and that the greatest success in terms of maintenance of quality of life as related to vision occurs when the individual patient really takes responsibility for his or her own well-being and then works with a knowledgeable, competent physicians, who truly listens and truly cares for the person as an individual.