Purpose.: To evaluate the effect of intense pulsed light (IPL) applied to the periocular area for meibomian gland dysfunction (MGD) in a prospective, double-masked, placebo-controlled, paired-eye study. Methods.: Twenty-eight participants underwent IPL treatment, with homogeneously sequenced light pulses delivered to one eye and placebo treatment to the partner control eye at 1, 15, and 45 days following baseline (BL) evaluation. Lipid layer grade (LLG), noninvasive tear break-up time (NIBUT), tear evaporation rate (TER), tear meniscus height (TMH), and subjective symptom score using visual analogue scales (VAS) were compared with BL and control values at each visit. Results.: Lipid layer grade improved significantly from BL to Day (D) 45 in the treated eye (P < 0.001), but not the control eye (P = 0.714), with 82% of treated eyes improving by at least one LLG. Noninvasive tear break-up time also improved significantly from BL to D45 in the treated (P < 0.001) but not in the control eye (P = 0.056) and was significantly longer than in the treated eye at D45 (14.1 ± 9.8 seconds versus 8.6 ± 8.2 seconds, P < 0.001). The tear evaporation rate was not different in the treated eye compared with the control eye at any visit. Tear meniscus height did not change from BL in either eye (P > 0.05). Visual analog scale symptom scores improved from BL in the treated (P = 0.015), but not the control eye (P = 0.245), with 86% of participants noting reduced symptoms in the treated eye by D45. Conclusions.: Intense pulsed light with multiple sculpted pulses shows therapeutic potential for MGD, improving tear film quality and reducing symptoms of dry eye. (https://www.anzctr.org.au number, ACTRN12614000162617.)

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.

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.

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.