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The effect of digital measurement software on photodynamic therapy
Siamak Ansari-Shahrezaei1, Erdem Ergun, Michael Stur
1Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria. siamak.ansari-shahrezaei@meduniwien.ac.at
Background:
To investigate the effect of refraction-corrected digital measurement software on photodynamic therapy (PDT) treatment spot size.
Methods:
Experimental study using a calibrated Gullstrand-type model eye. The axial length of the model eye was set to different values, ranging from 20 to 31 mm, and the PDT treatment spot sizes obtained from refraction-corrected digital measurement software and manual measurement with a fixed-magnification factor, as well as four different indirect contact laser lenses, were calculated and compared for a treatment spot with a diameter of 4 mm.
Results:
The maximum deviation from the treating laser spot was +39.6% under myopic and +17.4% under hyperopic conditions when the refraction-corrected digital measurement software was used. The maximum deviation was +14.2% under myopic and +13.3% under hyperopic conditions when the manual measurement with the fixed-magnification factor was used.
Conclusions:
The use of refraction-corrected digital measurement software produces a larger deviation from treating laser spot than the use of manual measurement with a fixed-magnification factor. Therefore, refraction-corrected digital measurement software might not be suitable for calculating the recommended PDT treatment spot size in eyes with high refractive errors.
