The effect of axial length on photodynamic therapy.
OBJECTIVE
To determine the effect of the axial length of the eye on photodynamic therapy (PDT) light fluence.


METHODS
Laboratory investigation.


METHODS
A calibrated Gullstrand-type model eye was used for this study. The axial length of the model eye was set to different values ranging from 20 to 31 mm, and the light fluence rate for treating a spot of 4 mm was recorded and compared with a fluence rate of 600 mW/cm2 with four indirect condensing laser lenses.


RESULTS
The axial length of the eye is inversely related to light fluence. From myopia to hyperopia, the total deviation from 600 mW/cm2 was -37.7% to +53.8% (Mainster Standard; Ocular Instruments Inc, Bellevue, Washington, USA), and -48.3% to +20.5% (Mainster Wide Field; Ocular Instruments Inc), -52.3% to +16.7% (Volk Transequator; Volk Optical Inc, Mentor, Ohio, USA), and -52.3% to +15.3% (Volk PDT Laser; Volk Optical Inc).


CONCLUSIONS
Axial length of the eye has a considerable effect on PDT light fluence rate in this model. These findings may be important for optimizing PDT, particularly in eyes with high refractive errors.
Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria. siamak.ansari-shahrezaei@meduniwien.ac.at
Siamak
S
Ansari-Shahrezaei
Erdem
E
Ergun
Michael
M
Stur
D001837:Body Weights and Measures; D005123:Eye / Q000033:anatomy & histology*; D006801:Humans; D007834:Lasers; D008954:Models, Biological; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000528:radiation effects / Q000627:therapeutic use; D011166:Porphyrins / Q000528:radiation effects / Q000627:therapeutic use; D000077362:Verteporfin
D017319:Photosensitizing Agents; D011166:Porphyrins; D000077362:Verteporfin