The use of the retinoscope/ opthalmoscope can feel intimidating, especially for students. For me, my disliking of retinoscope increased when I was released into the workforce and non of the clinics I worked at used it, even at the hospital!
But today, the retinoscope is my friend and I’m writing this post to hopefully expand the friendship circle.
It’s most common uses:
Retinoscopy is used as a baseline for subjective refraction or even to objectively obtain a refraction from pre-verbal or uncooperative children and people with physical or cognitive disabilities.
If you can expertly use a manual vertomer then Retinoscopy is way easier.
Retinoscopy Made Simple
- Always start WITH motion
It’s okay if you don’t understand the mechanics of how light is refracted depending on the refractive error; but if you do that is a bonus! Anyway, WITH motion is associated with hyperopes or plus lenses. Always add more power!
- If you started with a patient already showing WITH motion, add more plus lenses to neutralize the power.
- If you started with Against motion, use a large minus lens like -10 or -5 and progress towards the positive lenses to obtain a WITH motion and neutralize the power.
2. Check the lens at horizontal and vertical meridians
- If the person only has a spherical power without astigmatism, you will notice the neutralizing lens is the same lens at both meridians.
- However, if the person does have astigmatism, the neutralizing lens at the vertical meridian may be different from the horizontal meridian. Set aside that lens and repeat step 1 until the second meridian is neutralized. Set aside lens number 2.
- The lens with the stronger power (more plus) is the sphere and the difference between the 2 lenses is the astigmatism cylindrical power at the axis of the 2nd lens.
- If the person has against the rule astigmatism, simply rotate the retinoscope beam to match the reflection in the eye. That is your axis!
3. Subtract the working distance from the sphere. Common distance is 67cm= 1.5D.
- Otherwise, the formula is 100/working distance= Sphere Diopters
Here is a Retinoscopy simulator to practice until your heart is content
2. Portable Slitlamp
Well, not exactly but with bright direct transillumination, you can see opacities in the lens, iris, and vitreous screening for opacities and conditions like pigment dispersion syndrome and uveitis.
You can see anterior lesions by using the slit aperture if your model features it.
For funduscopy, depending on your model, your ophthalmoscope can suffice you from other equipment such as a fundus camera.
Use small pupil aperture, again if your model features it to easily see through small undilated pupils.
Again, the slit aperture can show you uneven retinal lessons!
My ophthalmoscope has a red-free filter to allow for better contrast and viewing of vessels and hemorrhages.
Cup to disc ratio can also be easily measured with this filter too. On the other hand, blue light filter allows for better viewing of optic disc drusens, as well as, fluorescence stained lesions.
Also, if you’ve got it, use the polarised light whilst at dark environments. It avoids retinal and corneal reflections while enhancing tissue colours.
A pale optic nerve may indicate optic neuritis or ischemia. Whereas a large cup-to-disc ratio indicates glaucoma. Cotton wool spots or vascular torsions indicate retinopathy and drusens at the macula may show early AMD!
While you are it, why not test the pupils (of course undilated!)
3. Measure Accommodation Lag
Accommodation lag is measured when a patient complains of symptoms relating to eye strain while doing near work.
It is different from measuring the amplitude of Accommodation, accommodation facility, Ac/A ratio, and convergence/diversion binocular fusion ranges. While these are important for the diagnosis of Accommodation related disorders such as Accommodation insufficiency; accommodative lag is helpful for determining the risk of Myopia in individuals.
It is easily measured by performing a normal retinoscopy however with 3 additional factors:
- Patient wears a prescription and is undilated.
- A near target is used for the patient to dynamically accommodate (as opposed to no target for standard retinoscopy)
- Retinoscopy is performed binocularly instead of monocular assessment, at a distance of 30-40cm and no subtraction of working distance is required at the end.
The specialist will first keep adding plus lenses while observing the with movement, until it reverses.
Accommodative lag Result is the lens in between the with and against movement. For example, with motion was seen with plus 1 lens and against was seen in a plus 1.5. The answer is 1.25.
It is easiest to use flippers for this assessment to allow for prompt shaping of lenses and observing of both eyes at the same time.
Lags occur when the stimulus is near and the eye appears to focus farther than the stimulus. Leads occur with far stimuli where the eye appears to focus nearer than the stimulus
Normally, the patient will under-accommodate for a target; +0.50D to +1.00 “lag” of accommodation at near is considered normal.
A higher than normal lag of accommodation means that the person’s focusing ability is under-accommodating and is at high risk of myopia or progression of myopia, and a “lead” of accommodation means that the person is over-focusing.