19 research outputs found
Visual dysfunction in macular telangiectasia type 2
Macular telangiectasia type 2 (macular telangiectasia type 2) is a bilateral neurodegenerative condition of the macula of the human eye which can lead to loss of
central vision. There is evidence that metabolic dysfunction leads to slow degeneration
of the retinal neuroglia, eventually leading to circumscribed loss of neuronal
tissue (photoreceptor atrophy). A characteristic feature of macular telangiectasia
type 2 is the temporal epicenter where the disease typically begins, and its limitation
to a central oval shaped area of approximately five by ten degrees, called the
macular telangiectasia type 2 area. Knowledge about visual function of people
with macular telangiectasia type 2 was limited to visual acuity testing, investigations
of reading performance, visual field testing with fundus-controlled perimetry
(microperimetry), and scotopic perimetry (not fundus-controlled). This thesis summarises
research aimed at exploring visual function in macular telangiectasia type 2
in more detail. In particular, visual acuity and reading performance are investigated
in more detail, the (para)central scotomas are better characterised, and visual function
in low light is elucidated by testing contrast sensitivity, low luminance visual
acuity and dark-adapted microperimetry. Visual acuity data was collected as part
of the international research collaboration The macular telangiectasia type 2 study,
which started in 2005 and has since then accrued data of more than 3000 individuals
with macular telangiectasia type 2. It was taken with Early Treatment of Diabetic
Retinopathy Study (ETDRS) charts on a harmonised protocol. Distribution of visual
acuity in the entire study cohort was investigated and eyes with low visual
acuity were looked at in detail. It was found that only about half of eyes with very
poor visual acuity showed evidence of neovascularisations, until recently still considered disease end stage, but nearly all eyes showed photoreceptor atrophy, which
is therefore more likely to define the disease end stage. Scotomas were characterised
further on retrospective analysis of microperimetry examinations from four
large centers of the macular telangiectasia type 2 study. This analysis confirmed
previous data which suggested mono-focality of the scotomas and the limitation to
a specific size. Further microperimetry assessment was performed with a recently
introduced new technology, allowing dark-adapted microperimetry with two wavelengths,
aiding differentiation of cone and rod dysfunction. This test showed more
general sensitivity reduction for blue light under low light conditions. This may
be in keeping with the findings from contrast sensitivity testing in mesopic light
conditions, showing strong impairment already in early disease stages, possibly indicating
inner retinal dysfunction rather than photoreceptor dysfunction in those
disease stages. Reading performance and the effect of binocularity was measured
with Radner Reading charts. Reading was consistently slower when patients were
using both eyes, strongly indicating binocular inhibition, in particular when arising
from scotomas in left eyes. Based on the above, the findings resulted in new insights
into visual function with implications on our understanding of the condition.
Understanding visual impairment not only helps patient counselling, but also helps
driving directions of future research
Validation of automated artificial intelligence segmentation of optical coherence tomography images
PURPOSE
To benchmark the human and machine performance of spectral-domain (SD) and swept-source (SS) optical coherence tomography (OCT) image segmentation, i.e., pixel-wise classification, for the compartments vitreous, retina, choroid, sclera.
METHODS
A convolutional neural network (CNN) was trained on OCT B-scan images annotated by a senior ground truth expert retina specialist to segment the posterior eye compartments. Independent benchmark data sets (30 SDOCT and 30 SSOCT) were manually segmented by three classes of graders with varying levels of ophthalmic proficiencies. Nine graders contributed to benchmark an additional 60 images in three consecutive runs. Inter-human and intra-human class agreement was measured and compared to the CNN results.
RESULTS
The CNN training data consisted of a total of 6210 manually segmented images derived from 2070 B-scans (1046 SDOCT and 1024 SSOCT; 630 C-Scans). The CNN segmentation revealed a high agreement with all grader groups. For all compartments and groups, the mean Intersection over Union (IOU) score of CNN compartmentalization versus group graders' compartmentalization was higher than the mean score for intra-grader group comparison.
CONCLUSION
The proposed deep learning segmentation algorithm (CNN) for automated eye compartment segmentation in OCT B-scans (SDOCT and SSOCT) is on par with manual segmentations by human graders
Safety and Feasibility of a Novel Sparse Optical Coherence Tomography Device for Patient-Delivered Retina Home Monitoring
Purpose To study a novel and fast optical coherence tomography (OCT) device for home-based monitoring in age-related macular degeneration (AMD) in a small sample yielding sparse OCT (spOCT) data and to compare the device to a commercially available reference device.
Methods In this prospective study, both eyes of 31 participants with AMD were included. The subjects underwent scanning with an OCT prototype and a spectral-domain OCT to compare the accuracy of the central retinal thickness (CRT) measurements.
Results Sixty-two eyes in 31 participants (21 females and 10 males) were included. The mean age was 79.6 years (age range, 69-92 years). The mean difference in the CRT measurements between the devices was 4.52 μm (SD ± 20.0 μm; range, -65.6 to 41.5 μm). The inter- and intrarater reliability coefficients of the OCT prototype were both >0.95. The laser power delivered was <0.54 mW for spOCT and <1.4 mW for SDOCT. No adverse events were reported, and the visual acuity before and after the measurements was stable.
Conclusion This study demonstrated the safety and feasibility of this home-based OCT monitoring under real-life conditions, and it provided evidence for the potential clinical benefit of the device.
Translational Relevance The newly developed spOCT is a valid and readily available retina scanner. It could be applied as a portable self-measuring OCT system. Its use may facilitate the sustainable monitoring of chronic retinal diseases by providing easily accessible and continuous retinal monitoring
A Novel Role for Corneal Pachymetry in Planning Cataract Surgery by Determining Changes in Spherical Equivalent Resulting from a Previous LASIK Treatment
Objectives. To provide a metric to differentiate between hyperopic and myopic ablation of a prior LASIK treatment based on the corneal pachymetry profile after laser vision correction (LVC). Methods. Pachymetry data were retrospectively recovered from patients who had previous LASIK for refractive purposes between 2019 and 2020. Patients with any corneal disorder were excluded. Ablation spherical equivalent was predicted from the central to semiperipheral corneal thickness (CPT) ratio, both values were provided by using the Pentacam user interface software (UI), and values were computed from extracted raw pachymetry data. Results. Data of 157 eyes of 81 patients were collected, of which data were analysed for 73 eyes of 73 patients to avoid concurrence of measurements in both eyes per subject (42% female; mean age 40.9; SD 12.8). The CPT ratio cutoff for distinction between myopic and hyperopic LASIK was 0.86 for Pentacam UI data. Sensitivity and specificity were 0.7 and 0.95, respectively. Accuracy increased with computation of the CPT ratio based on extracted raw data with sensitivity and specificity of 0.87 and 0.99, respectively. There was a marked linear correlation between the CPT ratio and the ablation spherical equivalent (R2 = 0.93). Conclusions. CPT ratio cutoffs can correctly classify if a cornea previously had a hyperopic versus myopic LASIK surgery and estimate the ablation spherical equivalent of such treatment. This could prove useful for increased accuracy of intraocular lens (IOL) calculations for patients with no historical data of their prior LVC surgery at the time of cataract surgery planning
Macular telangiectasia type 2
AbstractMacular telangiectasia type 2 is a bilateral disease of unknown cause with characteristic alterations of the macular capillary network and neurosensory atrophy. Its prevalence may be underestimated and has recently been shown to be as high as 0.1% in persons 40 years and older. Biomicroscopy may show reduced retinal transparency, crystalline deposits, mildly ectatic capillaries, blunted venules, retinal pigment plaques, foveal atrophy, and neovascular complexes. Fluorescein angiography shows telangiectatic capillaries predominantly temporal to the foveola in the early phase and a diffuse hyperfluorescence in the late phase. High-resolution optical coherence tomography (OCT) may reveal disruption of the photoreceptor inner segment–outer segment border, hyporeflective cavities at the level of the inner or outer retina, and atrophy of the retina in later stages. Macular telangiectasia type 2 shows a unique depletion of the macular pigment in the central retina and recent therapeutic trials showed that such depleted areas cannot re-accumulate lutein and zeaxanthin after oral supplementation. There have been various therapeutic approaches with limited or no efficacy. Recent clinical trials with compounds that block vascular endothelial growth factor (VEGF) have established the role of VEGF in the pathophysiology of the disease, but have not shown significant efficacy, at least for the non-neovascular disease stages. Recent progress in structure–function correlation may help to develop surrogate outcome measures for future clinical trials.In this review article, we summarize the current knowledge on macular telangiectasia type 2, including the epidemiology, the genetics, the clinical findings, the staging and the differential diagnosis of the disease. Findings using retinal imaging are discussed, including fluorescein angiography, OCT, adaptive optics imaging, confocal scanning laser ophthalmoscopy, and fundus autofluorescence, as are the findings using visual function testing including visual acuity and fundus-controlled microperimetry. We provide an overview of the therapeutic approaches for both non-neovascular and neovascular disease stages and provide a perspective of future directions including animal models and potential therapeutic approaches
Pentaerythritol Tetranitrate In Vivo Treatment Improves Oxidative Stress and Vascular Dysfunction by Suppression of Endothelin-1 Signaling in Monocrotaline-Induced Pulmonary Hypertension
Objective. Oxidative stress and endothelial dysfunction contribute to pulmonary arterial hypertension (PAH). The role of the nitrovasodilator pentaerythritol tetranitrate (PETN) on endothelial function and oxidative stress in PAH has not yet been defined. Methods and Results. PAH was induced by monocrotaline (MCT, i.v.) in Wistar rats. Low (30 mg/kg; MCT30), middle (40 mg/kg; MCT40), or high (60 mg/kg; MCT60) dose of MCT for 14, 28, and 42 d was used. MCT induced endothelial dysfunction, pulmonary vascular wall thickening, and fibrosis, as well as protein tyrosine nitration. Pulmonary arterial pressure and heart/body and lung/body weight ratio were increased in MCT40 rats (28 d) and reduced by oral PETN (10 mg/kg, 24 d) therapy. Oxidative stress in the vascular wall, in the heart, and in whole blood as well as vascular endothelin-1 signaling was increased in MCT40-treated rats and normalized by PETN therapy, likely by upregulation of heme oxygenase-1 (HO-1). PETN therapy improved endothelium-dependent relaxation in pulmonary arteries and inhibited endothelin-1-induced oxidative burst in whole blood and the expression of adhesion molecule (ICAM-1) in endothelial cells. Conclusion. MCT-induced PAH impairs endothelial function (aorta and pulmonary arteries) and increases oxidative stress whereas PETN markedly attenuates these adverse effects. Thus, PETN therapy improves pulmonary hypertension beyond its known cardiac preload reducing ability