PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 1015520

Instrument myopia--microscopy.

O W Richards
View original source ↗Export metadata ↓

Abstract

Looking through optical instruments stimulates the eye to accommodate more than would be necessary for naked eye viewing; this increased near power is called instrument myopia. The amount (up to -5 diopters) varies with the observer and the conditions of viewing. Using microscopes produces -1.5 to -2 diopters of instrument myopia. More instrument myopia is found with low-power magnification, inexperienced users, and when focusing form minus blur to sharp image. Physiologically, the instrument myopia appears to be associated with an accommodative equilibrium position and, psychologically, with a sensing of proximity.

Explore related subjects

Accommodation, OcularAge FactorsDistance PerceptionHumansLightMicroscopyMyopiaOptics and PhotonicsJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

O W Richards. 1976. Instrument myopia--microscopy.. https://pubmed.ncbi.nlm.nih.gov/1015520/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1992

Development of accommodation and convergence in infancy.

Paraxial photorefraction was used to assess the development of accommodation and convergence in a large sample of infants under 1 year of age. The infants viewed small dolls placed at various distances (200-25 cm). The majority of infants at all ages demonstrated appropriate convergence for target distance, regardless of manifest refractive error. However, accommodation lagged behind convergence in development. Infants under 2 months tended to demonstrate either flat accommodation responses with a fixed plane of focus at around 30 cm, or accommodated appropriately for near targets, but failed to relax their accommodation sufficiently for the more distant targets. Thus, the focussing error increased with increasing target distance. Since the manifest refractive error was estimated by extrapolating the accommodation function to 0 diopters demand, these infants demonstrated spuriously myopic behavior. After 2 months, the majority of infants showing emmetropic behavior had accommodation responses that changed appropriately with target distance. However, infants with myopic or hyperopic manifest refractive errors displayed a variety of accommodative styles.

Accommodation, Ocular↗
PubMed1992

Cycloplegic refraction in children: single-dose-atropinization versus three-day-atropinization.

A new scheme for refractive measurements under atropine cycloplegia was tested in 90 strabismic children aged two to several years. Refraction was determined by an autorefractor (CANON R 10) 90 minutes after application of two drops of atropine (0.5% atropine children < 2 1/2 years; 1.0% atropine children > 2 1/2 years) and compared with the results after 3 days of receiving 1 atropine eyedrop 3 times daily. In 86.5% the spherical equivalents differ not more than 1.0 diopter (p = 0.05); the correlation was 0.99. Astigmatic corrections were in agreement in 95.5%, the axis of cylinders in 93.0% (p = 0.05); the correlations were 0.95 and 0.97. The residual accommodation 90 minutes after 2 drops of atropine was not more than 1 diopter in all children. The additional cycloplegic effect of the three-day-atropinization was only 0.5 diopters. This new type of application allows a more rapid and less toxic assessment of refraction than the usual three-day-atropinization.

Accommodation, Ocular↗
PubMed1992

Does work with visual display units impair visual activities after work?

It is well established that visual display unit (VDU) operators complain of visual fatigue and visual stress during after-work hours. The present study was divided into two parts. In the first part, standard eye examinations were performed on a group of VDU workers (n = 32) and a control group (n = 15); those subjects who were found to have correct vision (n = 16 and 13, respectively) participated in the second part. The eye examinations revealed that on the average, the VDU workers suffered more than twice as many visual impairments as the controls. In those with correct vision, the near point of accommodation was measured at the beginning of the workday at the start of the week, and at the end of the workday, four days later. In the VDU group, the decrease in accommodation was uniformally distributed between zero and 1.0 diopter, whereas among the non-VDU workers, 77% of the decrease was between zero and 0.25 diopter. The dynamic range of accommodation in the VDU workers on the second examination was smaller than on the first. We conclude that some of the visual stress and visual fatigue that developed at work hindered visual activities after work.

Accommodation, Ocular↗