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Magnification-corrected photodynamic therapy

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Graefe's Archive for Clinical and Experimental Ophthalmology Aims and scope Submit manuscript

Abstract

Background

To present a method for performing photodynamic therapy (PDT) with a constant predictable light fluence based on actual laser spot magnification.

Methods

A calibrated Gullstrand-type model eye with a scale of half circles in the centre of the artificial fundus 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 actual laser spot magnification of four indirect condensing laser lenses were determined using a PDT laser unit.

Results

Equations for determining the actual laser spot magnification were calculated for each laser lens. The total change in laser spot magnification from hyperopia (axial length 20 mm) to myopia (axial length 31 mm) was −20% to +24.8% for Mainster Standard lens (Ocular Instruments Inc, Bellevue, Washington, USA), −15.7% to +27.7% for Mainster Wide Field lens (Ocular Instruments Inc), −16.3% to +33.1% for Volk Transequator lens (Volk Optical Inc, Mentor, Ohio, USA), and −19.2% to +24.4% for Volk PDT Laser lens (Volk Optical Inc).

Conclusions

Axial length of the eye has a considerable effect on PDT laser spot magnification when an indirect laser lens is used. By calculating the actual laser spot magnification in conjunction with knowledge of the true greatest linear dimension of the neovascular lesion, the clinician may be able to deliver a constant predictable amount of light fluence to the fundus independent of the axial length of the PDT treating eye.

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Acknowledgement

The authors thank Bernhard Rassow for providing the model eye.

Author information

Authors and Affiliations

  1. Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, A-8036, Graz, Austria

    Siamak Ansari-Shahrezaei & Andreas Wedrich

  2. Moorfields Eye Hospital, London, United Kingdom

    Siamak Ansari-Shahrezaei, Robert Chong & Adnan Tufail

  3. Department of Ophthalmology, Sanatorium Hera, Vienna, Austria

    Erdem Ergun

  4. Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria

    Michael Stur

Authors
  1. Siamak Ansari-Shahrezaei
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  2. Erdem Ergun
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  3. Robert Chong
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  4. Adnan Tufail
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  5. Andreas Wedrich
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  6. Michael Stur
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Corresponding author

Correspondence to Siamak Ansari-Shahrezaei.

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The authors have no financial interest in any of the products discussed in this article.

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Ansari-Shahrezaei, S., Ergun, E., Chong, R. et al. Magnification-corrected photodynamic therapy. Graefe's Arch Clin Exp Ophthalmol 245, 333–337 (2007). https://doi.org/10.1007/s00417-006-0419-y

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  • DOI: https://doi.org/10.1007/s00417-006-0419-y

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