Laser Treatment for Diabetic Retinopathy: What to Expect

Types of Laser Used in Diabetic Retinopathy

Two distinct laser approaches are used in managing diabetic retinopathy, each with a different target and mechanism:

• Focal laser: Precisely targeted burns applied directly to individual leaking microaneurysms in the central macular region. Used for DMO where specific, identifiable point sources of leakage can be treated.
• Grid laser: A pattern of evenly spaced burns applied to areas of diffuse retinal thickening and leakage within the macular zone, rather than individual leaking points. Used when DMO is diffuse and microaneurysms cannot be individually identified.
• Panretinal photocoagulation (PRP): Hundreds to thousands of laser burns applied across the peripheral retina, away from the macula, to destroy ischaemic (oxygen-deprived) retinal tissue. This is the treatment for proliferative diabetic retinopathy. The destruction of peripheral retinal tissue reduces the total amount of VEGF being produced, which causes new retinal blood vessels to regress.

How Panretinal Photocoagulation Works

In proliferative diabetic retinopathy, chronic retinal ischaemia causes the retina to release large quantities of vascular endothelial growth factor (VEGF). This drives the growth of fragile, abnormal new blood vessels on the retinal surface and into the vitreous — a process called neovascularisation. These vessels bleed easily, causing vitreous haemorrhage and visual loss, and can form fibrous tissue that contracts and pulls the retina away from the eye wall (tractional retinal detachment).

PRP addresses the root cause: by destroying peripheral ischaemic retinal tissue with laser burns, the total VEGF output from the eye is dramatically reduced. This causes existing neovascular vessels to regress and prevents new ones from forming. The landmark Diabetic Retinopathy Study (DRS), published in 1976, established that PRP reduced the risk of severe vision loss from high-risk PDR by more than 50%.

The trade-off is that PRP permanently destroys peripheral retinal tissue. Patients typically notice some reduction in peripheral and night vision after treatment — an acceptable trade-off given the alternative of progressive sight-threatening neovascular complications.

What the Laser Procedure Involves

Retinal laser photocoagulation is an outpatient procedure performed without any incisions or general anaesthesia. Here is what to expect:

1. Pupil dilation:Dilating eye drops are instilled 20–30 minutes before the procedure to widen the pupil and allow access to the peripheral retina.
2. Topical anaesthetic: Anaesthetic drops numb the eye surface. A contact lens is placed on the eye to focus the laser beam and provide a view of the retina.
3. Laser delivery:Sitting at a slit lamp, your ophthalmologist directs the laser beam precisely at the target areas. Each burn takes a fraction of a second. A full PRP course involves 1,200–1,800 burns, typically delivered over 2–3 sessions.
4. Duration:Each session lasts approximately 15–45 minutes depending on the extent of treatment required.

During PRP, patients typically notice bright flashes of light with each burn. Some people experience a mild aching sensation, particularly during more peripheral burns. Topical anaesthetic drops are usually sufficient; in some cases a peribulbar or sub-Tenon’s block may be offered for additional comfort.

Side Effects of Laser Treatment

Laser photocoagulation is generally well tolerated, but patients should be aware of the following:

• Peripheral visual field loss (PRP):Each laser burn creates a small permanent scotoma. Across 1,200–1,800 burns, this results in a measurable constriction of the peripheral visual field. Driving standards in Australia require an adequate visual field, and patients should discuss any field concerns with their ophthalmologist.
• Reduced night vision (PRP): Destroying peripheral rod photoreceptors reduces low-light visual sensitivity. Patients should be counselled about this before treatment, particularly if they regularly drive at night.
• Temporary worsening of macular oedema (PRP): Post-laser inflammation can exacerbate DMO in the short term. Pre-treating DMO with anti-VEGF injections before PRP can mitigate this risk.
• Small permanent scotomas (focal/grid): Each burn leaves a small permanent blind spot. Careful planning minimises any impact on reading vision.

Focal/Grid Laser vs Panretinal Photocoagulation

For DMO, anti-VEGF injections now produce superior visual acuity outcomes compared to focal/grid laser alone, based on the DRCR.net Protocol I trial. Laser may still be used as an adjunct, particularly to reduce the number of injections required. For PDR, PRP remains the standard of care, valued for its durable single-treatment effect.

Conclusion

Laser photocoagulation has protected the vision of millions of people with diabetes over the past five decades. PRP remains the cornerstone treatment for high-risk proliferative diabetic retinopathy, delivering durable protection against vitreous haemorrhage and tractional detachment. For DMO, anti-VEGF injections have largely superseded focal/grid laser as the preferred first-line treatment due to superior vision outcomes, but laser retains an important complementary role. Understanding which treatment — or which combination — is right for your stage of disease is best achieved through a thorough consultation with your ophthalmologist.

Frequently Asked Questions