Our lab first began measuring cone function using a technique for psychophysically measuring bleaching and regeneration of opsins, in the early 1980's. Using this technique we were able to find changes in cone health, and also test models of light interaction with the cone photoreceptors. The technique is based on the change in absorption spectrum of a pigment when present in quantity (Beer's law and self screening). It is very sensitive and can even be used for dynamic measurements. At the time very few labs could construct a high illuminance anomaloscope adequate for patient measurements, and it is only since about 2019 that people are starting to go back and become aware of the technique.
As we moved into more optical techniques for measurements we developed a technique that arose from Jean-Marie Gorrand and Francois Delori's work that allowed the measurement of cone directionality (the Stiles Crawford effect) by an all optical means. This was further developed by Susana Marcos to allow estimation of cone spacing from the scattering of cones in the pupil plane. We combined this work, with work that was being done in Ann Elsner's lab developing imaging based cone densitometry using the scanning laser ophthalmoscope (SLO).
Currently we use adaptive optics imaging to study the cones, combining our expertise in wavefront sensing and reflectometry with Ann's work on the SLO to generate unique AOSLO systems and characterizing cone packing in health and disease.
Psychophysical Measures of Cone bleaching and regeneration
Burns SA, Elsner AE, Lobes LA Jr., and Doft BH "A Psychophysical technique for measuring cone photopigment bleaching". Invest. Ophthalmol. and Vis. Sci. 28,711-717, 1987.
Elsner AE, Burns SA, Lobes LA Jr., and Doft BH "Cone Photopigment bleaching abnormalities in diabetes". Invest. Ophthalmol. and Vis. Sci. 28, 718-723, 1987.
Elsner AE, Burns SA, and Lobes LA Jr. "Foveal Cone Pigment Optical Density in Retinitis Pigmentosa". Appl. Optics. 26,1378-1384, 1987.
Burns SA, Elsner AE, and Lobes LA "Photopigment Bleaching in Central Serous Retinopathy". Applied Optics. 27, 1045-1049, 1988.
Elsner AE, Berk L, Burns SA, and Rosenberg PR. "Aging and human cone photopigments", J. Opt. Soc. Amer. A. 5, 2106-2112, 1988.
Elsner, AE, and Burns, SA and Webb RH "Mapping Cone Pigment Optical Density in Humans" J. Opt. Soc. Amer. 10, 52-58, 1993.
Burns SA, and Elsner AE, "Color-matching at high illuminances: photopigment optical density and pupil entry" J. Opt. Soc. Amer. 10, 221-230, 1993
Reflectometric Measurement of Cone Orientation and Photopigment Optical Density
Burns, SA, Wu, S., Delori, F. and Elsner AE "Direct Measurement of Human Cone Photoreceptor Alignment" J. Opt. Soc. Amer. A. 12, 2329-2338, 1995.
Burns, SA, Wu, S, He, J, and Elsner, AE “Variations in photoreceptor directionality across the central retina”, J. Optical Society Amer, A 14, 2033-2040, 1997. PMCID: PMC3395223
Marcos, S, Burns, SA, and He, J "A Model for cone directionality reflectometric measurements based on scattering." Journal of the Optical Society of America A 15, 2012-2022, 1998.
Elsner, AE, Burns, SA, Beausencourt, E, and Weiter, JJ, " Foveal cone photopigment distribution: small alterations associated with macular pigment distributions", Invest. Ophthalmol. Vis. Sci. 39,2394-2404 1998
Marcos, S, and Burns, S.A.“Cone spacing and waveguide properties from cone directionality measurements” J. Opt. Soc. Amer. A 16, 995-1004, 1999. PMCID: PMC2882181
He, JC, Burns, S.A., and Marcos, S. “Comparison of cone directionality determined by psychophysical and reflectometric techniques” Journal of the Optical Society, A, 16:2363-2369, 1999. PMC2970515
Elsner AE, L. Moraes, E. Beausencourt, A. Remky, S.A. Burns, J.J. Weiter, J. P. Walker, G. L. Wing, P. A. Raskauskas and L. M. Kelley “Scanning laser reflectometry of retinal and subretinal tissues” Optics Express 6, 243-250, 2000
Elsner, A.E., Burns, S.A., and Weiter, J.J. “Cone Photopigment In Older Subjects: Decreased Optical Density In Early Age-Related Macular Degeneration” J Opt Soc Am A Opt Image Sci Vis 19: 215-222, 2002., PMID: 11778727 PMC2981061
Prieto, P, McLellan, J.S., and Burns, S.A. Investigating The Light Absorption In A Single Pass Through The Photoreceptor Layer By Means Of The Lipofuscin Fluorescence. Vision Research 45 (15): 1957-1965, 2005, PMCID: PMC1479308
Marcos, S, and Burns, SA, Cone Directionality from Laser Ray Tracing in Normals and LASIK patients, Journal of Modern Optics. 56: 2181 – 2188 2009
AO Imaging and Properties of the Cone Photoreceptors
Burns, SA, Marcos, S, Elsner, AE, Bara, S, “Contrast Improvement for Confocal Retinal Imaging Using Phase Correcting Plates” Optics Letters. 27: 400-402, 2002
Burns, S.A., Tumbar, R., Elsner, A.E., Ferguson, D., & Hammer, D.X.. Large-field-of-view, modular, stabilized, adaptive-optics-based scanning laser ophthalmoscope. Journal of the Optical Society of Americaa-Optics Image Science and Vision, 24 (5), 1313-1326., 2007, PMCID: PMC2443858
Chui, Y, Song, H, Burns, SA, “Individual variations in human cone photoreceptor packing density: variations with refractive error.” Investigative Ophthalmology and Vision Science Invest. Ophthalmol. Vis. Sci. 49: 4679-4687, 2008 PMCID: PMC2710765
Chui, T.Y.P., Song, H.X., & Burns, S.A. (2008). Adaptive-optics imaging of human cone photoreceptor distribution. Journal of the Optical Society of America a-Optics Image Science and Vision, 25 (12), 3021-3029. PMCID: PMC2738986
Song H, Qi X, Zou W, Zhong Z, Burns SA, Dual electro-optical modulator polarimeter based on adaptive optics scanning laser ophthalmoscope Optics Express, Vol. 18, Issue 21, pp. 21892-21904 (2010) PMCID: PMC2972199
Song, H, Chui TYCP, Zhong, Z, Elsner, AE, Burns, SA “Variation of Cone Photoreceptor Packing Density with Retinal Eccentricity and Age”, Investigative Ophthalmology and Vision Science 52:7376-7384 (2011). PMCID: PMC3183974
Chui TY, Song H, Clark CA, Papay JA, Burns SA, Elsner AE. Cone photoreceptor packing density and the outer nuclear layer thickness in healthy subjects. Invest Ophthalmol Vis Sci. 2012 May 8. PMID: 22570340 PMCID: PMC3406883
Lammer J, Prager SG, Cheney MC, Ahmed A, Radwan SH, Burns SA, Silva PS, Sun, JK Cone Photoreceptor Irregularity on Adaptive Optics Scanning Laser Ophthalmoscopy Correlates with Severity of Diabetic Retinopathy and Macular Edema Invest Ophthalmol Vis Sci. 2016 Dec 1;57(15):6624-6632. doi: 10.1167/iovs.16-19537. PMCID 5152564 PMID: 27926754
Elsner AE. Chui TYP, Lei F, Song HX, Papay JA, and Burns SA. Distribution differences of macular cones measured by AOSLO: variation in slope from fovea to periphery more pronounced than differences in total cones 2017 Vision Res. 132:62-68. https://doi.org/10.1016/j.visres.2016.06.015. PMCID: PMC5346455. PMID: 27793592
Sawides, L., A. de Castro and S. A. Burns (2017). "The organization of the cone photoreceptor mosaic measured in the living human retina." Vision Res 132: 34-44. PMC5290289. PMID: 27353225
King, BJ; Sapoznik, KA; Elsner, AE; Gast, TJ; Papay, JA; Clark, CA; Burns, SA, Spectral Domain Optical Coherence Tomography and Adaptive Optics Imaging of Outer Retinal Tubulation , Optom Vis Sci. 2017 Mar;94(3):411-422. https://doi.org/10.1097/OPX.0000000000001031. PMID: 27984506 PMC5321857
Sawides, L, Sapoznik, KA, de Castro, A, Walker, BR, Gast, TJ, Elsner, AE, Burns, SA, Alterations to the foveal cone mosaic of diabetic patients, Investigative Ophthalmology and Vision Science, 2017 58(9):3395-3403. https://doi.org/10.1167/iovs.17-21793 PMC5290289 PMID: 27353225 PMCID: PMC5501497