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Ophthalmic Instruments & Ex Vivo Retinal Pigment Epithelium Autofluorescence

By: Andrew WilliamsUniversity of Rochester

Primary Investigator: Dr. David Williams, PhDMentor: Dr. Jennifer Hunter, PhD

Home Institution: Xavier University of Louisiana

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Autofluorescence

• The Retinal Pigment Epithelium nourishes the rods and cones.

• It develops a substance called lipofuscin.

• It is the lipofuscin in the cells causing the light emitted onto the retina to autofluoresce.

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RPE Pre-exposure image

Courtesy Jessica Morgan

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150 uW Exposure for 15 minutes

Courtesy Jessica Morgan

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RPE immediately Post-exposure Image

150 uW Exposure Location

• Dimming is a phenomenon that occurs in vivo and ex vivo for light intensities of 18.8 mW/cm2 on the retina.

• These light intensities were expected to be safe.

Courtesy Jessica Morgan

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Goals

• What are the light exposures of ophthalmic devices currently used in retinal surgery?

• Do they cause dimming ex vivo?

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Endoilluminators at 4mm

24.81

61.33565.05

0

10

20

30

40

50

60

70

25 Gauge B&L 20 Gauge B&L 20 Gauge Photon

Type of Light Source

Inte

nsity

(mW

/cm

^2)

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B&L Millennium vs. Photon Spectra

0500

10001500200025003000350040004500

400 450 500 550 600 650 700 750 800 850 900 950 1000

Wavelength (nm)

Inte

nsity

(Cou

nts)

20 Gauge B&L Millennium 20 Gauge Photon 25 Gauge B&L Millennium

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Methods: Dimming Ex Vivo

Power levels of the imaging light source were recorded to ensure safe light exposures would be used to image the retina.

Images of the retina were taken at a 1º field. Block half of the image and expose area for 15 min. Then take a post image of the full 1º field.

1º Field of View 1º Field of View

ExposureImaging

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RPE Pre-Exposure Image

20 Gauge B & L Millennium Exposure Location

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Fluorescence Half Blocked Exposure Image

20 Gauge B & L Millennium Exposure Location

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RPE Post-Exposure Image

20 Gauge B & L Millennium Exposure Location

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Mean of Ratios

1.002 1.015 0.975

0.000

0.200

0.400

0.600

0.800

1.000

25 Gauge B & L 20 Gauge B & L 20 Gauge Photon

Types of Light Sources

Aver

age

Valu

e of

Rat

ios

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Conclusions

• For the Bausch & Lomb Millennium, dimming does not occur in retinal pigment epithelium ex vivo at the exposure time of 15 minutes.

• More trials are necessary to confirm that dimming occurs for the Photon light source.

• There is a continued quest for light intensities and light exposure durations that are safe for the human retina in vivo.

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AcknowledgementsI would like to thank:

Dr. Jennifer Hunter, PhDDr. David Williams, PhDJessica MorganDr. Mina Chung, MDBen MasellaBob WolfeLana NagyDr. William FischerFunding Provided through the Center for Adaptive Optics, a National Science Foundation Science and Technology Center (STC) AST-987683And rest of the Center for Visual Science and Center for Adaptive Optics family that helped to make my research in Rochester, NY successful!

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ReferencesBennett, Arthur G. Clinical Visual Optics. Butterworths Inc. Second

Ed. 1989. pp. 9-22, pp. 359-390Rodieck, R. W. The Vertebrate Retina: Principles of Structure and

Function. W. H. Freeman and Company. 1973. pp. 288-295Delori, Francois C. “Maximum permissible exposures for ocular safety

(ANSI 2000), with emphasis on ophthalmic devices.” Optical Society of America. Vol. 24, No. 5. May 2007. pp 1250-1265

Inoue, Y. “A2e mediated phototoxic effects of endoilluminators.” Br. J. Ophthalmol. Vol. 90. February 2006. pp. 229-232

Lamb, Laura E. “A2e: A Component of Ocular Lipofuscin.” Photochemistry and Photobiology. Vol. 79. 2004. pp. 127-136.

“Endoilluminator.” http://www.retinalphysician.com/article.aspx?article=100050

“Endoilluminator.” http://www.vision-surgery.com/technology-millennium.html

“Mathematics.” http://en.wikipedia.org/wiki/Mathematics/