NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Correcting Night Vision
From: Jared Sherman
Date: 2005 Aug 11, 21:14 -0400
From: Jared Sherman
Date: 2005 Aug 11, 21:14 -0400
Frank, I'm not sure that it is a "focus" issue per se. I have lasik damage,
and during the day when my pupils are contracted I see better than I do at
night. At night, glare, flare, and other distortion (like double vision and
halos) become a problem because the cornea is now unevenly surfaced, and when
the pupils are wide open at night--there is more lens area being used, so more
distortions are in the "used" image path.
Distortions in the cornea are actually common, and new procedures for
corneal topography actually map the front and rear of the cornea separately to
accomodate for them. Some of the ray tracing gizmos actually "project" a dot
into your eye, and you use a joystick to mark a spot where you see it. That
position is then compared to a mathematical position where a perfect eye SHOULD
have seen the dot. And almost everyone has irregularities within the eye that
show up during this kind of mapping.
So with or without focus issues, your eyesight will be "degraded" when your
pupils are wide open and more of the internal distortions affect the image you
are seeing.