CA1246917A - Visual accommodation trainer-tester - Google Patents

Abstract

Invention Abstract The invention is all apparatus for training of the human visual accommodation system. Specifically, the apparatus is useful for training a person to volitionally control his focus to his far point (normally infinity) from a position of myopia due to functional causes. The functional causes could be due, for example, to a behavioral accommodative spasm or the effects of an empty field. The device may also be used to measure accommodation, the accommodation resting position and the near and far points of vision. The device comprises a number of optical elements arranged on a single optical axis (74). Several of the elements are arranged in order on a movable stage (20) in fixed relationship to each other: a light source 30, a lens (32), a target (36), an aperture (42), (48) or (52) and second lens (58). On base (18) and in fixed relationship to each other are eyepiece (70) and third lens (64). Stage (20) generates an image (72) of target (36) and the stage is movable with respect to base (18) by means of knob 22. The device is utilized for the various training and test functions by following a series of procedural steps, and interchanging the apertures as necessary for the selected procedure.

Description

~;~4~
~AS~ CASE NO. ARC-11426-1 3 VISUAL ~CCO~OD~TION TR~INER-TESTER

s Baekqround of the Invention 12 1. Field of the Invention 1~
14 This invention relates to a device for the training and measurement of the human visual accomrnodation system.

17 ~ccornmodation is the automatic adjustment of the eye for seeing at different distances and is effected by 18 changes in the convexity of the crystalline lens.
19 Specifieally, the device is a training aid for teaehing subjeets to relax the eye museles which are used to 21 foeus a sharp image on the retina of the eye and to

2 instead foeus at infinity. This is called relaxation

3 of aeeommodation.

225 2. Deseription of the Prior ~rt 27 A normal, or emmetropie, eye will foeus light rays from 29 a distance on the retina by means of eomplementary deflections of the cornea, crystalline lens, and fluid of the eye. Li~ht rays re~lected from a distant object 31 (beyond 25 feet) are considered to bf~ paralLel. With a 32 nearer object, how~ver, the reflected rays tend to 343 diverge so that unless some correction is made, the rays will not focus on the retina. The correction is known as accommodation and is achieved through 36 alteration of the anterior lens surface curvature by action of the ci1iary musc1e so tha~ a retinal focus is . ~,3 , . . .

1 obtained. It is often necessary or desirable~ for both 2 medical and research purposes, to cause a person to 3 relax his eye accommodation, that is to focus on a plane as far distant as possi~le, theoretically at infinity for a normal eye. Perhaps a most common 6 instance when relaxation of accommodation is desirable 8 is when an ophthalmologist examines a patient to 9 determine whether or not he needs glasses. ~he ophthalmologist accomplishes this by using drugs to 11 paralyze the eye muscles which control the eye lens or 12 by chan~ing a series of glass lenses in front of the 13 patient's eye~ using a technique called "fogging."
14 Thus, one objective of an ophthalmologist is to prescribe glasses which allow the patient to see far-away objects clearly, provided his accommodation is 16 fully relaxed. In order for the ophthalmologist to do 17 this, the accommodation must first be fully relaxed 18 before refraction measurements are taken.

~ccommodation relaxation can be important for a number 21 of purposes other than just determining prescriptions 22 for glasses as the inventor has discovered.
243 There are many situations where keen distant vision is very important~ For example, it is necessary for all 26 pilots to be able to p~rceive the existence of other aircra~t in the airspace immediately ahead of their 27 aircraft. Addition~lly, military pilots need to be able to detect other aircraft and identify them as 29 friendly or hostile at the farthest distance possible.

31 ~ need has developed for a device to train one to 32 overcome empty field myopia and to provide therapy for 33 behavioral myopia. Some past optometers employed such 34 complex electro-mechanical systems that their operation was beyond nearly all people except the originators.
36 For example, when the Cornsweet and Crane optometer, 37 citation below, was turned over to a skilled Covernment sc1aDtist, it ~ok thc scientist ove~ two mollths of .. . . , . . ~ .

~ 2~

1 concentrated study and practice to even make the device 2 work with modest success. If training human visual 3 accommodation is ever to have wide application and become a real social benefit then a really practical, 6 simple and inexpensive device must be provided.
7 Accordingly, it is an object of the present invention 8 to provide a device that is economical to fabricate, 9 simple to operate, maintain, and transport that will:
train the human visual accommodation system 11 independently of other visuo-muscular systems; provide 12 an accommodation stimulus and measurement tool in 13 vislon research; measure the accommodation resting 14 position and thc visual near and far points.

There is no known prior art device capable of 16 performing all o~ these functions let alone one that is 18 simple to operate and economical to construct. An 19 exemplary prior art relaxer is disclosed in U.S. Patent No. 3,843,240 wherein a defocused flashing source of 21 light is viewed through a pin-holc aperture to produce 22 relaxation of the eye's accommodation powers. U.S.
~23 Patent No. 1,475,698 issued to ~-lenker shows an 24 apparatus for the objective measurement of the refractive value of the principal point of the eye.
26 U.S. Patent No. 3l602,580 pertains to a method and 27 apparatus for simultaneously refracting both eyes of a 28 patient wherein a narrow beam of light is directed into 29 each eye at a point spaced from the optical axis of the eye. ~n optometer of the Scheiner type is revealed in 31 U.S. Patent ~o. 1,235,170 issued to Thorner.
32 Expensive, servo-control]ed optometers that are lar~e, 33 complex and difficult to use are mentioned in the 34 following publications: Servo-Controlled lnfrared Optometer, Cornswe~t and Crane, Journal of the Optical 36 Society of ~Merica, Vol. 60, No. 4, ~pril 1970, pp.
~7 548-554; Volitional Control of Visual Accommodatiorl, R.J. ~andle~, AGARD Conference Proceed~ngs No. 82 on ~ 3~lt~

1 ¦ Adaptation and ~cclimatisation in ~erospacc Meclicine, 2 ¦ September 1970; and Accurate Three-Dimensional 3 ¦ Eyetracker, Crane and Steele, Applied Optics, Vol. 17,

4 ¦ March 1, 1978, pp. 691-705.

5 l 7 ¦ Summary of Invention ¦ The present invention is an apparatus for training the 8 ¦ human visual accommodation system, for measuring the 9¦ accommodation, the accommodation resting position, and 10l the visual near and far points. The training of the l visual accommodation system is accomplished through a 121 defocus feedback that is external to the natural, 13 ¦ blurred-retinal-imaye feedback loop. The apparatus 141 employs very few components and is very easy to use.
151 The apparatus comprises a sta~ionary base with a 16¦ movable stage mounted on one end of the base. Five 171 elements are mounted on the movable sta~e: a light 181 source mounted at one end of the stage; a target l mounted at the middle o~ the stage; a first lens 201 mounted on the stage betweerl the light source and the 21¦ target; a second lens mounted at the opposite end of 2221 the stage; and a plurality of apertures are mounted on 3l the stage between the second lens and the target. ~n 241 eyepiece is mounted on the opposite end of the base;
25¦ ancl a third lens is mounted on the base between the 261 eyepiece and the second lens. The elements of the 271 invention mounted on the Movable stage are all in fixed 281 relationship to each other ancl in movable relationship 301 to the third lens arld the eyepiece.

31¦ Brief Description of the Drawillgs 321 The invelltion will be more fully understood ~rom the 33 following detailed description taken in conjunction 36 with the accompanying drawings in which:
37 1 ~ URE 1 15 a persl~ect1ve view of the invDnti~n.

~ 7 l -5-2 ¦ YIGURE 2 is a schematic diagram showing the elements of 3 ¦ the invention and the location of the image of target 5 l

6 I Detailed Description of the Invention

7 I Figure 1 sho~s a presently preferred embodiment of the

8 ¦ invention for laboratory use, designated generally by

9 ¦ the numeral 1~. In the center o~ the iigure is shown a I stand 12 haviny a rod 14 extending upward vertically

10 ¦ from a base 16. Attached to the top of stand 12 is a 112 ¦ base plate or rail 18, Mount~d on one end of basc 13 I plate 18 is movable stage 20 which is driven by means 14 ¦ of a rack 24 and pinion gear [not shown). Rotatable 15 I knob 22 is couplet3 to the pinion gear. Stage 20 may be 16 ¦ moved toward or away from eyepiece 70 on base plate 18 I by rotating knob 22 clockwise or counter-clockwise. A
17 ¦ diopter and/or distance scale 23 is affixed to basc 18 13 ¦ adjacent to rack 24 as for example by etching or 20 I painting. Scale 23 i5 read by using the edge 25 of I stage 20 as a pointer.

¦ A number o~ elements of the invention are all mounted 2243 ¦ Oll movable stage 20 in fixed relationship to each ¦ other. Vertically adjustable rod 26 affixed to stage 251 20 supports r~ctan~ular ~ox 28 wl~icl~ contairls .l light 261 source 30 and a ~irst lens 32 mounted in holder 34, 22871 target 36 is situated on end 38 of box 28, The target 291 may transmit llght therethrough from light source 30 301 with the area adjacent thereto being opaque or vice 311 versa, End 38 of bo,~ 28 may be, for example, a 321 photoyraphic transparency with ~ desired image 33 ¦ centr~lly positione(3.

34 ¦ Mounte~ on v~rtically adjustable stand 40 adjaccnt to 36 1 target 3~ is a "wi~e op~n" aperturc 42 about 8 mm in ~7 1 diameter. Tllc aperture is positioned so that the optical a~is ï4 of Lells 32 alld t:he other lenses passes ~ 6~9~7 1 centrally therethrough. ~pertures 48 and 52 supported 2 by pivotable arms 50 and 5~, re-cipectively may be moved 3 onto the optical axis 74 by means of high speed 4 solenoids 44 and 46, respectively. Aperture 48 is a "pinhole" aperture with an orifice o~ approximately 0.3 6 inm in diameter, whereas aperture 52 is a "Scheiner"
7 aperture having two orifices about 0.5 mm in diameter, 8 separated by 3.0 n~. When solenoi~ 46 is actuated, aperture 52 is moved to the position where the optical 10 axis 74 bisects the two orifices. Apertures 42, 48 and 1 52 are not depicted to scale in Yig. 1. Whcn the 1 device is in use there is either one aperture on the 13 optical axis (42) or two (42 and 48, or 42 and 52). ~s 14 it is intellded that aperture 42 be larger than aperture 48 or aperture 52, there is only one effective aperture 16 on the optical axis at any given time (the smaller one). A switching circuit 78 (see Fig. 2) housed in 18 cabinet 31 energizes solenoids 44 and 46. Specically, 19 the switching circuit provides these selectable modes of operation:

1. The en~rgi-~ation of solenoid 44 to move 23 apeLture 48 to the o~tical dXiS 74.

6 2. The energization oL solenoid 46 to move 2 aperture 52 to the optical axis 74.

28 3. Th~ automc~tic alterna~e energization of the solenoids so tha-t apertur~s 48 and 52 are alterrlately on optical axis 74. In this mocle, 31 it is pre~erable ~lat ~he switching circuit 333 include a user-selecta~le timillg circuit so -that the "on-axi:i" intervcll o~ aperture 52 rmay 34 be varie~.

36 Cabinet 31 also IlOUSeS a power supl-)ly to provi~e pow~r 37 l~mp 0.

1 The orifices of Scheiner aperture 52 are covered with 2 different colored filters 75 and 76, respectively.
3 These filters may be, for example, red and green.
These filters provide a cue for the direction of defocus when the image is split. On thc proximal end 6 of stage 20 is mounted a vertically adjustable stand 56 7 with second lens 58 and lens holder 60.

9 On the proximal end of rail 18 is a vertically adjustable stand 62 which supports lens holder 66 and

11 third lens ~4. ~lso attached to stand 62 is a brackF-t

12 67 supporting eyepiece 70.

13

14 Figure 2 shows the preferred spacirIg of certain items in the trainer-tester. Back-lighted target 36 is a l7 fixe~ distance from second lens 58, twice the focal 18 length (f) of lens 58. An ima~ 72 of target 36 is formed the same distance on the other, left, side of 19 lens 58. Of course as stage 20 is moved with respect to base 18 by means of knob 22, image 72 is moved with 21 respect ~o stationary third lens 64. ~yepiece 70 is 222 situated one foccll len~th from third lens 64 and lamp 3 30 is spaced one focal length from first lens 3~. l`IIc 24 field of view of the target is determined by the size of the aperture 42, 48 or 52 arId the distance of the 227 tàrget from the aperture. IJith the aperture diameters 28 mentioned above and if lens 58 has ~ focal len(3th of 10 centimeters, for example, there will be suEficierIt 29 field of ~iew available to stimulate a larc3e portion of the retina of the viewin-3 e~e 79 and thus, a lull 31 accotnmodation response.

33 The several modes of operation o~ the apparatus will 34 now be des(:ribed.
3.
36 Measurement of the I'ar I'oint of Vi;ioTI

37 _ __ 1 The vision far pOillt (punctum remotum oE accommodation) 2 is defined in the Dictionary of Visual Science, 3 Schapero, M., et al., Chilton Co., Phila., New York, 4 1960 a~:

61 The conjugate focus of the retina (fovea~ when the 71 accommodation is relaxec3 or at its minimum. In 81 emmetropia, the far point is said to be at 9 infinity; in myopia, it is at some finite distance in front of the eye; in hyperopia, it is at some 11 finite (virtual) distance behind the eye.

13 ~hat needs to be determined, therefore, is the optical 14 distance from the subject's eye, at, and beyond which, the image of target 36 can no longer be kept in focus, 16 i.e., wllen accommodation is fully relaxed. If the 17 point at which the image can no longer be kept in focus 18 is in front of the focal plane 80 of lens 64 the far point is closer than infinity and the eye is said to be 21 myopic or "near-siyhted." On th~ other hand, if the point is behind focal plane 80 (to the right of the 2 plane in Fig. 2~ the far point is said to hyperopic, 23 (hypermetropic) or "far-sighted." If the point is 24 right at the focal planc 80, the eye is then deemed emmetropic (normal).

28 For the measurement of the far point of vision the subject is preferably seated in front of device 10 with 29 the entrance pupil plane of one eye placed at the eyepiece 70. The lamp 30 is illuMinated and the 31 wicle-open aperture 12 is in place on optical axis 74.
32 ~n image oE target 36 is found at 72. Tllis image is 33 the object Eor lens 64 and the eye, and thus ~ecomes the visual stimulus for the eye. l'he position of stage 20 is de-termilled by the rotation of knoh 22 WiliCh in 36 turn cletermines the position 01 tlle .~ul~ject's stimulus 37 with respect to lens 64.

1 ¦ To star-t the measurement process the stimulus is 2 ¦ initially placed by the examiner between lens 69 and ¦ focal plane 80. This requires the subject to exert 5 ¦ some accommodative effort, an amount that is dependent 6 I upon where the stimulus has been placed with respect to 7 I lens 64. The scale 23 imprinted on base 18 and 8 ¦ corr~sponding pointer (proximal end of stage 20) 9 I enables the measurement of the diopter valu~ of power ¦ required at the eye to focus the stimulus (image 72).
10 ¦ For convenience, scale 23 may also include a vision distance scale in addition to the dioptric scale to 131 save the exaMiner the time needed to make the 14 I conversion from diopters to distance. The subject is I requested to rotate the knob 22 to move the 151 accommodation stimulus toward focal plane 80 and to 171 stop the movement when the stimulus first appears to 181 blur. When the blurring first occurs the point or 19¦ scale 23 alignecl with the pointer is read.

20¦ Because of the hi~h variability in biological response 211 systems, it is prefcrable to measure the ~ar point by 231 approaching it from both directions and then taking the 241 average reading after several trials. That is, the 251 subject moves the stirnulus away from lens 64, from a 261 position set by the examiner, until the stimulus blurs, 271 the examiner reads the scale, the subject rnoves the 281 stimulus, from a position selccted by the examiner, 291 towards lens 64 until the blurring of the stimulus 301 ~tops, and the examiner reads tl-e scale. This cycle is 311 repeated for as many times as is deemed appropriate by 321 the examiner and an average value of the dioptric 33 1 distance is computed. This mecln dioptric distance is 34 1 the refractive error o~ the eye under test, and when 35 1 converted to distance (throu~ll scal~ 23 or a simple 36 ¦ calculation) is ~lle rnonocula~ l`ar point of vision of 37 ¦ that cye.

1 Meclsuremen~ o~ the Near Point of Vision 3 The Dictionary eited above def ill2S the accommodative 4 near point (punctum proximum) as:
s 6 The point representing the maximum dioptric 7 stimulus to whieh the eye call aeeommodate. ~lenee, 8 usually the nearest point anteriorly on whieh tile 9 eye can focus, 11 The measuremen~ proeess for determining the near point 12 o~ vision is quite similar to the previous process.
13 The measurement begins when the examiner, using knob 14 2~, plaees the stimulus between lens 64 and focal plane 80. The subjeet then uses the ~nob 22 to move stage 20 16 and stimulus 7~ toward him -thu~ inereasing the 17 ¦ aeeommodative power required at the eye at ~yepiece 70 18 ¦ to focus the stimulus. ~Jhen the stimulus first starts ¦ to blur, the subject stops the movement of the stage 20 21 ¦ and the examiner notes where the pointer has stopped on 22 I seale 23. The braeketincJ proeedure used above is also 23 I pre~erably employecl here. In accordance with that l proeedure the examiner places the stimulus close to 224 ¦ lens 64 such thclt it is too close to be foeussed and 26 I will be o~servecl as blurrecl, The subject thell mc)ves 271 the stage 20 away ~rom him un~il the stimulus first I appears in focus. When the movement is stopped, the 29 ¦ examiner reads sc,ale 23. This hlurrincJ and elearing l tapproaehing and reeeding stimulus) proeedure is 301 repeated as many times as is eonsldered neeessary by 31 the exarminer alld a mearl value of the several scale 333 l readings is ealculaL~cl. This averclge value of l aecommodatioll, when collverted to distance from 3~ 1 diopters, is tlle monoeular near point of ViSiOII of tllat 37 e e, 1 ¦ lt is well ~nown ~h~t .1~ a visual stimulus approaches ¦ the eye the pupil decreases in si~e as accommodation 3 ¦ increases. The decreased pupil size causes increased 4 ¦ depth of field and facilitates accommodation. This 5 ¦ often results in a lazy or laggirlg response which cloes 6 ¦ not necessarily indicate the true capability o~ the 7 ¦ visual neuro-muscular system. To insure that the full ¦ accommodation range of the subject will be tested, the 9 ¦ examiner may dilate the subject's eyes with a 10 ¦ mydriatic. The mydriatic keeps the pupil large, 11 ¦ deprives the eye of great depth-of-field, and fully 12 ¦ taxes the accommo~ation capabilitiesO
13 l 14 ¦ Normally a defocused image is a blurred image.

15 ¦ However, if an optical aperture having two laterally

16 ¦ displaced orifices is placec] in front of a lens, a

17 ¦ single image of a point (or ~x~ended) source will be

18¦ formed in a plane Oll the other side of the lens, 9 ¦ coniucJat? to the object; all other planes are not 20 ¦ conjugate to the object--they are defocused--so two 21 ¦ imacJes of the source will be ~ormed. Ilhese images will 22 ¦ be separa~ed by a distance dependent upon the distance 23 ¦ between the two small apertures and the distance of the 241 images from the conjugate plane. ~etween the conjugate 251 plane and the lens each image will lie on thc same side 261 f the optical axis as the aperture which formed it; on 71 the side of the conjugate plane away from the lens each 281 image will lie on the opposite side of the optical 291 axis. Such a two-orifice aperture is known as a 301 Scheiner aperture.

33 1 ~or measurinc3 bc,th l-he near point ~nd the Ear pOillt, l the Scheiner aperture 5' may be usecl instead of, or 34 ¦ alternately, with the wide open aperture 42. When 35 1 aperture 52 is moved to the opticcll clXiS 74 by means of 36 1 solelloid 46, the subject sees a sinc31e tar~et image 72 37 o ly when it 1~ ill focu~; tl~e ~eLina is con juy~te to i ? ~

2 72. I~lor other situations, namely when image 72 is 3 ¦ defocused, the~ ~yc at eyepiece 70 observes two 4 ¦ displaced ~arget imacJ~s, each a different color (based 5 I on the colors of filters 75 and 76)o The separation of 6 ¦ the imacJes is a function of the amount of defocus. It 7 I is easier for tll(? subject to distinquish two displaced 8 ¦ and different colored images th..n defocus blur oE on~
9 I irllage so greater accommo~lation measurement accuracy can ¦ be ~xpected wherl aL~erture 52 is used for -~he near and 10 ¦ far vision measurements.

121 l 13 I Measurement of the Restinc~ Position 15 I ~hen the eye has great depth-of-fi~ld, a position of 16 ¦ tonic equilibrium occurs between the sympathetic and 17 ¦ parasvmpathetic nervous systems and the eye is saicl to 18 I be at the resting position. I'he phenomenon, also 191 called empty Gr dark~ field myopia, is ~n unconscious 201 process an~ the restincJ position is almost never at 211 infinity focus. Ernpirical stuclies indicate that normal 22¦ eyes focus, On the avs?ra-Jc, about onc~ Meter in fron~ of 23l the eye. For a compreilc-~rlsive study see, "'l`he Dark 2~1 Focus of ~ccomnlodation: Its Exis~ence, Its Measurement, 2sl Its Ef~ects," Nich~lcls ~. Simonel]i, AFOSR Technicc l Repor-t Bel-79-3/~FOSR-79-7, prepared by the Bellavioral 261 Engineering l,aboratory, New ~exico State University, l Novernber 1979.

301 llerein the eye is made to settle to its restirlg 311 position by removinc3 the clefocus blur accommodation 32¦ retinal stirnulus. Tllis is accomp1ished by placing 33 ¦ pinhole aperture 48 on optica1 a~is 74 by means of 34 solenoid ~4. 'l'he aperture increases thc depth-of-l~ield so much that no stirnulus blur is apparent to the eye 36 I ~dor test ! ~ '7 1 ¦ In accordance with this measurement, lamp 30 is 2 ¦ illuminated, ap~rture 48 is initi~lly placed on optical 3 ¦ axis 74, the subjec~'s eye to be tested is placed at 5 ¦ eyepiece 70, and the subject's other eye is occluded or l covered. Staye 20 is moved so that stimulus 72 is 61 positioned at the subject's prcviously measured far ¦ point and the subject is allowed a reasonable time for 81 accol~nodation to settle (more ~han one minute). After 9 ¦ sufficient time has been allowed for settling, solenoid 101 44 is de-energized moving aperture 48 off of the 11 ¦ optical axis and aperture 52 is moved thereon by l solenoid 46. After an interval shorter than the 13 ¦ accommodation latency period, about 250 milliseconds, 14¦ aperture 52 is removed from optical axis and aperture 151 48 is returned to it. During the brief period that 161 aperture 52 is on the optical axis, the eye under ¦ measurement will observe -two displaced images, each 18¦ differently colored, if the eye has drifted to its

19¦ resting position. This is arl easy pattern to discern

20 ¦ even during the brief period that aperture 52 is on the

21 ¦ optical a~is.
2 l 23 ¦ ~t regular intervals aperture 52 is brough-t back to the 241 optical axis for a brief period while aperture 48 is 25 I moved to its off-axis pOSitiO~ s the alternation 26 ¦ occurs, the subject is directed to move st~ge 20 in a ¦ direction that will cause the two colored images to be 28 ¦ superimposed. l`he correct direction to move the stage 29 ¦ will be immediately apparen-t to t:he subject becau.s~ of 30 ¦ the orientation of the two colored images. When the 31 ¦ images are superiml;osed and th~ sta~e is brouyht to 33 ¦ rest, the pointer for scale 23 indicates the empty 34 ¦ field myopia, that is, the resting position of the eye.

36 'r ~Lni 1 The subject invention has three salient visual 2 accommodation training fea-tures: (1) It can open t}~e 3 accommodation loop (nullify defocus blur) to allow 4 volitional control to be brought into playj (2) It can provide a defocus cue (feedback) that is not normally 6 available in real world visual tasks; and (3) It allows 7 accommodation to be decoupled from binocular vergence 8 by using only one eye, thus limiting it to a more pure 9 accommodation response. Inasmuch as willed control is initiated and completed in higher neural centers than 11 at each individual eye, both eyes benefit when only one 13 eye is trained.
14 The subject invention is so versatile that it permits many strategies for training the volitional control of 16 accommodation. Hereinafter is but one training 17 strateg~, that of volitionally controlling one's focus 18 to one's far point (normally infinity) from a position of myopia due to functional causes. The functional causes could be due, ~or example, to a behavioral 21 accornmodative spasm or the effects of an empty field.

22 Oth~r strategies will be apparent to a skilled clinician.

To implement the training, the device 10 is operated as 26 it is for the m~asurement of the resting position and 228 the subject's eye not in the eyepiece is either 29 occluded or coyered. As aperture 52 is periodically and briefly positioned on optical axis 74 (alternately with aperture 48), the subject is instructed -to not 31 touch knob 22, but to exert volitional con~rol on the 3332 eye so as to fuse together the two differen~ colored images. ~fter some pr.lc~ice, tr.linees can lealn ilOW to drive their accommodation in the appropriate direction to achieve the ~u~erir~ ositi~ll o~ images. It is not known how this is accomplished nor have~ users o~ the 37 device un able to explain llow ~l~ey fu~e the ima7e~. 1 Il ~Z4tj~'7 ~ -15-1 ¦ Sorne trainees have been ablc to achieve the task ~Jith 2 ¦ as little as one hour of training. After some practice 3 ~ and reinforcemellt a trainee is weaned from the device 4 ¦ and can utilize the new accor.~odation skill in the real 5 ¦ world. To enhance th ? training and make it possible6 ¦ for the trainee to alternately view real world objects 7 ¦ and stimulus 72 without leaving eyepiece 70, a 50/50 - 8¦ beamsplitter may be added to the apparatus. When the 9 ~ beams~litter is add~d, the ey-~piece is rot~ted 90 10¦ degrees so that its viewing axis is orthogonal to 11¦ optical axis 74. The beamsplitter is placed where the 12¦ two axes cross. Thus, the subject may either look 13¦ throu~h the beamsplitter at th? real world or look on 14¦ the beamsplitter for stimulus 72. When operated 151 thusly, neither eye is occluded, binocular viewing is 161 in force, and binocular accommodation is measured.

18¦ The componénts of the instrument need not be supported 19¦ on tall stands or on a ba~e a~ large as 18. The 20¦ instrument may be repackag~d in a much smaller- volumeO
211 It is possible, for instance, to helmet-mount ~he 2~1 device for dynamic studies in piloting aircraft, 231 driving cars, o~erating computer terminals, and other 241 human engineering investi~ations without intervention 25¦ in the on-going visual task.
~6l 271 The advantage of this invention over present day 2~1 devices is that it brings together multiple 291 accor.~modation measurement/training ~eatures in one 301 instruroent that is easy to operat~ and economical to 31¦ construct. This invention combines in one ophthalmic 321 instrument a device for: (a) traillirlg the human visual 33 1 accommoda-tion system incleperl~ently of other 34 1 visuo-muscular systems; (b~ measurillg the visual near 35 1 and far points; (c) measuring th~ accommodation resting 36 position; and (d) use as an accommodation stimulus and ~7 measur ment device in vision rosearcll

Claims (9)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An apparatus for training and measuring the human visual accommodation system comprising:

a base;

an eyepiece and a stage mounted on opposite ends of said base;

a first lens mounted on said base between said eyepiece and said stage;

means for moving said stage toward or away from said first lens;

a plurality of elements mounted on said stage in linear optical alignment comprising:

a light source mounted on the end of said stage farthest from said first lens;

a target mounted on said base near the middle portion of said stage;

a second lens mounted on said stage between said light source and said target;

a third lens mounted on the end of said stage nearest said first lens whereby an image of said target is produced between said first lens and said third lens and said image is moved with respect to said eyepiece when said stage is moved;
and a plurality of interchangeable apertures mounted on said stage between said third lens and said target.

2. An apparatus as set forth in claim 1 wherein said light source and said second lens are enclosed within a chamber and said target comprises a portion of one wall of said chamber.

3. Apparatus as set forth in claim 1 further characterized by having a diopter readout to show the relationship between the movable stage and the first lens.

4. The apparatus of claim 1 wherein said light source, first, second and third lenses and said eyepiece are aligned on a single optical axis and wherein only only aperture is effectively on said optical axis at any given time.

5. The apparatus of claim 4 wherein said aperture is at the focal plane of said third lens, said target is two focal lengths from said third lens and said target image is two focal lengths from said third lens and between said first lens and said third lens.

6. The apparatus of claim 1 wherein said interchangeable apertures comprise a wide-open aperture, a pinhole aperture and a two-hole aperture.

7. The apparatus of claim 6 wherein each hole of the two-hole aperture is covered by a different colored filter to provide a defocus cue.

8. Apparatus as set forth in claim 6 wherein means are provided for moving at least one of said apertures on and off of the optical axis.

9. Apparatus as described in claim 6 wherein means are provided for alternately positioning the pinhole aperture and the two-hole aperture at the optical axis.