Vision Anatomy

This presentation is Lecture 2 in the PEER Liberia Neurology Lecture Series. It provides an overview of eye anatomy, vision testing, and diagnosis of eye conditions

Aortic arch tortuosity with PHACE syndrome : a rare case scenario

PHACE syndrome is a rare neurocutaneous disorder characterised by an association of infantile haemangiomas with structural anomalies of brain, cerebral vasculature, eye, aorta and chest wall.1 Coarctation of aorta (COA) is most the common cardiac anomaly reported in PHACE syndrome. COA or interrupted aortic arch in PHACE is unique and complex both in location and character compared to the typical coarctation anatomy. Arterial tortuosity of the cerebral vasculature has been well described in literature in PHACE syndrome. We present a rare case of tortuous aortic arch continuing as descending aorta in an infant with PHACE syndrome.peer-reviewe

A medieval fallacy: the crystalline lens in the center of the eye.

ObjectiveTo determine whether, as most modern historians have written, ancient Greco-Roman authors believed the crystalline lens is positioned in the center of the eye.BackgroundHistorians have written that statements about cataract couching by Celsus, or perhaps Galen of Pergamon, suggested a centrally located lens. Celsus specifically wrote that a couching needle placed intermediate between the corneal limbus and the lateral canthus enters an empty space, presumed to represent the posterior chamber.MethodsAncient ophthalmic literature was analyzed to understand where these authors believed the crystalline lens was positioned. In order to estimate where Celsus proposed entering the eye during couching, we prospectively measured the distance from the temporal corneal limbus to the lateral canthus in 30 healthy adults.ResultsRufus of Ephesus and Galen wrote that the lens is anterior enough to contact the iris. Galen wrote that the lens equator joins other ocular structures at the corneoscleral junction. In 30 subjects, half the distance from the temporal corneal limbus to the lateral canthus was a mean of 4.5 mm (range: 3.3-5.3 mm). Descriptions of couching by Celsus and others are consistent with pars plana entry of the couching needle. Anterior angulation of the needle would permit contact of the needle with the lens.ConclusionAncient descriptions of anatomy and couching do not establish the microanatomic relationships of the ciliary region with any modern degree of accuracy. Nonetheless, ancient authors, such as Galen and Rufus, clearly understood that the lens is located anteriorly. There is little reason to believe that Celsus or other ancient authors held a variant understanding of the anatomy of a healthy eye. The notion of the central location of the lens seems to have arisen with Arabic authors in 9th century Mesopotamia, and lasted for over 7 centuries

Contribution to the theory of photopic vision: Retinal phenomena

Principles of thermodynamics are applied to the study of the ultramicroscopic anatomy of the inner eye. Concepts introduced and discussed include: the retina as a three-dimensional sensor, light signals as coherent beams in relation to the dimensions of retinal pigments, pigment effects topographed by the conjugated antennas effect, visualizing lights, the autotropic function of hemoglobin and some cytochromes, and reversible structural arrangements during photopic adaptation. A paleoecological diagram is presented which traces the evolution of scotopic vision (primitive system) to photopic vision (secondary system) through the emergence of structures sensitive to the intensity, temperature, and wavelengths of the visible range

Microanatomy of Adult Zebrafish Extraocular Muscles

Binocular vision requires intricate control of eye movement to align overlapping visual fields for fusion in the visual cortex, and each eye is controlled by 6 extraocular muscles (EOMs). Disorders of EOMs are an important cause of symptomatic vision loss. Importantly, EOMs represent specialized skeletal muscles with distinct gene expression profile and susceptibility to neuromuscular disorders. We aim to investigate and describe the anatomy of adult zebrafish extraocular muscles (EOMs) to enable comparison with human EOM anatomy and facilitate the use of zebrafish as a model for EOM research. Using differential interference contrast (DIC), epifluorescence microscopy, and precise sectioning techniques, we evaluate the anatomy of zebrafish EOM origin, muscle course, and insertion on the eye. Immunofluorescence is used to identify components of tendons, basement membrane and neuromuscular junctions (NMJs), and to analyze myofiber characteristics. We find that adult zebrafish EOM insertions on the globe parallel the organization of human EOMs, including the close proximity of specific EOM insertions to one another. However, analysis of EOM origins reveals important differences between human and zebrafish, such as the common rostral origin of both oblique muscles and the caudal origin of the lateral rectus muscles. Thrombospondin 4 marks the EOM tendons in regions that are highly innervated, and laminin marks the basement membrane, enabling evaluation of myofiber size and distribution. The NMJs appear to include both en plaque and en grappe synapses, while NMJ density is much higher in EOMs than in somatic muscles. In conclusion, zebrafish and human EOM anatomy are generally homologous, supporting the use of zebrafish for studying EOM biology. However, anatomic differences exist, revealing divergent evolutionary pressures

Ocular ultrasonography focused on the posterior eye segment: what radiologists should know

Ocular B-mode ultrasonography (US) is an important adjuvant for the clinical assessment of a variety of ocular diseases. When ophthalmoscopy is not possible, mainly due to opacification of the transparent media (e.g., mature cataract or vitreous haemorrhage), US can guide the ophthalmologist in diagnosing disease and choosing treatment. The superficial location and cystic structure of the eye make US ideal for imaging of the eye. Moreover, dynamic study helps distinguish between various conditions that would otherwise be difficult to differentiate in some clinical setting, such as vitreous, retinal, and choroidal detachment. US is also good technique for detecting other pathologic conditions such as lens dislocation, vitreous haemorrhage, asteroid hyalosis, optic disc drusen, and tumors (e.g., choroidal melanoma, metastases, hemangioma). An understanding of the basic anatomy of the eye, the US technique, and common entities that affect the ocular globe will allow radiologists to offer this valuable imaging modality to patients and referring clinicians. This article focuses on the US anatomy and pathologic conditions that affect the posterior ocular segment

Phantoms in medicine: the case of ophthalmology

Physical and in-silico phantoms have revealed extremely useful in the development of new surgical techniques and medical devices and for training purposes. The fabrication of eye phantoms requires knowledge of anatomy and physical principles beyond the eye physiology and medical instruments used in the clinical scenario. After a proper definition of phantoms and the discussion about their classification, the present work reviews the various phantoms developed in ophthalmology, illustrating the rationale of their design

Eye and Orbital Anatomy in Metopic Synostosis

Background: Metopic synostosis patients have a high prevalence of orthoptic anomalies, including hyperopia, astigmatism, and amblyopia. We hypothesized altered orbital anatomy contributes to suboptimal visual outcomes by adversely affecting eye anatomy and growth from early life onward. Therefore, we aimed to investigate eye and orbital anatomy in metopic synostosis. Methods: We conducted a retrospective study in nonsyndromic metopic synostosis patients (n = 134, median age 0.43 years [IQR 0.45]) with nonsyndromic sagittal synostosis patients (n = 134, median age 0.27 years [IQR 0.23]) as controls. Primary analyses focused on eye dimensions (axial length, width, and globe height) and orbital dimensions, correcting for sex and age. Measurements were obtained from preoperative computed tomography scans. Results: Axial length and width in metopic synostosis patients did not differ from sagittal synostosis patients, but globe height was significantly smaller (P = 0.0002). Lateral wall interorbital length, lateral orbital wall length, anterior medial interorbital length, and maximal medial interorbital length were significantly smaller, and anterior vertical orbital height and maximal vertical orbital height were significantly larger (P &lt; 0.001). The central orbital axis and interorbital angle were significantly narrower, and medial-to-lateral orbital wall angle was wider (P &lt; 0.001). Conclusions: Metopic synostosis patients have more shallow, wider, and higher orbits. Eye dimensions are similar in sagittal synostosis patients, although globe height was smaller. Altered orbital and eye dimensions in metopic synostosis probably have a causal relation with an unknown order of development. How these dimensions relate to future orthoptic anomalies (eg, refractive error) needs further investigation.</p