Comparison of laser beam intensity profiles produced by photodynamic therapy (PDT) and transpupillary thermotherapy (TTT) lasers.
OBJECTIVE
For photodynamic therapy (PDT) or transpupillary thermotherapy (TTT) lasers, long irradiation time (typically 1 minute or longer) is used and a large area of retina is treated. Consequently, the power stability but also the light distribution within the laser beam plays a major role. This study aimed to evaluate beam intensity profiles produced by several PDT and TTT lasers.


METHODS
A beam profile analyzer (Cohu 4812 camera connected to a LPA-300PC, Spiricon, Logan, UT) was used to compare the beam profiles of PDT lasers: OPAL (Lumenis, USA); ACTIVIS (Quantel Medical, France), VISULAS (Zeiss, Germany). Spots of 2, 3, 4, and 5 mm were tested with each laser. Similarly, TTT lasers: OCULIGHT SLx (Iridex, CA) and IRIDIS trade mark (Quantel Medical, France) were evaluated with 2 and 3 mm spot diameter and power ranging from 200 to 1,000 mW.


RESULTS
PDT lasers: OPAL had a "top hat" and homogeneous profile whatever the spot size. Numerous micro-spikes and micro-nadirs of power were observed with the ACTIVIS and the VISULAS. TTT lasers: for the IRIDIS the beam shape was rather gaussian, but the homogeneity was reduced by micro-spikes of power. With the OCULIGHT Slx the beam shape was rather top hat and only few micro-spikes or micro-nadirs of power could be disclosed.


CONCLUSIONS
The literature tends to prove that the shape and homogeneity of the beam profile could play a role on the efficacy of the treatment.


CONCLUSIONS
Since PDT and TTT lasers display different beam profiles, this parameter should be carefully evaluated when performing clinical evaluations of PDT or TTT treatments.
Desmettre
Thomas J
TJ
EA 2689, INSERM IFR 114, Pavillon Vancostenobel, Lille University Hospital, 59037 Lille Cedex, France. desmettre@lille.inserm.fr
Mordon
Serge R
SR
D017075:Laser Coagulation / Q000295:instrumentation; D008027:Light; D028022:Low-Level Light Therapy / Q000295:instrumentation*; D010778:Photochemotherapy / Q000295:instrumentation*; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011166:Porphyrins / Q000627:therapeutic use; D012164:Retinal Diseases / Q000628:therapy; D000077362:Verteporfin
D017319:Photosensitizing Agents; D011166:Porphyrins; D000077362:Verteporfin