Presentation on Retinoscopy and it's applied aspects

Presentation on retinoscopy

1. Retinoscopy

2. DEFINITION : Retinoscopy also known as ‘ Skiascopy’ or ‘ shadow test’ is an objective method of finding out the error of refraction by the method of neutralization. PRINCIPLE : It is based on the fact that when light is reflected from a mirror into the eye, the direction in which the light travels across the pupil depends upon the refractive state of the eye. TYPES OF RETINOSCOPY : Static retinoscopy refers to the procedure performed without active use of accommodation. Dynamic retinoscopy implies when the procedure is performed for near vision with active use of accommodation by the patient.

3. Prerequisites : Darkroom – 6m long or converted into 6m by use of a plane mirror. Trial box – containing spherical and cylindrical lenses, pinhole, occlude and prism. Trial frame Snellen’s self illuminated vision box. Retinoscope. SNELLEN’S VISION BOX TRIAL FRAME RETINOSCOPE

4. TYPES OF RETINOSCOPE : Mirror retinoscope – cheap - most commonly employed - source of light is required, which is kept above and behind the head of the patient. - mirror retinoscope may consist of a single plane mirror or a combination of plane and concave mirror( 9 Priestley-Smith mirror). 2) S elf-illuminated retinoscope - costly but handy - further two types : spot retinoscope streak retinoscope MIRROR RETINOSCOPE STREAK RETINOSCOPE

5. PROCEDURE : The patient is made to sit at a distance of 1m from the examiner. However distance of 5/6 is preferred in clinical practice. With the help of retinoscope, light is thrown onto the patient’s eye, who is instructed to look at a far point. With use of cycloplegics, patient can look directly into the light. Through a hole in the retinoscope’s mirror, the examiner observes a red reflex in the pupillary area of the patient. The retinoscope is moved in the horizontal and vertical meridian keeping watch on the red reflex. It is noted for speed and brilliance,width of reflex , swirling of reflex .

6. USE OF CYCLOPLEGICS IN RETINOSCOPY : Cycloplegics causes of paralysis of accommodation and dilate the pupil. These are used when the examiner suspects that accommodation is abnormally active (seen in children and hypermetropes). When retinoscope is performed after instilling cycloplegic drugs is called ‘ wet retinoscopy ’. Commonly used drugs are : 1% Atropine – used thrice daily for 3 days before retinoscopy. Effect lasts for 10-20days. 2% Homatropine – one drop every 10 min for 6 min and retinoscopy is performed after 1-2 hours .Effect lasts for 48-72 hours. 1% Cyclopentolate – one drop is instilled after 10-15 minutes for 3 times (Havener’s syndrome) retinoscopy is performed 60-90 minutes after .Effect lasts for 6 to 18 hours. 10% phenylephrine

7. OBSERVATION AND INFERENCE : Depending upon the movement of the red reflex when a plane mirror retinoscope is used at a distance of 1m the result is interpreted as : No movement of the red reflex – indicates myopia of 1D With the movement of red reflex along the movement of the retinoscope indicates either emmetropia, or hypermetropia or myopia of less than 1D. Against movement of red reflex to the movement of retinoscope implies myopia of more than 1D.

8. NEUTRALIZATION : When the red glow in the pupil does not move then we know patient has myopia of 1D. To estimate the degree of refractive error ,when the red reflex was moving with the movement of the plane mirror, the movement of red reflex is neutralized by addition of increasingly convex (+) spherical lens. When the red reflex was moving against the movement of plane mirror ,it is neutralizes by addition of concave (-)spherical lens . In presence of an astigmatic refractive error ,one meridian is neutralized by adding cylindrical lens with its axis at right angle to the meridian to be neutralized.

9. END POINT OF RETINOSCOPY : With simple plane mirror retinoscope – the end point pf retinoscopy is neutralization of red reflex in all the meridian ie . either no movement or just reversal of the movement. With a streak retinoscope – the end point streak disappears and the pupil appears completely illuminated or completely dark.

10. PROBLEM IN RETINOSCOPY : 1) Red reflex may not be visible or may be poor : seen with – small pupil - hazy media - high degree of refractive error Can be overcome by causing mydriasis or use of converging light with concave mirror retinoscope. 2) Changing retinoscope finding – due to abnormally active accommodation can be corrected by use of cycloplegics. 3) Scissors shadow – seen in patients with irregular astigmatism with dilated pupil. 4) Conflicting shadow – seen in patient with irregular astigmatism. 5) Triangular shadow – in patient with keratoconus, with its apex at the apex of cone. On moving the mirror, the triangular reflex appears to swirl around its apex (yawning reflex)