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The dream machine

From tips for novices to the pitfalls of over-reliance on normative data, Aston University lecturer Rebekka Heitmar talks with OT  about how optometrists can harness the potential of optical coherence tomography

01 Mar 2019 by Selina Powell

With any new piece of kit, there can be a tendency to focus on specifications.

The cost, speed and dimensions of a device are weighed up and the business model for introducing the equipment into practice is analysed.

But when it comes to optical coherence tomography (OCT), it can pay to also take a step back and think about how this new technology has the potential to enhance the role that optometrists play in offering clinical care and ultimately improve the lives of patients anxiously waiting for an overdue hospital appointment. 

Or, as Aston University lecturer, Dr Rebekka Heitmar, points out, patients who have fallen through the cracks of the hospital system all together.

“When you are an elderly patient, it is already worrying enough that you have a condition that threatens your eyesight. Having to arrange appointments and travel to the hospital is another concern,” she highlighted.

“Patients lost to follow-up sometimes have the attitude, ‘More bad news? I can’t take it anymore.’ They see it as a doomed thing,” she shared.

“If you can drop by your local optometrist and have a chat, then you can be reassured and there is less time pressure,” she added.

Dr Heitmar sees OCT technology as an important part of the tool kit that has the potential to allow optometrists to monitor certain conditions within the community and ease the strain on the hospital eye service.

“Patients have heard about the technology and their expectations have grown”

Getting to grips with OCT

For practitioners who are new to the technology, Dr Heitmar emphasised the importance of becoming familiar with the device.

Many of the devices have sensors in the head rest and chin rest meaning that it is important that the patient is positioned correctly for scans to be taken.

“At the beginning really take the time before you see the first patient to get continuous good quality images maybe with a colleague or volunteer sitting as a patient,” she said.

Although automatic functions that aim to enhance scan speed are useful, it is also important to know the manual procedures, Dr Heitmar shared.
For example, it can be helpful to switch off the automatic alignment in patients with poor fixation or lens opacity or turn off tracking functions in a patient with nystagmus.

“You don’t always have the perfect patient…You need to know the ins and outs of the equipment,” she emphasised.

What is ‘normal’?

Alongside the mechanics of operating the OCT device, Dr Heitmar highlighted the value of bearing in mind how the technology’s normative database is collected and considering whether it is relevant to the patient sitting in front of the clinician.

She suggested thinking about the age and refractive range of the patients included within the database, as well as their health status and ethnicity.

“If you have someone who is not really comparable to the normative database, it would be wrong to become immediately alarmed with a red or yellow result,” she said.

“I think the right thing to do would be to really look through the whole scan and check for all the things we look for – layer integrity, are there any visible abnormalities? Is there anything to be worried about? Rather than just looking at the numbers,” Dr Heitmar emphasised.

She stressed that rather than relying solely on the normative database, optometrists should treat each individual patient as the best point of comparison. 

Dr Rebekka Heimar

A matter of routine

Dr Heitmar observed that when optometrists first started using OCT, some practitioners would only use the device if they suspected a condition after conducting other clinical evaluations, such as a visual field test or fundus evaluation.

However, Dr Heitmar emphasised the value of taking an OCT scan as a matter of routine to detect change over time.

“Taking scans routinely will not only allow to build up a reference point for each patient to establish if there is a change over time but also enable the clinician to gain more experience on how structural and functional parameters may or may not overlap,” she said.

An optometrist would still use their clinical judgement about when to carry out the scan – a 20-year-old with no family history of ocular pathology might not warrant an OCT at each routine examination, but a patient over 40 could benefit from a routine OCT.

“It is easy then to have something to compare to rather than sitting there and thinking ‘I wonder if it was always like that on the last eye examination?’,” she said.

In practice, rather than showing patients the traffic light output of normative data, Dr Heitmar prefers to show them a line scan.

This is to avoid people becoming overly concerned at patches of red or orange on the scan that might have no clinical significance.

“There is no normative data comparison; it is just a nice picture to show how the retina looks in cross section. I can then explain what it shows without having to say why something lights up red,” she shared.

Increasing uptake

Dr Heitmar highlighted that five years ago, only a limited number of clinically-focused practices had an OCT device.

“Fast forward to today and many more practices have OCT. Patients have heard about the technology and their expectations have grown,” she observed.

Other factors that have influenced the uptake of OCT include its enhanced affordability and Specsavers committing to rolling out the technology.

“There has been pressure on everyone else to follow suit. There is a worry about what will happen if practices don’t have it,” Dr Heitmar said.

The increased use of OCT in optometry practices has added to the already stretched hospital eye service as it has allowed for more abnormalities to be picked up and referred.

“If you see more, you worry more and respond more,” she shared.

“When you are an elderly patient, it is already worrying enough that you have a condition that threatens your eyesight. Having to arrange appointments and travel to the hospital is another concern”

Despite concerns about unnecessary referrals into the hospital eye service as a result of the rise of OCT, Dr Heitmar emphasised that the clinical guidance has not caught up with the evolution of the technology.

“You hear from ophthalmologists that they are happy for optometrists to manage patients in the community and the majority of optometrists would have been happy to do that,” she explained.

“However, if you look at the clinical guidelines and the legal framework that we work within, it specifies in most cases that if we suspect a condition we have to refer,” Dr Heitmar highlighted.

Until all parties involved in the care of patients sit around a table to agree on a change in the guidelines, there will continue to be a debate about over-referring, Dr Heitmar emphasised.

“I have seen the frustration; where optometrists say I would be happy to keep patients on but legally I can’t do that,” Dr Heitmar stressed.

In some areas both parties have worked together closely to counteract over referrals, but this is not the norm.

“I think this is a good development. The problem with these things is that it is so scattered, and it is not the same everywhere,” she said.

Image credit: Nick Linnett

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