080410_153ABC _11.31_Raghu Nagaraju


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Lead Author - Dr. Raghu Nagaraju MS Dr. Rohit Shetty, Dr Rashmi Shetty, Dr. Santosh Shivaji, Dr.Himanshu Matalia Narayana Nethralaya, Bangalore ,India. Surgeon Safety During UVA Radiation Exposure in Collagen Crosslinking

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The authors have no financial interest in the materials presented herein

Collagen cross linking (CCL) : 

Collagen cross linking (CCL) Collagen cross-linking in the cornea using riboflavin (B2) + UVA treatment leads to a significant increase in mechanical stiffness of the corneal tissue Spörl et al (Ophthalmology 1997) Increased rigidity by more than 300%

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Ultra violet (UV) - 100 and 400nm. UV- A (315 - 400nm) Myung Chul Jo et al. Environmental Health and safety University of Nevada Reno. April 2005; 5-8.

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Purpose: To study and quantify the scattered UV-A radiation used in collagen cross linking procedure. Quantification of radiation reaching the surgeon and to estimate the dampening effect by various protective devices.

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Quantification of UV - A irradiance at Various distances from the limbus At different quadrants with respect to the limbus of the patient’s cornea At horizontal, vertical and 45° from the horizontal plane.

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Prospective cross sectional case series 4 patients Spectrometer (Model USB 2000; Ocean Optics, Inc. USA) UV-X source Materials and methods Institutional ethics committee approval and informed consent (from all patients) taken

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Probe held at the surgeons eye level Probe held at 450 2 cm from limbus

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Intensity of UV irradiance measured by spectrometer in 'counts' USB2000 model 1 counts=75 photons Integration time used was 100ms Diameter of the lens used in the probe- 5mm

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Intensity of one count calculated by the formula (75×hc) / (ATλ) h- Plank’s constant= 6.026×10E-35 c- speed of light in vacuum (3×10 E 8) A = πd2/4, area of the lens at the tip of the probe. d- diameter of the lens probe, (5mm) T- integration time used, (100mm) λ- is the wavelength of light of concern,(370x10 E-9) Intensity of 1 count= 2.053×10 E-12mW/cm2

ResultsUV-A irradiance in counts : 

ResultsUV-A irradiance in counts T/S/N/I Probe down T/S/N/Iprobe horiz T/S/N/I probe 450

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1.3 counts 683.2 counts Spectrasuite Software created graphs Maximum irradiance recorded was close to the limbus that is 2 cm and 45 degrees angle to the horizontal plane

Irradiance of UV-A in counts and mW/cm2 at the level of the surgeon. : 

Irradiance of UV-A in counts and mW/cm2 at the level of the surgeon. 16.6 counts 11.5 counts Irradiance at the surgeon’s Eye level Abdomen level Results

Dampening effect with various protective shields : 

Dampening effect with various protective shields 2097 counts 105.7 counts Dampening effects produced with GLOVES

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Spoerl. E et al proved the safety of the patient with UV-A exposure in CCL procedure in their study. We in our study are proving safety of the surgeons in the procedure. Spoerl E, Mrochen M, Sliney D, et al. Safety of UVA-riboflavin cross-linking of cornea. Cornea (United States), may 2007, 26(4) p385-9

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Any excess radiation exposure of medical personnel should be minimized and doses must be kept As Low As Reasonable Achievable or Practicable (ALARA principle) Permissible level 1mW/cm2 for 16 minutes ACGIH 2004 (American conference of Governmental Industrial Hygienists) Considering 140.26 x 10-11mW/cm2 (683.2 counts) as the maximum irradiance,it will take 22000 years for 365 days a year, 7 days a week and 24 hrs a day to reach the permissible level of exposure !!! As Low As Reasonably Achievable’ ALARA principle for radiation protection. 1998 Integrated Environmental Management. Environmental health and safety office. Ultraviolet - safety - bulletin.2007; 1-5.

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Conclusion Collagen crosslinking is a safe procedure with respect to exposure of radiation to the surgeon, even when the procedure is done on more than one patient Simultaneously. Further safety can be ensured by wearing UV protective goggles, gowns, gloves.

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