Plus Cylinder Retinoscopy Instructional Video
This is Mark Wilkinson from the University of Iowa Department of Ophthalmology & Visual Sciences. In this presentation I will discuss how to perform plus cylinder retinoscopy.
We will be discussed how to use a retinoscope to determine the refractive error of the eye. We will review the two different types of retinoscopes on the market. We will also be discussing tips for refining your retinoscopy results as well as how to overcome common problems routinely experienced when doing retinoscopy.
Retinoscopy is an objective technique that allows the clinician to determine the refractive error of the eye including the spherical power, cylinder power and cylinder axis. Retinoscopy frees the clinician from dependence on patient responses. Because of the objective nature of retinoscopy, it allows for the determination of the refractive state of patients of all ages, including those who are pre-verbal or non-verbal.
Additionally, the retinoscope is useful for visualization of anterior segment opacities and optical irregularities including cataracts, corneal opacities, irregular astigmatism and keratoconus.
Retinoscopy can be performed in two different ways; static, where accommodation is at rest or paralyzed, or dynamic, where accommodation is active. We will focus on static retinoscopy.
All retinoscopes have two basic settings. A plane mirror setting and a concave mirror setting. For static retinoscopy, we use the plane mirror setting in order to have parallel light rays entering the eye.
There are two types of retinoscopes. The two types are the Copeland design, and all others. For Copeland retinoscopes, the sleeve is up for the plane mirror effect. For all others, the sleeve is down for the plane mirror effect.
The primary disadvantage of the Copeland retinoscope is its non-halogen light source. All other retinoscopes use a halogen light source that makes visualization of the retinoscopic reflex much easier, particularly when doing retinoscopy through smaller pupils and media opacities.
Here you see the power plug at the bottom of the Copeland retinoscope. Simple pull this plug out to turn the Copeland retinoscope on.
You also see the sleeve that is moved up and down to change the retinoscope from the plane mirror setting to the concave mirror setting.
To turn on a halogen retinoscope, simple push down on the green plug and rotate it half a turn.
You also see the sleeve that is moved up and down to change the retinoscope from the plane mirror setting to the concave mirror setting.
When performing retinoscopy, the patient will have both eyes open.
The room lights will be lowered, but not off. Set the sleeve of the retinoscope for the plane mirror effect. This is down for all but the Copeland retinoscope, which is up. Ask the patient to look at a distance target; either a group or line of letters, or a fixation light or dot.
You will use your right eye when streaking the patient's right eye and your left eye when streaking the patient's left eye. This allows the patient to view the target with their fellow eye. Ideally, you will want to keep both of your eyes open when doing retinoscopy. I know this can be difficult when learning to do retinoscopy, particularly when looking with your non-dominant eye. Similar to when using a direct ophthalmoscope, keep practicing and it will get easier to keep both eyes open.
The working distance typically used when performing retinoscopy is 67cm (26"). This creates a working distance lens of 1.50D. For those with shorter arms, a 50cm (20") working distance is used. This creates a 2.00D working distance lens. When learning retinoscopy, it is helpful to tie a string to the head of the scope with knots at 67cm and 50cm to facilitate maintaining the correct working distance.
Here you see a string attached to the head of the retinoscope held 67cm from the phoropter.
To begin retinoscopy, shine the beam of the scope into the patient's pupil in order to see the retinal reflex. The beam is perpendicular to the meridian being scoped. This means that when the beam is oriented vertically and moved side to side, it is moving along the horizontal axis and thus measuring power in the horizontal meridian. When the beam is oriented horizontally and moved up and down, it is moving along the vertical axis and thus measuring power in the vertical meridian.
The goal of retinoscopy is to move the patient's far point to the plane of the retinoscope. The far point of the eye is defined as the point in space where an object must be placed along the optical axis for its image to be focused on the retina when the eye is not accommodating.
When the far point is behind the plane of the retinoscope, plus lenses are added by dialing down on the power wheel. By adding converging, plus power, the far point of the eye is moved in to the plane of the retinoscope.
When the far point is in front of the plane of the retinoscope, between the patient and the retinoscope, minus lenses are added by dialing up on the power wheel. By adding diverging, minus power, the far point of the eye is moved out to the plane of the retinoscope.
Patients with astigmatism have two focal points corresponding to the two different focal powers of the uncorrected astigmatic eye. When performing retinoscopy on a patient with astigmatism, you are adjusting lens powers to put both focal points together at the plane of the retinoscope.
In the case of this image, you see that both focal lines are in front of the retina. This tells us that the patient has compound myopic astigmatism. The patient will need an astigmatic correcting lens to bring the two focal lines together to a single focal point. They will then need a minus lens to move this single focal point back to the plane of the retina.
There are three main characteristics of the retinoscopic reflex that will tell the clinician about their proximity to neutrality: These are the speed of the retinoscopic reflex. The faster the reflex, the closer you are to neutral. The brilliance of the retinoscopic reflex. The brighter, more brilliant the reflex, the closer you are to neutral. And the width of the retinoscopic reflex. The broader the reflex, the closer you are to neutral.
Neutrality is the endpoint of retinoscopy. This occurs when the reflex is neutral; meaning there is no with or against motion. When neutral, the clinician will see a bright, broad, fast reflex.
There are varying opinions concerning the criteria for neutrality. Some feel the first "against motion" coming from "with motion" is neutrality.
Others the last "with motion". Rarely will there be a precise neutral point because the neutral zone is typically about 0.50D. The key for the clinician is to be consistent in establishing neutrality.
To avoid over minusing your patients during retinoscopy, I recommend that you use the last neutral before "against motion" when coming from "with motion".
To double check that you are in the neutral zone; move a few inches closer to the patient with the retinoscope. If neutral, this will result in "with motion". You can then move a few inches further from the patient with the retinoscope. If neutral, this will result in "against motion".
Lets review the specific steps you will use when doing retinoscopy. First, instruct to patient to look at the letters on the screen, or a dot on the screen, and ignore your light. Tell them you may block part of their view, but please tell you if you block the screen completely."
For patients with an unknown refractive error, start with a horizontal streak, streaking the vertical meridian. The reason to do this is two fold. By consistently approaching retinoscopy in the same way, each time you perform this test, you avoid silly mistakes with axis position and spherical and cylindrical powers. Also, more individuals have no astigmatism or with the rule astigmatism than those with against the rule or oblique astigmatism. Because with the rule astigmatism is around axis 90, you will already be set up to correct for with the rule astigmatism after you have neutralize the vertical meridian, with a horizontal streak.
Once you have neutralized the vertical meridian with a horizontally oriented streak, rotate the streak 90 degrees. You now have a vertically oriented streak that you will use to streak the horizontal meridian.
1 of 3 reflexes will be seen. You may have no with or against motion. This means the horizontal meridian is also neutralized and a spherical refractive error is present.
You may have with motion present. In this case, the patient has with the rule astigmatism. This will be neutralized with plus cylinder axis somewhere vertically, based on the axis you have determined by retinoscopy.
Finally, you may have against motion present. This patient has against the rule astigmatism. In this case, minus sphere power is added to neutralize the horizontal meridian. Remember, your streak is now oriented vertically and you are streaking the horizontal meridian. Once you have neutralized the horizontal meridian with a vertically oriented streak, rotate the streak and adjust the cylinder axis 90 degrees to a more horizontal orientation. Now streak the vertical meridian with a horizontal streak, this time adding plus cylinder to neutralize the with motion you have in this orientation.
When adding cylinder power, be sure the cylinder axis is oriented parallel to the retinoscopic streak. To determine the cylinder axis more easily, move the retinoscope sleeve into the concave setting to enhance the reflex.
Remember, the use of the concave mirror setting is only for cylinder axis determination. Once the cylinder axis has been determined, move the sleeve back to the plane mirror setting. Using the concave setting when checking for sphere or cylinder power will result in false neutrality.
Now we will discuss some tips to use when performing retinoscopy. First, if you are having difficulty determining if the motion you see is with or against, this could indicate that a large refractive error is present. Remember, when farther from neutrality you will have a slower, dimmer, narrower reflex. In this situation, moving the retinoscopic streak faster, rather than slower should help you to better determine the motion of the reflex.
You can also move closer to the patient with your retinoscope, until you see the retinoscopic reflex. Once you start to neutralize the reflex, move back to your normal retinoscopic working distance.
Large uncorrected spherical errors will often mask small amounts of astigmatism. With this in mind, you will find that as the spherical error is neutralized, smaller amounts of astigmatism will become more evident.
To account for your working distance, always take out the working distance lens from the phoropter before starting the subject refraction. Remember to dial up, 6 or 8 clicks, depending on your working distance. After taking out the working distance lens, check monocular acuities to see how well you have done.
Don't be confused by "false neutrality", which can occur if you have your retinoscope sleeve in the wrong position. Always make sure the sleeve is in the plane mirror position. Also, when performing retinoscopy, always be aware of your working distance and keep it consistent. Remember, a string tied to the head of the retinoscope is useful until you get a feel for the appropriate distance.
Here are a few techniques to use to assist you with refining the astigmatic correction. First is the break phenomenon. You will see the break phenomenon when you are not streaking on the correct astigmatic correction axis. You will notice that off axis reflexes are less intense and do not line up with the retinoscopic streak. The break phenomenon is more easily seen with higher amounts of astigmatism.
Next is the skew phenomenon. The skew phenomenon also occurs when your retinoscopic reflex is off axis with lower cylinder powers. As in the case of the break phenomenon, the off axis reflex does not line up with the retinoscopic streak.
The straddle cross technique is used to refine the cylinder axis. After you have reached neutrality in both meridians, move a few inches closer to get with motion. Now, streak 45 degrees on either side of the cylinder axis. If the retinoscopic reflex is not symmetrical in both orientations, move the cylinder axis towards the narrower and brighter reflex. Recheck with the straddle cross technique again after rotating the axis. The cylinder axis is found when the 45-degree off axis streaks are the same.
If struggling with reflections, move yourself and/or the phoropter a few degrees to one side or the other. However, remember, doing retinoscopy more than 15 degrees off axis will induce astigmatism.
Some common problems you may encounter when doing retinoscopy include the pupil suddenly constricting. If this happens, the patient is looking at the retinoscope. Redirect the patient's fixation to the distant target.
You may find a changing retinoscopic reflex. In this case, the patient is most likely accommodating or changing accommodation. Redirect the patient's fixation to the distant target.
You may find the brightness of the retinoscopic reflex changing. This happens most often when the patient is looking off to the side. Redirect the patient's fixation to the distance target.
The retinoscopic reflex may show a scissors motion. This often occurs when the retinoscopic streak is not on the cylinder axis. Rotate your retinoscopic streak until the streak and the reflex are aligned. Set your cylinder axis accordingly. Scissors motion can also occur when keratoconus or some other corneal irregularity is present.
If you are faced with smaller pupils and/or cataracts, it will be easier to see the reflex when you move closer. Once you see the reflex, you can move back to your normal retinoscopic working distance. Or, if you have to stay at this closer working distance to complete retinoscopy, simply note your working distance and change your working distance lens accordingly. For exam if you could only perform retinoscopy at a 10" (25cm) working distance, the working distance lens power would be 40/10 or 100/25 = 4.00D. In this case, you would dial up 16 clicks, to remove this closer working distance lens power before starting your subjective refraction.
A dim or indistinct reflex may be due to high refractive error. Try adding high + and/or high – to see if that brightens the reflex.
Now you know the protocol for preforming retinoscopy. The next step is to become proficient with the retinoscope, which will only happen if you use it regularly. Remember, mastering retinoscopy will allow you to objectively determine the refractive error of almost every patient.