The Effect of Target Color on Laser Absorption Ben Azar Grade 9 Central Catholic High School

Rationale To determine the effects of target color on the absorption of a Nidek GYC1500 532nm frequency-doubled green ophthalmic YAG laser. Laser test fire experience Could target color possibly enhance the laser’s effectiveness and safety? Will target color have an effect on laser absorption?

Purpose To test if there could be a way to possibly use target color to enhance the safety of laser procedures and surgeries. To find a way to make surgeries safer by treating only the target tissue and not the surrounding normal tissue. This is especially important when working with delicate structures such as the eye.

Lasers Acronym for Light Amplification by Stimulated Emission of Radiation Excitatory material which is stimulated Displaces electrons Emission of energy/photons Laser beam power, duration, and spot size can be modified

Ophthalmic 532nm Frequency Doubled YAG Green variant Makes delicate small burns Excitatory material: neodymium-doped, yttrium-aluminum-garnet crystal 1064nm Frequency doubling/532nm Visible spectrum

Duration and Power Play a big role in absorption More power=more intense burn Can be modified to fit the needs of the procedure Glaucoma treatment with frequency doubled YAG ms  ns

Target Manipulation The target’s characteristics can also have an effect on laser absorption PDT Visudyne is a drug that collects in abnormal blood vessels in the retina Specific wavelength activates Destroys abnormal blood vessels Protects normal blood vessels

Changing Eye Color It is uncommon but some scientists claim to be able to change the colors of eyes Green lasers are absorbed well by melanin The settings are adjusted to destroy melanin without destroying surrounding normal tissue Destroying melanin changes eye color What if I could stain tissues to increase laser absorption?

Experimental Target Animal tissues were beyond the scope of this experiment Lasers are usually tested on paper before used on patients in order to ensure that they are working properly Paper is readily accessible and comes in multiple colors Tissue paper was too porous Construction paper worked best POC

Hypotheses Null=Target color will have no significant effect on laser absorption Alternative=Target color will have an effect on laser absorption

Materials Nidek GYC1500 532nm frequency-doubled ophthalmic YAG laser (green variant) 60 lb. construction paper (Blue, Green, Yellow, Brown, and Red) Haag Streit 900 slit lamp 20 diopter magnifying lens

Procedures The laser was turned on and calibrated. Paper was centered and taped to the slit lamp in consistent fashion. The laser settings were adjusted. The laser was focused on the target. A spot size of 500 microns and a pulse duration of 0.15 seconds was used in all trials. The laser was fired three times for each power (100-900 mW in 100 mW increments). Once all of the bursts had been fired, the paper was taken off of the slit lamp and the results were recorded by looking at the ultra fine holes under a 20 diopter magnifying lens. Steps two through seven were repeated for all five colors of paper.

Pictures of Laser Burns

Effect of Blue Paper on Laser Absorption No Penetration=0 Partial Penetration=1 Full Penetration=2

Effect of Red Paper on Laser Absorption No Penetration=0 Partial Penetration=1 Full Penetration=2

Effect of Brown Paper on Laser Absorption No Penetration=0 Partial Penetration=1 Full Penetration=2

Effect of Yellow Paper on Laser Absorption No Penetration=0 Partial Penetration=1 Full Penetration=2

Effect of Green Paper on Laser Absorption No Penetration=0 Partial Penetration=1 Full Penetration=2

Effect of All Colored Paper on Laser Absorption No Penetration=0 Partial Penetration=1 Full Penetration=2

Conclusion Yellow differed significantly from the other colors Yellow and green were lower than the other colors at 500 and 600 nm Yellow remained lower than the other colors Not much variation seen among the following colors: blue, red, and brown The null was rejected for yellow and green

Limitations and Extensions Data was qualitative. A key had to be made. Holes were very small so it was hard to measure (especially between partial and full penetration). Only one type of material used Only one wavelength used Unknown relationship to bodily tissues Extensions More replicates Other wavelengths Natural tissues Could have used more increments of power.

Sources http://retinatoday.com/2012/04/multicolor-scan-laser-photocoagulator- provides-efficiencies-in-the-clinic https://jamanetwork.com/journals/jamaophthalmology/fullarticle/264612 https://www.reviewofoptometry.com/article/ro0917-make-your-brown- eyes-blue http://eyewiki.aao.org/Photodynamic_Therapy_(PDT) http://eyewiki.aao.org/Laser_Trabeculoplasty:_ALT_vs_SLT http://eyewiki.aao.org/Lasers_(surgery) https://en.m.wikipedia.org/wiki/Second-harmonic_generation https://www.ophthalmologyweb.com/Tech-Spotlights/26524-Nd-YAG- Lasers-in-Ophthalmology/