Our eyes are in continuous motion. Even when we attempt to fix our gaze, we produce so called “fixational eye movements”, which include microsaccades, drift, and ocular microtremor (OMT). Microsaccades, the largest and fastest type of fixational eye movement, shift the retinal image from several dozen to several hundred photoreceptors and have equivalent physical characteristics to saccades, only on a smaller scale (Martinez-Conde, Otero-Millan & Macknik, 2013). OMT occurs simultaneously with drift and is the smallest of the fixational eye movements (∼1 photoreceptor width, >0.5 arcmin), with dominant frequencies ranging from 70 Hz to 103 Hz (Martinez-Conde, Macknik & Hubel, 2004). Due to OMT’s small amplitude and high frequency, the most accurate and stringent way to record it is the piezoelectric transduction method. Thus, OMT studies are far rarer than those focusing on microsaccades or drift. Here we conducted simultaneous recordings of OMT and microsaccades with a piezoelectric device and a commercial infrared video tracking system. We set out to determine whether OMT could help to restore perceptually faded targets during attempted fixation, and we also wondered whether the piezoelectric sensor could affect the characteristics of microsaccades. Our results showed that microsaccades, but not OMT, counteracted perceptual fading. We moreover found that the piezoelectric sensor affected microsaccades in a complex way, and that the oculomotor system adjusted to the stress brought on by the sensor by adjusting the magnitudes of microsaccades.

Ocular microtremor (OMT) is a physiological high-frequency (up to 150 Hz) low-amplitude (25-2500 nm peak-to-peak) involuntary motion of the human eye. Recent studies suggest a number of clinical applications for OMT that include monitoring the depth of anesthesia of a patient in surgery, prediction of outcome in coma, and diagnosis of brain stem death. Clinical OMT investigations to date have used mechanical piezoelectric probes or piezoelectric strain gauges that have many drawbacks which arise from the fact that the probe is in contact with the eye. We describe the design of a compact noncontact sensing device to measure OMT that addresses some of the above drawbacks. We evaluate the system performance using a calibrated piezoelectric vibrator that simulates OMT signals under conditions that can occur in practice, i.e., wet eye conditions. We also test the device at low light levels well within the eye safety range.

Ocular Microtremor (OMT) is a continual, high frequency physiological tremor of the eye present in all subjects even when the eye is apparently at rest. OMT causes a peak to peak displacement of around 150nm-2500nm with a broadband frequency spectrum between 30Hz to 120Hz; with a peak at about 83Hz. OMT carries useful clinical information on depth of consciousness and on some neurological disorders. Nearly all quantitative clinical investigations have been based on OMT measurements using an eye contacting piezoelectric probe which has low clinical acceptability. Laser speckle metrology is a candidate for a high resolution, non-contacting, compact, portable OMT measurement technique. However, tear flow and biospeckle might be expected to interfere with the displacement information carried by the speckle. The paper investigates the properties of the scattered speckle of laser light (λ = 632.8nm) from the eye sclera to assess the feasibility of using speckle techniques to measure OMT such as the speckle correlation. The investigation is carried using a high speed CMOS video camera adequate to capture the high frequency of the tremor. The investigation is supported by studies using an eye movement simulator (a bovine sclera driven by piezoelectric bimorphs). The speckle contrast and the frame to frame spatiotemporal variations are analyzed to determine if the OMT characteristics are detectable within speckle changes induced by the biospeckle or other movements.

Ocular Microtremor (OMT) is a very fine continuous eye movement which has potential in monitoring and identifying a number of clinical conditions. There is a need for improved analysis and processing techniques to extract useful, quantifiable parameters from the OMT signal. A number of papers have shown the clinical significance of looking at the 'bursts' and 'baseling' patterns of the OMT signal. Analysis to date relies on visual inspection alone. This paper introduces an automated approach to burst/baseline identification based on a time-varying filter using the Gabor transform.

ing spectrum of encephalitis with NMDA receptor antibodies in young children. J Child Neurol 2010;25:742-5. 14. Hughes EG, Peng X, Gleichman AJ, Lai M, Zhou L, Tsou R, et al. Clinical Image: Keratitis in reactive arthritisThe patient, a 24-year-old man, presented to the ophthalmology cornea clinic with a 10-day history of pain and severe photophobia in his left eye. Examination revealed bilateral anterior stromal keratitis with multiple subepithelial infiltrates and epithelial breakdown; infiltration and breakdown were more extensive in the left eye, as seen in this slit lamp photograph. There was relatively little conjunctival injection, and the best corrected visual acuity was slightly reduced in the left eye (at 20/25). He had been referred from the ophthalmology emergency department, where he had presented 7 days previously and had been treated empirically with topical chloramphenicol, which produced no improvement. Results of polymerase chain reaction analysis of a conjunctival swab obtained at that time were negative for herpes simplex virus. Two months earlier, he had had culture-proven Salmonella gastroenteritis, which had been followed 10 days later by conjunctivitis and polyarticular arthritis affecting the knees, ankles, and left elbow. At that time, his erythrocyte sedimentation rate was 84 mm/hour and antinuclear antibody, rheumatoid factor, and anti-citrullinated protein antibodies were absent. He was diagnosed as having salmonella-related reactive arthritis (ReA). At presentation to our clinic he was taking oral prednisolone (20 mg/day), as prescribed by his rheumatologist. ReA occurs in Յ4% of patients ϳ1 month after an occurrence of gastroenteritis caused by Shigella, Salmonella, or Campylobacter. While the triad of ReA includes conjunctivitis, numerous other ocular manifestations have been described, including episcleritis, scleritis, and uveitis. Keratitis is a rarely reported manifestation of ReA. In this case, treatment with prednisolone acetate 1% drops led to complete resolution of the ocular symptoms within days, and disappearance of the clinical signs within 3 weeks. After 1 year, the keratitis has not recurred. Niamh E. Collins, MRCSI(Ophth) Royal Victoria Eye and Ear Hospital

Purpose Bleb dysfunction may occur as a late complication following glaucoma filtration surgery. Over-filtering, thinning and cystic blebs can lead to hypotony, leak and corneal dellen. We report our surgical management and outcomes of this specific entity using donor scleral patch grafts. Methods This is a 10-year non-comparative, retrospective interventional case series. Bleb reconstruction involved excision of encysted conjunctiva and sclera to identify the original fistula. A functioning donor scleral patch graft was sited over this with fixed and releasable sutures and the conjunctiva advanced. Intraocular pressure, visual acuity and post-operative issues were assessed. Results A total of 18 eyes of 17 patients with mean age 65 years (standard deviation 13.5) were included. Trabeculectomy was the primary procedure in 72% ( n = 13) and deep sclerectomy in 28% ( n = 5). Bleb leak accounted for 61% ( n = 11), hypotony 33% ( n = 6) and corneal dellen 6% ( n = 1). Mean pre-operative intraocular pressure was 7 mm Hg (standard deviation 4.6) which increased to 18.5 mm Hg (standard deviation 12) at day 1 ( p < 0.001), 11.8 mm Hg (standard deviation 4.6) at 3 months ( p < 0.05), 12.1 mm Hg (standard deviation 4.2) at 1 year ( p < 0.01) which was maintained at 12.1 mm Hg (standard deviation 5.3) at last follow-up ( p < 0.001). Post-operative interventions included bleb needling, re-suturing, suture removal, further glaucoma management, bleb leak and cataract surgery. Visual acuity also improved post-operatively and was maintained. Conclusion Reconstruction of the filtering bleb architecture with donor sclera results in improved intraocular pressure while maintaining visual acuity. Post-operative care is required to support the restored bleb function. Our findings support the use of scleral patch graft as an effective and safe method for the long-term management of hypotony and bleb leak as a late complication of glaucoma filtration surgery.

The TS, when compared with the GAT, underestimates IOP with a tendency for this to increase in the higher range of IOP readings. The TP is poorly correlated with the GAT.

Ocular Microtremor (OMT) is a continual very low amplitude involuntary tremor of the eye which has known potential in the diagnosis of a number of clinical conditions. Rapid involuntary flicks of the eye called microsaccades and slow drifting eye movements contaminate the OMT record. Current methods used to extract OMT from recorded eye movement traces result in some information loss in the OMT pattern. The signal recovery problem in OMT measurement appears to lend itself well to the application of a wavelet denoising technique. In this paper wavelet denoising is employed for the first time for the recovery of OMT.