Diabetic Eye Disease - Why Time in Range Matters

Clear vision supports independence, connection, and quality of life. For people living with diabetes, protecting eye health is closely linked to how much time glucose levels spend in range and how often they move out of range over months and years.

Understanding diabetic eye disease, the differences between type 1 and type 2 diabetes, and the early signs of diabetic retinopathy empowers people to take informed, supported steps to protect their sight.

What is Diabetic Eye Disease?

Diabetic eye disease refers to a group of conditions that can affect the eyes when glucose levels spend too much time outside a person’s target range. These include diabetic retinopathy, diabetic macular oedema, cataracts, and glaucoma. The most common is diabetic retinopathy.

When glucose levels are frequently out of range, especially over long periods, the small blood vessels supplying the retina can become stressed. Over time, these vessels may leak or become fragile, affecting the retina’s ability to process visual information accurately.

It’s important to be clear: diabetic eye disease is not caused by a lack of effort. Time out of range reflects many factors, including insulin availability, insulin sensitivity, hormones, illness, stress, access to care, technology, medications, and social circumstances.

Time in Range: A Modern Way to Understand Risk

Time in Range (TIR) refers to the percentage of time glucose levels stay within an agreed target range, usually 4.0 - 8.0 mmol/L for many adults (individual targets may differ). Time Out of Range (TOR) includes time spent above or below this range.

Research consistently shows that more time in range is associated with a lower risk of developing diabetic retinopathy or progression of eye changes, while higher time out of range - particularly above range - can increase risk. This makes TIR a meaningful, practical way to think about eye health over time.

Type 1 and Type 2 Diabetes: Different Pathways, Shared Eye Health Priorities

Both type 1 diabetes and type 2 diabetes can affect eye health, and both require ongoing attention to time in range and time out of range. While the biological pathways into diabetes differ, the eyes respond to glucose exposure in the same way, regardless of diabetes type.

Type 1 diabetes is an autoimmune condition in which insulin is no longer produced by the body. From diagnosis, glucose levels require support with insulin therapy. Variations in glucose—particularly extended periods out of range—can place stress on the small blood vessels of the retina, making regular screening and glucose pattern review essential.

Type 2 diabetes develops when the body becomes less responsive to insulin and may not produce enough insulin to meet its needs. Many people experience significant time out of range before diagnosis, which is why eye screening is recommended at diagnosis and reviewed regularly thereafter.

Importantly, diabetes type does not determine eye outcomes. What matters most for eye health is how often glucose levels spend within a person’s agreed target range over time, combined with timely access to eye screening, appropriate treatment, and multidisciplinary support.

Clinical Manifestations of Type 2 Diabetes

Type 2 diabetes often develops gradually, and early signs may be subtle or fluctuate. Common clinical manifestations include:

• Increased thirst
• More frequent urination
• Fatigue
• Blurred or changing vision
• Slow healing wounds or infections
• Tingling or numbness in hands or feet

Vision changes can occur when glucose levels move in or out of range more often than usual, causing temporary shifts in the eye’s lens. While these changes are often reversible, they are an important signal to seek assessment and review glucose patterns.

Diabetic Retinopathy: How It Develops

Diabetic retinopathy develops when repeated or prolonged time out of range affects the tiny blood vessels in the retina.

In early stages (non proliferative diabetic retinopathy), vessels may weaken or leak. In later stages (proliferative diabetic retinopathy), new, fragile vessels can form, increasing the risk of bleeding inside the eye.
Diabetic macular oedema occurs when fluid collects in the macula, the area responsible for sharp central vision. This can develop at any stage of retinopathy.

The reassuring reality is that regular screening and early treatment are highly effective at preserving vision, even when changes are detected.

Symptoms of Diabetic Retinopathy

One of the challenges with diabetic retinopathy is that early stages usually have no symptoms. Vision may seem fine despite changes already occurring.

As the condition progresses, symptoms may include:

• Blurred or distorted vision
• Fluctuating vision linked to time out of range
• Dark spots or floaters
• Difficulty seeing at night
• Areas of vision loss

Sudden changes—such as a shower of floaters or a shadow across vision—require urgent assessment.

Protecting Eye Health: A Team Based Approach

Maintaining eye health is a shared effort supported by a multidisciplinary care team. People living with diabetes benefit from coordinated care involving:

• General Practitioner (GP) – overall health monitoring and referrals
• Credentialled Diabetes Educator (CDE) – diabetes self management education focused on TIR and pattern recognition
• Endocrinologist or physician – medical management where required
• Optometrist – routine retinal screening
• Ophthalmologist – specialist treatment of eye disease
• Dietitian – personalised nutrition support that helps reduce time out of range
• Exercise physiologist – tailored physical activity to support glucose stability.

In Australia, most people are advised to have an eye check at diagnosis and at least every one to two years, or more often if changes are present.

Looking Forward with Confidence

Diabetic eye disease is common, but vision loss is not inevitable. Increasing time in range, reducing time out of range, and attending regular eye checks can significantly protect long term vision.
Eye screening is not about finding fault—it’s about early support, effective treatment, and preserving what matters most. With the right care team and a focus on time in range over time, most people living with diabetes can maintain healthy vision and confidence in their future.

How Westfund members can access support

Westfund members may have access to a range of products and services that support diabetes self -management and eye health, including:

• Extras benefits for allied health providers such as Credentialed Diabetes Educators, Accredited Practicing Dietitians, and Exercise Physiologists for eligible members
• Health and wellbeing programs that support diabetes self management 

Using these benefits can help Westfund members take proactive steps to help protect their eyes, support overall health and maintain quality of life.

The information provided is general in nature and does not replace professional medical advice. Waiting periods, limits and eligibility criteria apply. Benefits and programs are subject to your level of cover and annual limits. Please refer to your Policy Summary or check your Extras limits via Members Online or the Westfund app for full details.