Ansons and Davis
Diagnosis and Management of Ocular Motility Disorders
Published by Blackwell Publications - this is probably the best Orthoptics book you can buy. If you're a student or practicing Orthoptist you will probably not need to buy another book other than Ansons and Davis.
Eye
"It is an excellent book and it deserves to do well as it is destined to!"
British Orthoptic Journal, Vol 59, 2002
"a comprehensive text that will appeal to all orthoptists, opthalmologists and other opthalmic professions...an essential text for orthoptists."
Ansons and Davis