Dynamic refraction and anterior segment OCT biometry during accommodation.

Accommodation is the process by which the eye changes focus. These changes are the result of changes to the shape of the crystalline lens. Few prior studies have quantified the relation between lens shape and ocular accommodation, primarily at discrete static accommodation states. We present an instrument that enables measurements of the relation between changes in lens shape and changes in optical power continuously during accommodation. The system combines an autorefractor to measure ocular power, a visual fixation target to stimulate accommodation, and an optical coherence tomography (OCT) system to image the anterior segment and measure ocular distances. Measurements of ocular dimensions and refraction acquired dynamically on three human subjects are presented. The individual accommodative responses are analyzed to correlate the ocular power changes with changes in ocular dimensions.

Exploring the sustainable impacts of a clinical healthcare research scholarship programme.

BACKGROUND: The NHS is the first public body globally to commit to net zero. AIM: This study aimed to explore the environmental sustainability impact of a hospital scholarship programme. METHOD: A sustainable quality improvement value framework was used to measure the programme's environmental, social and financial effects. RESULTS: The social impact through face-to-face contact was most valued by scholars; there were also savings in carbon emissions and costs. DISCUSSION: Training in sustainability is essential for the workforce but little infrastructure and expertise are available within organisations to support staff to provide sustainable healthcare in day-to-day practice. CONCLUSION: Sustainable healthcare should be supported by education and national guidance and implementation plans should be drawn up to this end. The social impact of the framework used is often seen as less important than its environmental and financial components; however, as its value to scholars illustrates, the components are intertwined and should be considered of equal importance.

"Concrete ways we can make a difference": A multi-centre, multi-professional evaluation of sustainability in quality improvement education.

Quality improvement (QI) projects are a mandatory part of postgraduate medical training in the UK and graduating medical students must be competent in QI theory. We evaluated an educational toolkit that links concepts of sustainable healthcare with established quality improvement methodologies (the SusQI approach, available at www.susqi.org). The SusQI approach was implemented across a range of undergraduate and postgraduate nursing and medical education contexts. Educational strategies included guided online learning, live interactive webinars, small group activities and scaffolded project work. The evaluation strategy was informed by theories of academic motivation, educational value within communities of practice and behaviour change. A simultaneous nested design was tested using a mixed methods survey with input from learners and teachers. 177 survey responses were analysed to quantify and compare self-rated impacts of teaching across different audiences. Qualitative data were inductively coded into themes that were categorised according to above theoretical frameworks. Participants felt that this was 'time well spent' and many described transformative impacts that guided their daily professional practice beyond learning about QI. We suggest that meaningful space is found within both undergraduate and postgraduate healthcare curricula for SusQI, as a way of engaging and motivating learners to contribute to the creation of a sustainable healthcare system.

Midwifery research in areas of deprivation and need: the MeRIDiAN project.

Background: Areas with high levels of deprivation often have the lowest numbers of research participation. In January 2020, a maternity research service was established at a UK National Health Service (NHS) Trust incorporating a project monitoring equity of access to pregnant people from areas of deprivation and need. Aims: The aim is to monitor maternity research opportunities for pregnant people in areas of deprivation and need. Method: A collaborative working group was established. Using the Index of Multiple Deprivation levels (IMD) levels; 1-4 were considered 'areas in need'. Data were collected over a 12-month period from January 2020. Results: Fifty-four pregnant people (3.1%), out of 1762 who delivered during 2020, were recruited to one of three research studies ('Big Baby', 'POOL' and 'PAN-COVID'). The majority of pregnant people (65.9%) who delivered a baby were in IMD levels 1-4. Recruitment within IMD levels 1-4: 'PAN-COVID' at 86.7%, followed by 'Big Baby' with 77.3% and 'POOL' at 70.6%. COVID-19 pandemic presented challenges which impacted research delivery, including availability of research studies. Conclusion: This project was founded due to concerns that pregnant people from areas of need would be under-represented in research. We have found that this has not occurred. Recommendations are being put in place to ensure equity of access for all.

Age-Dependence of the Peripheral Defocus of the Isolated Human Crystalline Lens.

Purpose: To characterize the peripheral defocus of isolated human crystalline lenses and its age dependence. Methods: Data were acquired on 116 isolated lenses from 99 human eyes (age range, 0.03-61 years; postmortem time, 40.1 ± 21.4 hours). Lenses were placed in a custom-built combined laser ray tracing and optical coherence tomography system that measures the slopes of rays refracted through the lens for on-axis and off-axis incidence angles. Ray slopes were measured by recording spot patterns as a function of axial position with an imaging sensor mounted on a positioning stage below the tissue chamber. Delivery angles ranged from -30° to +30° in 5° increments using a 6 mm × 6 mm raster scan with 0.5-mm spacing. Lens power at each angle was calculated by finding the axial position that minimizes the root-mean-square size of the spot pattern formed by the 49 central rays, corresponding to a 3-mm zone on-axis. The age dependence of the on-axis and off-axis optical power and the relative peripheral defocus (difference between off-axis and on-axis power) of lenses were quantified. Results: At all angles, lens power decreased significantly with age. Lens power increased with increasing delivery angle for all lenses, corresponding to a shift toward myopic peripheral defocus. There was a statistically significant decrease in the lens peripheral defocus with age. Conclusions: The isolated human lens power increases with increasing field angle. The lens relative peripheral defocus decreases with age, which may contribute to the age-related changes of ocular peripheral defocus during refractive development.

Morphometric analysis of in vitro human crystalline lenses using digital shadow photogrammetry.

There is a great need for accurate biometric data on human lenses. To meet this, a compact tabletop optical comparator, the minishadowgraph, was built for measuring isolated eye lens shape and dimensions while the lens was fully immersed in supporting medium. The instrument was based around a specially designed cell and an illumination system which permitted image recording in both sagittal and equatorial (coronal) directions. Data were acquired with a digital camera and analyzed using a specially written MATLAB program as well as by manual measurements in image analysis software. The possible effect of lens orientation and gravity on the dimensions was examined by measuring dimensions with anterior or posterior surfaces up and by measuring lenses with calipers after removal from the minishadowgraph cell. Dimensions, curvatures and shape factors were obtained for 134 fully accommodated lenses ranging in age from birth to 88 years postnatal. Of these, 41 were from donors aged under 20 years, ages which are generally of limited availability. Thickness and diameter showed the same age-related trends described in previous studies but, for the lenses measured in air, age-dependent differences were observed in thickness (-5 to 0%) and diameter (+5 to 0%), consistent with gravitational sag. Anterior and posterior radii of curvature of the central 3 or 6 mm, depending on lens diameter, increase with age, with the anterior increase greater than the posterior. The anterior surface shape of the neonatal lens is that of a prolate ellipse and the posterior, an oblate ellipse. Both surfaces become hyperbolic after age 20. The data presented here on dimensions, shape and sagging will be of great value in assessing age-related changes in the optical and mechanical performance of the lens. In particular, the comprehensive data set from donors aged under 20 years provides a unique and valuable insight to the changes in size and shape during the early dynamic growth period of the lens.

In vivo measurement of the human crystalline lens equivalent refractive index using extended-depth OCT.

The lens equivalent refractive index (RI) is commonly used in calculations of crystalline lens power. However, accurate determination of the equivalent RI in vivo is challenging due to the need of multiple measurements with different ocular biometry devices. A custom extended-depth Spectral Domain-OCT system was utilized to provide measurements of corneal and lens surface curvatures and all intraocular distances required for determination of the lens equivalent RI. Ocular biometry and refraction were input into a computational model eye from which the equivalent RI was calculated. Results derived from human subjects of a wide age range show a decrease in RI with age and demonstrate the capability of in vivo measurements of the equivalent RI with extended-depth OCT.

System for on- and off-axis volumetric OCT imaging and ray tracing aberrometry of the crystalline lens.

We present a new in vitro instrument for measuring shape and wavefront aberrations of the primate crystalline lens, both on- and off-axis, while simulating accommodation with a motorized lens stretching system. The instrument merges spectral domain optical coherence tomography (SD-OCT) imaging and ray tracing aberrometry using an approach that senses wavefront aberrations of the lens with the OCT probing beam. Accuracy and repeatability of aberration measurements were quantified. Preliminary experiments on two human and four cynomolgus monkey lenses demonstrate the ability of the system to measure the lens shape, spherical aberration and peripheral defocus, and their changes during simulated accommodation.

Assessment of eye length changes in accommodation using dynamic extended-depth OCT.

It has been suggested that accommodation induces increases in axial eye length which could contribute to the development of myopia. However, it is debated whether changes in eye length occur during accommodation as the degree of change varies widely across literature. In this study, an extended-depth optical coherence tomography (OCT) system that provides dynamic whole eye biometry was utilized to assess changes in lens thickness (LT) and axial eye length (AEL) in young subjects responding to step disaccommodation stimuli of amplitude 2D, 4D, and 6D. The decrease in lens thickness with disaccommodation was strongly correlated with stimulus amplitude. No statistically significant changes in AEL during accommodation were observed.

Quantification of the ciliary muscle and crystalline lens interaction during accommodation with synchronous OCT imaging.

Two SD-OCT systems and a dual channel accommodation target were combined and precisely synchronized to simultaneously image the anterior segment and the ciliary muscle during dynamic accommodation. The imaging system simultaneously generates two synchronized OCT image sequences of the anterior segment and ciliary muscle with an imaging speed of 13 frames per second. The system was used to acquire OCT image sequences of a non-presbyopic and a pre-presbyopic subject accommodating in response to step changes in vergence. The image sequences were processed to extract dynamic morphological data from the crystalline lens and the ciliary muscle. The synchronization between the OCT systems allowed the precise correlation of anatomical changes occurring in the crystalline lens and ciliary muscle at identical time points during accommodation. To describe the dynamic interaction between the crystalline lens and ciliary muscle, we introduce accommodation state diagrams that display the relation between anatomical changes occurring in the accommodating crystalline lens and ciliary muscle.