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Toxins in Neuro-Ophthalmology
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Toxic optic neuropathy present as bilateral, symmetrical painless, progressive visual loss. Change in color perception (dyschromatopsia) is often the first symptom among the many. Visual acuity disturbance may start with a blur at fixation point, i.e., relative scotoma followed by a progressive decline [7]. Examination usually shows normal light and accommodation reflex except in those who are blind. On fundoscopy, disc may appear normal, swollen or hyperemic in early stage, while in later stages, optic atrophy may ensue. Visual field testing usually reveals centrocecal scotoma.
Cranial nerves
Published in Ian Mann, Alastair Noyce, The Finalist’s Guide to Passing the OSCE, 2021
Demonstrate the accommodation reflex. Again, ask the patient to look into the distance. Bring your finger into the midline, approximately 10 cm from the patient’s nose. Ask them to fix on your finger, and observe for convergence and pupil constriction.
History-taking model
Published in Kaji Sritharan, Vivian A Elwell, Sachi Sivananthan, Essential OSCE Topics for Medical and Surgical Finals, 2007
Kaji Sritharan, Vivian A Elwell, Sachi Sivananthan
InspectionEyelids: look for ptosis, lid retraction, entropion (lids turned in), ectropion (lids turned out) and styes.Conjunctiva: look for conjunctivitis, chemosis and pallor.Sclera: look for yellow colour (jaundice), blue colour (iron-deficiency anaemia, osteogenesis imperfecta) or inflammation.Cornea: look for corneal arcus (hypercholesterolaemia) and Kayser-Fleischer ring (Wilson’s disease).Iris: look for iritis.Pupils: may be miotic (constricted) or mydriatric (dilated). Test direct and consensual light reflex, and accommodation reflex.Ocular movements: test movements in all positions of gaze. Both eyes should move symmetrically.
COVID-19 and the Eye: Ocular Manifestations, Treatment and Protection Measures
Published in Ocular Immunology and Inflammation, 2021
In central retinal artery occlusion secondary to COVID-19 disease, sudden onset of painless loss of vision occurs. The pupil is unresponsive to light, and the accommodation reflex is absent. Emergent non-contrast computed tomographic images of the head and angiography are unremarkable for any acute infarct or blood clot. The optic nerve has slightly indistinct margins, and a cherry red spot with significant retinal whitening confirms the diagnosis of central retinal artery occlusion.64 In COVID-19 patients, tortuosity and dilatation of all branches of the central retinal vein, dot, blot and flame-shaped hemorrhages throughout all quadrants, and optic disc edema are the findings of central retinal vein occlusion.65Table 2 summarizes the retinal manifestations during the COVID-19 pandemic.
Amplitude of Accommodation in Patients with Multiple Sclerosis
Published in Current Eye Research, 2019
Bekir Küçük, Mehmet Hamamcı, Seray Aslan Bayhan, Hasan Ali Bayhan, Levent Ertuğrul Inan
The dysfunction of the accommodation reflex may also be caused by the effect on the posterior visual pathway. Optic radiation lesions, in particular, are very common in patients with MS, due to their periventricular location.62,63 Not all defects may exhibit clinical symptoms63; even so, small lesions can affect some visual parameters, such as AA. Another component of the accommodation reflex pathway is the visual cortex. Visual cortex involvement is controversial64-66; however, Jenkins et al. demonstrated significant occipital cortex atrophy in early stages of MS.64 Therefore, the lesions in the visual cortex may be caused by the reduction of AA in patients with MS.
‘The role of accommodative function in myopic development: A review.’
Published in Seminars in Ophthalmology, 2022
Efthymia Prousali, Anna-Bettina Haidich, Argyrios Tzamalis, Nikolaos Ziakas, Asimina Mataftsi
Accommodation comprises the mechanism through which the eye is able to alter the refractive power of the crystalline lens so as to preserve a clear illustration of a near target upon the retina. Accommodation, convergence and pupillary constriction comprise the accommodation reflex, an essential response for proper near vision coordination.6 A blurred image owing to hyperopic retinal defocus is believed to drive accommodation, which is mainly controlled via the parasympathetic system. The accommodative response is achieved through bilateral contraction of the ciliary muscle, with resultant changes in its morphology. The ciliary muscle is comprised, anteroposteriorly, of longitudinal, radial and circular fibres, which contract as a whole when the eye accommodates. In particular, accommodation is believed to induce thickening of the anterior ciliary muscle portion and thinning posteriorly, leading to a forward and inward displacement of the ciliary body and a change in lens shape, which becomes thicker. These phenomena result in extension and thinning of the choroid, which modifies its thickness so as to meet the plane of focus of the eye. Owing to proximity, changes in the choroid are strongly associated with regulation of scleral remodelling and metabolism and, as a result, with ocular growth.5 During accommodation, the anterior temporal sclera demonstrates thinning, which is more evident in myopic eyes, as depicted using anterior segment OCT.7 A thinner, more extensile sclera due to biochemical changes including proteoglycan synthesis, collagen and/or matrix metalloproteinase activity is believed to prompt axial elongation.8–10 Of note, Wagner et al. proposed that crystalline lens changes could exert a greater effect compared to ciliary muscle changes in the accommodative response.11 Also, the changes in lens shape and the resulting increase in ocular refractive power due to accommodation lead to changes in the aberrations experienced, particularly the high-order aberrations, while chromatic aberrations appear to have limited involvement.12