Module 6 Section 1
 

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Module 6:

 Retinoscopy in Minus Cylinder  
 

Section 1:

 Basic Concepts of Retinoscopy 
     
   
 

 

 

This Module assumes that you are familiar with the various refractive states of the eye,  basic clinical optics,  and the operation of the phoropter.

Introduction

The retinoscope was invented by ophthalmologist Jack Copeland.  The original spot retinoscope has been refined to the modern streak retinoscope.   The retinoscope projects a beam of light into the patient's eye through the pupil.  Through the peep-hole in the scope the observer sees a light reflex coming from the patient's pupil.  By observing the behavior of the reflex under certain conditions,  the observer can objectively determine the refractive error of the patient's eye. 

Retinoscopy is used in conjunction with refractometry in order to arrive at a glasses correction for someone with a refractive error (an ammetrope).  Retinoscopy is an objective measure of the refractive error,  meaning the process and result are not dependent upon patient responses.  Retinoscopy is particularly valuable in situations where communication difficulties inhibit the refractometric process, such as the examination of an infant, a deaf person, a stroke victim, or someone who doesn't speak your language.

Retinoscopy gives you a starting point for refractometry.  Retinoscopy also increases the accuracy, speed, and efficiency of refractometry on any patient with an unknown or questionable refractive error.  With retinoscopy you usually have a very good idea of what the endpoint should be even before you start refractometry.

How does manual retinoscopy compare to auto-refractor results?  Although late-model auto-refractors give excellent retinoscopic results on the majority of patients,  manual retinoscopy offers some distinct advantages.

  • If you don't have an assistant to perform auto-refraction for you,  manual retinoscopy performed by an experienced retinoscopist is actually a faster procedure.  A good retinoscopist can scope both eyes in less than a minute.
  • Auto-refractors can be "fooled" by irregularities (e.g. corneal edema, cataracts) in the ocular media.  The advantage of manual retinoscopy is that you can "see" the media irregularities (by the behavior of the reflex) and immediately be aware of conditions that may compromise the refraction.  The best auto-refractors are the ones with auto-K capabilities.  Using the keratometry results to double check the cylinder and axis readings can alert you to questionable auto-refractor results.

The retinoscope

The most widely used retinoscopes are the Copeland Optec 360 and the Welch-Allen.  They consist of an optical head,  a sleeve,  and a battery handle.  The optical head projects a slit beam called a "streak" from one side of the head,  and it has a peephole on the other side of the head.  The sleeve assembly allows the streak of light to be converged or diverged by moving the sleeve up or down.  The sleeve is also used to rotate the orientation of the streak.

Head

 

Sleeve

 

Battery handle

Various retinoscopic techniques make use of different sleeve positions.  There is more than one way to perform retinoscopy.  The method described in this Module uses the retinoscope in what is termed the "sleeve up" position,  as originally described by Jack Copeland.  It is very important to realize that these two popular retinoscopes do not function in the same manner.  The Copeland Optec instrument creates the sleeve-up effect with its sleeve in the upper most position (arrow).  The Welch Allen instrument creates the sleeve-up effect with its sleeve in the downward most position (arrow).

The sleeve-up position 

The sleeve-up position can be confirmed by projecting the streak onto your hand at about a foot away from the retinoscope.  In the sleeve-up position the streak will be maximally wide and out of focus.  With the sleeve all the way to the opposite position (sleeve-down),  the steak will form a thin, focused line on your hand. 

Appearance of streak in sleeve-up position
Appearance of streak in sleeve-down position

The method described in this Module requires the sleeve-up position (wide streak,  out of focus) at all times.  With the Copeland Optec,  this is achieved with the sleeve maximally up.  With the Welch Allen, this is achieved with the sleeve maximally down.  The "sleeve-up" position always refers to the streak being maximally wide and out of focus.

Using the retinoscope

Hold the retinoscope in one hand so that you can view the patient's eye through the peephole of the scope.  Depending upon the model,  your thumb or index finger of the same hand is used to hold the sleeve in the sleeve-up position and to rotate the sleeve, which rotates the streak.

The Welch Allen scope is turned on by a button/slide at the top of the handle.  The Copeland 360 is turned on by pulling a knob at the bottom of the handle.

The streak is passed across the pupil of the eye with the streak in a perpendicular orientation to the direction of the movement.  In the following illustrations the center of the streak is clear so that you can easily see what is behind it.

In this illustration the long part of the streak is oriented with the 90 degree line on the optical protractor,  but the streak is being moved along the 180 degree meridian.  This is called "streaking 180".
In this illustration the long part of the streak is oriented with the 180 degree meridian on the optical protractor,  but  the streak is being moved along the 90 degree meridian.  This is called "streaking 90".

The patient setup

The most convenient way to perform retinoscopy on cooperative people is with a phoropter.  It is easiest to perform retinoscopy on young children with the use of loose lenses or a refraction bar.  This module discusses retinoscopy with a phoropter.

The patient is placed behind the phoropter and the following adjustments are made:

  • The PD is properly set for the patient.
  • The phoropter is aligned so that the patient can view the eye chart with both eyes.
  • Both eye holes are set to the open position (0).  Do not use the retinoscopy lens (R).  This lens is not necessary and only adds another lens into the light path.
  • The sphere power is set to zero for each eye.
  • The cylinder power is set to zero for each eye.
  • The eye chart is set on a non-accommodative target such as a circle or the big E.
  • The room lights are dimmed.

The examiner (you) is situated in the following manner:

  • Sit as far back from the patient as possible while still being able to reach the dials on the phoropter.  Sitting farther back increases your accuracy.
  • When scoping the patient's right eye,  use the retinoscope with your right eye (and right hand) and sit slightly to the patient's right so that the patient can view the target on the eye chart with her left eye.
  • When scoping the patient's left eye,  use the retinoscope with your left eye (and left hand) and sit slightly to the patient's left so that the patient can view the target on the eye chart with her right eye.  By having the patient view the target on the eye chart,  you are trying to inactivate the patient's accommodation,  which would disrupt the retinoscopic process.

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