A masking device and method to create custom laser exposure patterns for verteporfin photodynamic therapy

Purpose: To demonstrate a method for creating individualized laser exposure patterns for verteporfin photodynamic therapy (PDT) for peripapillary, juxtafoveal, and irregularly shaped lesions. Methods: Laser beams from commercially available PDT lasers (Lumenis Opal [Lumenis, Inc., Yokneam, Israel (formerly Coherent Medical Group, Palo Alto, CA)] and Zeiss Visulas 690s [Carl Zeiss Jena GmbH, Jena, Germany] were masked using different patterns and household materials. The masking was tested for percentage of light transmission, fluence rate across the masked treatment area, and intensity drop-off at the edge of the mask. Results: Of the materials tested, electrical tape was completely opaque, black card stock allowed 0.6% measured transmission, and yellow paper allowed 18% transmission of laser light. For the Lumenis Opal laser, the ratio of mask size to image size at the slit-lamp focal plane was 1:1. For the Zeiss Visulas laser, the ratio was 2:1; however, the exact ratio of the mask size to the image size was dependent on the spot size setting used. Unmasked areas of laser light had the expected fluence rate (i.e., no masking effect). The intensity drop-off at the mask edge was equivalent to the edge of the unmasked beam. Conclusion: Masks that individualize laser exposure patterns during PDT would allow safe treatment of irregular lesions and limit exposure of healthy tissue to risks of treatment.