Cat-PROM5: a brief psychometrically robust self-report questionnaire instrument for cataract surgery.

PurposeTo develop a short, psychometrically robust and responsive cataract patient reported outcome measure suitable for use in high-volume surgical environments.MethodsA prospective study in which participants completed development versions of questionnaires exploring the quality of their eyesight using items harvested from two existing United Kingdom developed parent questionnaires. Participants were 822 patients awaiting cataract surgery recruited from 4 cataract surgical centres based in the UK. Exclusion criteria were other visually significant comorbidities and age <50 years. An iterative multi-stage process of evaluation using Rasch and factor analyses with sequential item reduction was undertaken.ResultsA definitive item set of just five items delivered performance in accordance with the requirements of the Rasch model: no threshold disordering, no misfitting items, Rasch-based reliability 0.90, person separation 2.98, Cronbach's α 0.89, good targeting of questions to patients with cataract with pre-operative item mean -0.41 logits and absence of significant floor or ceiling effects, minor deviations of item invariance, and confirmed unidimensionality. The test-re-test repeatability intra-class correlation coefficient was 0.89 with excellent responsiveness to surgery, Cohen's d -1.45 SD. Rasch calibration values are provided for Cat-PROM5 users.ConclusionsA psychometrically robust and highly responsive five-item cataract surgery patient reported outcome measure has been developed, which is suitable for use in high-volume cataract surgical services.

Cataract surgery patient-reported outcome measures: a head-to-head comparison of the psychometric performance and patient acceptability of the Cat-PROM5 and Catquest-9SF self-report questionnaires.

Background Cataract surgery is the most frequently undertaken NHS surgical procedure. Visual acuity (VA) provides a poor indication of visual difficulty in a complex visual world. In the absence of a suitable outcome metric, recent efforts have been directed towards the development of a cataract patient-reported outcome measure (PROM) of sufficient brevity, precision, and responsiveness to be implementable in routine high volume clinical services.Aim To compare and contrast the two most promising candidate PROMs for routine cataract surgery.Method The psychometric performance and patient acceptability of the recently UK developed five-item Cat-PROM5 questionnaire was compared with the English translation of the Swedish nine-item Catquest-9SF using Rasch-based performance metrics and qualitative semistructured interviews.Results Rasch-based performance was assessed in 822 typical NHS cataract surgery patients across four centres in England. Both questionnaires demonstrated good to excellent performance for all metrics assessed, including Person Reliability Indices of 0.90 (Cat-PROM5) and 0.88 (Catquest-9SF), responsiveness to surgery (Cohen's standardized effect size) of 1.45 SD (Cat-PROM5) and 1.47 SD (Catquest-9SF) and they were highly correlated with each other (R=0.85). Qualitative assessments confirmed that both questionnaires were acceptable to patients, including in the presence of ocular comorbidities. Preferences were expressed for the shorter Cat-PROM5, which allowed patients to map their own issues to the questions as opposed to the more restrictive specific scenarios of Catquest-9SF.Conclusion The recently UK developed Cat-PROM5 cataract surgery questionnaire is shorter, with performance and patient acceptability at least as good or better than the previous 'best of class' Catquest-9SF instrument.

An atom trap trace analysis system for measuring krypton contamination in xenon dark matter detectors.

We have developed an atom trap trace analysis (ATTA) system to measure Kr in Xe at the part per trillion (ppt) level, a prerequisite for the sensitivity achievable with liquid xenon dark matter detectors beyond the current generation. Since Ar and Kr have similar laser cooling wavelengths, the apparatus has been tested with Ar to avoid contamination prior to measuring Xe samples. A radio-frequency plasma discharge generates a beam of metastable atoms which is optically collimated, slowed, and trapped using standard magneto-optical techniques. Based on the measured overall system efficiency of 1.2 × 10(-8) (detection mode), we expect the ATTA system to reach the design goal sensitivity to ppt concentrations of Kr in Xe in <2 h.

Synchronization of quasiperiodic oscillations to a periodic force studied with semiconductor lasers.

We experimentally study synchronization processes in a system of two different multisection semiconductor lasers. Periodic self-pulsations of laser 1 are injected into laser 2, which is operating in a regime with two-frequency quasiperiodic self-pulsations. The experimental system demonstrates the new type of transitions to synchrony between three frequencies which has been recently revealed using generic coupled phase and van der Pol oscillator models. In particular, resonances of quasiperiodic oscillations at integer winding numbers three and five are shown to break up before locking to the injected periodic signal. Moreover, carefully determining the coherence of the noisy oscillations, we reveal so far unexplored processes of coherence transfer to nonsynchronized oscillations.

Tristability of a semiconductor laser due to time-delayed optical feedback.

We present an experimental and theoretical study of multistability of a single-mode laser subject to feedback through phase tuning and amplifier sections integrated on the same chip. Closely above threshold, a regime of tristability of continuous-wave (CW) states is found for multiple ranges of amplifier and phase currents. The separation between the tristable wavelengths agrees with the channel spacing of dense wavelength multiplexing in the C band of optical communication making the device interesting for ternary logic applications. Complementary theoretical investigations in the framework of the paradigmatic Lang-Kobayashi model provide a consistent understanding of the experimental findings and additionally yield an analytic formula expressing the maximum number of coexisting stable CW states by the linewidth-enhancement factor alpha . Tristability belongs to the alpha range from 5 to 8 in good agreement with experiment.

Anharmonicity of potentials of atoms in potassium hydrogensulfide (KDS) determined by neutron single-crystal diffraction

Potassium hydrogensulfide (KHS) is an ionic compound with an anionic molecular group HS(-). The fast reorientational disorder of the anions was determined for the ambient temperature modification [R3;m; Jeffrey (1974). Can. J. Phys. 52, 2370-2378]. Single crystals are available now as protonated or deuterated specimens. With neutron single-crystal diffraction at room temperature, a considerable anharmonicity of the atom potential of the H or D atoms was observed. Even the thermal motions of K and S atoms show small deviations from an isotropic probability density function, which can be modelled using anharmonic temperature factors. The temperature factors of the atoms were expanded into a Gram-Charlier series [Kuhs (1992). Acta Cryst. A48, 80-98] in order to evaluate the anharmonicity quantitatively. Parameters up to a fourth-order approximation are relevant for the D atoms. Results from neutron single-crystal diffraction are compared with split-atom models extracted from neutron powder diffraction patterns of fully deuterated samples.