INFORMATION TO USERS This manuscript has been reproduced from the microfilm master UMi films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMi a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6* x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. Bell & Howell Information and Learning 300 North Zeeb Road. Ann Arbor, Ml 48106-1346 USA 800-521-0600 UMT CHARACTERISTICS OF EXTREME-GAZE OCULAR FIXATION IN SPARSE VISUAL SURROUNDINGS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Tyson L Brunstetter, OD., M.S. ***** The Ohio State University 2000 Dissertation Committee: Approved by Nicklaus F. Fogt, OD ., PhD., Adviser Angela M. Brown, PhD . Adviser Mark A. BuIIimore, MCOptom, PhD. Physiological Optics Graduate Program Ronald Jones, OD., PhD. UMI Number 9971517 UMI* UMI Microform9971517 Copyright 2000 by Bell & Howell Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17. United States Code. Bell & Howell Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 ABSTRACT The purpose o f this dissertatioa was to determine the characteristics of extreme-gaze ocular fibcation. This was accomplished by examining eye position and movements during fixation and scleral search coil slippage. Subject calibration of search coil equipment was also studied. Seven young, emmetropic subjects fixated an LED target monocularly in the dark. A bite bar was used to fix the head. Using search coil equipment, eye positions were collected as subjects fixated a 6 arcmin LED through nasal eye rotation angles (0“, 10°, 20°, 30° and 40°). A fbveal afterimage was used to monitor for stress-induced eccentric fixation, however none was detected. Even after correction for search coil slippage, temporal fixation lags increased with eye rotation angle, and the mean eye position measured at 40° significantly lagged the target (14.5 arcmin). Fixation precision did not appear to change over qre rotation angles. Overall, while measurements with the scleral search coil suggested a lag of fixation, target foveation occurred at all gaze angles. This imperfect representation of the fovea’s position by the search coil equipment may have been due to retinal stretching or crystalline lens tilting. Typical microsaccades occurred in all subjects, and end-gaze nystagmus occurred in two subjects during 40° eye rotations. High-magnification photography was used to dhectly measure slippage of the scleral search coü during nasal gaze angles. Search coil slippage was always in the temporal direction, progressively increased with eye rotation angle, and was significant during eye rotations o f 30° (11.9 arcmm) and 40° (23 J arcmm). The data suggest that the scleral lens and bulbar conjunctiva slide together during eye movements, and return to their original position as the eye returns to straight-ahead gaze. ii At extreme angles, search coü calibrations horn a mechanical device differed fiom calibrations collected fiom human subjects. For search coü-based experiments vs^ere the eye is rotated laterally >10°, it may be more accurate to calibrate with subjects rather than the mechanical device. This would eliminate confotmding influences firom search coü slippage, improper target positioning and imperfect representation of the fevea’s position by the search COÜ equipment. lU Dedicated to the memory of my grandparents, Gerald R. and Mary E. Mooney. IV ACKNOWLEDGMENTS I would like to thank my advisor. Dr. Nick Fogt, for the volume of time and energy that he has invested into my education. However, this type o f sacrifice is not unusual for him; he always puts the student first Dr. Fogt has won numerous teaching awards for good reason. I would also like tothank Drs. Angela Brown, Mark BuIIimore, Ronald Jones and Ewen King-Smith for their support and suggestions, as well as for crucial advice on data analysis. Sincere appreciation is extended to the administration at the Naval Aerospace Medical Research Laboratory, especially to my Commanding and Executive Officers, Captain Glenn Armstrong and Commander Andrew Engle, respectively. Without their unwavermg support and their insistence that I keep pushing forward, this manuscript might never have been completed. VTTA June 13,1971 ..............................Bom - Warren, Ohio 1993 ............................................B.S. Molecular Biology, Grove City College 1997 ............................................OJ). Doctor of Optometry, The Ohio State University College o f Optometry 1997 ............................................M.S. Physiological Optics, The Ohio State University Graduate School 1996-1997 ................................Research Assistant Eye Physiology Laboratory The Ohio State University College of Optometry 1997 - 1999 ................................Graduate Teaching and Research Associate The Ohio State University College of Optometry 1999 - present ..............................Navy Optometrist / Primary hivestigator Naval Aerospace Medical Research Laboratory Naval Air Station Pensacola VI PUBLICATIONS 1. Brunstetter TJ, Fink BA and Hill RM. What is the oxygen environment under an encapsulated segment bifocal contact len? JAm Optom Assoc 1999;70:641-6. 2. Hill RM, Brunstetter TJ and Fink BA. Complex oxygen pathways: Multi-layered contact lens systems and their transmissihilities. Invest Ophthalmol Vis Sci 1999;40(4):s9G5. 3. Brunstetter TJ and Fogt NF. Slippage of scleral search coils in extreme horizontal angles of gaze. Invest Ophthalmol Vis Sci 1999;40(4):s55. 4. Hill RM, Fink BA, Smith BJ and Brunstetter TJ. Physiological correlates of Dk/L: A developing model and its applications. Optom Vis Sci I998;75(12s):156. 5. Brunstetter TJ and Fogt NF. The accuracy and precision of extreme-gaze ocular fixation in sparse visual surroundings. Optom Vis Sci I998;75(12s):103. 6. Brunstetter TJ, Fink BA and Hill RM. The oxygen environment under an encapsulated segment bifocal RGP contact lens under static conditions. Optom Vis Sci 1997;74(l2s):94. 7. Brunstetter TJ. What is the oxygen environment under an encapsulated segment bifocal contact lens? Master of Science in Physiological Optics Thesis, Graduate School of The Ohio State University, Columbus, Ohio, June 1997. FIELDS OF STUDY Major Field: Physiological Optics vu TABLE OF CONTENTS A bstract.................................................................................................................... ii D edication ................................................................................................................. iv Acknowledgments ...................................................................................................... v V ita............................................................................................................................. vi List of Tables............................................................................................................. xi List of Figures ..................................................................... xv List of Programs ..................................................................................................... xx List of Slippage Plots ............................................................................................... xxi List of Gaze Plots................................................................................................. xxii Chapters: 1. Introduction .................................................................................................I 2. Historical Review .............................................................................................. 5 2.0 Introduction............................................................................................... 5 2.1 Direction of Gaze....................................................................................... 5 2.1.1 Primary Line of Sight .................................................................... 5 2.1.2 Eye Center of Rotation .................................................................. 6 2.1.3 Positions of Gaze .......................................................................... 7 2.2 Foveal Fixation .........................................................................................7 221.1 Miniature Eye Movements during Fixation .................................. 8 2.2.2 Abnormal Fixation .......................................................................