4D Light FIeld Ophthalmoscope: A Study of Plenoptic Imaging for Retinal Imaging

The application of 4D Light Field technique to retinal imaging is proposed as a multi- modality imaging device. A feasibility study developed with numerical simulations is presente

Differential amplitude scanning for retinal imaging: a theoretical study

A differential amplitude scanning system for ophthalmoscopy is described theoretically. The differential scanning ophthalmoscope (DSO) samples the retina with two laterally displaced spots. The signal measured is the difference between the irradiance from these two locations. The theoretical analysis of the DSO shows it offers increased contrast at high spatial frequencies and only weak contributions from the low frequencies. This enables high-gain, low-noise detection that maximizes contrast

Structured illumination microscopy for in-vivo human retinal imaging: a theoretical assessment

Structured illumination microscopy applied to in-vivo retinal imaging has the potential to provide a low-cost and powerful diagnostic tool for retinal disease. In this paper the key parameters that affect performance in structured illumination ophthalmoscopy are studied theoretically. These include the number of images that need to be acquired in order to generate a sectioned image, which is affected by the non-stationary nature of the retina during acquisition, the choice of spatial frequency of the illuminating sinusoid, the effect of typical ocular aberrations on axial resolution and the nature of the sinusoidal pattern produced by the illumination system. The results indicate that structured illumination ophthalmoscopy can be a robust technique for achieving axial sectioning in retinal imaging without the need for complex optical systems

Study of the dynamic tear film aberrations using a curvature sensing setup

The advancement in adaptive optics in recent years has increased the interest in the dynamic aberrations of the eye, including those introduced by the first optical surface provided by the tear film. A curvature sensing system to measure the dynamic topography of the tear film is described. This optical system was used to measure the aberrations of the tear film on 14 eyes. The evolution of this surface is monitored through videos of the tear film topography. The effect on optical quality is studied from the time-evolution of the RMS wavefront error showing non-negligible aberration variations attributed to the tear film layer; the effect of tear film break-up on the ocular optical quality is also discussed. Furthermore, the aberration maps are decomposed into their constituent Zernike components showing stronger contributions from 4th order terms, and also from those components with vertical symmetry which can be attributed to the effect of the eye lids on the tear film. Finally, the power spectra of the RMS wavefront error evolution show that the strongest contributions of the tear film aberrations are to be found at low frequencies, typically below 2Hz

Hypopituitarism : a review on the diagnosis and management of central hypoadrenalism and hypothyroidism

A variety of conditions can result in hypopituitarism and this article focuses on the diagnosis, treatment and management of central hypoadrenalism and hypothyroidism. Central hypoadrenalism, if untreated, can potentially prove to be fatal and thus it is imperative that a timely diagnosis is done and life long supplementation instituted. Different glucocorticoid supplementation regimes together with possible side effects are discussed. Life long thyroxine replacement is needed for central hypothyroidism. Particular aspects regarding the diagnosis and management of central hypothyroidism are tackled. Important elements in the management of these patients, so as to ensure suitable supplementation are proper clinical and biochemical monitoring together with effective patient education.peer-reviewe

Diabetes in pregnancy : diagnosis, management, outcome and complications

Introduction: Numerous perinatal complications of diabetes in pregnancy have been recognised. Maternal post-partum complications can be equally devastating. Method: In this study, a cohort of known type 1 and type 2 pregnant diabetics and newly diagnosed Gestational Diabetes Mellitus (GDM) patients were analysed. Data collected was analysed in terms of method of diagnosis, gestational age at diagnosis for GDM, relevant medical or obstetric history, subsequent management and follow up. Results: Out of 79 viable pregnancies, 69.6% of patients were diagnosed with GDM, 13.9% with type 2 DM and 16.5% with type 1 DM. Mean gestational age for the GDM cohort was 37.9 (±1.6) weeks, 35.5 (±3.7) weeks in Type 2 and 37.1 (±0.7) weeks in the Type 1 cohort (p = 0.010). 20.3% of all cohort and specifically 23.6% of GDM pregnancies had a fetus which was large for gestational age. 30% of GDM patients, 25.5% of Type 2 DM patients and 84.6% of Type 1 DM patients, had their blood glucose controlled by an insulin infusion pump peri-partum. Mean HbA1C in the third trimester was 6.0%, 6.3% and 7.1% in GDM, Type 2 and Type 1 diabetics respectively (p = 0.004). A negative correlation was seen between HbA1C levels in third trimester and delivery gestational age (p < 0.001). Conclusion: Our findings emphasize the need for close follow up of these patients. Implementing a structured and holistic multidisciplinary team may have an impact on outcome, focusing on maternal education, in particular in GDM patients and their risk of developing type 2 DM in the future.peer-reviewe

Curvature sensor for the measurement of the static corneal topography and the dynamic tear film topography in the human eye

A system to measure the topography of the first optical surface of the human eye noninvasively by using a curvature sensor is described. The static corneal topography and the dynamic topography of the tear film can both be measured, and the topographies obtained are presented. The system makes possible the study of the dynamic aberrations introduced by the tear film to determine their contribution to the overall ocular aberrations in healthy eyes, eyes with corneal pathologies, and eyes wearing contact lenses

New methodology to measure the dynamics of ocular wave front aberrations during small amplitude changes of accommodation

We present a methodology to measure the systematic changes of aberrations induced by small changes in amplitude of accommodation. We use a method similar the one used in electrophysiology, where a periodic stimulus is presented to the eye and many periods (epochs) of the stimulus are averaged. Using this technique we have measured changes in higher order aberrations from 0.006μm to 0.02μm and correlated them with amplitude changes of accommodation as small as 0.14D. These small changes would have been undetectable without epoch averaging. The correlation coefficients of Zernike terms with defocus were calculated, demonstrating higher values of correlation for epoch averaging. The accurate monitoring of defocus at the start of the accommodation response has shown some interesting trends that may be related with the mechanisms behind accommodation

The blue cats of Malta

Academic literature yields very little information that makes reference to the Maltese cats. The Notarial archives, usually a source of rich information, in that they describe livestock that are part of a transaction, yield no information on cats, most probably, because cats were not held to represent a significant capital. Furthermore, the available literature usually makes single line references to the Maltese cat. Nonetheless, in days gone by, Malta did have a breed of unique cats described as being of a curious dark griseous (grey/blue) colour and which were highly esteemed and sought after in Sicily, and Italy.2 The Maltese Blue cats were also known locally as il-Qattus Irmiedi. The aim of this article is to present aspects associated with the breed known as the Maltese Blue cat.peer-reviewe

Wavefront curvature sensing for the human eye

In this paper we present a curvature wavefront sensor for the eye. The layout proposed is novel, whilst the algorithm used has been adapted from previously published work [Roddier, F.; Roddier, C. Appl. Opt. 1991, 30, 1325–1327]. The design of the set-up incorporates two field lenses that, together with a beam separator, define the distance Δz between the two sampled planes. We present a feasibility study to use this particular combination of optical configuration and retrieval algorithm in the eye. We present calibration curves and results from three real eyes