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Alice in Wonderland Syndrome
Published in Alexander R. Toftness, Incredible Consequences of Brain Injury, 2023
(STORY 4) A young boy began experiencing Alice in Wonderland syndrome at the age of ten following an infection that caused scarlet fever. One symptom that he regularly experienced was “that he perceived objects as reduced in size but at the correct distance and proportion” (p. 3). These episodes of micropsia often lasted longer than 20 minutes and occurred multiple times per day across many months. When he was 12 years old, he was placed in an fMRI scanner during an episode of micropsia. When compared to the brain of a child that was not experiencing micropsia, the scan revealed a reduction of brain activity in some parts of the brain that process visual information and an increase in brain activity elsewhere. The cause of the micropsia was unknown, but some type of migraine was one possible explanation as the child often experienced periods of aversion to sound and light such as many people with migraines experience. He did not, however, have a history of migraine headaches, leaving the case a mystery. As treatment, he began to wear glasses that increased the size of nearby objects during his micropsia episodes, which helped him feel more comfortable but did not prevent the episodes from recurring (Brumm et al., 2010).
MRCPsych Paper A1 Mock Examination 4: Answers
Published in Melvyn WB Zhang, Cyrus SH Ho, Roger Ho, Ian H Treasaden, Basant K Puri, Get Through, 2016
Melvyn WB Zhang, Cyrus SH Ho, Roger CM Ho, Ian H Treasaden, Basant K Puri
Explanation: Dysmegalopsia is also known as the Alice in Wonderland effect. Illusory change in the size and shape (both reduction and increase in size) is perceived visually. In this example, the objects (i.e. the heads) appear to be enlarged. This phenomenon is specifically known as macropsia. When the object is perceived as smaller than it actually is, this is known as micropsia.
Posterior cortical atrophy: clinical, neuroimaging, and neuropathological features
Published in Expert Review of Neurotherapeutics, 2023
John Best, Marianne Chapleau, Gil D. Rabinovici
The defining feature of PCA is the progressive decline in visuospatial and visuoperceptual functions. Patients often have preserved insight into their deficits. Individuals frequently report a prior history of evaluations with optometrists and ophthalmologists to investigate their visual complaints. This can include frequent changes in eyeglasses or even surgical procedures such as cataract surgery, without any improvement in their symptoms. Both in driving and navigating around the home, there is difficulty in judging distances, reading signs, or locating items. There can also be difficulty with identifying objects (visual agnosia) or recognizing faces (prosopagnosia). Perception can also be frequently altered, with perception of objects being larger (macropsia) or smaller (micropsia) than they actually are, or incorrect perception of motion.
Hyalocytes in proliferative vitreo-retinal diseases
Published in Expert Review of Ophthalmology, 2022
Charlotte H. Jones, Wei Gui, Ricarda G. Schumann, Stefaniya K. Boneva, Clemens A. K. Lange, Koen A. van Overdam, Toco Y. P. Chui, Richard B. Rosen, Michael Engelbert, J. Sebag
First described in 1865 by Iwanoff [15], macular pucker (MPK) is defined as a premacular, avascular, fibrocellular membrane with folds and striae in the underlying inner retina, accompanied by disturbed cytoarchitecture in the outer retina [16,17]. The term ‘epiretinal membrane (ERM)’ is not as accurate as the term ‘premacular membrane (PMM),’ which is the tissue that causes macular pucker, the term that correctly refers to the effects of this membrane on the macula. Although the term ‘idiopathic’ is common in the literature, it is no longer appropriate because MPK is now known to be caused by vitreous pathology. The prevalence of MPK is between 6% and 11.8% [18–20]. Over the age of 70 years the prevalence is as high as 15.1% [20], with bilateral involvement between 19.5% [18] and 31% [19] of cases. Chinese may have a higher prevalence than Caucasians, African Americans, or Hispanics [21]. The most common patient complaints are metamorphopsia and blurring, although micropsia and monocular diplopia have also been reported [22].
Aniseikonia and anisometropia: implications for suppression and amblyopia
Published in Clinical and Experimental Optometry, 2019
Jayshree South, Tina Gao, Andrew Collins, Jason Turuwhenua, Kenneth Robertson, Joanna Black
Changes in retinal receptor distribution from retinal asymmetry or pathology will cause the same physical size retinal image to be captured by a different number of photoreceptors, resulting in a change in the perceived image size and shape. This can occur in conditions such as epiretinal membranes, macular oedema, or axial myopia. Epiretinal membranes that cause macular contraction compress photoreceptors closer together, so that a retinal image with the same angular size now stimulates more photoreceptors, resulting in macropsia (image appears larger than normal).2014 Conversely, if the photoreceptors are stretched across a larger area such as in high axial myopia, central serous chorioretinopathy1992 or macular oedema, the same retinal image stimulates fewer photoreceptors, resulting in micropsia (image appears smaller than normal). Retinally induced aniseikonia can arise from both overall differences in image sizes between eyes and localised distortions in image shape, producing severe symptoms that are difficult to treat because the magnitude of aniseikonia varies across the visual field.2007 Even after appropriate surgery or treatment for the underlying conditions, photoreceptor spacing may not fully recover, leaving the patient with distorted vision.2014