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In support of routine OCT glaucoma testing

Having read the Soapbox article by Graham Lakkis on glaucoma detection (Insight June 2019), I find myself agreeing with his statistics, but disagreeing with his conclusions.

He argues that optical coherence tomography (OCT) results alone should not be used to diagnose glaucoma, with which I agree. However, he strongly implies that we should not be using OCT for the routine screening of glaucoma among the general population.

Graham states that 50% of glaucoma remains undiagnosed, even among those who have recently had an eye examination. This would suggest that the screening methods currently employed, such as disc examination and intraocular pressure (IOP) measurements, are not picking up a substantial number of glaucoma cases.

I work in an independent practice that does do routine OCT screening on all patients, and I have found it to be an indispensible tool. I have personally seen many patients that appeared normal at first, but subsequently turned out to have ophthalmologically diagnosed glaucoma after OCT scans flagged them as abnormal.

In addition, I have also found that I can significantly reduce the number of follow-up appointments required among patients with suspicious signs, such as large disc cupping and borderline IOPs, if they present with totally normal OCT results.

"After several years of routine OCT use I now find that my over-referral rate is quite small and I am picking up more diagnosed cases of glaucoma"

As is the case with any new test there will always be an increased rate of over-referral and follow-up at first, but with experience we start to learn what is significant, what is not, and how to relate the results with other parameters. Detailed feedback from our ophthalmologist colleagues is invaluable in speeding up this process.

After several years of routine OCT use I now find that my over-referral rate is quite small and I am picking up more diagnosed cases of glaucoma. In some situations I have also identified cases of pre-perimetric glaucoma; cases before field defects are detectable with standard automated perimetry.

Remember that if a patient has a field defect, they have already sustained irreversible damage to their vision.

Borderline results do not necessarily mean that more tests need to be done immediately. If there are no other suspicious factors, and perhaps only a couple of yellow sectors, then it may only be necessary to look for progression. In this case, the scan could just be repeated at the patient’s next routine check.

Further abnormal results with no other suspicious factors can also be repeated sooner rather than later in order to rule out artifacts such as misalignment. This is similar to unreliable visual field tests, which should also be repeated.

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It should also be borne in mind that OCT glaucoma scans might also pick up other undiagnosed conditions, such as neurological lesions, optic nerve lesions and retinal dystrophies. This is another good reason for the routine use of OCT in the clinic.

Even if only one in three cases, as Graham states, are ultimately diagnosed with glaucoma, I feel this is still a good result. The long-term cost-savings derived from the prevention of significant vision loss offsets the over-referral rate to some extent. However, I feel with experience, as well as combining OCT results with other tests and clinical acumen, we can greatly improve on this over-referral rate.

Graham also made this point clear, but I differ in that I do not feel that OCT should be viewed as an ancillary test. Instead, I believe we should consider it essential, in the same way that we currently view ophthalmoscopy or IOP measurements. After all, it is relatively quick, non-invasive and can easily be performed, albeit not interpreted, by ancillary staff.

In terms of cost, the charges to the patient can also be significantly reduced if the burden is spread over a practices’ entire patient base, making the economy of scale another benefit to routine testing.

It is my view that OCT has become a critical tool in the diagnosis of ocular conditions and is should be used as often as possible. It provides practitioners with more information, and ultimately leads to better outcomes for patients.

Name: David Curtis
Qualifications: Dip. App.Sci (Optom.), QIT
Workplace: Curtis Optometrists
Position: Optometrist
Special interests: Retinal pathology and ocular imaging
Location: Greenwood, WA
Years in the profession: 35


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