The prevalence of diabetes is expanding at an alarming rate. More than 133 million Americans are now living with diabetes or prediabetes—an increase of 11 million in the past 2 years (28). More concerning is that millions of these individuals are unaware of their diabetes or prediabetes status (28).

Given the sharp increase in diabetes, it is expected that the prevalence of diabetes-related eye disease— diabetes-related retinal disease (DRD) as well as glaucoma, cataracts, and other ocular disorders—will also continue to rise. DRD and its associated pathology, including diabetes-related macular edema (DME), is the leading cause of visual impairment and vision loss in adults between the ages of 20 and 74 years (16,18). DRD affects >7 million Americans, and the National Eye Institute projects an increase to >11 million people by 2030 (29).

Preventing or delaying the onset and slowing the progression of DRD is the goal of all eye care professionals (ECPs) and other health care professionals (HCPs) who participate in the care of people with diabetes. A crucial component of successfully meeting this goal is communication between ECPs and other diabetes HCPs to properly coordinate care. This chapter explains how to interpret eye examination reports for people with diabetes and reviews the latest information regarding diagnostic technologies, patient education, treatments, and telemedicine-based DRD screening. This information is necessary to facilitate collaborative care among ECPs and HCPs and ensure the best outcomes for their shared patients with diabetes.

It is estimated that ≥20% of people with diabetes first learn of their diabetes status through an eye exam (30). Thus, a diabetes-related eye exam record should include information about the person's diabetes status, ethnicity, age, duration of diabetes if present, and modifiable risk factors. These risk factors include the “ABCs of diabetes” (A1C, Blood pressure, Cholesterol, and Smoking status), as well as BMI/obesity status and nutritional concerns.

As observed in major diabetes clinical trials (19,20,31), lowering A1C to ≤7% is key to reducing the risk or slowing the progression of DRD and other diabetes complications (Table 1). Small reductions add up; even a 1% reduction in A1C can reduce microvascular and macrovascular complications. In addition, for people with diabetes who use continuous glucose monitoring (CGM), time in range and related CGM-derived parameters (32) should also be noted during eye exams.

TABLE 1

Reductions in Complication Rates with A1C Lowering in Major Clinical Trials (19,20)

ComplicationPrevalence Reduction, %
Diabetes Control and Complications Trial*UK Prospective Diabetes Study
Retinopathy 63 17–21 
Nephropathy 54 24–33 
Neuropathy 60 — 
Macrovascular disease (stroke and myocardial infarction) 41 16 
ComplicationPrevalence Reduction, %
Diabetes Control and Complications Trial*UK Prospective Diabetes Study
Retinopathy 63 17–21 
Nephropathy 54 24–33 
Neuropathy 60 — 
Macrovascular disease (stroke and myocardial infarction) 41 16 
*

Percentage reduction in prevalence of complications from lowering mean A1C from 9 to 7%.

Percentage reduction in prevalence of complications from lowering mean A1C from 8 to 7%.

Comorbidities such as hypertension and dyslipidemia should be addressed (33). The benefits of blood pressure and lipid-lowering medications in slowing the progression of DRD have been established for people with type 2 diabetes in clinical trials such as the FIELD (Fenofibrate Intervention and Event) study (34) and the ACCORD (Action to Control Cardiovascular Risk in Diabetes) Eye study (35).

Additionally, eye examination records should include information about medication use—particularly diabetes medications—to assess medication-taking consistency and engagement with the diabetes treatment plan.

All people with diabetes should have regular dilated retinal exams to identify the presence of any diabetes-related eye diseases and ensure prompt treatment if they develop. However, many people with diabetes are unaware that they have the disease, making it unlikely that they will receive these exams. Additionally, many people with significant vision-threatening DRD remain asymptomatic and may therefore be unaware that they are even at risk for serious ocular complications. According to one recent study (36), ~60% of Americans with diabetes do not receive eye exams as recommended. For this reason, it is crucial for all diabetes care professionals to consistently reinforce the importance of getting regular dilated retinal exams.

A diabetes-related eye exam report will include symptoms that might indicate undiagnosed diabetes, including refractive changes, early-onset cataracts (especially posterior subcapsular cataracts), ocular surface disease (i.e., dry eyes), and other diabetes-related findings (Table 2).

TABLE 2

Components of a Comprehensive Diabetes-Related Eye Exam

ComplicationsSymptoms/SignsTesting
Refractive errors Fluctuating or blurry vision related to glycemic variability Best corrected visual acuity test 
Abnormal visual function Abnormal color vision or visual function deficits Tests to detect decreased color perception, contrast sensitivity, and abnormal electrophysiology of the retina 
Neurological disorders Optic nerve issues (e.g., cranial nerve palsies, neovascularization, or glaucoma) Checks of pupils, extraocular motility, tonometry, and visual field 
Anterior segment disorders Dry eyes, corneal erosion, reduced corneal sensitivity, iris neovascularization, and cataracts Slit-lamp examination 
Retinal conditions (e.g., DRD, DME, vitreomacular traction, retinal vascular occlusion, vitreous hemorrhage, and tractional retinal detachment) Decreased vision, metamorphopsia, or sudden loss of vision Dilated retinal exam, retinal photography/widefield imaging, optical coherence tomography, and optical coherence tomography angiography, and ultrasonography 
ComplicationsSymptoms/SignsTesting
Refractive errors Fluctuating or blurry vision related to glycemic variability Best corrected visual acuity test 
Abnormal visual function Abnormal color vision or visual function deficits Tests to detect decreased color perception, contrast sensitivity, and abnormal electrophysiology of the retina 
Neurological disorders Optic nerve issues (e.g., cranial nerve palsies, neovascularization, or glaucoma) Checks of pupils, extraocular motility, tonometry, and visual field 
Anterior segment disorders Dry eyes, corneal erosion, reduced corneal sensitivity, iris neovascularization, and cataracts Slit-lamp examination 
Retinal conditions (e.g., DRD, DME, vitreomacular traction, retinal vascular occlusion, vitreous hemorrhage, and tractional retinal detachment) Decreased vision, metamorphopsia, or sudden loss of vision Dilated retinal exam, retinal photography/widefield imaging, optical coherence tomography, and optical coherence tomography angiography, and ultrasonography 

As mentioned earlier in this compendium (p. 4), people with type 2 diabetes should have an initial dilated retinal exam near the time of diagnosis and generally annually thereafter. By the time a person is diagnosed with type 2 diabetes, the disease often has been present for several years; indeed, 33% of individuals who are newly diagnosed will already have some degree of DRD (37). The screening interval can be extended to 2 or 3 years in individuals with type 2 diabetes who reliably follow up, whose diabetes is well controlled, and who have had a normal dilated retinal exam previously (38). Individuals with DRD may require more frequent follow-up, depending on its severity.

DRD can progress rapidly during pregnancy. Therefore, all women with type 1 or type 2 diabetes who become pregnant should have a dilated retinal exam in the first trimester of pregnancy, with additional monitoring every trimester and for 1 year postpartum as indicated by the degree of DRD present.

After a diabetes-related eye exam, the ECP should share a report with the person's HCP. This report will include information about the person's stage of DRD (Table 3) (39) and presence of DME, if applicable; a summary of retinal imaging results, telemedicine screening, and/ or other diagnostic tests; and treatment and follow-up recommendations, including the need for referral to a retinal specialist, if appropriate. Table 4 defines some of the common abbreviations ECPs often use in reporting findings of diabetes-related eye exams.

TABLE 3

Disease Severity Scale for DRD (39)

Severity LevelDescription
No apparent DRD No abnormalities 
Mild NPDR Microaneurysms only 
Moderate NPDR Hemorrhages, exudates, and/or microaneurysms; cotton wool spots; venous beading; intraretinal microvascular abnormalities 
Severe NPDR Classified using the 4–2–1 rule:
  • Hemorrhages in all 4 quadrants

  • Venous beading in at least 2 quadrants

  • Intraretinal microvascular abnormalities in at least 1 quadrant

 
PDR Neovascularization; vitreous or pre-retinal hemorrhage 
Severity LevelDescription
No apparent DRD No abnormalities 
Mild NPDR Microaneurysms only 
Moderate NPDR Hemorrhages, exudates, and/or microaneurysms; cotton wool spots; venous beading; intraretinal microvascular abnormalities 
Severe NPDR Classified using the 4–2–1 rule:
  • Hemorrhages in all 4 quadrants

  • Venous beading in at least 2 quadrants

  • Intraretinal microvascular abnormalities in at least 1 quadrant

 
PDR Neovascularization; vitreous or pre-retinal hemorrhage 
TABLE 4

Abbreviations Commonly Used in Diabetes-Related Eye Exam Reports and Their Definitions

AbbreviationDefinition
BCVA Best corrected visual acuity 
CN Cranial nerve; various CN palsies can hinder extraocular motility in specific ways. 
CWS Cotton wool spot; also known as soft exudates, these are infarcts within the retinal nerve fiber layer that appear white and feathery. 
DME Diabetes-related macular edema; an ocular complication of diabetes characterized by fluid build-up in the macula— the part of the eye responsible for clear straight-ahead vision. 
DMI Diabetes-related macular ischemia; DMI refers to the presence of occlusion, atrophy, or loss of retinal capillaries in the macula, with narrowing or obliteration of precapillary arterioles. 
DR/DRD Diabetes-related retinopathy or diabetes-related retinal disease; the most common and serious type of diabetes-related ocular complication, DR or DRD refers to mild to severe damage to retinal blood vessels caused by high blood glucose. 
EOM Extraocular motility; movement of the six muscles that, when functioning properly, allow the eyes to move and focus together in various directions. 
FAZ Foveal avascular zone; an area at the center of the retina that is devoid of blood vessels. 
HE Hard exudates; HEs are distinct white/yellow cholesterol deposits resulting from active or resolved DME. 
IOP Intraocular pressure; fluid pressure inside the eye that, if elevated, could be a sign of glaucoma. 
IRMA Intraretinal microvascular abnormality; one of the defining features of severe NPDR (see definition below), IRMAs are abnormal branching or widened retinal blood vessels that supply areas of nonperfusion in DRD. 
MA Microaneurysm; an early sign of DRD, MAs are small-vessel aneurysms resulting from weakening of capillary walls. 
NPDR Nonproliferative diabetes-related retinal disease; the more common form of DRD, NPDR is a condition in which the walls of retinal blood vessels weaken and sometimes leak fluid and blood into the retina, but new blood vessels are not yet growing (proliferating) in response to this damage. It is subclassified as mild, moderate, and severe and can also cause DME (see definition above). 
NVI Neovascularization of the iris; NVI occurs when new blood vessels grow in response to retinal ischemia, is associated with PDR (see definition below), and may cause spontaneous hyphema and neovascular glaucoma. 
NVD/NVE Neovascularization of the disk or elsewhere in the retina; NVD/NVE occurs when new blood vessels grow in response to retinal ischemia, is associated with PDR (see definition below), and may cause spontaneous vitreous hemorrhage. 
OCT Optical coherence tomography; an imaging test that uses light waves to take cross-section pictures of the retinal, OCT allows ECPs to see and measure the distinctive layers of the retina to diagnose and guide treatment of DRD and glaucoma. 
OCTA Optical coherence tomography angiography; OCTA is an imaging technique that uses laser light reflectance of the surface of moving red blood cells to accurately depict retinal vessels without the use of dye. 
PDR Proliferative diabetes-related retinal disease; PDR is the most advanced stage of DRD, characterized by the growth of new, fragile blood vessels in the retina (neovascularization). 
TRD Tractional retinal detachment; TRD is the separation of the neurosensory retina from the retinal pigment epithelium resulting from the traction caused by proliferative membranes present over the retinal surface or vitreous. 
UWF Ultra-widefield; UWF imaging provides a 200° panoramic image of the retina, allowing ECPs to better visualize and evaluate retinal abnormalities. 
VB Venous beading; a late-stage finding in NPDR that represents weakened walls of major retinal vessels, VB is one of the strongest predictors for progression to PDR. 
VH Vitreous hemorrhage; VHs are caused by bleeding from fine neovascular blood vessels in the eye. 
AbbreviationDefinition
BCVA Best corrected visual acuity 
CN Cranial nerve; various CN palsies can hinder extraocular motility in specific ways. 
CWS Cotton wool spot; also known as soft exudates, these are infarcts within the retinal nerve fiber layer that appear white and feathery. 
DME Diabetes-related macular edema; an ocular complication of diabetes characterized by fluid build-up in the macula— the part of the eye responsible for clear straight-ahead vision. 
DMI Diabetes-related macular ischemia; DMI refers to the presence of occlusion, atrophy, or loss of retinal capillaries in the macula, with narrowing or obliteration of precapillary arterioles. 
DR/DRD Diabetes-related retinopathy or diabetes-related retinal disease; the most common and serious type of diabetes-related ocular complication, DR or DRD refers to mild to severe damage to retinal blood vessels caused by high blood glucose. 
EOM Extraocular motility; movement of the six muscles that, when functioning properly, allow the eyes to move and focus together in various directions. 
FAZ Foveal avascular zone; an area at the center of the retina that is devoid of blood vessels. 
HE Hard exudates; HEs are distinct white/yellow cholesterol deposits resulting from active or resolved DME. 
IOP Intraocular pressure; fluid pressure inside the eye that, if elevated, could be a sign of glaucoma. 
IRMA Intraretinal microvascular abnormality; one of the defining features of severe NPDR (see definition below), IRMAs are abnormal branching or widened retinal blood vessels that supply areas of nonperfusion in DRD. 
MA Microaneurysm; an early sign of DRD, MAs are small-vessel aneurysms resulting from weakening of capillary walls. 
NPDR Nonproliferative diabetes-related retinal disease; the more common form of DRD, NPDR is a condition in which the walls of retinal blood vessels weaken and sometimes leak fluid and blood into the retina, but new blood vessels are not yet growing (proliferating) in response to this damage. It is subclassified as mild, moderate, and severe and can also cause DME (see definition above). 
NVI Neovascularization of the iris; NVI occurs when new blood vessels grow in response to retinal ischemia, is associated with PDR (see definition below), and may cause spontaneous hyphema and neovascular glaucoma. 
NVD/NVE Neovascularization of the disk or elsewhere in the retina; NVD/NVE occurs when new blood vessels grow in response to retinal ischemia, is associated with PDR (see definition below), and may cause spontaneous vitreous hemorrhage. 
OCT Optical coherence tomography; an imaging test that uses light waves to take cross-section pictures of the retinal, OCT allows ECPs to see and measure the distinctive layers of the retina to diagnose and guide treatment of DRD and glaucoma. 
OCTA Optical coherence tomography angiography; OCTA is an imaging technique that uses laser light reflectance of the surface of moving red blood cells to accurately depict retinal vessels without the use of dye. 
PDR Proliferative diabetes-related retinal disease; PDR is the most advanced stage of DRD, characterized by the growth of new, fragile blood vessels in the retina (neovascularization). 
TRD Tractional retinal detachment; TRD is the separation of the neurosensory retina from the retinal pigment epithelium resulting from the traction caused by proliferative membranes present over the retinal surface or vitreous. 
UWF Ultra-widefield; UWF imaging provides a 200° panoramic image of the retina, allowing ECPs to better visualize and evaluate retinal abnormalities. 
VB Venous beading; a late-stage finding in NPDR that represents weakened walls of major retinal vessels, VB is one of the strongest predictors for progression to PDR. 
VH Vitreous hemorrhage; VHs are caused by bleeding from fine neovascular blood vessels in the eye. 

Retinal fundus photography (Figure 1) is considered the gold standard for DRD imaging, and recent advances in imaging technologies have significantly improved the ability to detect and treat DRD and maculopathy. Ultra-widefield imaging (Figure 2) provides a larger field of view, allowing ECPs to see more of the retina and detect peripheral changes, which in turn facilitates early detection of DRD and enhances patient education regarding the importance of screening and follow-up care.

FIGURE 1

Fundus photographs of eyes with nonproliferative DRD (A), proliferative DRD (B), and DME (C).

FIGURE 1

Fundus photographs of eyes with nonproliferative DRD (A), proliferative DRD (B), and DME (C).

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FIGURE 2

Ultrawide-field imaging of NPDR.

FIGURE 2

Ultrawide-field imaging of NPDR.

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The American Diabetes Association recognizes the potential of HCP clinic–based retinal photography with remote (telemedicine) review and interpretation by eye care experts as a way to overcome barriers to screening services in locations where qualified ECPs are not readily available (16). However, in-person exams are still necessary if retinal photos are of unacceptable quality and for follow-up if abnormalities are detected. Retinal photos are not a substitute for dilated comprehensive eye exams, which should be performed at least initially and at intervals thereafter as recommended by an ECP (16). U.S. Food and Drug Administration-approved artificial intelligence systems that detect more than mild DRD and DME are an alternative to traditional screening approaches. However, their benefits and optimal use have not yet been determined (16,40).

Optical coherence tomography (OCT) (Figure 3) has dramatically improved early detection and care of DRD and maculopathy. OCT allows for the early identification and management of DME. Based on OCT, DME is categorized as center-involved or non–center-involved. Center-involved DME is characterized by loss of foveal contour, cystoid macular edema involving the center of the fovea, neuro-sensory detachment involving the center of the fovea, and increased central subfield thickness. Non–center-involved DME is characterized by retinal thickening and/or cystic spaces not directly involving the center of the macula.

FIGURE 3

Spectral-domain OCT scan showing center-involved DME.

FIGURE 3

Spectral-domain OCT scan showing center-involved DME.

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OCT angiography (OCTA) (Figure 4) is another modern imaging test that can detect other vascular anomalies such as vascular loops, tortuosity, and dilations of the vessels, as well as intraretinal microvascular abnormalities and superficial neovascularization. It also detects diabetes-related macular ischemia, with clinical signs of paramacular 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 not only result in vision impairment, but also signify a poor prognosis because the condition cannot be treated.

FIGURE 4

OCTA image of the macula of a person with DRD. Vascular changes shown include microaneurysms (circle), enlarged FAZ (star), macular neovascularization (red arrow), microvascular tortuosity (blue arrow), and extensive capillary nonperfusion (yellow arrow).

FIGURE 4

OCTA image of the macula of a person with DRD. Vascular changes shown include microaneurysms (circle), enlarged FAZ (star), macular neovascularization (red arrow), microvascular tortuosity (blue arrow), and extensive capillary nonperfusion (yellow arrow).

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All people with severe nonproliferative diabetes-related retinal disease (NPDR), proliferative diabetes-related retinal disease (PDR), or DME should be referred to an ophthalmologist experienced in the management of DRD—even those with 20/20 vision and no visual complaints (16–18). Anti-vascular endothelial growth factor (VEGF) medications are the first-line treatment for most people with center-involved DME and PDR (41,42). In some cases of persistent edema after three to six injections, the retinal specialist may elect to switch anti-VEGF agents, add laser therapy, or initiate steroid treatment. For individuals with non–center-involved DME, the specialist may start treatment with focal laser therapy or anti-VEGF agents or decide on further observation if the vision is not compromised.

Reports of diabetes-related eye exams are an essential component of interprofessional communication between ECPs and HCPs who share patients with diabetes or prediabetes. These reports can be handwritten notes, forms developed and completed via an electronic medical record system, or based on templates obtained from various resources such as professional organizations. In addition to merely reporting their findings, ECPs should use these reports to alert HCPs if additional care such as a referral to a retinal specialist is warranted. Even when people have no notable ocular manifestations of diabetes upon examination, the ECP should still share a report to that effect in a timely manner.

Confronting the emerging epidemic of DRD and ensuring better ocular outcomes requires collaboration from all ECPs and HCPs involved in the care of people with diabetes. Bidirectional interprofessional communication is particularly important, and both ECPs and HCPs should be aware of their shared patients' overall medical status, individualized glycemic targets, and evolving eye health. Effective team care and ongoing communication can decrease the risk of sight-threating DRD, reduce systemic complications, improve clinical outcomes, and enhance quality of life for people with diabetes.

Editorial and project management services were provided by Debbie Kendall of Kendall Editorial in Richmond, VA.

Dualities of Interest

B.A.C. is a consultant for Genentech and Regeneron. S.A.R. is a speaker for Allergan, Inc., and VSP Vision Care. No other potential conflicts of interest relevant to this compendium were reported.

Author Contributions

All authors researched and wrote their respective sections. Lead author T.W.G. reviewed all content and is the guarantor of this work.

The opinions expressed are those of the authors and do not necessarily reflect those of VSP Vision Care, Regeneron, or the American Diabetes Association. The content was developed by the authors and does not represent the policy or position of the American Diabetes Association, any of its boards or committees, or any of its journals or their editors or editorial boards.

Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0 for details.