Impairments of object recognition are core features of neurodegenerative syndromes, in particular posterior cortical atrophy (PCA; the \'visual-variant Alzheimer\'s disease\'). These impairments arise from damage to higher-level cortical visual regions and are often missed or misattributed to common ophthalmological conditions. Consequently, diagnosis can be delayed for years with considerable implications for patients. We report a new test for the rapid measurement of cortical visual loss - the Graded Incomplete Letters Test (GILT). The GILT is an optimised psychophysical variation of a test used to diagnose cortical visual impairment, which measures thresholds for recognising letters under levels of increasing visual degradation (decreasing \"completeness\") in a similar fashion to ophthalmic tests. The GILT was administered to UK Biobank participants (total n=2,359) and participants with neurodegenerative conditions characterised by initial cortical visual (PCA, n=18) or memory loss (typical Alzheimer\'s disease, n=9). UK Biobank participants, including both typical adults and those with ophthalmological conditions, were able to recognise letters under low levels of completeness. In contrast, participants with PCA consistently made errors with only modest decreases in completeness. GILT sensitivity to PCA was 83.3% for participants reaching the 80% accuracy cut-off, increasing to 88.9% using alternative cut-offs (60% or 100% accuracy). Specificity values were consistently over 94% when compared to UK Biobank participants without or with documented visual conditions, regardless of accuracy cut-off. These first-release UK Biobank and clinical verification data suggest the GILT has utility in both rapidly detecting visual perceptual losses following posterior cortical damage and differentiating perceptual losses from common eye-related conditions.

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End-stage age-related macular degeneration (AMD) and retinitis pigmentosa (RP) are two major retinal degenerative (RD) conditions that result in irreversible vision loss. Permanent eye damage can also occur in battlefields or due to accidents. This suggests there is an unmet need for developing effective strategies for treating permanent retinal damages. In previous studies, co-grafted sheets of fetal retina with its retinal pigment epithelium (RPE) have demonstrated vision improvement in rat retinal disease models and in patients, but this has not yet been attempted with stem-cell derived tissue. Here we demonstrate a cellular therapy for irreversible retinal eye injuries using a \"total retina patch\" consisting of retinal photoreceptor progenitor sheets and healthy RPE cells on an artificial Bruch\'s membrane (BM). For this, retina organoids (ROs) (cultured in suspension) and polarized RPE sheets (cultured on an ultrathin parylene substrate) were made into a co-graft using bio-adhesives [gelatin, growth factor-reduced matrigel, and medium viscosity (MVG) alginate]. In vivo transplantation experiments were conducted in immunodeficient Royal College of Surgeons (RCS) rats at advanced stages of retinal degeneration. Structural reconstruction of the severely damaged retina was observed based on histological assessments and optical coherence tomography (OCT) imaging. Visual functional assessments were conducted by optokinetic behavioral testing and superior colliculus electrophysiology. Long-term survival of the co-graft in the rat subretinal space and improvement in visual function were observed. Immunohistochemistry showed that co-grafts grew, generated new photoreceptors and developed neuronal processes that were integrated into the host retina. This novel approach can be considered as a new therapy for complete replacement of a degenerated retina.

OBJECTIVE: The recent pandemic has identified the need for telemedicine assessment of ophthalmology patients. A vital component of such assessment is visual acuity (VA) measurement. The aim of this study was to determine the feasibility and reliability of computerised \'at home\' VA measurements using COMPlog software.
METHODS: A Bland Altman method comparison study of worse eye \'in clinic\' and \'at home\' orthoptist-supervised COMPlog computerised VA measurements. Subjects underwent gold standard semi-automated computerised test and retest logMAR VA measurements on their habitually corrected worse eye both \'in clinic\' and \'at home.\' The orthoptist ran the test from the eye clinic with the patient viewing a secondary PC monitor either in the same clinic room or at home. A screen sharing voice and video conferencing application and standard consumer IT hardware were employed to present the test optotypes in the patient\'s home.
RESULTS: 23 paediatric and 13 adult patients with a range of ocular diseases and worse eye visual acuities were included (range -0.14 to 1.06 logMAR). No significant bias was found between \'in clinic\' and \'at home\' measurements (mean -0.01 logMAR and 95% confidence interval -0.03, 0.00 logMAR). Test-retest variability of \'in clinic,\' \'at home\' and \'in clinic\' versus \'at home\' measurements were within normal reported ranges at 0.12 logMAR (6 ETDRS letters) or less.
CONCLUSIONS: Remote home VA testing performed by an eye care professional using a semi-automated VA measurement program and video conferencing application provided unbiased measurements with acceptable test-retest reliability. Home testing was both feasible and acceptably reliable in appropriately equipped patients.

UNASSIGNED: The Covid-19 pandemic necessitated social distancing restrictions, which placed limitations on access to ophthalmic care to only those who had an imminent risk of sight loss. All other face-to-face consultations were converted to telephone consultations or were postponed. We investigated whether parents were able to test their child\'s vision using available home vision testing applications, with an aim to aid decision making during a telephone consultation.
UNASSIGNED: Families with follow-up consultations at Birmingham Children\'s Hospital were asked to test their child\'s vision at home. Instructions for the use of Peek acuity, or iSight Pro, were emailed to a parent. Parents chose to use a particular app based on available devices at home. Parents were asked to test uniocular visual acuity twice. Home versus hospital acuity was correlated. Home acuity test-retest reliability was acquired. Parental feedback was obtained through questionnaires.
UNASSIGNED: One hundred and three families were contacted, 15 families completed home vision testing. Ten families used Peek acuity, five families used iSight Pro. Uniocular visual acuity test-retest reliability was 0.03 LogMAR. Home-hospital acuity testing had a bias of 0.14 LogMAR, hospital acuity yielding a lower LogMAR score. Most families who completed testing found it easy to do; however, some struggled, and 81 families did not undertake home vision testing.
UNASSIGNED: Uptake of home vision testing was limited by parental engagement, most likely influenced by the current pandemic. Most families who undertook home vision testing were able to generate results that could be used for clinical decision making. Extending the impact of parental vision testing will require education by clinicians and further study to increase sample sizes and to improve confidence.

Vision is a vital attribute to foraging, navigation, mate selection and social signalling in animals, which often have a very different colour perception in comparison to humans. For understanding how animal colour perception works, vision models provide the smallest colour difference that animals of a given species are assumed to detect. To determine the just-noticeable-difference, or JND, vision models use Weber fractions that set discrimination thresholds of a stimulus compared to its background. However, although vision models are widely used, they rely on assumptions of Weber fractions since the exact fractions are unknown for most species. Here, we test; i) which Weber fractions in long-, middle- and shortwave (i.e. L, M, S) colour channels best describe the blue tit (Cyanistes caeruleus) colour discrimination, ii) how changes in hue of saturated colours and iii) chromatic background noise impair search behaviour in blue tits. We show that the behaviourally verified Weber fractions on achromatic backgrounds were L: 0.05, M: 0.03 and S: 0.03, indicating a high colour sensitivity. In contrast, on saturated chromatic backgrounds, the correct Weber fractions were considerably higher for L: 0.20, M: 0.17 and S: 0.15, indicating a less detailed colour perception. Chromatic complexity of backgrounds affected the longwave channel, while middle- and shortwave channels were mostly unaffected. We caution that using a vision model whereby colour discrimination is determined in achromatic viewing conditions, as they often are, can lead to misleading interpretations of biological interactions in natural - colourful - environments.

OBJECTIVE: The objective of this study was to identify and validate smartphone-based visual acuity (VA) apps that can be used in a teleophthalmology portal.
METHODS: The study was conducted in three phases: A survey to investigate if the SmartOptometry App was easy to download, understand and test (phase I), an in-clinic comparison of VA measured in a random testing order with four tools namely COMPlog, Reduced Snellen near vision, Peek Acuity (Distance VA) and SmartOptometry (Near VA) (phase II) and a repeatability study on these 4 tools by measuring VA again (phase III). The study recruited the employees of our institute and adhered to the strict COVID-19 protocols of testing.
RESULTS: Phase I Survey (n = 40) showed 90% of participants used android phones, 60% reported that instructions were clear, and all users were able to self-assess their near VA with SmartOptometry App. Phase II (n = 68) revealed that Peek Acuity was comparable to COMPlog VA (P = 0.31), however SmartOptometry was statistically significantly different (within 2 log MAR lines) from Reduced Snellen near vision test, particularly for young (n = 44, P = 0.004) and emmetropic (n = 16, P = 0.04) participants. All the 4 tests were found to be repeatable in phase III (n = 10) with a coefficient of repeatability ≤0.14.
CONCLUSIONS: Smartphone-based apps were easy to download and can be used for checking patient\'s distance and near visual acuity. An effect of age and refractive error should be considered when interpreting the results. Further studies with real-time patients are required to identify potential benefits and challenges to solve.

BACKGROUND: Visual acuity (VA) testing is a vital screening tool for the assessment of ocular function. The coronavirus 2019 pandemic has caused an immediate need for synchronous telemedicine in all specialties, including ophthalmology. While a plethora of mobile VA applications exist, there is no consensus as to what technology can accurately and reproducibly measure a patient\'s vision at home.
METHODS: A systematic literature search was performed in April 2020 using PubMed, Embase and Medline, identifying English publications from 2010 to 2020 on remote VA tests: 4338 articles were identified and 14 were ultimately included in the review.
RESULTS: Of those 14, the highest quality studies, best reproducibility and correlation with in-clinic acuities measured were found using the Peek Acuity application. The studies included patients throughout the world aged 3-97, with and without correction, with known ocular pathology.The Peek Acuity studies measured distance vision on a Samsung Galaxy S3 with a mean difference of 0.055 Logarithm of the Minimum Angle of Resolution (LogMAR) for home testing compared with the Early Treatment Diabetic Retinopathy Study (ETDRS). Test-retest variability was ±0.029 LogMAR for 95% confidence interval limits.
CONCLUSIONS: There can be one or more lines of variability in vision testing in a clinical setting using reference standard ETDRS and clinical standard Snellen charts. Test-retest reliability is not perfect even on standard clinical charts (variation up to 0.48 LogMAR). Of the technologies reviewed, Peek Acuity home testing had the greatest correlation with ETDRS clinical vision and high test-retest reliability. Peek Acuity performed no worse than Snellen and ETDRS charts.

Determine the repeatability of and optimum stimulus parameters for testing polarization pattern perception in a real-world clinical population, and assess the ability of polarization perception to distinguish normal from abnormal eyes.
Polarization perception was evaluated in staff and patients attending ophthalmology clinics at Warwick Hospital, UK. A series of visual stimuli were presented in pseudorandom order using a liquid-crystal-display-based polarization pattern generator. Stimuli included geometric patterns, gratings, checkerboards, and optotypes. Participants had one or both eyes diagnosed as normal or abnormal following ophthalmic examination, optical coherence tomography, and measures of visual acuity. Measurement scores were assigned to the eye(s) of each participant depending on the total number of stimuli perceived or identified.
Stimuli covered the range of spatial scales resolvable within polarization perception by normal and abnormal eyes. Different stimuli had different saliencies. For each stimulus type, polarization perception in the abnormal group was significantly reduced compared with normal eyes (P < 0.001). Relative stimulus salience was broadly similar for normal-eye and abnormal-eye viewing groups, being greatest for radially symmetric patterns and least for optotypes. Checkerboard pattern salience had an inverse logarithmic relationship with check fundamental spatial frequency. A devised metric covering the dynamic range of polarization perception was repeatable, and the score derived from the metric was reduced in the abnormal group compared with the normal group (P < 0.001).
Clinically useful metrics of polarization perception distinguish between normal and abnormal eyes.
Perception of spatial patterns formed of non-uniform polarization fields has potential as a quantitative clinical diagnostic measurement.

This study was designed to assess risk for retinal toxicity associated with administration of high-dose sildenafil citrate to dogs heterozygous for a functionally null mutation in Pde6a over a 4-month period. Three Pde6a +/- dogs were administered 14.3 mg/kg sildenafil per os and two Pde6a +/- dogs placebo once daily for 16 weeks. Three Pde6a +/+ dogs were administered sildenafil for 7 days. Ophthalmic examination, vision testing, and electroretinography (ERG) were regularly performed. At study termination, dogs were euthanized and globes collected. Retinal layer thickness and photoreceptor nuclei counts were determined from plastic sections. In both Pde6a +/- and Pde6a +/+ sildenafil-treated (ST) dogs, elevation of dark-adapted b-wave threshold and unmasking of the scotopic threshold response (STR) were observed. Sildenafil treated Pde6a +/- dogs had significantly thinner ONL (24.90 +/-1.88 μm, p = 0.004) and lower photoreceptor nuclei counts (273.6 +/- 29.3 cells/100 μm, p = 0.008) compared to measurements (35.90 +/- 1.63 μm) and counts (391.5 +/-27.0 cells/100 μm) from archived untreated Pde6a +/- dogs.