The Dark Focus of Visual Accommodation: Its Existence, Its Effects, Its Measurement
Simonelli, Nicholas Michael
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/66573
Description
Title
The Dark Focus of Visual Accommodation: Its Existence, Its Effects, Its Measurement
Author(s)
Simonelli, Nicholas Michael
Issue Date
1980
Department of Study
Psychology
Discipline
Psychology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Psychology, Experimental
Language
eng
Abstract
The "dark focus" or "resting state" of visual accommodation to the refractive state to which the eye tends to return in the absence of any visual stimulus, as in complete darkness. This tendency is reviewed in terms of past and current attempts at its quantification and its effects on visual performance. In Experiment I, a new optometer -- the polarized vernier optometer -- is described and compared experimentally to the better-known laser optometer. The former compared favorably to the latter in terms of subject acceptability and agreement of dark focus measurements.
In Experiment II, the accommodative responses to Snellen letters and Landold Cs of varying size were measured. It was observed that as the targets decreased in size and, consequently, fineness of detail, accommodation was increasingly further out. As targets became larger, accommodation shifted in toward the dark focus.
In Experiment III, the dark focuses of 301 observers, varying in age and far point (i.e., the amount of nearsightedness or farsightedness) were measured. It was observed that the difference between the measured dark focus and the far point ("relative dark focus") varies little in its distribution over a wide range of ages and far points. There was, however, a slight tendency for the realtive dark focus to be smaller with increasing age and increasing hyperopia, and for it to be larger with increasing myopia.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
