The Eye Care Advocate

Static Retinoscopy 101

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by

Jason Searle
in

Static retinoscopy is a technique used to objectively measure the refractive error of the eye. This post looks at the basics of retinoscopy and provides a learning activity at the end to test your understanding and knowledge. This article is intended to supplement the information from university lectures and professional training and assumes a minimum of a novice understanding of retinoscopy throughout.

JUMP TO:
How Does it Work?
How is Retinoscopy Performed
What are the Movements?
What do the Movements Mean?
Adaptations
Summary
Skill Centre Activity

What is Retinoscopy?

Retinoscopy, also known as “skiascopy”1, is a procedure that uses light and lenses to determine the refractive error of a patient’s eyes. It’s an essential skill for optometrists and is particularly useful for patients who cannot provide subjective feedback, such as young children1 or those who may be malingering2.

How Does it Work?

During retinoscopy, an optometrist uses a retinoscope3 to shine either a spot or a streak of light into the patient’s eye and observes the red reflex (reflection) from the retina, whilst the patient looks into the distance. By moving the retinoscope, the optometrist can observe the movement of the reflex and use lenses to neutralise it3, that is, they ensure no movement is seen from the red reflex when the streak of light is shone across it. This helps to determine the patient’s refractive error.

An image showing the optics of a neutral reflex of an emmetropic eye using a +1.50 DS working lens for a working distance of 67 cm.

Retinoscopy of an Emmetropic Eye: This diagram shows the retinoscopy process with a +1.50 DS lens at a 67 cm working distance, demonstrating how parallel reflected rays confirm the absence of refractive error in an emmetropic eye.

How is Retinoscopy Performed?

1. Estimate Likely Refractive Error From Case History and Visions4:
From the case history and initial unaided visions, you can work out if the patient has any significant refractive error and, in most cases be able to determine if they are most likely hyperopic or myopic.

2. Explain Procedure4:
Explain to your patient what you are wanting to do with this test. Advise them it is to check for their prescription, explain they will have a trial frame or phoropter with blurry lenses within and use of a light will be required as you perform the test.

Turn off the lights and switch on the duochrome (or other non-accommodative target).

An image of the duochrome

3. Set Up Trial Frame / Phoropter3,4:
Ensure the correct set-up of your frame or phoropter and that the patient is comfortable whilst wearing it. You will require the correct pupillary distance to be dialed in and a short back vertex distance to ensure accurate results.

4. Working Distance3:
Correct for your working distance (the distance from the patient’s cornea to the retinoscope) by adding the equivalent lens to the trial frame or dialing it into your phoropter3. This distance is usually your arm’s length, which allows you to use your arm to keep check of your distance whilst easy changing lenses if needed. It is calculated by finding the reciprocal of the working distance in metres (for example a working distance of 50 cm would be 1 / 0.50 m = +2.00 Dioptres. This corrects the vergence of light to give you neutral when at the end point, of which you would then remove your working distance lenses.

5. Collar Down / Plano Position and Keep on Axis3,4:
Pull the retinoscope collar down into the plano position and turn on the retinoscope. Move yourself so your right eye is on axis with the patient’s right eye. You should block the view of the target with this eye BUT not block the view of the target for their left eye. Providing you are at the same height as the patient and the above is in effect, you should be on axis – this is critical not to induce any astigmatic artifacts into your findings.

6. Ensure Appropriate Fogging of the Left Eye:
Shift your light over to the left eye before correcting the right eye and assess to see if there is an against movement in all meridians (see section below) to check for fogging. If the left eye does not have an against movement in all meridians, add convex/plus/positive lenses in until there is. This will aid in controlling accommodation during the procedure.

7. Refract the Right Eye:
Rotate the streak and sweep across the pupil in all meridians. Ideally check horizontal and vertical meridians first but also the 45 and 135 degree meridians for oblique cylinders. You can then refine your sweeps to find the most precise axis from this. You will want to then add spherical lenses to neutralise (see the section below) the reflex, starting with the slowest with or fastest against movements first (when working in minus cylinder). Once this meridian is corrected for, correct the second meridian.

It is worth noting a slower and duller reflex indicates that the meridian is further away from neutral compared to a faster and brighter reflex.

Correcting the second meridian can either be done with spheres or cylinders (with the cylinders held at the appropriate axis). Many optometrists prefer to correct the second meridian by holding up a sphere until neutrality is found and then substituting it for the corresponding cylinder lens at the end. This helps to avoid introducing astigmatic artifacts into your findings through inaccurate holding of the cylinder during the procedure.

Once at neutral, move your ret closer to the eye than your working distance and see if the reflex shows a with movement, then further away from the eye beyond your working distance and see if an against is observed. If this final check gives the results described, you are at an end point for retinoscopy for the right eye.

A Tip from the Comments (Thank you Marek!) You can use this rocking back and forth during the retinoscopy process to help gauge how much to change the lens power by – instead of just opting to change by small steps.

8. Refract the Left Eye3:
Once retinoscopy on the right eye is complete, move to the left eye. You working distance lens, provided that you have neutralised the right eye, should produce enough fogging for you to control accommodation for when you perform retinoscopy on the left eye. Remember, move yourself to the left hand side, stay on axis and use your left eye to perform retinoscopy on your patient’s left eye3.

9. Remove Working Distance Lenses and Check Acuities:
Once you have neutralised both eyes, remove the working distance lenses and note your results. It is worth measuring the patient’s monocular visions at this point. Ideally, their vision should be better (at worst – the same) as pre-retinoscopy. Knowing these details will help guide the rest of your subjective refraction.

10. Proceed to Subjective Refraction:
Once you have completed your retinoscopy, proceed onto performing a subjective refraction on your patient (outside the scope of this article).

What are the Movements?

As the optometrist moves the light, they will see one of three main results within the reflex. Below are some descriptions with some animations on what these reflexes may look like.

With Movement

An animation of a streak of light passing over a pupil and the streak of light within the pupil moving in the same direction as the main streak. A demonstration of the with movement

With Movement: A “with-movement” is where the direction of the reflex seen through the pupil matches that of the direction the streak is moving in.

Against Movement

Against Movement: An “against-movement” is where the direction of the reflex seen through the pupil moves in the opposite direction to the direction the streak is moving in.

An animation of a streak of light passing over a pupil and the streak of light within the pupil moving in the opposite direction as the main streak. A demonstration of the against movement

Neutral Reflex

An animation of a streak of light passing over a pupil and the pupil just illuminating. A demonstration of the neutralised reflex.

Neutral Reflex: A neutral reflex is one where the reflex in the pupil does not move when the retinoscopy streak passes over it. The pupil will just appear to light up as the streak passes into the pupil and go dark when the streak leaves the pupil.

What the Movements Mean

Seeing the movement in the reflex indicates that there is a refractive error present that needs correcting. This correction is found by placing lenses over the eye that stop the reflexes moving to generate a neutral reflex.

With Movements: A with movement indicates that the meridian requires more plus or less minus to correct it. When performing retinoscopy on an eye with a correcting working distance lens in, this would indicate that the meridian being assessed is hyperopic (and the light would be focusing behind the retina).

WITH MOVEMENTS – ADD MORE PLUS OR REDUCE MINUS

Against Movements: An against movement indicates that the meridian requires more minus or less plus to correct it. When performing retinoscopy on an eye with a correcting working distance lens in, this would indicate that the meridian being assessed is myopic (and the light would be focusing in front of the retina).

AGAINST MOVEMENTS – ADD MORE MINUS OR REDUCE PLUS

Neutral: A neutral reflex is one that shows no movement. This is ultimately the reflex that we are aiming for when performing retinoscopy. If you suspect that you have neutral reflex, to confirm it you can make the reflex demonstrate a with movement when moving closer to the eye and an against when moving away from the eye.

Adaptations

Sometimes the core skill of retinoscopy can run into issues, especially if tackling a patient with pathology. This section will look briefly at different issues that you may encounter and techniques that you can utilise to increase you chances of overcoming them.

An animation of the scissors reflex with a split in the beam making the reflex appear like a pair of scissors.

Scissors Reflex: In some cases, the reflex may produce what looks like a pair of scissors snipping within the reflex (sometimes providing a with and an against movement simultaneously). This is often due to the optical aberration of coma, or in cases of corneal diseases such as keratoconus5. There is an example of the scissors reflex to the left – although it can take several other forms.

To overcome this difficulty you can increase the room lighting to cause the pupil to become smaller and you will then be less likely to be affected by peripheral aberrations4. You can also use larger power lenses to bracket the neutral point4. In some cases, scissor reflexes can be minimised when additional lenses are added throughout retinoscopy.

Large Pupils: These can produce many spherical aberrations. Focus on the central reflex4 and, if necessary, increase the room brightness to encourage mild pupil constriction, allowing for removal of these peripheral aberrations.

Small Pupils: A small pupil will let less light into the eye and as such the reflex will be dimmer. You will need to ensure a wide aperture and aim to use the minimum number of lenses possible (perhaps even removing your working distance lens and accounting for it in the final prescription) to minimise the light loss through lens reflection4.

Media Opacities: Media opacities will obstruct the light entering into the eye and as such the reflex will be dimmer. There will potentially be areas that appear like shadows that affect the reflex – do your best in these situations. You will need to ensure a wide aperture and aim to use the minimum number of lenses possible (perhaps even removing your working distance lens and accounting for it in the final prescription) to minimise the light loss through lens reflection4.

High Ametropia: The higher a patient’s prescription, the further the light will be focused from the retina and thus a duller reflex. Learn to recognise the signs of high ametropia and use cues from previous glasses and the case history. Add a relatively high powered lens (such as a high plus if high hyperopia is suspected) and perform ret with this lens as a baseline4.

Summary

In conclusion, static retinoscopy is a fundamental and precise method used in eye examinations to determine refractive errors. It involves shining a light into the patient’s eye and observing the reflection off the retina. The examiner can then interpret the movement of this reflex to understand the refractive state of the eye. By adding lenses in front of the eye, the reflex can be neutralised, providing an estimate of the patient’s prescription. This technique, while simple, is incredibly effective and forms the basis of many eye examinations. It’s a crucial tool in ensuring optimal eye health and vision correction and thus must be practiced by students and fully qualified optometrists to become proficient.

Skill Activity

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Further Reading

  1. Simsek M, Oral S, Erogul O, Sabaner MC, Simsek C, and Yorukoglu S (2022). Comparison of the results of four different refraction measurement devices in children with retinoscopy. Romanian Journal of Ophthalmology 66(4): 337-343.
    Available online at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9773113/ [Accessed: 30th March 2024].
  2. Naidoo K, and Govender P (2002). Case finding in the clinic: refractive errors. Community Eye Health 15(43): 39-40.
    Available online at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1705884/ [Accessed: 30th March 2024].
  3. White E, Oke I, and Eng K (2023). Retinoscopy. EyeWiki by American Academy of Ophthalmology. Available online at: Information for “Retinoscopy” – EyeWiki (aao.org) [Accessed: 30th March 2024].
  4. Elliott DB (2007). Determination of the refractive correction. In: Elliott DB. Clinical Procedures in Primary Eye Care. Third Edition. Edinburgh: Elseveir pp 97-103.
  5. Santodomingo-Rubido J, Carracedo G, Suzaki A, Villa-Collar C, Vincent SJ, and Wolffsohn J (2022). Keratoconus: an updated review. Contact Lens and Anterior Eye 45(3): 101559.

Comments

2 responses to “Static Retinoscopy 101”

  1. Marek Wojt Avatar
    Marek Wojt

    Hi Jason
    Thanks for this informative summary of basic distance retinoscopy.
    I would make the following comments:
    1. Working distance. Many students are told to use a 66cm string and subtract 1.50 from their result. This is particularly amusing when watching smaller female asian students with shorter wingspans attempt this.
    A working distance of 40cm, and a corresponding 2.00D subtraction not only is ergonomically superior, but as you know, the view from 40cm is MUCH BETTER than at 66cm.
    The part where you advise coming closer and further away to check final endpoint is a good one, but could be expanded to be used during the ret process , Ie rock closer or further way instead of changing the lens by 025 or 050 each time.

    2. I would also note that students being instructed to use the “R” lens in refractor heads is common, and of course just adds two lens surfaces to the view, causing more internal reflections. LEAVE THE R LENS OUT.

    3. There is of course a third option apart from refractor heads and trial frames.
    The one I have found VERY USEFUL in 45 years of practice is to
    a/ Do a ret OVER THE TOP OF CURRENT GLASSES
    and
    b/ Do rets in free space with loose lenses.

    4. There is a particular advantage in retting the LEAST WITH meridian first, leaving one direction neutral and the other (90 degrees from the first) as a POSITIVE movement. When you do this, and assess the remaining with movement more carefully, YOU ARE ABLE TO FIND THE CYL AXIS EXACTLY.
    This is achieved by moving the ret collar up slih=ghtly and narrowing the beam.
    In many (most but not all) cases careful observation will reveal a BRIGHTER REFLEX in the middle of the
    still poise beam. When you rotate the beam, THE BRIGHT CENTRAL REFLEX DOES NOT ROTATE.
    It is indicating the (positive) cal axis.
    SO
    a Neutralise the least with (If sinus, add minus lenses so we achieve this result.
    b Once neutralised, rotate the beam to the remaining with.
    c Narrow beam to find bright central regex giving plus cal axis.
    d Add spherical lenses until second beam is neutral
    COUNT THE STEPS (1,2 3 4)
    Then if in refractor head,
    d rotate minus cal axis so it is at 90 degrees to bright reflex
    e add the number of steps as minus cal in refractor head (4 steps -1.00D)
    f. Subtract working distance (2.00D if ret distance is 40cm)
    You then have the Rx in minus cal form in r head ready for duo chrome and subjective.
    This “Plus cylinder technique” of course also works in trial frames.

    If in free space , just draw the lines and the powers. You will come to the same conclusion with a bit of practice.

    WHEN DOING SUBJECTIVE, DO NOT ask “is this same better or worse” and adding +025
    INSTEAD< ADD +050 and ask "IS that the same or worse?
    Keep adding 050 until it is worse.Then work backwards to get final sphere.

    This technique was taught to me by a pommie Optometrist (OO) who used it to get
    through his list of patients in time to catch his Manchester bus. He moved to Adelaide, South Australia, and influenced many of my cohort when we worked at a large Optometry group practice, Laubman and Pink, in South Australia.

    Hope you find this interesting and useful

    Best regards
    Marek Wojt B. Optom.(Hons), M.Optom
    Adelaide

    Reply
    1. Jason Searle Avatar
      Jason Searle

      Hi Marek,

      Thank you for reading and for your detailed reply. Your added comments and tips will be greatly appreciated by others that have read this post and are aiming to master the art of retinoscopy.

      As you know, there are many methods within retinoscopy that can be utilised to make the task of reaching neutral and of course, many pros and cons to each. The method shared in the post was adapted from the way I was taught (which was based on the David B Elliott method described in his Clinical Procedures in Primary Eye Care) and how I aid students starting to to learn the skill.

      Whilst there is no issues performing the techniques in your comments, I feel only fair to explain why I have provided the guide as in the form that it is in above (and for further information for those wishing to understand other considerations when choosing how to do retinoscopy).

      1) Working distance – I agree, many students do fail to measure their own working distance and as such use the wrong one, leading to an inaccurate ret result. Whilst you are right that the view is better and it is ergonomically easier to perform at a shorter distance, being closer to the eye means maintaining the working distance is much more critical (i.e. small errors of maintaining working distance will be more noticeable on the vergence and subsequent retinoscopy result at shorter working distances) – with students often being poorer at keeping this working distance. I insist students take time to measure their working distance instead of just picking 67 cm / +1.50 DS. I particularly like the point that you made about the rocking back and forth throughout the test to gauge the amount of change required from the reflex and I will certainly add that tip to the post (as well as advise students they can utilise this in their training!)

      2) Working Distance Lenses. This method also has the pros and cons. As you say, leaving the lens in provides an additional reflective surface, making the reflex potentially more difficult to see. The advantage of using a working distance lens does mean that removal of the working distance lens post-retinoscopy gives the final retinoscopy result ready to be utilised in the refraction without having to perform the calculation from retinoscopy. From teaching retinoscopy, I find students are often very focused on what they are trying to do and see, that an added calculation at the end is another thing to worry about and another source of error should they add and not subtract. Similarly, a source of error of using the working distance lens is that the student forgets to take it out…

      3) I completely agree here – it can be very useful to do!

      4) Whilst I agree in plus cyl form the axis is easier to find, convention in UK is to work in minus cyl. In phoropters, you are right, it is easy to alternate between plus and minus cyl forms, but most optometry courses in the UK teach refraction within a trial frame – so to switch from plus to minus cyl can be more difficult – especially for the students only beginning their journey or yet to fully understand transposing to their alternate sphere-cyl form for when they progress. Additionally, I would also factor in the control of accommodation in this case – especially if no working distance lenses are used.

      In summary, my main focus was getting the basics covered in a way they can focus purely on finding a good basepoint for subjective without having to consider the additional nuances of optometry as a whole. However, the points you have raised are very useful for those who have mastered the basics and want to expand on the skill further – and I am very grateful for the comments and expertise that you have shared.

      Best regards,
      Jason Searle BSc(Hons) MCOptom Prof Cert Glauc

      Reply

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