Effect of Loupes on Ocular Blue Light Hazard: Indirect Viewing

Objectives:

This study measured the effect magnification loupes have on the 'blue light hazard' when a curing light is viewed indirectly.

Methods:

Loupes with 3.5x magnification (Design for Vision [DFV], Carl Zeiss [CZ], Quality Aspirator [QA]), and 2.5x magnification (DFV and QA) with were tested over three days. The loupes were placed at the entrance to an integrating sphere connected to a spectrometer (USB 4000, Ocean Optics). A typodont with human teeth was placed 40cm away and in line with this sphere. A Sapphire Plus (Den-Mat) curing light was positioned at a 45 degree angle from the facial of tooth #9.

The spectral radiant power reflected from the teeth was recorded 5 times both with and without the loupes over the entrance into the sphere. The angular subtense of the experiment was 0.02 radians. The maximum permissible cumulative exposure times in an eight-hour day were calculated using guidelines set by the American Conference of Industrial Hygienists (ACGIH). Weighted blue light irradiance values were compared between the brands of loupes using Fisher's PLSD, α=0.05.

Results:

Weighted blue irradiance values were significantly different for each brand of loupe (p<0.05) and were up to 8 times greater at the pupil than without loupes. However, since the resulting images are now 2.5 to 3.5x larger on the retina, the effective blue light hazard was reduced compared to without the loupes.

Conclusions:

Without loupes, at 40cm distance, the maximum cumulative daily exposure time to light reflected from the tooth was approximately 10 minutes. This maximum is unlikely to be reached in the dental office. All the loupes increased the irradiance received at the pupil. Although the irradiance received by the eye was greater, the maximum cumulative daily exposure time was increased. Further studies are required on the ocular hazards of loupes and the effects of other curing lights.