1985 |
Erichsen, Jonathan T |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Pupil Size and Accommodation: Central Control @ State University New York Stony Brook
The objective of the proposed research is to study the central nervous control of accommodation, pupil size and choroidal blood flow. The nucleus of Edinger-Westphal (EW), via its projection to the ciliary ganglion, is involved in the mediation of all three of these clinically important visual functions. EW in birds is much more clearly delineated in its cytoarchitecture than in mammals, and two morphologically distinct subpopulations of neurons (i.e. choroid and ciliary) have been described in the avian ciliary ganglion. Our previous studies of the central control of the pupillary light reflex and choroidal blood flow have identified two bisynaptic retinofugal pathways projecting to different subdivisions of EW. A third subdivision of EW may be involved in the control of accommodation. The major goals of the present proposed studies are to determine: (1) the central pathways controlling accommodation, (2) the subdivision of EW to which each of these central pathways projects, (3) the differential projection of the three subdivisions of EW on the two cell types in the ciliary ganglion, (4) other afferent and efferent connections of the retinorecipient nuclei in the pupillary reflex and choroidal pathways, and (5) the morphology and regional distribution of the retinal ganglion cells giving rise to each of the pathways that input to the different subdivisions of EW. Anatomical methods, including microstimulation in conjunction with discrete lesions and conventional pathway tracing techniques (i.e., autoradiography, HRP and immunohistochemistry), will be used. In order to help establish the visual function(s) of specific pathways, both pupillometry and retinoscopy will be used to measure changes in pupil size and accommodative state of the eye during microstimulation of selected neuronal structures. These proposed studies will help elucidate the anatomical substrates mediating accommodation, the pupillary response and choroidal blood flow. This anatomical knowledge may provide critically needed experimental models for the future investigation of both developmental problems in accommodation (i.e., myopia) and the reported role of choroidal blood supply disorders in some retinal dystrophies.
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1987 — 1989 |
Erichsen, Jonathan T |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Pupil Size and Accommodation: Central Control @ State University New York Stony Brook
The objective of the proposed research is to study the central nervous control of accommodation. The nucleus of Edinger-Westphal (EW), via its projection to the ciliary ganglion, is involved in the mediation of three clinically important visual functions: accommodation, pupilloconstriction, and choroidal blood flow. EW in birds is much more clearly delineated in its cytoarchitecture than in mammals, and two morphologically distinct subpopulations of neurons (i.e., choroid and ciliary) have been described in the avian ciliary ganglion. Our previous studies of the central control of the pupillary light reflex and choroidal blood flow have identified two bisynaptic retinofugal pathways projecting to different subdivisions of EW. A third subdivision of EW may be involved in the control of accommodation. The major goals of the present proposed studies are to determine: (1) the central pathways controlling accommodation, (2) the differential projection of the three subdivisions of EW on the two cell types in the ciliary ganglion, and (3) the pupillary subdivision of EW in the cat and rabbit, important mammalian models for visual studies. Anatomical methods will be used, including: microstimulation in conjunction with discrete lesions, conventional pathway tracing techniques (i.e., autoradiography, HRP and immunohistochemistry), and transsynaptic transport methods. In order to help establish the visual function(s) of specific pathways, both pupillometry and retinoscopy will be used to measure changes in pupil size and accommodative state fo the eye during microstimulation of selected neuronal structures. More anatomical knowledge of the central control of accommodation may provide critically needed experimental models for the future investigation of the role of over-accommodation in the development of myopia.
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1993 — 1995 |
Erichsen, Jonathan T |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Pupil Size and Accommodation--Central Control @ State University New York Stony Brook
Accommodation, pupilloconstriction and choroidal blood flow are all clinically important ocular functions. Both the nature of the visual stimuli that elicit each of these responses and the peripheral mechanisms by which each is produced have been the subject of investigation. Yet surprisingly little is known about the central neural circuits involved. The delineation of the anatomical pathways mediating accommodation, pupilloconstriction and choroidal blood flow and the possible sites of interaction between them would make it possible to test a variety of fundamental hypotheses concerning the respective roles of these three ocular functions in a variety of clinical pathologies. The long-term goal of this research program is to improve our understanding of the functional organization of accommodation pathways that control the ability to focus the eye in vertebrates and use this information to determine the role that the central nervous system may play in the development of myopia. Over the past decade, the chick has become an important model for the study of myopia. In the proposed experiments, chronic stimulation of accommodation "centers" in the developing chick brain will be used to test directly the clinical "near work" hypothesis that overaccommodation, or too much near vision, can produce myopia or nearsightedness. In addition, using pathway tracing techniques in conjunction with microstimulation, the brainstem circuits involved in accommodation will be determined. In summary, this set of experiments will anatomically and functionally define the brainstem circuitry controlling accommodation and determine its role in the causation of experimental myopia.
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