-
Developmental Biology Aug 2021The basic structure of the eye, which is crucial for visual function, is established during the embryonic process of optic cup morphogenesis. Molecular pathways of... (Review)
Review
The basic structure of the eye, which is crucial for visual function, is established during the embryonic process of optic cup morphogenesis. Molecular pathways of specification and patterning are integrated with spatially distinct cell and tissue shape changes to generate the eye, with discrete domains and structural features: retina and retinal pigment epithelium enwrap the lens, and the optic fissure occupies the ventral surface of the eye and optic stalk. Interest in the underlying cell biology of eye morphogenesis has led to a growing body of work, combining molecular genetics and imaging to quantify cellular processes such as adhesion and actomyosin activity. These studies reveal that intrinsic machinery and spatiotemporally specific extrinsic inputs collaborate to control dynamics of cell movements and morphologies. Here we consider recent advances in our understanding of eye morphogenesis, with a focus on the mechanics of eye formation throughout vertebrate systems, including insights and potential opportunities using organoids, which may provide a tractable system to test hypotheses from embryonic models.
Topics: Actomyosin; Animals; Cell Movement; Eye; Humans; Lens, Crystalline; Morphogenesis; Optic Disk; Organogenesis; Retina; Retinal Pigment Epithelium; Signal Transduction; Vertebrates
PubMed: 33811855
DOI: 10.1016/j.ydbio.2021.03.023 -
Neurology Aug 2022
Topics: Eye; Humans; Multiple Sclerosis; Optic Neuritis; Tomography, Optical Coherence
PubMed: 35618437
DOI: 10.1212/WNL.0000000000200903 -
Romanian Journal of Ophthalmology 2021Idiopathic intracranial hypertension (IIH) is a neuro-ophthalmological syndrome of unknown cause that can be vision-threatening, so an early diagnosis is crucial. We...
Idiopathic intracranial hypertension (IIH) is a neuro-ophthalmological syndrome of unknown cause that can be vision-threatening, so an early diagnosis is crucial. We reported a case of a 68-year-old asymptomatic male referred with a cataract in his right eye (OD). Best-corrected visual acuity (BCVA) was 70 letters (20/ 40) in the OD and 85 letters (20/ 20) in the left eye (OS). Ophthalmological examination revealed a significant nuclear cataract in the OD that explained the visual acuity. Fundus imaging showed a faint nasal margin elevation of the optic disc of both eyes (OU). Optical coherence tomography (OCT) revealed a sectorial retinal nerve fiber layer (RNFL) atrophy in the inferior quadrant in the OS. Nevertheless, visual field (VF) did not demonstrate defects. Neuroimaging was normal and examination of CSF revealed an opening pressure of 500 mmH2O. A diagnosis of IIH was confirmed and acetazolamide 250 mg twice daily was recommended. After 12 months of follow-up, RNFL thickness remained stable and VF did not confirm defects. A routine eye examination was the onset of IIH in our case. Thus, the ophthalmologist played a crucial role in the early diagnosis of this syndrome. Papilledema is usually a key criterion for IIH, so after its detection, exclusion diagnosis and treatment should be initiated in order to avoid permanent visual loss.
Topics: Aged; Humans; Male; Optic Disk; Papilledema; Pseudotumor Cerebri; Retinal Ganglion Cells; Tomography, Optical Coherence
PubMed: 34179586
DOI: 10.22336/rjo.2021.37 -
Contact Lens & Anterior Eye : the... Dec 2020While scleral lenses have been fitted using diagnostic lenses or impression moulding techniques for over a century, recent advances in anterior segment imaging such as... (Review)
Review
While scleral lenses have been fitted using diagnostic lenses or impression moulding techniques for over a century, recent advances in anterior segment imaging such as optical coherence tomography and corneo-scleral profilometry have significantly improved the current understanding of the anatomy of the anterior eye including the morphometry of the conjunctiva, sclera, and corneo-scleral junction, as well as the ocular surface shape and elevation. These technological advances in ocular imaging along with continual improvements and innovations in scleral lens design and manufacturing have led to a global increase in scleral lens prescribing. This review provides a comprehensive overview of the conjunctiva and sclera in the context of modern scleral lens practice, including anatomical variations in healthy and diseased eyes, the physiological impact of scleral lens wear, potential fitting challenges, and current approaches to lens modifications in order to minimise lens-induced complications and adverse ocular effects. Specific topics requiring further research are also discussed.
Topics: Conjunctiva; Contact Lenses; Humans; Prosthesis Fitting; Sclera; Tomography, Optical Coherence
PubMed: 32624363
DOI: 10.1016/j.clae.2020.06.005 -
Brain : a Journal of Neurology Jul 2020Mitochondrial failure and hypoxia are key contributors to multiple sclerosis pathophysiology. Importantly, improving mitochondrial function holds promise as a new... (Review)
Review
Mitochondrial failure and hypoxia are key contributors to multiple sclerosis pathophysiology. Importantly, improving mitochondrial function holds promise as a new therapeutic strategy in multiple sclerosis. Currently, studying mitochondrial changes in multiple sclerosis is hampered by a paucity of non-invasive techniques to investigate mitochondrial function of the CNS in vivo. It is against this backdrop that the anterior visual system provides new avenues for monitoring of mitochondrial changes. The retina and optic nerve are among the metabolically most active structures in the human body and are almost always affected to some degree in multiple sclerosis. Here, we provide an update on emerging technologies that have the potential to indirectly monitor changes of metabolism and mitochondrial function. We report on the promising work with optical coherence tomography, showing structural changes in outer retinal mitochondrial signal bands, and with optical coherence angiography, quantifying retinal perfusion at the microcapillary level. We show that adaptive optics scanning laser ophthalmoscopy can visualize live perfusion through microcapillaries and structural changes at the level of single photoreceptors and neurons. Advantages and limitations of these techniques are summarized with regard to future research into the pathology of the disease and as trial outcome measures.
Topics: Animals; Humans; Mitochondria; Multiple Sclerosis; Neuroimaging; Optic Nerve; Retina
PubMed: 32163545
DOI: 10.1093/brain/awaa049 -
Clinical & Experimental Optometry Jan 2020We live in a three-dimensional world and the human eye can focus images from a wide range of distances by adjusting the power of the eye's lens (accommodation).... (Review)
Review
We live in a three-dimensional world and the human eye can focus images from a wide range of distances by adjusting the power of the eye's lens (accommodation). Progressive senescent changes in the lens ultimately lead to a complete loss of this ability by about age 50, which then requires alternative strategies to generate high-quality retinal images for far and close viewing distances. This review paper highlights the biomimetic properties and underlying optical mechanisms of induced anisometropia, small apertures, dynamic lenses, and multi-optic lenses in ameliorating the visual consequences of presbyopia. Specifically, the advantages and consequences of non-liner neural summation leveraged in monovision treatments are reviewed. Additionally, the value of a small pupil is quantified, and the impact of pinhole pupil location and their effects on neural sensitivity are examined. Different strategies of generating multifocal optics are also examined, and specifically the interaction between ocular and contact or intraocular lens aberrations and their effect on resulting image quality are simulated. Interestingly, most of the novel strategies for aiding presbyopic and pseudophakic eyes (for example, monovision, multifocality, pinhole pupils) have emerged naturally via evolution in a range of species.
Topics: Accommodation, Ocular; Anisometropia; Contact Lenses; Eyeglasses; Humans; Optics and Photonics; Presbyopia; Pupil; Visual Acuity
PubMed: 31734940
DOI: 10.1111/cxo.12987 -
Journal of Neuro-ophthalmology : the... Mar 2022Although nonarteritic anterior ischemic optic neuropathy (NAION) is considered a disorder that primarily affects the optic nerve head, optical coherence tomography (OCT)...
BACKGROUND
Although nonarteritic anterior ischemic optic neuropathy (NAION) is considered a disorder that primarily affects the optic nerve head, optical coherence tomography (OCT) shows peripapillary and foveal subretinal fluid associated with optic disc swelling from NAION. We sought to further evaluate retinal and vitreous changes in patients with NAION.
METHODS
Patients diagnosed with NAION at the New England Eye Center between 2013 and 2017 were evaluated using OCT. The presence and distribution of subretinal fluid was analyzed. Evidence of other vitreoretinal changes, including vitreopapillary traction (VPT) and the presence of hyperreflective dots (HRD), were also determined.
RESULTS
Twenty-five eyes from 20 patients who presented within 4 weeks of symptom onset were assessed. Peripapillary subretinal fluid was seen in 16 eyes (64%). Of those eyes, the subretinal fluid extended into the macula in 4 eyes (16%). Visual acuity improved in 2 of 4 eyes after subfoveal fluid resolution. Intraretinal cysts located in the peripapillary region were seen in 8 eyes (32%), HRD were noted in 11 (44.0%). There was no evidence of VPT.
CONCLUSIONS
A substantial number of patients with NAION have subretinal fluid on OCT, consistent with prior reports. Resolution of subfoveal fluid may result in some recovery of visual acuity. Other retinal changes, such as intraretinal cysts and HRD, are present but have unclear implications. We did not find evidence of a primary role of VPT in the pathophysiology of NAION.
Topics: Cysts; Humans; Nerve Fibers; Optic Disk; Optic Neuropathy, Ischemic; Retinal Ganglion Cells; Tomography, Optical Coherence
PubMed: 34001734
DOI: 10.1097/WNO.0000000000001264 -
Asia-Pacific Journal of Ophthalmology...Structural and functional alterations in the microcirculation by systemic hypertension can cause significant organ damage at the eye, heart, brain, and kidneys. As the...
Structural and functional alterations in the microcirculation by systemic hypertension can cause significant organ damage at the eye, heart, brain, and kidneys. As the retina is the only tissue in the body that allows direct imaging of small vessels, the relationship of hypertensive retinopathy signs with development of disease states in other organs have been extensively studied; large-scale epidemiological studies using fundus photography and advanced semi-automated analysis software have reported the association of retinopathy signs with hypertensive end-organ damage includes the following: stroke, dementia, and coronary heart disease. Although yielding much useful information, the vessels assessed from fundus photographs remain limited to the larger retinal arterioles and venules, and abnormalities observed may not be that of the earliest changes. Newer imaging modalities such as optical coherence tomography angiography and adaptive optics technology, which allow a greater precision in the structural quantification of retinal vessels, including capillaries, may facilitate the assessment and management of these patients. The advent of deep learning technology has also augmented the utility of fundus photographs to help create diagnostic and risk stratification systems. Particularly, deep learning systems have been shown in several large studies to be able to predict multiple cardiovascular risk factors, major adverse cardiovascular events within 5 years, and presence of coronary artery calcium, from fundus photographs alone. In the future, combining deep learning systems with the imaging precision offered by optical coherence tomography angiography and adaptive optics could pave way for systems that are able to predict adverse clinical outcomes even more accurately.
Topics: Fluorescein Angiography; Fundus Oculi; Humans; Hypertension; Retina; Retinal Vessels; Tomography, Optical Coherence
PubMed: 35533334
DOI: 10.1097/APO.0000000000000509 -
Eye (London, England) Feb 2023The retina and the optic nerve are considered extensions of the central nervous system (CNS) and thus can serve as the window for evaluation of CNS disorders. Spectral... (Review)
Review
The retina and the optic nerve are considered extensions of the central nervous system (CNS) and thus can serve as the window for evaluation of CNS disorders. Spectral domain optical coherence tomography (OCT) allows for detailed evaluation of the retina and the optic nerve. OCT can non-invasively document changes in single retina layer thickness and structure due to neuronal and retinal glial cells (RGC) modifications in systemic and local inflammatory and neurodegenerative diseases. These can include evaluation of retinal nerve fibre layer and ganglion cell complex, hyper-reflective retinal spots (HRS, sign of activated microglial cells in the retina), subfoveal neuroretinal detachment, disorganization of the inner retinal layers (DRIL), thickness and integrity of the outer retinal layers and choroidal thickness. This review paper will report the most recent data on the use of OCT as a non invasive imaging biomarker for evaluation of the most common systemic neuroinflammatory and neurodegenerative/neurocognitive disorders in the adults and in paediatric population. In the adult population the main focus will be on diabetes mellitus, multiple sclerosis, optic neuromyelitis, neuromyelitis optica spectrum disorders, longitudinal extensive transverse myelitis, Alzheimer and Parkinson diseases, Amyotrophic lateral sclerosis, Huntington's disease and schizophrenia. In the paediatric population, demyelinating diseases, lysosomal storage diseases, Nieman Pick type C disease, hypoxic ischaemic encephalopathy, human immunodeficiency virus, leukodystrophies spinocerebellar ataxia will be addressed.
Topics: Adult; Humans; Child; Tomography, Optical Coherence; Retinal Ganglion Cells; Neuroinflammatory Diseases; Retina; Neuromyelitis Optica; Biomarkers
PubMed: 35428871
DOI: 10.1038/s41433-022-02056-9 -
Clinical & Experimental Optometry Jan 2020Our current understanding of emmetropisation and myopia development has evolved from decades of work in various animal models, including chicks, non-human primates, tree... (Review)
Review
Our current understanding of emmetropisation and myopia development has evolved from decades of work in various animal models, including chicks, non-human primates, tree shrews, guinea pigs, and mice. Extensive research on optical, biochemical, and environmental mechanisms contributing to refractive error development in animal models has provided insights into eye growth in humans. Importantly, animal models have taught us that eye growth is locally controlled within the eye, and can be influenced by the visual environment. This review will focus on information gained from animal studies regarding the role of optical mechanisms in guiding eye growth, and how these investigations have inspired studies in humans. We will first discuss how researchers came to understand that emmetropisation is guided by visual feedback, and how this can be manipulated by form-deprivation and lens-induced defocus to induce refractive errors in animal models. We will then discuss various aspects of accommodation that have been implicated in refractive error development, including accommodative microfluctuations and accommodative lag. Next, the impact of higher order aberrations and peripheral defocus will be discussed. Lastly, recent evidence suggesting that the spectral and temporal properties of light influence eye growth, and how this might be leveraged to treat myopia in children, will be presented. Taken together, these findings from animal models have significantly advanced our knowledge about the optical mechanisms contributing to eye growth in humans, and will continue to contribute to the development of novel and effective treatment options for slowing myopia progression in children.
Topics: Accommodation, Ocular; Animals; Emmetropia; Eye; Humans; Models, Animal; Myopia; Optics and Photonics; Refraction, Ocular
PubMed: 31742789
DOI: 10.1111/cxo.12991