The modified Airlie House classification has been used to classify nonproliferative diabetic retinopathy (NPDR) since the Diabetic Retinopathy Study (DRS) and Early Treatment Diabetic Retinopathy Study (ETDRS). (1-3) Since this classification determines management of nonproliferative diabetic retinopathy, it is extremely important to know these criteria. This classification has been further refined by Wilkinson et al for international use and was adopted as part of the AAO's Preferred Practice Pattern for Diabetic Retinopathy. (4,5)
- Look at images. Lots of them. While the BCSC and the AAO PPP provide very helpful charts and definitions for grading the severity of diabetic retinopathy, there weren't a lot of images provided for helping know exactly how to grade NPDR. Having other resources such as Kanski's Clinical Ophthalmology textbook or Spalton's Atlas of Clinical Ophthalmology were very useful. While I never got Gass' Atlas of Macular Diseases or Yannuzzi's Retinal Atlas, these would also be very helpful resources. You can also check out these free online resources I found that might be good study aids. Even if you're not a visual learner, this classification is pattern recognition, and by having a mental picture of each grade of NPDR, you'll have more than just words to help you get a sense of how to manage your patient's retinopathy.
- Answer the questions you and your patients want to know. Of course, there are tons of ways to learn the material and only you will be able to figure out how you learn best, but another strategy for learning NPDR classification is to create a list of "frequently asked questions" that your patients may ask, and answer them (this strategy holds true for learning any other disease process). After all, clinical questions form the inspiration for these many research studies. Some examples of questions might be:
- What does "diabetic retinopathy" mean?
- Based on the severity of my diabetic retinopathy, how often do I need to follow-up, and what testing will I need at each exam?
- When do I need to be treated for diabetic retinopathy?
- Am I at risk for losing vision due to diabetic retinopathy?
- Is there anything I can do to improve my diabetic retinopathy?
- Quiz yourself. Find a friend (or friends) who can study with you. Having other people hold you accountable to the details will help keep you from glossing over specific details you need to know as you're reading. While this doesn't apply or work for everyone, having to answer very specific questions helped me solidify my knowledge. Some examples of specific questions might be:
- What are the criteria for mild nonproliferative diabetic retinopathy, and when do you need to schedule a follow-up exam?
- What is the 4-2-1 rule?
- What are the criteria for very severe NPDR, and when do you need to schedule a follow-up exam?
- What are the criteria for severe NPDR, and when do you need to schedule a follow-up exam?
- What are the criteria for moderate NPDR, and when do you need to schedule a follow-up exam?
Classification and Management (1-7)
The following table is adapted from multiple sources. I was able to find some images available for linking under the Creative Commons license, which will hopefully help illustrate each stage of NPDR. Obviously, the management of these stages will differ if there is the presence of any macular edema or clinically significant macular edema.
- No evidence of retinal vascular disease
- Yearly with dilated funduscopic exams
- ETDRS: ≥ 1 microaneurysm with no other findings
- Kanski: microaneurysms, retinal hemorrhages, exudates, cotton wool spots, up to the level of moderate NPDR with no IRMAs or venous beading
- 12 months with dilated funduscopic exam
One of the following (4-2-1 rule):
- 4 quadrants of ≥ 20 hemorrhages
- ≥ 2 quadrants of venous beading
- ≥ 1 quadrant of IRMAs
- 4 months with dilated funduscopic exam
- ~15% risk for progression to high-risk PDR (8)
Very Severe NPDR
- ≥ 2 of the 4-2-1 criteria
- 2-4 months with dilated funduscopic exam
- ~50% risk for progression to PDR (8)
- Can consider panretinal photocoagulation on a case-by-case basis; consider getting an FA to look for evidence of capillary dropout (9)
- The Diabetic Retinopathy Study Research Group. A modification of the Airlie House classification of diabetic retinopathy. DRS report #7. Invest Ophthalmol Vis Sci 1981; 21:210-26.
- Early Treatment Diabetic Retinopathy Study Research Group. Early Treatment Diabetic Retinopathy Study design and baseline patient characteristics: ETDRS report number 7. Ophthalmology 1991; 98:741-56.
- Early Treatment Diabetic Retinopathy Study Research Group. Grading diabetic retinopathy from stereoscopic color fundus photographs - an extension of the modified Airlie House classification. ETDRS report number 10. Ophthalmology 1991; 98:786-806.
- 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.
- American Academy of Ophthalmology Retina/Vitreous Panel. Preferred Practice Pattern Guidelines. Diabetic Retinopathy. San Francisco: American Academy of Ophthalmology; 2014. Available at www.aao.org/ppp (actual link).
- Retinal Vascular Disease. In: Kanski JJ, Bowling B, eds. Clinical Ophthalmology: A Systemic Approach, 7th Ed. Edinburgh: Elsevier; 2011:534-551.
- Retinal Vascular Disease: Diabetic Retinopathy. In: Retina and Vitreous. Basic and Clinical Sciences Course, Section 12, 2012-2013 ed. San Francisco: American Academy of Ophthalmology; 2012:89-112.
- Early Treatment Diabetic Retinopathy Study Research Group. Fundus photographic risk factors for progression of diabetic retinopathy. ETDRS report number 12. Ophthalmology 1991; 98:823-833.
- Early Treatment Diabetic Retinopathy Study Research Group. Fluorescein angiographic risk factors for progression of diabetic retinopathy. ETDRS report number 13. Ophthalmology 1991; 98:834-840.
Do you have any strategies for learning how to classify NPDR? Leave a comment!