Evaluating the impact of information and support for people with nystagmus in the digital age: A patient and carer questionnaire study.

Background: Nystagmus is a disorder of rhythmic, involuntary oscillations of the eyes and can be classified as either infantile or acquired. Whether it occurs in isolation or as a part of other visual or neurological disorders, it causes significant visual dysfunction and problems with social functioning. In this study, we seek to understand ways in which people with nystagmus are currently supported across the UK and identify any geographical variations or disconnects between current practice and best practice, as judged by patients and their carers.Methods: A nationwide, qualitative, cross-sectional, questionnaire study of people with nystagmus and their carers. Recruitment was achieved through specialist clinics, charity events, online advertisements and social media calls. Data was gathered using five, age-appropriate questionnaires which were completed and returned to the research team between November 2016 and August 2018.Results: 184 respondents were included (89 carers, 47 patients aged 4-10 years, 5 aged 11-14 years, 4 aged 15-17 years and 39 > 18 years). Notably, respondents rated social media as the best source of information they have received, even compared with face-to-face consultation with medical professionals. Additionally, only 33% of the respondents had been offered visual impairment support. Notably, patterns of clinical practice and patient experience emerged according to geographical location, particularly provision of initial information and ongoing VI support.Conclusions: This study highlights a significant variation in the support and information received by people in the UK with nystagmus. It also supports the role of charities and increasingly, social media in the provision of patient information. The study also highlights the need for standardized guidelines for the management of patients with nystagmus, particularly with regard to support and information.

Absolute molecular transition frequencies measured by three cavity-enhanced spectroscopy techniques.

Absolute frequencies of unperturbed (12)C(16)O transitions from the near-infrared (3-0) band were measured with uncertainties five-fold lower than previously available data. The frequency axis of spectra was linked to the primary frequency standard. Three different cavity enhanced absorption and dispersion spectroscopic methods and various approaches to data analysis were used to estimate potential systematic instrumental errors. Except for a well established frequency-stabilized cavity ring-down spectroscopy, we applied the cavity mode-width spectroscopy and the one-dimensional cavity mode-dispersion spectroscopy for measurement of absorption and dispersion spectra, respectively. We demonstrated the highest quality of the dispersion line shape measured in optical spectroscopy so far. We obtained line positions of the Doppler-broadened R24 and R28 transitions with relative uncertainties at the level of 10(-10). The pressure shifting coefficients were measured and the influence of the line asymmetry on unperturbed line positions was analyzed. Our dispersion spectra are the first demonstration of molecular spectroscopy with both axes of the spectra directly linked to the primary frequency standard, which is particularly desirable for the future reference-grade measurements of molecular spectra.

Low-pressure line-shape study in molecular oxygen with absolute frequency reference.

We present a line-shape analysis of the rovibronic R1 Q2 transition of the oxygen B band resolved by the Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectroscopy technique in the low pressure range. The frequency axis of the spectra is linked by the ultra-narrow diode laser to the optical frequency comb in order to measure the absolute frequency at each point of the recorded spectra. Experimental spectra are fitted with various line-shape models: the Voigt profile, the Galatry profile, the Nelkin-Ghatak profile, the speed-dependent Voigt profile, and the speed-dependent Nelkin-Ghatak profile with quadratic and hypergeometric approximations for the speed dependence of collisional broadening and shifting. The influences of Dicke narrowing, speed-dependent effects, and correlation between phase- and velocity-changing collisions on the line shape are investigated. Values of line-shape parameters, including the absolute frequency of the transition 435685.24828(46) GHz, are reported.

Comb-linked, cavity ring-down spectroscopy for measurements of molecular transition frequencies at the kHz-level.

We present a low uncertainty measurement technique for determining molecular transition frequencies. This approach is complementary to sub-Doppler saturation spectroscopies and is expected to enable new frequency measurements for a wide variety of molecular species with uncertainties at the kHz-level. The technique involves measurements of Doppler broadened lines using cavity ring-down spectroscopy whereby the probe laser is actively locked to the ring-down cavity and the spectrum frequencies are linked directly to an optical frequency comb that is referenced to an atomic frequency standard. As a demonstration we have measured the transition frequency of the (30012) ← (00001) P14e line of CO2 near 1.57 µm with a combined standard uncertainty of ~9 kHz. This technique exhibits exceptional promise for measurements of transition frequencies and pressure shifting parameters of many weak absorbers, and indicates the potential for substantially improved measurements when compared to those obtained with conventional spectroscopic methods.

Cavity ring-down spectroscopy of the oxygen B-band with absolute frequency reference to the optical frequency comb.

Absolute positions of several oxygen B-band lines were measured with the Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectrometer. The frequency axis of spectra was linked to the optical frequency comb. Achieved uncertainties of line positions are between 0.9 and 2.9 MHz. Self-pressure shifts coefficients are also reported.

Pound-Drever-Hall-locked, frequency-stabilized cavity ring-down spectrometer.

We describe a high sensitivity and high spectral resolution laser absorption spectrometer based upon the frequency-stabilized cavity ring-down spectroscopy (FS-CRDS) technique. We used the Pound-Drever-Hall (PDH) method to lock the probe laser to the high-finesse ring-down cavity. We show that the concomitant narrowing of the probe laser line width leads to dramatically increased ring-down event acquisition rates (up to 14.3 kHz), improved spectrum signal-to-noise ratios for weak O(2) absorption spectra at λ = 687 nm and substantial increase in spectrum acquisition rates compared to implementations of FS-CRDS that do not incorporate high-bandwidth locking techniques. The minimum detectable absorption coefficient and the noise-equivalent absorption coefficient for the spectrometer are about 2×10(-10) cm(-1) and 7.5×10(-11) cm(-1)Hz(-1/2), respectively.