Laser photocoagulation control of diabetic macular oedema without fluorescein angiography

Diabetic macular edema: Evidence-based management

Diabetic macular edema (DME) is the most common cause of vision loss in patients with diabetic retinopathy with an increasing prevalence tied to the global epidemic in type 2 diabetes mellitus. Its pathophysiology starts with decreased retinal oxygen tension that manifests as retinal capillary hyperpermeability and increased intravascular pressure mediated by vascular endothelial growth factor (VEGF) upregulation and retinal vascular autoregulation, respectively. Spectral domain optical coherence tomography (SD-OCT) is the cornerstone of clinical assessment of DME. The foundation of treatment is metabolic control of hyperglycemia and blood pressure. Specific ophthalmic treatments include intravitreal anti-VEGF drug injections, intravitreal corticosteroid injections, focal laser photocoagulation, and vitrectomy, but a substantial fraction of eyes respond incompletely to all of these modalities resulting in visual loss and disordered retinal structure and vasculature visible on SD-OCT and OCT angiography. Efforts to close the gap between the results of interventions within randomized clinical trials and in real-world contexts, and to reduce the cost of care increasingly occupy innovation in the social organization of ophthalmic care of DME. Pharmacologic research is exploring other biochemical pathways involved in retinal vascular homeostasis that may provide new points of intervention effective in those cases unresponsive to current treatments.

A Quantitative Approach to Predict Differential Effects of Anti-VEGF Treatment on Diffuse and Focal Leakage in Patients with Diabetic Macular Edema: A Pilot Study

Purpose

We use semiautomated segmentation of fluorescein angiography (FA) to determine whether anti-vascular endothelial growth factor (VEGF) treatment for diabetic macular edema (DME) differentially affects microaneurysm (MA)–associated leakage, termed focal leakage, versus non-MA–associated leakage, termed diffuse leakage.

Methods

We performed a retrospective study of 29 subjects treated with at least three consecutive injections of anti-VEGF agents for DME (mean 4.6 injections; range, 3–10) who underwent Heidelberg FA before and after anti-VEGF therapy. Inclusion criteria were macula center involving DME and at least 3 consecutive anti-VEGF injections. Exclusion criteria were macular edema due to cause besides DME, anti-VEGF within 3 months of initial FA, concurrent treatment for DME besides anti-VEGF, and macular photocoagulation within 1 year. At each time point, total leakage was semiautomatically segmented using a modified version of our previously published software. Microaneurysms were identified by an expert grader and leakage within a 117 μm radius of each MA was classified as focal leakage. Remaining leakage was classified as diffuse leakage. The absolute and percent changes in total, diffuse, and focal leakage were calculated for each subject.

Results

Mean pretreatment total leakage was 8.2 mm² and decreased by a mean of 40.1% (P < 0.0001; 95% confidence interval [CI], [−28.6, −52.5]) following treatment. Diffuse leakage decreased by a mean of 45.5% (P < 0.0001; 95% CI, [−31.3, −59.6]) while focal leakage decreased by 17.9% (P = 0.02; 95% CI, [−1.0, −34.8]). The difference in treatment response between focal and diffuse leakage was statistically significant (P = 0.01).

Conclusions

Anti-VEGF treatment for DME results in decreased diffuse leakage but had relatively little effect on focal leakage as assessed by FA. This suggests that diffuse leakage may be a marker of VEGF-mediated pathobiology. Patients with predominantly focal leakage may be less responsive to anti-VEGF therapy.

Translational Relevance

Fluorescein angiography can define focal and diffuse subtypes of diabetic macular edema and these may respond differently to anti-VEGF treatment.

DIABETIC MACULAR EDEMA

Diabetic macular edema (DME) remains the most common cause of vision loss among diabetic patients. New understanding of the underlying pathophysiology has interest in the potential benefits of the specific pharmacologic therapy, such as treatment with intraocular steroids, anti-vascular endothelial growth factor (VEGF), and protein kinase C-beta (PKCβ) inhibition. At the last time, laser photocoagulation, according to the guidelines of the Early Treatment of Diabetic Retinopathy Study (ETDRS), continues to be primary standard care treatment in most communities. Optical coherence tomography (OCT) is very useful in monitoring macular edema progression and response to treatment.

The course of response to focal/grid photocoagulation for diabetic macular edema

PURPOSE

The purpose of this study was to determine whether eyes with center-involved diabetic macular edema, treated with focal/grid photocoagulation, in which there is a reduction in central subfield thickness (CST) measured with optical coherence tomography after 16 weeks, will continue to improve if retreatment is deferred.

METHODS

This is a prospective, multicenter, observational, single-group focal/grid photocoagulation study of 122 eyes with center-involved diabetic macular edema (optical coherence tomography CST > or =250 microm). At the 16-week visit and continuing every 8 weeks, eyes were assessed for retreatment and additional laser treatment was deferred if the visual acuity letter score improved > or =5 letters or optical coherence tomography CST decreased > or =10% compared with the visit 16 weeks prior.

RESULTS

Of the 115 eyes that completed the 16-week visit, 54 (47%) had a decrease in CST by > or =10% compared with baseline. Of these, 26 (48%) had a CST > or =250 microm at 16 weeks and were evaluable at 32 weeks. Eleven (42%; 95% confidence interval, 23-63%) of the 26 eyes had a further decrease in CST > or =10% from 16 weeks to 32 weeks without further treatment.

CONCLUSION

Sixteen weeks after focal/grid laser for diabetic macular edema in eyes with a definite reduction, but not resolution, of central edema, 23% to 63% likely will continue to improve without additional treatment.

Diabetic macular edema: what is focal and what is diffuse?

PURPOSE

To review the available information on classification of diabetic macular edema (DME) as focal or diffuse.

DESIGN

Interpretive essay.

METHODS

Literature review and interpretation.

RESULTS

The terms focal diabetic macular edema and diffuse diabetic macular edema frequently are used without clear definitions. Published definitions often use different examination methods and often are inconsistent. Evaluating published information on the prevalence of focal and diffuse DME, the responses of focal and diffuse DME to treatments, and the importance of focal and diffuse DME in assessing prognosis is hindered because the terms are used inconsistently. A newer vocabulary may be more constructive, one that describes discrete components of the concepts such as extent and location of macular thickening, involvement of the center of the macula, quantity and pattern of lipid exudates, source of fluorescein leakage, and regional variation in macular thickening and that distinguishes these terms from the use of the term focal when describing one type of photocoagulation technique. Developing methods for assessing component variables that can be used in clinical practice and establishing reproducibility of the methods are important tasks.

CONCLUSIONS

Little evidence exists that characteristics of DME described by the terms focal and diffuse help to explain variation in visual acuity or response to treatment. It is unresolved whether a concept of focal and diffuse DME will prove clinically useful despite frequent use of the terms when describing management of DME. Further studies to address the issues are needed.

Diabetic retinopathy: an update

Diabetes mellitus is a major cause of avoidable blindness in both the developing and the developed countries. Significant technological advances have taken place to improve the diagnostic accuracy of diabetic retinopathy. In the last three decades, the treatment strategies have been revised to include, besides laser photocoagulation, early surgical interventions and pharmacotherapies.

The importance of fluorescein angiography in planning laser treatment of diabetic macular edema

OBJECTIVE

To test the hypothesis that pretreatment fluorescein angiography (FA) is not necessary for effective laser treatment of patients with clinically significant diabetic macular edema (CSME).

DESIGN

Prospective, randomized, controlled treatment simulation.

PARTICIPANTS

Six fellowship trained retina specialists.

INTERVENTION

The authors compared the ability of four retina specialists (observers) to plan laser treatment with and without the use of FA. One hundred consecutive cases of CSME were selected, each case consisting of a stereo pair of color photographs and a corresponding fluorescein angiogram. These cases were first read by two retina specialists who reached consensus on a treatment plan for each case (standard map). Each of the 4 observers reviewed 50 of these cases on 2 occasions and plotted 2 sets of treatment maps, 1 set created with and 1 without the aid of FA. Each observer's 100 treatment maps were graded for accuracy by comparing them to the corresponding standard maps. The role of FA in improving the accuracy of treatment maps was evaluated using logistic regression analysis to control for different observers, different cases, and different posterior pole characteristics.

MAIN OUTCOME MEASURES

Accuracy was defined as the proportion of standard treatment correctly treated by the observer.

RESULTS

For the observers as a group, the use of FA improved treatment planning accuracy from 49% to 54.5% (P = 0.02); however, there was significant interobserver variation in performance (P < 0.001). Treatment planning accuracy without and with FA was as follows: observer 1, 40.8% and 40.2%; observer 2, 49.8% and 72%; observer 3, 56.1% and 59.5%; and observer 4, 49.2% and 46.4%.

CONCLUSION

The use of FA improves the accuracy of treatment planning for CSME. The authors' study supports the use of FA in laser treatment of patients with CSME.