Ophthalmic Measuring Instrument

The proper fitting of contact lenses involves various ophthalmic measurements, such as iris diameter, pupil diameter, height of the palpebral fissure, as well as parameters of the contact lens. Unfortunately, present day instruments and methods used for making such measurements are generally inefficient, cumbersome, or unduly expensive.

Measurements of the pupil, iris and fissure are currently made with the use of a hand held graduated rule or a reticle used with a simple magnifier or a more sophistocated slit lamp. The use of the rule is subject to the accuracy of the markings on the rule, elimination of eye movement during measuring, elimination of parallax errors and unwanted shadows. Even the most sophistocated systems, however, have an accuracy of about .+-.0.3 mm, whereas proper fitting of some types of contact lenses require accuracy within .+-.0.1mm.

None of the above instruments are used to measure the parameters of contact lenses, such as overall diameter, optical zone, and peripheral curve. Instead, a separate instrument is employed and usually comprises a 7.times.magnifier having a reticle with scale markings. Proper use of the instrument requires exact positioning of the lens relative to the scale, which is often a cumbersome procedure.

In summary, there is presently no instrument capable of making highly accurate and reliable measurements of the eye, and no single instrument capable of making measurements of both the eye and the contact lens.

The present invention provides a simple and inexpensive instrument and method for accurately making all measurements of the eye required for the fitting of contact lenses, as well as measurements of the individual lens. The device is capable of measurements of a tolerance less than 0.1mm for any object or image having reasonably distinct boundaries or edges and is particularly suitable for ophthalmic measurements.

The device is characterized by a housing having a magnifier in one portion and a viewing aperture in another portion. The object to be measured is magnified and reflected toward the viewer by an internal split mirror system. The mirrors are mounted in a coplanar relationship, and one mirror may be rotated out of the plane of the other. The degree of rotation is controlled manually with an external handle that is associated with a graduated scale on the body of the housing.

With mirrors in a coplanar relationship, the magnified image viewed through the viewer appears whole. Upon rotation, the image is split into two parts, and rotation is continued until opposite edges of the parts coincide. The degree of rotation is directly correlated to the linear dimension being measured, and such dimension is indicated on the graduated scale.

From the foregoing, it may be seen that a measurement operation requires merely aligning the object through the viewer and rotation of the handle to make a measurement, which is simple, reliabile, and less time consuming than existing methods.

The device may include right angle reflecting attachments to allow for more convenient viewing of a particular article, as well as internal light sources for illuminating the work area.

FIG. 1 is a perspective view of the measuring instrument of the present invention.

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1.

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 2.

FIG. 4 is a cross-sectional view taken along line 4--4 of FIG. 2.

FIGS. 5 and 6 are views through the viewing aperture of the instrument, illustrating a representation of an object during the measurement procedure.

FIG. 7 is a fragmentary plan view of the instrument shown in FIG. 1, further illustrating an attachment thereto.

FIG. 8 is an elevational view, partly in a cross section, of another embodiment of the instrument of the present invention.

FIG. 9 is a sectional view taken along line 9--9 of FIG. 8.

As shown in FIGS. 1-4, the instrument of the present invention is contained and supported within a suitable housing 10, which may have a removable top cover 12 to allow access to the interior.

Mounted at one end of the housing is a magnifying lens 14, preferably a 5x aspheric lens system, for magnifying the object to be viewed. The lens is preferably surrounded by an opaque side wall 16 to allow transmission of light from the interior of the housing toward the object. A suitable internal light source may be provided, such as the bulb 18 connected in a known fashion to a battery 20 and operated by a switch 22 accessible externally of the housing 10.

Mounted within the housing and behind the lens 14 is a series of equi-sized fixed mirrors 24, 26 and 28 (FIG. 2), the purpose of which are to reflect the magnified image from the lens onto a split mirror system, generally indicated at 30, and thence out of a viewing aperture 32 located behind and in direct alignment with the lens. The first fixed mirror is located directly behind the lens 14 and at a 45.degree. angle to the axis thereof, whereby the image is reflected from the mirror at a 90.degree. angle. The second mirror 26 is mounted out of the path of the lens 14 in rearward parallel relationship with the first mirror 24, whereby the image from the first mirror is reflected by the second mirror 90.degree. to the rear. The third fixed mirror 28 is located rearwardly of the second mirror and at an angle of 90.degree. thereto, and the split mirror system 30 is arranged rearwardly with the first mirror 24 in parallel with the third mirror. The three fixed mirrors 24, 26 and 28 thus serve to reflect the image back to the split mirror system 30, which is disposed at 45.degree. to the viewing aperture 32.

It will be appreciated that the fixed mirrors 24, 26 and 28 are utilized for convenience and serve to bend light around two corners of a square. This feature allows the viewing aperture 32 to be located in direct rearward alignment with the lens 14, allowing the user to face the subject being examined and giving the sensation that the image is moving in a straight path from the lens to the viewing aperture. Other mirror systems could be employed to allow viewing from any desired position relative to the lens.

The split mirror system 30 comprises a pair of mirror segments 30a and 30b which are contiguous and together define a mirror of the same size as the fixed mirrors. The lower segment 30a is affixed in the housing in parallel relationship with the third mirror 28. The upper mirror segment 30b is rotatable about a central axis from a position coplanar with lower segment 30a to positions at an angle relative to the lower segment. For this purpose, the rear side of rotatable segment 30b is affixed to a shaft 38 on the central axis of the mirror, said shaft being journalled at or near its free ends in the housing 10.

Means are provided for rotating the shaft 38 and the mirror segment 30b while at the same time indicating the degree of rotation. In accordance with the preferred embodiment, an external handle 40 is rotatably connected to the housing and connected by a motion reducing system to the shaft 38, whereby a relatively large degree of rotation of the handle is required to effect a small degree of rotation of the shaft.

As shown, the handle 40 is mounted near one end on a shaft 42 journalled through a wall of the housing 10 and terminating in a pinion 44. The pinion 44 is engaged with a relatively large diameter circular gear segment 46, said segment being affixed on its axis to the shaft 38. It may be seen that a relatively large rotation of the handle 40 and pinion 44 is required to effect a small degree of rotation of the shaft 38 and mirror segment 30b. As will be explained hereinafter in more detail, this feature in effect magnifies or multiplies the degree of movement of the mirror segment 30b, which is directly related to the measurement being sought, thus greatly increasing the accuracy of the instrument.

The other end of the handle 40 preferably terminates in a pointer 48 or other reference indicator, and a curved reference scale 50 (FIG. 1) is located therebeneath. The scale 50 may be applied to the exterior surface of the housing and may be divided into any desired units of measure. The handle 40 is arranged such that the pointer 48 slides or moves across the scale 50, with the radius of the circular arc of the scale corresponding substantially with the radius from the pivot of the handle to the pointer. The curved scale associated with the pointer allows the rotational angle of the mirror segment 30b relative to the mirror segment 30a to be read as linear units of measure.

The operation of the device shown in FIGS. 1-4 will now be described with reference to FIGS. 5 and 6. Assuming that the diameter of a pupil is to be measured, the instrument is positioned with the lens 14 facing the eye of the subject, and the operator views through the viewing aperture 32, corresponding to the views shown in FIGS. 5 and 6. The pointer 48 is placed in the zero position, under which condition the mirror segments 30a and 30b are coplanar. In such case, the outline of the pupil, indicated at 52, will appear as a circle that is bisected by the juncture line 54 between the lens segments.

In order to make the measurement, the handle 40 is rotated, causing the mirror segment 30b to rotate relative to the segment 30a. The handle is rotated until half of the image is split and moved its entire width, diameter, or length, as shown in FIG. 6, whereby opposite edges of the image coincide. The degree of movement required to move the image of the half segment along a distance of the length thereof is directly calibrated as a unit linear measurement on the scale 50, and corresponds to the length or diameter of the object being moved.

From the above, it may be seen that the amplified degree of movement of the handle 40 and pointer 48 is correlated directly to the degree of rotation of the mirror segment 30b relative to the segment 30a, which is in turn correlated to the width, length or diameter of the object being observed and measured. Although the operation of the instrument has been described as having a null or reference point as zero, it is obvious that the null point, i.e., corresponding to the setting in which the mirror segments 30a and 30b are coplanar, could represent any value on the scale 50, since only the degree of rotation is measured with regard to a reference point.

A contact lens measuring attachment for the instrument illustrated in FIGS. 1-4 is shown in FIG. 7 and is generally indicated at 60. The instrument described hereinbefore in connection with FIGS. 1-4 is intended to view vertical objects along a horizontal line with the instrument in a horizontal position. The attachment 60 allows an object to be supported horizontally and viewed and measured with the instrument in a horizontal position.

The attachment 60 comprises a housing that is attached or capped by means (not shown) over the lens 14. An upwardly facing reflective mirror 62 is mounted in the housing in front of the lens 14 at a 45.degree. angle thereto. The housing 60 includes a top wall 64 having a holder 66 with a dished-out well 68 therein for receiving and supporting a contact lens therein. The wall 64 and holder 66 are constructed of transparent material to allow the image of the horizontally supported contact lens to be reflected by the mirror 62 and into the lens 14, with the measurement being made by the same method hereinbefore described.

Another embodiment of the invention, particularly suitable for measuring the parameters of contact lenses, is shown in FIGS. 8 and 9. The device therein shown comprises a housing 70 having a side wall 72 with a curved scale 74 thereon and an upper transparent wall 76 bearing a lens holder 78. Mounted on the top wall is a secondary housing 80 containing a light source including bulb 82, battery 84 and external switch 86 mounted in the top of the secondary housing. An screen 88 is mounted in the housing between the bulb 82 and the holder 78 to diffuse the light from the bulb.

In the present embodiment, a similar handle 90 having a reference indicator 92 is utilized, one end of which is connected to a shaft 94 and gear system 96 similar to that hereinbefore described. The shaft 94 is secured to one segment 98a of a split mirror system, the other segment 98b of which is fixed at a 45.degree. angle relative to a magnifying eyepiece 100 located on the side of the housing. The mirror 98b is also arranged at 45.degree. to the holder 78 and to the lens contained therein, whereby the image of the lens is reflected by the mirrors 98a and 98b into the eyepiece 100.

The operation of the device of the present embodiment is similar to that previously described except that the series of fixed mirrors is eliminated and the object is measured at right angles to the viewer. In measuring a contact lens, for example, the lens is simply placed in the holder 78 and the distance between the whole image and the split image is measured on the scale 74 as a linear measurement.

It will be understood that various modifications, changes in design and other alterations to the embodiments described herein may be made without departing from the scope and spirit of the invention defined in the claims appended hereto. For example, although the instruments described herein are especially suitable for measurements relating to the eye and to contact lenses, it will be appreciated that the instrument could be easily adapted and used for making linear measurements of any object or image.