網膜鏡檢和光屈光法之結合及改進
Date Issued
1999
Date
1999
Author(s)
王藹侯
DOI
882314B002374
Abstract
Purpose. Conventional photorefractors applying either camera or
video have fixed distance between the viewing line and the light source
and read the refraction from the size of the crescent. Since the
relationship between the crescent size and the refraction is not linear and
the resolution at higher refractive error is poor, a hand-held
photorefractor was introduced which employed fixed crescent:pupil ratio
as endpoint and read the refraction from the varying distance between the
eye and the light source. The relationship between the distance and the
refraction is linear.
Methods. For ‘axial’ myopia and hyperopia, a simple formula holds
that do = Ratio‧Pu‧lo‧R where do is the distance between the eye and the
light source; Ratio is the non-crescent:pupil ratio; Pu is the pupil diameter;
lo is the test distance and R is the refraction relative to the vergence of the
test distance. A design of hand-held photorefractor, similar in shape with
direct ophthalmoscope and retinoscope, was proposed that by sliding the
Ai-Hou Wang
light source up and down and looked through a fixed viewing hole for a
fixed crescent:pupil ratio, the refraction could be read from a linear scale
with good resolution. Oblique astigmatism could be read simply by
aligning the instrument with the oblique crescent, no need to rely upon
complicated calculation.
Results. With random combination of spherical and cylindrical lenses
in front of a model eye I read the refraction blindly with a prototype of
this hand-held photorefractor. The result was satisfactorily accurate.
Conclusions. A practical hand-held photorefractor was designed,
with which the refraction could be read on a linear scale with good
resolution, and the axis of oblique astigmatism could be determined by
simply aligning the instrument with the tilted crescent.
Publisher
臺北市：國立臺灣大學醫學院眼科
Type
journal article
File(s)![Thumbnail Image]()
Loading...
Name
882314B002374.pdf
Size
248.8 KB
Format
Adobe PDF
Checksum
(MD5):086851c3e647ff370fbec64fae330283