3D Visualization System Reduces Retinal Light Hazard During Macular Surgery

A digital 3-dimensional (3D) visualization system exposes fewer patients to retinal light hazard during macular surgery than a conventional microscope, according to research published in Retina. However, the report shows no significant visual acuity differences between patients who underwent a procedure using the 3D system and those for whom surgeons used a conventional microscope.

Researchers investigated the retinal light hazard during macular surgery using a scenario-based study of the typical settings used during macular surgery as well as a retrospective evaluation of a case-control study.

The case-control study included patients who underwent pars plana vitrectomy (PPV) for epiretinal membrane using the 3D and conventional microscopy.

For scenario study, the investigators measured the spectral irradiances of endoilluminators for settings used during core vitrectomy and macular manipulations with the 3D and conventional microscopy. 

For the retrospective study, they extracted times needed for core vitrectomy and macular manipulations from the medical records of patients and calculated the total retinal light hazard index (THI) and macular hazard index (MHI) based on the spectral irradiances weighted by standard functions. 

The main outcome measures were THI, MHI, and the number of cases that exceeded the maximum permissible radiant power exposure. The researchers compared the values between the 3D and conventional-microscopy groups.

In the scenario study, the researchers found that the spectral irradiances were 1.6 and 3.9 mW/cm² for core vitrectomy and 3.4 and 8.1 mW/cm² for macular manipulations using typical settings for the 3D and conventional-microscopy groups, respectively. 

In the retrospective case-control study, there were 20 patients (mean age, 70.4±9.6 years) in the 3D group and 10 patients (mean age, 68.2±6.0 years) in the conventional-microscopy group.

The researchers found that the median THI was 7.35 ± 3.19 kJ/m² (range, 4.31-17.37) in the 3D group and 17.68±5.49 kJ/m² (range, 11.09-27.70) in the conventional-microscopy group (P <.0001). They reported that the median MHI was 5.41±2.94 kJ/m² (range, 2.93-14.58) in the 3D group and 14.03±5.36 kJ/m² (range, 6.84-23.55) in the conventional-microscopy group (P <.001). The threshold limits were exceeded in 5% and 60% of PPV cases in the 3D and conventional-microscopy groups, respectively (P <.05).

“The light-induced retinal toxicity (retinal photopic injury) is a well-known complication during ocular surgeries. Since the short wavelength visible light contributes to retinal hazard, blue- and ultraviolet-light filters have been equipped in the operating microscopes and endoilluminators to minimize the toxicity during the surgery,” according to the investigators. 

The primary limitations of the study included the retrospective design and relatively small sample size.