Retinoscopy

retinoscopy

1. Retinoscopy Shahana

2. Introduction Retinoscopy is an objective method of measuring the optical power of the eye. We use a retinoscope to illuminate the inside of the eye and to observe the light that is reflected from the retina. These reflected rays change as they pass out through the optical components of the eye, and by examining just how these emerging rays change, we determine the refractive power of the eye . Pupilloscopy,shadowscopy,skiascopy .

3. History Cuignet 1873 -first description and utilising a retinoscope . AJ cross -1902 teaching a course in it. Greet 1895,axenfeld,heine,and hess 1898 -original work on dynamic retinoscopy .

4. Types of retinoscopy Static retinoscopy - Refractive error determined when patient fixates an object at a distance of 6cm with accommodation relaxed. Dynamic retinoscopy - The refractive state is determined while the subject fixates an object at some closer distance,usually at or near the plane of retinoscope itself with accommodation under action.

5. Types of retinoscopes Reflecting mirror retinoscope - Plane mirror - Priestley – smith’s mirror [plane and concave mirrors] Self illuminated retinoscope Spot retinoscope Streak retinoscope

6. Reflecting mirror retinoscope A perforated mirror by which the beam is reflected in to the patients eye and through a central hole the emergent rays enter the observer's eye.

7. Self illuminated retinoscope The light source and the mirror are incoporated in one

8. Spot vs Streak retinoscope The spot retinoscope reflects a beam of light from a circular source, where as the streak retinoscope emits a beam from a line source.

9. Retinoscope and its parts Retinoscopy consist of a head, neck and tail. Observing the optics of retinoscope we find two main systems Projection system: Light source - A bulb with a linear filament that projects a line or streak of light. Condensing lens - Resting in the light path, the lens focuses rays from the bulb onto the mirror Focusing sleeve - The sleeve also varies the distance between the bulb and lens to allow the retinoscope to project rays that either diverge (plane mirror effect) or converge (concave mirror effect). Hence, the sleeve is also called the vergence control. Current source - This is provided by a battery in the handle Observation system: Peep hole

10. Principle Retinoscope works on focault‘s principle It state that the examiner should stimulate infinity at the working distance to obtain refractive error

11. Working distance The distance between patients eye and the observer while performing retinoscopy is called WD. Normally 66 cm [+1.50D] or 50cm[+2.00D] To compensate the WD we use working distance lens.

12. Fixation target The target given to the patient should be 6/60 in snellen chart. It is given to the patient to relax accommodation during retinoscopy .

13. Requirements Dim room Retinoscope Trail lenses Trail frame VA chart

14. Procedure The patient is instructed to watch the letter on distance chart. The patient right eye should be examine with the examiner´s right eye with the retinoscope in right hand and viceversa . WD should be maintained an arm length distance . The examiner should stay as close to visual axis as possible. The examiner should not obstruct the view of target.

15. Examine the movement in horizontal meridian and vertical meridian without any lenses. - Three possible reflex may be observed: With motion – the patient is hyperopic,emmetropic or myopic less then dioptric value of the WD. Against motion – patient's myopia is greater the dioptric value of WD Neutrality – patient‘s myopia is equal to dioptric value of WD.

16. Neutralising spherical power E g : patients ref error is +3.00Dsph We will get with movement without any lens @ 66cm. There are two ways: 1. By placing WDL Your Rx =amount of DS added 2. Without WDL Your Rx = amount of DS added - WD

17. PROPERTIES OF REFLEX BRIGHTNESS- Dim (far from neutralization) bright(close to neutralization) WIDTH – narrow (far from neutralization) wide(close to neutralization ) SPEED – slow (far from neutralization) fast (close to neutralization ) MOVEMENT – with (need more plus) against(need more minus)

18. Recognising the astigmatism Break in the alignment between the reflex in the pupil and the band outside it is observed when the streak is not parallel to one of the meridian Neutralising astigmatism with two sphere First neutralize one axis with appropriate sphere Then keep on changing the sphere till the second axis is neutralized Astigmatism is measured by the difference between the 2 sphere.

19. Neutralising with a sphere and cylinder First neutralize one axis with an sph lens Neutralize the other axis with a cyl lens at appropriate orientation. The spherical cyl gross retinoscopy may be read directly from the trail lens apparatus.

20. End point of retinoscopy Neutral – the end point of retinoscopy means neutralization of red reflex in any meridian with the movement of the mirror. Reversal – the real endpoint for retinoscopy . -over correction by 0.25D should cause reversal of the movement.

21. Reason for false reading Inexperience Not aligning with visual axis of the patient Definite WD is not maintained Defect in trail lenses Lack of patient's coordination.

22. Problems in retinoscopy Red reflex may not be visible – small pupil,hazy media and high degree of refractive error. Retinoscopy in nuclear cataract shows index myopia in early stages Scissoring shadow may be seen in healthy cornea but with unusual difference in curvature in the centre and the corneal opacities.

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