Open Eye Condition Research Articles

The Relationship between Self-Regulated Learning (SRL) and Cognitive Function with The Performance of qEEG Examination in First Year Medical Students

Introductions: Medical students are required to lifelong learning. Electroencephalog-raphy is a neuroscience tool that can be used to record brain wave activity related to a person’s cognitive function. Objective: This study was conducted to see the relationship between self-regulated learning and cognitive function with quantitative electroencepha-logram (qEEG) parameters. Methods: This study used an observa-tional analytic approach to assess self-regulated learning and cog-nitive function using the MSLQ and MoCA-INA questionnaires. qEEG recording to see brain wave activity was done when the eyes were open and closed and seen in alpha and beta waves. The sam-ple of this study amounted to 32 respondents who were willing to carry out each research procedure. Results: The study findings reveal a significant correlation between SRL and qEEG parameters. In the open-eye condition, such a correla-tion exists in the frontal and central regions with regard to alpha waves (P = 0.046 and P = 0.047). In contrast, in the closed-eye condition, it exists in the occipital, central, and parietal regions with alpha waves (P = 0.005, P = 0.021, and P = 0.049) and the central region with beta waves (P = 0.030). There is a significant correla-tion between cognitive function and qEEG parameters observed in both open and closed-eye conditions within the frontal region beta waves (P = 0.024, P = 0.044, and P = 0.021). Conclusions: There is a relationship between SRL and cognitive function with alpha and beta wave activity on qEEG recording.

Role of Short Term Open Eye OrthoK Lens Wear in Inducing Myopia Control Changes in Eyes With Moderate Myopia

Purpose: To assess peripheral refraction, corneal, and visual acuity changes after open eye use of orthokeratology (OrthoK) contact lenses. Methodology: OrthoK contact lenses were worn on separate occasions for half an hour and 2 hours in open eye condition. The peripheral refraction (PR) changes were assessed monocularly up to 30° nasally and temporally in the horizontal visual field using the open field autorefractometer. Average corneal power (ACP), central corneal thickness (CCT), and visual acuity (VA) was recorded using corneal topographer, specular microscope, and LogMAR chart respectively. Results: Mean baseline PR at 25° and beyond both nasally and temporally was -0.54 ± 1.68D (mean ± SD) which increased to mean -1.29 ± 1.43D (p < 0.01) post half an hour of lens wear and further increased to mean -1.62 ± 1.53D (p < 0.01) after 2 hours lens wear. The mean baseline ACP was 43.45 ± 1.34D that reduced to mean 43.11 ± 1.37D (p < 0.01) after half an hour of lens wear and a further reduction to mean 42.73 ± 1.34D (p < 0.01) 2 hours post lens wear. Mean CCT changes after half an hour lens wear were not significant but it reduced by mean 14.92 ± 4.68 µm (p < 0.01) 2 hours post lens wear as compared to baseline. The unaided VA improved from mean 0.85 + 0.37 log at baseline to mean 0.49 + 0.35 log (p < 0.01) after half an hour of lens wear and mean 0.39 + 0.35 log (p < 0.01) after 2 hours of OrthoK lens wear. Conclusion: Rapid corneal and peripheral refraction shifts are seen after half an hour of open-eye wear of the OrthoK lens with a gradual rise in impact for 2 hours of lens wear.

Role of Short Term Open Eye Orthok Lens Wear in Inducing Myopia Control Changes in Eyes with Moderate Myopia

Purpose: To assess peripheral refraction, corneal, and visual acuity changes after open eye use of orthokeratology (OrthoK) contact lenses. Methodology: OrthoK contact lenses were worn on separate occasions for half an hour and 2 hours in open eye condition. The peripheral refraction (PR) changes were assessed monocularly up to 30° nasally and temporally in the horizontal visual field using the open field autorefractometer. Average corneal power (ACP), central corneal thickness (CCT), and visual acuity (VA) was recorded using corneal topographer, specular microscope, and LogMAR chart respectively. Results: Mean baseline PR at 25° and beyond both nasally and temporally was -0.54 ± 1.68D (mean ± SD) which increased to mean -1.29 ± 1.43D (p &lt; 0.01) post half an hour of lens wear and further increased to mean -1.62 ± 1.53D (p &lt; 0.01) after 2 hours lens wear. The mean baseline ACP was 43.45 ± 1.34D that reduced to mean 43.11 ± 1.37D (p &lt; 0.01) after half an hour of lens wear and a further reduction to mean 42.73 ± 1.34D (p &lt; 0.01) 2 hours post lens wear. Mean CCT changes after half an hour lens wear were not significant but it reduced by mean 14.92 ± 4.68 µm (p &lt; 0.01) 2 hours post lens wear as compared to baseline. The unaided VA improved from mean 0.85 + 0.37 log at baseline to mean 0.49 + 0.35 log (p &lt; 0.01) after half an hour of lens wear and mean 0.39 + 0.35 log (p &lt; 0.01) after 2 hours of OrthoK lens wear. Conclusion: Rapid corneal and peripheral refraction shifts are seen after half an hour of open-eye wear of the OrthoK lens with a gradual rise in impact for 2 hours of lens wear.

Study of effect of visual stimuli on heart rate variability in middle aged males

Introduction: Changes of light intensity can shift many physiological parameters like heart rate variability (HRV). This study is to assess the effect of visual stimuli on cardiac autonomic activity using Heart Rate Variability in middle aged males. Objectives: To determine the effect of visual stimuli on Heart Rate Variability in middle aged males. Materials and Methods: The effects of visual stimuli on cardiac autonomic activity using Heart Rate Variability (HRV) was studied in 50 healthy middle aged males. Beat to beat R-R intervals were continuously recorded under closed eye condition (CEC) and the open eye condition (OEC). HRV frequency domain parameters like LF nu, HF nu, LF/HF were obtained with the help of RMS polyrite – D version 3.0.11 Results: The values of LF nu, HF nu and LF/HF for all the subjects under both the closed –eye condition (CEC) and open- eye condition (OEC) were obtained. Values of LF nu and LF/HF under CEC appear to be smaller than those OEC. The mean value of HF nu for under CEC was significantly greater ( when compared to OEC. Conclusion: The parasympathetic component of the cardiac autonomic activity increased during the closed eye condition when compared to the open eye condition. Keywords: OEC, CEC, LF/HF, Cardiac activity, AFT.

Classification of Perceived Human Stress using Physiological Signals.

In this paper, we present an experimental study for the classification of perceived human stress using non-invasive physiological signals. These include electroencephalography (EEG), galvanic skin response (GSR), and photoplethysmography (PPG). We conducted experiments consisting of steps including data acquisition, feature extraction, and perceived human stress classification. The physiological data of 28 participants are acquired in an open eye condition for a duration of three minutes. Four different features are extracted in time domain from EEG, GSR and PPG signals and classification is performed using multiple classifiers including support vector machine, the Naive Bayes, and multi-layer perceptron (MLP). The best classification accuracy of 75% is achieved by using MLP classifier. Our experimental results have shown that our proposed scheme outperforms existing perceived stress classification methods, where no stress inducers are used.

Effects of visual occlusion on dynamic postural stability in health young adults

목적: 본 연구는 건강한 젊은 성인을 대상으로 시각정보 입력에 해부학적인 제한을 주었을 때 그들의 동적 균형능력에미치는 영향을 알아보고자 하였다. 방법: 연구대상자의 일반적인 특성(성별, 연령, 신장, 몸무게)을 측정한 후, Space Balance 3D를 이용하여 동적균형능력을 평가하였다. 동적균형능력은 3가지 시각정보 조건(눈뜬조건, 우세눈 감은조건, 비우세눈 감은조건)에서 실시하였다. 연구대상자들은 우세눈검사카드(hold-in-the-card test)를이용하여 우세눈을 검사하였다. 본 연구는 동적균형능력을평가하기 위하여 Space Balance 3D 평가 프로그램 중 진단플러스검사, 사선운동, 자동차피하기게임을 사용하였다. 결과: 진단플러스검사는 왼쪽사선앞(front oblique left)이통계학적으로 유의한 차이가 있었다. 또한 사후 검정결과 왼쪽사선앞은 눈뜬 조건은 우세눈 감은조건과 비우세눈 감은조건과 모두 유의한 차이가 있었으며, 우세눈 감은 조건과 비우세눈 감은 조건도 유의한 차이가 있었다(p<0.05) 사선운동은 시각차단 유형에 따라 효과시간, 운동능력, 비운동능력이유의한 차이가 있었다. 효과시간과 운동능력은 눈뜬 조건이가장 낮고 우세눈 감은조건이 가장 높았다. 그러나 비운동능력은 눈뜬 조건이 가장 높았고 비우세눈 감은조건이 가장 낮았다(p<0.05). 결론: 본 연구의 결과는 우세눈에서 제공하는 시각정보가비우세눈에서 제공하는 시각정보보다 동적균형능력을 유지및 조절하는데 더 크게 작용하는 것으로 판단된다.Visual inputs are an important source of information for postural control, This study examines whether such inputs are absolutely necessary for one eye or both eyes, and whether such visual information are more important to left eye or right eye for postural control. The purpose of this study is investigating the comparison of dominant and non-dominant eye-closed condition on dynamic postural balance in healthy young adults. Six health young adults participated in this study. After measured the hold-in-the-card to check the dominant eye, the sample was then measured dynamic postural balance using the Space Balance 3D system. The measuring programs consisted of a diagnosis plus test, an oblique exercise, and a car avoiding game. To analyze the effect of visual occlusion on dynamic postural balance, this study used the one-way ANOVA. After analyzing, the front of left in the diagnosis and the test was significantly different among in various conditions, such as an open-eye condition, a closed dominant eye condition, and a closed nondominant eye condition. Average time, effect exercise, and non-effect exercise in the oblique exercise were significantly different among in various conditions (p<.05). The results of this study suggest that the visual information of dominant eye is more effectual information to control postural balance than that of non-dominant eye in healthy young adults.

Study of Effect of Visual Stimuli on Heart Rate Varibilityin Young Adult Males

The effects of visual stimuli on cardiac autonomic activity using Heart Rate Variability (HRV)was studied in 50 healthyadult males. Beat tobeat R-R intervals were cotinuously recorded under closed eye condition (CEC) and the open eye condition(OEC). HRV frequency domain parameters like LF nu, HF nu, LF/HF were obtained with the helpof RMS polyrite-D version 3.0.11. There was a significant (p<0.05) decrease in HF nu in OEC when compared to CEC, and a significant(p<0.05)increase in LF nu and LF-HF ratio in OEC when compared to CEC. Indicating increased sympathetic activity and reduced parasympathetic activity in OEC1.

12주간의 수중운동이 노인 골관절염 환자의 동적평형성과 통증요인에 미치는 영향

Abstract This study evaluated the dynamic balance and pain after 12 weeks aquatic exercise in old osteoarthritis patients. The dynamic balances were assessed using 2 different experimental conditions (Open Eye Condition; OEC,Closed Eye Condition; CEC). Twenty-two subjects were assigned one of the two experimental groups: arthritis group(ART, age=65.25±5.9, n=11), control group(CON, age=64.50±7, n=11). All subjects participated in the aquatic exercise program three times a week for 12 weeks. The dynamic balances (OEC (p<.001), CEC (p<.05)) capability were improved significantly in the ART group after 12 week aquatic exercise. Visual Analogue Scale (VAS) was decreased significantly [Factor 10(Soft chair, p< 0.01), 11 (Lying down, p< 0.05), 12(Handicap, p< 0.05), 13 (Workinterference, p< 0.01)] in the ART group. In conclusion, aquatic exercise was effective in improving the overall healthstatus and the capacity of dynamic balances and reducing the degree of pain in osteoarthritis patients.

Treatment of hemispatial neglect in patients with post-hemiparesis: A single-subject experimental design study using a whole-body tilt exercise plus mental practice

To investigate the effect of whole-body tilt exercise for treating hemispatial neglect and to identify the effects of incorporating mental practice into the exercise. We used a single-subject experimental design alternating with multiple baselines. Three stroke patients with hemispatial neglect participated in this study. The severity of hemispatial neglect and balance function were measured during baseline and intervention sessions. The whole-body tilt exercise was performed by using a device that allows the body to tilt 20° from the neutral upright position. Mental practice consisted of 5 min of relaxation, main whole-body tilt imagination, and normalization phases. When the whole-body tilt exercise alone was performed, the average severity score of hemispatial neglect in subjects 1, 2, and 3 decreased by 7.54, 10.02, and 8.24, respectively; their respective average balance function score increased by 35.95%, 28.13%, and 15.33% under the open-eye condition and 34.66%, 20.33%, and 13.77% under the closed-eye condition. For subjects 1, 2, and 3, the respective average hemispatial neglect score decreased by 9.07, 11.35, and 10.13 after the whole-body tilt exercise with mental practice; their average balance function scores increased by 40.15%, 33.38%, and 24.22% under the open-eye condition and by 38.93%, 27.08%, and 11.88% under the closed-eye condition, respectively. These findings suggest that a whole-body tilt exercise alone may be beneficial in enhancing hemispatial neglect symptoms but the addition of mental practice produces a greater positive effect.

Relationship between the medial longitudinal arch and the thoracic and lumbar curvatures with the static and dynamic stability in obese females

Background and Aim: Materials and Methods: Twenty eight obese females (age= 25±8 years old, BMI=37±4) and twenty nine non-obese females (age= 23±4 years old, BMI=23±3) were recruited in this case-control study with the cross-sectional technique. The MLA, spinal curve angles and the static or dynamic balance index of the subjects were measured using the navicular drop, flexible ruler and Biodex balance system tools, respectively. The static balance test was carried out using a modified Clinical Test of Sensory Interaction and Balance (CTSIB) test in both the open and closed eyes while the subjects stood on their dominant legs. The order of the dynamic and static tests was selected randomly. Results: The findings of this study showed that in closed eye condition, most changes happened between the global Stability Index (SI) and BMI; while in open eye condition, most changes occurred between the lateral-medial stability index and BMI (r=0.5). Also during an open eye condition, a moderate correlation was found between the navicular drop and lateral-medial stability index (r=0.05). In closed eyes condition, no significant changes were found between the SI and lumbar lordosis (r=0.0004); while a weak correlation was found between the thoracic curve angle and lateral-medial stability index (r=0.04). Conclusion: The dynamic stability is not only correlated to their BMI, but is highly dependent on their foot curvature types and slightly on their thoracic curve angle. Abdominal obesity always played a significant role in antero-posterior stability index. Lumbar curvature showed a minor effect on static index value. Key words: Dynamic stability, static stability, obesity, thoracic kyphosis, lumbar lordosis. Reviewing the literature reveals a possible correlation between the obesity and the potential foot, spine and stability problems. Investigating the important parameters affecting the balance of obese people and prevention from falling are of high importance to reduce the resulting expenditures. This study aimed to assess the acts and the counter acts between the medial longitudinal arch (MLA) and the thoracic and lumbar curvatures with the static and dynamic stability in obese females.

The relationship between infratentorial lesions, balance deficit and accidental falls in multiple sclerosis

Objective The role of static posturography and magnetic resonance imaging (MRI) in identifying patients at high risk of falls was investigated. Relationships between static posturography measures and MRI metrics were also investigated. Methods A total of 31 ambulatory MS patients (EDSS ranging from 2.0 to 5.0) with a predominant balance disorder were recruited. Each patient underwent a static posturography with a monoaxial platform and a conventional 1.5 T brain MRI scan. Measurements of T1-hypointense and T2-hyperintense lesion volumes (LVs), focusing on lesions selectively located at infratentorial levels, were performed by two operators unaware of clinical data. The self-reported number of falls in the previous 6 months was considered as the main outcome measure. Results Fourteen (45%) patients reported 1 or more falls over the past 6 months. When compared to non-faller patients, they had a higher EDSS score, poorer static standing balance, and greater brainstem and middle cerebellar peduncle (MCP) T2-LVs. A strength correlation between brainstem T2-LV and impaired static standing balance in an open eye condition was also found. In the multivariate analysis, the variables more strictly associated with recurrent falls were greater T2-LV at the MCP (beta: 6.2; p = 0.01) and brainstem (beta: 5.8; p = 0.001) levels, and a wider displacement of the body center of pressure in the closed eye condition (beta: 0.02; p = 0.03). Conclusion Our data suggests that the damage of specific infratentorial areas negatively affect the static standing balance and may predispose MS patients to accidental falls. These findings might contribute in selecting patients requiring a proper rehabilitation intervention program.

A novel, dynamic, in vivo, non-contact method of measuring oxygen depletion rate of the anterior eye

Despite the importance of oxygen measurements, techniques have been limited by their invasive nature and small corneal area of assessment. The aim of this study was to assess a non-contact way of measuring oxygen uptake of the whole anterior eye. The device consisted of a goggle with an oxygen sensitive material on the inner surface. As the output is affected by temperature, a second probe was inserted into the goggle to compensate. The goggle was positioned over the eye on 10 subjects (mean age 30.5±5.0 years, 3:2 male:female) to assess the oxygen depletion of the unrestricted, blinking eye. Measurements were taken over a 3 min period. The volume contained within the goggle and bone structure of individual eyes was measured by water volume displacement and the output corrected to O(2)% reduction/cm(3) over a 30s period. To check the discriminatory ability of the device, measurements were taken in open-eye and closed-eye conditions, along with on the subjects' skin (cheek) for comparisons. The oxygen depletion measure over 30s was on average 3.10±1.51 O(2)%cm(3) during open eye condition, significantly more than during closed eye conditions (1.26±1.52 O(2)%cm(3)). The skin (control) showed a negligible oxygen uptake (0.19±0.33 O(2)%cm(3)). The results demonstrated good repeatability with a mean standard deviation of around 0.4 O(2)%cm(3) (equating to 11%). The technique demonstrated a non-invasive, non-contact method of measuring consumption of oxygen within the goggle (oxygen depletion rate) and showed good within-visit repeatability.

Diffusion and Monod kinetics to determine in vivo human corneal oxygen‐consumption rate during soft contact‐lens wear

The rate of oxygen consumption is an important parameter to assess the physiology of the human cornea. Metabolism of oxygen in the cornea is influenced by contact-lens-induced hypoxia, diseases such as diabetes, surgery, and drug treatment. Therefore, estimation of in vivo corneal oxygen-consumption rate is essential for gauging adequate oxygen supply to the cornea. Phosphorescence quenching of a dye coated on the posterior of a soft contact lens provides a powerful technique to measure tear-film oxygen tension (Harvitt and Bonanno, Invest Ophthalmol Vis Sci 1996;37:1026-1036; Bonanno et al., Invest Ophthalmol Vis Sci 2002;43:371-376). Unfortunately, previous work in establishing oxygen-consumption kinetics from transient postlens tear-film oxygen tensions relies on the simplistic assumption of a constant corneal-consumption rate. A more realistic model of corneal metabolism is needed to obtain reliable oxygen-consumption kinetics. Here, physiologically relevant nonlinear Monod kinetics is adopted for describing the local oxygen-consumption rate, thus avoiding aphysical negative oxygen tensions in the cornea. We incorporate Monod kinetics in an unsteady-state reactive-diffusion model for the cornea contact-lens system to determine tear-film oxygen tension as a function of time when changing from closed-eye to open-eye condition. The model was fit to available experimental data of in vivo human postlens tear-film oxygen tension to determine the corneal oxygen-consumption rate. Reliance on corneal oxygen diffusivity and solubility data obtained from rabbits is no longer requisite. Excellent agreement is obtained between the proposed model and experiment. We calculate the spatial-averaged in vivo human maximum corneal oxygen-consumption rate as Q(c)(max) = 1.05 x 10(-4) mL/(cm(3) s). The calculated Monod constant is K(m) = 2.2 mmHg.

ＳＤＡ法を用いた姿勢制御能の加齢変化の解析

Falling is one of the most common and serious problems because advancing age has been associated with muscle weakness and deterioration of postural control system. The mechanisms contributing to age-related increases in ability of postural control and falls in the elderly remain unclear. The purpose of the stabilogram diffusion analysis(SDA)method was to study change of the mechanism of postural control between young and elderly generation. Any parameters of SDA were compared with several parameters of body sway derived from recordings of the center of pressure(COP)with the aid of a static force platform. The subjects were48healthy young volunteers(age: 18-64yeas, mean±S. D: 33. 6±14. 6years)and41 healthy elderly volunteers(age: 65-87years, mean±S. D: 77.7±4.3years). They quietly stood on a static force plat form with o pen and closing eyes for thirty seconds. The following results were indicated. 1. The elderly group was a significantly than the young group greater in the Diffusion constant Drs and the mean square critical displacement when eyes open and eyes closed. 2. On the elderly group, the correlation between SDA parameters and COP parameters was found to be greater in the closing eye condition than that in the open eye condition. 3. The correlations between diffusion coefficient and the range o f anterior-posterior was greater than the correlations between the diffusion coefficients and the range of medio-lateral. Thus, the muscle of the tibialis anterior and the planter muscles was suggested.

Oxygen Demands with Hybrid Contact Lenses

The purpose of this study was to assess the corneal response, as measured by corneal oxygen uptake, of keratoconic corneas to SoftPerm and SynergEyes hybrid contact lenses at the central cornea, 2.0 and 4.5 mm temporal to the central cornea, and 1 mm temporal to the limbus. Corneal oxygen uptake rates were measured with a Clark-type polarographic electrode on the right eyes of 14 subjects and the left eye of 1 subject, all with keratoconus. Measurements were made at the central cornea, 2.0 and 4.5 mm temporal to the central cornea, and 1 mm temporal to the limbus. They were made for the open eye condition, as well as following 300 s of SoftPerm and SynergEyes hybrid contact lens wear. A one-way analysis of variance (ANOVA) was used to determine the effect of measurement location on oxygen uptake rates under uncovered eye conditions. To determine the difference among oxygen uptake rates relative to those of the uncovered eye at each measurement location for each hybrid lens, a two-way repeated measures ANOVA was used. Multiple comparisons with Tukey-Kramer adjustment were used post hoc to determine which locations were significantly different. For the uncovered keratoconic cornea, there was no significant difference among the oxygen uptake rates associated with the three corneal locations; however, the oxygen uptake rates measured 1 mm temporal to the limbus were significantly higher than those measured at the three corneal locations. Comparison of oxygen uptake rates measured with the SoftPerm and SynergEyes lenses relative to those of the uncovered eye at each location revealed significantly higher rates at the peripheral cornea than at the central cornea. At all locations, the relative oxygen uptake rates obtained with the SynergEyes lenses were lower than those obtained with the SoftPerm lenses. The SynergEyes lens allows significantly more oxygen to reach the cornea during wear than the SoftPerm lens at the central cornea, as well as 2.0 mm and 4.5 mm temporal to the central cornea.

Influence of sound and light on heart rate variability.

The effects of acoustic and visual stimuli and their synergistic effects on heart rate variability including gender differences were investigated. Of particular interest was the influence of visual stimulus on heart rate variability during listening to simple sounds of different characters. Twelve male and 12 female university students were selected as subjects. The subjects listened at rest to 7 different figures of sound at loudness levels averaging 60 dB. Beat-to-beat R-R intervals were continuously recorded under the closed-eye condition (CEC) and the open-eye condition (OEC) prior to, during, and immediately after the exposure to acoustic stimuli. Low frequency (LF) power was defined over 0.04-0.15 Hz and high frequency (HF) power over 0.15-0.40 Hz. Cardiac autonomic function was estimated by plotting LF/HF in standard measure against HF in standard measure and by plotting LF/HF (%) against HF (%), accompanied by a demarcated central area. Values of LF/HF tended to be smaller under CEC than under OEC. Values of HF while listening to a 110 Hz sine wave under CEC were significantly greater than values for 880 Hz and 3520 Hz sine waves, or for 110 Hz or 880 Hz sawtooth waves, under OEC. Under CEC, values of HF for 7 figures of sound were greater in females than in males. The value of HF of sine wave for 110 Hz under CEC and OEC was significantly greater than that for white noise under the OEC. The results suggest that the cardiac parasympathetic nervous activity during auditory excitation increases with elimination of visual stimuli and tends to be greater in females than in males.

Changes in the diurnal pattern of the distribution of gelatinases and associated proteins in normal and pathological tear fluids: evidence that the PMN cell is a major source of MMP activity in tear fluid.

The matrix metalloproteases (MMP) play critical roles in modulating apoptosis, angiogenesis, cell migration, wound healing, tissue remodeling and inflammation in all connective tissues. Two extracellular MMPs, both type IV gelatinases, MMP-2 and MMP-9 (gelatinase A and B), as well as their respective inhibitors TIMP-1, TIMP-2 and TIMP-3 have been detected in the human cornea. MMP-9 is localized in the epithelium while MMP-2 is expressed preferentially by stromal keratocytes, and to a lesser extent, in the epithelium with expression of both enzymes up-regulated during wound healing.1 MMPs, principally pro-MMP-9 and associated complexes, have been detected in human tear fluid in the open eye condition. Active MMP-9 is presumed to be derived principally from the epithelium. Increased levels of enzyme and a shift in the pattern of distribution from proenzyme to the active MMP-9 species, along with the emergence of pro-MMP-2 and active MMP-2, has been observed in tear fluid in a wide range of pathological conditions. These conditions include external ocular infections, corneal wound healing secondary to LASIK, sterile corneal ulcers, dry eye syndrome, active keratoconus, ocular rosacea and sterile corneal melts.2–4 This study was designed to examine the origins and the nature of gelatinolytic species and associated proteins present in normal and pathological tear fluid during open and closed eye phases of the diurnal cycle.

Optimum open eye equalizer design for nonminimum phase channels

This paper contains results on the design of optimum equalizers to eliminate intersymbol interference (ISI) in linear nonminimum phase channels conveying binary signals. The optimization is with respect to an open eye condition with a delay d. For causal stable channels with n/sub c/ nonminimum phase zeros, we argue that this problem requires only the consideration of the n/sub c/-tap FIR modified channel that has all the n/sub c/ nonminimum phase zeros of the original channel. We show that if this modified channel can be equalized to yield an equalized system that is open eye with delay d, then the optimizing equalizer is, in fact, (d-n/sub c/)-tap FIR with all zeros outside the unit circle. We also give a simple necessary and sufficient condition to determine if for a particular d, a given channel can be equalized to achieve an equalized response that is open eye with delay d.

Effects of prism ballasting of rigid contact lenses on human corneal oxygen-uptake rates. Part 1: open eye conditions

Oxygen-uptake rates have not been previously determined along the central-to-inferior vertical hemimeridian of the human cornea, nor have the effects of oxygen deprivation along this meridian. Effects of prism-ballasted rigid lenses on human, open-eye, corneal oxygen dernands were studied using a micropolarographic electrode system. The base-line-unstressed openeye condition showed a significantly higher uptake rate for the inferior cornea with respect to the central cornea. This relationship was not altered under prism-ballasted Boston RXD or Equalens wear,Unexpectedly, under open-eye PMMA wear, the inferior corneal oxygen-uptake rate was lower than its central counterpart. Therefore, rigid prism-ballasted contact lens wear does not seem to compromise the oxygen demand of the inferior cornea under static open-eye conditions, significant for patients wearing astigmatic or bifocal rigid lenses.

Contact lens wear affects corneal pH: implications and new directions for contact lens research

Summary u • Longterm exposure to corneal hypoxia that results from contact leans wear (and presumed stromal acidosis) lowers CHC and induces polymegethism. • Stromal acidosis lowers the rate at which the cornea recovers from an oedematous load (e.g, PRPH). • There is a relationship between the pH level and PRPH, with values of pH ≤7.3 having an increasingly greater effect on CHC. • Stromal pH is directly related to lens DK/L. For the open-eye condition, soft lenses with a Dk/L of 16×10−9 (cm·mlO2)/sec·ml·mmHg) or greater would be necessary to avoid a drop in stromal pH. For the closed-eye condition, the Dk/L must be substantially higher, corresponding to a value of 80×10−9 (cm·mlO2)/(sec·ml·mmHg) or greater. Unfortunately, soft lenses of these transmissibilities are currently not available.