Retinoscope theory.pptx

Retinoscope is an objective refraction instrument used to
determine the spherocylindrical refractive error, as well as
observe optical aberrations, irregularities, and opacities.

The technique is called Retinoscopy/Skiascopy/Shadow Test

1. RETINOSCOPE THEORY Presenter- Shayri Pillai Liberia Eye Centre JFK Memorial Medical Centre LV Prasad Eye Institute India August 5 2019

2. INTRODUCTION Retinoscope is an objective refraction instrument used to determine the spherocylindrical refractive error, as well as observe optical aberrations, irregularities, and opacities. The technique is called Retinoscopy/ Skiascopy /Shadow Test Sihota , R. et.al. Parson’s: Diseases of the Eye. 22 nd Edition 2015. India. Page-59 AAO Clinical Optics. Section-3 2011-2012 Page-121

3. HISTORY Sir William Bowman in 1859, reported the movement of light and shadow effect. Use since 1873- reflecting mirror spot retinoscopes , externally illuminated. Modern streak design that brought significant change in 1927 , by Jack C. Copeland.

4. PRINCIPLE Retinoscope is based on the Focault’s Principle. When light is reflected from a mirror into the eye, the direction in which the light will travel across the pupil will depend upon the refractive state of the eye. Observation system: light path from patient's pupil,through mirror, to observer's retina AAO Clinical Optics. Section-3 2011-2012 Page-121

5. OPTICAL PRINCIPLE The illumination stage- Fundal area illuminated by the light reflected in the patient’s eye. Illuminated area serves as an object The reflex stage- The light rays reflected back from the fundus. It forms a reflex shadow in pupillary area.

6. Characteristic of the Reflex is based on: LOW ERRORS HIGH ERRORS SPEED High Low BRILLIANCE Bright Dull WIDTH Broad Narrow AAO Clinical Optics. Section-3 2011-2012 Page-124

7. AAO Clinical Optics. Section-3 2011-2012 Page-124 Characteristics of the moving retinal reflex on both sides of neutrality

8. If the retinoscope is tilted upward, reflex will move to the opposite direction in case of myopes . Same direction of retinoscopic light and reflex in case of hyperopes and emmetropes . No movement ( with working lens) at all in case of emmetropes .

9. The projection stage The image at the far point is located by moving the illumination across the fundus and noting the behavior of the luminous reflex seen by the observer in the patient’s pupil.

10. WORKING DISTANCE The distance from the retinoscope to the patient’s eye. D=1/F The length of average person’s arm is 66 cm. The power of the lens that focus parallel light rays at 66 cm is + 1.50 D or 50 cm is + 2.00 D

11. TECHNIQUES The main retinoscopy techniques are: Static Retinoscopy- Accommodation fully relaxed Working distance lens added or subtracted from the objective finding. Fixates letter at 6 m. Only Ametropia or emmetropia can be determined.

12. Dynamic Retinoscopy Accommodation is active No influence of working distance. Fixates at the bulb of retinoscope . Accommodative lag can be determined.

13. Dry Retinoscopy- Done without using cycloplegic drugs. Done in elderly patients. Wet Retinoscopy- Done with using cycloplegic drugs. Done in children and young adults.

14. TYPES OF RETINOSCOPE Reflecting Mirror Retinoscope Plane Mirror Retinoscope Priestley–Smith Retinoscope Self Illuminated Retinoscope Spot Retinoscope Streak Retinoscope

15. Left: Mirror retinoscope : C, concave mirror; P, plane mirror Right: Streak retinoscope Sihota , R. et.al. Parson’s: Diseases of the Eye. 22 nd Edition 2015. India. Page-60

16. EQUIPMENT The source of light for retinoscopy could be either external or internal. An external source of light is directed into the patient’s eye with the help of a mirror retinoscope . Alternatively an internal bulb is situated inside a self- illuminated retinoscope .

17. Priestley–Smith Retinoscope A plane mirror at one end and a concave mirror at the other. The mirrors project a circle of light into the patient’s eye through the pupil. Both the plane and the concave mirrors have a central hole 2.5 mm wide anteriorly and 4.0 mm posteriorly fitted with a low polar convex lens for viewing the reflex thus created. Either of the two mirrors can be used for retinoscopy.

18. REFLECTING MIRROR RETINOSCOPE ADVANTAGES: Cheaper than self illuminated Retinoscope . Reduces the refraction time and error. Can be used for pediatric patients. DISADVANTAGES: Requires a special light source. Glare from the source of light is annoying to the patient. To check the axis and amount of cylinder is difficult. Intensity and type of the beam cannot be changed or controlled.

19. SELF ILLUMINATED RETINOSCOPE Spot Retinoscope - Round Filament. Scooped in any meridian Used in examining children. Better for low level of astigmatism

20. Streak Retinoscope - Linear Filament Quickly change from plano mirror to concave mirror. Narrowing the width makes it easy to pin down the principle meridians. Better for high cyclinders .

21. Streak Motion- Hyperopic Patients Light focuses behind the retina. Streak movement in the same direction as the retinoscopei.e . displays with motion. Add plus lenses to bring the focusing point up to the retina

22. Myopic Patients Light focuses at the point before the retina Streak movement in opposite direction as the retinoscope . i.e. against movement Add minus lenses to move the focal point back onto the retina

23. Emmetropic Patients No motion of the reflex observed in the pupil. Also known as neutral motion.

24. A. Streak Reflex B. With movement C. Against movement AAO Clinical Optics. Section-3 2011-2012 Page-124

25. Nature of reflexes in Ametropia ( Plane Mirror) Myopic far point of accommodation located at a finite distance Infront of the eye Hyperopes far point of accommodation is located at some point behind the primary focal plane of the eye. Emmetropic eyes far point of accommodation is located at infinity

26. Retinoscopy with a plane mirror Effective source lies behind the plane of mirror ( commonly used) The rays of light forms the source goes parallel or slightly diverging. Doesnot cross between the source and the patient’s eye. WITH MOVEMENT- Hyperopia AGAINST MOVEMENT- Myopia

27. Retinoscopy with a concave mirror It is kept as the effective source in front of the plane of the mirror, so that the rays emitted from the source are more converging and cross at a certain distance between patient and the source. WITH MOVEMENT- Myopia AGAINST MOVEMENT- HYPEROPIA

28. Retinoscopy with a concave mirror. O1, the observed eye; O2, the observer’s eye. The image of the source of light (L) is formed at l1 (the immediate source of light) by the mirror. If O1 is hypermetropic a virtual image of l1 is formed on the line l1n, passing through the nodal point n as at h1. If O1 is myopic a real inverted image is formed as at m1. If the mirror is tilted downwards, as shown by the dotted line, l1 moves to l2, h1–h2 and m1–m2. This shows that the shadow seen by the observer moves in the opposite direction in hypermetropia and in the same direction in myopia. Sihota , R. et.al. Parson’s: Diseases of the Eye. 22 nd Edition 2015. India. Page- 60

29. Light Pathway in Retinoscopy If the eye has 1 D of myopia Retinoscopy is performed at a distance of 1 m, no shadow will be visible; the pupil will be either completely illuminated or completely dark. The method, therefore, consists of placing lenses in front of the eye until no shadow is seen.

30. The course of the emergent rays in myopia of 1 D and at the point of reversal. So long as the light source l1 is in the pupillary area of O2, the pupil of O1 appears uniformly illuminated, and there is no shadow. Directly l1 passes to l2 the light is completely cut off, so that the pupil of O1 becomes completely dark. Sihota , R. et.al. Parson’s: Diseases of the Eye. 22 nd Edition 2015. India. Page- 61

31. Myopia with more than 1 D From a plane mirror at a distance of 1 m and the mirror is tilted in any direction the light —the shadow at the edge of the light—moves across the pupil in the opposite direction.

32. The course of incident rays in myopia more than 1 D. Sihota , R. et.al. Parson’s: Diseases of the Eye. 22 nd Edition 2015. India. Page- 61

33. Sihota , R. et.al. Parson’s: Diseases of the Eye. 22 nd Edition 2015. India. Page- 63

34. Thank you! Excellence Equity Efficiency L V Prasad Eye Institute