User:Sunderv/Macropsia

Macropsia

General Background Information

Macropsia is a neurological condition that has adverse effects on affected humans' sight. Instead of seeing things as they commonly appear, macropsia causes objects to appear larger than normal, which in turn, has the effect of making the person seem smaller. Macropsia can be caused through other neurological conditions or diseases, or through the use of psychoactive drugs. Macropsia is often categorized as a symptom of many other visual disorders, such as aniseikonia, dysmetropsia.

Eye

Important Info to be discussed in article

Our plan is to discuss the two major aspects of macropsia: Causes and symptoms.

There are many ways through which macropsia results; some of these causes are other neurological and opthalmic conditions, while other causes are psychoactive drugs. Some examples of the neurological conditions are brian tumors, frontal lobe epilepsy, and Alice in Wonderland Syndrome (AIWS), also called Todd's Syndrome. AIWS is a condition affecting a range of visual perceptions, and is often associated in some way with the other neurological conditions mentioned above. AIWS can be a symptom of Epstein-Barr Virus (EBV), therefore there it is logical that Macropsia is indirectly related to EBV. In the case of dysmetropsia caused by surgical reattachment for macula-off rhegmatogenous retinal detachment, the macropsia could be linked to the misalignment and/or abnormal spatial distribution of photoreceptors. The compression of photoreceptors closer together could stimulate more receptors and an object would consequently be perceived as larger (macropsia). If the photoreceptors were to be stretched apart, less stimulation of the photoreceptors would result in perceiving an object to be smaller (micropsia). This effect seems to be heterogeneous across the retinal area affected. It appears that the photoreception distribution associated with dysmetropsia following macula detachment occurs soon after the neuroretina from the retinal pigment epithelium or by the surgical reattachment procedure.

The most obvious symptom of Macropsia is the presence of exceptionally enlarged objects throughout the visual field. Stemming from this symptom, someone with Macropsia may feel undersized in relation to his or her surrounding environment. Patients with Macropsia have also noted the cessation of auditory function prior to the onset of visual hallucination, indicating possible seizure. A buzzing sound in the ears has also been reported immediately before Macropsia development. Those afflicted may additionally experience extreme anxiety both during and after episodes as a result of the overwhelming nature of his or her distorted visual field. Psychologically, a person with macropsia may have feel separation from the outside world and even immediate family consistent with the perceived difference in physical size. Due to the fear and anxiety associated with the condition, those who previously suffered hesitate to recount the episodes. Symptoms caused chemically by drugs such as cannabis, magic mushrooms,or cocaine tend to dissipate after the chemical compound has been excreted from the body

The extent of macropsia can be measured by the New Aniseikonia Test (NAT). Threshold dysmetropsia can be measured using a bracketing process by determining when a subject determines that varying pairs of circles of different sizes are perceived the same. This procedure allows one to quantify the interocular differences in retinal image size in the vertical and horizontal meridians. The range of horizontal and vertical dysmetropsia can be given as a percent where a positive value reflects macropsia and a negative value reflects micropsia.

Tentative Sources

1. Ugarte M. Horizontal and vertical micropsia following macula-off rhegmatogenous retinal-detachment surgical repair. "Grafes Archive for Clinical and Experimental Ophthalmology" 244 (11): 1545-1548 NOV 2006.

2. SCHNECK JM. Macropsia and micropsia. "AMERICAN JOURNAL OF PSYCHIATRY" 122 (3): 350-350 1965.

3. Abe,. Macropsia, micropsia, and episodic illusions in Japanese adolescents. "JOURNAL OF THE AMERICAN ACADEMY OF CHILD AND ADOLESCENT PSYCHIATRY" 28 (4): 493-496 JUL 1989

4. Ghanizadeh A. Citalopram-induced macropsia. "CLINICAL NEUROPHARMACOLOGY" 30 (4): 246-247 JUL-AUG 2007.

5. Wright J, and Boger W. Visual Complaints From Healthy Children. Survey of Ophthalmology 44 (2) 113-121 1999.

Allotment of Workload

At the present time, we have decided to split up the work as follows:

Causes: 2/3 Phil Eliades, 1/3 Zayn Hassan

Symptoms: 2/3 Vikas Sunder, 1/3 Zayn Hassan Retrieved from "http://en.wikipedia.org/wiki/Macropsia_project_proposal" Categories: Proposed deletion as of 3 October 2009 | All articles proposed for deletion