Basic Clinical Optics

Chapter one begins with the introduction of fundamental theories of light and vision, traversing through the primeval thinking to the current understanding, and acknowledging the early scientists without whose efforts this body of knowledge would have amounted to nothing. It introduces the reader to the concepts of wavefront, optical ray and the fundamental wave properties of light such as reflection, refraction, diffraction, polarization and interference. It further demonstrates how the properties of light are observed in nature as colours of sky and seas; moonlight; eclipse, day and night. The chapter prepares the reader and sets the stage for detailed discussion of properties of light as applied in clinical settings in the subsequent chapters.
Chapter Two discusses reflection as one of the fundamental properties of light. Using mirror as a model, it demonstrates how images are formed through reflection. It explains the laws and rules of reflection, mirror formula and finally, it considers the issue of total internal reflection as applied in keratometry where a refractive medium can also exhibit reflective properties. At the end of this chapter, the reader will be able to trace and draw ray diagrams of images formed by mirrors.
Chapter Three introduces refraction as another fundamental property of light and explains the laws and rules of refraction. Using lens as a model, it discusses various types and shapes of lenses and how images are formed through refraction. It further demonstrates how refraction can lead to optical illusions observed in nature as heat haze, mirage, apparent depth illusion and rainbow effect. Finally, it discusses the lens equation and how the human eye is considered as a compound lens system. At the end of this chapter, the reader will be able to trace and draw ray diagrams of images formed by lenses.
Chapter Four continues further discussion on refraction and lenses. It expands the knowledge on lens properties, lens transposition and ophthalmic glass prescriptions. It demonstrates how refraction can lead to optical aberrations observed in lens system as spherical aberration, chromatic aberration, astigmatism, coma and Petzval curvature. Finally, it discusses lens effectivity, contact lenses, intra-ocular lenses and biometry. At the end of this chapter, the reader will be able to neutralize lenses, perform lens transpositions, interpret glass prescriptions and calculate intra-ocular lens powers
Chapter Five introduces the reader to the concept of optical deviation, image displacement and dispersion of light. Using prism as a model, it discusses the concepts of prism base direction, deviation power, prism neutralization, splitting/dividing/sharing prism, dispersion and dispersive power of prism. It also discusses the concepts of chromatic aberration, spectrum formation and rainbow effect. It establishes prism as the basic building block of lenses. Using ample diagrammatic illustrations and practical solved examples, it simplifies the knotty issues encountered in calculations involving prismatic effect, compounding and resolving of prisms. Finally, it discusses the issues of combined/compound prisms and the various applications of prism in the management of patients with refractive, strabismic and orthoptic anomalies. At the end of this chapter, the reader will be able to decode prismatic prescriptions, split, combine and resolve prisms with minimal effort.
Chapter Six accumulates and summarizes all the knowledge learnt from the previous chapters and use it to demonstrate how compound optical system could be designed and built from simple optical systems. It discusses in detail the optics of simple microscope, compound microscope, slit lamp biomicroscope, telescopes, telemicroscope, image minifiers, direct and indirect ophthalmoscopes. At the end of this chapter, the reader will be able to draw and explain the optics of basic optical instruments used in the ophthalmic practice.