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Functional Anatomy of the Ciliary Muscle in Birds and Humans

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Functional Anatomy of the Ciliary Muscle in Birds and Humans Functional Anatomy of the Ciliary Muscle in Birds and Humans by Machelle T. Pardue A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Doctor of Philosophy in Vision Science and Biology Waterloo, Ontario, Canada, 1996 8 Machelle T. Pardue, 1996 National iibrary Bibliothèque nationale (*B of Canada du Canada Acquisitions and Acquisitions et Bibliographie SeNices services bibliographiques 395 Weliirrgtori Sîreeî 395. rue Wenïngton OttawaON KIAW Oüawa ON K1AW Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive 1icence allowing the exclusive parnettant à la National Liiof Canada to Bibliothècpe nationale du Canada de reproduce, loan, disbi'b9te or sell reprodune, prêter, distnLbuer ou copies of Werthesis by any means vendn des copies de sa these de and in any form or format, making qpelque manière et sous qyelqye this thesis amable to interested fome que ce soit pour metûe des persons. exemplaires de cette thèse à la disposition des personnes mtéressées. The author retains ownership of the L'auteur conserve la pro@& du copyright m hislher thesis. Neither droit d'auteur qui protège sa thèse. Ni the thesis nor sub- extmcts la thèse ni des extraits substanîiels & nom it may be @ted or otherwise celle-ci ne doivent être imprimds ou reproduced with the aufhor's autrement reproduits sans son permission. autorisation* The University of Waterloo requues the signatures of al1 persons ushg or photocopying this thesis. Please sign below, and give address and date, iii Abstract Functional Anatomy of the Ciliary Muscle in Birds and Humans The functional aaatomy of the avian ciliary muscle has beai difncdt to describe due to its inaccessible location inside the eye. This thesis compares the ciliary muscle of birds and humam in both the relaxed and contracted states. The two groups both accommodate by changing the shape of the lem, although the ciliary body and ciliary muscle morphology are very different. The ciliary muscles of the chicken (Gahga1iu.s domesticus),the pigeon (Columbiafivia), the kestrel (Faico sparverius),and the hooded merganser (Mmgus cucullatus) (four ~ieswith ditTering accommodative n&) were examined histologicdly. The ciliary muscle of ail four species can be divided into three main muscle fibre groups based on insertion and ongin: anterior, posterior and intemal. The anterior muscle fibre puporiginates at the sclera under the scleral ossicles and inserts into the inner lamellae ofthe cornea. During accommodation these fibres pull the comea posteriorly, changing the cuwature of the comea. The posterior muscle fibre group originates on the sclera and inserts posteriorly ont0 the baseplate of the ciiiary body. The posterior fibre group acts on the baseplate of the ciliary body, puiiing it fonvard to change the cuwature of the lem during accommodation. The interna1 muscle fibre group extends hmthe baseplate of the ciüary body to the imer lameiiae of the comea and thus has a role in both comeal and lenticular accommodation. Species differences do exist as seen in subgroups determined by the orientation of the fibres between the relaxed and contracted states and the percentage of fibres within the main muscle fibre gcoups). in general, the rnajority of ciiiary muscle fibres in the chicken, pigeon, and kestnl are in the antetior muscle fibre group, suggestkig an emphasis on comeal accommodation; in the ciliary muscle of the hooded merganset, the majority of fibres are in the intemal and posterior muscle fibre groups, indicating that lenticular accommodation is the predominant form of accommodation. For the study of human ciliary muscle, meen pairs ofeyes ranging Ïn age fiom O to 107 years were treated with 20% pilocarpine and 5% atropine. The ciliary muscle decreases in length (8-20%) and in width (544%)). Changes With contraction were not found in the other measurements. The fibres of the ciliary muscle do not change orientation with contraction. During accommodation the ciliary muscle teleases zonular tension by shorteaing, but not by moving forward. With age the ciliary muscle shortens, widens, and moves fornard. Changes in ciliary muscle dimensions were seen at ail ages, indicating no loss of muscle contractility. The amotmt of co~ectivetissue in the ciliary muscle increases (24%) with age. The aging ciliary muscle is able to contract, but the reduction of zonular tension bmught on by age, may prevent lenticdar changes, thereby contributing to presbyopia. Acknowledgments Numerous individuais and groups assisted in the completion of the thesis by providing tissue, technical support, andloi advice. First, 1would like to express my heart-felt appreciation to my supervisor, Dr. Jacob Sivak, for encouraping me to pursue this degree and for ali his support. In addition, 1would iike to thank my committee members, Dr. Ralph Chou and Dr. Bill Diewones for their advice and support in the development of the thesis. 1would iike to acknowledge the Kortwright Waterfowl Center, McDonald's Coilege, esp. Dr. Bird, and Pascal Vieira of Grand Valley, Ontario for allowing me to coiiect bird eyes. Human eyes were obtained hmthe Eye Bank of Canada, Ontario Division, tbugh the kind cooperation of Marilyn Schneider and Mt. Hasani. The histology tracing prognun was written by Dr. Adrian Glasser. In addition, Adrian offered much useful advice and critiques of this work. The cornputer monitors used for this study were loaned by Dr. Trefford Simpson and Dr. Sue Leat. Statistical advice was obtained fiom various sources inciudùig David Matthews, Erin Harvey, Dr. Trefford Simpson, Dr. Jeff Hovis, and Corrine Motluk. Translations ofpapers fiom German to English were graciously done by Henriette Stumper. 1wodd also Like to thank ail the graduate dents, facuity, and staffof the School ofûptometry for theu firiendship and assistance. Financial support was provided through the Natural Science and Engineering Research Council of Canada (NSERC) awarded to Dr. Jacob Sivak. Lastly, 1 would l&e to thank my husband, Je& for his love and support, and my daughter, Emily, who reminds me of the simple Wgs in life. Table of Contents General Ln~du~ti~nomm~ommmmmmmmomomomoomommmmmmmmmomomm~momommmmm~momomommmmmmmmammmmmmmomoom~o~mmmmo~mmmommmoo1 The.. Vertebrate Eye...................................................................................... 2 Ciliary Body Anatomy ................................................................................. 3 Hlllnatu........................................................................................... 3 Bir& ................................................................................................ 7 Gened Muscle Structwe............................................................................. 10 Ciliary Muscle Structure .......................................................... 12 Hl,unam................................................................................ 12 BK~S..................................................................................... 13 Accommodation........................................................................................... 14 Hm............................................................................. ............... 14 Bir& .................................................... .......... Thesis Objectives ......................................................................................... Section 1 The Functional Anatomy of the Curry Muscle in Four Avian Spceies.......... Introduction.............*......*...*...................*...............*................*................... Methods.......................................................................................*............... Results...............................*......................................................................... Chicken Muscle Fibre Groups and Subdivisioas ... ........ .....*.... Pigeon Muscle Fibre Groups and Subdivisions.............................. Kestrel Muscle Fibre Groups and SuMivisions........ .. ..... ...... Hooded Merganser Muscle Fibre Groups and Subdivisions..... ...... Asymmetfy...................................................................................... Discussion .........................................................................................*...*..... Species Accommodative Needs ...................................................... Role of the Cïl.iary Muscle in Accommodation...... ............ .......... Species Diaemces.................................................................0....... Asymmetry .............. ................................................................... Effect of Contraction ........... ... ..........*......................*.............. vii Section II The Functional Anatomy of the CüUry Muscle in Humons across Age .......... 72 htroduction. ................................................................................................. 73 Chary. Muscle Function.................................................................. 74 Ciiiary. Muscle Aging ...................................................................... 78 Morphologicai Changes with Age ..................cal.....................79 Functiod Changes with Age ............................................. Role of the Ciliary Muscle m Presbyopia.......................... Methods ...................................................................................................... Results ........................ ...............................................................................
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