Diabetic Retinopathy: Everything Physician Associates Should Know

Diabetes is an increasingly common condition seen and managed by PAs (physician associate/physician assistant). According to the CDC, 38.4 million people in the United States (11.6% of the US population) have diabetes.¹    Physician associates are becoming increasingly relied on for the management of diabetes due to the expected shortfall of physicians.²

A 2018 report found no significant difference in outcomes in the care of diabetic patients among physicians, PAs, and nurse practitioners._²  The PA profession is one of the fastest-growing healthcare professions today–the United States had 139,688 PAs in 2019.^3,4 PAs providing primary healthcare services are in an excellent position to screen patients at risk for diabetic retinopathy.   Many PAs have a background in optometry and/or ophthalmology.  Some PA’s have extensive eyecare experience including performing minor surgical procedures and comprehensive eye exams.⁵   

 

What is Diabetic Retinopathy?

Diabetic retinopathy is a microvascular disease.  Multiple changes in the retinal vasculature occur in the presence of diabetic retinopathy.  Diabetic retinopathy is typically classified into two major types: non-proliferative (NPDR) and proliferative diabetic retinopathy (PDR).  The presence of macular edema should also be noted.   NPDR is categorized as mild, moderate, or severe. 

Mild NPDR consists of microaneurysms only.¹⁰  Moderate NPDR consists of an increased number of microaneurysms and small hemorrhages.¹⁰ Cotton wool spots and hard exudates may be present.¹⁰  Cotton wool spots are believed to be small areas of ischemia from retinal arteriole obstruction.¹¹  Severe NPDR consists of 4 quadrants of diffuse retinal hemorrhages and microaneurysms, 2 or more quadrants of venous beading, or 1 or more quadrants of IRMA (intraretinal microvascular abnormalities).¹⁰ 

Proliferative diabetic retinopathy, or PDR, includes the presence of neovascularization and/or the presence of vitreous/preretinal hemorrhaging.¹⁰ PAs may be the first health provider to suspect diabetic retinopathy during a careful routine physical.  PAs may even detect diabetic retinopathy in the eyes.    A vision screening during the routine health check may pick up decreased visual acuities suggesting that there may be a sight-threatening problem. 

Viewing the retina through undilated pupils with a direct ophthalmoscope may also detect diabetic retinopathy.   The disadvantage of viewing the retina in this setting is that an undilated pupil provides a very limited (if any) view of the retina.  Retinopathy can easily be missed.  Patients must receive pharmacological pupil dilation to view the full extent of the retina.  

Who is at Risk for Diabetic Retinopathy?

Diabetic retinopathy is the most common complication of diabetes mellitus.⁶  Diabetic retinopathy has traditionally been considered a microvascular disease.⁶  However, there are inflammatory and neurodegenerative components as well.⁶ Multiple risk factors have been identified that increase the risk of diabetic retinopathy.  Risk factors are many.  Risk factors include poor glycemic control, pregnancy, puberty, elevated lipid level, high blood pressure, kidney disease, sleep apnea, length of time the patient had diabetes, and dysfunction of biochemical pathways that can lead to inflammation especially as it relates to the retinal blood vasculature, race, higher body mass index, younger age, and past cataract surgery^7,8. 

It seems counterintuitive that younger age would be a risk factor for diabetic retinopathy. After all, length of time with diabetes is a common risk factor.  In my practice, I see many diabetic patients daily.  Diabetic retinopathy seems to be uncommon in patients under 30 years of age.  I would anticipate an increased prevalence of diabetic retinopathy in the elderly.    

Diabetic retinopathy is associated with multiple risk factors more likely to occur in the elderly: High blood pressure, elevated lipid level, and other vascular diseases.  However, I have seen diabetic young adults and children in otherwise good health with significant diabetic retinopathy.  Average HbA1c may account for the age paradox.  Among modifiable risk factors, the average HbA1c has the strongest impact on the progression of diabetic retinopathy.⁷  

Patients with an average HbA1c of 10.0% or greater have a risk ratio for progression of any retinopathy, referable retinopathy, diabetic macular edema, and proliferative diabetic retinopathy compared to those with an average HbA1c of 7.0% or less.⁷   Non-white patients generally have a higher risk of progression to all forms of diabetic retinopathy.⁷ 

The problem in deciding who to refer for a comprehensive eye exam is that any patient with diabetes may have retinopathy.  Even patients without a prior diagnosis of diabetes can have diabetic retinopathy (e.g. prediabetics, patients not yet diagnosed with prediabetes or diabetes).   Any patient with hyperglycemic issues must have a comprehensive eye exam.  I have seen many prediabetics with retinopathy.  Studies that compared patients with normal glucose tolerance and prediabetes showed that the latter group had retinopathy approximately twice as frequently as the former group.⁹ 

How is Diabetic Retinopathy Detected?

Even a thorough comprehensive eye exam with pupil dilation can miss important diabetic eye changes.  New equipment is now available that can provide more in-depth views of the retina which traditional eye exams may miss.  Optical coherence tomography (OCT) is a non-invasive diagnostic technique that produces in vivo cross-sectional views of the retina. 

An OCT basically can view the inside retinal tissue.  More recently, it has been possible to create non-invasive non-dye-based OCT angiography images.¹²   I find the OCT an invaluable tool in detecting macular edema.  Diabetic macular edema arises from the accu­mulation of fluid, protein, and lipids throughout the layers of the retina in the form of intraretinal cystic spaces, best seen by OCT.¹³  Macular edema can be difficult to detect without optical coherence tomography. 

However, if visual acuity is decreased in the presence of diabetic retinopathy, without other explanation, macular edema should be suspected.  New cameras are commercially available that now allow ultra-wide field views of the retina.   I have such a camera at my practice.  These cameras provide very sharp images of most of the retina. These images can be magnified to detect even small retinal hemorrhages and microaneurysms.   I have seen images pick up very small retinal hemorrhages in the peripheral retina that I was unable to visualize with the traditional indirect ophthalmoscope.  In addition, these cameras allow for photo documentation that can be used to show patients as well as to compare with future office visits.  

In summary, many PAs are in a great position to screen patients who are at risk for diabetic retinopathy.   All patients who have diabetes or even prediabetes should have a complete comprehensive eye exam.  Risk factors may increase suspicion of diabetic retinopathy, but retinopathy can show up even without common risk factors present.   PAs may want to refer to an eye care professional who can either dilate the patients’ pupils and/or have an ultra-wide field retinal camera available.   OCT is also important to screen for retinal abnormalities, especially diabetic macular edema.