My binocular indirect ophthalmoscope
Hospital optometrist, Amy Unwin, shares how a piece of equipment that she first encountered at university has become her unlikely go-to for fundus examinations in the hospital setting
Fundus examinations have always been a key role for optometrists, and I’m sure most will use either a direct ophthalmoscope or a Volk lens to carry out fundus examination. While both are excellent pieces of equipment, they do depend upon your patients’ cooperation.
I remember picking up the bio headset at university for the first time and thinking ‘Good job I’ll never need this in practice.’ I thought it was mainly used by ophthalmologists and I was certainly not in a rush to pick it up when I started in the hospital clinic. However, like anything, with practice and patience, I have become a big advocate of the bio headset. I also feel it has been a very reliable piece of equipment while working throughout the COVID-19 pandemic as it gives a good fundus view from arm’s reach.
Like anything, with practice and patience, I have become a big advocate of the bio headset
The benefitsThere are many benefits of the bio headset for an optometrist in day-to-day testing. It provides a clear image and is quick to perform, once you learn the technique, and it is great for those patients who have ‘ants in their pants’ and don’t have steady fixation.
It is suitable for all patients: children, newborns, adults, those who are wheelchair users and those with learning difficulties.
It is portable and could also be great for those carrying out domiciliary work.
It has a longer working distance that allows the examiner to be at arm’s length from the patient, which is more appropriate for testing than other techniques during the pandemic. I have also found patients to be less intimidated by this.
It has a wide field of view. Using a 20D lens, for example, the practitioner can achieve a view equivalent to approximately eight disc diameters. This is great for screening as you can see gross abnormalities in a glance as you can see the optic nerve and macular in the same view.
Furthermore, it allows the optometrist to prioritise the magnification or field of view (FoV). For example, the practitioner can control what they are prioritising by changing the power of the condensing lens. Lenses range from 15–40D. While a 20D lens is a standard lens for general examination, allowing x3 magnification and a FoV of approximately 45 degrees, a 30D lens offers x2 magnification, but a larger FoV of approximately 65 degrees. Therefore, this lens could be preferred if you were prioritising a full retinal examination.
It is important to note that the higher-powered lenses offer less magnification, but a greater FoV. They have to be held closer to the patient’s eye and are smaller in diameter, so might also be preferred by practitioners with smaller hands. Higher powered lenses are also advantageous for those with smaller pupils.
DisadvantagesOf course, with every piece of equipment there are disadvantages to consider. Firstly, it provides low levels of magnification, and high levels of illumination.
Secondly, optometrists should be aware of dilation. Especially when you are learning the technique, examination is much easier on a dilated pupil. If possible, coordinating with cycloplegic refraction is advisable, to save the patient being dilated twice.
The real game changer for me is when I manage to achieve a glimpse of the fundus that I might not have otherwise achieved, as this can really make the difference to a timely diagnosis or a more accurate referral to the ophthalmologist
Don’t judge its appearance
As we know, the binocular indirect ophthalmoscope isn’t the most fashionable piece of equipment in our armoury. Therefore, I find it best to make a joke of this. My paediatric patients respond well to my ‘robot hat,’ and I always have a few illuminated toys or a flashing disco ball to help distract them while carrying out the exam.
The real game changer for me is when I manage to achieve a glimpse of the fundus that I might not have otherwise achieved, as this can really make the difference between a timely diagnosis and a more accurate referral to the ophthalmologist.
I’m not surprised that the binocular indirect ophthalmoscope isn’t a popular piece of equipment as it is unfamiliar for so many of us, even for optometrists in hospitals. However, if you do have a bio headset available, I would encourage you to give it a go (depending on the nature of your examination and the patient). But be mindful that it does take practice.