Philip Turnbull

Ocular surface microbiome in meibomian gland dysfunction

To investigate the ocular microbiome in meibomian gland dysfunction in Auckland, New Zealand.

Contact Lens Methods for Clinical Myopia Control

Purpose A number of optical methods for slowing myopia progression have been tested and are now available. However, data on real-world use in clinical use is scarce. Here, we present a review of the clinical outcomes for patients attending a specialist myopia control clinic at The University of Auckland Optometry School, NZ. Case Series We report a comparative case series of 110 patients (aged 4–33 years, mean: 12.13 ± 4.58 years, 62% female) who attended the clinic between 2010 and 2014. Fifty-six were prescribed orthokeratology, 32 dual focus soft contact lenses, and 22 received advice only. Initial myopia, vitreous and axial eye length, previous myopia progression, age, number of myopic parents, and gender were not significantly different between orthokeratology and dual focus soft contact lens groups. Mean follow-up time for the orthokeratology and dual focus lens groups was the same (orthokeratology: 1.30 ± 0.88 years; dual focus lens: 1.33 ± 0.80 years (p = 0.989)). There was a significant reduction in the annualized myopia progression in both groups (orthokeratology: −1.17 ± 0.55 to −0.09 ± 017 D/yr, p < 0.001; dual focus soft contact lens: −1.15 ± 0.46 to −0.10 ± 0.23 D/yr, p < 0.001). There was no difference between orthokeratology and dual focus lens treatment efficacy (p = 0.763), nor in axial or vitreous chamber length changes after treatment (p = 0.184). One adverse event was reported over the 4-year period. Conclusions Both orthokeratology and dual focus soft contact lenses are effective strategies for targeting myopia progression in the clinic. We saw no significant difference in the efficacy of the two methods in this regard, and so we believe there are very few barriers for any contact lens practitioner to be actively promoting myopia control treatment to at-risk patients.

Origins of Pupillary Hippus in the Autonomic Nervous System

Purpose The purpose of this study was to determine the relative roles of the sympathetic (SNS) and parasympathetic nervous system (PNS) in pupillary hippus. Methods We used a paired-eye control study design with three cohorts receiving either 1.0% tropicamide (PNS antagonist) in light (TL), 1.0% tropicamide in dark (TD), or 10% phenylephrine (SNS) in light (PL), n = 12 in each. Each subject received one drop to the randomly determined treatment eye, while the other eye served as control. Bilateral measures of pupil size and dynamics were made over 2.6 seconds using an infrared eye-tracker sampling at 500 Hz. Measures were taken at baseline, then every 5 minutes for 40 minutes. Hippus, analyzed in both time and frequency domains, was compared between eyes and cohorts. Results Pupillary hippus with a distinct dominant frequency was present in all measures at baseline (mean: 0.62 Hz, SD: 0.213 Hz), and that frequency did not change in any group (P = 0.971). Hippus magnitude (treatment eye relative to control eye) decreased in the TL (-72.8 ± 4.7%, P < 0.0001) and TD (-71.3 ± 2.6%, P < 0.0001) groups, but did not change in the PL (+5.4 ± 13.7%, P = 0.173) group, despite PL pupils dilating to a proportion similar to TD. Conclusions Pupillary hippus can be extinguished by antagonizing the PNS, whereas agonizing the SNS dilates the pupil without affecting hippus. This suggests that hippus originates from central PNS activity, and not from SNS activity, or oscillations in the balance between PNS and SNS at the pupil.

Comparison of treatment effect across varying severities of meibomian gland dropout

PURPOSE Better understanding of the pathophysiology of meibomian gland dysfunction (MGD) has provided the opportunity to develop treatments which could be tailored for specific presentations of MGD. This study sought to directly compare treatment effectiveness for three current therapies across differing levels of MG dropout. METHODS Subjects (n=81), grouped by infrared meibography dropout proportions, into either no (control), mild, or pronounced MG dropout, were randomised to receive treatment with a latent heat device (n=25), liposomal spray (n=28), or heated warm compress (n=28). A battery of tear film measures was performed, pre- and post-application of treatment, and compared by treatment type and MG severity. RESULTS Symptoms correlated with MG dropout proportions (r=0.618, p<0.001). Following treatment, non-invasive tear breakup time improved (p=0.010), independent of treatment type (p=0.131). The improvement was significant only in the pronounced MGD group (+4.32 ±1.15s, p=0.008), however, following treatment, the mild group was no longer distinct from the control group (p=0.843). Lipid layer grade (LLG) also improved following treatment (p<0.009), but again was not specific to treatment type (p=0.349). All three severity groups showed an improvement in LLG, with 49.3% of participants showing an improvement of at least one grade, and none showing decreased LLG. CONCLUSIONS Increased LLG across all three treatment groups suggests that all methods increase meibum outflow to the tear film, resulting in a thicker lipid layer after treatment. These results suggest that all three treatments are effective in improving tear film quality, independent of MGD severity based either on symptoms or based on gland dropout.

Similar contrast sensitivity functions measured using psychophysics and optokinetic nystagmus

Although the contrast sensitivity function (CSF) is a particularly useful way of characterising functional vision, its measurement relies on observers making reliable perceptual reports. Such procedures can be challenging when testing children. Here we describe a system for measuring the CSF using an automated analysis of optokinetic nystagmus (OKN); an involuntary oscillatory eye movement made in response to drifting stimuli, here spatial-frequency (SF) band-pass noise. Quantifying the strength of OKN in the stimulus direction allows us to estimate contrast sensitivity across a range of SFs. We compared the CSFs of 30 observers with normal vision measured using both OKN and perceptual report. The approaches yield near-identical CSFs (mean R = 0.95) that capture subtle intra-observer variations in visual acuity and contrast sensitivity (both R = 0.84, p < 0.0001). Trial-by-trial analysis reveals high correlation between OKN and perceptual report, a signature of a common neural mechanism for determining stimulus direction. We also observe conditions where OKN and report are significantly decorrelated as a result of a minority of observers experiencing direction-reversals that are not reflected by OKN. We conclude that there are a wide range of stimulus conditions for which OKN can provide a valid alternative means of measuring of the CSF.

Repeatability of Arterial Spin Labeling MRI in Measuring Blood Perfusion in the Human Eye: MRI of Blood Perfusion in the Human Eye

Quantifying blood perfusion in ocular tissues is challenging, partly because the majority of the blood is carried by the choroid, which is difficult to visualize because it is located between the retina and sclera.

Comparing the in vitro effects of MGO™ Manuka honey and tea tree oil on ocular Demodex viability

PURPOSE To compare the in vitro antiparasitic effects of MGO™ Manuka honey and tea tree oil against ocular Demodex. METHODS Fifty-two viable Demodex mites were acquired from the epilated eyelashes of 9 participants with blepharitis and symptomatic dry eye. Viable mites were randomised to one of five treatment groups: cyclodextrin-complexed and uncomplexed Manuka Honey, 100% and 50% tea tree oil, and no treatment. Following treatment application, mite viability was assessed for 240 min, based on limb and body movement and/or the development of a crenated/translucent appearance. Kaplan-Meier survival analysis was then performed. RESULTS The log-rank test demonstrated a significant treatment effect on the survival distribution of Demodex mites (p < 0.001). Bonferroni-corrected post-hoc pairwise analysis showed that all treatments except for uncomplexed honey effected lower survival probabilities than the untreated group (all p < 0.001). Among the four treatments, survival probabilities were lowest with 100% tea tree oil (all p < 0.001), and highest with uncomplexed honey (all p ≤ 0.001). No difference was observed between complexed honey and 50% tea tree oil (p = 0.81). CONCLUSIONS The in vitro efficacy of cyclodextrin-complexed Manuka honey was comparable with 50% tea tree oil, an established treatment for ocular Demodex. The findings support future clinical trials investigating the therapeutic effects of complexed honey in demodectic blepharitis patients.

Ocular effects of virtual reality headset wear in young adults

Virtual Reality (VR) headsets create immersion by displaying images on screens placed very close to the eyes, which are viewed through high powered lenses. Here we investigate whether this viewing arrangement alters the binocular status of the eyes, and whether it is likely to provide a stimulus for myopia development. We compared binocular status after 40-minute trials in indoor and outdoor environments, in both real and virtual worlds. We also measured the change in thickness of the ocular choroid, to assess the likely presence of signals for ocular growth and myopia development. We found that changes in binocular posture at distance and near, gaze stability, amplitude of accommodation and stereopsis were not different after exposure to each of the 4 environments. Thus, we found no evidence that the VR optical arrangement had an adverse effect on the binocular status of the eyes in the short term. Choroidal thickness did not change after either real world trial, but there was a significant thickening (≈10 microns) after each VR trial (p < 0.001). The choroidal thickening which we observed suggest that a VR headset may not be a myopiagenic stimulus, despite the very close viewing distances involved.

Ocular surface microbiome in meibomian gland dysfunction: Microbiome in MGD

To investigate the ocular microbiome in meibomian gland dysfunction in Auckland, New Zealand.