The statistics are undeniable. More than 130 million Americans have diabetes or prediabetes.¹ More alarming, millions of people don’t even know they have the condition.

As the number of people living with diabetes increases, so does diabetic retinopathy (DR) and diabetic macular edema (DME), the leading causes of visual impairment and blindness in Americans ages 20 to 74.^2-3 Additionally, 28.5% of patients ages 40 and older who have diabetes have DR, with 13.6% of DR patients having DME.^3-4 What’s more, DR is projected to climb to 11 million by 2030.⁴

Based on these numbers, it’s clear optometrists should utilize the latest technology available to aid them in keeping tabs on diabetes progression. This article addresses these technologies, including personal patient devices. (See “Telemedicine and Artificial Intelligence for Diabetes,” p. 62.)

OPHTHALMIC DIAGNOSTIC DEVICES

• Fundus photography. Standard retinal photography provides about a 30° view of the posterior pole. Ultra-widefield (UWF) imaging allows for a large field of view, enabling the OD to detect peripheral lesions, which suggest severe DR. Incidentally, eyes that have predominantly peripheral lesions (defined as outside of the Early Treatment Diabetic Retinopathy Study 7 standard field) had a 4.7-fold increased risk of progression to proliferative DR (PDR).⁵

Ultra-widefield imaging and confocal scanning laser ophthalmoscopy, which address these drawbacks, possess great potential, as they do not require dilation.⁶

• Optical coherence tomography (OCT). OCT allows optometrists to identify and manage DME early. Currently, DME is categorized as center vs. non-center-involving, based on SD-OCT. Center-involving DME is characterized by loss of foveal contour, cystoid macula edema involving the center of the fovea, neurosensory detachment involving the center of the fovea, and increased central macular thickening measurement. Non-center-involved DME involves retinal thickening and/or cystic spaces not directly involving the center of the macula.

This technology has also proven useful in visualizing disorganization of the retinal inner layers (DRIL), which might predict visual outcomes.⁷ Proliferative DR features (e.g., neovascularization) and vitreomacular traction, which can induce or exacerbate DME, can also be seen via OCT.^8-9

OCT angiography (OCTA) can aid ODs in detecting subclinical microaneurysms at the deep capillary plexus and other vascular anomalies (e.g., vascular loops, tortuosity and dilations of the vessels), intraretinal microvascular abnormalities, and neovascularization. Additionally, the technology can help optometrists identify diabetic macular ischemia (DMI), which appears as areas of capillary nonperfusion, impairment of the choriocapillaris flow, and enlargement of the foveal avascular zone (FAZ). Abnormalities in the structure or perfusion of the FAZ result in vision impairment and a poor prognosis, as this condition can’t be treated. DMI should be ruled out in patients who have poor vision at presentation or despite attempted treatment for DME.

• Support technologies. B-scan ultrasonography, angiography, and devices that assess abnormal visual function are supportive technologies in monitoring the progression of diabetes.

B-Scan ultrasonography is a valuable tool in cases of vitreous hemorrhage or media opacities.

Widefield fluorescein angiography (FA) and indocyanine green (IGC) angiography are beneficial to ODs, as they help detect peripheral capillary network nonperfusion, which can increase DR severity.¹⁰

Devices that aid in assessing abnormal visual function (e.g., decreased color perception, contrast sensitivity, and abnormal electrophysiology of the retina) detect the early visual function compromised due to diabetes before the occurrence of DR.^11-12 Therefore, optometrists should consider using such devices. As lutein, meso-zeaxanthin, and zeaxanthin can inhibit the development of DR, optometrists should also consider Macular Pigment Optical Density (MPOD) testing.¹³

PERSONAL PATIENT DEVICES

• Continuous glucose monitoring. In addition to longer duration, glycemic control, blood pressure, and cholesterol contribute considerably to the onset, severity, and progression of DR complications. Optimal glycemic control (A1c ≤7), as observed in major diabetes studies, is key to reducing or preventing progression of DR.^14-15 However, A1c is unreliable in patients who have anemia, hemoglobinopathies, or iron deficiency. Also, evidence shows that A1c differs among minority racial and ethnic groups.^16-17

The good news: Continuous glucose monitoring provides the parameter Time in Range (TIR), which goes beyond A1c, allowing for a more reliable parameter to assess glycemic control in patients who have diabetes. Specifically, it indicates the percentage time a person’s glucose value was within the target range of 70 mg/dL to 180 mg/dL during a defined period of >70%.¹⁸ The greater the TIR, the lower the risk of developing complications. The lower the TIR, the higher the risk of developing complications. Incidentally, patients who had advanced DR had significantly less TIR and higher measures of glycemic variability than those with less severe or no DR. In fact, TIR was significantly associated with the prevalence of all stages of DR.¹⁹

Given this information, it makes sense for optometrists to recommend continuous glucose monitoring to patients who have anemia, hemoglobinopathies, iron deficiency, or to those who belong to a minority racial and ethnic group. Additionally, ODs should inform all patients who have diabetes that cholesterol-lowering medications are beneficial in slowing the progression of DR.²⁰

• Insulin pump. For patients who have diabetes and are tired of injections, an insulin pump, which provides a continuous subcutaneous insulin infusion, can bring welcomed relief, while possibly decreasing the risk of DR development in young patients who have diabetes.²¹ Therefore, ODs should also suggest this technology to their patients who have diabetes. As minority youths, particularly Blacks, were 2.1 times more likely to develop DR than white youth,²¹ access and increased use of insulin pumps is especially important in minority populations. Optometrists should educate their patients to talk to their primary care provider about how to gain access to an insulin pump.

• Fingertip pulse oximeter. The COVID-19 pandemic has disproportionately affected patients who have diabetes. Specifically, these patients have an increased risk of a poor prognosis and a higher mortality rate when compared to non-diabetic patients.²² Additionally, the risk of death from COVID-19 is four times greater for diabetic patients. In fact, nearly 40% of people who have died from COVID-19 had diabetes.²³

With the virus apparently here to stay, patients who have diabetes should monitor their oxygen levels, blood pressure, and heart rate. With the recently published hypertension guidelines, patients who have diabetes should make sure their blood pressure is <130/80 mmHg.²⁴

As a non-invasive fingertip pulse oximeter can help detect low oxygen levels, ODs should recommend their diabetic patients acquire one, and optometrists can provide this direct link to such devices: https://amzn.to/3uFVV8v . Additionally, ODs should educate patients that if their oxygen level is lower than 94%, and patients are having symptoms of respiratory distress, such as any shortness of breath, they should contact their regular health care provider immediately. Another reason to recommend patients who have diabetes use the pulse oximeter is to help detect sleep apnea, which is more prevalent in these patients. Sleep apnea can increase the risk of sleep hypoxia. Sleep hypoxia, if severe enough, can lead to death.²⁵

WHEN TO REFER

The DR Severity Scale²⁸ is valuable. Optometrists should refer all patients who have severe diabetic eye disease to a retinal specialist to determine treatment. Anti-VEGF injections are the first-line treatment for any patient who has center-involved DME and PDR.^26-27

In cases of persistent edema after three to six injections, the retinal specialist may switch the anti-VEGF agent, employ a laser, or use steroids. For patients who have non-center-involved DME, treatment may be a focal laser, anti-VEGF, or observation if the patient’s vision isn’t compromised. Finally, in patients with compromised vision, consider a referral to a low vision specialist.

REIGN IN DIABETES

Diabetes is an epidemic. Improving interaction among the patient’s health care team is critical in preventing vision loss. OM

REFERENCES

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3. American Academy of Ophthalmology. Diabetic Retinopathy PPP 2019. https://www.aao.org/preferred-practice-pattern/diabetic-retinopathy-ppp . (Accessed March 29, 2022.)4. Varma R, Bressler NM, Doan QV, et.al. Prevalence of and risk factors for diabetic macular edema in the United States. JAMA Ophthalmol. 2014 Nov;132(11):1334-40. doi: 10.1001/jamaophthalmol.2014.2854.
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30.  American Optometric Association. Evidence-based Clinical Practice Guideline: Eye Care of the Patient With Diabetes Mellitus. www.aoa.org/optometrists/tools-and-resources/evidence-based-optometry/evidence-based-clinical-practice-guidlines/cpg-3--eye-care-of-the-patient-with-diabetes-mellitus. Accessed April 11, 2022. 
    
    

DR. REYNOLDS is an associate professor at Nova Southeastern University and chief of Advanced Ophthalmic Care and Specialty Testing, The Eye Care Institute. Additionally, she is chief of Primary Care, The Eye Care Institute-Davie. She is a Fellow in the American Academy of Optometry and the Optometric Retina Society.