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UNSW SOVS Postgraduate students showcase their research

08/05/2015
-By Lewis Williams, PhD

The School of Optometry and Vision Science at the University of NSW held its annual review of postgraduate research student activities over two days beginning at the end of March.

As the opening part of the review process, a seminar-style presentation to the profession was given at the university. Attendees were registered SOVS alumni who were invited via e-mail. CPD points were on offered.

Candidates for the MSc (2) and PhD (8) degrees were involved and a noteworthy feature was the number of candidates from the Centre For Eye Health (4), many of whom also filled staff positions at the centre. Six candidates from SOVs also presented.

From the list of the candidates' supervisors it became obvious that Prof Michael Kalloniatis (CFEH) especially, and Prof Mark Willcox (SOVS), must lead busy lives given their involvement with research supervision of multiple students.

The evening's MC was Dr Isabelle Jallbert, SOVS' deputy head of school and the students were introduced by Dr Blanka Golebiowski, SOVS' postgraduate research director.

 

Early glaucoma detection

The first speaker was Mr Nayuta Yoshioka, optometrist, CFEH, who is investigating the relationship between retinal structure and function in a glaucoma detection context with the aim of reducing the 'apparent' lack of concordance between the two.

 

The discordance is only 'apparent' because post-mortem assessment show that both 'losses' appear to run concurrently suggesting that there are structural changes occurring undetected in advance of measurable functional reductions, e.g. visual field reductions. That discordance is a confounding factor when trying to diagnose the presence of glaucoma, about 50% of which lurks undiagnosed.

One approach being investigated is to alter the size of targets used in perimetry because the current standard (the Goldmann Size III target) has been shown (Khuu & Kallioniatis, 2015) to be larger than the central retina's spatial summation area. Spatial summation is the ability of the retina to add-up (sum) the photic energy it receives.

To understand the concept of 'spatial summation area' (SSA), further background information is required. Firstly, over small (about 10' or 1 mm wide at arm's length) areas, Rico's Law/Rico's Area, an old (1877, Rico [sometimes Ricco] was an Italian astronomer) applies.

Rico's Law states that for light to be detected, the area of the stimulus and the intensity of the incident light are 'interchangeable'. Within that size limit, similar detection levels are found between patches that are twice as bright but half the area, and ones that are half as bright and twice the area (i.e. Area X Intensity = a constant).

Rico's discovery was mentioned by several of the CFEH researchers.

Once the stimulus exceeds a certain critical size, the SSA, the ice-hockey-shaped curve (sloping down to the right, X: log area, Y: log threshold of detection) becomes horizontal and detection is independent of area, i.e. Rico's Law no longer applies.

It is hoped that the use of a smaller target in the assessment of central retinal sensitivity (at the fovea the SSA approximates the conjugate of a single cone cell because there is little or no convergence of receptors to the retina's neural network there) will be a able to detect glaucomatous changes earlier.

Similarly, changes elsewhere in the retina are to be investigated by targets sized according to the local spatial summation areas (larger away from the fovea due to retinal neural convergence).

Rico's belief, probably sound given many findings in the discipline and autopsy findings, is that structural changes precede functional changes clinically and ways of detecting those changes as early as possible will probably go some way towards reducing the toll of glaucoma.

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A second aspect of Mr Nayuta's work is to assess the efficacy of practitioner education focused on glaucoma diagnosis specifically. The outcome was a reduction in false-positives accompanied by little change in the false-negative rate.

Under the title: Size Does Matter, CFEH staff member and optometrist, Mr Jack Phu, also pursued the SSA theme in a glaucoma context.

Again, an early detection theme was relevant, especially in light of data that suggests that up to 25-35% of retinal ganglion cells are lost before functional decreases are detected by common means, the discordance theme again.In addition to the use of multiple stimulus sizes, especially smaller ones, another technique being assessed is directing the test subject to expect test stimuli to appear in specific (examiner-nominated) areas while still maintaining central fixation. The use of multiple targets and varying durations are also being assessed for any contribution they might have to detecting small functional changes sooner.

 

Macular degeneration

Ms Angelica Ly, optometrist, CFEH, is studying imaging methods and the contribution of each to a correct diagnosis of AMD. A defining feature of AMD used in such diagnoses is the presence of sub-retinal pathology, especially sub-retinal fluid.

 

Her PhD is pursuing an absence of uniform testing protocols and a lack of classification schemes targeting AMD specifically. Assessment methods include stereo fundus photography/imaging, fundus auto-fluorescence, near-IR imaging, OCT, etc.

The spectral characteristics of the imaging systems will also play a rôle in diagnosis and at least three wavelengths have been selected for use, 477, 577, and 640nm, either singly or as part of a composite of wavelengths.Currently, the CFEH uses five different wavelengths routinely in various instruments. Trials conducted used bands of wavelengths some 50-100 nm wide. If a successful classification scheme is created its use will be evaluated by experts and non-experts to determine its usefulness more broadly.

 

Uveal melanocytes, your time has come

Mr Ephrem Sitiwin a UNSW science graduate now at the SOVS, is studying uveal melanocytes (pigment cells), an ocular anatomical feature that has to-date, received little attention.

 

Uveal melanocytes are known to reduce light scatter (by virtue of their pigmentation), counter oxidative ocular damage, while at the same time giving adjacent blood vessels mechanical/physical support.

'Transformed' melanocytes are implicated in the development of primary uveal tumours (mostly choroidal), the most common primary ocular tumours in human adults.

Mr Sitiwin's supervisors span the School of Optometry and Vision Science and the Save Sight Institute at Sydney Eye Hospital. The impact of age on melanocytes is another aspect of interest to Mr Sitiwin as are their possible rôles in angiogenesis, immune responses, and other intracellular interactions and interactions with their local environment. The research is using the UNSW Biomedical Imaging Facility including its capacity to use fluorescence-lifetime imaging microscopy (FLIM) for 2-photon excitation microscopy and confocal microscopy. Partial motivation for some of his research is the recent revelation that cutaneous melanocytes can play a rôle in angiogenesis and immunoregulation. The possibility that they may also have similar functions in an ocular context is to be investigated.

More papers in the print version of Insight - out next week

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