Tablet App halometer for the assessment of dysphotopsia

Purpose To assess the validity and repeatability of the Aston Halometer. Setting University clinic, United Kingdom. Design Prospective, repeated-measures experimental study. Methods The halometer comprises a bright light-emitting-diode (LED) glare source in the center of an iPad4. Letters subtending 0.21° (∼0.3 logMAR) were moved centrifugally from the LED in 0.05 degree steps in 8 orientations separated by 45 degrees for each of 4 contrast levels (1000, 500, 100, and 25 Weber contrast units [Cw]) in random order. Bangerter occlusion foils were inserted in front of the right eye to simulate monocular glare conditions in 20 subjects (mean age 27.7 ± 3.1 years). Subjects were positioned 2 meters from the screen in a dark room with the iPad controlled from an iPhone via Bluetooth operated by the researcher. The C-Quant straylight meter was also used with each of the foils to measure the level of straylight over the retina. Halometry and straylight repeatability was assessed at a second visit. Results Halo size increased with the different occlusion foils and target contrasts (F = 29.564, P <.001) as expected and in a pattern similar to straylight measures (F = 80.655, P <0.001). Lower contrast letters showed better sensitivity but larger glare-obscured areas, resulting in ceiling effects caused by the screen's field-of-view, with 500 Cw being the best compromise. Intraobserver and interobserver repeatability of the Aston Halometer was good (500Cw: 0.84 to 0.93 and 0.53 to 0.73) and similar to the straylight meter. Conclusion The halometer provides a sensitive, repeatable way of quantifying a patient-recognized form of disability glare in multiple orientations to add objectivity to subjectively reported discomfort glare.

Semantic sentiment analysis of Twitter

Sentiment analysis over Twitter offer organisations a fast and effective way to monitor the publics' feelings towards their brand, business, directors, etc. A wide range of features and methods for training sentiment classifiers for Twitter datasets have been researched in recent years with varying results. In this paper, we introduce a novel approach of adding semantics as additional features into the training set for sentiment analysis. For each extracted entity (e.g. iPhone) from tweets, we add its semantic concept (e.g. Apple product) as an additional feature, and measure the correlation of the representative concept with negative/positive sentiment. We apply this approach to predict sentiment for three different Twitter datasets. Our results show an average increase of F harmonic accuracy score for identifying both negative and positive sentiment of around 6.5% and 4.8% over the baselines of unigrams and part-of-speech features respectively. We also compare against an approach based on sentiment-bearing topic analysis, and find that semantic features produce better Recall and F score when classifying negative sentiment, and better Precision with lower Recall and F score in positive sentiment classification.

Determining which factors influence the optimum multifocal contact lens correction for presbyopia

Presbyopia is a consequence of ageing and is therefore increasing inprevalence due to an increase in the ageing population. Of the many methods available to manage presbyopia, the use of contact lenses is indeed a tried and tested reversible option for those wishing to be spectacle free. Contact lens options to correct presbyopia include multifocal contact lenses and monovision.Several options have been available for many years with available guides to help choose multifocal contact lenses. However there is no comprehensive way to help the practitioner selecting the best option for an individual. An examination of the simplest way of predicting the most suitable multifocal lens for a patient will only enhance and add to the current evidence available. The purpose of the study was to determine the current use of presbyopic correction modalities in an optometric practice population in the UK and to evaluate and compare the optical performance of four silicone hydrogel soft multifocal contact lenses and to compare multifocal performance with contact lens monovision. The presbyopic practice cohort principal forms of refractive correction were distance spectacles (with near and intermediate vision providedby a variety of other forms of correction), varifocal spectacles and unaided distance with reading spectacles, with few patients wearing contact lenses as their primary correction modality. The results of the multifocal contact lens randomised controlled trial showed that there were only minor differences in corneal physiology between the lens options. Visual acuity differences were observed for distance targets, but only for low contrast letters and under mesopic lighting conditions. At closer distances between 20cm and 67cm, the defocus curves demonstrated that there were significant differences in acuity between lens designs (p < 0.001) and there was an interaction between the lens design and the level of defocus (p < 0.001). None of the lenses showed a clear near addition, perhaps due to their more aspheric rather than zoned design. As expected, stereoacuity was reduced with monovision compared with the multifocal contact lens designs, although there were some differences between the multifocal lens designs (p < 0.05). Reading speed did not differ between lens designs (F = 1.082, p = 0.368), whereas there was a significant difference in critical print size (F = 7.543, p < 0.001). Glare was quantified with a novel halometer and halo size was found to significantly differ between lenses(F = 4.101, p = 0.004). The rating of iPhone image clarity was significantly different between presbyopic corrections (p = 0.002) as was the Near Acuity Visual Questionnaire (NAVQ) rating of near performance (F = 3.730, p = 0.007).The pupil size did not alter with contact lens design (F = 1.614, p = 0.175), but was larger in the dominant eye (F = 5.489, p = 0.025). Pupil decentration relative to the optical axis did not alter with contact lens design (F = 0.777, p =0.542), but was also greater in the dominant eye (F = 9.917, p = 0.003). It was interesting to note that there was no difference in spherical aberrations induced between the contact lens designs (p > 0.05), with eye dominance (p > 0.05) oroptical component (ocular, corneal or internal: p > 0.05). In terms of subjective patient lens preference, 10 patients preferred monovision,12 Biofinity multifocal lens, 7 Purevision 2 for Presbyopia, 4 AirOptix multifocal and 2 Oasys multifocal contact lenses. However, there were no differences in demographic factors relating to lifestyle or personality, or physiological characteristics such as pupil size or ocular aberrations as measured at baseline,which would allow a practitioner to identify which lens modality the patient would prefer. In terms of the performance of patients with their preferred lens, it emerged that Biofinity multifocal lens preferring patients had a better high contrast acuity under photopic conditions, maintained their reading speed at smaller print sizes and subjectively rated iPhone clarity as better with this lens compared with the other lens designs trialled. Patients who preferred monovision had a lower acuity across a range of distances and a larger area of glare than those patients preferring other lens designs that was unexplained by the clinical metrics measured. However, it seemed that a complex interaction of aberrations may drive lens preference. New clinical tests or more diverse lens designs which may allow practitioners to prescribe patients the presbyopic contact lens option that will work best for them first time remains a hope for the future.