Knowing when to use laser therapy or injection therapy-either together or stand-alone-for diabetic macular edema is a crucial decision for the ophthalmologist.
By Manish Nagpal, MD, Special to Ophthalmology Times
Gujarat, India-When treating diabetic macular edema (DME), ophthalmologists often face the choice of which treatments should be used-either alone or in combination-that best prevent further damage to the retina, correct vision loss, and prevent eventual blindness.
Many tools are available for treating DME and edema in general-two of which I have found to be successful: laser therapy, which has been proven to be extremely effective, and anti-vascular endothelial growth factor (VEGF) injections, which should be used moderately due to potential risk factors.
In certain cases, these two treatments can be used together. In others, they are better suited as stand-alone procedures.
When assessing a patient with DME, I first determine how diffuse is the edema. I examine the eye using ocular coherence tomography (OCT). If the edema is not diffuse, I usually treat the eye with laser therapy alone using pattern scanning laser treatment with algorithm-based software (Endpoint Management, Topcon Medical Laser Systems). The software applies a user-defined percentage of the titration burn to deliver non-destructive laser treatment that can utilize a grid for more accurate burn patterns.
The software has a feature called “Landmarks” that can outline the macular grid with a few visible endpoints and allow me to see where I have applied the laser, even though most of the treatment is not ophthalmoscopically visible. This gives confidence that I have treated the entire area, and do not run the risk of overlapping burns or missing an important area.
If examination reveals that the edema is not well defined and in small areas, or more diffuse, I combine laser therapy and injections for the best possible results. One of the benefits of combination therapy is that the frequency of anti-VEGF injections can be reduced, which means less risk of side effects or complications to the patient.
I also use combination therapy in cases of macular edema due to branch vein occlusion. For a patient with acute branch vein occlusion, I recommend three anti-VEGF treatments over the course of a month. At the second injection appointment, I perform a mild grid laser to the area using a 30% to 40% setting. In this case, I don’t want to achieve a dense white burn. I just want to “tickle” the retinal pigment epithelium (RPE) cells so that they help regress the edema faster.
Several cases illustrate this technique and treatment paradigm.
Case 1: A 50-year-old diabetic male presented with a reduction in vision to about 20/80, which had occurred over the course of 1 month. During examination, I discovered circinates in the eye and some hemorrhages temporal to the fovea. I ordered an OCT, which revealed significant cystoid macular edema. I advised a combination of anti-VEGF injections and grid laser, which was performed using 100 μm spot burns at 200 mW power titration and a setting of 40%. I applied a semi-circular grid pattern and followed this with an injection of ranibizumab (Lucentis, Genentech). At the 1-month visit, the patient had good regression of the edema and his visual acuity had improved to 20/20. At the 4-month postoperative visit, he remained stable.
Case 2: A 52-year-old diabetic female had a noticeable decrease in vision in her right eye. At the time of her initial evaluation, her vision was 20/200, and a fundus evaluation revealed diffuse macular edema and hemorrhages around the macular area. I also advised her to return for combination treatments. Grid laser was performed using 100 μm size spots with a 30% setting and 200 mW power. I followed her laser treatment with a ranibizumab injection. At her 1-month follow-up appointment her vision had improved to 20/20 and her edema had regressed significantly.
Case 3: The vision of a 60-year-old diabetic male had been reduced in the month prior to his initial consultation to 20/80. It was determined that he had circinates and hemorrhages temporal to the fovea. I performed an OCT, which revealed a normal foveal contour with no cystoid edema.
In this case I recommended only grid and focal laser treatment. I used the semicircular grid spot burns at 150 mW at a 20-millisecond duration with a 30% to 40% setting. At his 1-month appointment the patient had good regression of his edema and his visual acuity had improved to 20/20. He returned for follow-up appointments for 6 months and his macular edema condition has been stable to date.
In the past, patients have been nervous about receiving injection therapy. As it grows into a more common practice in treating DME, however, patients are becoming more comfortable with this method of treatment.
In any situation, the physician must advise the best possible regimen and utilize the best tools and instruments. As knowledge of lasers and medications advance, we should adjust our treatment protocols accordingly. I have experienced great success with my patients with thoughtful diagnosis and treatment plans, combined with cutting-edge equipment.