Block 7 & 8

Module

: The Nervous System-Psychiatry- Eye-Ent

: Diabetic Retinopathy

Course Period : Academic Year 2014 2015 4th Semester

Name: Student Guidance

Faculty of Medicine Brawijaya University 2015

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STUDENT GUIDANCE

Course Period : 4th Semester

MODULE : NERVOUS SYSTEM-PSYCHIATRY- EYE-ENT SUBMODULE: OPHTHALMOLOGY TOPIC : DIABETIC RETINOPATHY

1. SUB-TOPICS :

1. Global prevalence of Diabetes mellitus and its complication to the eye 2. Basic anatomy of the retina related to diabetic retinopathy

3. Risk factor and pathogenesis of diabetic retinopathy 4. Clinical features and diagnosis of diabetic retinopathy 5. Prevention and management of diabetic retinopathy 6. Eradication of diabetic blindness

2. CONTRIBUTORS

Ophthalmology staffs at the Department of Ophthalmology, Faculty of Medicine Brawijaya University

3. COMPETENCY AREA

This module is a part of the elaboration of

1. The area of competence 1 ie. The Effective Comunication

2. The area of competence 3 ie. The Scientific-Base of Medical Sciences. 3. The area of competence 4 ie. The Management of Health Problems

4. The area of competence 7 ie. The Professionalism.

4. COMPETENCY COMPONENT

1. The Clinical Skill : Retinal examination

2. The Scientific-Base of Medical Sciences : To apply the concepts and principle of Biomedical Sciences, Clinical Sciences and Public Health in appropiate with Primary Health Care.

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5. LEARNING OBJECTIVES

At the end of the Teaching-Learning Process of this topic, the student should be able to: 1. Understand the anatomy of the retina in relation to diabetic retinopathy

2. Describe the risk factors and pathogenesis of diabetic retinopathy

3. Understand the clinical features of diabetic retinopathy and its diagnosis

4. Understand the prevention and the principles of diabetic retinopathy management 5. Understand the role of general practicioners in the eradication of diabetic blindness

6. LECTURE DESCRIPTION

This topic is a part of Module of The Nervous System integratedly designed for medical student of the 5th semester through Teaching-Learning Process. This part of Module will facilitate the student to have an understanding of general aspect of diabetic retinopathy, especially the prevention to eradicate blindness caused by diabetes mellitus.

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GLOBAL PREVALENCE OF DIABETES MELLITUS AND ITS COMPLICATION TO THE EYE Diabetesmellitusiscommonmetabolicdisordercharacterizedbysustained

hyperglycemia of variable severity, secondary to lack, diminished efficacy, or both of endogenous insulin. Diabetes may be insulin-dependent (IDDM) termed type 1 or non-insulin-dependent (NIDDM) termed type 2. Diabetes mellitus among the leading cause of death, disability, and economic loss throughout the world. WHO has estimated that there were 171 million people worldwide with diabetes mellitus in 2000 and predicted that 366 million people will have diabetes mellitus by the year 2030. The increase will be due mainly to increases in low and middle income countries.

There are many ocular manifestation of diabetes mellitus, like cataract, diabetic retinopathy,and others. Diabetic retinopathy is a microvascular complication of longstanding both type 1 and type 2 diabetes mellitus. It develops in nearly all persons with type 1 diabetes and in more than 77% of those with type 2 who survive over 20 years with the disease. The frightening thing about diabetic retinopathy that this diseases can cause irreversible blindness. WHO has estimated that diabetic retinopathy is responsible for 4.8% of the 37 million cases of blindness throughout the world.

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In order to prevent vision loss due to diabetic retinopathy, primary health care providers

as a case finder have to be improved. The improvement include primary prevention with specific attention of the risk factors, basic examination for screening, and know when to refer.

BASIC ANATOMY OF THE RETINA

Retina isa light-sensitive , transparent tissue lining the inner surface of the eye. Anatomically retina divided into a few general region. The posterior retina defined by anatomist as the macula lutea, or yellow spot containing xantophyll (yellow) pigment. The conventional boundary of the macula, as defined histologically, is that area with 2 or more layers of ganglion cells that is 5-6 mm diameter and is centered vertically between the temporal vascular arcades. The central 1.5 mm of the macula is occupied by the fovea. Within the fovea is a region devoid of retinal vessels known as the foveal avascular zone (FAZ).

The retina outside the macula is called peripheral retina.

Figure 1.Basic anatomy and posterior pole of the retina. Macula shown above is due to

hisstologic definition.

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Figure 2. Anatomical ladmark of the macula (blue circle) and fovea (yellow circle)

In cross-sectional histologic preparation, the layers of the retina can be seen easily. Several layers of neurons interconnected by synapses. They are listed here in order from the inner to outer retina :

Internal limiting membrane (ILM)

Nerve fiber layer (NFL, the axon of ganglion cell layer) Ganglion cell layer

Inner plexiform layer Inner nuclear layer

Outer plexiform layer

Outer nuclear layer (the nuclei of photoreceptors) External limiting membrane

Rod and cone (photoreceptors)

Figure 3. Cross section of the fovea

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Light striking the retina must travel through the full thickness of the retina to reach the

photoreceptors. The density and distribution of photoreceptors vary with topographic location within retina. In the fovea is a densely packed arrangement of cones. The central fovea has no rods. The number of cone photoreceptors decreases rapidly away from the center. The periphery contains almost no cones.

There are 2 sources blood supply to the retina. Central retinal artery that vascularized 2/3 inner retina, and choroidal blood vessels that vascularized 1/3 outer retina, particularly photoreceptor). Fovea avascular zone is vascularized by choroidal blood vessels.

RISK FACTORS AND PATHOGENESIS OF DIABETIC RETINOPATHY

-RISK FACTORS

Diabetic retinopathy can happen to anyone who has diabetes. The risk is greater if the patients has :

Longer duration of diabetes : duration of diabetes predicts the prevalence and severity of diabetic retinopathy. An earlier pre-pubertal diagnosis of diabetes may predict earlier development of diabetic retinopathy. Diabetic retinopathy rarely develops within 5 years of the onset of diabetes or before puberty, but about 5% of type 2 diabetics have diabetic retinopathy at presentation.

Poor glycaemic control: it relevant to the development and progression of diabetic retinopathy.

Blood pressure control: if poorly controlled is associated with worsening of diabetic retinopathy

Blood lipid control: Hyperlipidemia is well established as a risk factor for diabetic retinopathy

Others : smoking, pregnancy,nephropathy,genetic risk factor

-PATHOGENESIS

Many biochemical pathways link the altered glucose metabolism of diabetes directly to development and progression of diabetic retinopathy, which has a multifactorial pathogenesis. This biochemical changes affecting retinal vasculature. Retinopathy exhibits features of both microvascular occlusion and leakage.

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Microvascular occlusion

Pathogenesis : Capillary changes consist of loss of pericytes, thickening of basement membrane and damage and proliferation of endothelial cells. Haematological changes consist of deformation and increased rouleaux formation of red blood cells and increased platelet stickiness and aggregation leading to decrease oxygen transport. The consequences of retinal capillary non-perfusion is retinal ischemia, and it can cause arteriovenous shunt and neovascularization.

Microvascular leakage

Pathogenesis : breakdown of the inner blood retinal barrier leads to leakage plasma constituens into the retina. Physical weakening of the capillary wall results in localized saccular outpouchings of the vessel wall, termed microaneurisms. Consequences of increased vascular permeability include the development of intraretinal haemorrhage and oedema which may be diffused or localized.

Figure 4. Pathogenesis of diabetic retinopathy

Figure 5. Consequences of retinal ischemia in diabetic retinopathy

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Figure 6. consequences of increased vascular permeability in diabetic retinopathy

DIAGNOSIS AND EXAMINATION

-DIAGNOSIS

Diabetic retinopathy can be asymptomatic. Involvement of the fovea by oedema or hard exudates or ischemia is the most common cause of visual impairment. Reduction of visual acuity is gradual and painless. It can be mild to severe. In more severe stage of diabetic retinopathy, severe visual loss can happened. Ussualy it caused by sequelae from ischemia-induced neovascularization. It could be bleeding on the vitreous, tractional retinal detachment, and others. Diabetic retinopathy is classified into an early stage, non proliferative diabetic retinopathy (NPDR), and a more advanced stage, proliferative diabetic retinopathy (PDR). This

latter stage is a manifestasion of ischemia-induced neovascularization from diabetes.

Nonproliferative diabetic retinopathy

Characteristic findings in NPDR include microaneurysm , cotton wool spots (nerve fiber layer infarcts), intraretinal haemorrhages (dot blot), nerve fiber layer haemorrhages (flame shaped), intraretinal microvascular abnormalities (IRMA), hard exudates, retinal oedema, arterioral abnormalities, dilatation and beading retinal veins. NPDR divided into mild,moderate, and severe.

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Proliferative diabetic retinopathy

The signs of NPDR with neovascularization. Neovascularization is the hallmark of PDR. New vessel may proliferate on or within one disc diameter of the optic nerve head(NVD=new vessel at disc), or along the course of major vessel (NVE=New vessel elsewhere), or both.

Diabetic macular oedema can happened at both stage of diabetic retinopathy. The clinical sign are location of retinal thickening relative to the fovea, presence and location of exudates.

Figure 7. Nonproliferative diabetic retinopathy (left), Neovascularized disc in Proliveratife diabetic retinopathy (right)

-EXAMINATION

Screening involves measurement of visual acuity and fundus examination. The gold standard for screening diabetic retinopathy is with clinically examination and fundus photographics with dilated pupil. Pupil dilation using 0.5% to 1% tropicamide eye drop is safe and markedly increases the sensitivity of diabetic retinopathy examination using direct or indirect ophthalmoscope or slit lamp biomicroscopy with special lens. Additional tests include : Fundus Fluorescein Angiography (FFA), Optical Coherence Tomography (OCT)

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PREVENTION AND MANAGEMENT OF DIABETIC RETINOPATHY

The only means of preventing diabetic retinopathy is by regulating blood sugar, blood pressure and other factors under the control of the patient, as guided by their primary care provider or endocrinologist.

In order to achieve the public health goal to minimizing visual loss, secondary prevention is needed. Primary care provider (general practicioner, endocrinologist, diabetologist, or anyone who care with diabetics patients) should do early detection and screening for diabetic retinopathy. Once diabetes mellitus is diagnosed, eye examination should be done.

Table 1. Reccomended eye examination

Diabetes typeFirst examinationFollow up

Type 13-5 years after diagnosedAnnually

Type 2

Prior to pregnancy (type1 or

type2)

At time of diagnosis

Prior to conception and early

in the first trimester

Annually

Every 1-3 months or at

discretion of ophthalmologist

Table 2. Timetable based on retinopathy findings

Retinal abnormality

Normal or rare microaneurysms Mild NPDR

Moderate NPDR Severe NPDR

Clinical significant macular edema PDR

*Consider laser surgery

Suggested follow up

Annually

Every 9 months Every 6 months Every 2-4 months Every 2-4 months*

Every 2-3 months*

If the reduced visual acuity has happened at the time we examine the patients, we have to refer to ophthalmologist. Urgent referral to ophthalmologist must be done if there are conditions like PDR, preretinal or vitreous haemorrhage, rubeosis iridis and retinal detachment.

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There are many ways to manage diabetic retinopathy : with laser photocoagulation,

surgical management (pars plana vitrectomy), and intravitreal injection for symptomatic treatment. The therapy for diabetic retinopathy are depend on the stage and the indication.

ERADICATION OF DIABETIC BLINDNESS

It has been reported that 36% of those with type 2 diabetes mellitus have never had their eyes examined . These patients tend to be older, less educated and to have had a more recent diagnosis than those receiving regular eye care. They are also likely to live in rural areas and receive health care from a family or general practitioner. Alarmingly, 32% of patients with diabetes mellitus at high risk for vision loss never undergo an eye examination, and less than 40% of those with high-risk characteristics for vision loss receive treatment. When examined, almost 61% of these patients are found to have diabetic retinopathy, cataract, glaucoma or another ocular manifestation of diabetes mellitus. These findings have significant implications for the person and for society.

In order to reduce diabetic blindness, primary health provider should know the principles in eye care for patients with diabetes.

Patients should know that they have diabetes mellitus and the condition requires care

Patients should receive adequate care for diabetes mellitus, as guided by the general practitioner as the primary health provider, endocrinologist, or diabetologist

Patients should undergo eye examination for the presence of diabetic retinopathy

If retinopathy is detected, or patients is referred to an ophthalmologist for an examination, the society must deliver the necessary level of eye care

Patients should be sufficiently aware and motivated that they not only undergo eye examination but also return regularly for such examination

Through this approach that involve general practitioners as primary health providers, endocrinologist, diabetologist, ophthalmologist, the awareness of patients with diabetes mellitus, and society, it is expected that diabetic blindness can be reduced.

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MODULE TASK

Find out your answers to the following tasks by yourself after discuss it with your group or after reading the suggested references below.

1. What is the definition of diabetes mellitus

2. Explain the pathogenesis of diabetes mellitus can cause retinopathy

3. When we should perform eye examination for diabetes mellitus patients 4. Explain how to diagnosed diabetic retinopathy

5. Explain how diabetes mellitus can cause irreversible blindness in diabetic retinopathy 6. Explain how to prevent diabetic retinopathy as a primary health care provider

7. In what condition you have to refer the diabetic retinopathy patients to the ophthalmologist

REFERENCES

Report of WHO consultation in Geneva. Prevention Of Blindness From Diabetes mellitus.Geneva: WHO Press. 2006

American Academy of Ophthalmology staff. Basic And Clinical Science Course : Retina and Vitreus. San Fransisco : American Academy of Ophthalmology. 2008-2009

Kanski JJ, Clinical Ophthalmology, A Systematic Approach. 6th ed. Edinburgh: Butterworth-Heinemann. 2007

Mitchell Paul, Foran Suriya (Australian Diabetes Society). Guidelines for the management of Diabetic retinopathy. Commonwealth of Australia: National Health and medical Research Council.2008

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