Modern System of Ophthalmology (MSO) is a series of multiple volumes, planned with a very specific aim to cater to the needs of residents in ophthalmology. Volume editors of this series make a team of like-minded and devoted teachers from different subspecialties. Theory and Practice of Squint and Orthoptics in its third edition, has been thoroughly updated and comprises basic text which describes the fundamental principles of squint and orthoptics. It includes complete and upto- date material arranged in a simple and lucid style. It has been written primarily keeping in mind the requirements of the residents in ophthalmology and students of orthoptics and optometry. It will also act as a useful handy guide on strabismus for the practising ophthalmologists, optometrists and orthopticians.