Apparatus and method for making ophthalmic measurements

A device for use in fitting lenses to spectacles frames wherewith ophthalmic measurements are applied directly to frames selected by patients. A frame without lenses is adjusted to fit the patient, the fitting device is applied to the frame and the whole placed upon the face. Measurements of distances from extreme lateral and inferior points on the frame rims to the patient's visual axis in the case of each eye are taken for use in edging the lenses to a size and shape which will locate their optical centers in coincidence with the patient's visual axes when the spectacles are glazed and put to use.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to improvements in measuring apparatus and method 
for use in fitting ophthalmic lenses in spectacles frames. 
2. Description of the Prior Art 
Fitting lenses to spectacles frames requires, in each case of each lens, 
the taking of measurements which can be used to locate the lens optical 
center in proper relationship relative to the patient's visual axis when 
the spectacles are worn. 
While various measuring scales and fixtures are used for this purpose (the 
apparatus of U.S. Pat. No. 4,055,900 being exemplary) less than optimum 
accuracy of measurement has resulted principally from a lack of means or 
method of compensating for deviation of visual axis from pupil center. 
A patient's visual axes do not necessarily exit from the centers of 
respective pupils but may do so nasally or temporally to the extent of 0.1 
to 0.2 mm for example. Accordingly, the techniques used heretofore of 
referencing from the center or other arbitrarily selected points on a 
patient's pupil fail to provide an assurance of whether spectacles frame 
measurements so taken accurately represent the true distances needed to 
ultimately properly locate a lens optical center relative to the patient's 
visual axis. 
It is, accordingly, a principal object of this invention to provide novel 
means and method of assuring accurate alignment of lens optical center 
relative to a patient's visual axis in the case of each lens of a glazed 
spectacles frame intended to be worn by the patient. 
A further object is to provide means and method for locating the position 
at which a patient's visual axis intersects the plane of a lens rim of a 
spectacles frame when the frame is properly fitted to the patient. 
Other objects and advantages of the invention will become apparent from the 
following description. 
SUMMARY OF THE INVENTION 
The aforesaid objects and their corollaries are accomplished by providing 
in a spectacles frame fitting system, e.g. of the type represented in U.S. 
Pat. No. 4,055,900, a novel light-diffracting reticle located forwardly of 
a patient's pupil in the general plane of a lens rim of a spectacles frame 
when the frame, with attached fitting system, is placed in proper wearing 
position. The reticle, being in the form of a disc is of smaller diametral 
size than the patient's pupil and rendered manually vertically and 
horizontally adjustable in the plane of the lens rim. 
With vertical and horizontal adjusting screws, the recticle is first 
roughly aligned with the patient's pupil, preferably by a fitting 
practitioner, and finally brought into precise alignment with the 
patient's visual axis by the patient himself. 
This latter adjustment is accomplished by providing a distant bright spot 
target for the patient to monocularly fixate upon. The target is seen 
directly by virtue of the patient's free annular pupil aperture and a 
bright circular ring pattern is formed around the target by the presence 
of the diffracting disc. 
If the bright ring pattern is not perceived as centered with the target, 
the patient is instructed to adjust the reticle to the extent necessary to 
bring the bright ring into an apparent concentric relationship with the 
target. This produces a centering of the reticle upon the patient's visual 
axis and distances from the so adjusted reticle to extreme lateral and 
extreme inferior points on the corresponding spectacles lens rim represent 
the measurements needed for finishing a lens to be mounted in the rim.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1 there is illustrated a measuring system 10 with which the 
position of intersection of a patient's visual axis with the plane of a 
spectacles lens rim may be precisely determined. 
The system of FIG. 1 includes measuring device 12 and spectacles frame 14 
to which the device 12 is attached. The attachment of device 12 to frame 
14 is made by positioning locators 16 and 18 into the lens grooves of each 
of right and left eye lens rims 20a and 20b of frame 14. Locators 16 are 
positioned nasally of rims 20a and 20b at their extreme lateral extensions 
and locators 18 are positioned at the extreme inferior points of the lens 
grooves in rims 20a and 20b. 
To the extent thus far described, measuring device 12 is generally similar 
to one of the embodiments of U.S. Pat. No. 4,055,900 and those interested 
in greater details of the aforementioned means and method of attaching 
device 12 to a spectacles frame may refer to U.S. Pat. No. 4,055,900. 
Device 12 further incorporates vertically and horizontally adjustable sides 
22 and 24 operable by vertically and horizontally disposed adjusting 
screws 26 and 28 respectively. 
Extending laterally from each of horizontal slides 24 are reticles 30 from 
which the distances laterally and downwardly (horizontally and vertically) 
to extreme lateral and extreme inferior points in the grooves of each of 
lens rims may be measured with scales 32 and 34. Readings of scales 32 and 
34 are taken from fiducial marks 36 and 38. 
Measurements determined from scales 32 in each case represent the 
horizontal distance d.sub.1 (FIG. 5) from the visual axis interecept and 
the optical center (OC) to extreme lateral edge of a lens L to be fitted 
in frame 14. Measurements taken from each of scales 34, on the other hand, 
represent the distance d.sub.2 from the visual axis to the extreme 
inferior extension of the lens edge. 
For example, in fitting a conventional single vision lens worn at 
10.degree. pantoscopic angle at normal fitting distance and where the 
objective is to cause the optical axis to intersect the center of rotation 
of the eye, the optical center is displaced downwardly 5 mm from the 
measurement on scale 34. When fitting special lenses, e.g. of the 
progressive addition type where the fitting objective is to obtain 
coincidence of primary gaze visual axis with optical center, the 
measurement on scale 34 is used unmodified. 
It should be understood that while lens L of FIG. 5 is illustrated as being 
a patient's right eye lens, i.e. to be fitted in the right eye rim 20a of 
spectacles frame 14, similar measurements d.sub.1 and d.sub.2 would be 
used in mirror-image fashion for the finishing and glazing of a lens to be 
fitted into the left eye lens rim 20b of frame 14. 
In the finishing of a lens L (FIG. 5) measurements d.sub.1 and d.sub.2 are 
utilized according to the traditional "boxing" method of specifying lens 
size. Those interested in these details may refer to U.S. Pat. No. 
4,055,900 or to the publication referred to therein as "The Boxing Method 
of Specifying Eye Size" by Glen A. Frye, PhD. Journal of the American 
Optometric Association, February, 1959, pages 481-484. 
Turning now to details of each reticle 30 and its use in establishing the 
location of intersection of a patient's visual axis with the plane of a 
lens rim 20a or 20b, there is depicted in FIG. 2 an enlarged illustration 
of one of reticles 30, namely that shown within the right eye lens rim 20a 
of frame 14. The reticle within lens rim 20b, being of identical 
construction and function, will not be separately described herein since 
the description which follows can be applied directly thereto. 
Reticle 30 (FIG. 2) is suspended from slide 24 (FIG. 1) by support 40 which 
may comprise a length of wire. The reticle, being cemented or otherwise 
attached to wire 40, is preferably formed of a transparent or translucent 
glass or plastic material and is in the form of a thin disc rendered 
circularly light-diffracting by the provision of circular striations 42, 
ridges or other such means on at least one of its sides. 
As depicted in FIG. 2, reticle 30 is of a diametral size less than that of 
a patient's pupil aperture 44 so that at maximum pupil contraction under 
ordinary examining or fitting room conditions, the placing of reticle 30 
before the eye leaves a free annular pupil aperture 46. 
Alignment of reticle 30 with the visual axis of eye E (FIG. 2), for 
example, is accomplished by initially positioning the reticle forwardly of 
pupil aperture 44 using adjusting screws 26 and 28 of device 12. This 
initial adjustment of reticle 30 is preferably performed by the fitting 
practitioner and may be considered as a "coarse" adjustment since only 
positioning before the pupil aperture 44, but not necessarily in the 
illustrated centered relationship, is required. A bright spot target, e.g. 
a spot of light against a projection screen, is located forwardly of the 
patient and the patient is directed to fixate monocularly thereupon. The 
bright spot target is diagrammatically illustrated with the full line 
circle in each of FIGS. 3 and 4 and will be referred to hereinafter as 
target 48. 
With reticle 30 before the pupil aperture 44, target 48 will be seen 
directly by virtue of the patient's free annular pupil aperture 46. Also 
seen will be a bright circular ring pattern of light around target 48 due 
to the presence of the diffracting reticle 30. This ring pattern is 
illustrated by broken lines 50 in FIGS. 3 and 4. 
The patient is instructed to center the ring pattern around target 48 by 
self manipulation of adjusting screws 26 and 28. For example, if pattern 
50 is off-center as in FIG. 3, the patient should bring it to the position 
illustrated in FIG. 4. 
With pattern 50 viewed as being centered on target 48 (FIG. 4) reticle 30 
can be considered as being centered upon the patient's visual axis. The 
reticle, in turn, being disposed in the plane of lens rim 20a gives 
indication of the position of intersection of the patient's visual axis 
with the plane of lens rim 20 and readings of scales 32 and 34 provide the 
aforementioned measurements d.sub.1 and d.sub.2 of FIG. 5. 
Knowing measurements d.sub.1 and d.sub.2, lens L can be finished by edging 
to the shape and size required for fitting into lens rim 20a with its 
optical center OC approximately located relative to the patient's visual 
axis when the spectacles frame 14 with lens L is worn by the patient. 
Those interested in details of the procedure used to finish ophthalmic 
lenses according to dimensions d.sub.1 and d.sub.2 may refer to U.S. Pat. 
No. 4,055,900. 
It should be appreciated that various modifications and adaptations of the 
precise form of the invention here shown may be made to suit particular 
requirements. For example, means other than slides 22 and 24 may be used 
to adjustably support reticles 30 in the planes of lens rims 20a and 20b. 
The embodiments of FIGS. 1-4 of U.S. Pat. No. 4,055,900 are exemplary. 
Accordingly, it is intended that all modifications which incorporate the 
novel concept disclosed are to be construed as coming within the scope of 
the claims or the range of equivalency to which they are entitled in view 
of the prior art.