A Brief History and Summary of Stereoscopy in Medicine

written by Lindsay Cole, Canada


In life, most humans see the world from two dis­tinct view­points: one from each eye.  The left eye receives an image slight­ly dif­fer­ent from the right eye because it is focus­ing on the object of inter­est from a slight­ly dif­fer­ent angle.  The brain uses these dif­fer­ences to per­ceive depth.

The term ‘Stere­oscopy’ refers to what is now more wide­ly known as 3D imag­ing, i.e., record­ing and pre­sent­ing visu­al infor­ma­tion in three dimen­sions.  When a stereo­scop­ic image is viewed prop­er­ly, the brain per­ceives depth as it would in the phys­i­cal world.  Thus, a flat paper or screen can car­ry spa­tial infor­ma­tion. This sim­ple con­cept can be adapt­ed into draw­ing, pho­tog­ra­phy and video for true 3D visualization. 

Charles Wheat­stone dis­cov­ered the con­cept of stere­oscopy and built the first view­ing devices in 18321.  By 1852 the Brew­ster-type stere­o­scope was pub­licly avail­able1.  This hand­held device allowed the com­mon indi­vid­ual to view side-by-side (SBS) stereopho­tog­ra­phy for­mats and helped incite the great pop­u­lar­i­ty of stere­oscopy in the mid 19th cen­tu­ry1.  Though this pop­u­lar­i­ty increased and decreased through­out the decades, the con­cept was con­tin­u­ous­ly applied to a vari­ety of prac­tices includ­ing art, film, pho­tog­ra­phy, his­to­ry, and medicine. 

In the present day a vari­ety of view­ing devices exist.  Polar­ized light pro­jec­tion and fil­tered glass­es allow both left and right eye images from one screen.  It is cur­rent­ly wide­ly used, and known to the gen­er­al pub­lic via 3D movies.  SBS stereo images can also be “free-viewed” by those indi­vid­u­als who have trained their eyes to diverge on the page: each eye focused on its cor­re­spond­ing image.  This easy access allows the visu­al­iza­tion of true 3D depth, as it is nat­u­ral­ly per­ceived by the brain, for a vari­ety of pur­pos­es with­out the need for advanced or expen­sive technologies.

Stereoscopy in Medical Education

The use of stere­oscopy for med­ical edu­ca­tion began in the ear­ly 20th cen­tu­ry.  Some sources indi­cate that Dr. Daniel John Cun­ning­ham was the first to use SBS stere­o­graphs to teach human anato­my2,3.  In 1909 his work was com­piled into sev­er­al vol­umes of Stereo­scop­ic Stud­ies of Anato­my, even­tu­al­ly com­pris­ing the Edin­burgh Stereo­scop­ic Atlas of Anato­my3,4.  By the mid-cen­tu­ry mark, a resur­gence in the pop­u­lar­i­ty of stereo­scop­ic view­ing sparked col­lab­o­ra­tion between anatomist Dr. David L. Bas­sett and William B. Gru­ber, inven­tor of the View­mas­ter sys­tem.  They cre­at­ed a col­lec­tion of stereo­scop­ic disks fea­tur­ing dis­sec­tions by Bas­sett and pho­tographs by Gru­ber: A Stereo­scop­ic Atlas of Human Anato­my4.

Stereo­scop­ic anatom­i­cal teach­ing con­tin­ues to be of use today.  The reten­tion of knowl­edge in med­ical stu­dent groups shown 3D stereo­scop­ic videos is greater than that of groups shown 2D videos2,6.  This result is sig­nif­i­cant in anatom­i­cal rela­tion­ships, while func­tion­al knowl­edge appears unaf­fect­ed2.  The strength of this learn­ing impact is still unknown.  Some stud­ies deter­mined no sig­nif­i­cant dif­fer­ence in writ­ten test scores between 3D and 2D video learn­ing7.  These incon­clu­sive results are poten­tial­ly due to the type (ie. func­tion­al vers­es spa­tial) of ques­tions test­ed.  The ben­e­fit of 3D learn­ing varies from per­son to per­son.  A large pre­dic­tor of a student’s suc­cess in anatom­ic learn­ing is visu­ospa­tial abil­i­ty; stereo­scop­ic learn­ing aids may be more ben­e­fi­cial for those with low­er nat­ur­al visu­ospa­tial scores6,7,8.  It effec­tive­ly evens the play­ing field.  Unfor­tu­nate­ly, though many med­ical schools cur­rent­ly give stu­dents access to 3D com­put­er mod­els, they are dis­played or pro­ject­ed onto flat screens, and thus lose the actu­al stereo­scop­ic ben­e­fit6,8.  Mod­ern teach­ing pro­grams with true stereo­scop­ic pro­jec­tion of CT vas­cu­lar mod­els have been intro­duced through polar­ized pro­jec­tion7,9.  When intro­duced to stereo­scop­ic tech­niques of learn­ing, stu­dents find it use­ful and are inter­est­ed in using it in the future6,10.

Figure 1: Stereoscopic teaching tools throughout the decades (1905–1960).
Stereo­scop­ic Stud­ies of Anato­my, vol. 2 (1909); sec­tion II, No. 13: Spinal Canal No. 4, p. 28.  This is a SBS view of dis­sect­ed cra­nial nerves and arter­ies, intend­ed to be placed into a stereo­scop­ic view­er.  There are hun­dreds of such views with­in the Edin­burgh Stereo­scop­ic Atlas of Anato­my4.
A Stereo­scop­ic Atlas of Human Anato­my, sec­tion I, the Cen­tral Ner­vous Sys­tem (1952); p. 152–153.  The back pages of Bassett’s atlas con­tain­ing a jack­et of View­mas­ter reels and instruc­tions for viewing/projection5.

In the 21st cen­tu­ry, stereo­scop­ic teach­ing has been thor­ough­ly mod­ern­ized and adapt­ed, sig­nif­i­cant­ly in the field of neu­ro­surgery, where many prac­tice-hours are need­ed despite lim­it­ed avail­abil­i­ty of patients and OR time10.  Vir­tu­al real­i­ty (VR) sim­u­la­tions in 3D space allow res­i­dents to gain expe­ri­ence in the field with­out risk to patients10.  These can be both hap­tic (touch sim­u­la­tion) and non-hap­tic, and stud­ies have shown them to be sig­nif­i­cant­ly ben­e­fi­cial com­pared to con­trol groups with­out VR, though some uncer­tain­ty exists11,12,13.  The hepat­ic por­tion of the sim­u­la­tion train­ing may not con­tribute sig­nif­i­cant­ly to the ben­e­fit, sug­gest­ing that the improved learn­ing out­comes is due to the stereo­scop­ic VR13.  Stereo­scop­ic mod­els are also used for learn­ing pur­pos­es in oth­er spe­cial­i­ties10.

Stereoscopy in Surgery 

Stereo­scop­ic tech­niques in surgery are not sim­ply lim­it­ed to train­ing and sim­u­la­tion.  As ear­ly as 1922, sur­geons had adapt­ed the knowl­edge of stere­op­sis for use in the OR15.  Gun­nar Holm­gren retained depth when mag­ni­fi­ca­tion was required by first using binoc­u­lar micro­scopes at the Uni­ver­si­ty Clin­ic of Stock­holm15.  This tech­nique was quick­ly employed world­wide and had espe­cial ben­e­fit in the small surg­eries of the head and neck15.

Stere­oscopy is also a use­ful phe­nom­e­non in laparo­scop­ic surg­eries.  Tra­di­tion­al­ly, the laparo­scope video is dis­played on a 2D mon­i­tor and there­fore lacks poten­tial­ly cru­cial depth infor­ma­tion.  Stereo­scop­ic laparo­scopes allow true 3D rela­tion­ships to be deter­mined with­out open­ing the body cav­i­ty to human eyes16.  This is done sim­ply by includ­ing two visu­al view­points and then view­ing them via any stereo­scop­ic method.  As min­i­mal­ly inva­sive surg­eries, and there­fore laparoscopy, increased in com­plex­i­ty, the dif­fi­cul­ties of per­form­ing pro­ce­dures with­out depth became appar­ent17.  In the ear­ly 1990s stereo­scop­ic laparoscopy was used for the first time on human patients: a laparo­scop­ic chole­cys­tec­to­my per­formed at Nuclear Research Cen­ter Karl­sruhe17.  The incor­po­ra­tion of stere­oscopy in laparo­scop­ic pro­ce­dures increas­es the ease of tasks that require 3D visu­al­iza­tion such as organ mobi­liza­tion and sutur­ing17.  A 2017 lit­er­a­ture review by Schwab et al. col­lect­ed objec­tive and sub­jec­tive infor­ma­tion from patients and sur­geons using 2D vs 3D laparo­scop­ic sys­tems dur­ing chole­cys­tec­to­my oper­a­tions18.  They found that there were no increased neg­a­tive out­comes in either method, and that many sur­geons per­ceived bet­ter depth per­cep­tion and con­trol with the 3D sys­tems18.  Stereo­scop­ic laparoscopy can also be com­bined with laparo­scop­ic ultra­sound for aug­ment­ed real­i­ty views of inter­nal struc­tures16

Image-guid­ed surgery (IGS) is wide­ly used in a vari­ety of fields14.  IGS allows a 3D sur­gi­cal plan to be devel­oped on a 3D mod­el of the patient which is cre­at­ed from pre­op­er­a­tive imag­ing14.  3D mod­els are also used for pre-plan­ning, head frame place­ment and to deter­mine acces­si­bil­i­ty before radio­surgery19.  This short­ens pro­ce­dure times, opti­mizes patient expe­ri­ence and decreas­es repeat pro­ce­dures19.  Unfor­tu­nate­ly, most of these mod­els are viewed on a 2D mon­i­tor, elim­i­nat­ing the ben­e­fit of true stereo­scop­ic effect14.  It would be ben­e­fi­cial and fea­si­ble to include stereo­scop­ic view­ing through a polar­ized dis­play14.

3D imag­ing can be per­formed intra­op­er­a­tive­ly with­in the OR through stereo­scop­ic record­ing and polar­iza­tion14.  These images may be com­bined with the pre­op­er­a­tive mod­els for intra­op­er­a­tive visu­al­iza­tion14.  The ease of incor­po­rat­ing stere­oscopy into surgery increas­es as tech­nol­o­gy devel­ops.  Some­thing as com­mon­ly avail­able as a smart­phone can be adapt­ed into a view­ing device20.  Suc­cess­ful robot-assist­ed oph­thalmic surgery sim­u­la­tions have been per­formed by attach­ing a stereo­scop­ic cam­era to a binoc­u­lar sur­gi­cal micro­scope and dis­play­ing the resul­tant image on a smart­phone VR head­set20.

High-def­i­n­i­tion stereo­scop­ic 3D imag­ing in real-time is cru­cial in the emerg­ing field of telesurgery.  With ultra-fast 5G inter­net con­nec­tion it is pos­si­ble to per­form robot-assist­ed laparo­scop­ic surg­eries thou­sands of kilo­me­tres from the patient site21,22.  These meth­ods, though still new, could poten­tial­ly com­bat sur­geon short­ages, remote access prob­lems, and dis­ease spread21.

Figure 2: An example of telesurgery technologies.
5G ultra-remote robot-assist­ed laparo­scop­ic surgery in Chi­na (2020): Fig­ure 1 “Micro­Hand” sur­gi­cal robot sys­tem22.
Left: The sur­geon con­sole con­tains a stereo­scop­ic image view­er and mobile mas­ter manip­u­la­tors to con­trol the patient side cart.
Right: The patient side cart per­forms the robot-assist­ed surgery via com­mands from the sur­geon console.

Stereoscopy in Ophthalmology

Stere­oscopy is an impor­tant part of vision.  Screen­ing and test­ing for stereo­scop­ic acu­ity can help diag­nose a vari­ety of ocu­lar con­di­tions includ­ing stra­bis­mus and ambly­opia23.  There are sev­er­al stereo­scop­ic tests rang­ing in speci­fici­ty and ease of use for the appro­pri­ate patient case and physi­cian concern. 

In 1960 Bela Julesz used ran­dom-dot stere­o­cards to test for stereo­scop­ic acu­ity23.  These ran­dom pat­terns of dots appear flat and unin­ter­est­ing when viewed monoc­u­lar­ly, but when the test sub­ject uses intact binoc­u­lar vision through a stereo­scop­ic view­ing device, shapes emerge in the depth23.  The TNO stereotest uti­lizes the same con­cept and tests most­ly for ambly­opia23.  It is viewed in red/blue anaglyph and con­sists of recog­nis­able images instead of depth clues23.  TNO tests are designed so that when view­ing monoc­u­lar­ly, an incor­rect image is still vis­i­ble23.  A quan­ti­ta­tive aspect is also added23.  The Lang test is sim­i­lar again, but uses a pano­graph­ic view­ing tech­nique where no spe­cial glass­es are required23.  The most com­mon stereotest is the Tit­mus test, in which raised shapes and objects are detect­ed when viewed through polar­ized glass­es23.

Lang’s two pen­cil test, first described in 1983, removes the need for any spe­cial­ized stere­ode­vice24.  It requires that the patient cor­rect­ly line up a pen­cil with one held by the exam­in­er; binoc­u­lar per­for­mance is com­pared against monoc­u­lar in each eye23,24,25.  This is a qual­i­ta­tive test and is not used for diag­no­sis, but has been shown to dis­tin­guish gross stra­bis­mus at a high sen­si­tiv­i­ty and speci­fici­ty com­pared to ran­dom-dot and TNO with a neg­a­tive pre­dic­tive val­ue of 100%25.

Figure 3: Stereoscopic acuity tests.
Stereo­scop­ic Vision & Test­ing Tech­niques – Overview (2020): Fig­ure 3. Julesz ran­dom-dot stere­ogram. When the SBS images at the top are viewed binoc­u­lar­ly a rec­tan­gle appears clos­er in depth as rep­re­sent­ed by the draw­ing in the low­er images23.
Stereo­scop­ic Vision & Test­ing Tech­niques – Overview (2020): Fig­ure 1.  Lang’s two pen­cil test23.
Stereo­scop­ic Vision & Test­ing Tech­niques – Overview (2020): Fig­ure 1.  Lang’s two pen­cil test23.

Stere­oscopy is not only used to test for ocu­lar con­di­tions; it’s also used to treat them.  Non-sur­gi­cal treat­ments of eye move­ment and ocu­lar mus­cle dis­or­ders such as stra­bis­mus are known as orthop­tics: these include stereo­scop­ic exer­cis­es.  Dr. Louis Javal intro­duced orthop­tic treat­ment for stra­bis­mus in the late 19th cen­tu­ry, using ear­ly Wheat­stone stere­o­scopes to induce prop­er binoc­u­lar focus26.  The binoc­u­lar train­ing pro­vid­ed by these treat­ments is used in replace­ment of and to sup­port surgery26.  The over-reliance and mis­use of ear­ly orthop­tics dam­aged their ther­a­peu­tic rep­u­ta­tion around the turn of the cen­tu­ry, but treat­ments were mod­ern­ized in 1919 by doc­tors E. E. and M. C. Mad­dox and even­tu­al­ly re-pop­u­lar­ized their use26.  M. C. Mad­dox cre­at­ed stere­o­cards for the amblyoscope (lat­er the syn­op­tophore), a reflect­ing stere­o­scope-like device that allows for indi­vid­ual eye stim­u­la­tion with lights, diver­gence angle mea­sure­ment, and deter­mi­na­tion of the area of sup­pres­sion27.

In 1927 Dr. Carl Sat­tler pub­lished the first set of orthop­tic stere­o­cards for stra­bis­mus diag­no­sis and treat­ment that were avail­able for use at home28.  They were inex­pen­sive and avail­able for par­ents to pur­chase for their chil­dren28.  Oth­er sim­i­lar sets were soon avail­able and wide­ly used until the 1950s28.

Figure 4: Orthoptic stereocards for strabismus diagnosis and treatment.
Stere­oskopis­che Bilder für schie­lende Kinder (1942), as rep­re­sent­ed in What do you see? (2011)28. A selec­tion of stereo­scop­ic SBS pairs designed for use with a home view­er.  Chil­dren would be giv­en the images and asked, “What do you see?”, their answers diag­nos­ing pos­si­ble ocu­lar sup­pres­sion28. For exam­ple, in cards 1 and 1a, a child with nor­mal binoc­u­lar vision will see a rab­bit in a nest of eggs.  A child with stra­bis­mus who has reduced input from their right eye may only see the rab­bit, and will train their eyes to make the nest appear.

The ben­e­fit of orthop­tic exer­cis­es con­tin­ues to be of con­tro­ver­sy today.  Oph­thal­mol­o­gists dis­pute whether lengthy exer­cis­es sup­port marked ther­a­peu­tic improve­ment26.  Stud­ies have shown that stereo­scop­ic orthop­tic train­ing for only two weeks (15 mins twice a day) mild­ly increas­es the angle of fusion in stra­bis­mus patients and decreas­es the required pris­mat­ic cor­rec­tion29.  Longer train­ing can lead to greater improve­ment and the remis­sion of tropia29.  These ben­e­fits depend on the individual’s moti­va­tion, time com­mit­ment, and the nature of their pre­sent­ing stra­bis­mus29,30.  Exode­vi­a­tion seems to ben­e­fit more than esode­vi­a­tion, while ver­ti­cal devi­a­tion shows no effect29.  The out­come of orthop­tic train­ing depends large­ly on the sever­i­ty of stra­bis­mus pri­or to start­ing ther­a­py: bet­ter results cor­re­late with milder cas­es30.  Non-sur­gi­cal treat­ments are there­fore reserved for mild or small angle stra­bis­mus26,29,30.  They can­not over­come large dis­par­i­ties that would ben­e­fit from surgery26.  These inher­ent lim­i­ta­tions of orthop­tics are often mis­un­der­stood, lead­ing to mis­ap­pli­ca­tion of orthop­tic ther­a­pies, poor out­comes and decreased clin­i­cal sup­port26.

Stere­oscopy can also be used in screen­ing for glau­co­ma31.  Ocu­lar fun­dus images are often ana­lyzed for diag­nos­tic char­ac­ter­is­tics of the optic nerve head; this is espe­cial­ly true for nor­moten­sive glau­co­ma that can­not be detect­ed with a tonome­ter31.  Impor­tant fea­tures such as the cup depth, disc shape and cup to disc ratio are used in screen­ing31,32.  Cor­rect diag­no­sis of glau­co­ma based on these fea­tures is aid­ed by stereo­scop­ic analy­sis31,32,33,34.  Oph­thal­mol­o­gists can view these stereo­scop­ic images either dig­i­tal­ly or on film33.  When com­par­ing glau­co­ma detec­tion using stereo­scop­ic ver­sus mono­scop­ic images, the stereo­scop­ic screen­ing detects cas­es at increased sen­si­tiv­i­ty and repro­d­u­ca­bil­i­ty32.  Stereo­scop­ic images more accu­rate­ly indi­cate glau­co­ma patients that are near­er the cup to disc ratio thresh­old32.  Fur­ther­more, com­put­er-aid­ed machine-learn­ing detec­tion meth­ods that focus on ana­lyz­ing stereo­scop­ic images of the ocu­lar fun­dus out­per­form those that rely only on a sin­gle image with no depth infor­ma­tion31,34.


This is by no means a com­pre­hen­sive col­lec­tion of the uses of stere­oscopy in med­i­cine.  The increased infor­ma­tion of 3D con­tributes ben­e­fits to many areas of imag­ing not men­tioned above, such as screen­ing mam­mog­ra­phy, echocar­dio­g­ra­phy, bron­choscopy and scintig­ra­phy35,36,37,38.  Humans exist in and process the phys­i­cal world in three dimen­sions; it is no sur­prise that the best med­ical obser­va­tions also include depth information. 

Stere­oscopy remains a long-stud­ied and under-used tech­nol­o­gy in med­i­cine.  It is used wide­ly in some spe­cial­i­ties, includ­ing anato­my, neu­ro­surgery, laparo­scop­ic surgery, imag­ing and oph­thal­mol­o­gy, but remains a rel­a­tive­ly unknown con­cept in the gen­er­al med­ical and non-med­ical pop­u­la­tion.  Com­mon crit­i­cisms of stere­oscopy in all fields include the need for addi­tion­al view­ing devices, glass­es or tools10,23,32.  While this is poten­tial­ly true, nov­el and inex­pen­sive stereo­scop­ic devices are avail­able in the major­i­ty of cas­es20,28.

The pop­u­lar­i­ty of stere­oscopy has ebbed and flowed over the many decades since Charles Wheat­stone first described its prin­ci­ple1.  The extent of its use in med­i­cine has fol­lowed a sim­i­lar process.  The cur­rent progress in com­put­er tech­nol­o­gy allows for increased con­sump­tion of mod­ern 3D movies, and increased inno­va­tion in the med­ical field.  We exist in a cur­rent stereo­scop­ic boom.  There are more oppor­tu­ni­ties for stere­oscopy in vir­tu­al care and remote pro­ce­dures21,22.  More 3D tools are avail­able to med­ical stu­dents6,8.  For record­ed depth infor­ma­tion to be of ben­e­fit, 3D data need to be viewed not from flat screens, but from stereo­scop­ic view­ers.  Only in this way is the patient tru­ly represented.


Thank you to Andrew Lau­ren for edit­ing, proof­read­ing and con­tribut­ing from his won­der­ful col­lec­tion!  Thanks also to David Kuntz and Bri­an May for direct­ing my areas of focus.


2D          Two dimen­sion­al
3D          Three dimen­sion­al
SBS        Side-by-side (stereo­scop­ic view­ing)
OR         Oper­at­ing room
VR          Vir­tu­al real­i­ty
CTA        Com­put­ed tomo­graph­ic angiogram
IGS         Image-guid­ed surgery

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Lindsay Cole (Victoria, Canada)

My stereo-hob­by is quick­ly approach­ing its 3rd birth­day, prov­ing once again how time flies!  I start­ed tak­ing stereo pho­tos when I was liv­ing in Ham­burg, Ger­many, and need­ed a per­son­al inter­est to pass the time.  Like many peo­ple I first encoun­tered the stereo process thanks to Dr. Bri­an May, and since then I’ve met many won­der­ful pho­tog­ra­phers and artists! I main­ly enjoy hyper­stere­os and pho­tos that can demon­strate the grandios­i­ty of my sub­jects.  Hav­ing returned to Cana­da, my main focus has been the nat­ur­al beau­ty and colour that sur­rounds me every day.  Any time I’m on a hike or camp­ing excur­sion I’m sure to snap a few pic­tures! It’s amaz­ing how much you can do with a smart­phone.  My only equip­ment cur­rent­ly is my trusty, old, cracked Sam­sung Note 8… the cam­era is great and that’s all that mat­ters!  Sequen­tial pho­tos do have a lim­it, but there’s enough for me to work with for now!

Insta­gram-pro­file: staring.at.stereos