Sometimes our two eyes don't work properly in conjunction with each other. 'Orthoptics' is the study, diagnosis and (non-surgical) treatment of anomalies of binocular vision, strabismus ('squint') and monocular functional amblyopia. Its treatment involves the use of exercises, prisms or patching.

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All optometrists will encounter patients for whom orthoptic treatment would be beneficial, though only a minority will specialise in it. The College of Optometrists' Diploma in Orthoptics was the first postgraduate orthoptics qualification in the UK and one translation of the College motto, aequis oculis videre is 'to see with both eyes equally'. Nowadays there is also a separate specialised profession of orthoptists, most of whom are hospital-based. Their training route is quite distinct from that of optometrists.

Wheatstone-type stereoscope

Binocular vision

Binocular telescopes existed as far back as the 17th century but were never very common. Two spyglasses mounted together formed the basis of simple theatre glasses in the 18th and 19th centuries. The 'stereoscope' was named by Sir Charles Wheatstone in the 1830s and was originally an entertainment device for viewing stereo-pictures in 3D. The presence of such items in the parlour dictated their tasteful manner of manufacture, from materials such as gilded brass and polished walnut. Whilst some such devices descended downmarket and were used to view early erotica, other devices employed the same principles to either measure deficiencies in binocular vision or else train the eyes to work together better.


Squint in babies up to the age of four months is quite normal. Thereafter, children under three can have surgery to correct squint and restore 3D vision, the ability to perceive depth by merging images together from each eye.

Squint training mask 1583

Two famous images of a child's squint training mask appear in the Ophthalmoduleia by Georg Bartisch (1583). The one shown here is to correct a convergent squint by forcing the child's eyes to look outwards from each other.

Set of occluders

Next we show a set of spectacle frame-mounted occluders made of black plastic (including the 'Geno' Okluder at the bottom which was promoted in the 1930s as 'useful in all cases of strabismus...especially children'). Flesh coloured products were also available, which were theoretically less noticeable.


Doyne occluder 1933

Occlusion therapy ('Patching') has been the main treatment for amblyopia (which accounts for 90% of all child eyecare services work in UK) and is often popularly known as 'lazy eye'. It is possible to measure the number of patching hours to determine effectiveness of a dose. Our illustrated item is the 1933 model of the Doyne occluder. This was a trainer to combat lazy eye or squint and was for use behind a spectacle rim. There were three sizes, of which this is the large, and an option of a side ventilator. The product was available in the late 1930s from the Hamblin Catalogue and well into the post-war era too (Registered Design: 781961/33).


Many of the historic devices that follow perform many of the same functions or may be used in conjunction with one another or, indeed, other instruments and sets of stereo cards or everyday objects serving as fixation targets. Clinicians seeking more detailed information on how they were used in practice should consult one of the classic text books such as that by the optometrist Henry William Gibson FBOA, FSMC, Textbook of Orthoptics (1955). Gibson (d.1966) was Senior Staff Orthoptist and Lecturer in Orthoptics at the London Refraction Hospital (now the Institute of Optometry) from 1939-1962.


Worth-Black amblyoscope 1914

Amblyoscopes are fusion-training devices. In their simplest form they act like a stereoscope and the patient is able to view sets of card and fuse the images, for example by observing a parrot on one card to reside within a bird cage depicted on a card on the opposite side. Instead of moving a card bearing both images further away, the images are on separate cards that may be moved further apart. The best known instrument was designed by a Dr Worth with horizontal adjustment only. This training device was then modified by a Dr Black of Milwaukee to feature vertical adjustment too. One advertisement to be found in our collection, dating from 1914, declares somewhat misleadingly that 'it trains an amblyopic eye to see'.

Binocular Test of Cantonnet

Binocular test of Cantonnet

This binocular vision test from the 1930s, last used in the optometry school at Glasgow Caledonian University, was designed by Monsieur A. Cantonnet, an ophthalmic surgeon at the Laennec Hospital and Director of the Albert Remy School of Re-education. To British optometrists he is perhaps best known for having written the foreword to G. H. Giles' A Manual of Practical Orthoptics (1938). His system of 're-education' was introduced to Britain by Walter Green at the London Refraction Hospital. Cantonnet also co-authored the book Strabsimus with Filliozat. See also lower down this page for the Pigeon-Cantonnet stereoscope.


Diploscope cards

The memorable thing about this device was the 'DOG' card with which it was typically used. Some practitioners wrote out their own cards and an example is included here alongside the commercial printed version. The diploscope was an instrument designed as a test for binocular vision and muscle balance but found to be equally useful as a home training apparatus for adults and older children. If a patient was experiencing relative divergence that would cause the letters to be read as DOOG. Excessive convergence, on the other hand, would cause them to be read as OGDO. Suppression of left or right eye would cause, respectively, only DO or OG to appear.

Esdaile Turville Equilibrium Test

Esdaile-Turville Equilibrium Test

Newly designed in 1934 by A. J. Esdaile (who sadly died that same year aged just 58) and A. E. Turville, this was advertised as 'A simple piece of apparatus to test refraction balance'. There are two pupillary distance scales, for use depending upon whether the chart was held at 40cm or 33cm from the eyes.

Freeman OMIS (Ocular Muscle Imbalance Screener) Near Unit

OMIS prototype head

This prototype for a muscle balance test by Keeler Instruments Ltd consisted of a rectangular plate fixed into a black plastic hand-held bulb unit. The plate featured a rectangular red border and a green dot placed within to one side. The patient would have viewed the plate through red/green spectacles. The green dot might have moved and the red border 'floated' if the muscles of the eye were not balanced. In extreme cases the dot may have appeared to move outside of the rectangular border altogether. This pre-production instrument is part of the Harry Freeman Archive which includes several uncatalogued files of information about this prolific optometrist's inventions.

Giles Three Needle Test

Giles Three Needle Test

The BOA's own baby, this device invented by George Giles was to measure stereoscopic acuity. The intention was that the patient held the device up to his or her own face whilst the optometrist/orthoptist moved the centre needle to and fro until the patient perceived the three needles to lie in the same plane. The patient's view was concentrated through a letterbox-type frontal mask. Our museum's version of this test appears to have been modified in that it is the outer two needles that move and it seems to have been set up so that the patient did the moving.

Maddox Wing Test

Maddox Wing Test

The Maddox Wing Test was invented by the ophthalmic surgeon Ernest E Maddox (1860-1933), a specialist in squint. It may be described as a heterophoria test and numerous versions have been manufactured since its invention in 1913 up to the present day. It is a quantitative and subjective method of measuring the size of a strabismic deviation by dissociation of the eyes brought about by two septa which are placed in such a way as to present fields to either eye separated by a diaphragm at the centre. The right eye sees a red and white arrow, each of which point to a scale with numbers seen by the left eye; the red arrow points to the vertical red scale and the white arrow points to the horizontal white scale. A third arrow located to the right and below the horizontal white scale is used to measure torsion. The Maddox Wing measures the size of heterophorias (latent deviations) and small heterotropias (manifest deviations) at near when normal retinal correspondence (NRC) is present. It is especially helpful when patients present with symptoms of diplopia (double vision) with no apparent cause. It is generally used in association with a number of other tests before a full diagnosis is determined. Near-constant features include a card holder, a septum, a fixed right eye occluder in the form of an angled bar, a binocular eyepiece (with or without drop cells for trial lenses) and a hinged torsion lever with pointed end. Many also have a folding handle to make the instrument easier to store or carry in a domiciliary case. The instrument's simplicity is its greatest strength. Ignoring possible accessories, it contained no lenses or prisms, so that natural conditions were interfered with as little as possible.

Pigeon-Cantonnet Stereoscope

Pigeon Cantonnet Stereoscope

One of the most distinctively named ophthalmic instruments, this was primarily a home trainer for patient exercises but could also be used to examine for and demonstrate simultaneous vision for either colour or form. It folded flat for ease of portability and was made of lightweight black cardboard. It comprised two outer flaps bearing scales and a pointed central flap held upright by a cord which acted as a septum. This also contained a covered mirror. It was used in conjunction with coloured objects (usually pictorial cards), dull objects (a copper coin was recommended) and recognisable shapes (such as a card bearing a letter U). To add entertainment value it was possible to play snap or noughts and crosses whilst using the device, or to conduct a tracing exercise using drawing paper.

Remy Separator

Remy Separator

A very simple form of device comprising a twin card holder with septum and handle. Its method of use always involved tilting the distal end upwards or downwards depending upon whether esophoria or exophoria was being treated.

Rosen Foriagraph

Rosen Foriagraph

Surviving examples of this device are often missing their coloured filters. A small red spotlight was situated in the centre of the scale and an eye looking through the red filter would see only this light and an eye looking through a blue/green filter see only the scale. A patient with heterophoria would see the spotlight apparently out of position and this could be plotted on the scale. The device only functioned correctly if held constantly at the exact distance of 33.3cm away.

Turville Near Balance Unit

Turville Near Balance Unit (NBU)

This device, also called the Turville Near Reflector (TNR), was for testing visual and other binocular functions from a distance of circa 37cm. Our example was manufactured by Barr & Stroud in Scotland, but more than one Glasgow firm put its name to examples. The 1969 Patent No. 1155597, originally taken out by Scott & Madill Ltd with reference to the apexed mirror, applies. The price of the instrument in the mid 20th century was £37.10.0. including one set of eight test cards.

Worth's 4-Dot Binocular Vision Test

Worth 4 Dot Test

Finally a note of warning...prototypes (or for that matter instruments supplied to the market for professional use) have not always been sophisticated. This hand-held near vision test is in fact an 'Ever Ready' bicycle lamp battery pack with four colour filters mounted. (One white, one red, two green). The patient would have been asked to hold the test unit at reading distance from his or her face.

Worth's test was invented in 1903 but the hand-held version appeared in 1955 when AIM was the first company to convert a bicycle lamp. Clement Clarke supplied the pictured version of this instrument with two hoods (the Worth 4-dot and a duochrome test). The patient would hold the instrument at the reading distance whilst wearing diplopia goggles. Correctly set-up, the 4 dots are in diamond formation with red at the top, white below and green lateral filters. A patient wearing a red goggle over the right eye would see all four lights if possessing binocular vision or five (!) if diplopic. Rotating the hood served as a malingerer's test.