Bal Dhillon

Is cataract surgery justified in patients with age related macular degeneration? A visual function and quality of life assessment

AIMS To determine whether patients with age related macular degeneration (ARMD) benefit from cataract surgery in terms of visual function and quality of life measures, and to assess the impact of surgery on the progression of ARMD. METHODS A prospective study was carried out of patients with and without ARMD undergoing cataract surgery. Data were collected from 187 patients at the Princess Alexandra Eye Pavilion, Edinburgh and the Oxford Eye Hospital, Oxford. The patients were divided into three groups: (1) a control group with ARMD and no surgery (n=41), (2) a study group of patients with ARMD who underwent cataract surgery (n=90), and (3) a second control group of patients without ocular comorbidities who underwent cataract surgery (n=56). Visual function and quality of life assessments were carried out at baseline and 3–5 months after baseline or surgery. RESULTS There were significant improvements both in terms of quality of life and visual function measures in the study group. Benefits were greater in patients with moderate cataract irrespective of the degree of ARMD. No increased incidence in progression to the “wet” form of ARMD was found. Improvements in quality of life measures and visual function were more pronounced in patients with no ocular comorbidities. CONCLUSIONS Patients with mild and moderate degrees of ARMD do benefit from cataract surgery and the benefits are greater in patients with moderate degrees of lens opacity. Longer follow up is required to assess the risk of increased ARMD progression.

Fractal analysis of retinal vessels suggests that a distinct vasculopathy causes lacunar stroke

Objectives: Lacunar strokes account for 25% of all ischemic strokes and may represent the cerebral manifestation of a systemic small vessel vasculopathy of unknown etiology. Altered retinal vessel fractal dimensions may act as a surrogate marker for diseased cerebral vessels. We used a cross-sectional study to investigate fractal properties of retinal vessels in lacunar stroke. Methods: We recruited patients presenting with lacunar stroke and patients with minor cortical stroke as controls. All patients were examined by a stroke expert and had MRI at presentation. Digital retinal photographs were taken of both eyes. Monofractal and multifractal analyses were performed with custom-written semiautomated software. Results: We recruited 183 patients. Seventeen were excluded owing to poor photographic quality, leaving 166 patients (86 with lacunar and 80 with cortical stroke). The mean age was 67.3 years (SD 11.5 years). The patients with lacunar stroke were younger but the prevalence of diabetes, hypertension, and white matter hyperintensities did not differ between the groups. The mean Dbox (monofractal dimension) was 1.42 (SD 0.02), the mean D0 (multifractal dimension) 1.67 (SD 0.03). With multivariate analysis, decreased Dbox and D0 (both representing decreased branching complexity) were associated with increasing age and lacunar stroke subtype after correcting for hypertension, diabetes, stroke severity, and white matter hyperintensity scores. Conclusions: Lacunar stroke subtype and increasing age are associated with decreased fractal dimensions, suggesting a loss of branching complexity. Further studies should concentrate on longitudinal associations with other manifestations of cerebral small vessel disease.

Validating retinal fundus image analysis algorithms: Issues and a proposal

This paper concerns the validation of automatic retinal image analysis (ARIA) algorithms. For reasons of space and consistency, we concentrate on the validation of algorithms processing color fundus camera images, currently the largest section of the ARIA literature. We sketch the context (imaging instruments and target tasks) of ARIA validation, summarizing the main image analysis and validation techniques. We then present a list of recommendations focusing on the creation of large repositories of test data created by international consortia, easily accessible via moderated Web sites, including multicenter annotations by multiple experts, specific to clinical tasks, and capable of running submitted software automatically on the data stored, with clear and widely agreed-on performance criteria, to provide a fair comparison.

Differences in retinal vessels support a distinct vasculopathy causing lacunar stroke.

Background: Lacunar stroke is common, but the etiology of the small vessel abnormality is unknown. Retinal vessels share ontogeny, size, and physiologic characteristics with cerebral small vessels, and retinopathy is associated with stroke. We compared retinal microvessel appearance as a surrogate for cerebral small vessels in patients with lacunar and large artery cortical ischemic stroke. Methods: We prospectively recruited patients with lacunar ischemic stroke and cortical stroke controls. We took digital retinal photographs of each eye. We assessed central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) diameters and arteriovenous ratios (AVRs) using semiautomated computer software methods and quantified arteriovenous nicking and focal arteriolar narrowing. Results: Among 212 patients (105 lacunar, 107 cortical strokes) of mean age 68 years (SD 12 years), AVR was decreased (0.76 vs 0.78, p = 0.03) and CRVE was increased (44.9 pixels/218 μm vs 42.8 pixels/208 μm, p = 0.01) in lacunar patients compared with cortical patients, but CRAE did not differ (33.2 pixels/161 μm vs 33.7 pixels/163 μm, p = 0.4). On multivariable analysis, increased CRVE was associated with lacunar stroke subtype (p = 0.03) and younger age (p < 0.001) after correcting for other vascular risk factors. Arteriovenous nicking and focal arteriolar narrowing did not differ between ischemic stroke subtypes. Conclusions: Retinal venules are wider and arteriovenous ratios are smaller in patients with lacunar strokes compared with those in patients with cortical strokes.

Systems of analysis of posterior capsule opacification.

This paper demonstrates the wide variety of systems for the analysis of posterior capsular opacification (PCO). No single system has been proved to be a gold standard and it is difficult to comment on the advantages of one system over another with the limited current knowledge on the effects of PCO on vision. There are few studies that actually compare the different systems of analysis. Researchers must ensure that the systems they use for PCO analysis are objective and must give maximum consideration to ensuring potential systematic errors are reduced to a minimum. Further research is required into how the various types and locations of PCO affect vision and how well different systems of analysis perform.

Transorbital Sonographic Evaluation of Normal Optic Nerve Sheath Diameter in Healthy Volunteers in Bangladesh

Introduction Measurement of optic nerve sheath diameter (ONSD) by ultrasound is increasingly used as a marker to detect raised intracranial pressure (ICP). ONSD varies with age and there is no clear consensus between studies for an upper limit of normal. Knowledge of normal ONSD in a healthy population is essential to interpret this measurement. Methods In a prospective observational study, ONSD was measured using a 15 MHz ultrasound probe in healthy volunteers in Chittagong, Bangladesh. The aims were to determine the normal range of ONSD in healthy Bangladeshi adults and children, compare measurements in males and females, horizontal and vertical beam orientations and left and right eyes in the same individual and to determine whether ONSD varies with head circumference independent of age. Results 136 subjects were enrolled, 12.5% of whom were age 16 or under. Median ONSD was 4.41 mm with 95% of subjects in the range 4.25–4.75 mm. ONSD was bimodally distributed. There was no relationship between ONSD and age (≥4 years), gender, head circumference, and no difference in left vs right eye or horizontal vs vertical beam. Conclusions Ultrasonographic ONSD in Bangladeshi healthy volunteers has a narrow bimodal distribution independent of age (≥4 years), gender and head circumference. ONSD >4.75 mm in this population should be considered abnormal.

Retinal imaging as a source of biomarkers for diagnosis, characterization and prognosis of chronic illness or long-term conditions

The black void behind the pupil was optically impenetrable before the invention of the ophthalmoscope by von Helmholtz over 150 years ago. Advances in retinal imaging and image processing, especially over the past decade, have opened a route to another unexplored landscape, the retinal neurovascular architecture and the retinal ganglion pathways linking to the central nervous system beyond. Exploiting these research opportunities requires multidisciplinary teams to explore the interface sitting at the border between ophthalmology, neurology and computing science. It is from the detail and depth of retinal phenotyping that novel metrics and candidate biomarkers are likely to emerge. Confirmation that in vivo retinal neurovascular measures are predictive of microvascular change in the brain and other organs is likely to be a major area of research activity over the next decade. Unlocking this hidden potential within the retina requires integration of structural and functional data sets, that is, multimodal mapping and longitudinal studies spanning the natural history of the disease process. And with further advances in imaging, it is likely that this area of retinal research will remain active and clinically relevant for many years to come. Accordingly, this review looks at state-of-the-art retinal imaging and its application to diagnosis, characterization and prognosis of chronic illness or long-term conditions.

The role of retinal regulation of sleep in health and disease

The process of photoentrainment, through the activation of photoreceptor transduction cascades, influences the circadian physiology of many life forms from primitive invertebrates to primates. In humans, a population of intrinsically photosensitive retinal ganglion cells (ipRGCs) is responsible for mediating the circadian rhythm and is susceptible to primary dysfunction affecting this cell population specifically, or disorders influencing light activation of retinal ganglion photoreceptors. The former may arise through cell depletion in conditions such as inherited or acquired optic neuropathies or conditions like Parkinsons disease which may alter retinal dopamine-mediated neurotransmission, and the latter, secondary to common causes of light transmission reduction associated with ageing and cataract. This review examines the current evidence linking ocular pathology and the resultant reduction in retinal phototransduction with circadian disturbances and sleep disorders, with downstream effects on our overall physiological integrity. As our understanding of the effects of light pathways on circadian biology develops, therapeutic modalities based upon the underlying pathophysiological processes are emerging, although the direct measurement, consequences and treatment of relative or absolute ipRGC dysfunction remain to be fully and clearly elucidated in man.

Quality of life and relative importance: A comparison of time trade-off and conjoint analysis methods in patients with age-related macular degeneration

Aim: To investigate the relative priorities in quality of life (QoL) in patients with age-related macular degeneration (AMD). Methods: Measures of visual function, QoL and utility associated with visual loss were obtained from 122 patients with AMD classified according to macular morphology. The two methods of utility assessment were time trade-off (TTO) and conjoint analysis (CA), which have been recommended by the UK’s National Institute of Clinical Excellence as techniques for the assessment of healthcare priorities. Results: Results show that the two methods for assessing utility are poorly related: TTO relates moderately to visual function and disease severity but CA does not. CA identified two different subgroups of patients: one with outdoor mobility and the other with reading as their main priority. Conclusion: Further work is needed and caution required in interpreting data obtained using these methodologies for determining their relative importance in vision-related QoL studies.

Contextual detection of ischemic regions in ultra-wide-field-of-view retinal fluorescein angiograms

We report a novel prototype algorithm using contextual knowledge to locate ischemic regions in ultra- wide-field-of-view retinal fluorescein angiograms. We use high- resolution images acquired by an Optos ultra-wide-field-of- view (more than 200 degrees) scanning laser ophthalmoscope. We leverage the simultaneous occurrence of ischemia with a number of other signs, detected automatically, typical for the state of progress of the condition in a diabetic patient. The specific nature of ischemic and non-ischemic regions is determined with an AdaBoost learning algorithm. Preliminary results demonstrate above 80% pixel classification accuracy against manual annotations.