Diabetic retinopathy
Encyclopedia
Diabetic retinopathy is retinopathy
(damage to the retina
) caused by complications of diabetes mellitus
, which can eventually lead to blindness
.
It is an ocular manifestation of systemic disease which affects up to 80% of all patients who have had diabetes for 10 years or more. Despite these intimidating statistics, research indicates that at least 90% of these new cases could be reduced if there was proper and vigilant treatment and monitoring of the eyes. The longer a person has diabetes, the higher their chances of developing diabetic retinopathy.
, which may cause vision loss more rapidly, may not have any warning signs for some time. In general, however, a person with macular edema is likely to have blurred vision, making it hard to do things like read or drive. In some cases, the vision will get better or worse during the day.
As new blood vessels form at the back of the eye as a part of proliferative diabetic retinopathy (PDR), they can bleed (ocular hemorrhage) and blur vision. The first time this happens, it may not be very severe. In most cases, it will leave just a few specks of blood
, or spots, floating in a person's visual field, though the spots often go away after a few hours.
These spots are often followed within a few days or weeks by a much greater leakage of blood, which blurs vision. In extreme cases, a person will only be able to tell light from dark in that eye. It may take the blood anywhere from a few days to months or even years to clear from the inside of the eye, and in some cases the blood will not clear. These types of large hemorrhages tend to happen more than once, often during sleep
.
On funduscopic exam, a doctor will see cotton wool spots
, flame hemorrhages (similar lesions are also caused by the alpha-toxin of Clostridium novyi
), and dot-blot hemorrhages.
Elevation of blood-glucose levels can also cause edema (swelling) of the crystalline lens (hyperphacosorbitomyopicosis
) as a result of sorbitol
(sugar alcohol
) accumulating in the lens. This edema often causes temporary myopia
(nearsightedness). A common sign of hyperphacosorbitomyopicosis is blurring of distance vision while near vision remains adequate.
-induced intramural pericyte
death and thickening of the basement membrane
lead to incompetence of the vascular walls. These damages change the formation of the blood-retinal barrier
and also make the retinal blood vessels become more permeable.
The pericyte death is caused when "hyperglycemia persistently activates protein kinase C-δ (PKC-δ, encoded by Prkcd) and p38 mitogen-activated protein kinase
(MAPK) to increase the expression of a previously unknown target of PKC-δ signaling, Src homology-2 domain–containing phosphatase-1 (SHP-1), a protein tyrosine phosphatase. This signaling cascade leads to PDGF receptor- dephosphorylation and a reduction in downstream signaling from this receptor, resulting in pericyte apoptosis…"
Small blood vessel
s – such as those in the eye – are especially vulnerable to poor blood sugar
(blood glucose) control. An overaccumulation of glucose
and/or fructose
damages the tiny blood vessels in the retina. During the initial stage, called nonproliferative diabetic retinopathy (NPDR), most people do not notice any change in their vision. Early changes that are reversible and do not threaten central vision are sometimes termed simplex retinopathy or background retinopathy.
Some people develop a condition called macular edema
. It occurs when the damaged blood vessels leak fluid and lipid
s onto the macula
, the part of the retina that lets us see detail. The fluid makes the macula swell, which blurs vision.
As the disease progresses, severe nonproliferative diabetic retinopathy enters an advanced, or proliferative, stage when blood vessels proliferate (i.e. grow). The lack of oxygen
in the retina causes fragile, new, blood vessels to grow along the retina and in the clear, gel-like vitreous humour
that fills the inside of the eye. Without timely treatment, these new blood vessels can bleed, cloud vision, and destroy the retina. Fibrovascular proliferation can also cause tractional retinal detachment
. The new blood vessels can also grow into the angle of the anterior chamber of the eye and cause neovascular glaucoma.
Nonproliferative diabetic retinopathy shows up as cotton wool spots
, or microvascular abnormalities or as superficial retinal hemorrhages. Even so, the advanced proliferative diabetic retinopathy (PDR) can remain asymptomatic
for a very long time, and so should be monitored closely with regular checkups.
Prior studies had also assumed a clear glycemic threshold between people at high and low risk of diabetic retinopathy. However, it has been shown that the widely accepted WHO and American Diabetes Association diagnostic cutoff for diabetes of a fasting plasma glucose ≥ 7.0 mmol/l (126 mg/dl) does not accurately identify diabetic retinopathy among patients. The cohort study
included a multi-ethnic, cross-sectional adult population sample in the US, as well as two cross-sectional adult populations in Australia. For the US-based component of the study, the sensitivity was 34.7% and specificity was 86.6%. For patients at similar risk to those in this study (15.8% had diabetic retinopathy), this leads to a positive predictive value
of 32.7% and negative predictive value
of 87.6%.
Published rates vary between trials, the proposed explanation being differences in study methods and reporting of prevalence
rather than incidence
values.
During pregnancy
, diabetic retinopathy may also be a problem for women with diabetes.
It is recommended that all pregnant women with diabetes have dilated eye examination
s each trimester to protect their vision.
People with Down's syndrome, who have three copies of chromosome 21, almost never acquire diabetic retinopathy. This protection appears to be due to the elevated levels of endostatin
, an anti-angiogenic protein, derived from collagen XVIII. The collagen XVIII gene is located on chromosome 21.
that includes:
The eye care professional will look at the retina for early signs of the disease, such as: (1) leaking blood vessels, (2) retinal swelling, such as macular edema, (3) pale, fatty deposits on the retina (exudates) signs of leaking blood vessels, (4) damaged nerve
tissue (neuropathy), and (5) any changes in the blood vessels.
Should the doctor suspect macular edema
, he or she may perform a test called fluorescein angiography
. In this test, a special dye
is injected into the arm
. Pictures are then taken as the dye passes through the blood vessels in the retina. This test allows the doctor to find the leaking blood vessels.
into the eye, and vitrectomy
.
Although these treatments are very successful (in slowing or stopping further vision loss), they do not cure diabetic retinopathy. Caution should be exercised in treatment with laser surgery since it causes a loss of retinal tissue. It is often more prudent to inject triamcinolone. In some patients it results in a marked increase of vision, especially if there is an edema of the macula
.
Avoiding tobacco use and correction of associated hypertension are important therapeutic measures in the management of diabetic retinopathy.
The best way of addressing diabetic retinopathy is to monitor it vigilantly and achieve euglycemia.
Since 2008 there have been other drugs (e.g. kinase inhibitors and anti-VEGF
) available.
can be used in two scenarios for the treatment of diabetic retinopathy. It is widely used for early stages of proliferative retinopathy.
.
In treating advanced diabetic retinopathy, the burns are used to destroy the abnormal blood vessels that form in the retina. This has been shown to reduce the risk of severe vision loss for eyes at risk by 50%.<
Before using the laser, the ophthalmologist dilates the pupil and applies anesthetic drops to numb the eye. In some cases, the doctor also may numb the area behind the eye to reduce discomfort. The patient sits facing the laser machine while the doctor holds a special lens on the eye. The physician can use a single spot laser or a pattern scan laser for two dimensional patterns such as squares, rings and arcs. During the procedure, the patient will see flashes of light. These flashes oftentimes create an uncomfortable stinging sensation for the patient. After the laser treatment, patients should be advised not to drive for a few hours while the pupils are still dilated. Vision will most likely remain blurry for the rest of the day. Though there should not be much pain in the eye itself, an ice cream headache like pain may last for hours afterwards.
Patients will lose some of their peripheral vision after this surgery although it may be barely noticeable by the patient. The procedure does however save the center of the patient's sight. Laser surgery may also slightly reduce colour and night vision.
A person with proliferative retinopathy will always be at risk for new bleeding, as well as glaucoma
, a complication from the new blood vessels. This means that multiple treatments may be required to protect vision.
to restore vision. A vitrectomy is performed when there is a lot of blood in the vitreous
. It involves removing the cloudy vitreous and replacing it with a saline solution.
Studies show that people who have a vitrectomy soon after a large hemorrhage are more likely to protect their vision than someone who waits to have the operation. Early vitrectomy is especially effective in people with insulin-dependent diabetes, who may be at greater risk of blindness from a hemorrhage into the eye.
Vitrectomy is often done under local anesthesia
. The doctor makes a tiny incision in the sclera
, or white of the eye. Next, a small instrument is placed into the eye to remove the vitreous and insert the saline solution into the eye.
Patients may be able to return home soon after the vitrectomy, or may be asked to stay in the hospital
overnight. After the operation, the eye will be red
and sensitive, and patients usually need to wear an eyepatch for a few days or weeks to protect the eye. Medicated eye drops are also prescribed to protect against infection
.
has shown promising results in treatment of diabetic complications incidental to vascular degeneration. Once thought to be a useless byproduct of insulin production, it helps to ameliorate and reverse many symptoms of diabetes.
Retinopathy
Retinopathy is a general term that refers to some form of non-inflammatory damage to the retina of the eye. Frequently, retinopathy is an ocular manifestation of systemic disease.-Pathophysiology:Causes of retinopathy are varied:...
(damage to the retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
) caused by complications of diabetes mellitus
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
, which can eventually lead to blindness
Blindness
Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...
.
It is an ocular manifestation of systemic disease which affects up to 80% of all patients who have had diabetes for 10 years or more. Despite these intimidating statistics, research indicates that at least 90% of these new cases could be reduced if there was proper and vigilant treatment and monitoring of the eyes. The longer a person has diabetes, the higher their chances of developing diabetic retinopathy.
Signs and symptoms
Diabetic retinopathy often has no early warning signs. Even macular edemaMacular edema
Macular edema occurs when fluid and protein deposits collect on or under the macula of the eye and causes it to thicken and swell. The swelling may distort a person's central vision, as the macula is near the center of the retina at the back of the eyeball...
, which may cause vision loss more rapidly, may not have any warning signs for some time. In general, however, a person with macular edema is likely to have blurred vision, making it hard to do things like read or drive. In some cases, the vision will get better or worse during the day.
As new blood vessels form at the back of the eye as a part of proliferative diabetic retinopathy (PDR), they can bleed (ocular hemorrhage) and blur vision. The first time this happens, it may not be very severe. In most cases, it will leave just a few specks of blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
, or spots, floating in a person's visual field, though the spots often go away after a few hours.
These spots are often followed within a few days or weeks by a much greater leakage of blood, which blurs vision. In extreme cases, a person will only be able to tell light from dark in that eye. It may take the blood anywhere from a few days to months or even years to clear from the inside of the eye, and in some cases the blood will not clear. These types of large hemorrhages tend to happen more than once, often during sleep
Sleep
Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...
.
On funduscopic exam, a doctor will see cotton wool spots
Cotton wool spots
Cotton wool spots are an abnormal finding on funduscopic exam of the retina of the eye. They appear as puffy white patches on the retina. They are caused by damage to nerve fibers. The nerve fibers are damaged by swelling in the surface layer of the retina...
, flame hemorrhages (similar lesions are also caused by the alpha-toxin of Clostridium novyi
Clostridium novyi
Clostridium novyi a Gram-positive, endospore- forming, obligate anaerobic bacteria of the class clostridia. It is ubiquitous, being found in the soil and faeces. It is pathogenic, causing a wide variety of diseases in man and animals. It comes in three types, labelled A, B, and a non-pathogenic...
), and dot-blot hemorrhages.
Elevation of blood-glucose levels can also cause edema (swelling) of the crystalline lens (hyperphacosorbitomyopicosis
Hyperphacosorbitomyopicosis
Hyperphacosorbitomyopicosis is an edema of the crystalline lens in the eye commonly resulting in a myopia, or near-sightedness. This edema is caused by the accumulation of sorbitol, a sugar alcohol. This may occur when blood glucose levels are above normal, such as in diabetes mellitus....
) as a result of sorbitol
Sorbitol
Sorbitol, also known as glucitol, Sorbogem® and Sorbo®, is a sugar alcohol that the human body metabolizes slowly. It can be obtained by reduction of glucose, changing the aldehyde group to a hydroxyl group. Sorbitol is found in apples, pears, peaches, and prunes...
(sugar alcohol
Sugar alcohol
A sugar alcohol is a hydrogenated form of carbohydrate, whose carbonyl group has been reduced to a primary or secondary hydroxyl group . Sugar alcohols have the general formula Hn+1H, whereas sugars have HnHCO...
) accumulating in the lens. This edema often causes temporary myopia
Myopia
Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...
(nearsightedness). A common sign of hyperphacosorbitomyopicosis is blurring of distance vision while near vision remains adequate.
Pathogenesis
Diabetic retinopathy is the result of microvascular retinal changes. HyperglycemiaHyperglycemia
Hyperglycemia or Hyperglycæmia, or high blood sugar, is a condition in which an excessive amount of glucose circulates in the blood plasma. This is generally a glucose level higher than 13.5mmol/l , but symptoms may not start to become noticeable until even higher values such as 15-20 mmol/l...
-induced intramural pericyte
Pericyte
A pericyte is a type of cell found in the central nervous system. These cells play an integral role in the maintenance of the blood brain barrier as well as several other homeostatic and hemostatic functions of the brain. Pericytes are also a key component of the neurovascular unit, which also...
death and thickening of the basement membrane
Basement membrane
The basement membrane is a thin sheet of fibers that underlies the epithelium, which lines the cavities and surfaces of organs including skin, or the endothelium, which lines the interior surface of blood vessels.- Composition :...
lead to incompetence of the vascular walls. These damages change the formation of the blood-retinal barrier
Blood-retinal barrier
The blood–retinal barrier, or the BRB, is part of the blood–ocular barrier that consists of cells that are joined tightly together to prevent certain substances from entering the tissue of the retina...
and also make the retinal blood vessels become more permeable.
The pericyte death is caused when "hyperglycemia persistently activates protein kinase C-δ (PKC-δ, encoded by Prkcd) and p38 mitogen-activated protein kinase
Mitogen-activated protein kinase
Mitogen-activated protein kinases are serine/threonine-specific protein kinases that respond to extracellular stimuli and regulate various cellular activities, such as gene expression, mitosis, differentiation, proliferation, and cell survival/apoptosis.-Activation:MAP kinases are activated...
(MAPK) to increase the expression of a previously unknown target of PKC-δ signaling, Src homology-2 domain–containing phosphatase-1 (SHP-1), a protein tyrosine phosphatase. This signaling cascade leads to PDGF receptor- dephosphorylation and a reduction in downstream signaling from this receptor, resulting in pericyte apoptosis…"
Small blood vessel
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
s – such as those in the eye – are especially vulnerable to poor blood sugar
Blood sugar
The blood sugar concentration or blood glucose level is the amount of glucose present in the blood of a human or animal. Normally in mammals, the body maintains the blood glucose level at a reference range between about 3.6 and 5.8 mM , or 64.8 and 104.4 mg/dL...
(blood glucose) control. An overaccumulation of glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
and/or fructose
Fructose
Fructose, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847...
damages the tiny blood vessels in the retina. During the initial stage, called nonproliferative diabetic retinopathy (NPDR), most people do not notice any change in their vision. Early changes that are reversible and do not threaten central vision are sometimes termed simplex retinopathy or background retinopathy.
Some people develop a condition called macular edema
Macular edema
Macular edema occurs when fluid and protein deposits collect on or under the macula of the eye and causes it to thicken and swell. The swelling may distort a person's central vision, as the macula is near the center of the retina at the back of the eyeball...
. It occurs when the damaged blood vessels leak fluid and lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
s onto the macula
Macula
The macula or macula lutea is an oval-shaped highly pigmented yellow spot near the center of the retina of the human eye. It has a diameter of around 5 mm and is often histologically defined as having two or more layers of ganglion cells...
, the part of the retina that lets us see detail. The fluid makes the macula swell, which blurs vision.
Proliferative diabetic retinopathy (PDR)(or PDRP)
As the disease progresses, severe nonproliferative diabetic retinopathy enters an advanced, or proliferative, stage when blood vessels proliferate (i.e. grow). The lack of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
in the retina causes fragile, new, blood vessels to grow along the retina and in the clear, gel-like vitreous humour
Vitreous humour
The vitreous humour or vitreous humor is the clear gel that fills the space between the lens and the retina of the eyeball of humans and other vertebrates...
that fills the inside of the eye. Without timely treatment, these new blood vessels can bleed, cloud vision, and destroy the retina. Fibrovascular proliferation can also cause tractional retinal detachment
Retinal detachment
Retinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency.The retina is a...
. The new blood vessels can also grow into the angle of the anterior chamber of the eye and cause neovascular glaucoma.
Nonproliferative diabetic retinopathy shows up as cotton wool spots
Cotton wool spots
Cotton wool spots are an abnormal finding on funduscopic exam of the retina of the eye. They appear as puffy white patches on the retina. They are caused by damage to nerve fibers. The nerve fibers are damaged by swelling in the surface layer of the retina...
, or microvascular abnormalities or as superficial retinal hemorrhages. Even so, the advanced proliferative diabetic retinopathy (PDR) can remain asymptomatic
Asymptomatic
In medicine, a disease is considered asymptomatic if a patient is a carrier for a disease or infection but experiences no symptoms. A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated. Asymptomatic infections are also called subclinical...
for a very long time, and so should be monitored closely with regular checkups.
Risk factors
All people with diabetes mellitus are at risk those with Type I diabetes (juvenile onset) and those with Type II diabetes (adult onset). The longer a person has diabetes, the higher the risk of developing some ocular problem. Between 40 to 45 percent of Americans diagnosed with diabetes have some stage of diabetic retinopathy. After 20 years of diabetes, nearly all patients with Type I diabetes and >60% of patients with Type II diabetes have some degree of retinopathy; however, these statistics were published in 2002 using data from four years earlier.Prior studies had also assumed a clear glycemic threshold between people at high and low risk of diabetic retinopathy. However, it has been shown that the widely accepted WHO and American Diabetes Association diagnostic cutoff for diabetes of a fasting plasma glucose ≥ 7.0 mmol/l (126 mg/dl) does not accurately identify diabetic retinopathy among patients. The cohort study
Cohort study
A cohort study or panel study is a form of longitudinal study used in medicine, social science, actuarial science, and ecology. It is an analysis of risk factors and follows a group of people who do not have the disease, and uses correlations to determine the absolute risk of subject contraction...
included a multi-ethnic, cross-sectional adult population sample in the US, as well as two cross-sectional adult populations in Australia. For the US-based component of the study, the sensitivity was 34.7% and specificity was 86.6%. For patients at similar risk to those in this study (15.8% had diabetic retinopathy), this leads to a positive predictive value
Positive predictive value
In statistics and diagnostic testing, the positive predictive value, or precision rate is the proportion of subjects with positive test results who are correctly diagnosed. It is a critical measure of the performance of a diagnostic method, as it reflects the probability that a positive test...
of 32.7% and negative predictive value
Negative predictive value
In statistics and diagnostic testing, the negative predictive value is a summary statistic used to describe the performance of a diagnostic testing procedure. It is defined as the proportion of subjects with a negative test result who are correctly diagnosed. A high NPV means that when the test...
of 87.6%.
Published rates vary between trials, the proposed explanation being differences in study methods and reporting of prevalence
Prevalence
In epidemiology, the prevalence of a health-related state in a statistical population is defined as the total number of cases of the risk factor in the population at a given time, or the total number of cases in the population, divided by the number of individuals in the population...
rather than incidence
Incidence (epidemiology)
Incidence is a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate with a denominator.Incidence proportion is the...
values.
During pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
, diabetic retinopathy may also be a problem for women with diabetes.
It is recommended that all pregnant women with diabetes have dilated eye examination
Eye examination
An eye examination is a battery of tests performed by an ophthalmologist, optometrist, or orthoptist assessing vision and ability to focus on and discern objects, as well as other tests and examinations pertaining to the eyes....
s each trimester to protect their vision.
People with Down's syndrome, who have three copies of chromosome 21, almost never acquire diabetic retinopathy. This protection appears to be due to the elevated levels of endostatin
Endostatin
]Endostatin is a naturally-occurring 20-kDa C-terminal fragment derived from type XVIII collagen. It is reported to serve as an anti-angiogenic agent, similar to angiostatin and thrombospondin....
, an anti-angiogenic protein, derived from collagen XVIII. The collagen XVIII gene is located on chromosome 21.
Diagnosis
Diabetic retinopathy is detected during an eye examinationEye examination
An eye examination is a battery of tests performed by an ophthalmologist, optometrist, or orthoptist assessing vision and ability to focus on and discern objects, as well as other tests and examinations pertaining to the eyes....
that includes:
- Visual acuity test: This test uses an eye chartEye chartAn eye chart is a chart used to measure visual acuity. Types of eye charts include the logMAR chart, Snellen chart, Landolt C, and the Lea test.-Procedure:Charts usually display several rows of optotypes , each row in a different size...
to measure how well a person sees at various distances (i.e., visual acuityVisual acuityVisual acuity is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain....
). - Pupil dilation: The eye care professional places drops into the eye to widen the pupilPupilThe pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. It appears black because most of the light entering the pupil is absorbed by the tissues inside the eye. In humans the pupil is round, but other species, such as some cats, have slit pupils. In...
. This allows him or her to see more of the retina and look for signs of diabetic retinopathy. After the examination, close-up vision may remain blurred for several hours. - OphthalmoscopyOphthalmoscopyOphthalmoscopy is a test that allows a health professional to see inside the fundus of the eye and other structures using an ophthalmoscope . It is done as part of an eye examination and may be done as part of a routine physical examination...
: This is an examination of the retina in which the eye care professional: (1) looks through a device with a special magnifying lens that provides a narrow view of the retina, or (2) wearing a headset with a bright light, looks through a special magnifying glass and gains a wide view of the retina. Note that hand-held ophthalmoscopy is insufficient to rule out significant and treatable diabetic retinopathy. - Optical coherence tomographyOptical coherence tomographyOptical coherence tomography is an optical signal acquisition and processing method. It captures micrometer-resolution, three-dimensional images from within optical scattering media . Optical coherence tomography is an interferometric technique, typically employing near-infrared light...
(OCT): This is an optical imaging modality based upon interference, and analogous to ultrasound. It produces cross-sectional images of the retina (B-scans) which can be used to measure the thickness of the retina and to resolve its major layers, allowing the observation of swelling and or leakage. - Digital Retinal Screening Programs: Systematic programs for the early detection of eye disease including diabetic retinopathy are becoming more common, such as in the UK, where all people with diabetes mellitusDiabetes mellitusDiabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
are offered retinal screening at least annually. This involves digital image capture and transmission of the images to a digital reading center for evaluation and treatment referral. See Vanderbilt Ophthalmic Imaging Center http://www.retinopathyscreening.org/ and the English National Screening Programme for Diabetic Retinopathy http://www.nscretinopathy.org.uk/ - Slit Lamp Biomicroscopy Retinal Screening Programs: Systematic programs for the early detection of diabetic retinopathy using slit-lamp biomicroscopy. These exist either as a standalone scheme or as part of the Digital program (above) where the digital photograph was considered to lack enough clarity for detection and/or diagnosis of any retinal abnormality.
The eye care professional will look at the retina for early signs of the disease, such as: (1) leaking blood vessels, (2) retinal swelling, such as macular edema, (3) pale, fatty deposits on the retina (exudates) signs of leaking blood vessels, (4) damaged nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
tissue (neuropathy), and (5) any changes in the blood vessels.
Should the doctor suspect macular edema
Macular edema
Macular edema occurs when fluid and protein deposits collect on or under the macula of the eye and causes it to thicken and swell. The swelling may distort a person's central vision, as the macula is near the center of the retina at the back of the eyeball...
, he or she may perform a test called fluorescein angiography
Fluorescein angiography
Intravenous Fluorescein angiography or fluorescent angiography is a technique for examining the circulation of the retina using the dye tracing method...
. In this test, a special dye
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....
is injected into the arm
Arm
In human anatomy, the arm is the part of the upper limb between the shoulder and the elbow joints. In other animals, the term arm can also be used for analogous structures, such as one of the paired forelimbs of a four-legged animal or the arms of cephalopods...
. Pictures are then taken as the dye passes through the blood vessels in the retina. This test allows the doctor to find the leaking blood vessels.
Management
There are three major treatments for diabetic retinopathy, which are very effective in reducing vision loss from this disease. In fact, even people with advanced retinopathy have a 90 percent chance of keeping their vision when they get treatment before the retina is severely damaged. These three treatments are laser surgery, injection of triamcinoloneTriamcinolone
Triamcinolone is a long-acting synthetic corticosteroid given orally, by injection, inhalation, or as a topical ointment or cream....
into the eye, and vitrectomy
Vitrectomy
Vitrectomy is a surgery to remove some or all of the vitreous humor from the eye. Anterior vitrectomy entails removing small portions of the vitreous from the front structures of the eye—often because these are tangled in an intraocular lens or other structures...
.
Although these treatments are very successful (in slowing or stopping further vision loss), they do not cure diabetic retinopathy. Caution should be exercised in treatment with laser surgery since it causes a loss of retinal tissue. It is often more prudent to inject triamcinolone. In some patients it results in a marked increase of vision, especially if there is an edema of the macula
Macular edema
Macular edema occurs when fluid and protein deposits collect on or under the macula of the eye and causes it to thicken and swell. The swelling may distort a person's central vision, as the macula is near the center of the retina at the back of the eyeball...
.
Avoiding tobacco use and correction of associated hypertension are important therapeutic measures in the management of diabetic retinopathy.
The best way of addressing diabetic retinopathy is to monitor it vigilantly and achieve euglycemia.
Since 2008 there have been other drugs (e.g. kinase inhibitors and anti-VEGF
Vascular endothelial growth factor
Vascular endothelial growth factor is a signal protein produced by cells that stimulates vasculogenesis and angiogenesis. It is part of the system that restores the oxygen supply to tissues when blood circulation is inadequate....
) available.
Laser photocoagulation
Laser photocoagulationLaser photocoagulation
Laser coagulation or laser photocoagulation surgery is used to treat a number of eye diseases and has become widely used in recent decades...
can be used in two scenarios for the treatment of diabetic retinopathy. It is widely used for early stages of proliferative retinopathy.
Panretinal photocoagulation
Panretinal photocoagulation, or PRP (also called scatter laser treatment), is used to treat proliferative diabetic retinopathy (PDR). The goal is to create 1,600 - 2,000 burns in the retina with the hope of reducing the retina's oxygen demand, and hence the possibility of ischemiaIschemia
In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...
.
In treating advanced diabetic retinopathy, the burns are used to destroy the abnormal blood vessels that form in the retina. This has been shown to reduce the risk of severe vision loss for eyes at risk by 50%.<
Before using the laser, the ophthalmologist dilates the pupil and applies anesthetic drops to numb the eye. In some cases, the doctor also may numb the area behind the eye to reduce discomfort. The patient sits facing the laser machine while the doctor holds a special lens on the eye. The physician can use a single spot laser or a pattern scan laser for two dimensional patterns such as squares, rings and arcs. During the procedure, the patient will see flashes of light. These flashes oftentimes create an uncomfortable stinging sensation for the patient. After the laser treatment, patients should be advised not to drive for a few hours while the pupils are still dilated. Vision will most likely remain blurry for the rest of the day. Though there should not be much pain in the eye itself, an ice cream headache like pain may last for hours afterwards.
Patients will lose some of their peripheral vision after this surgery although it may be barely noticeable by the patient. The procedure does however save the center of the patient's sight. Laser surgery may also slightly reduce colour and night vision.
A person with proliferative retinopathy will always be at risk for new bleeding, as well as glaucoma
Glaucoma
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...
, a complication from the new blood vessels. This means that multiple treatments may be required to protect vision.
Intravitreal triamcinolone acetonide
Triamcinolone is a long acting steroid preparation. When injected in the vitreous cavity, it decreases the macular edema (thickening of the retina at the macula) caused due to diabetic maculopathy, and results in an increase in visual acuity. The effect of triamcinolone is transient, lasting up to three months, which necessitates repeated injections for maintaining the beneficial effect. Complications of intravitreal injection of triamcinolone include cataract, steroid-induced glaucoma and endophthalmitis.Vitrectomy
Instead of laser surgery, some people require a vitrectomyVitrectomy
Vitrectomy is a surgery to remove some or all of the vitreous humor from the eye. Anterior vitrectomy entails removing small portions of the vitreous from the front structures of the eye—often because these are tangled in an intraocular lens or other structures...
to restore vision. A vitrectomy is performed when there is a lot of blood in the vitreous
Vitreous humour
The vitreous humour or vitreous humor is the clear gel that fills the space between the lens and the retina of the eyeball of humans and other vertebrates...
. It involves removing the cloudy vitreous and replacing it with a saline solution.
Studies show that people who have a vitrectomy soon after a large hemorrhage are more likely to protect their vision than someone who waits to have the operation. Early vitrectomy is especially effective in people with insulin-dependent diabetes, who may be at greater risk of blindness from a hemorrhage into the eye.
Vitrectomy is often done under local anesthesia
Local anesthesia
Local anesthesia is any technique to induce the absence of sensation in part of the body, generally for the aim of inducing local analgesia, that is, local insensitivity to pain, although other local senses may be affected as well. It allows patients to undergo surgical and dental procedures with...
. The doctor makes a tiny incision in the sclera
Sclera
The sclera , also known as the white or white of the eye, is the opaque , fibrous, protective, outer layer of the eye containing collagen and elastic fiber. In the development of the embryo, the sclera is derived from the neural crest...
, or white of the eye. Next, a small instrument is placed into the eye to remove the vitreous and insert the saline solution into the eye.
Patients may be able to return home soon after the vitrectomy, or may be asked to stay in the hospital
Hospital
A hospital is a health care institution providing patient treatment by specialized staff and equipment. Hospitals often, but not always, provide for inpatient care or longer-term patient stays....
overnight. After the operation, the eye will be red
Red
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...
and sensitive, and patients usually need to wear an eyepatch for a few days or weeks to protect the eye. Medicated eye drops are also prescribed to protect against infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
.
C-peptide
Though not yet commercially available, c-peptideC-peptide
C-peptide is a protein that is produced in the body along with insulin. First preproinsulin is secreted with an A-chain, C-peptide, a B-chain, and a signal sequence. The signal sequence is cut off, leaving proinsulin...
has shown promising results in treatment of diabetic complications incidental to vascular degeneration. Once thought to be a useless byproduct of insulin production, it helps to ameliorate and reverse many symptoms of diabetes.
Pine bark extract
A pine bark extract of oligomeric proanthocyanidins has been shown to improve microcirculation, retinal edema and visual acuity in the early stages of diabetic retinopathy.External links
- Diabetic Retinopathy Resource Guide from the National Eye Institute (NEI).
- National Diabetes Information Clearinghouse
- English National Screening Programme for Diabetic Retinopathy