Written to help trainee ophthalmologists, this textbook is now the recognised text on optics for the examinations of the Royal College of Ophthalmologists and the Royal Surgical Colleges. It approaches the subject from first principles and assumes no previous knowledge of optics. The book has been kept as simple as possible and is liberally complemented with diagrams designed to be easily understood and memorised. Only the most fundamental and clinically useful mathematical formulae are quoted, and the optical principles are applied to clinical situations. Ophthalmology examinations have changed substantially since the last edition was written and a total rewrite of this essential guide has become necessary. The third edition has been made more comprehensive and detailed to keep up with these changes and incorporates three new chapters: refractive surgery, contact lenses and lasers. Other new material includes photometry, visual acuity, contrast sensitivity, colour vision, absorptive lenses, fluorescence, ultrasound, and the specular microscope.