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Chronic Fatigue Syndrome: Limbic Encephalopathy in a Dysregulated Neuroimmune Network
Published in Jay A. Goldstein, Chronic Fatigue Syndromes, 2020
As has been mentioned previously, disturbances in visual acuity are common in CFS. They include problems with accommodation causing intermittent blurred vision and photophobia, probably due to ciliary muscle spasm since it is treatable with ocular prostaglandin inhibitors. The common complaint of oscillopsia could be due to brain stem dysfunction, since subtle nystagmus is sometimes seen, or may be related to difficulty with fixation, which could produce the phenomenon of lines of print jumping around while reading. Most of these visual disturbances are caused by autonomic dysfunction, perhaps again secondary to limbic-hypothalamic dys-regulation. Neuro-ophthalmologic exam is usually normal, although nystagmus has been reported in 27% of patients in one series.49
The Parts of the Eye Affected
Published in John William Yee, The Neurological Treatment for Nearsightedness and Related Vision Problems, 2019
The ciliary muscle is a ring circling the lens. It is attached to the crystalline lens by zonule fibers. Refer to the cross sectional diagram in Figure 2.5. It controls the shape of the crystalline lens. When the ciliary muscle relaxes, it recedes. The fibers become taut and pull on the lens to flatten it for distant focusing. When the muscle becomes tense, it thickens. It is like how your biceps expand when you flex them. The fibers become loose. The slack allows the lens to assume its normal round shape for near focusing. When myopia sets in, the ciliary muscle responds to the excessive tension of the oblique muscles by also becoming tense to entice the lens to bulge.
Anatomy and Physiology of the Autonomic Nervous System
Published in Kenneth J. Broadley, Autonomic Pharmacology, 2017
The preganglionic parasympathetic fibres synapse in ganglia, which unlike sympathetic ganglia lie very close to or within the organ that they innervate. The postganglionic parasympathetic fibres are therefore short and non-myelenated. Often the cell bodies of the postganglionic neurones are distributed throughout the tissue so that no discrete ganglia occur but instead they form a network of interconnecting fibres known as a plexus. For example, the cardiac ganglia of the vagus nerve form a plexus around the great vessels or in the atrial wall which give rise to the postganglionic fibres to the heart. Also running through this plexus are sympathetic postganglionic fibres and sensory afferents. The vagus nerve also contains somatic motor fibres which innervate the striated muscle of the pharynx and larynx, which controls swallowing. The ciliary ganglion lies behind the eyeball, receiving preganglionic fibres from the oculomotor nerve, and innervates the ciliary muscle and smooth muscles of the sphincter pupillae (circular muscle) of the iris.
A Review of Lens Biomechanical Contributions to Presbyopia
Published in Current Eye Research, 2023
Imbalance between lens capsule elasticity and interior lens elasticity as well as other material properties certainly does develop with age and is well documented, however, many other studies demonstrate additional factors are involved which could also contribute to reduced accommodative function. It has been demonstrated that lenticular growth alone accounts for 8–10% of age-related reduction to accommodative power.59 Changes to relative material properties between the lens capsule, fiber cell cortex, and fiber cell nucleus have all been observed and likely influence how these lens tissues interact mechanically.3,52,53 It has been suggested that physiologic change outside of the lenticular organ itself such as age-related change in the ciliary muscle or insertion of the iris root could contribute to initiating presbyopia as well,59 while it has also been suggested that presbyopia is in part a result of continual lens development through life.72
Diagnosis and Management of Post Traumatic Recurrent Unilateral Accommodative Spasm—A Case Report
Published in Journal of Binocular Vision and Ocular Motility, 2022
Praveen Kumar P, Amit Bhowmick, Neha Mahabale, Jameel Rizwana Hussaindeen, Dhanashree Ratra
This case report illustrates the presence of unilateral accommodative spasm, a rare clinical entity, and to the best of our knowledge, there are very few reports that have documented the same.7–12 All these cases of unilateral accommodative spasm were documented to have moderate to severe visual impairment, while our patient had mild visual impairment. The computational eye model to understand the impact of blunt injury demonstrated that the stress on the zonules could cause deformation of the lens.13 Ciliary muscle spasm, when circumference of zonules gets affected, presents with temporary incline toward myopic error.14 It is also reported that the trauma can damage the ciliary ganglion, leading to increased parasympathetic activity.8 In our case, the trivial injury on the left side followed by the traumatic events could have potentially resulted in a shock, leading to unilateral spasm of accommodation. The patient also reported increased stress levels at workplace due to the nature of the armed professions itself. A report by Tokiwa et al. also documented psychogenic etiology to be one of the causes for unilateral accommodative spasm.6 The manifestation of spasm was reported in the unaffected eye when the affected eye was occluded.11 In our report, to understand the manifestation in the unaffected eye, we had examined all the accommodation parameters when the affected eye was occluded.
Biometric assessment of pseudophakic subjects during objective accommodative stimulation: a prospective observational study
Published in Clinical and Experimental Optometry, 2022
Rajaraman Suryakumar, Andrew Maxwell
Accommodation is an increase in refractive power that occurs when the ciliary muscles contract, releasing tension in the zonule and causing the lens to become curved and shift forward.18 Accommodative capacity diminishes with age as the natural crystalline lens undergoes physical changes, including the loss of elasticity and hardening of the lens material.19 These age-related changes to the lens prevent the necessary curvature required for change in optical power of the eye.20 Replacement of the natural lens with a monofocal IOL during cataract surgery provides improved distance vision but does not restore accommodative capacity and ability to focus at near distances.21 The ultimate goal for pseudophakic presbyopia correction following cataract surgery is to restore accommodation for near vision.