Why the periphery matters in DR progression

This month I am delighted to have a guest contribution to my diabetes column from an esteemed colleague, Jeff Gerson, OD, FAAO, of Grin Eye Care in Olathe, KS. Dr. Gerson is passionate about retinal disease, diabetes and optometry, and I have been honored to lecture with him on both diabetes and AMD (age-related macular degeneration) over the past 10 years. -A. Paul Chous, OD

Diabetic retinopathy (DR) in patients is a common finding in optometric practices. When we grade the level of retinopathy, we often do so with findings of the Early Treatment Diabetic Retinopathy Study (ETDRS)in mind.

In the clinic, we evaluate to determine if specific patients need treatment and, if no treatment is needed, we determine an appropriate follow-up schedule for each person. At the same time, ODs also consider the totality of risk factors, including disease duration, degree of diabetes control, and examination findings.

Previously from Dr. Chous: New strategies to assess the risk of diabetes-related vision loss

Of critical importance, the retinopathy grading scale used in ETDRS was based on standardized seven-field stereo photography. This methodology was consistent in how it was performed and read at a reading center. It did not take into account peripheral retinal lesions. We have since come to learn the importance of the peripheral retina in accurately gauging the level of DR and assessing individual risk of progression.

Screening

Much emphasis is put on the importance of screening for DR. As it turns out, much of this screening is being done through telehealth programs. For example, the Joslin Vision Network found twice as much retinopathy with ultra-widefield imaging as compared to with traditional non-mydriatic imaging. ¹

We have all had patients either tell us that another OD first detected their diabetes, or we were the first ones to find their diabetes during a routine eye examination. This can sometimes happen by spotting a single or only a few small peripheral retinal hemorrhages.

In these cases, seemingly inconsequential findings make all the difference by allowing us to make (or infer) a life-changing diagnosis that can be corroborated by laboratory analysis. Although it is easy to assume these findings are “idiopathic,” we should first rule out commonly found systemic diseases that increase morbidity and mortality without proper management, and we can easily test for-hypertension and diabetes.

Related: Worldwide diabetes epidemic approaches half a billion

Grading

One of the purposes of a careful clinical exam is grading the extent of any DR. When we grade only the more central retina, as done in ETDRS, we are going to miss retinopathy in some of our patients.

Recent analysis shows when grading retinopathy with only standard seven-field photography versus including the periphery, we will underestimate the grade/level of retinopathy in 10 percent of cases.² Further, it was determined the field most important to scrutinize for these changes was the temporal periphery.

Failure to detect these peripheral lesions may mean less frequent retinal examinations than are truly indicated due to underestimated pathology, inaccurate grading of retinopathy, and patient risk for progression.

Related: How diabetes affects contact lens wear

Progression

Regardless of the disease in question, patients are often seen more frequently when they are suspected to be at higher risk of disease progression in a shorter time period. As it turns out, peripheral examination for ascertaining the extent of DR pertains here as well.

Although we think of the posterior pole as being where the action is, people with more peripheral DR lesions are more likely to progress than those without.

In patients with predominantly peripheral lesions (PPL), there was a 3.2-times increased risk of a two-step or more progression of DR over a four-year follow-up period. PPL was defined as more than 50 percent of retinopathy being located outside the area of standard ETDRS fields. Patients with PPL had a 4.7-times increased risk for progression from non-proliferative DR to proliferative DR.³

In addition, the greater the total area of PPL, the greater the likelihood of progression. All of these findings were independent of diabetes type, duration, glycosylated hemoglobin (HbA1C), and baseline retinopathy severity.

Periphery and ischemia

It is now believed nonperfusion in DR begins in the mid-peripheral retina, accounting for the increased risk of progression.⁴ Patients with PPL are more likely to have increased areas of nonperfusion and increased nonperfusion index as graded from widefield fluorescein angiography.⁵ Nonperfusion may be behind some of the macular problems we see-namely diabetic macular edema.

Related: Why communication is the key to diabetes success

We now see the importance of the peripheral retina in examination of patients with both diabetes and DR as well as those with diabetes who have not yet been diagnosed (about eight million Americans).⁶

Whether it is through clinical exam or imaging, we must not forget although the posterior pole may be where visually significant changes happen, there is much to be learned from the periphery.

References

1. Silva PS, Cavallerano JD, Tolls D, Omar A, Thakore K, Patel B, Sehizadeh M, Tolson AM, Sun JK, Aiello LM, Aiello LP. Potential Efficiency Benefits of Nonmydriatic Ultrawide Field Retinal Imaging in Ocular Telehealth Diabetic Retinopathy Program. Diabetes Care. 2014;37(1):50-5.

2. Silva PS, Cavallerano, JD, Sun JK, Soliman AZ, Aiello LM, Aiello LP. Peripheral Lesions Identified by Mydriatic Ultrawide Field Imaging: Distribution and Potential Impact on Diabetic Retinopathy Severity. Ophthalmology. 2013 Dec;120(12):2587-95.

3. Silva PS, Vavallerano JD, Haddad NM, Kwak H, Dyer KH, Omar AF, Shikari H, Aiello LM, Sun JK, Aiello LP. Peripheral Lesions Identified on Ultrawide Field Imaging Predict Increased Risk of Diabetic Retinopathy Progression over 4 Years. Ophthalmology. 2015 May;122(5):949-56.

4. Sun JK, Aiello LP. The Future of Ultrawide Field Imaging for Diabetic Retinopathy: Pondering the Retinal Periphery. JAMA Ophthalmology. 2016 Mar;134(3):247-8.

5. Silva PS, Dela Cruz AJ, Ledesma MG, van Hemert J, Radwan A, Cavallerano JD, Aiello LM, Sun JK, Aiello LP. Diabetic Retinopathy Severity and Peripheral Lesions Are Associated with Nonperfusion on Ultrawide Field Angiography. Ophthalmology.2015 Dec;122(12):2465-72.

6. American Diabetes Association. Statistics about Diabetes. Available at: http://www.diabetes.org/diabetes-basics/statistics. Accessed 7/17/17.

Read more from Dr. Chous here