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Magnification-corrected photodynamic therapy

  • Siamak Ansari-ShahrezaeiEmail author
  • Erdem Ergun
  • Robert Chong
  • Adnan Tufail
  • Andreas Wedrich
  • Michael Stur
Perspective

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.

Keywords

Photodynamic therapy Light fluence Choroidal neovascularization 

Notes

Acknowledgement

The authors thank Bernhard Rassow for providing the model eye.

References

  1. 1.
    Age-Related Eye Disease Study Research Group (2000) Risk factors associated with age-related macular degeneration. A case-control study in the age-related eye disease study: Age-Related Eye Disease Study Report Number 3. Ophthalmology 107:2224–2232CrossRefGoogle Scholar
  2. 2.
    Altman DG, Bland JM (1983) Measurement in medicine: the analysis of method comparison studies. Statistician 32:307–317CrossRefGoogle Scholar
  3. 3.
    Ansari-Shahrezaei S, Stur M (2005) Magnification-corrected indirect biomicroscopy of the optic nerve head. Graefes Arch Clin Exp Ophthalmol 243:257–262PubMedCrossRefGoogle Scholar
  4. 4.
    Ansari-Shahrezaei S, Ergun E, Stur M (2006) The effect of digital measurement software on photodynamic therapy. Graefes Arch Clin Exp Ophthalmol 244:137–142PubMedCrossRefGoogle Scholar
  5. 5.
    Ansari-Shahrezaei S, Ergun E, Stur M (2006) The effect of axial length on photodynamic therapy. Am J Ophthalmol 141:699–702PubMedCrossRefGoogle Scholar
  6. 6.
    Ansari-Shahrezaei S, Ergun E, Stur M (2006) Digital area measurement of fundus landmarks. Graefes Arch Clin Exp Ophthalmol 244:649–653Google Scholar
  7. 7.
    Bennett AG, Rudnicka AR, Edgar DF (1994) Improvements on Littmann’s method of determining the size of retinal features by fundus photography. Graefes Arch Clin Exp Ophthalmol 232:361–367PubMedCrossRefGoogle Scholar
  8. 8.
    Fankhauser F, Durr U, Giger H, Rol P, Kwasniewska S (1996) Lasers, optical systems and safety in ophthalmology: a review. Graefes Arch Clin Exp Ophthalmol 234:473–487PubMedCrossRefGoogle Scholar
  9. 9.
    Husain D, Gragoudas ES, Miller JW (1998) Photodynamic therapy. In: Berger JW, Fine SL, Maguire MG (eds) Age-Related Macular Degeneration. Mosby, St. Louis, pp 297–307Google Scholar
  10. 10.
    Husain D, Kramer M, Kenny AG, Michaud N, Flotte TJ, Gragoudas ES, Miller JW (1999) Effects of photodynamic therapy using verteporfin on experimental choroidal neovascularization and normal retina and choroid up to 7 weeks after treatment. Invest Ophthalmol Vis Sci 40:2322–2331PubMedGoogle Scholar
  11. 11.
    Kondo M, Ito Y, Miyata K, Kondo N, Ishikawa K, Terasaki H (2006) Effect of axial length on laser spot size during photodynamic therapy: an experimental study in monkeys. Am J Ophthalmol 141:214–215PubMedCrossRefGoogle Scholar
  12. 12.
    Kramer M, Miller JW, Michaud N, Moulton RS, Hasan T, Flotte TJ, Gragoudas ES (1996) Liposomal benzoporphyrin derivative verteporfin photodynamic therapy: selective treatment of choroidal neovascularization in monkeys. Ophthalmology 103:427–438PubMedGoogle Scholar
  13. 13.
    Littmann H (1982) Determination of the real size of an object on the fundus of the living eye [in German]. Klin Mbl Augenheilk 180:286–289PubMedCrossRefGoogle Scholar
  14. 14.
    Littmann H (1988) Determining the true size of an object on the fundus of the living eye [in German]. Klin Mbl Augenheilk 192:66–67PubMedGoogle Scholar
  15. 15.
    Michels S, Hansmann F, Geitzenauer W, Schmidt-Erfurth U (2006) Influence of treatment parameters on selectivity of verteporfin therapy. Invest Ophthalmol Vis Sci 47:371–376PubMedCrossRefGoogle Scholar
  16. 16.
    Miller JW, Schmidt-Erfurth U, Sickenberg M, Pournaras CJ, Laqua H, Barbazetto I, Zografos L, Piguet B, Donati G, Lane AM, Birngruber R, van den Berg H, Strong A, Manjuris U, Gray T, Fsadni M, Bressler NM, Gragoudas ES (1999) Photodynamic therapy with verteporfin for choroidal neovascularization caused by age-related macular degeneration: results of a single treatment in a phase 1 and 2 study. Arch Ophthalmol 117:1161–1173PubMedGoogle Scholar
  17. 17.
    Rassow B (1972) A model of Gullstrand’s normal eye [in German]. Ophthalmologica 164:143–148PubMedCrossRefGoogle Scholar
  18. 18.
    Reinke MH, Canakis C, Husain D, Michaud N, Flotte TJ, Gragoudas ES, Miller JW (1999) Verteporfin photodynamic therapy retreatment of normal retina and choroid in the cynomolgus monkey. Ophthalmology 106:1915–1923PubMedCrossRefGoogle Scholar
  19. 19.
    Rudnicka AR, Burk RO, Edgar DF, Fitzke FW (1998) Magnification characteristics of fundus imaging systems. Ophthalmology 105:2186–2192PubMedCrossRefGoogle Scholar
  20. 20.
    Sandberg MA, Tolentino MJ, Miller S, Berson EL, Gaudio AR (1993) Hyperopia and neovascularization in age-related macular degeneration. Ophthalmology 100:1009–1013PubMedGoogle Scholar
  21. 21.
    Schmidt-Erfurth U, Miller JW, Sickenberg M, Laqua H, Barbazetto I, Gragoudas ES, Zografos L, Piguet B, Pournaras CJ, Donati G, Lane AM, Birngruber R, van den Berg H, Strong HA, Manjuris U, Gray T, Fsadni M, Bressler NM (1999) Photodynamic therapy with verteporfin for choroidal neovascularization caused by age-related macular degeneration: results of retreatments in a phase 1 and 2 study. Arch Ophthalmol 117:1177–1187PubMedGoogle Scholar
  22. 22.
    Stur M, Ansari-Shahrezaei S (2001) The effect of axial length on laser spot size and laser irradiance. Arch Ophthalmol 119:1323–1328PubMedGoogle Scholar
  23. 23.
    Treatment of Age-Related Macular Degeneration with Photodynamic Therapy (TAP) Study Group (1999) Photodynamic therapy of subfoveal choroidal neovascularization in age-related macular degeneration with verteporfin: One-year results of 2 randomized clinical trials—TAP Report 1. Arch Ophthalmol 117:1329–1345Google Scholar
  24. 24.
    Treatment of Age-Related Macular Degeneration with Photodynamic Therapy (TAP) Study Group (2001) Photodynamic therapy of subfoveal choroidal neovascularization in age-related macular degeneration with verteporfin: Two-year results of 2 randomized clinical trials—TAP Report 2. Arch Ophthalmol 119:198–207Google Scholar
  25. 25.
    Visudyne in Minimally Classic Choroidal Neovascularization (VIM) Study Group (2005) Verteporfin therapy of subfoveal minimally classic choroidal neovascularization in age-related macular degeneration: 2-year results of a randomized clinical trial. Arch Ophthalmol 123:448–457CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Siamak Ansari-Shahrezaei
    • 1
    • 2
    Email author
  • Erdem Ergun
    • 3
  • Robert Chong
    • 2
  • Adnan Tufail
    • 2
  • Andreas Wedrich
    • 1
  • Michael Stur
    • 4
  1. 1.Department of OphthalmologyMedical University of GrazGrazAustria
  2. 2.Moorfields Eye HospitalLondonUnited Kingdom
  3. 3.Department of OphthalmologySanatorium HeraViennaAustria
  4. 4.Department of Ophthalmology and OptometryMedical University of ViennaViennaAustria

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