Keynote speaker Professor Allison McKendrick, Head of Optometry and Vision Science at Melbourne University, opened by applauding the increasing use of OCT in optometry, noting that over 75% of the optometrists in the room had access to OCT. She, however, sounded a cautionary note that this can lead to over-referral, particularly for glaucoma, since most potential glaucoma cases are stable and progress slowly. Overwhelming, public ophthalmology services can lead to those people who do have rapidly progressing glaucoma not being seen in a timely manner, which leads to poorer outcomes later, she said. Adding that those who are treated aggressively for glaucoma that was never likely to progress, must suffer the consequential side-effects of treatment.
Prof McKendrick illustrated her point by showing that some completely normal eyes can show abnormal RNFL on the OCT due to, for example, the optic nerve variation in position above or below the foveal fixation point. As the OCT references the blind spot, about 30% of scans fall outside the reference database. Prof McKendrick cautioned the need to use clinical judgement and not rely solely on the OCT. Other acquisition issues include poor image quality (for example, from dry eyes), poor image centration, significant head tilt, segmentation faults, or unusual anatomical features such as tilted discs. Prof McKendrick emphasised the importance of excellent training for the person taking the images to be able to defray these issues, particularly when comparing previous images.
In the future, we will see a return to more personalised medicine and structure-function mapping, she said. In the meantime, we must rely on previous experience and skill to interpret correctly.
Dr Anjelica Ly continued a similar theme in her discussion of the role of imaging in monitoring AMD and predicting future progression. She asked the rhetorical question, “What tools do I have in my exam room to make my life easier?” I would prefer to rephrase that as “to make my patient’s life easier”, however, the answer lies in prognostic biomarkers. The word of the moment is prognostication, or determining who will lose vision and who won’t, based on four risk factors of drusen appearance and pigment. Again, the take home message was to use as many tools as you have at your disposal to identify progression. Applying evidence-based comparisons to catch late AMD early and imaging can be helpful in tying it all together.
Dr Jack Phu moved the discussion towards comparing visual field measurements. He showed that results between screening devices and different modes are not interchangeable, and that even repeated measurements on the same instrument can give spurious results. It can take many years to collect meaningful results to detect change, he stressed. Static automated perimetry does not give information on functional visual fields, which is what is of interest to patients in their daily lives, particularly among low vision patients. Peripheral and central visual fields need to be assessed separately particularly to predict function.
