This book takes a deep dive into the complex world of the eye and contact lenses through four distinct chapters. The first explores ocular anatomy and ametropia correction, while comparing the effects of spectacle lenses to contact lenses. The second delves into the details of contact lens parameters, also detailing their indications, contraindications, and possible complications when fitting contact lenses. The third chapter unveils the secrets of contact lens fitting, providing in-depth training for optometrist contactologists to achieve accurate fittings. Finally, the fourth chapter focuses on specific cases, such as corneal deformities, requiring distinct adaptive approaches. Overall, this book offers a comprehensive journey from the structure of the eye to the nuances of contact lens fitting, covering a variety of situations to educate the reader in the complexities of contactology.