Dynamic accommodation and myopia.
Invest Ophthalmol Vis Sci
; 40(9): 1968-74, 1999 Aug.
Article
en En
| MEDLINE
| ID: mdl-10440250
ABSTRACT
PURPOSE:
Accommodative effort during nearwork is thought to be a causative factor in the development of myopia. It has been proposed that an anomaly in autonomic control may be a precursor to the development of myopia. In the present study the closed-loop accommodation response after variations in fixation period was investigated in emmetropes, early-onset myopes and late-onset myopes to determine characteristics of reflex accommodation for each refractive group.METHODS:
Closed-loop accommodation responses were measured in a group of emmetropes (n = 7), early-onset myopes (n = 7), and late-onset myopes (n = 7) by use of a dynamic tracking infrared optometer. A variation in fixation period (10 seconds, 60 seconds, and 180 seconds) before an accommodative step was used to stimulate the accommodation control mechanism differentially.RESULTS:
Group results of accommodative response times showed that late-onset myopes were significantly affected by the duration of fixation before the change in stimulus vergence. Accommodative response times after 3 minutes of sustained near vision were significantly longer than those observed for other groups for the near-to-far condition. Reaction time appears to be independent of refractive grouping, prior fixation period, and direction of step change.CONCLUSIONS:
Late-onset myopes showed significantly extended accommodation response times after a sustained near vision task that was demonstrable under well-controlled experimental conditions. The extended response times observed in the present study were consistent with previous reports of refractive shifts in late-onset myopes and early-onset myopes and provide a corollary between reflex and adaptive components of the accommodation response. Potential mechanisms are discussed in an attempt to explain the resultant hysteresis under closed-loop viewing conditions.
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Banco de datos:
MEDLINE
Asunto principal:
Acomodación Ocular
/
Miopía
Límite:
Adult
/
Female
/
Humans
/
Male
Idioma:
En
Revista:
Invest Ophthalmol Vis Sci
Año:
1999
Tipo del documento:
Article
País de afiliación:
Reino Unido