Diabetic Eye Disease

Introduction

Prevalence of diabetic eye disease 

Risk factors for diabetic eye disease 

Screening

Visual acuity

Retinal examination

Frequency of screening

Referral to ophthalmology

Management of patient with diabetic eye disease

Pregnancy

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(See Strength of Recommendations Taxonomy (SORT) for explanation of Grade A-C)

SEMDSA 2017 Recommendations
Diabetic eye disease is a leading cause of visual impairment and screening for diabetic retinopathy is indicated in all patients with type 2 diabetes	A
Aim to optimise glucose, blood pressure and lipid control to reduce the risk and progression of diabetic retinopathy	A
Screening should begin at diagnosis of type 2 diabetes	B
Patients without retinopathy or diminished visual acuity should be screened again every 1 to 2 years	B
Patients should have their visual acuity assessed	C
The preferred screening method for diabetic retinopathy is either fundal photography or dilated indirect ophthalmoscopy	C
Urgent referral to an ophthalmologist is indicated if there is sudden severe vision loss; retinal tear and/or detachment; proliferative diabetic retinopathy or severe diabetic macular oedema	C
Pregnancy may be associated with worsening of retinopathy. Patients should be counselled and screened for diabetic retinopathy prior to pregnancy, or in the first trimester of pregnancy	B

INTRODUCTION 

Diabetic eye disease is a leading cause of visual impairment in the developing world,¹and is mainly comprised of diabetic retinopathy (DR), which includes diabetic macular oedema (DMO), and cataract formation. It is estimated that a third of people living with diabetes will develop diabetic retinopathy.²
Diabetic retinopathy is by and large preventable and/or treatable, while cataract surgery can now successfully be performed on a large scale. It is thus imperative that patients are appropriately screened and referred to an ophthalmologist to detect diabetic eye disease. Vision loss is disabling as it results in a loss of independence and an increased risk of falls. In patients with diabetes this is compounded by their difficulty with administering therapies such as insulin as well as self-monitoring of blood glucose levels.

PREVALENCE OF DIABETIC EYE DISEASE

It is estimated that approximately 34.6% of people with diabetes or 93 million people worldwide have some form of DR with 10.2% having vision-threatening diabetic retinopathy (VTDR).²
Screening studies of DR have often detected a high prevalence of cataracts, even in excess of the prevalence of DR^3,4 and thus cataracts remain a common cause of vision loss in patients with diabetes.

RISK FACTORS FOR DIABETIC EYE DISEASE 

The duration of diabetes is a major risk factor for DR. The prevalence of DR in patients with type 2 diabetes increases two-fold in those with diabetes for up to 19 years compared to those with diabetes for less than 5 years.⁵ Proliferative diabetic retinopathy (PDR), the most vision-threatening form of DR develops in 2% of those with diabetes for under 5 years but is present in 25% of those with diabetes for 25 years^.5

The most important modifiable risk factor is glycaemic control. Poor glucose control is associated with both the development and progression of DR.^6,7,8 There is evidence that tight glycaemic control will lower these risks and should be the target, if this can be attained safely. Blood pressure and lipid control also decrease the risk of DR.⁹ However there is no evidence to support intensive blood pressure control (systolic BP < 120mmHG) to reduce DR.¹⁰

There is evidence that fenofibrate may reduce the progression of DR.¹⁰ Patients who develop diabetic kidney disease are at high risk of also having DR.

SCREENING 

Patients with significant DR may be asymptomatic and hence screening is important to detect patients in whom intervention may prevent vision loss. Patients and their family members must be informed that they may have a significant eye disease that requires treatment even in the absence of symptoms. Since patients with type 2 diabetes may have had many years of undiagnosed diabetes, it is recommended that all such patients should be screened at diagnosis for DR. Ideally this should be done by an ophthalmologist or an optometrist who is trained in detecting DR. This, however, is not always possible in resource limited settings. All screening encounters should begin with a clinical evaluation with emphasis on glycaemic control; duration of diabetes; other co-morbid diseases (hypertension, dyslipidaemia); drug therapy and ocular history.

Although the validity of visual acuity testing to detect DR was previously debated, recent guidelines have suggested that this is of importance in resource restricted settings where the screening is not done by an ophthalmologist^.11,15,18 Screening should therefore be divided into 2 components: visual acuity and retinal examination.

Visual acuity

Visual acuity can be assessed by trained healthcare providers (HCP) in any of the following ways, depending on resources:  

• Refracted visual acuity examination using a 3- or 4-meter visual acuity lane and a high contrast visual acuity chart.¹⁵
• Presenting visual acuity examination using a near or distance eye chart and a pin-hole option if visual acuity is reduced.¹⁵
• Presenting visual acuity examination using a 6/12 (20/40) equivalent handheld chart consisting of at least 5 standard letters or symbols and a pin-hole option if visual acuity is reduced.¹⁵

If visual acuity is less than 6/12 (20/40), the patient requires referral to an ophthalmologist for further evaluation.

Retinal examination

Screening for diabetic retinopathy can be done in the following ways:

• Fundus photographic methods (dilatation improves results):
  • Digital images, 35mm film or Polaroid instant film prints with subsequent grading by trained individuals. The advantage is that it creates a permanent record of the retina. Screening with a mobile fundal camera improved the quality of care for diabetic patients and is feasible in the South African public sector, primary care setting.¹² Retinal photography was found to be effective, acceptable, and cost-effective^.13
  • The photograph should be evaluated by an ophthalmologist or medical doctor, nurse or optometrist properly certified by an authority such as the Ophthalmological Society of South Africa (OSSA). This method offers the possibility of telemedicine whereby patients can be screened at their primary health centres and the interpretation is done by a trained individual remotely.
• Indirect ophthalmoscopy i.e. dilated slit-lamp ophthalmoscopy¹⁵ (evaluated by ophthalmologists)
• Direct ophthalmoscopy through dilated pupils (evaluated by medical practitioners, optometrists, or ophthalmologists), although this is the least reliable method.

Since few primary healthcare nurses in South Africa are trained to screen for DR, most patients at primary health care level will have to be referred to a skilled professional until fundal photography becomes more widespread. DR should be assessed according to the International Classification of Diabetic Retinopathy and Diabetic Macular Oedema (Table I).¹⁴ If DR is detected the patient should be monitored and referred according to the ICO Guidelines for Diabetic Eye Care (Table II).¹⁵ In addition patients who cannot be evaluated by their primary HCP for DR or VA should also be referred for ophthalmology assessment.

Frequency of screening

In patients without evidence of DR or impaired visual acuity, annual follow-up screening is usually recommended. However in resource limited areas there is evidence that screening every 2 years may be cost-effective in patients with no DR and good glycaemic control.¹⁶

Table I: International Classification of Diabetic Retinopathy and Diabetic Macular Oedema ¹⁴

Diabetic Retinopathy	Findings Observable on Dilated Ophthalmoscopy
No Apparent DR	No Abnormalities
Mild nonproliferative DR	Microaneurysms only
Moderate nonproliferative DR	Microaneurysms and other signs (e.g., dot and blot haemorrhages, hard exudates, cotton wool spots), but less than severe nonproliferative DR
Severe nonproliferative DR	Moderate nonproliferative DR with any of the following: Intraretinal haemorrhages (≥20 in each quadrant) Definite venous beading (in 2 quadrants) Intraretinal microvascular abnormalities (in 1 quadrant) and no signs of proliferative retinopathy
Proliferative DR	Severe nonproliferative DR and 1 or more of the following: Neovascularization Vitreous/preretinal haemorrhage
Diabetic Macular Oedema	Findings Observable on Dilated Ophthalmoscopy#
No DMO	No retinal thickening or hard exudates in the macula
Noncentral-involved DMO	Retinal thickening in the macula that does not involve the central subfield zone that is 1mm in diameter
Central-involved DMO	Retinal thickening in the macula that does involve the central subfield zone that is 1mm in diameter

# Hard exudates are a sign of current or previous macular edema. DMO is defined as retinal thickening, and this requires a three-dimensional assessment that is best
performed by a dilated examination using slit-lamp biomicroscopy and/or stereo fundus photography.

Table II: Re-examination and Referral Recommendations based on International Classification of Diabetic Retinopathy and Diabetic Macular Oedema (adapted from ICO Guidelines for Diabetic Eye Care) ²⁵

Diabetic Retinopathy (DR)
Classification	Re-examination  Or next screening schedule	Referral to Ophthalmologist
No apparent DR, mild nonproliferative DR and no DMO	Re-examination in 1-2 year	Referral not required
Mild nonproliferative DR	6-12 months	Referral not required
Moderate non-pro liferative DR	3-6 months	Referral required
Severe nonproliferative DR	< 3-months	Referral required
PDR	< 1 month	Referral required
Diabetic Macular Oedema (DMO)
Classification	Re-examination  Or next screening schedule	Referral to Ophthalmologist
Noncentral-involved DMO	3 months	Referral required
Central-involved DMO	1 months	Referral required

Table III: Referral to ophthalmology¹⁸

Urgent referral: Sudden severe vision loss Retinal tear and/or detachment Proliferative diabetic retinopathy Severe DMO

Referral within three months: Unexplained gradual worsening of vision Non central-involved DMO Visual acuity below 6/12 (20/40) Severe nonproliferative diabetic retinopathy Symptomatic vision complaints

Referral within six months: Unexplained retinal findings Visual acuity cannot be obtained Retinal examination cannot be obtained or inability to visualise fundus Glaucoma Cataract Moderate nonproliferative diabetic retinopathy (no DMO) Mild nonproliferative diabetic retinopathy

 

REFERRAL TO OPHTHALMOLOGY 

Patients with DR and other eye diseases usually require referral to ophthalmologists. Table III is a guide to the urgency of this referral.

MANAGEMENT OF PATIENTS WITH DIABETIC EYE DISEASE 

The detailed ophthalmological management of patients with diabetic eye disease is beyond the scope of this guideline. Photocoagulation surgery and anti-vascular endothelial growth factor therapy are the modalities used by ophthalmologists to treat patients with DR and DMO.

The role of the primary HCP is to ensure optimal glycaemic, blood pressure and lipid control to limit progression of DR. It must be borne in mind that rapid intensification of glycaemic control may result in acute worsening of DR;¹⁷ therefore these patients may benefit from treatment for significant DR prior to intensification.
Good glycaemic control should not be delayed unnecessarily as the benefits outweigh the risks. In addition, patients with DR are likely to have other microvascular complications and patients should be screened for diabetic kidney disease and neuropathy. Patients who are visually disabled should be assisted with appropriate disability grants and rehabilitation.

PREGNANCY 

Pregnancy may be associated with progression of DR.^19,20 Women with pre-existing type 2 diabetes who are planning pregnancy or who have become pregnant should be counselled on the risk of development and progression of DR. These women often have rapid intensification of glycaemic control which may further compound this risk.²⁷ They should be screened prior to falling pregnant or within the first trimester for DR. On the other hand, women with gestational diabetes are not at increased risk and do not require screening for DR.²¹

Authors: Nazeer A Mohamed and Willie Mollentze

References

1. Klein BE. Overview of epidemiologic studies of diabetic retinopathy. Ophthalmic Epidemiol 2007;14:179-83
2. Yau JWY, Rogers SL, Kawasaki R, Lamoureux EL, Kowalski JW, Bek T, et al. Global prevalence and major risk factors of diabetic retinopathy. Diabetes Care. 2012 Mar;35(3):556–64.
3. Khan T, Bertram MY, Jina R, Mash B, Levitt N, Hofman K. Preventing diabetes blindness: Cost effectiveness of a screening programme using digital non-mydriatic fundus photography for diabetic retinopathy in a primary health care setting in South Africa. Diabetes Res Clin Pract. 2013 Aug;101(2):170-6
4. Bai XL, Xu X, Lu M, et al. A cross-sectional study of moderate or severe visual impairment and blindness in residents with type 2 diabetes living in Xinjing Town, Shanghai. Chin J Ophthal.2016 Nov; 52: 825-830
5. Klein R, Klein BE, Moss SE, et al. The Wisconsin Epidemiologic Study of Diabetic Retinopathy. III. Prevalence and risk of diabetic retinopathy when age at diagnosis is 30 or more years. Arch Ophthalmol 1984;102:527-32.
6. UK Prospective Diabetes Study (UKPDS) Group. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). Lancet 1998;352:837-53.
7. Kohner EM, Stratton IM, Aldington SJ, et al. Relationship between the severity of retinopathy and progression to photocoagulation in patients with Type 2 diabetes mellitus in the UKPDS (UKPDS 52). Diabet Med 2001;18:178-84.
8. Wong TY, Liew G, Tapp RJ, et al. Relation between fasting glucose and retinopathy for diagnosis of diabetes: three population-based cross-sectional studies. Lancet 2008;371:736-43.
9. Leske MC, Wu S-Y, Hennis A, et al. Hyperglycemia, blood pressure, and the 9-year incidence of diabetic retinopathy: the Barbados Eye Studies. Ophthalmology 2005;112:799–805
10. ACCORD Study Group, ACCORD Eye Study Group, Chew EY, et al. Effects of medical therapies on retinopathy progression in type 2 diabetes.N Engl J Med 2010;363:233–244
11. Early Treatment Diabetic Retinopathy Study Research Group. Early photocoagulation for diabetic retinopathy: ETDRS report number 9. Ophthalmology 1991;98:766-85. (Vis acuity)
12. Mash B, Powell D, du Plessis F, et al. Screening for diabetic retinopathy in primary care with a mobile fundal camera – evaluation of a South African pilot Project. S Afr Med J 2007; 97: 1284-1288
13. O'Hare JP, Hopper A, Madhaven C, et al. Adding retinal photography to screening for diabetic retinopathy: a prospective study in primary care. BMJ. 1996 Mar 16;312(7032):679-82
14. Wilkinson CP, Ferris FL III, Klein RE, et al. Proposed international clinical diabetic retinopathy and diabetic macular edema disease severity scales. Ophthalmology 2003;110:1679.
15. Wong TY, Aiello LP, Ferris F, et al. ICO Guidelines for Diabetic Eye Care http://www.icoph.org/downloads/ICOGuidelinesforDiabeticEyeCare.pdf
16. Agardh E, Tababat-Khani P. Adopting 3-year screening intervals for sight-threatening retinal vascular lesions in type 2 diabetic subjects without retinopathy. Diabetes Care 011;34:1318– 1319
17. Early worsening of diabetic retinopathy in the Diabetes Control and Complications Trial. Arch Ophthalmol 1998; 116:874-86
18. International Diabetes Federation and The Fred Hollows Foundation. Diabetes eye health: A guide for health care professionals. Brussels, Belgium: International Diabetes Federation, 2015. www.idf.org/eyecare
19. Axer-Siegel R, Hod M, Fink-Cohen S, et al.Diabetic retinopathy during pregnancy. Ophthalmology 1996;103:1815–1819
20. Best RM, ChakravarthyU. Diabetic retinopathy in pregnancy. Br J Ophthalmol 1997;81:249–251
21. Gunderson EP, Lewis CE, Tsai A-L, et al. A 20-year prospective study of childbearing and incidence of diabetes in young women, controlling for glycemia before conception: the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Diabetes 2007;56:2990–2996