Martin ten Hove

Gaze behavior in audiovisual speech perception: the influence of ocular fixations on the McGurk effect.

We conducted three experiments in order to examine the influence of gaze behavior and fixation on audiovisual speech perception in a task that required subjects to report the speech sound they perceived during the presentation of congruent and incongruent (McGurk) audiovisual stimuli. Experiment 1 showed that the subjects’ natural gaze behavior rarely involved gaze fixations beyond the oral and ocular regions of the talker’s face and that these gaze fixations did not predict the likelihood of perceiving the McGurk effect. Experiments 2 and 3 showed that manipulation of the subjects’ gaze fixations within the talker’s face did not influence audiovisual speech perception substantially and that it was not until the gaze was displaced beyond 10°–20° from the talker’s mouth that the McGurk effect was significantly lessened. Nevertheless, the effect persisted under such eccentric viewing conditions and became negligible only when the subject’s gaze was directed 60° eccentrically. These findings demonstrate that the analysis of high spatial frequency information afforded by direct oral foveation isnot necessary for the successful processing of visual speech information.

Safety and Tolerability of Acetazolamide in the Idiopathic Intracranial Hypertension Treatment Trial.

Objective: To examine the tolerability and adverse events reported in the Idiopathic Intracranial Hypertension Treatment Trial (IIHTT). Methods: Randomized, double-masked, placebo-controlled clinical trial. Trial participants (n = 165) with mild visual loss concurrently receiving low-sodium weight-reduction diet plus the maximally tolerated dosage of acetazolamide (up to 4 g/d) or placebo for 6 months. Main outcomes measures: adverse events (AEs), assessment of clinical and laboratory findings at study visits. Results: Thirty-eight of 86 participants randomized to the acetazolamide group (44.1%) tolerated the maximum allowed dosage of 4 g/d. The average time to achieve maximum study dosage in the acetazolamide group was 13 weeks (median 12 weeks; range 10–24 weeks). A total of 676 AEs (acetazolamide, n = 480; placebo, n = 196) and 9 serious AEs (acetazolamide, n = 6; placebo, n = 3) were reported. Notably, the percentages of participants reporting at least 1 AE in the nervous, gastrointestinal, metabolic, and renal organ systems were significantly higher in the acetazolamide group (P < 0.05). The odds of paresthesia (OR 9.82; 95% CI 3.87–27.82), dysgeusia (OR ∞; 95% CI 3.99–∞), vomiting and diarrhea (OR 4.11; 95% CI 1.04–23.41), nausea (OR 2.99; 95% CI 1.26–7.49) and fatigue (OR 16.48; 95% CI 2.39–702.40) were higher in the acetazolamide group than in the placebo group. Conclusion: Acetazolamide appears to have an acceptable safety profile at dosages up to 4 g/d in the treatment of idiopathic intracranial hypertension. The majority of participants in the Idiopathic Intracranial Hypertension Treatment Trial were able to tolerate acetazolamide above 1 g/d for 6 months.

Vision and driving: Canada.

Supported by the findings of a major review of vision standards for driving in Canada, the Canadian Ophthalmological Societys Committee on Vision Standards for Driving issued a series of recommendations in 2000 to the Canadian Medical Association. Many of these recommendations, including changes in visual acuity and visual field standards and consideration for exceptional cases, have been implemented across Canada. Canadian courts have stated that it is important to provide on-road assessments for visually impaired individuals who wish to continue driving. Most Canadian provinces and territories will allow visually impaired drivers a license if they pass the test. However, these on-road assessments use scarce resources and may be expensive for the driver. Limited licensure is a widespread practice, but whether it effectively protects drivers is not established. Except for Alberta, Quebec, and Nova Scotia, all Canadian provinces and territories have legislated mandatory reporting of visually impaired drivers by vision care providers.

Strabismus surgical subspecialization: a population-based analysis.

IMPORTANCE The growing complexity of medical and surgical care has resulted in increasing subspecialization. To date, data have been lacking regarding the degree to which subspecialization has affected the provision of strabismus surgical services. This gap is important to address given the implications for health care human resources planning and educational programs. OBJECTIVE To investigate the effect of subspecialization on the provision of strabismus surgery services. DESIGN, SETTING, AND PARTICIPANTS Population-based study in Ontario, Canada, which provides universal health care coverage to the provincial population. Participants included all ophthalmologists in Ontario and the provincial population of approximately 12 million persons from January 1, 1994, through December 31, 2011. MAIN OUTCOMES AND MEASURES Surgeon-level rates of strabismus surgery. RESULTS From January 1, 1994, through December 31, 2011, the percentage of ophthalmologists who provided strabismus surgery decreased from 37.7% (156 of 414 surgeons) to 12.5% (54 of 432 surgeons; difference, 25.2%; 95% CI, 19.3%-30.9%; P < .001), a 66.8% decline from the baseline level. Of ophthalmologists who provided strabismus surgery during the same period, the mean number of strabismus procedures per surgeon grew from 16.2 to 55.3 per year, a 241.4% increase (95% CI, 20.4%-461.6%; P < .001). These trends occurred at all career stages. CONCLUSIONS AND RELEVANCE Strabismus surgery has evolved into a subspecialized field of ophthalmology during the past 15 years. These findings may have important implications for health care professionals and health care system leaders, including the need to account for subspecialization in physician human resources decisions to ensure access to quality strabismus surgery across regions. Furthermore, residency education programs and their governing organizations may need to account for strabismus subspecialization when designing curriculum and accreditation requirements.

Optimization of Visual Evoked Potential (VEP) Recording Systems

OBJECTIVE To explore the influence of environmental conditions on pattern visual evoked potential (VEP) recordings. METHODS Fourteen subjects with no known ocular pathology were recruited for the study. In an attempt to optimize the recording conditions, VEP recordings were performed in both the seated and recumbent positions. Comparisons were made between recordings using either LCD or CRT displays and recordings obtained in silence or with quiet background music. Paired recordings (in which only one variable was changed) were analyzed for changes in P100 latency, RMS noise, and variability. RESULTS Baseline RMS noise demonstrated a significant decrease in the variability during the first 50msec accompanied by a 73% decrease in recording time for recumbent position when compared to the seated position (p<0.05). Visual evoked potentials recorded using LCD monitors demonstrated a significant increase in the P100 latency when compared to CRT recordings in the same subjects. The addition of background music did not affect the amount of RMS noise during the first 50msec of the recordings. CONCLUSION This study demonstrates that the use of the recumbent position increases patient comfort and improves the signal to noise ratio. In contrast, the addition of background music to relax the patient did not improve the recording signal. Furthermore, the study illustrates the importance of avoiding low-contrast visual stimulation patterns obtained with LCD as they lead to higher latencies resulting in false positive recordings. These findings are important when establishing or modifying a pattern VEP recording protocol.

Loss of Central Vision and Audiovisual Speech Perception

Communication impairments pose a major threat to an individuals quality of life. However, the impact of visual impairments on communication is not well understood, despite the important role that vision plays in the perception of speech. Here we present 2 experiments examining the impact of discrete central scotomas on speech perception. In the first experiment, 4 patients with central vision loss due to unilateral macular holes identified utterances with conflicting auditory-visual information, while simultaneously having their eye movements recorded. Each eye was tested individually. Three participants showed similar speech perception with both the impaired eye and the unaffected eye. For 1 participant, speech perception was disrupted by the scotoma because the participant did not shift gaze to avoid obscuring the talkers mouth with the scotoma. In the second experiment, 12 undergraduate students with gaze-contingent artificial scotomas (10 visual degrees in diameter) identified sentences in background noise. These larger scotomas disrupted speech perception, but some participants overcame this by adopting a gaze strategy whereby they shifted gaze to prevent obscuring important regions of the face such as the mouth. Participants who did not spontaneously adopt an adaptive gaze strategy did not learn to do so over the course of 5 days; however, participants who began with adaptive gaze strategies became more consistent in their gaze location. These findings confirm that peripheral vision is sufficient for perception of most visual information in speech, and suggest that training in gaze strategy may be worthwhile for individuals with communication deficits due to visual impairments.

Peripapillary choroidal neovascular membrane in a teenage boy: presenting feature of idiopathic intracranial hypertension and resolution with intravitreal bevacizumab.

Peripapillary choroidal neovascular membrane (ppCNVM) is an infrequent finding in patients with idiopathic intracranial hypertension (IIH). In the pediatric subgroup there is only a single previously reported case. We describe the use of intravitreal bevacizumab for ppCNVM in a teenage boy with IIH.

Eye Exercises for Treatment of Idiopathic Cranial Nerve VII Paresis: Pilot Study

BACKGROUND To determine if fine-motor eye exercises can be used for treatment of unilateral, idiopathic cranial nerve VII paresis to improve rate of recovery. METHODS In this prospective, randomized controlled trial, eligible patients were randomized to perform fine-motor eye exercises (n=18) or to do no exercise (n=9) for a period of four weeks. Orbicularis oculi muscle strength was measured in paretic and unaffected eyes at baseline, two weeks and four weeks using an Orbicularis Oculi Pressure Sensor. RESULTS The average initial strength of the paretic orbicularis oculi muscle was 34±10 mm Hg compared to the unaffected muscle which was 103±17 mm Hg at baseline (n=27). By four weeks, patients who performed eye exercises improved more than those who did not (74.4 versus 47.4 mm Hg, p=0.029). While there was some loss to follow-up, 63.8% of patients performing exercises (7/11) achieved functional recovery at four weeks compared to 12.5% (1/8) of those who did not (p=0.059). Steroids and antivirals were found to have independent positive effects on improving functional outcome. CONCLUSIONS Eye exercises have a potential role in the treatment of idiopathic cranial nerve VII paresis and warrant consideration in the management of these patients.

Electroretinograms and Normative Data

Electroretinography (ERG) is an important clinical tool that provides an objective quantitative measure of retinal function. Decreased a and b wave amplitudes and prolonged latencies correlate to reductions in retinal function that may be the result of toxicity, ischemic damage, or retinal dystrophy (Fishman et al. 2001, Ophthalmology monographs). Furthermore, since the different components of the ERG waveform correspond to the different layers of the retina, one is able to attribute changes in the ERG to damage to specific retinal layers. This data can be a useful surrogate for retinal health, for example establishing safety profiles for drugs under clinical development. Since 1989 the International Society for Clinical Electrophysiology of Vision (ISCEV) has provided standards for the recording of ERGs. These documents provide a framework for the clinical electrophyisologist to obtain “standard” ERG recordings (Marmor 1989). The variety of permissible ERG instruments and their individual calibration requirements contributes to significant inter-laboratory variability. This variability is recognized in the ISCEV standards and partly addressed by stating “it is incumbent on the manufactures and users to verify that full-field stimulation meets the requirements of this standard.” Placing the onus for compliance on the manufactures but leaving the clinical electrophyisologist to determine if the recording standards are indeed met. ERG standards have extended beyond the aand b-wave of the full field flash ERG. The pattern ERG (PERG) is the electroretinal response to a pattern reversing stimulus such as bar gratings or checkerboard pattern. The PERG primarily reflects ganglion cell function and since it is viewed on display monitors it largely represents ganglion cell function within the macula. The peak and trough components of the PERG have been formally defined as the N35, P50 and N95 which represent the polarity (Negativity or Positivity) and the mean latency of occurrence. The ISCEV has produced standards for the recording and reporting of the PERG (Holder et al. 2007). While the PERG provides a single waveform which represents the electroretinal response of the entire macular region, the clinical multifocal electroretinogram (mERG) provides information of local retinal function. The mERG is recorded typically displaying the local retinal response of 61 or 103 local regions within the central 45 of the posterior pole. The responses represent localized cone-driven ERGs obtained in the light adapted state. While the waveform morphology of the mERG is similar to the fullfield ERG the electroretinal

Idiopathic intracranial hypertension

More than 93% of people with idiopathic intracranial hypertension (previously called pseudotumour cerebri and benign intracranial hypertension) are obese. The annual incidence of the disease is highest among young obese women, at an estimated 20 per 100 000.[1][1] The median age at onset is 34 years