DIABETES MELLITUS DIABETES MELLITUS CHRONIC CHRONIC

COMPLICATIONSCOMPLICATIONS

affect many organ systems affect many organ systems and are responsible for the and are responsible for the majority of morbidity and majority of morbidity and

mortality associated with the mortality associated with the disease.disease.

CHRONIC CHRONIC COMPLICATIONSCOMPLICATIONS

Chronic complications can be Chronic complications can be divided into vascular and divided into vascular and nonvascular complicationsnonvascular complications

vascular complications of vascular complications of DMDM

subdividedsubdivided microvascular (microvascular (retinopathy, retinopathy,

neuropathyneuropathy, nephropathy) , nephropathy) macrovascular complications macrovascular complications

(coronary artery disease, (coronary artery disease, peripheral vascular disease, peripheral vascular disease, cerebrovascular disease)cerebrovascular disease)

Nonvascular complicationsNonvascular complications

include problems such asinclude problems such as:: GastroparesisGastroparesis sexual dysfunctionsexual dysfunction skin changesskin changes

chronic complicationschronic complications

The risk increases The risk increases with thewith the duration of hyperglycemiaduration of hyperglycemia

apparent in the second decade of apparent in the second decade of hyperglycemia. hyperglycemia.

TyType 2 DM may have a long pe 2 DM may have a long asymptomatic period of asymptomatic period of hyperglycemia, many individuals hyperglycemia, many individuals with type 2 DM have complications with type 2 DM have complications at the time of diagnosis. at the time of diagnosis.

chronic complicationschronic complications

Randomized, prospective clinical trials Randomized, prospective clinical trials involving large numbers of individuals involving large numbers of individuals with type 1 or type 2 DM have with type 1 or type 2 DM have conclusively demonstrated that a conclusively demonstrated that a reduction in chronic hyperglycemia reduction in chronic hyperglycemia prevents or reduces retinopathy, prevents or reduces retinopathy, neuropathy, and nephropathy. Other neuropathy, and nephropathy. Other incompletely defined factors also incompletely defined factors also modulate the development of modulate the development of complications. complications.

chronic complicationschronic complications

BeBecause of these observations, it cause of these observations, it is suspected that a genetic is suspected that a genetic susceptibility for developing susceptibility for developing particular complications exists. particular complications exists.

the genetic loci responsible for the genetic loci responsible for these susceptibilities have not yet these susceptibilities have not yet been identified. been identified.

MECHANISMS OF MECHANISMS OF COMPLICATIONSCOMPLICATIONS

Three major theories Three major theories

increased intracellular glucose leads to increased intracellular glucose leads to the formation of advanced glycosylation the formation of advanced glycosylation end products (AGEs) via the end products (AGEs) via the nonenzymatic glycosylaton of cellular nonenzymatic glycosylaton of cellular proteins. Nonenzymatic glycosylation proteins. Nonenzymatic glycosylation results from the interaction of glucose results from the interaction of glucose with amino groups on proteinswith amino groups on proteins

Intracellular glucose is Intracellular glucose is predominantly metabolized by predominantly metabolized by phosphorylation and subsequent phosphorylation and subsequent glycolysis, but when intracellular glycolysis, but when intracellular glucose is increased, some glucose glucose is increased, some glucose is converted to sorbitol by the is converted to sorbitol by the enzyme aldose reductase. enzyme aldose reductase.

Increased sorbitol concentrations Increased sorbitol concentrations affect several aspects of cellular affect several aspects of cellular physiology (decreased myoinositol, physiology (decreased myoinositol, altered redox potential) and may altered redox potential) and may lead to cellular dysfunction.lead to cellular dysfunction.

However, testing of this theory in However, testing of this theory in humans, using aldose reductase humans, using aldose reductase inhibitors, has not demonstrated inhibitors, has not demonstrated beneficial effects on clinical beneficial effects on clinical endpoints of retinopathy, endpoints of retinopathy, neuropathy, or nephropathy.neuropathy, or nephropathy.

third hypothesisthird hypothesis

hyperglycemia increases the formation hyperglycemia increases the formation of diacylglycerol leading to activation of of diacylglycerol leading to activation of certain isoforms of protein kinase C certain isoforms of protein kinase C (PKC)(PKC)..

affect a variety of cellular events that affect a variety of cellular events that lead to DM-related complications. lead to DM-related complications.

EExample, PKC activation by glucose xample, PKC activation by glucose alters the transcription of genes for alters the transcription of genes for fibronectin, type IV collagen, contractile fibronectin, type IV collagen, contractile proteins, and extracellular matrix proteins, and extracellular matrix proteins in endothelial cells and neurons proteins in endothelial cells and neurons in vitro.in vitro.

Growth factors appear to play an Growth factors appear to play an important role in DM-related important role in DM-related complications. complications.

Other growth factors, such as platelet-Other growth factors, such as platelet-derived growth factor, epidermal growth derived growth factor, epidermal growth factor, insulin-like growth factor I, factor, insulin-like growth factor I, growth hormone, basic fibroblast growth hormone, basic fibroblast growth factor, and even insulin, have growth factor, and even insulin, have been suggested to play a role in DM-been suggested to play a role in DM-related complications. related complications.

Finally, oxidative stress and free Finally, oxidative stress and free radical generation, as a radical generation, as a consequence of the hyperglycemia, consequence of the hyperglycemia, may also promote the may also promote the development of complications.development of complications.

GLYCEMIC CONTROL AND GLYCEMIC CONTROL AND COMPLICATIONSCOMPLICATIONS

The Diabetes Control and Complications The Diabetes Control and Complications Trial (DCCT) provided definitive proof Trial (DCCT) provided definitive proof that reduction in chronic hyperglycemia that reduction in chronic hyperglycemia can prevent many of the early can prevent many of the early complications of type 1 DM. complications of type 1 DM.

This large multicenter clinical trial This large multicenter clinical trial randomized over 1400 individuals with randomized over 1400 individuals with type 1 DM to either intensive or type 1 DM to either intensive or conventional diabetes management, conventional diabetes management, and then evaluated the development of and then evaluated the development of retinopathy, nephropathy, and retinopathy, nephropathy, and neuropathyneuropathy

glycemic controlglycemic control

nonproliferative and proliferative nonproliferative and proliferative retinopathy (47% reduction), retinopathy (47% reduction),

microalbuminuria (39% reduction), microalbuminuria (39% reduction), clinical nephropathy (54%clinical nephropathy (54%

reduction)reduction) neuropathy (60% reduction). neuropathy (60% reduction).

intensive diabetes intensive diabetes managementmanagement

group would experience 15.3 more group would experience 15.3 more years of life without significant years of life without significant microvascular or neurologic microvascular or neurologic complications of DM as compared complications of DM as compared to individuals who received to individuals who received standard therapy.standard therapy.

NEUROPATHY AND DIABETES NEUROPATHY AND DIABETES MELLITUSMELLITUS

occurs in approximately 50% of occurs in approximately 50% of individuals with long-standing type individuals with long-standing type 1 and type 2 DM.1 and type 2 DM.

It may manifest as It may manifest as polyneuropathy, mononeuropathy, polyneuropathy, mononeuropathy, and/or autonomic neuropathy.and/or autonomic neuropathy.

NEUROPATHY AND DIABETES NEUROPATHY AND DIABETES MELLITUSMELLITUS

The most common form of diabetic The most common form of diabetic neuropathy is distal symmetric neuropathy is distal symmetric polyneuropathypolyneuropathy

It most frequently presents with It most frequently presents with distal sensory loss. Hyperesthesia, distal sensory loss. Hyperesthesia, paresthesia, and pain paresthesia, and pain

Physical examination reveals Physical examination reveals sensory loss, loss of ankle sensory loss, loss of ankle reflexes, and abnormal position reflexes, and abnormal position sense. Paresthesia is sense. Paresthesia is characteristically perceived as a characteristically perceived as a sensation of numbness, tingling, sensation of numbness, tingling, sharpness, or burning that begins sharpness, or burning that begins in the feet and spreads proximally. in the feet and spreads proximally.

Pain typically involves the lower Pain typically involves the lower extremities, is usually present at extremities, is usually present at rest, and worsens at night. rest, and worsens at night.

As diabetic neuropathy progresses, As diabetic neuropathy progresses, the pain subsides and eventually the pain subsides and eventually disappears, and a sensory deficit in disappears, and a sensory deficit in the lower extremities persists.the lower extremities persists.

Diabetic polyradiculopathyDiabetic polyradiculopathy is a is a syndrome characterized by severe syndrome characterized by severe disabling pain in the distribution of one disabling pain in the distribution of one or more nerve roots. It may be or more nerve roots. It may be accompanied by motor weakness. accompanied by motor weakness.

Fortunately, diabetic polyradiculopathies Fortunately, diabetic polyradiculopathies are usually self-limited and resolve over are usually self-limited and resolve over 6 to 12 months.6 to 12 months.

MononeuropathyMononeuropathy (dysfunction of (dysfunction of isolated cranial or peripheral isolated cranial or peripheral nerves) is less common than nerves) is less common than polyneuropathy in DM and polyneuropathy in DM and presents with pain and motor presents with pain and motor weakness in the distribution of a weakness in the distribution of a single nerve.single nerve.

Autonomic NeuropathyAutonomic Neuropathy

Can Can involvinvolvee the cholinergic, the cholinergic, noradrenergic, and peptidergic noradrenergic, and peptidergic (peptides such as pancreatic (peptides such as pancreatic polypeptide, substance P, etc.) systems. polypeptide, substance P, etc.) systems.

multiple systems, including: the multiple systems, including: the cardiovascular, gastrointestinal, cardiovascular, gastrointestinal, genitourinary, sudomotor, and genitourinary, sudomotor, and metabolic systems. metabolic systems.

IsIs less than satisfactory. less than satisfactory. glycemic control and will improve glycemic control and will improve

nerve conduction velocity, nerve conduction velocity, Avoidance of neurotoxins Avoidance of neurotoxins

(alcohol), supplementation with (alcohol), supplementation with vitamins for possible deficiencies vitamins for possible deficiencies (B(B1212, B, B66, folate; , folate;

symptomatic treatment are the symptomatic treatment are the mainstays of therapymainstays of therapy

GASTROINTESTINAL/GENITOURINGASTROINTESTINAL/GENITOURINARY DYSFUNCTIONARY DYSFUNCTION

GastroparesisGastroparesis genitourinary dysfunction including genitourinary dysfunction including

cystopathy, erectile dysfunction, and cystopathy, erectile dysfunction, and female sexual dysfunction (reduced female sexual dysfunction (reduced sexual desire, dyspareunia, reduced sexual desire, dyspareunia, reduced vaginal lubrication). Symptoms of vaginal lubrication). Symptoms of diabetic cystopathy begin with an diabetic cystopathy begin with an inability to sense a full bladder and a inability to sense a full bladder and a failure to void completelyfailure to void completely

DIABETIC RETINOPATHYDIABETIC RETINOPATHY

Diabetes causes an array of long-term Diabetes causes an array of long-term systemic complications, which have systemic complications, which have considerable impact on both the patient and considerable impact on both the patient and the society because it typically affects the society because it typically affects individuals in their most productive years. individuals in their most productive years.

Ophthalmic complications Ophthalmic complications corneal abnormalities, glaucoma, iris corneal abnormalities, glaucoma, iris

neovascularization, cataracts, and neovascularization, cataracts, and neuropathies. neuropathies.

However, the most common and potentially However, the most common and potentially most blinding of these complications is most blinding of these complications is diabetic retinopathy. diabetic retinopathy.

Pathophysiology:Pathophysiology:

The exact mechanism by which diabetes The exact mechanism by which diabetes causes retinopathy remains unclear, but causes retinopathy remains unclear, but several theories have been postulated to several theories have been postulated to explain the typical course and history of the explain the typical course and history of the disease disease

Growth hormoneGrowth hormone

It was noted that diabetic retinopathy was It was noted that diabetic retinopathy was reversed in women who had postpartum reversed in women who had postpartum hemorrhagic necrosis of the pituitary gland hemorrhagic necrosis of the pituitary gland (Sheehan syndrome). (Sheehan syndrome).

Platelets and blood viscosityPlatelets and blood viscosity

increased erythrocyte aggregation, increased erythrocyte aggregation, decreased RBC deformability, increased decreased RBC deformability, increased platelet aggregation, and adhesion, poor platelet aggregation, and adhesion, poor circulation, endothelial damage, and focal circulation, endothelial damage, and focal capillary occlusion. capillary occlusion.

retinal ischemia contributes to the retinal ischemia contributes to the development of diabetic retinopathy. development of diabetic retinopathy.

Aldose reductase and Aldose reductase and vasoproliferative factorsvasoproliferative factors

Hyperglicemia shunts excess glucose into Hyperglicemia shunts excess glucose into the aldose reductase pathway in certain the aldose reductase pathway in certain tissues, which converts sugars into alcohol tissues, which converts sugars into alcohol (eg, glucose into sorbitol, galactose to (eg, glucose into sorbitol, galactose to dulcitol). Intramural pericytes of retinal dulcitol). Intramural pericytes of retinal capillaries seem to be affected by this capillaries seem to be affected by this increased level of sorbitol, eventually increased level of sorbitol, eventually leading to the loss of its primary function leading to the loss of its primary function (ie, autoregulation of retinal capillaries). (ie, autoregulation of retinal capillaries).

Loss of function of pericytes results in weakness Loss of function of pericytes results in weakness and eventual saccular outpouching of capillary and eventual saccular outpouching of capillary walls. walls.

These microaneurysms are the earliest detectable These microaneurysms are the earliest detectable signs of DM retinopathy. signs of DM retinopathy.

Ruptured microaneurysms (MA) result in retinal Ruptured microaneurysms (MA) result in retinal hemorrhages either superficially (flame-shaped hemorrhages either superficially (flame-shaped hemorrhages) or in deeper layers of the retina (blot hemorrhages) or in deeper layers of the retina (blot and dot hemorrhages). and dot hemorrhages).

Increased permeability of these vessels results in Increased permeability of these vessels results in leakage of fluid and proteinaceous material, which leakage of fluid and proteinaceous material, which clinically appears as retinal thickening and clinically appears as retinal thickening and exudates. exudates.

Macular edema is the most common cause of Macular edema is the most common cause of vision loss in patients with nonproliferative vision loss in patients with nonproliferative diabetic retinopathydiabetic retinopathy

Another theory to explain the development Another theory to explain the development of macular edema deals with the increased of macular edema deals with the increased levels of diacylglycerol (DAG) from the levels of diacylglycerol (DAG) from the shunting of excess glucose. This is thought shunting of excess glucose. This is thought to activate protein kinase C (PKC), which, to activate protein kinase C (PKC), which, in turn, affects retinal blood dynamics, in turn, affects retinal blood dynamics, especially permeability and flow, leading to especially permeability and flow, leading to fluid leakage and retinal thickening. fluid leakage and retinal thickening.

As the disease progresses, eventual closure As the disease progresses, eventual closure of the retinal capillaries occurs, leading to of the retinal capillaries occurs, leading to hypoxia. hypoxia.

Infarction of the nerve fiber layer leads to Infarction of the nerve fiber layer leads to the formation of cotton-wool spots (CWS) the formation of cotton-wool spots (CWS) with associated stasis in axoplasmic flow. with associated stasis in axoplasmic flow.

More extensive retinal hypoxia triggers More extensive retinal hypoxia triggers compensatory mechanisms within the eye to compensatory mechanisms within the eye to provide enough oxygen to tissues. Venous caliber provide enough oxygen to tissues. Venous caliber abnormalities, such as venous beading, loops, and abnormalities, such as venous beading, loops, and dilation.dilation.

Intraretinal microvascular abnormalities (IRMA) Intraretinal microvascular abnormalities (IRMA) represent either new vessel growth or remodeling represent either new vessel growth or remodeling of preexisting vessels through endothelial cell of preexisting vessels through endothelial cell proliferation within the retinal tissues to act as proliferation within the retinal tissues to act as shunts through areas of nonperfusion. shunts through areas of nonperfusion.

The extracellular matrix is broken down first by The extracellular matrix is broken down first by proteases, and new vessels arising mainly from the proteases, and new vessels arising mainly from the retinal venules penetrate the internal limiting retinal venules penetrate the internal limiting membrane and form capillary networks between membrane and form capillary networks between the inner surface of the retina and the posterior the inner surface of the retina and the posterior hyaloid face. hyaloid face.

Neovascularization Neovascularization borders of perfused and nonperfused retina and borders of perfused and nonperfused retina and

most commonly occur along the vascular arcades most commonly occur along the vascular arcades and at the optic nerve head. and at the optic nerve head.

these vessels rarely cause visual compromise. these vessels rarely cause visual compromise. However, they are fragile and highly permeable. However, they are fragile and highly permeable.

These delicate vessels are disrupted easily by These delicate vessels are disrupted easily by vitreous traction, which leads to hemorrhage into vitreous traction, which leads to hemorrhage into the vitreous cavity or the preretinal space. the vitreous cavity or the preretinal space.

These new blood vessels initially are associated These new blood vessels initially are associated with a small amount of fibroglial tissue with a small amount of fibroglial tissue formation.. formation..

As the vitreous contracts, it may exert tractional As the vitreous contracts, it may exert tractional forces on the retina via these fibroglial forces on the retina via these fibroglial connections. connections.

Traction may cause retinal edema.Traction may cause retinal edema.

Frequency: Frequency: In the US: In the US: Approximately 16 Approximately 16

million Americans have diabetes, million Americans have diabetes, 50% of them not even aware that they have it. Of 50% of them not even aware that they have it. Of

those that know, only one half receives those that know, only one half receives appropriate eye care.appropriate eye care.

diabetic retinopathy is the leading cause of new diabetic retinopathy is the leading cause of new blindness in persons aged 25-74 years in the blindness in persons aged 25-74 years in the United States, responsible for more than 8000 United States, responsible for more than 8000 cases of new blindness each year. cases of new blindness each year.

This means that diabetes is responsible for 12% of This means that diabetes is responsible for 12% of blindnessblindness

Race: Race: An increased risk of diabetic An increased risk of diabetic retinopathyretinopathy

Native AmericanNative American HispanicHispanic African Americans African Americans

History:History:

In the initial stages, patients are generally In the initial stages, patients are generally asymptomaticasymptomatic

in the more advanced stages of the disease, in the more advanced stages of the disease, patients may experience symptoms, patients may experience symptoms, including blurred vision, distortion, or including blurred vision, distortion, or visual acuity loss. visual acuity loss.

Physical: Physical: MicroaneurysmsMicroaneurysms

– Earliest clinical sign of diabetic retinopathy Earliest clinical sign of diabetic retinopathy – Secondary to capillary wall outpouching due to pericyte Secondary to capillary wall outpouching due to pericyte

loss loss – Appear as small red dots in the superficial retinal layers Appear as small red dots in the superficial retinal layers – Fibrin and RBC accumulation in the microaneurysm Fibrin and RBC accumulation in the microaneurysm

lumen lumen – Rupture produces blot/flame hemorrhages Rupture produces blot/flame hemorrhages – May appear yellowish in time as endothelial cells May appear yellowish in time as endothelial cells

proliferate and produce basement membraneproliferate and produce basement membrane

Dot and blot hemorrhagesDot and blot hemorrhages– Occur as microaneurysms rupture in the deeper layers of the retina Occur as microaneurysms rupture in the deeper layers of the retina

such as the inner nuclear and outer plexiform layers such as the inner nuclear and outer plexiform layers – Appear similar to microaneurysms if they are small; may need Appear similar to microaneurysms if they are small; may need

fluorescein angiography to distinguish between the twofluorescein angiography to distinguish between the two

Flame-shaped hemorrhages - Splinter hemorrhages that Flame-shaped hemorrhages - Splinter hemorrhages that occur in the more superficial nerve fiber layeroccur in the more superficial nerve fiber layer

Retinal edema and hard exudates - Caused by the Retinal edema and hard exudates - Caused by the breakdown of the blood-retina barrier, allowing leakage of breakdown of the blood-retina barrier, allowing leakage of serum proteins, lipids, and protein from the vesselsserum proteins, lipids, and protein from the vessels

Cotton-wool spotsCotton-wool spots– Nerve fiber layer infarction from occlusion of Nerve fiber layer infarction from occlusion of

precapillary arteriolesprecapillary arterioles– Fluorescein angiography - No capillary Fluorescein angiography - No capillary

perfusionperfusion– Frequently bordered by microaneurysms and Frequently bordered by microaneurysms and

vascular hyperpermeabilityvascular hyperpermeability

Venous loops, venous beadingVenous loops, venous beading– Frequently adjacent to areas of nonperfusion Frequently adjacent to areas of nonperfusion – Reflects increasing retinal ischemia Reflects increasing retinal ischemia – Most significant predictor of progression to Most significant predictor of progression to

Proliferative DRProliferative DR

Intraretinal microvascular abnormalitiesIntraretinal microvascular abnormalities– Remodeled capillary beds without proliferative Remodeled capillary beds without proliferative

changes changes – Collateral vessels that do not leak on Collateral vessels that do not leak on

fluorescein angiography fluorescein angiography – Usually can be found on the borders of the Usually can be found on the borders of the

nonperfused retinanonperfused retina

Macular edemaMacular edema– leading cause of visual impairment.leading cause of visual impairment.– 75,000 new cases of macular edema are diagnosed 75,000 new cases of macular edema are diagnosed

annually. annually. – Possibly due to functional damage and necrosis of Possibly due to functional damage and necrosis of

retinal capillaries retinal capillaries – Clinically significant macular edema (CSME) is Clinically significant macular edema (CSME) is

defined as any of the following: defined as any of the following: » Retinal thickening located 500 mm or less from the center of Retinal thickening located 500 mm or less from the center of

the foveal avascular zone (FAZ) the foveal avascular zone (FAZ) » Hard exudates with retinal thickening 500 mm or less from the Hard exudates with retinal thickening 500 mm or less from the

center of the FAZ center of the FAZ » Retinal thickening 1 disc area or larger in size located within 1 Retinal thickening 1 disc area or larger in size located within 1

disc diameter of the FAZdisc diameter of the FAZ

Mild nonproliferative diabetic retinopathy - Mild nonproliferative diabetic retinopathy - Presence of at least 1 microaneurysmPresence of at least 1 microaneurysm

Moderate nonproliferative diabetic retinopathy Moderate nonproliferative diabetic retinopathy – Presence of hemorrhages, microaneurysms, and hard Presence of hemorrhages, microaneurysms, and hard

exudates exudates – Soft exudates, venous beading, and IRMA less than that Soft exudates, venous beading, and IRMA less than that

of severe NPDRof severe NPDR

Severe nonproliferative diabetic retinopathy Severe nonproliferative diabetic retinopathy (4-2-1) (4-2-1) – Hemorrhages and microaneurysms in 4 quadrants Hemorrhages and microaneurysms in 4 quadrants – Venous beading in at least 2 quadrants Venous beading in at least 2 quadrants – IRMA in at least 1 quadrantIRMA in at least 1 quadrant

the more advanced stages of NPDR reflect the more advanced stages of NPDR reflect the increasing retinal ischemia setting up the increasing retinal ischemia setting up the stage for proliferative changes. the stage for proliferative changes.

Causes: Causes: Risk factors Risk factors Duration of the diabetesDuration of the diabetes

– In patients with type I diabetes, no clinically In patients with type I diabetes, no clinically significant retinopathy can be seen in the first 5 significant retinopathy can be seen in the first 5 years after the initial diagnosis of diabetes is years after the initial diagnosis of diabetes is made. made.

– After 10-15 years, 25-50% of patients show After 10-15 years, 25-50% of patients show some signs of retinopathy.some signs of retinopathy.

– This prevalence increases to 75-95% after 15 This prevalence increases to 75-95% after 15 years and approaches 100% after 30 years of years and approaches 100% after 30 years of diabetes.diabetes.

In patients with type II diabetes, the In patients with type II diabetes, the incidence of diabetic retinopathy increases incidence of diabetic retinopathy increases with the duration of the disease. with the duration of the disease.

patients with type II diabetes:patients with type II diabetes: 23% have NPDR after 11-13 years23% have NPDR after 11-13 years 41% have NPDR after 14-16 years41% have NPDR after 14-16 years 60% have NPDR after 16 years 60% have NPDR after 16 years

Lab Studies: Lab Studies:

Fasting glucose Fasting glucose hemoglobin A1c (HbA1c)hemoglobin A1c (HbA1c)

Imaging Studies: Imaging Studies:

Fluorescein angiography is an invaluable adjunct in the Fluorescein angiography is an invaluable adjunct in the diagnosis and management of diabetic retinopathy.diagnosis and management of diabetic retinopathy.– Microaneurysms would appear as pinpoint hyperfluorescence that Microaneurysms would appear as pinpoint hyperfluorescence that

does not enlarge but rather fades in the later phases of the test.does not enlarge but rather fades in the later phases of the test.– Blot and dot hemorrhages can be distinguished from Blot and dot hemorrhages can be distinguished from

microaneurysms because they appear as hypofluorescent rather microaneurysms because they appear as hypofluorescent rather than hyperfluorescent.than hyperfluorescent.

– Areas of nonperfusion appear as homogenous dark patches Areas of nonperfusion appear as homogenous dark patches bordered by occluded blood vessels.bordered by occluded blood vessels.

– IRMA is evidenced by collateral vessels that do not leak, usually IRMA is evidenced by collateral vessels that do not leak, usually found in the borders of the nonperfused retina.found in the borders of the nonperfused retina.

multiple microaneurysms. multiple microaneurysms.