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MICROVASCULAR COMPLICATIONS AND DIABETIC RETINOPATHY
Although macrovascular atherosclerotic changes are seen in both diabetic and nondiabetic patients, the microvascular changes are unique to diabetes. Diabetic microvascular disease (or micro-angiopathy) is characterized by capillary basement membrane thickening. The basement membrane surrounds the endothelial cells of the capillary. Researchers believe that increased blood glu-cose levels react through a series of biochemical responses to thicken the basement membrane to several times its normal thickness. Two areas affected by these changes are the retina and the kidneys. Diabetic retinopathy is the leading cause of blindness in people between 20 and 74 years of age in the United States; it occurs in both type 1 and type 2 diabetes (ADA, Diabetic Retinopathy, 2003). Similarly, about one in every four individu-als starting dialysis has diabetic nephropathy.
People with diabetes are subject to multiple visual complica-tions (Table 41-9). The eye pathology referred to as diabetic retinopathy is caused by changes in the small blood vessels in the retina, the area of the eye that receives images and sends infor-mation about the images to the brain (Fig. 41-9). It is richly sup-plied with blood vessels of all kinds: small arteries and veins, arterioles, venules, and capillaries. There are three main stages of retinopathy: nonproliferative (background) retinopathy, prepro-liferative retinopathy, and proliferative retinopathy.
Nearly all patients with type 1 diabetes and more than 60% of patients with type 2 diabetes have some degree of retinopathy after 20 years (ADA, Diabetic Retinopathy, 2003). Changes in the microvasculature include microaneurysms, intraretinal hem-orrhage, hard exudates, and focal capillary closure. Although most patients do not develop visual impairment, it can be devas-tating if it occurs. A complication of nonproliferative retinopa-thy, macular edema, occurs in approximately 10% of people with type 1 and type 2 diabetes and may lead to visual distortion and loss of central vision.
An advanced form of background retinopathy, preprolifera-tive retinopathy, is considered a precursor to the more serious proliferative retinopathy. In preproliferative retinopathy, there are more widespread vascular changes and loss of nerve fibers.
Epidemiologic evidence suggests that 10% to 50% of patients with preproliferative retinopathy will develop proliferative retinopathy within a short time (possibly as little as 1 year). As with back-ground retinopathy, if visual changes occur during the preprolif-erative stage, they are usually caused by macular edema.
Proliferative retinopathy represents the greatest threat to vision. Proliferative retinopathy is characterized by the prolifera-tion of new blood vessels growing from the retina into the vitreous. These new vessels are prone to bleeding. The visual loss associated with proliferative retinopathy is caused by this vitreous hemorrhage and/or retinal detachment. The vitreous is normally clear, allowing light to be transmitted to the retina. When there is a hemorrhage, the vitreous becomes clouded and cannot trans-mit light, resulting in loss of vision. Another consequence of vit-reous hemorrhage is that resorption of the blood in the vitreous leads to the formation of fibrous scar tissue. This scar tissue may place traction on the retina, resulting in retinal detachment and subsequent visual loss.
Retinopathy is a painless process. In nonproliferative and pre-proliferative retinopathy, blurry vision secondary to macular edema occurs in some patients, although many patients are asymp-tomatic. Even patients with a significant degree of proliferative retinopathy and some hemorrhaging may not experience major visual changes. However, symptoms indicative of hemorrhaging include floaters or cobwebs in the visual field, or sudden visual changes including spotty or hazy vision, or complete loss of vision.
Diagnosis is by direct visualization with an ophthalmoscope or with a technique known as fluorescein angiography. Fluorescein angiography can document the type and activity of the retinopa-thy. Dye is injected into an arm vein and is carried to various parts of the body through the blood, but especially through the vessels of the retina of the eye. This technique allows the ophthalmolo-gist, using special instruments, to see the retinal vessels in bright detail and gives useful information that cannot be obtained with just an ophthalmoscope.
Side effects of this diagnostic procedure may include nausea during the dye injection; yellowish, fluorescent discoloration ofthe skin and urine lasting 12 to 24 hours; and occasional allergic reactions, usually manifested by hives or itching. Generally, how-ever, it is a safe diagnostic procedure. Patient preparation includes explaining:
· The steps of the procedure
· The fact that the procedure is painless
· The potential side effects
· The type of information the technique can provide
· That the flash of the camera may be slightly uncomfortable for a short time
The first focus of management is on primary and secondary pre-vention. The results of the DCCT study demonstrated that maintenance of blood glucose to a normal or near-normal level in type 1 diabetes through intensive insulin therapy and patient education decreased the risk for development of retinopathy by 76% when compared with conventional therapy in patients with-out preexisting retinopathy. The progression of retinopathy was decreased by 54% in patients with very mild to moderate non-proliferative retinopathy at the time of initiation of treatment. Similarly, the UKPDS study demonstrated a reduced risk of retinopathy in type 2 diabetes with better control of blood glu-cose levels (ADA, Diabetic Retinopathy, 2003).
For advanced cases, the main treatment of diabetic retinopa-thy is argon laser photocoagulation. The laser treatment destroys leaking blood vessels and areas of neovascularization. For patients at increased risk for hemorrhaging, panretinal photocoagulation may significantly reduce the rate of progression to blindness. Pan-retinal photocoagulation involves the systematic application of multiple (more than 1,000) laser burns throughout the retina (ex-cept in the macular region). This stops the widespread growth of new vessels and hemorrhaging of damaged vessels. The role of “mild” panretinal photocoagulation (with only a third to a half as many laser burns) in the early stages of proliferative retinopa-thy or in patients with preproliferative changes is being investi-gated. For macular edema, focal photocoagulation is used to apply smaller laser burns to specific areas of microaneurysms in the macular region. This may reduce the rate of visual loss from macular edema by 50% (ADA, Diabetic Retinopathy, 2003).
Photocoagulation treatments are usually performed on an out-patient basis, and most patients can return to their usual activi-ties by the next day. For some patients, limitations may be placed on activities involving weight bearing or bearing down. For most patients, the treatment does not cause intense pain, although they may report varying degrees of discomfort. Usually an anesthetic eye drop is all that is needed during the treatment. A few patients may experience slight visual loss, loss of peripheral vision, or im-pairments in adaptation to the dark. For most patients, however, the risk of slight visual changes from the laser treatment itself is much less than the potential for loss of vision from progression of retinopathy.
When a major hemorrhage into the vitreous occurs, the vitre-ous fluid becomes mixed with blood and prevents light from pass-ing through the eye; this can cause blindness. A vitrectomy is a surgical procedure in which vitreous humor filled with blood or fibrous tissue is removed with a special drill-like instrument and replaced with saline or another liquid. A vitrectomy is performed on patients who already have visual loss and in whom the vitre-ous hemorrhage has not cleared on its own after 6 months. The purpose is to restore useful vision; recovery to near-normal vision is not usually expected. Other strategies that may slow the pro-gression of diabetic retinopathy include:
· Control of hypertension
· Control of blood glucose
· Cessation of smoking
Nursing management of patients with diabetic retinopathy or other eye disorders involves implementing the individual plan of care and providing patient education. Education focuses on pre-vention through regular ophthalmologic examinations and blood glucose control and self-management of eye care regimens. The effectiveness of early diagnosis and prompt treatment is empha-sized in teaching the patient and family. If vision loss occurs, nursing care must also address the patient’s adjustment to im-paired vision and use of adaptive devices for diabetes self-care as well as activities of daily living.
In all forms of therapy for retinopa-thy, something is destroyed in the process of saving vision, and the facts must be presented to the patient and family as honestly as possible. The course of the retinopathy may be long and stress-ful. In teaching and counseling the patient, it is important to stress the following:
· Retinopathy may appear after many years of diabetes, and its appearance does not necessarily mean that the diabetes is on a downhill course.
· The odds for maintaining vision are in the patient’s favor, especially with adequate control of glucose levels and blood pressure.
· Frequent eye examinations are the best way to preserve vision, because they allow for the detection of any re-tinopathy.
Some additional points to keep in mind when the patient with diabetes has some type of visual impairment include the following:
· Visual impairment can be a shock. The person’s response to vision loss depends on personality, self-concept, and coping mechanisms.
· As in any loss, acceptance of blindness by the patient occurs in stages; some patients may learn to accept blindness in a rather short period, and others may never do so.
· Although retinopathy occurs bilaterally, the severity may differ in the two eyes.
· Many of the chronic complications of diabetes occur si-multaneously. For example, a patient who is blind due to diabetic retinopathy may also have peripheral neuropathy and may experience impairment of manual dexterity and tactile sensation.
Continuing care for the patient with impairedvision due to diabetic changes depends on the severity of the im-pairment and the effectiveness of the patient’s coping in response to the impairment. The importance of careful diabetes manage-ment is emphasized as one means of slowing the progression of visual changes. The patient is reminded of the need to see the ophthalmologist regularly. If eye changes are progressive and un-relenting, the patient needs to be prepared for inevitable blind-ness. Therefore, consideration is given to making referrals for teaching the patient Braille and for training with a guide dog. Re-ferral to state agencies should be made to ensure that the patient receives services for the blind. Family members are also taught how to assist the patient to remain as independent as possible de-spite decreasing visual acuity.
Referral for home care may be indicated for some patients, particularly those who live alone, those not coping well, and those who have other health problems or complications of diabetes that may interfere with their ability to perform self-care. During home visits, the nurse can assess the patient’s home environment and ability to manage diabetes despite visual impairments.
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