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Revision of Optics

Revision of Optics. For Postgraduates. General Considerations. Geometrical optics The science of geometrical optics consists of the study of the passage of light through various media. Clinical optics Consists of study of the basic optical principles of the human eye. Geometrical Optics.

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Revision of Optics

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  1. Revision of Optics For Postgraduates

  2. General Considerations • Geometrical optics The science of geometrical optics consists of the study of the passage of light through various media. • Clinical optics Consists of study of the basic optical principles of the human eye

  3. Geometrical Optics

  4. I. Light • Light is a form of energy or electromagnetic radiation which is capable of stimulating the photoreceptors of the retina to produce the sensation of sight • The visible spectrum • Wave theory of light - Wave fronts - Wave motion - Phase difference (coherent & incoherent)

  5. II. Reflection • Definition • Laws of reflection (2) • Reflection by plane mirrors • Reflection by spherical mirrors: - Concave mirrors - Convex mirrors

  6. III. Refraction • Definition • Laws of refraction • Factors affecting refraction of light • Real and Apparent depth • The critical angle &Total internal reflection

  7. Refraction by Lenses (A) Spherical lenses • The principal focus of a convex lens • Conjugate foci of a convex lens • Types of spherical lenses a. Convex spherical lenses - Plano-convex - Biconvex - Convex meniscus (concavo-convex) b. Concave spherical lenses - Plano-concave - biconcave - Concave meniscus (Convexo-concave)

  8. Images formed by convex lenses • Images formed by concave lenses N.B. The nature and position of the image depends upon the position of the object.

  9. (B) Astigmatic lenses ● Cylindrical lenses - Convex cylinder - Concave cylinder - Axis of the cylindrical lens - Power of the cylindrical lens - Refraction by a cylindrical lens ● Toric lenses (sphero-cylinderical lens) - Image formed by the toric lens ► Sturm of conoid ► Interval of sturm ► The circle of least diffusion

  10. Cross cylinder and its uses • Maddox rod and its uses

  11. IV. Refraction by Prisms • Definition of the prism • Refraction by prisms • Nomenclature (Notation) of prisms - The prism dioptre - Angle of minimum (apparent) deviation - The centrad - The apical refracting angle

  12. Use of prisms in ophthalmology • Diagnostic • Therapeutic • In ophthalmic instruments

  13. Clinical Optics

  14. Optical Considerations of Normal Eye

  15. Cardinal Points of the Eye • The nodal point • The anterior (First) principal focus • The posterior (Second) principal focus • The centre of rotation of the eye • The Optical axis • The visual axis • The central pupillary line • The angle Alpha • The angle Gamma • Angle Kappa

  16. The Optical Constants of the Eye • Refractive indices of the ocular media • Radii of curvature of the central region of the refracting surfaces of the eye • Positions of refracting surfaces of the eye

  17. The Dioptric System of the Eye • The Schematic eye ► Ophthalmic properties • The Reduced eye ► Ophthalmic properties

  18. The Formulation of Retinal Images • Construction of retinal images • Calculation of size of retinal image & factors affecting it.

  19. The Emmetropic Eye • Optical principles • The dioptric system of the eye

  20. Optical aberrations of the eye • Spherical A • Chromatic A • Chromatic difference of magnification • Peripheral A a. Oblique astigmatism b. Coma aberration c. Image distortion • Curvature of the field • Diffraction • Decentration

  21. Significances of optical aberrations of the eye • The circles of least diffusion • Stenopaeic aperture (small pupil size) - Advantages - Clinical applications

  22. Ametropia(Errors of Refraction) • Myopia ● Aphakia • Hypermetropia ● Anisometropia • Astigmatism ● Aniseikonia • Presbyopia

  23. Accommodation • Definition • Mechanism • Far point (punctum remotum) • Near point (punctum proximum) • Range of accommodation • Amplitude of accommodation • Measurment of accommodation

  24. Accommodation in different refractions • Variations of accommodation power with age • Anomalies of accommodation • Relative accommodation • Reserve accommodation

  25. Convergence • Definition • Types • Important definitions • Measurement of near point of convergence • Measurement of amplitude of convergence • Relative convergence

  26. Association of accommodation & convergence • Accommodative-Convergence/Accommodation ratio (AC/A ratio) • Dissociation of accommodation & convergence • Anomalies of convergence

  27. Catoptric (Purkinje-Sanson) images • Definition • Optical principle • Characters • Uses in ophthalmic practice

  28. Heterophoria • Definition • Types • Investigations (especially optical principles of): - Maddox rod - Maddox wing - Use of prisms • Treatment: especially role of prisms

  29. Paralytic squint • Hess screen

  30. Visual Acuity • Optical principles of measurement of distant vision • Optical principles of measurement of near vision

  31. Retinoscopy&Verification of Refraction

  32. Spectacle Lenses • Lens material (glass & plastic) • The standard forms of lenses in clinical practice: 1. Spherical lens 2. Toric lens 3. Lenticular lens 4. Aspheric lens

  33. Back vertex power (BVP) • Back vertex distance (BVD) • Spectacle magnification • Optical aberration of lenses • Decentring of lenses

  34. Specification (Notation) of lenses in prescriptions: • A spherical lens alone • A cylindrical lens alone • A combined spherical & cylindrical lenses

  35. Spherical equivalent • Transposition of lenses: • Simple T : - Spheres - Cylinders - Spheres & cylinders 2. Toric T

  36. Bifocal lenses • Definition • Indications • Types • Optical principles of bifocals • Optical defects of bifocals • The ideal bifocal lens

  37. Lenses with Antireflection • Characters • Optical principles

  38. Verification of spectacle lenses • Methods

  39. Instruments

  40. Instruments • Slitlamp & accessories • Direct ophthalmoscope • Indirect ophthalmoscope

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