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Home , Aniseikonia, Macropsia, Metamorphopsia, Micropsia

CET Continuing education

Macropsia/ Nicholas Phelps Brown describes the possible implications of an occasionally reported visual symptom. Module C13046, one general CET point, suitable for optometrists and dispensing opticians

acropsia and micropsia are infrequently reported Baldwin symptoms that can be challenging to evaluate. In theM perception is of an object larger than it really is and in micropsia an object appears to be smaller. The phenomena have been known for many years.1 T h e underlying causes range from trivial to life threatening. The causes are in the categories of: ● Optical ● Accommodational ● Retinal ● Cerebral. Cerebral causes affect both eyes equally, whereas the other causes may each affect a single eye. Accommodational causes are usually but not invariably bilateral. Alice in Wonderland syndrome is a rare oddity in which the sufferer, usually a child, Optical experiences themselves to be large and all external things to be small (illustration with Plus spectacle lenses magnify and apologies to Sir John Tenniel) minus lenses minify. A person will become aware of macropsia/micropsia to the that can be tolerated. phakic or pseudophakic eyes in which when there has been a change in their Aniseikonia is minimised by the use of the retinal surgeon has filled the optical status. This occurs when a a contact on the affected eye and posterior segment with silicone oil. hypermetrope parts with their plus eliminated by a posterior chamber lens This relatively high refractive index spectacles and opts for contact lenses, implant. material reduces the effectivity of the laser sight correction, or lens implants. The increase in that is posterior lens contour and produces The person may be disappointed associated with the development of an approximately +4.5D shift. The with their new emmetropia because nuclear is due to the increase spectacle lens correction will then of the loss of magnification and the in refractive index of the lens nucleus. cause magnification, which is likely to proportional reduction in The myopic shift commonly precedes produce unacceptable aniseikonia. that goes with it. Patients undergoing visible cataract.2 This requires a minus The biggest refractive shift of all used laser sight correction should always be shift in the patient’s spectacles with to be seen after without warned that they may lose a line of best concurrent minification. The reduced lens implants; something that is rarely corrected visual acuity and that this is image size is likely to be the reason why met today. Spectacle correction with more likely in the hypermetrope. patients with nuclear cataract do not a high plus lens for of about When a refractive shift affects one tolerate well the full minus adjustment +10D produces a magnification of eye or one eye more than the other, in their spectacles, particularly when about 33 per cent which is not tolerated the condition is that of the cataract is uniocular. by a patient with a phakic fellow eye. and an optical correction produces Myopia due to an axial length increase A correction for aphakia magnification or minification with is seen following produces a magnification of 7 to 10 resultant aniseikonia. Minor degrees of surgery in which an encircling explant per cent, which is usually tolerated. An aniseikonia are tolerable and compatible has been used. A spectacle correction for anterior chamber lens implant produces with binocular function, particularly if any surgically induced myopia produces about 3 per cent magnification and the condition has been present from minification. the posterior chamber implant no childhood, but each person has a limit A hypermetropic shift occurs in discernable magnification.

26 | Optician | 15.01.10 opticianonline.net Continuing education CET

Figure 2 Fluorescein angiogram of Figure 1. This shows the cystic pattern of the oedema

Figure 1 Cystic macular oedema (with fixation pointer)

Accommodational Retinal The receives proprioceptive If the retinal elements become spread feedback in relation to the muscular effort apart, the image of an object falls onto required for , which can fewer elements and is perceived as produce the of accommodative smaller. Conversely if the elements micropsia or of macropsia.1,3 In become crowded together the image of weakness of accommodation, a greater an object falls onto more elements and effort is needed to focus a near object is perceived as larger.5 Micropsia and and therefore the object is perceived macropsia are only experienced when to be nearer than it actually is. The the macular region is affected. retinal image remains the same size Retinal oedema and fluid beneath the for a familiar object at its actual neuroepithelium stretches the distance and it therefore appears small. causing micropsia (Figures 1 and 2). Accommodative micropsia is reported This occurs in cystic , in persons straining to accommodate at central serous , and in the onset of , but does not acute-onset ‘wet’ age-related macular occur when there is complete paralysis Figure 3 Choroidal melanoma lifting the macula degeneration. Other causes are of accommodation. choroidal tumours (Figure 3) and a When the accommodation is greater retinal detachment just beginning to lift than that needed to focus a near object, anticholinergic eye drop such as the macula. Micropsia is also reported it is described as accommodation excess. tropicamide may be used for a period in retinal re-attachment following A state of inappropriate maximal of time to relax the ciliary muscle. successful surgery. Choroiditis can accommodation is described as spasm The child’s circumstance should not cause macropsia or micropsia.6 The of accommodation. be overlooked and psychological help retina is commonly stretched unevenly, In accommodation excess and in may be needed. causing distortion (), spasm of accommodation a reduced The causes of organic spasm which is easily detected with the Amsler effort or no effort is required by the of accommodation are ocular or chart. The visual acuity is commonly person to focus a near object. The near neurological.The ocular causes include reduced by the retinal dysfunction due object is therefore judged to be a larger and affecting the ciliary to the condition causing the micropsia, object at a distance and the person is body and in traumatic myopia a myopic but it is also reduced geometrically in affected by macropsia. shift occurs with swelling proportion to the minification. Accommodation excess may be or spasm resulting from blunt trauma. primary and functional in nature or Ciliary spasm may also be induced by an Cerebral causes organic and secondary to .4 adverse reaction to a number of drugs Primary image formation occurs in The functional cases occur in young including sulphonamides and thiazides, the striate cortex at the occipital pole persons who may be suffering from such as acetazolamide. of the brain and the interpretation pressure at school and may have neurotic The neurological causes include of this image depends upon the or hysteric personalities. It is more likely irritative lesions of the brain stem function of the association areas of to occur in children with uncorrected affecting the third nerve nucleus as the pre-striate and also of the parietal refractive errors. The symptoms are may occur in encephalitis. Spasm of and temporal regions of the brain. The blurred distance vision, macropsia accommodation affecting one eye can pre-striate cortex is associated with and . A refraction without occur with an Adie in the tonic form recognition,7 motion perception8 mydriatic is likely to show a variable phase in association with . Spasm and colour recognition.9 Further degree of myopia, which can result in of accommodation may also occur forward in the brain the parietal and the child’s condition being aggravated as a component of cyclic oculomotor temporal areas are associated with by the prescription of minus lenses. spasm, a rare and recurring condition, visuospatial perception.10 Temporal The management involves a mydriatic which affects the pupil and extraocular lobe dysfunction can cause macropsia refraction and spectacles given with muscles of one eye supplied by the third or micropsia.11 a full plus refractive correction. An nerve. dysfunction with opticianonline.net 22.01.10 | Optician | 27 Continuing education CET

macropsia may occur without evident pathology in the of Multiple-choice questions – take part at opticianonline.net and in partial temporal lobe . The aura of migraine takes on many Which of the following is not a cause of Which of the following would not cause a forms of sensory disturbance and is 1 perceived image size change? 4 decrease in axial length? not necessarily followed by a headache. A Accommodation fluctuation A Central serous retinopathy When it involves micropsia this can B Refractive change B Posterior staphyloma cause much distress to the sufferer when C Peripheral retinal elevation C Choroidal neovascular AMD first experienced. Partial temporal lobe D Macular oedema D Retinal detachment with macula off epilepsy is an epilepsy without or loss of consciousness. The sufferer Which of the following is true regarding Which of the following may result in is affected by altered awareness or by 2 optical macro/micropsia? 5 persistent micropsia? sensory disturbance including visual A A hyperope experiences micropsia when A disturbance.Temporal lobe disturbance moving from spectacles to contact lenses B LSD with micropsia also occurs in response B A hyperope experiences macropsia when C to toxic brain states including that moving from spectacles to contact lenses D Magic mushrooms due to hallucinogenic drugs, such C A hypermetrope undergoing as dextromethorphan, LSD, magic may experience macropsia Dysfunction of which lobe results in mushrooms, cannabis, opiates (such as D A myope undergoing lens implantation may 6 macropsia/micropsia? morphine) and heroin. Micropsia may experience micropsia A Parietal be persistent after ceasing long-term B Occipital cocaine use.12 Which of the following binocular C Temporal Pathological cerebral causes of 3 corrections will result in the least D Frontal micropsia/macropsia include temporal aniseikonia? lobe tumours, brain injury, cerebral A Spectacles infarcts, multiple sclerosis and Epstein- B Contact lenses Barr virus infection (infectious C Corneal refractive surgery mononucleosis) which occasionally D implantation causes encephalitis.13 Micropsia may be the presenting sign of this infection.14 15 Successful participation in this module counts as one credit towards the GOC CET scheme Alice in Wonderland syndrome administered by Vantage and one towards the Association of Optometrists Ireland’s scheme. is a rare oddity in which the sufferer, The deadline for responses is February 18 2010 usually a child, experiences themselves to be large and all external things to be small, and occasionally vice versa. In the morphology. Brit J Ophthalmol, 1987; 71: 11 Ceriani F, Gentilashi V, et al. Seeing famous story by Lewis Carroll, Alice 405-414. objects smaller than they are: micropsia experienced this phenomenon after 3 Alexander KR. On the nature of following right tempero-parietal infarction. eating cake and drinking a magic potion. accommodative micropsia. Am J Optom Cortex, 1998: 34; 131-8. Perhaps the author was familiar with Physiol Opt, 1975; 53: 79-84. 12 Wenzel K, Bernstein PD et al. Levels of hallucinogenic substances? However, 4 Duke-Elder WS. Text-Book of dissociation in detoxified substance abusers Alice in Wonderland syndrome can , Vol 4, Kimpton, London and their relationship to chronicity of alcohol be primary without hallucinogenic 1949 pp4439-4444. and drug use. J Nerv Ment Dis, 1996; 184: substances being implicated. It can 5 Duke-Elder WS. Text-Book of 220-7. also be secondary to cerebral viral Ophthalmology, Vol 1, Kimpton, London 13 Lahat E, Berkovitch M et al. Abnormal infection.13 1932 p989. visual evoked potentials in children with Psychological disturbance is 6 Duke-Elder WS. Text-Book of ‘Alice in Wonderland’ syndrome due to implicated as a cause of functional Ophthalmology, Vol 3, Kimpton, London . J Child Neurol, micropsia/macropsia.16 Micropsia may 1940 p2204. 1999; 14: 732-5. be a component of a dissociative disorder, 7 Ruddock HK. Spatial vision after cortical 14 Cinbis M, Aysum S. Alice in Wonderland a condition which the person separates lesions. In Vision and Visual Dysfunction. syndrome as an initial manifestation of certain thoughts or memories from 10 Spatial Vision. Ed D Reagan. pp 261-289. Epstein-Barr virus infection. Br J Ophthalmol, normal consciousness. In this condition Macmillan, London 1991. 1992; 76: 316. there may be a breakdown of memory, or 8 Zihl J, von Cramon D, Mai N. Selective 15 Evans RW, Rolak LA. The Alice in of awareness of identity and the person disturbance of movement vision after Wonderland syndrome. Headache, 2004; may also have disordered perception bilateral brain damage: a review of 55 cases. 44: 624-5. with micropsia.17The psychoanalytical Brain, 1985; 106: 313-340. 16 Schneck JM. Psychogenic micropsia in explanation of micropsia is that the 9 Plant GT. Disorders of colour vision in fact and fiction. JAMA, 1984; 251; 2350. person is trying to distance themselves diseases of the nervous system. In Vision and 17 Lipsanen T, Kokeilla J et al. Micropsia and from an environment fraught with Visual Dysfunction 7 Inherited and acquired dissociative disorders. J Neuro-ophthalmol, conflict.18 ● colour vision deficiencies. Ed Foster DH, 2003; 23: 106-7. Macmillan, Basingstoke 1991 pp 173-198. 18 Walsh & Hoyt’s Clinical Neuro- References 10 Anderson RA. Inferior parietal lobule Ophthalmology, Sixth Edition. Lipincott 1 Duke-Elder WS. Text-Book of function in spatial perception and Williams & Wilkins, Philadelphia, 2005 Vol Ophthalmology Vol 1, Kimpton, London visuomotor integration. In Handbook 1 p628. 1932 p1072. of Physiology, Section 1, Vol V. Plum F 2 Brown NAP, Hill AR. Cataract: The Ed. American Physiology Soc, Bethesda ● Nicholas Phelps Brown is a consultant relationship between myopia and cataract Maryland 1987; pp 483-518. ophthalmologist practising in Harley Street

28 | Optician | 22.01.10 opticianonline.net