Article

REFRACTIVE FOCUS

AN ODE TO MY RETINOSCOPE

In these days of high-tech wizardry, we “wow” our patients on a daily basis with 3D section views on optical coherence tomography or with the elevation detail of a corneal topography map. Just recently, though, I’ve been asked almost daily about what I’m doing when I’m performing retinoscopy. What is it about the humble retinoscope that is enthralling my patients? I like to joke with them that I’m “just waving a light around to keep busy,” but then I explain it to them, oftentimes letting them blast me in the eye for a few seconds to appreciate the reflex.

My trusty retinoscope has been by my side for the better part of two decades now; the one time that it needed to be sent for repairs, I couldn’t function as a clinician until I had secured a temporary replacement. In our pursuit of the most fundamental of eyecare skills—refraction—I can’t think of any tool that’s quite as integral to my practicing life as my retinoscope. So, here is an ode to my retinoscope—my buddy “Ret”— and all of the things that it helps me do in just a swift sweep or two, especially in the world of contact lens practice.

Pediatric Refractions

I was recently involved in a panel discussion with colleagues that was filmed for an online course in myopia management. A case was presented in which there was a difference between the child’s subjective refraction and the autorefraction. We were discussing which we would prescribe, and as the conversation evolved, we had to stop the camera to discuss our various refraction techniques.

So, which would I prescribe? Neither! My retinoscopy result is my trusted, objective assessment of a child’s refractive state at both distance and near. Confirming the result subjectively in a trial frame—checking the over-ret and having older children adjust their cylinder axis, if required—means that on some days, especially school holidays, my phoropter doesn’t get any action. I don’t let my pediatric patients near a phoropter unless they’re astigmatic enough to need it and mature enough to provide reliable responses. It’s objective, reliable, and fast to refract children using a retinoscope.

Diagnosing Keratoconus and Other Corneal Irregularities

Within a quick sweep or two, the ret tells whether a patient needs further investigation with topography, which saves me from wasting precious time on a complicated refraction that can be frustrating for both practitioner and patient in these cases. In fact, a recent study investigated the validity and reliability of retinoscopy as a screening tool for keratoconus in comparison to the Pentacam (Oculus) Scheimpflug camera as the gold standard. Retinoscopy was determined to have 98% sensitivity and 80% specificity for detection of even early stages of keratoconus, and there was excellent agreement between two retinoscopists. It was concluded that retinoscopy provides a sensitive and reliable test for keratoconus detection and could be utilized in population screenings (Al-Mahrouqi et al, 2019).

Toric Contact Lens Assessment

After measuring acuity, the ret result will quickly tell whether the lens is sitting in alignment or whether it’s rotating. If there is a spherical or a toric over-retinoscopy result, in which the axis is in alignment (parallel or perpendicular) with the axis of the prescribed lens, it’s a genuine refractive change. If there is a mixed hyperopic astigmatism over-ret result with an oblique axis to the refractive axis, abandon any notion of trying to subjectively over-refract this lens and instead head straight to the slit lamp to assess the degree of rotation. The more that the toric lens is rotated, the greater that the induced oblique astigmatism will be evident on over-ret (Benjamin, 1998). Adding to my list of patients who (almost) never have a subjective refraction, along with kids, are toric contact lens wearers while they are wearing their lenses. If things don’t add up, remove their lenses and assess their full refraction again.

Multifocal Contact Lens Troubleshooting

After checking acuity monocularly (to identify a troublesome eye/lens) and binocularly (to assess the functional outcome), the ret helps to identify the refractive state of the eye-plus-lens. For example, the Bifocal Lenses in Nearsighted Kids (BLINK) study is evaluating distance-center multifocal soft lenses with +1.50D and +2.50D adds for myopia control. In an investigation of fitting the +2.50D add lens to myopic children, the children could achieve best-corrected acuity similar to that with spectacles, but they typically needed an extra –0.50D to –0.75D over-refraction to do so (Schulle et al, 2018). I’ve been observing this exact amount of over-retinoscopy result in my multifocal contact lens-wearing children for some time, but sometimes it’s not quite that simple.

Miranda is a high myopic astigmat who by age 12 had already progressed to OD –5.00 –2.25 x 180 and OS –6.75 –2.75 x 170. She was fit with toric multifocal soft contact lenses with a +2.50D add. Due to stability issues, we subsequently changed to a second lens type with a +2.50D add, and on review, Miranda’s acuity was a few letters better in the second lens type than in the first; but, she was adamant that it didn’t feel as clear. The second lens type was a much-improved fit; her over-retinoscopy result showed –0.50 OD and OS, but with 20/20+ acuity in each eye, I didn’t feel it prudent to over-minus her. Rather, I reduced the add to +2.00D, and this resolved her complaints. My retinoscope allowed me to visualize the optical zones of the lens to confirm centration and, in combination with acuity measures, helped direct management.

An example of “Ret” and me in action.

Orthokeratology Assessment

Aside from the obvious use of the retinoscope to assess treatment level and residual prescription with an orthokeratology (ortho-k) fit, the humble ret can provide an indication of what to expect on topography. Again, this can save time on a difficult subjective refraction in the case of any induced corneal irregularity, such as that due to lens decentration or warping.

Danielle has been wearing ortho-k for three months, with a starting prescription of OD –4.50 and OS –2.50. Her left lens has been an easy fit, but the right lens showed minor temporal decentration owing to a flatter nasal contour on baseline topography relative to the temporal contour. Accordingly, the spherical lens centers where its alignment zone finds the same curvature in the periphery. The first sweep of the horizontal meridian on retinoscopy showed this decentration, with a minor influence on acuity (OD 20/20-, OS 20/20+).

However, when she fixated at 40cm for near retinoscopy, her pupil constricted, and this temporal decentration was far less evident refractively. It also didn’t affect her near acuity. With a baseline topography indicating that this decentration is likely difficult to fix, and Danielle in a near-work-based job, the retinoscopy reflex at near is reassuring that ortho-k does provide a suitable refractive correction without visual compromise.

Complex Contact Lens Fitting

Suppose that I’ve just fit a keratoconus patient with his or her first pair of large-diameter or mini-scleral GP contact lenses. The trial lens kit powers vary dramatically, and I have no clue how close this lens is as far as providing good acuity. Should I swing the phoropter in front of the patient and try huge steps like ±3.00D? Should I walk the patient, significantly over- or under-corrected, to the pre-testing room to use the autorefractor? No, I’m going to let the patient sit right there in the exam chair and quickly and simply work it out myself using my trusty ret. Once I’m in the ballpark, that’s when I’ll introduce the trial frame or the phoropter to work toward achieving best-corrected acuity.

In long-term follow up, the retinoscope reflex can also highlight lens deposits, scratches, surface haze, lens warping, and even the onset of ocular pathology such as cataract.

Do You Feel the Love?

If you don’t feel as strongly about your ret as I do—and perhaps you’ve left this trusty tool languishing since finishing your schooling—I urge you to dig it out, dust it off, and welcome it back into your life.

If you do love your ret as much as I do, throw me the secret “ret club” handshake when you see me at the next conference—it’s a subtle movement with your wrist side-to-side and then up-and-down. CLS

For references, please visit www.clspectrum.com/references and click on document #282.