streak retinoscope

STREAK RETINOSCOPE:Welch Allyn®

Elite™ REF 18245 PREPARED BY:

Anis Suzanna Binti MohamadA 123369

OVERVIEW

i. what is streak retinoscope

ii. basic principleiii. advantagesiv. Disadvantagesv. Conclusion

INTRODUCTION

• Retinoscopy - an objective method of measuring the optical power of the eye.

• Retinoscope - an instrument that we used to illuminate the inside of the eye, and to observe the light that is reflected from the retina.

• By examining just how these emerging rays change, we determine the refractive power of the eye.

• According to the Dictionary of Optometry And Visual Science; 5th Edition,pg:267, streak retinoscope is a retinoscope which projects into the patient’s eye an oblong streak which can be adjusted in width and rotated in various meridians.

• There are two types of retinoscope such as:– Spot retinoscope– Streak retinoscope

What is streak retinoscope?

The retinoscopehow it works

“ There’s less in a retinoscope than meets the eye……..”

Paul (“Doc”) Berry

Basic principle in streak retinoscope

• There are two systems operating in streak retinoscopy:

1) Projecting system2) Observation system

External part of streak retinoscope

1) Projection system

• Main purpose:– To illuminates the retina –Contains the major components such as:

Light sourceCondensing lensMirror Focusing sleeveCurrent source

Function of each components in Projection system

Components in projection system

Functions

Light source • A bulb with linear filament that projects a line of light or streak

Condensing lens • the lens that responsible for focusing the rays from the bulb onto the mirror

Mirror • bends the path of the light at right angle to the axis of the handle, therefore the beam projects from the head of the retinoscope

Focusing sleeve/ vergence control

• to project the rays either diverge (plane mirror effect) or converge (concave mirror effect)• sleeve changes the focus (vergence) by moving bulb up or down

Current source • Consist of battery in handle (rechargeable/replaceable)• Corded handle with connected to the electrical source

Figure 2.4 Usual method of vergence control (lens is fixed). Copeland type.

Figure 2.5 Alternative method of vergence control (bulb is fixed). Welch Allyn type.

Current sources

Corded handle Battery handle

2) Observation system

• Main purpose:– To allows the observer to see the retinal reflex of the

patient.

Light pathway in observation system

Light path from the patient’s retina •Light reflected by illuminated retina enters the retinoscope•Rays emerging from the retina pass through and acted upon by optical component of the eye.

Light pass trough the mirror •The light passes through an aperture in the mirror and out the peephole at the back of the head of retinoscope.

Light go onto the observer’s retina •The observer can observe the retinal reflex or movement of the streak through the peephole.

From observation, the observer can see the characteristics of the moving retinal reflex. The observer can detect refractive errors such as myopia,hyperopia, or astigmatism. The observer can measure the condition by placing lenses in the path of the retinal reflex. When the correcting lens create neutrality, this is the power of the patient’s refractive error.

Overall system of the streak retinoscopeThe retinoscope emit

rays of light that illuminate the retina

(RPE & choroid)

Turning the sleeve will also rotated the

projection streak through the condensing lens

Raising or lowering the sleeve will make rays diverge by action of

the mirror

Light reflected by illuminated retina will pass through optical component and enter the retinoscope

The light passes through an aperture in the mirror and

out the peephole at the back of the head of

retinoscope.

The observer can observe the retinal reflex or

movement of the streak through the peephole.

Advantages of Elite™ Retinoscope

• Provides 2.8X the brightness of standard retinoscopes • Superior streak quality -easy in patients with small pupils • Crossed linear polarizing filter eliminates bothersome glar

e from trial lenses • External focusing sleeve• Sealed optics keep the lenses cleaner• Fits all Welch Allyn 3.5 V power sources

Welch Allyn 18245 Streak Retinoscope

Disadvantages of Elite™ Retinoscope

• The transparent sealed optics easily have the finger print.

• The light too bright– Induces pupil constrict

• The batteries will easily lasting– The bulb is bright

Conclusion

• As we have seen, retinoscopy is an essential technique in optometry field as it can be very helpful to the patient such as children, nonliterate, hearing impaired, language disorder, or indecisive.

• Whatever the brand that observer used not determine the accuracy, the endpoint lies in the observer’s successful performance and interpretation of the art.

References:

BooksJohn M. Corboy,M.D., David J. Norath, and Richard Reffner. The Retinoscopy Book: An

Introductory Manual for Eye Care Professionals. University of Honululu,Hawaii: SLACK Incorperated, 1996.

George E. Garcia,M.D. Handbook of Refraction. Boston : Little, Brown and Company. 1989.

David B. Henson. Optometric Instrumentation. Oxford: Butterworth Heinemann. 1996.David B. Henson. Optometric Insrumentation. London : Butterworth& Co. (Publishers)

Ltd. 1983.Michel Millodot. Dictionary of Optometry And Visual Science. Oxford : Butterworth

Heinemann. 2000.

Internet sources Welch Allyn Corporation, “ Retinoscope”. 17 Jan. 2010 <

http://www.welchallyn.com/wafor/students/Optometry-Students/Retinoscope_2007_05_09.htm>.

Welch Allyn Corporation, “ Optometry Student Instruments”. 16 Jan. 2010 <http://www.welchallyn.com/wafor/students/Optometry-Students/default.htm >

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