|AFFILIATIONS||Professor of Optometry and Vision Science|
Chromatic organization in human retina; Mechanisms of visual loss with aging; Clinical psychophysics
Basic studies of chromatic organization of human parafoveal retina. These psychophysical studies address the general issue of chromatic organization of sensitivity control at parafoveal locations as compared with the fovea. A different neural organization may exist in nonfoveal areas, particularly with respect to cone inputs to center, surrounds of ganglion cells, and the relative balance between them. The specific hypothesis tested is that interaction between color adaptational mechanisms is predominantly away from the fovea, while foveal vision is characterized by relatively independent mechanisms. A few previous studies have examined the nature of this interaction. Studies that tested at the fovea found independence while studies that tested away from the fovea found interaction. Results from this project have shown significantly more interaction between color mechanisms away from the fovea, suggesting that models of visual processing based on fovea results may not be appropriate for nonfoveal vision.
Studies of mechanisms of visual loss with aging. Vision changes with age have been well documented. Previously, the majority of age-related changes in color vision were attributed to a well-known yellowing of the ocular lens. Recent evidence indicates that morphological changes occur in the retina with increasing age. This project is to determine whether neural changes occur in the retina with age, as distinct from changes in preretinal filters (lens and macular pigment), and to test the hypothesis that long-term exposure to visible radiation (light) contributes to neural loss with age. Studies have shown that approximately 40 to 50 percent of the loss of sensitivity to blue light, shown by older individuals, is caused by lens changes; the remaining loss must be attributed to alteration in neural (presumably retinal) function. The hypothesis that yellow macular pigment protects the foveal area from light damage has been tested, and evidence has been found supporting this hypothesis, lending indirect evidence that light exposure throughout a lifetime contributes to retinal damage.
Clinical psychophysics: Understanding rod monochromatism. Typical total color blindness, achromatopsia or rod monochromatism, is inherited as an automal recessive condition and is thought to result from absence of cone function. Rod monochromats have been used in basic visual studies as models of normal human rod vision and to study rod vision without interference from cone receptors. This was under the assumption that they only have rods, that their rods are like normal rods, and that rod-cone interaction is not important or doesn’t exist. We have identified 25 individuals with this very rare disorder (incidence 0.0003%). Of these, none behaves like a classical rod monochromat on all tests of vision; many show residual cone function on specialized tests, and most show evidence for rod-cone interaction, seriously questioning previous assumptions. This project aims to account for the extreme variability of vision function on the basis of heterogeneity of the retina (in cone density),’variable fixation patterns, and variations in the genotypes. An additional aim is to relate phenotypical behavior (vision characteristics) to genotypes through the use of molecular genetic techniques.
Haegerstrom-Portnoy, G., Schneck, M., Hewlett, S. and Verdon, W. Clinical vision characteristics of the congenital achromatopsias. I. Visual acuity, refractive error and binocular status. Optometry and Vision Science 73(7):446-456, 1996
Friedman, N., Haegerstrom-Portnoy, G., Paul, O., Jampolsky, A. Foveal vision function before and after fluorescein angiography. Invest. Ophthalmol Vis Sci. 35(9), 3566-3570, 1994
Haegerstrom-Portnoy, G., Schneck, M., Hewlett, S., Verdon, W. and Fisher, S. Clinical vision characteristics of the congenital achromatopsias. II. Color vision. Optometry and Vision Science 73(7):457-465, 1996
Sample PA, Johnson CA, Haegerstrom-Portnoy G, Adams AJ: Optimum parameters
for short-wavelength automated perimetry. J Glauc. 5: 375-383, 1996
Haegerstrom-Portnoy G, Schneck M, Brabyn JA and Jampolsky A. The SKILL card: An acuity test of reduced luminance and contrast. Invest. Ophthalmol Vis Sci. 38(1):207-218, 1997
Schneck M and Haegerstrom-Portnoy G. Color vision defect type and spatial vision in the Optic Neuritis Treatment Trial. Invest. Ophthalmol Vis Sci. 38(11): 2278-2289, 1997
Verdon W and Haegerstrom-Portnoy G. Topography of the multifocal ERG. Documenta Ophthalmologica 95:73-90, 1998
Haegerstrom-Portnoy, G., Schneck, M. Brabyn, J. Seeing into old age: vision function beyond acuity. Optometry and Vision Science 76(3):141-158, 1999
Haegerstrom-Portnoy, G. and Verdon, W. Rods induce transient tritanopia in Blue Cone Monochromats. Vision Res. 39 (13): 2275-2284, 1999
Haegerstrom-Portnoy G, Schneck ME, Lott LA and Brabyn JA. The relation between visual acuity and other spatial vision measures. Optometry and Vision Science, 77;12:653-662, 2000
Lott LA, Schneck ME, Haegerstrom-Portnoy G and Brabyn JA. Reading performance in older adults with good acuity. Optometry and Vision Science, 78(5):316-324, 2001
West CG, Gildengorin G, Haegerstrom-Portnoy G, Schneck ME, Lott L and Brabyn J. Is vision function related to physical functional ability in older adults? J. Am. Geriatrics Soc.(50):136-145, 2002
Haegerstrom-Portnoy G, Schneck ME, Brabyn J and Lott L. Development of refractive errors into old age. Optometry and Vision Science 79(10): 643-649, 2002
West CG, Gildengorin G, Haegerstrom-Portnoy G, Schneck ME, Lott L and Brabyn J. Vision and driving self-restriction. J. Am. Geriatrics Soc , 2003; 51:1348-55
Verdon W, Schneck ME, Haegerstrom-Portnoy G. A comparison of three techniques to estimate the human dark-adapted cone electroretinogram. Vision Research, 43(19): 2089-2099, 2003
Crognale MA, Fry M, Highsmith J, Haegerstrom-Portnoy G, Neitz M, Neithz J, Webster MA. Characterization of a novel form of x-linked incomplete achromatopsia. Feature issue for International Color Vision Society, Vis. Neurosci. 2004;21(3):197-203
Schneck M, Haegerstrom-Portnoy G, Lott LA, Brabyn JA, Gildengorin G. Low contrast vision function predicts subsequent acuity loss in an aged population: the SKI Study. Vision Research 2004; 44:2317-2325.
Haegerstrom-Portnoy G. The Glenn A. Fry Award Lecture 2003: Vision in elders–summary of findings of the SKI study. Optom Vis Sci. 2005 Feb;82(2):87-93.
Brabyn JA, Schneck ME, Lott LA, Haegerstrom-Portnoy G. Night driving self-restriction: vision function and gender differences. Optom Vis Sci. 2005 Aug;82(8):755-64.
Lott LA, Haegerstrom-Portnoy G, Schneck ME, Brabyn JA. Face recognition in the elderly. Optom Vis Sci 2005 Oct; 82(10):874-81.