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Report

School of optometry and vision science ARVO highlights

06/08/2018By Lewis Williams PhD
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LEWIS WILLIAMS reports on the contributions made by UNSW SOVS researchers at the 2018 ARVO Annual Meeting, which were relayed at a fascinating alumni evening held earlier this year.

The recent School of Optometry and Vision Science (SOVS) educational alumni evening focused on presentations and related research made by staff and graduate students at the 2018 ARVO (Association for Research in Vision and Ophthalmology) Annual Meeting. The meeting, which this year was held in Honolulu in April, is arguably the most important stage on which to present ophthalmic research results.

The first presentation, delivered by Centre for Eye Health (CFEH) optometrist Ms Jessie Huang, examined the impact of professional collaboration on glaucoma care. Huang opened with the observation that the case for a collaborative approach continues to grow, as our ageing population is resulting in an increasing need for eyecare.

Driven partly by the significant waiting times private eyecare usually entails, CFEH has established a partnership with the adjacent Prince of Wales (POW) Hospital’s glaucoma clinic. The collaboration aims to streamline management of glaucoma patients, with a focus on preventing the possibility of unnecessary vision loss due to delayed commencement of glaucoma treatment.

The collaboration is based on RANZCO’s Guidelines for Collaborative Care. It encompasses the initiation of new treatments, as well as ongoing management of existing glaucoma cases. However, cases classified as advanced, acute, or complex are seen by glaucoma specialists at the POW Hospital and their advice forms the foundation of subsequent treatment pathways.

Currently, 11% of referrals made prove to be unsuited to that pathway and the reasons why are the subject of ongoing investigations.

"The collaboration aims to streamline management of glaucoma patients, with a focus on preventing the possibility of unnecessary vision loss due to delayed commencement of glaucoma treatment."

A survey of 100 cases involved in the program identified 49 glaucoma cases and 51 glaucoma suspects. Criteria and assessments used were based on IOP, optic disc appearance, anterior angle, visual fields, central corneal thickness, and a risk assessment (e.g., pseudoexfoliation syndrome – PEX). Foci for assessments were the anterior angle, IOP, optic disc, and visual fields.

Up to 35% of glaucoma patients needed their treatment modified (more, less, none, different treatment/medication) once it had been commenced, according to data collected as part of the collaboration. Under previous referral schemes, IOP was the only criterion applied, however the current referral system represents an update that includes all the criteria detailed above.

Automated image analysis

Dr Barbara Zangerl, a researcher at the CFEH, gave an interesting presentation on the centre’s custom, automated optic nerve head (ONH) image analysis system now in use in glaucoma cases. The system is used to characterise ONHs initially and to monitor any changes chronologically.

Traditionally, such tasks relied on stereo photographic images, sometimes imaged in red-free light, as the latter technique is well suited to disclosing nerve fibre bundle defects. However, despite the ability to perform rapid image superimposition comparisons of sequences via careful photography and alignment of serial images, the process is imperfect and time-consuming.

To try and improve on this technique, a mathematician contractor created a custom, fundus-flicker, false-colour, form-imaging program using the C# (C sharp) programming language, with an interface designed in collaboration with the CFEH users. The program aligns related images using Drance haemorrhages and peripapillary atrophy as reference points.

It uses a subtraction algorithm to identify changes in the ONH, and the on-screen demonstration during Zangerl’s presentation made it quite clear how successful the technology was already. However, despite the systems capability, about 12% of related images still require manual alignment, suggesting a totally automated system is still some way off.

Cohen’s kappa coefficient (a measure of inter-rater agreement) was improved to 0.57 using fundus flicker (from a range of 0.24–0.43), while fundus images from AMD cases also lend themselves to fundus-flicker analysis and comparisons. The present system is claimed to have excellent sensitivity (true positive rate) and moderate specificity (true negative rate), and an ability to detect drusen regression automatically.

While no future plans were announced, it is conceivable that an evolved version of the software has commercial potential, as it would be of use to many ophthalmic practitioners. The general basis of the software means there are also other potential applications both inside and outside the eye.

KEYNOTE SPEAKERS

Jessie Huang

Barbara Zangerl

Edward Lum

Jerome Ozkan

Mei Ying Boon

Barbara Junghans

Pauline Kang

Ocular microbiome

SOVS researcher Dr Jerome Ozkan has been studying the ocular microbiome. According to him, other microbiomes, such as the skin, have relatively stable biomes across most people. Changes can occur over time under the influence of diet, antibiotics, changed environment, etc., but generally by about the ages of 2–3 years, an adult-like state is reached.

However, it is possible to have a state of microbial imbalance or maladaptation on or inside the body, which is known as dysbiosis. A well-known example is gastric ulcers and/or cancers caused by the dominance of Helicobacter pylori in the gut. Other examples are Crohn’s disease, ulcerative colitis, and Clostridium difficile infection following a course of antibiotics. Early antibiotic exposure also has ramifications later in life, such as an increased risk of childhood obesity, a state that affects the diversity of the microbiome.

Ocular dysbiosis can result in dry eye, episcleritis, Thygeson’s superficial punctate keratitis, and chronic follicular conjunctivitis. Although the ocular surface is considered to be sterile or nearly so in most cases, up to 2% of exiting intravitreal injection needles are contaminated.

Confounding the ‘sterile’ claim is our current inability to culture the majority of organisms (only 1–2%) that might be present. That limits identification to actual observations of microorganisms in vivo or ex vivo.

Such observations are laborious and time consuming when colony numbers are small or almost non-existent. It has been suggested that the conjunctival microbiology might be stratified (surface, superficial, or deep) but attempts at swabbing and culturing the various layers has produced different and conflicting results.

It has already been shown that limbal and fornix tissue differs from those of the conjunctival surface. To circumvent the culturing problem, a technique using DNA sequencing is employed instead – by focusing on the 16S ribosomal RNA (rRNA) gene, a bacterial fingerprint of each bacterium can be identified. Unfortunately, Gram negative bacteria are much easier to deal with than Gram positive organisms.

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Using the Illumina MiSeq platform, Ozkan has identified 20 different bacteria in the fornices, 24 in the limbal area, and 43 on the ocular surface itself. The fornix and limbal zones are dominated (75% of identifications) by Pseudomonas spp., whereas the conjunctiva has lower levels (10.4%). Absolute numbers are not derivable using the technique, only the relative contributions of each bacteria – a contribution termed the ‘relative abundance’.

To underline the difficulty of identifying bacteria by culturing, Ozkan was only able to culture six bacteria from one sample, while eventually identifying 180 by mRNA sequencing.

Another technique he employs is FISH (fluorescent in situ hybridisation), using a universal bacteria probe or a Pseudomonas-specific probe. A nonsense probe is used as a control and is expected to be blank when processed.

Ozkan concluded that the fornices and the limbus have similar microbiomes, and that they are different from that of the ocular surface.

Scleral CLS and keratoconus

Optometrist, industrial designer, and researcher from SOVS’ ROK Group (Research in Orthokeratology), Dr Edward Lum, has been researching the effects of scleral and miniscleral CLs on corneal sensitivity, nerve fibre density (NFD), and Langerhans cell density in keratoconic eyes.

Nerves generally are important to ocular health and the cornea’s sensory function is important to the eye’s protection and the maintenance of its tear film. However, rigid CLs of any description depress corneal sensitivity in normal and keratoconic eyes.

The cornea’s neural network is modified by keratoconus and modified further by the combination of keratoconus and CLs, while an increase in Langerhans cells suggest inflammation.

Lum’s eight subjects (16 eyes) were keratoconics who had never worn CLs. They were assessed bilaterally at; baseline, 1, 3, and 6 months after commencing CL wear, however not all subjects made it all the way to 6 months.

Touch sensitivity (Cochet-Bonnet aesthesiometer) was assessed centrally, sensitivity to a pulsed jet of air was measured centrally and at the temporal limbus, and the sub-basal nerve plexus was scanned with a confocal microscope.

While there was a slight tendency to decreased touch sensitivity over time, it failed to reach a statistically significant level.

Likewise, sensitivity to the jet of air was not significantly different centrally or limbally. However, there was a significant difference between the central and limbal sensitivities as a result of CL wear. Langehans cell density differences were also insignificant, even at the 10% confidence level.

Although there was a slight trend towards decreased inflammation in scleral CL wear, it was concluded that a much larger study was required to pursue the matter more deeply.

Suprathreshold VEPS

SOVS senior lecturer Dr Mei Ying Boon delved into the complex topic of ‘VEPs used as an indicator of abnormal cortical processing in non-strabismic amblyopes’. The prevalence of amblyopia was given as 3%, but the responses to treatment are subject to individual variation – while some amblyopes respond positively to treatment, some 25% regress upon cessation of treatment.

Paradoxically, those whose VA at the cessation of treatment was better, are the ones most likely to regress thereafter. Relevant factors affecting outcomes include VA at the time of cessation, previous regression, and tapering of previous treatments. However, stereopsis, stereoacuity, age, race, sex, and age of diagnosis, do not appear to be relevant.

Boon set out to investigate what supplemental information VEP using highly visible stimuli might provide. Amblyopes or amblyopes who completed a course of treatment recently, were compared with normal children (no amblyopia and normal VA), all of whom were aged 4.5 years or older. VEPs were recorded with both eyes open using a sine wave grating with a spatial frequency of 5°, presented at 70% contrast, and with a 100 msec ON-400 msec OFF duty cycle.

A total of 17 bilateral amblyopes, 29 unilateral amblyopes, 6 nearly-recovered amblyopes,4 recovered amblyopes, and 10 controls were assessed. Based on the so-called C3 VEP amplitude, the controls had the highest amplitude, followed closely by the nearly recovered group. All others had significantly lower C3 amplitudes.

Unexpectedly, there was no significant difference between the better and poorer seeing eyes, leading to a conclusion that supports the work of onetime Australian optometrist Professor Robert Hess, which suggests amblyopia is a monocular phenomenon.


Eye-hand co-ordination

SOVS staff member Associate Professor Barbara Junghans presented her research on using a tablet computer-based test, the Lee-Ryan Eye Hand Coordination Test App for eye-hand co-ordination. The test uses a 20-plate sequence that can be set for easy, moderate, or hard challenges.

The test is basically one of shape following, but with the use of all 20 plates it can be time-consuming. A single task-orientation plate precedes all tests and a shorter 6-plate routine is also possible. A pencil, a tablet stylus, or even a finger can be used for the tracing task, which the computer not only delivers, but also records, times, and assesses before transmitting the data via email.

The task can be performed monocularly or binocularly, although with children at least, binocular tasking is faster. While it is possible to use a finger to trace the shapes presented, it is slower. The computer samples the tactile input 10x per second and shape complexity influences the time taken. There is some evidence that, in older individuals, the time to complete the task starts to increase with age.

The applications for the Lee-Ryan (L-R) Test include amblyopia, concussion cases, traumatic and non-traumatic brain injury, developmental anomalies, slow learners, and stroke victims in casualty departments. The L-R Test was conceived by Dr Kiseok (Robin) Lee, designed by Dr Malcolm Ryan, and had input from Junghans, Dr Catherine Suttle and Dr Sieu Khuu, all of whom were associated with UNSW at some stage.

Atropine and choroidal thickness

ROK Group member and myopia researcher, Dr Pauline Kang, undertook a study investigating the effects of atropine on choroidal thickness when the pharmaceutical was instilled at different times of the day. It has already been shown (Huang et al., 2016) that atropine in most concentrations (0.01–1%) is the most effective of all the current anti-myopia treatments.

Surprisingly, 0.01% is almost as effective as higher concentrations, but without most of the side-effects. While the exact mechanism remains unknown, it is generally assumed that there is a biochemical effect in play.

Atropine is known to alter choroidal thickness within an hour of application, but diurnal variations in choroidal thickness are a confounding factor. Generally, when 1% atropine is used, it is applied in the evening before sleep so that its known effects (cycloplegia and mydriasis) go largely unnoticed.

Kang posed the question, “Is there a difference in outcomes when atropine is instilled in the morning (8am) or the evening (8pm)?” The research involved 32 subjects from SOVS, UNSW and SUNY (State University of New York), who were imaged using the Heidelberg Spectralis OCT (horizontal meridian only) at four-hourly intervals (8am–8pm), and at 24 and 96 hours after instillation.

The diurnal variation in choroidal thickness without atropine shows a high around 8am, a low around midday, a more rapid rise to 4pm and a slower rise thereafter to the 8pm determination. Under the influence of atropine, the thickness peaked before midday (opposite of diurnal behaviour) and then slowly thinned in the PM to finish at or below the baseline thickness, i.e., thickest in the morning and thinnest in the evening.

The latter suggests that atropine administered first thing in the morning may have a greater anti-myopia effect that the same dose administered just before sleep. In the case of progressive myopes, Kang concluded that further study was required.

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