Sharon Yeo

Computer aided diagnosis of atrial arrhythmia using dimensionality reduction methods on transform domain representation

Abstract Electrocardiogram (ECG) is a P-QRS-T wave, representing the depolarization and repolarization mechanism of the heart. Among different cardiac abnormalities, the atrial fibrillation (AF) and atrial flutter (AFL) are frequently encountered medical emergencies with life threatening complications. The clinical features of ECG, the amplitude and intervals of different peaks depict the functioning of the heart. The changes in the morphological features during various pathological conditions help the physician to diagnose the abnormality. These changes, however, are very subtle and difficult to correlate with the abnormalities and demand a lot of clinical acumen. Hence a computer aided diagnosis (CAD) tool can help physicians significantly. In this paper, a general methodology is presented for automatic detection of the normal, AF and AFL beats of ECG. Four different methods are investigated for feature extraction: (1) the principal components (PCs) of discrete wavelet transform (DWT) coefficients, (2) the independent components (ICs) of DWT coefficients, (3) the PCs of discrete cosine transform (DCT) coefficients, and (4) the ICs of DCT coefficients. Three different classification techniques are explored: (1) K -nearest neighbor ( K NN), (2) decision tree (DT), and (3) artificial neural network (ANN). The methodology is tested using data from MIT BIH arrhythmia and atrial fibrillation databases. DCT coupled with ICA and K NN yielded the highest average sensitivity of 99.61%, average specificity of 100%, and classification accuracy of 99.45% using ten fold cross validation. Thus, the proposed automated diagnosis system provides high reliability to be used by clinicians. The method can be extended for detection of other abnormalities of heart and to other physiological signals.

EPILEPTIC EEG CLASSIFICATION USING NONLINEAR PARAMETERS ON DIFFERENT FREQUENCY BANDS

Epilepsy is a chronic neurological disorder with considerable incidence and affects the population everywhere in the world. It occurs due to recurrent unprovoked seizures which can be noninvasively diagnosed using electroencephalograms (EEGs) which are the neuronal electrical activity recorded on the scalp. The EEG signal is highly random, nonlinear, nonstationary and non-Gaussian in nature. The nonlinear features characterize the EEG more accurately than linear models. EEG comprsises of different activities like delta, theta, lower alpha, upper alpha, lower beta, upper beta and lower gamma which are correlated to the brain anatomy and its function. In the current study, the nonlinear features such as Hurst exponent (HE), Higuchi fractal dimension (HFD), largest Lyapunov exponent (LLE) and sample entropy (SE) are extracted on these individual activities to provide improved discrimination. The ranked features are classified using support vector machine (SVM) with different kernel functions, decision tree (DT) and k-nearest neighbor (KNN) to select the best classifier. It is observed that SVM with radial basis function (RBF) kernel provides highest accuracy of 98%, sensitivity and specificity of 99.5% and 100%, respectively using five features. The developed methodology is ready for epilepsy screening and can be deployed in many programmes.

Longitudinal Changes in Tear Evaporation Rates After Eyelid Warming Therapies in Meibomian Gland Dysfunction

PURPOSE Lid warming is the major treatment for meibomian gland dysfunction (MGD). The purpose of the study was to determine the longitudinal changes of tear evaporation after lid warming in patients with MGD. METHODS Ninety patients with MGD were enrolled from a dry eye clinic at Singapore National Eye Center in an interventional trial. Participants were treated with hot towel (n = 22), EyeGiene (n = 22), or Blephasteam (n = 22) twice daily or a single 12-minute session of Lipiflow (n = 24). Ocular surface infrared thermography was performed at baseline and 4 and 12 weeks after the treatment, and image features were extracted from the captured images. RESULTS The baseline of conjunctival tear evaporation (TE) rate (n = 90) was 66.1 ± 21.1 W/min. The rates were not significantly different between sexes, ages, symptom severities, tear breakup times, Schirmer test, corneal fluorescein staining, or treatment groups. Using a general linear model (repeat measures), the conjunctival TE rate was reduced with time after treatment. A higher baseline evaporation rate (≥ 66 W/min) was associated with greater reduction of evaporation rate after treatment. Seven of 10 thermography features at baseline were predictive of reduction in irritative symptoms after treatment. CONCLUSIONS Conjunctival TE rates can be effectively reduced by lid warming treatment in some MGD patients. Individual baseline thermography image features can be predictive of the response to lid warming therapy. For patients that do not have excessive TE, additional therapy, for example, anti-inflammatory therapy, may be required.

Clinical Trial of Thermal Pulsation (LipiFlow) in Meibomian Gland Dysfunction With Preteatment Meibography.

Objectives: Thermal pulsation (LipiFlow) has been advocated for meibomian gland dysfunction (MGD) treatment and was found useful. We aimed to evaluate the efficacy and safety of thermal pulsation in Asian patients with different grades of meibomian gland loss. Methods: A hospital-based interventional study comparing thermal pulsation to warm compresses for MGD treatment. Fifty patients were recruited from the dry eye clinic of a Singapore tertiary eye hospital. The ocular surface and symptom were evaluated before treatment, and one and three months after treatment. Twenty-five patients underwent thermal pulsation (single session), whereas 25 patients underwent warm compresses (twice daily) for 3 months. Meibomian gland loss was graded using infrared meibography, whereas function was graded using the number of glands with liquid secretion. Results: The mean age (SD) of participants was 56.4 (11.4) years in the warm compress group and 55.6 (12.7) years in the thermal pulsation group. Seventy-six percent of the participants were female. Irritation symptom significantly improved over 3 months in both groups (P<0.01), whereas tear breakup time (TBUT) was modestly improved at 1 month in only the thermal pulsation group (P=0.048), without significant difference between both groups over the 3 months (P=0.88). There was also no significant difference in irritation symptom, TBUT, Schirmer test, and gland secretion variables between patients with different grades of gland loss or function at follow-ups. Conclusions: A single session of thermal pulsation was similar in its efficacy and safety profile to 3 months of twice daily warm compresses in Asians. Treatment efficacy was not affected by pretreatment gland loss.

Agreement of non-invasive tear break up time measurement between Tomey RT-7000 Auto Refractor-Keratometer and Oculus Keratograph 5M

Background It is difficult to standardize assessment of dry eye in different clinical settings. Increasingly, tear stability is recognized to be important for the definition and assessment of patients with dry eye. Recently, two commercially available instruments have been made available for objectively measuring noninvasive tear break-up time (NIBUT), as an indicator of tear stability: the Tomey RT-7000 Auto Refractor-Keratometer and Oculus Keratograph (K)5M. We aim to assess the agreement of NIBUT measurements using these modalities. Methods This prospective cross-sectional study was carried out in a tertiary referral eye center and involved 126 consecutive dry eye patients. NIBUT assessment was performed on the right eyes of participants with both the RT-7000 and the K5M techniques, with the order of assessment randomized. The Standardized Patient Evaluation of Eye Dryness (SPEED) questionnaires were administered to assess dry eye symptoms in the 2 weeks before assessment. Results The age of the participants was 56.0±14.3 years (69.84% females). Measurements for both modalities were non-normally distributed (right-skewed). The median RT-7000 and K5M readings were 4.2 (range 0.1–10.0) and 6.4 (0.1–24.9) seconds, respectively. RT-7000 and K5M readings were poorly correlated (ρ=0.061, P=0.495). Intraclass correlation coefficient between the modalities was 0.187 (95% confidence interval −0.097 to 0.406). The Bland–Altman plot showed no systematic differences between the readings with these machines. The agreement between machines was not different in different SPEED categories. Conclusion While there are theoretical and practical benefits of NIBUT for assessment of tear stability over dye-based methods, the agreement between the two modalities was poor. Hence, studies and trials assessing NIBUT should avoid using these modalities interchangeably for NIBUT assessment. More research is needed to improve consensus on how to determine NIBUT.

Lost to follow-up for appointments in a dedicated dry eye clinic

Objective Dry eye is a prevalent condition with significant socioeconomic burden. This study evaluates the extent and reasons for loss to follow-up (LTF) in a dedicated dry eye clinic. LTF refers to patient who discontinued visits for >2 years. Method The proportion of patients LTF and the demographics in a cohort of dry eye patients (2006 to 2010) were determined. A telephone survey was prospectively conducted for patients who were LTF. Results Of 505 patients, 240 (47.5%) were LTF. Associated demographic factors for LTF were male sex, non-Chinese ethnicity, and age group <30 years old (all P<0.05). The reasons for LTF through the telephone survey (response rate 77.9%) were categorized into three broad groups, stabilized dry eye condition (47%), personal/social factors (25%) and perceived insufficiency of healthcare delivery (28%). Only two (1.1%) were considered as management failures. The younger patients (age <50 years) were more likely to become LTF (P<0.001) due to stabilized dry eye disease, compared to older patients who were more likely to be LTF due to personal/social reasons (P=0.02). Poor communication and service factors under healthcare delivery were found to be higher (P=0.002) in those who visited once before they were LTF (8.5%) compared to those who visited multiple times before they were LTF (0.1%). Conclusion LTF was relatively common in hospital-based dry eye management. Female and older patients were less likely to stop consultation. Stabilized dry eye condition, common in younger patients, was the most common reason for LTF. Elderly patients have difficulty attending clinics due to nonmedical problems, which may require a more holistic approach.

The Association of Dry Eye Symptoms with Socioeconomic Factors and Quality of Life

Purpose: Dry eye is a common condition with significant morbidity and socioeconomic burden. The associated demographic factors that worsen utility in dry eye patients were not known. There were many questionnaire instruments advocated for dry eye documentation but none of these have been shown to correlate to quality of life (QoL). We aimed at examining the health related utility values in a group of dry eye patients and their associations.

Effects of wearing a daily disposable lens on tear film: a randomised controlled trial.

Contact lens‐induced dry eye is commonly encountered, although its extent is not well documented with daily disposable lenses. A novel type of contact lens system incorporating moisturising agent (alginic acid) has been developed. The aim of this study was to evaluate the effect of wearing daily 2‐hydroxyethyl methacrylate disposable contact lenses for seven days on tear stability, conjunctival and limbal redness and dry eye symptoms. Then, we aimed to determine whether lens solutions containing alginic acid had any influence on tear parameters.

Satisfaction and convenience of using terpenoid-impregnated eyelid wipes and teaching method in people without blepharitis

Purpose Demodex infestations cause blepharitis and are difficult to treat. Recently, a new type of eyelid wipes with terpenoids has been found effective. We aim to evaluate patient satisfaction after short-term use and compare two teaching modalities on the techniques of use. Patients and methods Eligible participants were taught to use eyelid wipes (Cliradex®) by either live or online video demonstration based on random allocation. Participants used the wipes twice daily for a week. All participants had prior evaluation of socioeconomic status, dry eye symptoms, and meibomian gland features. After 1 week, competence of use was assessed by participants showing their technique to the investigator, and a questionnaire on comfort, ease, and convenience of use was administered. Higher scores indicate greater satisfaction, and these levels are compared among the two teaching modalities using chi square. Results A total of 50 participants were recruited, with a mean age of 42±16 years, and 88% of the participants were females. Overall, median comfort level was 4.0 (range: 1–6), ease level was 5.0 (3–6), and convenience level was 5.0 (2–6). Median stinging was 2.0 (1–4), which corresponded to some but mild stinging. The median competence level was 4.0 (2–4), which corresponded to excellent competence. These satisfactory levels (ease, comfort, and convenience) experienced were not significantly associated with different socioeconomic indicators, that is, housing type, income, highest education level, and were not different between teaching methods (p>0.05). Conclusion Short-term use of Cliradex eyelid wipes seems to be acceptable to most people. The teaching instructions before using these wipes were equally effective – whether live or online video demonstration was used.