Diabetic retinopathy

Diabetic retinopathy (DR) is a chronic progressive, potentially sight-threatening disease of the retinal microvasculature associated with the prolonged hyperglycaemia and other conditions linked to diabetes mellitus such as hypertension (1).

• DR is the most common eye problem associated with diabetes
  • other ocular complications of diabetes may include:
    • specific to progression of the ocular disease e.g. - cataract, rubeosis ridis
    • non-specific recognised associations of diabetes in the eye e.g. - glaucoma, retinal vein occlusion/optic disc swelling (1)
• it is a microangiopathy affecting the retinal precapillary arterioles, the capillaries and the venules

The risk of developing diabetic retinopathy is greater with longer duration of diabetes

• large longitudinal studies of patients with diabetes in Wisconsin reported that
  • retinopathy develops within five years of diagnosis of diabetes in about
    • 25% of people with type 1 diabetes
    • 40% of people with type 2 diabetes who are taking insulin and 24% of people with type 2 diabetes who are not taking insulin
    • the 25 year cumulative rate of progression to
      • diabetic retinopathy was 83%
      • diabetic macular oedema was 29%
      • clinically relevant macular oedema was 17%
• in addition to duration of diabetes, poor glycaemic control and uncontrolled hypertension is also associated with greater risk of DR (when compared to patients with good control of these factors) (2,3)
  • control of serum glucose and blood pressure have been shown to be effective in preventing vision loss due to DR
• DR is the leading cause of vision loss in adults aged 20–74 years (4)

A change in vision in DR has two basic mechanisms:

• retinopathy – diabetes-related damage to the whole retina
• maculopathy – diabetes-related damage specific to the central fovea (3)

From 1990–2010, diabetic retinopathy (DR) ranked as the fifth most common cause of preventable blindness and fifth most common cause of moderate to severe visual impairment (5)

• in 2010, of an estimated 285 million people worldwide with diabetes, over one-third have signs of DR, and a third of these are afflicted with vision-threatening diabetic retinopathy (VTDR)
  • defined as severe non-proliferative DR or proliferative DR (PDR) or the presence of diabetic macular edema (DME) (6)
• PDR is the most common vision-threatening lesion particularly among patients with type 1 diabetes
• DME is responsible for most of the visual loss experienced by patients with diabetes as it remains the major cause of vision loss in the highly prevalent type 2 diabetes
  • also is invariably present in patients with type 2 diabetes with PDR (7)

NICE state that "when starting a diabetes treatment that is likely to result in a rapid, substantial drop in the person's HbA1c, notify the person's ophthalmologist so they can assess the person's eyes before treatment begins and check for changes afterwards" (8)

Ophthalmologists should consider fenofibrate for people with non-proliferative retinopathy and type 2 diabetes to reduce the progression of diabetic retinopathy (8).

Notes:

• in the lowering events in non-proliferative retinopathy in Scotland (LENS) trial (9)
  • among participants with early retinal changes (n=1151) found during median of 4 years, fewer patients randomised to fenofibrate developed referable diabetic retinopathy or required treatment for retinopathy or maculopathy (32.1 % v 40.2% placebo; HR 0.74, 95% CI 0.61-0.90)

Reference:

1. Ghanchi F; Diabetic Retinopathy Guidelines Working Group. The Royal College of Ophthalmologists' clinical guidelines for diabetic retinopathy: a summary. Eye (Lond). 2013 Feb;27(2):285-7. doi: 10.1038/eye.2012.287.
2. Ockrim Z, Yorston D. Managing diabetic retinopathy. BMJ. 2010;341:c5400.
3. Broadbent D. Diabetic retinopathy: Fundamentals for primary care. Diabetes & Primary Care 2013;Vol 15 No 4
4. Cheung N, Mitchell P, Wong TY. Diabetic retinopathy. Lancet. 2010 Jul 10;376(9735):124-36. doi: 10.1016/S0140-6736(09)62124-3.
5. Bourne RR, Stevens GA, White RA, Smith JL, Flaxman SR, Price H, Jonas JB, Keeffe J, Leasher J, Naidoo K, Pesudovs K, Resnikoff S, Taylor HR; Vision Loss Expert Group. Causes of vision loss worldwide, 1990-2010: a systematic analysis. Lancet Glob Health. 2013 Dec;1(6):e339-49. doi: 10.1016/S2214-109X(13)70113-X.
6. Yau JW, Rogers SL, Kawasaki R, Lamoureux EL, Kowalski JW, Bek T, et al. Global prevalence and major risk factors of diabetic retinopathy. Diabetes Care. 2012;35(3):556–64.
7. Tong L, Vernon SA, Kiel W, Sung V, Orr GM. Association of macular involvement with proliferative retinopathy in type 2 diabetes. Diabet Med. 2001;18(5):388–94.
8. NICE (August 2024). Diabetic retinopathy: management and monitoring.
9. Preiss D, Logue J, Sammons E, Zayed M, Emberson J, Wade R, Wallendszus K, Stevens W, Cretney R, Harding S, Leese G, Currie G, Armitage J. Effect of Fenofibrate on Progression of Diabetic Retinopathy. NEJM Evid. 2024 Aug;3(8):EVIDoa2400179.