Temporal Edge Research Articles

Retinal thickness and age ‐ optical coherence tomography study

Abstract Purpose To test the hypothesis is retinal thickness of the temporal disc margine ‐ just independent of age. Methods 60 eyes in 60 healthy volunteers were included in this study. Three OCT (STRATUS ‐ Zeiss) scans were performed, aligned vertically and placed at the temporal edge of the optic disc. Retinal Thickness (RT) and retinal nerve fiber layer thickness (RNFLT) were calculated, with variance and correlated with age. Results Both of paramethers tested ‐ RT and RNFLT decrease with age. The mean nerve fibre layer thickness was 112 (SD=21) ‐ in correlation with increasing age, and the mean retinal thickness (MRT) was 237 (SD=24) ‐ not in correlation with age increase . The mean coefficients of variation were 8,3% for RNFLT and 3,9%for total RT. Conclusion OCT testing is of high reproducibility for total retinal thickness and in nerve fibre layer thickness messurements. Both of paramethers decrease with age, but decrease of RNLFT, only, significantly correlates with increasing age. This put optic disc parameters (when a reference plane) in three dimensional tomography, for possible reassesment ‐ adjusting to age.

Longterm findings in peripapillary crescent formation in eyes with mild or moderate myopia

To describe early changes of optic disc deviation and peripapillary crescent formation in eyes with mild or moderate myopia. We carried out a retrospective review of medical records and fundus photographs. We evaluated serial fundus photographs taken in 10 patients with mild or moderate myopia. We observed longterm changes in optic disc areas by creating video files using these photographs and Photoshop and Windows Movie Maker software. The distance between the fovea and the temporal edge of the optic disc was measured in each photograph and any gradual changes in distance between these in the same patient were regarded as representative of optic disc deviation. Correlations between optic disc deviation (0-34.5% disc diameter) and either progression of myopia (- 0.75 D to 6.25 D) or length of follow-up (21-98 months) were statistically examined. On video files, the optic disc appeared to gradually deviate towards the nasal side and the myopic crescent developed gradually in the temporal side of the optic disc in most myopic patients. A significant correlation was found between optic disc deviation and progression of myopia (r2 = 0.61, p < 0.0001), but no correlation was detected between disc deviation and follow-up period (r2 = 0.055, p = 0.33). As optic disc deviation progressed, the peripapillary crescent became larger. The optic disc appears to deviate mostly nasally as myopia progresses and the peripapillary crescent forms as a result of optic disc deviation in eyes with mild or moderate myopia.

Auditory temporal edge detection in human auditory cortex

Auditory objects are detected if they differ acoustically from the ongoing background. In simple cases, the appearance or disappearance of an object involves a transition in power, or frequency content, of the ongoing sound. However, it is more realistic that the background and object possess substantial nonstationary statistics, and the task is then to detect a transition in the pattern of ongoing statistics. How does the system detect and process such transitions? We use magnetoencephalography (MEG) to measure early auditory cortical responses to transitions between constant tones, regularly alternating, and randomly alternating tone‐pip sequences, where the dimension of change is either frequency, loudness, or spatial location. Such transitions embody key characteristics of natural auditory temporal edges. Our data demonstrate that the temporal dynamics and response polarity of the neural temporal‐edge‐detection processes depend in specific ways on the generalized nature of the edge (the context preceding and following the transition) and suggest that distinct neural substrates in core and noncore auditory cortex are recruited depending on the kind of computation (discovery of a violation of regularity, vs the detection of a new regularity) required to extract the edge from the ongoing fluctuating input entering a listener's ears.

Auditory temporal edge detection in human auditory cortex

Auditory objects are detected if they differ acoustically from the ongoing background. In simple cases, the appearance or disappearance of an object involves a transition in power, or frequency content, of the ongoing sound. However, it is more realistic that the background and object possess substantial non-stationary statistics, and the task is then to detect a transition in the pattern of ongoing statistics. How does the system detect and process such transitions? We use magnetoencephalography (MEG) to measure early auditory cortical responses to transitions between constant tones, regularly alternating, and randomly alternating tone-pip sequences. Such transitions embody key characteristics of natural auditory temporal edges. Our data demonstrate that the temporal dynamics and response polarity of the neural temporal-edge-detection processes depend in specific ways on the generalized nature of the edge (the context preceding and following the transition) and suggest that distinct neural substrates in core and non-core auditory cortex are recruited depending on the kind of computation (discovery of a violation of regularity, vs. the detection of a new regularity) required to extract the edge from the ongoing fluctuating input entering a listener's ears.

Brain responses to auditory and visual stimulus offset: Shared representations of temporal edges

Edges are crucial for the formation of coherent objects from sequential sensory inputs within a single modality. Moreover, temporally coincident boundaries of perceptual objects across different sensory modalities facilitate crossmodal integration. Here, we used functional magnetic resonance imaging in order to examine the neural basis of temporal edge detection across modalities. Onsets of sensory inputs are not only related to the detection of an edge but also to the processing of novel sensory inputs. Thus, we used transitions from input to rest (offsets) as convenient stimuli for studying the neural underpinnings of visual and acoustic edge detection per se. We found, besides modality-specific patterns, shared visual and auditory offset-related activity in the superior temporal sulcus and insula of the right hemisphere. Our data suggest that right hemispheric regions known to be involved in multisensory processing are crucial for detection of edges in the temporal domain across both visual and auditory modalities. This operation is likely to facilitate cross-modal object feature binding based on temporal coincidence.

Retinal Detachment in a Patient with Extensive Myelinated Retinal Nerve Fibers

We report extensive myelinated retinal nerve fibers in a 42-year-old patient with retinal detachment. Fundus examination revealed a horseshoe-shaped tear near the temporal edge. Pars plana vitrectomy was performed and firm vitreo-retinal adhesion was noticed in the area of extensive myelinated retinal nerve fibers. Following vitrectomy with silicone oil tamponade, the retina was reattached successfully. In conclusion, retinal detachment may develop in patients with extensive myelinated retinal nerve fibers. Vitrectomy may be performed to treat this condition.

Acute retinal pigment epithelial tear in the untreated fellow eye following repeated bevacizumab (Avastin™) injections

Acute retinal pigment epithelial tear in the untreated fellow eye following repeated bevacizumab (Avastin™) injections

Lateral Head Impacts and Protection of the Temporal Area by Bicycle Safety Helmets

The protective effectiveness of bicycle helmets has been demonstrated in several epidemiologic studies. However, the temple region is only minimally covered by most helmet models. Impact tests were performed on human cadavers to investigate whether current bicycle helmets are capable of preventing direct contact on the temporal area in side impacts. Lateral head impacts, corresponding to a force load of 15,000 N on an nonhelmeted head, were applied on 11 helmeted cadavers by a steel pendulum with a flat impact surface, and the contact between the impactor plate and the temporal and zygomatic area was investigated by means of paint transfer. In eight tests, a common design bicycle helmet was used, whereas in three tests the helmets provided larger temporal coverage (temporal helmet edge <10 mm above Frankfort plane). The skulls were inspected for fractures. In seven of the eight tests with common design bicycle helmets, contact had occurred and in one of these a skull fracture was seen. The helmets with a larger temporal coverage consistently prevented such contact loading. The common designs of commercially available bicycle helmets do not prevent direct contact loading on the temporal and zygomatic arch region and this contact loading is potentially harmful. The present preliminary study strongly questions the effectiveness of these helmets in providing accurate protection of the temporal and zygomatic area.

Comparison of cytologic and histologic evaluations of the conjunctiva in the normal equine eye

To describe the cells observed in conjunctival brush cytology (CBC) from normal horses and compare these findings with conjunctival structural histology so as to understand which cells are recovered from CBC. This study was divided into three parts. (1) Conjunctival brush smears were collected from 20 healthy horses on both eyes and a differential count on 300 cells was carried out on May Grünwald-Giemsa (MGG) smears. (2) A similar protocol was used for whole eyes from five horses obtained rapidly after death from a slaughterhouse. The eyes were then assessed for conjunctival histology. (3) Cytobrush smears were collected from five healthy horses. Smears were examined after MGG or periodic acid Schiff (PAS) staining. The differential cell count showed a majority of deep and intermediate epithelial cells with very few superficial and goblet cells in both eyes. A stratified columnar to cuboidal epithelium was observed on nearly the whole surface of the conjunctiva. A stratified squamous type was observed at the palpebral and bulbar edges. Areas with highest mucus cell indices were found from the nasal to the temporal edge of the equine inferior conjunctiva in the upper palpebral segment near the fornix and in a part of the nasal fornix. In MGG smears no mucus cells were identified; however, they were numerous in PAS smears (22.6% +/- 11) and were mostly cylindrical cells (42.5% +/- 14.4 PAS positive). Cytobrush smears in the healthy horse are characterized by a majority of polyhedral and cylindrical cells and a few squamous cells. The cylindrical cells may be mucous cells and probably originate from the main stratified columnar to cuboidal epithelium.

Auditory grammar: The event construction model and spoken language

Several auditory illusions are accounted for by using the event construction model as presented by Nakajima et al. (2000) in order to explain the gap transfer illusion. In this model, the perceptual system detects and processes onsets and offsets of sounds as if they were independent elements. Temporal edges of sounds and their perceptual attributes are combined to construct auditory events obeying the proximity principle in time and frequency. For example, the onset and offset of a Chinese syllable belonging physically to different tones can be combined if close enough in time and frequency. The listener often hears a syllable with a lexical tone resulting from this illusory connection. Illusory attribution of perceptual features also occurs in nonspeech tones. One demonstration where only an offset of a glide is presented shows the mechanism; a very short illusory tone with no physical counterpart is perceived. Probably, the perceptual system looks for an onset to connect with the offset, but fails and is forced to restore an onset. Our attempts to connect this model to speech perception and pitch perception are presented along with some novel demonstrations. [Work supported by JSPS and 21st Century COE, Kyushu University.]

Redistribution of the neurosensory retina in inferior limited macular translocation: an evaluation using image registration

The present work aims to demonstrate the role of redistribution of the neurosensory retina (RNR)-that is, retinal tissue stretching and compression-in inferior limited macular translocation (LMT), to perform displacement mapping all over the area centralis, and to try and improve displacement evaluation precision. Using piecewise linear image registration (through Matlab) on indocyanine green angiographic frames, we have evaluated the deformation (on both the retinal and choroido-scleral layer) of a pre-operative grid superimposed on the area centralis, plotted displacement vectors all over the area centralis, and calculated a scale ratio between pre- and post-operative frames. The scale ratio tests whether or not the same physical distance is represented by the same distance on these frames. The choroido-scleral layer is not deformed following surgery. The retinal layer shows areas of stretching and compression, demonstrating the RNR. Displacement vectors feature a rotating pattern around the optic disk (except if a macular fold exists) and a positive naso-temporal gradient. The median scale ratio is 3.8% (2.5% to 5.8%). LMT involves RNR accounting for inferior retinal displacement, despite the supposedly limited internal scleral shortening. Our study confirms that the optic disk temporal edge is the displacement axis (except if a macular fold exists). Our method, unaffected by a non-zero scale ratio, provides more precision than previously published.

The Use of Nerve Growth Factor in Surgical Wound Healing of the Cornea

Background: Recent studies have shown how the topical application of nerve growth factor (NGF) has led to the repair of neurotrophic corneal ulcers with recovery of corneal surface sensitivity. The biological effect of NGF, at a corneal level, is mediated by the presence of specific receptors localized on the surfaces of the corneal and conjunctival cells. Objectives: To evaluate the efficacy of NGF to promote corneal wound healing after cataract surgery. Methods: Thirty patients were divided into two groups (groups A and B) and underwent cataract surgery. After surgery patients in group A received 1 drop of NGF solution (10 µg of NGF dissolved in 50 µl of saline solution, 0.9% of sodium chloride) in the conjunctival fornix every 2 h (from 6 a.m. to 12 p.m.) for 2 weeks and then 4 times a day for another week. The patients in group B received 1 drop of hyaluronic acid 0.2% eye drops in the conjunctival fornix every 2 h for 2 weeks and then 4 times a day for another week. With optical coherence tomography (OCT) we evaluated the corneal thickness at the side of the surgical wound, the endothelial cell count and the incision line in the stroma 1, 7 and 21 days after surgery. Results: Before surgery in group A and in group B, the endothelial cell count was 2,607.4 ± 261.0 versus 2,602.0 ± 266.6 (p < 0.991), and the temporal cornea edge thickness was 639.2 ± 24.7 versus 644.4 ± 31.9 µm (p < 0.605), respectively. At 24 h after surgery, the results were: 2,523.2 ± 280.5 versus 2,528.2 ± 235.7 (p < 0.988) and 804.4 ± 29.5 versus 802.6 ± 35.0 µm (p < 0.953). After 7 days the cell count values were: 2,511.4 ± 229.8 versus 2,490.0 ± 230.4 (p < 0.361) and corneal thickness 713.6 ± 16.5 versus 771.4 ± 36.5 µm (p < 0.047). Finally, 21 days after surgery, the number of endothelial cells was 2,540.2 ± 237.3 versus 2,503.4 ± 224.5 (p < 0.382) and corneal thickness 645.2 ± 22.6 versus 704.2 ± 11.8 µm (p < 0.002). In the patients treated with NGF, on day 21, we found with OCT a complete wound healing, and the stromal incision was not visible. Conclusions: This clinical experience shows that the topical administration of NGF is effective in accelerating the healing of surgical corneal wounds.

Temporal Masking in Electric Hearing

Temporal masking can be defined as the detection threshold of a brief signal as a function of the signal delay in a relatively long masker. The temporal masking pattern in normal acoustic hearing reveals temporal edge enhancement in which the signal detection threshold is greater near the masker onset than in the steady-state portion. Both peripheral and central mechanisms appear to underlie temporal edge enhancement, but their relative contributions remain elusive. Cochlear implants bypass cochlear mechanical processing and stimulate the auditory nerve directly, thereby providing a unique opportunity to separate the peripheral mechanisms from the central mechanisms. Here, we systematically measured temporal masking in electric hearing by examining whether a brief signal was harder to detect at the onset than in the steady-state portion of a long masker (the "overshoot" effect). The signal and the masker were presented (1) either to the same electrode or to different electrodes, (2) at the same stimulation or different rates, and (3) in a simultaneous or an interleaved fashion. A consistent pattern of results was observed, depending on the stimulus configuration between the signal and the masker. Simultaneous stimulation at the same rate and with the same electrode produced no difference in sensitivity between the onset and the steady-state conditions, but interleaved stimulation at different rates or with different electrodes produced a significant difference. Unlike acoustic hearing, high masker levels produced an overshoot effect, and low masker levels produced an undershoot effect. Although the present results are consistent with the "on-frequency vs. off-frequency" hypothesis for the overshoot effect, results also suggest a central "same vs. different" mechanism underlying temporal masking. These results have practical implications for improving cochlear implant design.

Visual adjustments to temporal blur

After observers have adapted to an edge that is spatially blurred or sharpened, a focused edge appears too sharp or blurred, respectively. These adjustments to blur may play an important role in calibrating spatial sensitivity. We examined whether similar adjustments influence the perception of temporal edges, by measuring the appearance of a step change in the luminance of a uniform field after adapting to blurred or sharpened transitions. Stimuli were square-wave alternations (at 1 to 8 Hz) filtered by changing the slope of the amplitude spectrum. A two-alternative-forced-choice task was used to adjust the slope until it appeared as a step change, or until it matched the perceived transitions in a reference stimulus. Observers could accurately set the waveform to a square wave, but only at the slower alternation rates. However, these settings were strongly biased by prior adaptation to filtered stimuli, or when the stimuli were viewed within temporally filtered surrounds. Control experiments suggest that the latter induction effects result directly from the temporal blur and are not simply a consequence of brightness induction in the fields. These results suggest that adaptation and induction adjust visual coding so that images are focused not only in space but also in time.

Clinical Neurophysiology: EEG–Video Monitoring

Clinical Neurophysiology: EEG–Video Monitoring

Tomografia de coerência óptica em osteoma de coróide: relato de caso

The authors present a case of choroidal osteoma diagnosed in a 62-year-old male patient. A well-defined and slightly elevated lesion located in the posterior pole of the right eye associated with internal vasculature and choroidal neovascularization at its superior and inferior temporal edge were suspicious of the tumor. Confirmation of diagnosis was obtained with A and B ecography and computed tomography. Optical coherence tomography showed high reflectivity through its thickness as well as elevation of the RPE-choriocapillaris complex at the choroidal neovascularization site. Although the literature and the present case show several different tomographical findings, optical coherence tomography can help establishing the diagnosis of choroidal osteoma.

Multilayered Retinoschisis Associated with Optic Disc Pit

Recently, optical coherence tomography (OCT) analysis has contributed greatly to the detection of posterior retinoschisis associated with optic disc pits. We report an unusual case of optic disc pit maculopathy. A 37-year-old woman with a multilayered structure of posterior retinoschisis associated with a very small, shallow optic disc pit was treated. The patient came to our clinic after a few weeks of decreased vision in her right eye. Fundus examination showed a shallow macular detachment with a tiny, shallow pit at the temporal edge of the optic disc. OCT revealed an unusual multilayered structure of retinoschisis connected to the optic disc. We performed vitrectomy with induction of the posterior hyaloid separation and gas tamponade. After vitrectomy, OCT showed a marked fluid resolution in the retinoschisis, and the patient's vision improved rapidly. The multilayered separation of retinoschisis can be caused by traction of the optic disc with a tiny, shallow pit at the temporal edge of the disc.

Surgical Removal of Peripapillary Choroidal Neovascularization Associated With Age-Related Macular Degeneration

To describe the results of surgical treatment of peripapillary choroidal neovascularization in age-related macular degeneration as an option to both laser photocoagulation and photodynamic therapy. Retrospective review of patients with peripapillary choroidal neovascularization secondary to age-related macular degeneration who were not eligible for or refused laser photocoagulation. Patients without the diagnosis of age-related macular degeneration and those who had extension of their neovascularization subfoveally were excluded from the review. Eleven patients total were identified who met the specified inclusion criteria. The male to female ratio was 4:7, with an age range of 63 to 94 years (mean = 78 years). The mean area of involved retina temporal to the optic disc was 5 clock hours, with the distance of the temporal edge of the lesion from the fovea ranging from 100 to 2,000 microm. The mean duration of follow-up was 23 months, with 27% (3 of 11) experiencing recurrent choroidal neovascularization. The preoperative and postoperative visual acuity ranges were both 20/25 to counting fingers. Sixty-four percent (7 of 11) of patients had stable or improved visual acuity postoperatively, with a mean visual acuity change of 1 line visual improvement. In cases where photodynamic therapy and laser photocoagulation are not indicated, the surgical treatment of peripapillary choroidal neovascularization secondary to age-related macular degeneration may prove beneficial.

Une nouvelle méthode de mesure de la pression intraoculaire

The ocular hypertension (elevation of the intraocular pressure — IOP —) is widespread in the industrialized countries. Its consequences can lead to complete blindness. That is why it is the subject of an attentive surveillance, notably with risky (glaucomatous) patients. Ophthalmologists currently use aplanation tonometers whose utilization induces multiple constraints: (local anaesthesia, additional instrumentations required, …). Our aim was to propose an investigative method both atraumatic and ambulatory. We designed an original device that, putting to profit a physical relation between frequency of mechanical vibration of the ocular globe and the intraocular pressure, combines vibrometry by laser interferometry and spectral analysis of a mechanical impulse transmitted to the eye by a micro hammer located on the temporal edge of the orbital socket. After having scrupulously confirmed that the luminous energy delivered to the eye by the laser source was in agreement with the authorized security norms, we led a survey clinic on 25 patients to test the innocuity and the reliability of this device and to value the reproducibility of measurements. The obtained results are very encouraging: the expressed discomfort is comparable the one felt during analogous sight-testings. Reliability is good (18% of failure in recorded measurements) and the intra individual reproducibility, expressed by the coefficient of interrelationship intraclass, outlines a value qualified of very good ( R > 0.93). These first results encourage us to pursue our works to succeed in establishing an correlation between the measured value (the resonance frequency of the eye-ball) and the supervised one (the intraocular pressure).

Choroidal neovascularization associated with sympathetic ophthalmia: case report

A 7-year-old boy with sympathetic ophthalmia secondary to penetrating ocular trauma developed choroidal neovascularization in the macular region of the sympathizing eye. Posterior segment biomicroscopy disclosed a single, round, small, slightly elevated yellow-white lesion temporal to the fovea, linked to the temporal edge of the optic disc by a fibrotic band. On fluorescein angiography the round lesion showed a gradual hyperfluorescence, with late staining and leakage, and was interpreted as a fibrovascular scar from previous choroidal neovascularization. Despite intense immunosuppressive therapy, the patient's final visual acuity was 20/400. Although rarely associated with sympathetic ophthalmia, choroidal neovascularization and its cicatricial stages can occur and compromise the visual prognosis of an already debilitated eye. The best course of treatment for choroidal neovascularization in these types of cases has not yet been determined.