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Biomedical Engineering Online May 2016Analysis of fast temporal changes on retinas has become an important part of diagnostic video-ophthalmology. It enables investigation of the hemodynamic processes in...
BACKGROUND
Analysis of fast temporal changes on retinas has become an important part of diagnostic video-ophthalmology. It enables investigation of the hemodynamic processes in retinal tissue, e.g. blood-vessel diameter changes as a result of blood-pressure variation, spontaneous venous pulsation influenced by intracranial-intraocular pressure difference, blood-volume changes as a result of changes in light reflection from retinal tissue, and blood flow using laser speckle contrast imaging. For such applications, image registration of the recorded sequence must be performed.
METHODS
Here we use a new non-mydriatic video-ophthalmoscope for simple and fast acquisition of low SNR retinal sequences. We introduce a novel, two-step approach for fast image registration. The phase correlation in the first stage removes large eye movements. Lucas-Kanade tracking in the second stage removes small eye movements. We propose robust adaptive selection of the tracking points, which is the most important part of tracking-based approaches. We also describe a method for quantitative evaluation of the registration results, based on vascular tree intensity profiles.
RESULTS
The achieved registration error evaluated on 23 sequences (5840 frames) is 0.78 ± 0.67 pixels inside the optic disc and 1.39 ± 0.63 pixels outside the optic disc. We compared the results with the commonly used approaches based on Lucas-Kanade tracking and scale-invariant feature transform, which achieved worse results.
CONCLUSION
The proposed method can efficiently correct particular frames of retinal sequences for shift and rotation. The registration results for each frame (shift in X and Y direction and eye rotation) can also be used for eye-movement evaluation during single-spot fixation tasks.
Topics: Algorithms; Eye Movements; Humans; Image Processing, Computer-Assisted; Ophthalmoscopes; Retina; Retinal Vessels; Signal-To-Noise Ratio; Videotape Recording
PubMed: 27206477
DOI: 10.1186/s12938-016-0191-0 -
Journal of Anatomy Apr 2005The retinal and cerebral microvasculatures share many morphological and physiological properties. Assessment of the cerebral microvasculature requires highly specialized... (Review)
Review
The retinal and cerebral microvasculatures share many morphological and physiological properties. Assessment of the cerebral microvasculature requires highly specialized and expensive techniques. The potential for using non-invasive clinical assessment of the retinal microvasculature as a marker of the state of the cerebrovasculature offers clear advantages, owing to the ease with which the retinal vasculature can be directly visualized in vivo and photographed due to its essential two-dimensional nature. The use of retinal digital image analysis is becoming increasingly common, and offers new techniques to analyse different aspects of retinal vascular topography, including retinal vascular widths, geometrical attributes at vessel bifurcations and vessel tracking. Being predominantly automated and objective, these techniques offer an exciting opportunity to study the potential to identify retinal microvascular abnormalities as markers of cerebrovascular pathology. In this review, we describe the anatomical and physiological homology between the retinal and cerebral microvasculatures. We review the evidence that retinal microvascular changes occur in cerebrovascular disease and review current retinal image analysis tools that may allow us to use different aspects of the retinal microvasculature as potential markers for the state of the cerebral microvasculature.
Topics: Aging; Blood-Brain Barrier; Blood-Retinal Barrier; Capillaries; Cerebrovascular Circulation; Cerebrovascular Disorders; Dementia; Diabetes Mellitus; Fundus Oculi; Humans; Hypertension; Image Processing, Computer-Assisted; Mass Screening; Ophthalmoscopes; Photography; Retinal Vessels
PubMed: 15817102
DOI: 10.1111/j.1469-7580.2005.00395.x -
Medicina 2015This study assessed optic disc size and cupping, using a commercially available ophthalmoscope, in order to show norms of these values for clinical practice. Subjects...
This study assessed optic disc size and cupping, using a commercially available ophthalmoscope, in order to show norms of these values for clinical practice. Subjects were office-workers referred from their respective workplaces for a routine medical examination, which included eye examination. The optic disc size was classified as small, medium or large, for having a diameter < 1.0, 1.0-1.5, or > 1.5 times (respectively) the diameter of the ophthalmoscope's selected light spot on the posterior pole. The cupping was classified as the ratio of the vertical cupping diameter and the vertical disc diameter on a relative decimal scale from 0.0 to 1.0.This study included 184 subjects with a mean age of 40.5 ± 9.5 years; 149 (81%) were males. Their mean ocular pressure was 12.4 ± 1.5 mmHg (range 10-17 mmHg). There was a high correlation between optic disc sizes and cupping in the right and left eyes (Pearson Correlation r = 0.866, p < 0.001); therefore, for simplicity only the data for right eyes are presented. According to our definition, the optic discs in these eyes comprised 27 (14.7%) small, 141 (76.6%) medium and 16 (8.7%) large. The small optic discs were rarely cupped, and the large optic discs were always cupped. Optic disc cupping greater than 0.7 was rarely found and should be suspect of glaucoma. Clinical doctors should be aware of this and refer those subjects with abnormal cupping to the specialist.
Topics: Adult; Age Factors; Aged; Eye; Female; Glaucoma; Humans; Intraocular Pressure; Male; Middle Aged; Ophthalmoscopes; Optic Disk; Organ Size
PubMed: 25637893
DOI: No ID Found -
Optometry and Vision Science : Official... May 2012To develop and test the application of an adaptive optics scanning laser ophthalmoscope (AOSLO) with eye tracking for high-resolution microperimetric testing. (Comparative Study)
Comparative Study
PURPOSE
To develop and test the application of an adaptive optics scanning laser ophthalmoscope (AOSLO) with eye tracking for high-resolution microperimetric testing.
METHODS
An AOSLO was used to conduct simultaneous high-resolution retinal imaging and visual function testing in six normal subjects. Visual sensitivity was measured at test locations between the fovea and 5.0° eccentricity via an increment threshold approach using a 40-trial, yes-no adaptive Bayesian staircase procedure (QUEST). A high-speed eye tracking algorithm enabled real-time video stabilization and the delivery of diffraction-limited Goldmann I-sized stimuli (diameter = 6.5 arc min = ∼32 μm; λ = 680 nm) to targeted retinal loci for 200 ms. Test locations were selected either manually by the examiner or automatically using Fourier-based image registration. Cone spacing was assessed at each test location and sensitivity was plotted against retinal eccentricity. Finally, a 4.2 arc min stimulus was used to probe the angioscotoma associated with a blood vessel located at 2.5° eccentricity.
RESULTS
Visual sensitivity decreases with eccentricity at a rate of -1.32 dB/deg (R = 0.60). The vertical and horizontal errors of the targeted stimulus delivery algorithm averaged 0.81 and 0.89 arc min (∼4 μm), respectively. Based on a predetermined exclusion criterion, the stimulus was successfully delivered to its targeted location in 90.1% of all trials. Automated recovery of test locations afforded the repeat testing of the same set of cones over a period of 3 months. Thresholds measured over a parafoveal blood vessel were 1.96 times higher (p < 0.05; one-tailed t-test) than those measured in directly adjacent retina.
CONCLUSIONS
AOSLO-based microperimetry has the potential to test visual sensitivity with fine retinotopic precision. Automated recovery of previously tested locations allows these measures to be tracked longitudinally. This approach can be implemented by researchers interested in establishing the functional correlates of photoreceptor mosaic structure in patients with retinal disease.
Topics: Adult; Equipment Design; Female; Humans; Male; Ophthalmoscopes; Optics and Photonics; Reference Values; Reproducibility of Results; Retina; Retinal Diseases; Visual Field Tests
PubMed: 22446720
DOI: 10.1097/OPX.0b013e3182512b98 -
Journal of Biomedical Optics Feb 2012A multifunctional line scanning ophthalmoscope (mLSO) was designed, constructed, and tested on human subjects. The mLSO could sequentially acquire wide-field, confocal,...
A multifunctional line scanning ophthalmoscope (mLSO) was designed, constructed, and tested on human subjects. The mLSO could sequentially acquire wide-field, confocal, near-infrared reflectance, fluorescein angiography (FA), and indocyanine green angiography (ICGA) retinal images. The system also included a retinal tracker (RT) and a photodynamic therapy laser treatment port. The mLSO was tested in a pilot clinical study on human subjects with and without retinal disease. The instrument exhibited robust retinal tracking and high-contrast line scanning imaging. The FA and ICGA angiograms showed a similar appearance of hyper- and hypo-pigmented disease features and a nearly equivalent resolution of fine capillaries compared to a commercial flood-illumination fundus imager. An mLSO-based platform will enable researchers and clinicians to image human and animal eyes with a variety of modalities and deliver therapeutic beams from a single automated interface. This approach has the potential to improve patient comfort and reduce imaging session times, allowing clinicians to better diagnose, plan, and conduct patient procedures with improved outcomes.
Topics: Angiography; Equipment Design; Equipment Failure Analysis; Humans; Microscopy, Confocal; Ophthalmoscopes; Reproducibility of Results; Retinal Artery; Retinal Diseases; Sensitivity and Specificity; Treatment Outcome
PubMed: 22463040
DOI: 10.1117/1.JBO.17.2.026008 -
Investigative Ophthalmology & Visual... Feb 2022To characterize the early structural and functional changes in the retinal microvasculature in response to hyperglycemia in the Ins2Akita mouse.
PURPOSE
To characterize the early structural and functional changes in the retinal microvasculature in response to hyperglycemia in the Ins2Akita mouse.
METHODS
A custom phase-contrast adaptive optics scanning light ophthalmoscope was used to image retinal capillaries of 9 Ins2Akita positive (hyperglycemic) and 9 Ins2Akita negative (euglycemic) mice from postnatal weeks 5 to 18. A 15 kHz point scan was used to image capillaries and measure red blood cell flux at biweekly intervals; measurements were performed manually. Retinal thickness and fundus photos were captured monthly using a commercial scanning laser ophthalmoscope/optical coherence tomography. Retinal thickness was calculated using a custom algorithm. Blood glucose and weight were tracked throughout the duration of the study.
RESULTS
Elevated blood glucose (>250 mg/dL) was observed at 4 to 5 weeks of age in Ins2Akita mice and remained elevated throughout the study, whereas euglycemic littermates maintained normal glucose levels. There was no significant difference in red blood cell flux, capillary anatomy, lumen diameter, or occurrence of stalled capillaries between hyperglycemic and euglycemic mice between postnatal weeks 5 and 18. Hyperglycemic mice had a thinner retina than euglycemic littermates (p < 0.001), but retinal thickness did not change with duration of hyperglycemia despite glucose levels that were more than twice times normal.
CONCLUSIONS
In early stages of hyperglycemia, retinal microvasculature structure (lumen diameter, capillary anatomy) and function (red blood cell flux, capillary perfusion) were not impaired despite 3 months of chronically elevated blood glucose. These findings suggest that hyperglycemia alone for 3 months does not alter capillary structure or function in profoundly hyperglycemic mice.
Topics: Animals; Blood Flow Velocity; Blood Glucose; Capillaries; Diabetic Retinopathy; Disease Models, Animal; Erythrocyte Count; Erythrocytes; Hyperglycemia; Male; Mice; Ophthalmoscopes; Retinal Vessels; Tomography, Optical Coherence
PubMed: 35138346
DOI: 10.1167/iovs.63.2.18 -
Canadian Journal of Ophthalmology.... Dec 2016
Topics: Aged, 80 and over; Calcium; Cataract; Crystallins; Female; Humans; Lens Cortex, Crystalline; Retinal Perforations; Slit Lamp; Vision Disorders
PubMed: 27938970
DOI: 10.1016/j.jcjo.2016.03.005 -
Ophthalmology and Therapy Dec 2020Despite advances in ophthalmic diagnostics, the direct ophthalmoscope remains a key clinical skill taught to medical students and is the tool of choice for retina...
Despite advances in ophthalmic diagnostics, the direct ophthalmoscope remains a key clinical skill taught to medical students and is the tool of choice for retina examination among non-ophthalmic physicians. However, in recent years viable alternatives have become available. The coronavirus disease 2019 (COVID-19) pandemic has forced a major re-thinking in medical education worldwide. In this commentary, we examined the current merits and limitations of the direct ophthalmoscope in both the clinical sense and in the context of infection control. Furthermore, we compared the direct ophthalmoscope with alternatives, including commercially available portable non-mydriatic fundus cameras, that would allow a change in focus during ophthalmic teaching. We concluded that the latter will better prepare our medical students for the age of telemedicine and deep-learning systems. While the COVID-19 pandemic will not be the sole reason for the 'death' of the direct ophthalmoscope, the global situation will inevitably serve to expedite long overdue changes in our teaching of ophthalmic skills to non-ophthalmic physicians.
PubMed: 32860621
DOI: 10.1007/s40123-020-00295-1 -
The Ocular Surface Apr 2017Conjunctival microvascular responses may be a surrogate metric of efferent neural pathway function innervating the ocular surface as changes in blood flow occur within...
PURPOSE
Conjunctival microvascular responses may be a surrogate metric of efferent neural pathway function innervating the ocular surface as changes in blood flow occur within seconds after a stimulus. As somatosensory dysfunction may partially underlie dry eye (DE), in this study we evaluate whether bulbar conjunctival microvascular alterations correlate with various aspects of DE.
METHODS
Fifty-six DE patients were prospectively recruited from a Veterans Affairs ophthalmology clinic over an 11-month period. DE symptoms and ocular pain were assessed along with DE signs. A novel functional slit lamp biomicroscope (FSLB) was used to image the temporal bulbar conjunctiva from the right eye before and after central corneal stimulation with an air puff. Blood flow velocities were measured and noninvasive microvascular perfusion maps (nMPMs) were created.
RESULTS
The bulbar blood flow velocity was 0.50 ± 0.15 mm/s at baseline and increased to 0.55 ± 0.17 mm/s after stimulation (P < 0.001); the average change in velocity was 0.05 ± 0.09. nMPMs values and venule diameter, on the other hand, did not significantly increase after stimulation (1.64 ± 0.004 at baseline, 1.65 ± 0.04 after stimulation, P = 0.22 and 22.13 ± 1.84 μm at baseline, 22.21 ± 2.04 μm after stimulation, P = 0.73, respectively). Baseline blood flow velocity positively associated with Schirmer scores (r = 0.40, P = 0.002). Those with higher self-rated wind hyperalgesia demonstrated less change in blood flow velocity (r = -0.268, P = 0.046) after air stimulation on the central cornea.
CONCLUSION
Conjunctival blood flow velocity, but not vessel diameter or complexity, increases after wind stimuli. Baseline flow positively correlated with Schirmer scores while change in flow negatively correlated with self-reported wind hyperalgesia.
Topics: Blood Flow Velocity; Conjunctiva; Cornea; Dry Eye Syndromes; Humans; Slit Lamp
PubMed: 28042094
DOI: 10.1016/j.jtos.2016.12.002 -
Journal of Diabetes Research 2022To investigate the applicability of deep learning image assessment software VeriSee DR to different color fundus cameras for the screening of diabetic retinopathy (DR).
AIMS
To investigate the applicability of deep learning image assessment software VeriSee DR to different color fundus cameras for the screening of diabetic retinopathy (DR).
METHODS
Color fundus images of diabetes patients taken with three different nonmydriatic fundus cameras, including 477 Topcon TRC-NW400, 459 Topcon TRC-NW8 series, and 471 Kowa nonmyd 8 series that were judged as "gradable" by one ophthalmologist were enrolled for validation. VeriSee DR was then used for the diagnosis of referable DR according to the International Clinical Diabetic Retinopathy Disease Severity Scale. Gradability, sensitivity, and specificity were calculated for each camera model.
RESULTS
All images (100%) from the three camera models were gradable for VeriSee DR. The sensitivity for diagnosing referable DR in the TRC-NW400, TRC-NW8, and non-myd 8 series was 89.3%, 94.6%, and 95.7%, respectively, while the specificity was 94.2%, 90.4%, and 89.3%, respectively. Neither the sensitivity nor the specificity differed significantly between these camera models and the original camera model used for VeriSee DR development ( = 0.40, = 0.065, respectively).
CONCLUSIONS
VeriSee DR was applicable to a variety of color fundus cameras with 100% agreement with ophthalmologists in terms of gradability and good sensitivity and specificity for the diagnosis of referable DR.
Topics: Adult; Artificial Intelligence; Chi-Square Distribution; Diabetes Mellitus; Diabetic Retinopathy; Female; Humans; Male; Middle Aged; Ophthalmoscopes; Reproducibility of Results; Software Design
PubMed: 35308093
DOI: 10.1155/2022/5779276