Retinoscopy dr.asif siddiqui

Retinoscopy

1. RETINOSCOPY Dr.Asif Ullah Siddiqui MS 1 st Year Department of Ophthalmology Shadan Institute of Medical Sciences

2. Definition & Principle It is an objective method of finding the refractive error based on the principle of neutralization. When the light of retinoscope is reflected into the eye, the direction in which light will travel in the pupillary area depends on the refractive status of the eye. Retinoscopy is also caled as skiascopy , pupillocopy , shadowscopy , umbrascopy , scotoscopy .

3. History Sir William Bowman - in 1859 observed linear fundus reflex using a Helmholtz ophthalmscope . Ferdinand Cuignet - in 1873 classified variable reflexes into myopia, hyperopia and astigmatism. also gave misleading term " keratoscopie " to his technique. Edmond Landolt - suggested the source of reflex is fundus rather than cornea. M.Mengin - in 1878 published accurate explanation, proving Landolt's suggestion. H.Parent - in 1880 introduced quantitative refraction test, measuring the exact amount of refractive error using lenses. also coined the term " retinoscopie ". Jack C.Copeland - in early 1920s introduced streak retinoscope , he is known as father of streak retinoscopy . Hand held retinoscopes began to be overtaken in 1970s by Auto refractors making use of infra-red light.

4. Prerequisites for Retinoscopy Darkroom preferably 6 m long, or which can be converted into 6 m by use of a plane mirror. Trial box containing spherical and cylindrical lenses of variable plus and minus powers, a pinhole, an occluder and prisms. Trial frame preferably adjustable type which can be used in children as well as in adults. Vision box, A Snellen’s self illuminated vision box. Retinoscope .

5. Types of Retinoscopes Mirror Retinoscope : Cheaper. Source of light – External. Mirror – plane or pristley -smith mirror i.e , combination of plane and concave mirrors. Self-illuminated Retinoscope : Costly but handy. Spot retinoscope and Streak retinoscope Streak retinoscope is more popular, in it the usual circular beam of light is modified into a linear streak, it uses planocylindrical retinoscopy mirror and is more sensitive in detecting astigmatism. Generally a Plane mirror is used for retinoscopy . In patients with hazy media and high degree of ametropia concave mirror is more useful.

6. Parts of a Retinoscope Retinoscope consists of a Head, Neck and Tail. Observing the optics of retinocope we find two main systems Projection system Light source Condensing lens Focusing sleeve Current source Observation system Peep hole

7. Types of Retinoscopy Dry Retinoscopy Done without the use of cycloplegic drugs. Done in elderly individuals. Wet Retinoscopy Done with the use of cycloplegic drugs. Done in children and young adults. Static Retinoscopy Done by relaxing the accommodation by cycloplegic drugs or by asking the patient to look at a distant target. Done in elderly and young adults. Dynamic Retinoscopy Done by the use of active accommodation by asking the patient to look at a near target. Done rarely in clinical practice.

8. Use of cycloplegics in retinoscopy Cycloplegics are drugs which cause paralysis of accommodation and dilate pupil , used in retinoscopy when accommodation is suspected abnormally active and will hinder exact retinoscopy . Such situation is seen in children and hypermetropes .

9. Mydriatics and Cycloplegic Agents in Retinoscopy

10. Procedure The examiner sits at a distance of 1 m from the patient. Light is thrown into the patients eye and the examiner observes the movement of red reflex in the pupillary area in both horizontal and vertical meridians by moving the retinoscope .

11. Procedure: The results are interpreted as : Movement of red reflex with the movement of the retinoscope – Emmetropia , Hypermetropia , Myopia <1D Movement of the red reflex opposite to the movement of the retinoscope – Myopia >1D No movement of red reflex – Myopia of 1D

12. Neutralization When the red glow in the pupil doesn’t move the patient has myopia of 1 D. When the red glow moves with the movement of the plane mirror or when the red glow moves against the movement of the plane mirror, the observer has to estimate the degree of refractive error by neutralizing the movement. By addition of increasingly convex (+) spherical lenses when movement is with the plane mirror or concave (-) spherical lenses when movement is against the plane mirror. If its simple spherical error, the movement of the red reflex will be neutralized in both vertical and horizontal meridian.

13. Neutralization In astigmatic refractive error, one meridian is neutralized by adding appropriate cylindrical lens with its axis at right angle to the meridian to be neutralized. Examples:

14. Transposition Transposition is the conversion of a written lens power from plus-cylinder form to minus-cylinder form or vice versa. Simple Transposition and Toric Transposition.

15. Simple Transposition 3 Steps Step 1 If axis is less than 90 add 90 more to it. If axis is more than 90 subtract 90 from it. Step 2 Retain Cylinder power but change the sign. Step 3 New spherical power is an algebric sum of the old spherical and cylinder powers.

16. Simple Transposition Examples -5.00 DS / -3.00 DC 90° -8.00 DS / +3.00 DC 180° +2.00 DS / +1.00 DC 180° +3.00 DS / -1.00 DC 90°

17. Toric Transposition Toric formula is written as a fraction, the numerator and the denominator comprises both the base curve and the cylinder necessary to give the required combination. A toric astigmatic lens is made with one spherical surface and one toric surface. The principal meridian of weaker power of the toric surface is known as the base curve of the lens.

18. Toric Transposition Steps Transpose the given prescription to one having a cylinder of the same sign as the base curve which to be used (simple transposition) The spherical surface is given by subtracting the base power from the sphere in (1). This is written as the numerator of the fraction. Fix the cylindrical base curve with its axis at right angle to the cylinder in (1). Add to the base curve the cylinder in (1) with its axis at right angles to that of the base curve.

19. Toric Transposition Example +3.00 DS +1.00 DC 90° BC -6.00 1. Simple transposition +4.00 DS -1.00 DC 180° 2. The spherical surface is given by subtracting the base power from the sphere in (1). This is written as the numerator of the fraction. +4.00 –(-6.00) = +10.00 DS 3. Fix the cylindrical base curve with its axis at right angle to the cylinder in (1). -6.00 DC 90° 4. Add to the base curve the cylinder in (1) with its axis at right angles to that of the base curve -6.00 +(-1.00) = -7.00 DC 180° +10.00 DS -6.00 DC 90° -7.00 DC 180°

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