COMBINATION THERAPY OF INTRAVITREAL RANIBIZUMAB AND SUBTHRESHOLD MICROPULSE PHOTOCOAGULATION FOR MACULAR EDEMA SECONDARY TO BRANCH RETINAL VEIN OCCLUSION: 6-MONTH RESULT

This study suggests that the combination therapy of intravitreal ranibizumab and 577-nm subthreshold micropulse photocoagulation can treat macular edema secondary to macular edema secondary to branch retinal vein occlusion effectively, by decreasing the frequency of intravitreal ranibizumab injections than intravitreal ranibizumab monotherapy while maintaining good visual acuity at 6 months.

Purpose:

To determine the efficacy of the combination therapy of intravitreal ranibizumab (IVR) and 577-nm yellow laser subthreshold micropulse laser photocoagulation (SMLP) for macular edema secondary to branch retinal vein occlusion cystoid macular edema.

Methods:

Retrospective, consecutive, case–control study. Forty-six eyes of 46 patients with treatment-naive branch retinal vein occlusion cystoid macular edema were enrolled. The IVR + SMLP group consisted of 22 patients who had undergone both SMLP and IVR. Intravitreal ranibizumab group consisted of 24 patients who had undergone IVR monotherapy. Intravitreal ranibizumab therapy was one initial injection and on a pro re nata in both groups, and SMLP was performed at 1 month after IVR in the IVR + SMLP group. Preoperatively and monthly, best-corrected visual acuity and central retinal thickness were evaluated using swept source optical coherence tomography.

Results:

Best-corrected visual acuity and central retinal thickness significantly improved at 6 months in IVR + SMLP and IVR groups. Best-corrected visual acuity and central retinal thickness were not significantly different between the two groups at any time points. The number of IVR injections during initial 6 months in IVR group (2.3 ± 0.9) was significantly greater (P = 0.034) than that in IVR + SMLP group (1.9 ± 0.8).

Conclusion:

The combination therapy of IVR and SMLP can treat branch retinal vein occlusion cystoid macular edema effectively, by decreasing the frequency of IVR injections while maintaining good visual acuity.

Online optical coherence tomography during subthreshold laser irradiation

PURPOSE

To investigate the role of real-time optical coherence tomography (OCT) in the detection of standard and nonvisible subthreshold laser irradiation.

METHODS

We used an integrated platform consisting of a slit-lamp, a digital camera, a slit-lamp mounted OCT, and a 532-nm laser photocoagulator (Topcon Inc., Tokyo, Japan). The laser aiming beam and the OCT scan were aligned to obtain real-time tomographic imaging of the irradiated area during laser exposure. Standard and subthreshold laser irradiation and simultaneous OCT acquisition were tested in artificial and biological samples. Laser testing cards were chosen as artificial samples. Freshly enucleated pig eyes were used for iris irradiation.

RESULTS

Ophthalmoscopically visible reference burns were placed on the laser testing card in 2 parallel lines. Then, a series of laser spots with the same size and duration but different power were placed between the reference burns. Online OCT during laser irradiation detected changes in the reflectivity profile of the artificial sample at a power of 200 mW, in absence of ophthalmoscopically visible lesions. Similarly, reference burns were placed on pig iris and between them various laser spots were performed at ranging powers. Changes in the iris optical properties, as detected with online OCT, were produced with a power of 860 mW in absence of visible endpoint.

CONCLUSIONS

Online OCT is able to identify non-ophthalmoscopically visible lesions during subthreshold laser irradiation either in artificial samples or in pig iris.

Angiographic effects of indocyanine green photobleaching by the diode laser

BACKGROUND AND OBJECTIVE

To investigate the cause of hypofluorescent spots detected by indocyanine green (ICG) videoangiography in areas subjected to ICG-enhanced transpupillary thermotherapy in pigmented rabbits.

MATERIALS AND METHODS

In 6 eyes, two similar areas were treated with transpupillary thermotherapy. A standard dose of ICG (0.5 mg/kg) was injected intravenously before treatment of the second area. Red-free photographs without further injection of ICG (first ICG videoangiography) were then performed. The first area was re-irradiated using the same parameters. Red-free photographs and a second ICG videoangiography, still without further injection of ICG, were performed. ICG was then re-injected and a third ICG videoangiography was obtained. Finally, fluorescein angiography was performed.

RESULTS

The first ICG videoangiography demonstrated hyperfluorescence of the first area and normofluorescence of the second area. The second ICG videoangiography demonstrated hypofluorescence of the first area. The third ICG videoangiography showed hyperfluorescence of both areas.

CONCLUSIONS

Hypofluorescence detected after re-irradiation is probably related to ICG photobleaching.

Evolution of retinal laser therapy: minimum intensity photocoagulation (MIP). Can the laser heal the retina without harming it?

Laser photocoagulation is a photo-thermal therapy validated by landmark studies and commonly accepted as the standard of care for various retinal diseases. Although its mechanism of action is still not completely understood, it is normally administered with visible endpoints, true intra-retinal burns that cause chorioretinal scars, which, with time, evolve into expanding areas of atrophy. New hypotheses on the mechanism of action of laser photocoagulation suggest that its therapeutic benefits derive from biologic activities that cannot be inducted within the "burned" area of photocoagulation necrosis, but that occur in the adjacent surrounding areas affected by a lower, sub-lethal, photo-thermal elevation. Thus, the iatrogenic chorioretinal damage caused by visible endpoint photocoagulation may be redundant and an equally effective laser therapy could be administered with minimum intensity photocoagulation (MIP) using laser protocols aiming to create only non-lethal photo-thermal elevations with no intraoperative visible endpoint. It is the purpose of this paper to review laser techniques and clinical protocols that have been utilized to administer retina-sparing MIP treatments that hold the promise of healing the retina while minimizing the iatrogenic harm.

Subthreshold and micropulse diode laser photocoagulation

Retinal laser photocoagulation is a proven, effective treatment for various retinal disorders. Common clinical protocols use intra-operatively visible endpoints that cause iatrogenic chorioretinal damage. For this reason, laser therapy is normally limited to levels of disease severity for which the benefit-to-risk ratio justifies its application. The use of 810 nm diode lasers in the MicroPulse mode offers the surgeon the possibility to minimize iatrogenic retinal damage. A less destructive laser therapy with a more favorable benefit-to-risk ratio could justify treatment earlier in the course of the disease, allowing for stabilization or improvement of less compromised visual functions.