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Oculomotor Rehabilitation for Reading Dysfunction in Mild Traumatic Brain Injury

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Oculomotor rehabilitation for reading dysfunction in mild traumatic brain injury Item Type Article; Thesis Authors Thiagarajan, Preethi Download date 28/09/2021 16:15:48 Link to Item http://hdl.handle.net/20.500.12648/1144 OCULOMOTOR REHABILITATION FOR READING DYSFUNCTION IN MILD TRAUMATIC BRAIN INJURY Submitted by Preethi Thiagarajan DISSERTATION In partial satisfaction of the requirements for the degree of Doctor of Philosophy in Vision Science State University of New York State College of Optometry © Preethi Thiagarajan 2012 I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii Abstract Aim Considering the extensive neural network of the oculomotor subsystems, global damage as a result of traumatic brain injury could compromise precise oculomotor control, thus causing reading dysfunction. The aim of the present thesis was to evaluate comprehensively the effect of oculomotor-based vision rehabilitation in symptomatic individuals with respect to nearwork and reading and having a mild traumatic brain injury (mTBI). A wide range of laboratory and clinical parameters related to reading involving vergence, accommodation, and version were tested. Methods Twelve subjects with documented mTBI and nearvision-related symptoms participated in the study. A cross-over, interventional experimental design was used involving true “oculomotor” training and “SHAM” training. Each training protocol was performed for 6 weeks, 2 sessions a week, 45 minutes of actual training per session. During each training session, all three oculomotor subsystems (vergence/accommodation/version) were trained for 15 minutes each in a randomized order. All laboratory and clinical parameters were measured before (baseline) and after true oculomotor (post-OMT) and SHAM (post-SHAM) training. In addition, nearvision- related symptoms were assessed using the Convergence Insufficiency Symptom Survey (CISS) scale. Lastly, subjective attention was measured using the Visual Search and Attention Test (VSAT). iii Results Following true oculomotor training, there was a marked improvement in various laboratory and clinical parameters assessed. Over 80% of the abnormal parameters found at baseline testing were found to significantly improve with training. Dynamics of vergence and accommodation, along with clinically assessed maximum amplitudes, improved markedly. Versional saccadic eye movements demonstrated improved rhythmicity and accuracy. These results together had a significant positive impact on overall reading ability. The improved reading-related oculomotor behavior was reflected in reduction of symptoms. In addition, subjective attention was found to also improve with true oculomotor training. In contrast, none of the aforementioned parameters changed with SHAM training. Conclusions Oculomotor-based vision rehabilitation had a strong positive effect on reading- related oculomotor control. This oculomotor learning effect is suggestive of intact neuroplasticity mechanisms in a compromised brain following TBI. iv Acknowledgements My heartfelt thanks to my advisor Prof. Kenneth J. Ciuffreda for his constant motivation, guidance, and support throughout my graduate program. I am always indebted to him for being my professional father and providing me with an opportunity to learn and acquire scientific knowledge. This project was funded by the US Army, DoD, TATRC. My sincere thanks to them for making this project possible. I thank all my study participants who devoted their precious time for taking part in the study and enlightened me with valuable insights. Thanks to SUNY Graduate program, American Optometric Foundation Ezell Fellowship, Minnie Flaura Turner Memorial Fund, and College of Optometrists in Vision Development for their financial support and encouragement. I would like to thank my Committee members Dr. Jose Manuel Alonso and Dr. Jordan Pola for their comments and suggestions. My sincere gratitude to Dr. William R. Bobier for his helpful comments as an external examiner. Many thanks to Mariano Rodriguez for programming test targets. I acknowledge Diana Ludlam and Naveen Yadav in Ciuffreda’s lab for their help during pilot testing. I would like to thank all the clinicians in the SUNY Head Trauma Clinic for providing me with the subjects. Thanks to Jorge Villon for his technical and computing support. My heartfelt thanks to my friends Anthony Perez, Naveen Yadav, Nili Parekh, Phoram Shah, and Gayathri Thyagarajan for their love, care, and emotional support during my tough times. v Dedication To my parents, brother and aunts for their unflinching love, support and encouragement, To my spiritual Guru for being my lynchpin, & To all TBI survivors vi Table of Contents Abstract ........................................................................................................................................... iii Acknowledgements .......................................................................................................................... v Dedication ....................................................................................................................................... vi Table of Contents ........................................................................................................................... vii Chapter 1 TRAUMATIC BRAIN INJURY – AN OVERVIEW ..................................................... 1 1.1 Definition and classification .................................................................................................. 1 1.2 Mechanisms and Pathophysiology of TBI ............................................................................. 2 1.3 Neuroimaging in TBI ............................................................................................................. 6 Chapter 2 SEQUELAE OF TBI ..................................................................................................... 10 2.1 General sequelae of TBI ...................................................................................................... 10 2.2 Visual sequelae in TBI ......................................................................................................... 12 Chapter 3 THESIS PREAMBLE ................................................................................................... 16 3.1 Introduction .......................................................................................................................... 16 3.1.1 Reading: Basic Concepts .................................................................................................. 16 3.1.2 Investigations on reading in brain injury: Diagnosis .................................................... 17 3.1.3 Oculomotor rehabilitation in TBI ................................................................................. 21 3.1.4 Theory under consideration .......................................................................................... 23 3.1.5 Hypothesis..................................................................................................................... 24 3.2 AIMS OF THE STUDIES ................................................................................................... 25 3.3 METHODS .......................................................................................................................... 29 3.3.1 Subjects ......................................................................................................................... 29 3.3.2 Study design .................................................................................................................. 30 3.3.3 Evaluative Procedures ................................................................................................... 32 3.3.4 Treatment protocol ........................................................................................................ 48 3.4 ANALYSES ......................................................................................................................... 57 3.4.1 Data acquisition and analyses for objective recordings ................................................ 57 3.4.2 STATISTICAL ANALYSES ....................................... Error! Bookmark not defined. 3.5 RESULTS ............................................................................................................................ 60 3.5.1 Laboratory and clinically-based measures of accommodation, vergence, and version 61 3.5.2 Additional subjective tests ............................................................................................ 73 3.5.3 Correlations: Objective and subjective findings ........................................................... 74 vii 3.6 DISCUSSION ...................................................................................................................... 78 3.6.1 True oculomotor training effects ................................................................................... 78 3.6.2 SHAM training effects ................................................................................................ 100 3.6.3 Future directions ......................................................................................................... 101 3.7 CONCLUSIONS...............................................................................................................
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