Document Type: Original Research

Authors

1 Department of Medical Physics, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran

2 Medical Physics Department, Reza Radiotherapy Oncology Centre, Mashhad, Iran

3 Stem Cell Research Centre, Tabriz University of Medical Sciences, Tabriz, Iran

4 Department of Medical Bioengineering, Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran

5 School of Biomedical Sciences, University of Aberdeen, Aberdeen, AB25 2ZD, UK

6 Retina Research Center, Mashhad University of Medical Science, Mashhad, Iran

7 Research Unit, Sensory Biology & Organogenesis (SBO), Helmholtz Zentrum München, 85764 Neuherberg – Munich, Germany

Abstract

Introduction: The aim of the present study was to determine burn intensity in retinal laser photocoagulation based on laser parameters; wavelength, power, beam size and pulse duration, using Optical Coherence Tomography (OCT), fundus camera, physical eye model and computer simulation in a clinical study.Materials and Methods: Participants were 10 adult patients between 50-80 years with proliferative diabetic retinopathy. A multicolor-photo coagulator with 532 nm green and 672 nm red for retina photocoagulation in diabetic retinopathy was used to investigate the participants. Lesion size was measured for spot sizes 50 and 100 μm, with 100 and 150 mW laser power, and pulse duration 50 and 100 ms by OCT. Artificial eye and Zemax-optical design software were used with the same laser parameters.Results: Appearance of OCT and fundus images showed direct relationship between retina burn size and lesion intensity with exposure time and power and also reverse relationship with laser spot size. Compared to red wavelength, burn size and lesion intensity increased in green wavelength. On the other hand, results from physical eye model were the same as clinical examination shown. Laser spot size in retina with Zemax simulation demonstrated that red wavelength was greater than green one.Conclusion: This study showed shorter pulses provide decrease in duration of laser surgery with significantly reduced pain. Results and calculations described in this article can help clinicians adjusting the required total coagulated area, the number of lesions and pattern density.

Keywords

  1. Treatment techniques and clinical guidelines for photocoagulation of diabetic macular edema. Early Treatment Diabetic Retinopathy Study Report Number 2. Early Treatment Diabetic Retinopathy Study Research Group. Ophthalmology. 1987;94:761-74. PubMed PMID: 3658348.
  2. Mainster MA. Decreasing retinal photocoagulation damage: principles and techniques. Semin Ophthalmol. 1999;14:200-9. doi.org/10.3109/08820539909069538. PubMed PMID: 10758220.
  3. Fong DS, Girach A, Boney A. Visual side effects of successful scatter laser photocoagulation surgery for proliferative diabetic retinopathy: a literature review. Retina. 2007;27:816-24. doi.org/10.1097/IAE.0b013e318042d32c. PubMed PMID: 17891003.
  4. Kulkarni G. Laser-tissue interaction studies for medicine. Bulletin of Materials Science. 1988;11:239-44. doi.org/10.1007/BF02744557.
  5. Krauss JM, Puliafito CA. Lasers in ophthalmology. Lasers in surgery and medicine. 1995;17:102-59. doi.org/10.1002/lsm.1900170203.
  6. Muqit MM, Gray JC, Marcellino GR, Henson DB, Young LB, Patton N, et al. Barely visible 10-millisecond pascal laser photocoagulation for diabetic macular edema: observations of clinical effect and burn localization. Am J Ophthalmol. 2010;149:979-86 e2. PubMed PMID: 20510687.
  7. Jain A, Blumenkranz MS, Paulus Y, Wiltberger MW, Andersen DE, Huie P, et al. Effect of pulse duration on size and character of the lesion in retinal photocoagulation. Arch Ophthalmol. 2008;126:78-85. doi.org/10.1001/archophthalmol.2007.29. PubMed PMID: 18195222.
  8. Palanker D, Lavinsky D, Blumenkranz MS, Marcellino G. The impact of pulse duration and burn grade on size of retinal photocoagulation lesion: implications for pattern density. Retina. 2011;31:1664-9. doi.org/10.1097/IAE.0b013e3182115679. PubMed PMID: 21642898.
  9. Nagpal M. Clinical experience with a high-speed multispot laser. Retina Today. 2008;3:76-8.
  10. Mojana F, Brar M, Cheng L, Bartsch DU, Freeman WR. Long-term SD-OCT/SLO imaging of neuroretina and retinal pigment epithelium after subthreshold infrared laser treatment of drusen. Retina. 2011;31:235-42. doi.org/10.1097/IAE.0b013e3181ec80ad. 21157398. PubMed PMCID: 3530923.
  11. Deák GG, Bolz M, Prager S, Ritter M, Kriechbaum K, Scholda C, et al. Photoreceptor Layer Regeneration is Detectable in the Human Retina Imaged by SD-OCT after Laser Treatment Using Subthreshold Laser PowerOuter Retina Recovers after Subthreshold Laser. Investigative ophthalmology & visual science. 2012;53:7019-25. doi.org/10.1167/iovs.12-10196.
  12. Brown JC, Solomon SD, Bressler SB, Schachat AP, DiBernardo C, Bressler NM. Detection of diabetic foveal edema: contact lens biomicroscopy compared with optical coherence tomography. Arch Ophthalmol. 2004;122:330-5. doi.org/10.1001/archopht.122.3.330. PubMed PMID: 15006844.
  13. Navarro R, Santamaria J, Bescos J. Accommodation-dependent model of the human eye with aspherics. J Opt Soc Am A. 1985;2:1273-81. doi.org/10.1364/JOSAA.2.001273. PubMed PMID: 4032096.
  14. Norrby S, Piers P, Campbell C, van der Mooren M. Model eyes for evaluation of intraocular lenses. Appl Opt. 2007;46:6595-605. doi.org/10.1364/AO.46.006595. PubMed PMID: 17846654.
  15. Shen J, Spors F. Optical Modeling and Analysis of Peripheral Optics of Contact Lenses. Open Journal of Ophthalmology. 2012;2:54. doi.org/10.4236/ojoph.2012.23012.
  16. Liou HL, Brennan NA. Anatomically accurate, finite model eye for optical modeling. J Opt Soc Am A Opt Image Sci Vis. 1997;14:1684-95. doi.org/10.1364/JOSAA.14.001684. PubMed PMID: 9248060.
  17. Rasta S H, Manivannan A, Sharp P. Spectral imaging technique for retinal perfusion detection using confocal scanning laser ophthalmoscopy. J Biomed Optics. 2012;17(11): 116005,1-11. DOI: 10.1117/1.JBO.17.11.116005.
  18. Rasta SH. Retinal: Perfusion Imaging of Human Eye Using Scanning Laser Ophthalmoscope. Thesis: The University of Aberdeen; 2008.
  19. Bressler SB, Almukhtar T, Aiello LP, Bressler NM, Ferris FL, 3rd, Glassman AR, et al. Green or yellow laser treatment for diabetic macular edema: exploratory assessment within the Diabetic Retinopathy Clinical Research Network. Retina. 2013;33:2080-8. doi: 10.1097/IAE.0b013e318295f744. PubMed PMID: 23792486. PubMed PMCID: 4126070.