{"paper_id":"1c4a8aa1-4797-4ea0-9e43-e25fcc91faf9","body_text":"1 \n \nTitle: Ev aluatio n of a  V i rtual  Re ality - Bas ed Ey e Track er for  N euro - O ph t h a l mic Asse ssment : A 1 \nFe a s i bility, R e liabil i ty and Repr oducibi lity  Study   2 \n 3 \nAuthor s: I rem  Karae r 1 ,  H a - J un  Y oo n 1 , R unfeng  M a 2,1 , Reene t t e Sav an t 1 , Van e ss a Rodwell 1 ,  Riddhi  4 \nShe noy 1 , Zha nhan T u 1 , Qa de er Arsh ad 3 , Elizabet a B Muk ae tova - L adin ska 3,4 , Mervyn G  T homas 1* 5 \n 6 \nAffiliations :  7 \n1 U l v e r s c r oft  Ey e  U n it ,  De p ar t m e nt  of  P s yc h o log y  a n d V is i on S c i en c es , U n i v er s it y  o f  Lei c es te r , 8 \nLe ices ter , LE 2 7LX , U K 9 \n2 Chongq ing Medic al U niv e r s ity,  Ch ongqi ng , Chong qing, Ch i na.  10 \n3 Sc hool of  P sych ology a n d Vi s i on Sc i e nce s ,  Unive rsi ty o f L eice s te r, Lei ce s te r,  Englan d, U ni te d 11 \nKing dom. 12 \n4 The E ving t on Cent r e , Le ice s ter G e n eral Hospi tal, L eice ste r, Unit ed King dom.  13 \n 14 \n 15 \n*Co rre spo nding a uth or ,  Tel: + 44 (0)116 2 52 587 9, Fa x: +44  (0)116 22 3 1996,  email : mt350@le .ac .uk  16 \n 17 \nRunnin g titl e: Ka r a e r  et al. Virt ual Real ity  Eye T r a cke r  for N euro - O ph t h a lmic Ass e ssmen t  18 \n 19 \nAbs t rac t = 237 word s 20 \nManu script : 28 96 words  21 \nNumber o f figu re s = 4  22 \nNumber o f tab le s = 1  23 \nSup plemen tary t a bl e = 0  24 \nS u pp l e m e nt a r y  f ig u res  =  0 25 \n 26 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \nNOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice.\n\n2 \n \n 27 \nAbs tract  28 \nBac kground/Objec t ives :  V i r tua l R eali t y  ( VR) eye t rac k er s of fe r por t a ble , obje ctive  t o ol s  f o r ne uro-29 \nophthal mic t e sting. T hi s  s tudy eval ua ted the f ea sibi li ty, repr oduc ibility and r elia bil ity of a V R ey e 30 \ntrack er (Bulbi CAM ) comp are d to we a r a bl e ey e- tr a cki ng gla sse s ( PupilL ab s Ne on gl a sse s), highlig hting 31 \nits p oten tial c linic al u til ity and f e a s i bili ty.     32 \nSubjects / Met hods: A prospec tiv e s t ud y inv olving  39 he althy pa r tic ipan t s (mea n a geGiq2±Giq2 SD = 30 . 0 ± 33 \n9.5 year s) a s ses se d int er -visi t r e p r o ducibil ity of Bulbi CAM t e s t s ac ro s s  tw o visi ts.  Pupilla r y  ligh t  r efl e x 34 \nte sts we re  conduc t ed wi t h bot h BulbiC A M an d PupilL ab s Ne on, ena bling p air ed a s s e ssmen t s .  35 \nReproduc ibili ty  was an a lys ed u sing i nt ra - c las s  c orre la tion c oe ffici e nts (I CC ), rel i abi lity  via Bland-36 \nAltman a naly si s, an d part i cip a nt  expe rie nc e through a sur v ey e valu a t i ng t es t  c om for t  and u sabil i t y .  37 \nResults :  Pa r tic ipa nt s’ feed b ac k (n= 27 ) hi ghl ighted hi gh ac cept ability f or Bulbi CA M : 89% foun d th e 38 \nte st  com for table , 9 2.6% fe l t  t h e  te sting  duration w a s  app ropri at e, an d 81.5%  rep o rt e d no ey e strai n 39 \nor fa tigue . Int er -visi t r e p r od ucibil ity o f B ulbi cam t e st s  s how ed hig h r eproducib il it y for pur suit and 40 \npupil  te s t s (I CC = 0.8 8-0 .76) , w hile s ac cad ic  task s s how ed lo we r rep roduci bility ( be st IC C a t  0.62 ). 41 \nPai red  a sse s s me n t s be t w e en de vice s  sho we d clo s e a g reem ent for ke y pupi llome t er metr ics : b a seli n e 42 \ndia mete r  (bi as : -0 .48 ± 0.47 mm), p eak cons tr ic ti on dia me ter (bia s: -0.56 ±  0 .36 mm), cons tr i cti on 43 \nve locity  (bia s: 0.22 ±  0.58 mm/s), and d u r a t i on o f con s t riction (bi a s : - 0 .052 ± 0 .15 s) .  44 \nConc lus ions: Thi s  stu dy hi ghligh t s the c li nic al fea s ibi li ty of Bul biC AM, with hi gh p atie n t  acc ept abili t y  45 \nand r e produ cibil it y  f or pur s ui t a nd pupil  t e s t s . Pai red a sse s s men t s con f i r me d it s  a cc ur a cy f o r  k ey 46 \npupil lomet ric pa r a me te rs, v alida t i ng it s re liabil ity f or cli nica l and r e sea rc h use .  47 \n 48 \n 49 \n 50 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n3 \n \n  51 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n4 \n \nIntroduction  52 \nEy e-t r ac king  devi ces a re w idely  utiliz ed i n bo t h neu ro- ophth almic  re s e a r c h an d cl in ical  s e tting s , 53 \nprovidi ng va luable  in sight s  int o ocul ar an d ne ur ol ogic al func t i o n (1 -3). In rec ent y ea rs, Virtu al Re ali ty 54 \n(VR )  hea d set e ye - tr a cki ng dev ice s ha ve ga ined i ncrea sing pop ulari ty a s  po rta ble  and e ffic ien t 55 \nalter nativ e s to conv enti onal e ye -t rack ing sys tem s  (4 ).  By int eg r a t i ng adv ance d ey e -trac king 56 \nca pabili t i es  wit hin VR h e ad se ts, th e se de v ice s  of fe r en ha nce d fl exi bility a nd con venien ce (5) . Unli ke 57 \nco nventiona l s e t u p s  w ith s e p ara te di spla y s , p r oje c tor s , a n d co mpute r s , the s e al l -i n-on e sy ste ms  58 \nof fer a spac e- s a ving s olu tion  f or  clini cs w hile  providin g ac curat e ey e -t r a cki ng data .  59 \nBoth subjec t i ve a n d objec t i ve me t hod s  a re employe d to eva lua te ey e mov eme nt s and pupi llary l ight 60 \nrefl ex e s . H ow ever , the re i s  a  growin g ne ed for  c linic all y ad a pt a ble ey e t rack ers u t ilizing  objec t i ve 61 \nmethod s (6 ). Pa rtic ularly, VR hea ds et ey e - t rac king  devi ce s equipp e d with a u tom ated so ft w a re, o f fer 62 \nsignific ant adv an tage s by  providin g preci se a n d s t a nd ardize d mea sur ement s, en s ur i ng ac curac y an d 63 \nrelia bili ty (7, 8) .  Bulbi CAM i s an examp le of a V R head s et with eye trac king capa bil itie s aime d a t 64 \nobtaini ng obje c tive metr i c s for  oculomo tor be haviour a nd pupill ome te r; thu s  h avi ng  the pot enti al 65 \nfor a s s e s sing a  ra nge o f n euro - o p ht h almi c  disea s e s  a nd dys func t i on s  (9 ). 66 \nVR ey e t rack ing sy ste ms  a r e  und er -expl o r e d compa re d to t r a di tional sy stem s (10 )  and to d at e, th er e 67 \nare no  re pr od ucibil i ty/rel iabili ty  studie s  using V R head s et -ba sed eye  tra cke rs. Th e r e for e, in thi s 68 \nst u d y, we  aim to a sse s s  th e r e p r odu cibil i t y  of Bulbi C A M te st s  an d relia bil ity of Bul biCAM com pa red 69 \nto oth er wea ra ble ey e track e r with pupi ll ometry such a s  PupilL ab s Neo n gla s se s , o ffe r i ng new  70 \ninsight s in to th eir po ten tia l cli nica l appli c abil ity.  71 \n 72 \n 73 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n5 \n \nMaterial s (Subjec t s) and Methods  74 \nParti cipan t s  75 \nHealthy  par ticipa n ts (n =39 ) wer e rec r u i te d for t h e s t udy  and succ e s sfull y co mple ted bo th v is i ts . 76 \nHealthy  s ubj ect s wer e de f i ned a s pa rtic ip ant s  who ha d no neu rolo gica l di se as e s  or clini cal s ig ns  o f 77 \noc ular motili ty dysfu nction .  The dem ogr aphic  charac t eri s tic s  o f t h e  part icipa nts a re pr e sent ed in 78 \nTable 1. T heir ag e s  r ang ed from 21 t o 59 yea rs, a nd th e mal e -to- fema l e ra tio w a s 18:22. Re fr a c tive 79 \nerro r s rang ed from -8 .00D to +5 . 50D .  All  subjec t s  a chi ev ed a be s t -c o r rec t e d visu a l a cuity  (BC VA) o f  80 \n0.20  logMAR or bet ter . Colo ur v is i o n, a s ses s ed wi t h t h e  I s h ihar a p seudoi s ochrom a t i c pla te s, w as 81 \nnormal ( 1 7 / 17 ) in mo st pa rticipa nts. Ho we ver, one indivi dual r ec or d ed score s o f 5/ 1 7 in the r ig h t 82 \ney e and 6 / 17  in th e le f t e ye .  83 \nNone o f th e p artic ipant s ha d a hi stor y  o f neurolog ical  di so r de rs . Oph thalmolog ica l  histo r ie s  w er e 84 \nlarge ly unrema r k able,  exc ept in fiv e indi v idual s: thr ee ha d cornea l re frac tive  s u rge r y , one h ad 85 \nprevi ou s ly  undergon e  strabismu s s urge r y  and a lso had c olour b lind ne ss, and on e had lat tice 86 \nd e ge n e ra t i on  a nd  p os t e r i or  vi t r eou s  det ac h m e n t  in  bot h  e y e s . 87 \nWritten  in forme d co nsent w a s obtaine d f rom each  p art i cip a nt.  88 \n 89 \n 90 \n 91 \n 92 \n 93 \n 94 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n6 \n \nTabl e 1:   Demog r a phic info rmati on of p a rtic ipan ts 95 \nVa r ia ble      \nAge, M ea n ± SD  30. 2±9.7  \nS ex, No. (%)            \n      Fem ale  2 1(54)  \n    Male  1 8(46)  \nE t hnic ity, No. (%)  \n  \n     White-Br i t ish  2 (5)  \n     W hi t e-Other  8 (18)  \n     As ia n-O riental  21 (54)  \n     A sian-India n \nS ubcontin ent  7 (18)  \n     A fro-Ca ribbean  1  (2.5)  \n     Other  1(2.5)  \nVis ua l Acuity (c or rec t e d, \nlogMAR), Mean ± SD    \n  \n     L eft  e y e  -0.01±0 .06  \n     Right e ye  -0.02±  0.07  \nCol our  Vision    N or mal  N o. (% )  38  (97.4)  \n  96 \nStudy D e s ig n  97 \n39 p art i cipan t s co mplet ed two te sting se s s i on s , s c hed uled a t s im ila r time s o f th e da y. At ba s eline , all 98 \npartic ipan t s  unde rwent be st -corr ecte d v isual ac ui ty a ss e ssment s (ETDRS c har t at 4m) a nd I shihar a 99 \nte sts for col ou r  vision scr eeni ng.  100 \nFi gure 1 il lustra te s t he par tici pan t s ’ fl ow through th e  s tudy  and t he o r d er o f te s tin g pe r fo rmed.  101 \nFurthe r de tai l s  reg a rding the s timulus p a rame te rs u sed in Bulbi CA M are p rovi ded belo w.  102 \nIn the s eg men t o f the s tudy inv olvin g Neon gl asse s , part ici pant s  w or e the gl a sse s whil e tr a ck ing 103 \nst i muli di spl ay ed on t h e  Bulbi CAM scre e n. D uring  the s e  me as urem ent s ,  pa rticipa nt s ’ he ad s  wer e 104 \nposi tione d slig h t l y behi nd th e s t a nd ard p os tur e  t o  acc ommoda te t h e  glas s e s  a nd ens ure ac cur at e 105 \ndata cap ture .  106 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n7 \n 107 \nFigure 1 :   Flow cha r t ex plai n in g th e s tudy de s i g n . B: B ulb icam, N : P upilL a bs  N eo n  e ye t rac king  gla sses  108 \n 109 \nPart i cipan t Ex perien c e  110 \nP ar ticipa nts w e r e  a sked t o c omplet e a  q ues tionn aire a fter c omple ting  t w o vi s i t s. The q ue s tion na ir e 111 \ns c or ed (1 ) C om for t, (2 ) Le ngth o f th e ex amina t i on, (3) Brigh tne s s , (4) D o uble vi s io n,  (5) Gr ad ing th e 112 \nfatigu e/ ey e strain s p ec ific ally for Bul bica m on a 5 - point Lik er t  s c ale a s : 1  = S trongl y  Dis a gr ee, 2 = 113 \nD i s ag r e e, 3 =  Neu t r al,  4 = Ag ree , 5 = S tr o ng ly Agree  (Figur e 3 ).  114 \n 115 \nBulbiCAM  116 \nBulbiC A M  (BulbiT ech AS , Oslo , Norwa y ) is a C E - c er t i f i ed and F DA- r eg ister ed e ye - t r a cki ng dev ice t ha t 117 \nus e s  A I - int eg r a te d s of twa re t o  a sse s s  the  data ob tain ed by camer a s. I t ac comm od ate s  an 118 \ninterpu pilla r y  di st a nce o f  49mm to 75m m . The di s pl a y mode  hardwar e u t i li se d  is th e Sha r p 119 \nLS0 55R1SX0 4, whi ch c ons i sts of 5.5”  LCD  pane l (2560× 1440 pi xel s @60 fp s; 1920× 1080 pi xels @60 120 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n8 \nfp s ), M IPI  boa rd, Whi te 60 - pi n fl ex cable ,  HD MI - MI P I b oard (ba sed on T C358870XBG M silic on) . The 121 \ncame r a  i s config ure d to ca p t ur e tw o dif f eren t type s o f ima ge s alt erna tely , D a r k  Pupil  (DP ) an d Bright 122 \nP upil ( B P).  I f the ini tia l frame i s B P , th e n ext one  will  be D P , f ollo wed by  BP  ag ai n, a nd s o  o n. The  123 \ncame r a  ope rat e s at 400 frame s  pe r  s ec o nd (FP S ), cap turing  200 DP  a nd 200 BP i mage s  pe r  s ec ond, 124 \nr e s ulting  in a  to t a l o f 400 pupil ima ge s p er s econd . The s timulu s s y nchr oniza tion typi call y has an  125 \nacc uracy  of ±18 ms, with a w or s t - ca se d e viation of ±38 ms (9 ).  126 \nExpe r im ental se t-up is s how n on F igur e 2 A, a nd Fi gure 2B show s r eal time  re cordi ng s c r e en.  127 \n128 \nFigure 2 :   (A ) Bul biCAM ey e track ing de v i ce  s e t up an d a par ticip a nt bei ng a sse s s e d  ( p l e as e  c o nt ac t  129 \nt h e c or re s pon ding au tho r to req ue s t a c cess  to F i gure2A)  ( B ) B ulbic am screen d ur i ng a s s e ss men t (C )  130 \norigin al pur s ui t te s t da ta . Whi te l ine s s h o w the s tart i ng and e ndi ng o f  th e stim ulu s.  Verti cal a r row  is  131 \na  s c a l e of  w a v e  am pl it ud e  a nd h o r i z ont al a r r ow  r e p r e se n ts  t wo  s econd s ( D) ori gin al  s ac cad e s  te st 132 \ndat a (E) origin al pu pi l te st da t a  133 \n 134 \nPupilLab s  N e on g la s s e s 135 \nP upilLab s N e on Gla s ses  (Pupil Labs Gmb H, Berlin, Ge rmany ) ar e ey e - t r ac king  glas se s  e quipped with 136 \ns c en e c amera s in fron t of the g la s s e s and  t w o eye  cam er a s  w ith 850 nm infr are d ill uminator LE Ds . 137 \nThe de vic e is conn e cted to th e c ompani o n devi ce (Andr oid phon e) whi ch en abl e s the gl a sse s to r u n 138 \nand proc e ss th e da ta  coll ecti on. P upil C lo u d websi te i s th e rec ommend ed t o o l fo r  analy s in g th e da ta 139 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n9 \n \nand pr o ce s s in g th e reco rdin gs. PupilL abs N e on gla sse s  en ab le s r e sea rche rs t o co llect g aze, sacc ad e s, 140 \npupil  diame ter s dat a a long side r ea l -worl d fron t ca mera foo tage .  The c amera op e rate s  a t a 141 \nfreq uenc y of 20 0 f rame s pe r se cond ( F PS ) (11) .  142 \nData Set  143 \nPur suit s, s ac cade s  a nd pupill ary lig ht r e f l ex tes t val ue s  wer e obta in ed by Bulbi CA M. The  s mo oth 144 \npursu it te s t ev alu ate s how  well  th e ey e t r a cks a vis ual ta rget smoo thly .  The gain v alues w ere  145 \nprovide d f or pur s ui t te s t s  i n re s pon s e to 10  degree 0.5 Hz  fr e qu ency  stimul i. Gain,  w hich measur es  146 \ntrack ing a ccurac y ,  is  d efin ed a s  th e r a t i o  of the s t im ulu s ' s  v eloc ity t o the ey e's m oveme nt veloc ity. 147 \nPer fec t  t rac king  i s  indic at ed by a gai n val ue of 100 %, but un d er-t rac king is  sugg e sted by va lue s le s s  148 \nthan 1 00%. T hr o ugh ex amina tio n o f thi s  variabl e a t dif fer ent s timulu s fre quenci e s, the  acc uracy  and 149 \nef fec t i ve ne s s  of the smoo t h  pur s ui t sy st e m ca n be e valua t e d in va r i ou s  s c enari o s ( 9,12). S t i muli and  150 \ntrack ing rec ordi ngs o f bo th right an d l ef t eye  is  s how n in  Figure 2 C.  151 \nSa cca de s are rapid eye mo veme nt s th at s h i ft  gaz e betwe e n dif f eren t ta rget s .  Duri ng a visual s earc h 152 \nta sk, the sac cad e  t est de live rs both ho rizo nt a l and ver tical  s timul i . Pe a k ve locity,  l atenc y, an d 153 \nac curac y pa r a me ters a re p r ov ide d to a ss ess sacc adic  ey e move me nt s . Ve rtic al 9 d egree a n d 154 \nhorizon tal 20 degre e sac cade  pa rame ter s were a ss e ssed u sing   BulbiC AM’ s sta nd ard te st pro toc ol. 155 \nFi gure 2D show s exa mple s o f horizon tal and vertica l s a cc ad e s.  156 \nPupil  ba selin e -pe ak c on s t ric t i on di ame te rs and con s t ric ti on vel ocity value s  w er e obtain e d fo r  157 \npupil lomet ry te st i ng . Da ta f rom onl y one  e ye w as anal y s e d to a s s e s s re pr od ucibil i ty and r e liabil i t y  of 158 \npupil lomet ry te st i ng, since  all the  p art i ci pa nts we r e  h eal thy  and w e ex pected a high  degree o f  159 \nco r rela t i on be twee n the two e ye s. The di agram in Fig ur e  2E show s th e pu pil dia m ete r  increa sing  and 160 \ndec r e a sing th rough th e t ri al s . I n ad dition  t o Bulbic am, th e s ame variabl e s  fo r pupi l te s t w er e 161 \nobtain e d fro m PupilL ab s N eon gla sse s Pu pil C loud pla t f orm w here gaz e a nd pupil diamete r da ta  is  162 \nav ailable.   163 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n10 \n \nStatist i c al Analy si s  164 \nA sampl e s i ze c alc ula tion w a s  per f o r m ed  bas ed on a n exp ec ted i ntrac la s s  c orre la ti on c oef ficie n t  165 \n(I CC ) of 0. 675 , deriv ed from sacc adic  gai n  r e liabil i ty (I CC s ra nged from 0 .52 – 0 .8 3) data in h eal thy  166 \nco nt rol s r epor ted in a  Hun tington' s di sea se stud y (13) . A s s umi ng a null hy pothe s i s  ICC o f 0.50, a  167 \nsignific anc e lev el o f 0.0 5, an d 80% pow er, the r equire d samp le siz e  wa s e stim ated  to be  27 168 \npartic ipan t s . To ac coun t fo r an  an tici pat e d 10%  dropout ra te, the fina l adju st ed sa mple s iz e w as 169 \ndete rmined  to  be 31 par t i cipa nts .  170 \nThe  IC C wa s  u s ed to a sse s s  i n t e r-vi s it r ep roduc ibility o f BulbiC AM t e sts (14 ). At th e end o f the two  171 \nvi s it s, da ta from n= 39 pa rtici pan t s  w as a nal ys e d for the pu rsui t  te st, n =37  fo r  t he  vertica l 9 de gre e 172 \nsacc adic  t e s t, n = 35 fo r the h orizon tal 20  degree sac cad ic te st , and n= 35 for th e p upil  te s t , 173 \nre spectiv ely . F or pur s ui t s, gai n val ue s  we re an aly sed in  re s pon se to 10  degre e 0.5 Hz  freq ue ncy 174 \nst i mulu s.  For sacc ad es , pea k ve locity , la t enc y and  acc uracy  val ues  o f ver tica l 9 de g r e e and ho r i z on tal 175 \n20 d egree w er e anal y sed . For th e pupil t es t; ba s eline pupil di a met er, pe ak  cons tri ction di ame ter an d 176 \nco nstriction vel oc ity w ere an al yse d. Te st reprod ucibi lity is c a tegor ized a s ex cell e nt when t he  I CC 177 \nex ceed s 0.9 0, good  when it fall s be twee n  0.75 a nd 0.90 , moder at e fo r va lue s rangi ng  fr o m 0.50 to 178 \n0.75 , and po o r  w hen i t  i s  be low 0 .50 (15 ) . 179 \nWe obt ain ed pai red pupill ome try data fr om Pupil Lab s Neo n gl ass e s in n= 23 par tic i pant s  and u sed 180 \nBlan d-Al t ma n te st to e valua t e  t h e agr ee me nt in pupi llary li ght r ef lex mea sur e m e nts  betwe en 181 \nBulbi CAM a nd Pu pil Lab s Neo n g las ses (1 6).  182 \nBlan d-Al t ma n anal ysi s  w a s pe rf or me d u si ng Graph Pad P r i s m, a nd I CC a n alysi s u sin g R.  183 \nEthic al app roval  184 \nThis study rec eived  eth ica l approva l from  the Ea s t Midl a nd s  –  N o tting h am 2 Re sea r c h Ethic s  185 \nCommitt ee ( RE C ) (RE C re fer ence : 21/EM / 00 17, pro tocol  ver sion : 0772 , and th e UK Hea lth Re s earch 186 \nAutho rity (HR A) app roval  ( IRAS I D: 279 30 9).  187 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n11 \nResults   188 \nPart i cipan t Ex perien c e  189 \nA tota l of n =27  par ticipa nts pr ovi ded f ee dba ck on their Bu lbiCAM e xamina ti on ex perienc e  us i n g a 5 -190 \npoint Li kert s c al e,  achi eving  an ex cel len t re s po n s e r at e, with ma jor i t y  r epor t i ng posi tive e xperi enc e s. 191 \nSpec ifica lly, 89.0% fo und th e te s t  comfo r t a ble , 9 2.6% c onsid ere d the ex amina t i on  leng t h 192 \nappropri at e, a nd 92.5%  wer e sa ti s fied w i t h  the b rightne s s  level s. F urthermo re, 6 2 .9% repor ted no  193 \nocc ur renc e o f do ubl e vi s ion ,  and 81 .5% i nd icated t he y ex peri enc ed no ey e s t rai n or fa tigue (F igu re 194 \n3).  195 \n 196 \n197 \nFigure 3 :  Patie nt Expe r ie n c e A c r o ss  D i ffe rent Va riable s.  Bar c harts ill ustra ting the  frequ ency  of 198 \nr es pons es  fo r  v ar ious  pat ie nt  e xp e r i e n ce  f a c t o rs :  ( A) C o mf o r t  d u r i ng  th e  pr o ce du re ,  ( B) 199 \nA p p r op r i at e ne ss  of  t he  e xa m i na t io n  l en gt h ,  ( C) B r i gh tn e s s  l ev e ls  us e d  du r i ng  t he ex am i n at i o n,  (D ) 200 \nInci denc e o f do ub le vi s i on , a nd (E) E ye str ain or f ati gue  expe r i ence d d uring o r  a fte r the  exam i nati on .  201 \n 202 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n12 \n \nInter -vi sit  Rep rod u c ibil it y  of B ulbi cam T est s 203 \nThe  pursuit t e st demo ns tra t e d high repr oduc ibili t y , with a n I CC v alu e o f  0 .81 (Fi g ure 4A) . Fo r  the 204 \nve r tic al 9 degre e sac cade s  t e st, the I C C v alue s fo r lat enc y, pe ak v eloc ity, and  acc uracy  were 0 .62, 205 \n0.50 , and 0 .49, r e spectiv e ly. S imila r l y, f or  the horiz ontal 20 d egree sac cad e s  te s t, t he IC C v alue s f or 206 \nthe se me tric s we r e  0 .52, 0 .46, a nd 0 .61, re spec tively  ( Figu r e 4A ).  207 \nIn the pupil te st , high r e produ cibil it y  wa s obse rved  f or  th e  ba selin e p upil dia me te r (I CC : 0.88),  for  208 \nthe pe ak c onstric t i o n diame ter (I CC: 0 .83 ), a s w ell a s fo r the c on stric t i on  veloc ity ( IC C: 0.76 ) (Fi gur e 209 \n4A).  210 \nThe se re sul ts in dic at e vary ing le vels o f re produc ibility acro s s  t he t e ste d pa r a m ete r s, w it h part icula r l y 211 \nstrong  con si st e ncy in the pur sui t and pu p il te st  me tr ic s .  212 \n 213 \n 214 \n 215 \n 216 \n 217 \n 218 \n 219 \n 220 \n 221 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n13 \n \n 222 \n 223 \n 224 \n 225 \n                             226 \n 227 \n 228 \n 229 \n 230 \n 231 \n 232 \n 233 \n 234 \n 235 \n 236 \n 237 \n 238 \nFig ur e  4. In tra -Cla ss Cor relati on (ICC) Analy s i s an d Blan d - Alt man Pl ots: (A ) ICC v a lues wi th 95% 239 \nco nfide nc e inte rv al s  fo r  sac cade s , p ursui t  and  p upil te st s. Col our s repre se nt di f fere nt te s t gro up s :  240 \nve r tic al 9° (de g r e e ) sa cca dic task (b lue ), h orizon tal 20 ° ( de gr e e ) sacc adic t a s k (gr e e n), p ur suit te st  241 \n(pur ple) , an d pu pi l te sts (red ). (B-E ) Bla nd -Al t m a n plo t s for the p upi l te s t m e tr ic s f o r  pupil d i ame ter 242 \n(ba seli ne  a nd p e ak c ons t ric tio n), c on stric t io n ve l ocity (mm /s) a nd d ur a t i on of c on strictio n .  Avera ge 243 \nrepres en ts  t h e bi a s betw e en tw o m ea sur emen ts , wh ile da s hed  lin es i nd icat e the  9 5% limits o f 244 \nagree m en t (LoA ).  245 \n 246 \n 247 \n(A) \n(B) (C) \n(D) (E) \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n14 \n \nPaire d As se s sment Bet ween D e vic e s  248 \nThe  Bland -Altma n plot s  i llu s t rat e th e a gr eemen t be t w e en Bul bi CAM and Pu pilLa b s  N eon gla s s e s  249 \nmea s u remen t s ac r o s s variou s pupil  te st pa r a me ters : Pa i r e d a s s e s smen t be twee n  devi ces showed 250 \ncl os e  ag reem en t  for k ey pu pillome te r metric s : ba sel ine di a met er (bi a s: -0 .48 ±  0. 47 mm LoA:-1.4 t o 251 \n0.45 ) ,  pe ak  cons tr i cti on dia me ter (bia s: - 0.56 ±  0.36 m m LoA: -1. 3 to 0.15 ), c on str ic t i on vel ocity  252 \n(bia s: 0.2 2 ± 0.5 8 mm/ s  L oA: -0.9 to 1 . 3), and du r a t io n o f cons tric tion (bi as: - 0 .052  ± 0.15 s LoA : - 0 .34 253 \nto 0.23 ).  Mo s t d ata  po int s  fe ll wi t h in th e limi t s o f a gre emen t (Lo A), demon s t ra tin g  agreeme nt  254 \nbetwe e n sy stem s  (F igure 4B , 4 C, 4 D, 4E).  These re s u lts sugge st goo d  agreem e nt  b etween t he  t w o 255 \nsys t e m s , w ith mino r, c on s i s t ent bia se s ac ross s t atic  and dynami c pupi l mea su rem ent pa ram ete rs.  256 \nDis c us sion   257 \nThis study ev alua ted  t h e fea sibili ty  of u si ng the Bul bi CAM devi ce i n a c linic al se tti ng, foc u s in g on the 258 \nreprod uci bility of pu rsuit, sac cad e,  and p upi llometry t e st s . In  addi tion, a pai red a sse s s me n t  be tween 259 \nBulbi CAM a nd th e Pup ilLa b s  Neon e ye- tr ack ing gl as s e s ex amined t h e  agre eme n t  betwee n devic e s. 260 \nOverall,  pa rticip a nt  f e ed bac k indi cate d a high  leve l of ac cep tab ili ty, w ith favou ra bl e rating s f or 261 \nco mfort, e xamina ti on leng t h ,  brightn e ss,  a nd minim al repor t s  of do uble v is i on or eye strain . S mooth 262 \npursu it and pup ill omet ry te st s  d e mon s tr ated st r ong  rep roducibili ty, w hile s ac cad e  te s t s s h owe d 263 \nmore v ariabl e r e sul ts . The se findi ng s  sup port th e po ten t i a l ev er y day clini cal appli c abili t y  of 264 \nBulbi CAM a s  a  f ea sible an d we ll- tole rat e d ey e- t rac king  so lution .  265 \n 266 \nInter -vi sit  Rep rod u c ibi lit y  of B ulbiCAM T est s 267 \nThe  pursuit t e st s ho wed g ood repr oduci bi lity at 1 0-d egre e, 0 .5 Hz  t e st freq uenc y . The  r e prod ucibil ity 268 \nof th e Bul bi CAM wa s a s se ssed u sing t h e  gain  value  of th e pur sui t te st a t  a  s t imul u s  f requ e ncy of 0.5 269 \nHz , as  pu rsuit ga in i s know n to dec rea se  at fr equ enc ie s above  0.5 Hz (17) . Alth ou gh pr e vious s t udi e s  270 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n15 \n \nhav e shown t ha t  g ain v alue s a t 0. 25 Hz  a r e  higher t han  th ose at 0 .5 Hz  in ch ildren , w ith per for m anc e 271 \ndec lining  as targe t vel ocity incre a se s, our  finding s  c on firm the hig h rep roduci bili ty of the  pu rsuit te st 272 \nat 0.5  Hz . T hi s  sugg e s t s th at 0.5 H z i s an i d eal pa ra met er f or  r e produc ibili t y  as se ss ment s  (18 ,19 ).   273 \nInte r-vi sit r epr oducibility f or pupi lla ry li ght reac tio n te s t s s how ed g ood r epro ducibility for b a s eli ne -274 \npea k co nstric tion diame ter s a nd c on s tric tio n velo city pa ra met er s .  I n con tr as t ,  th e  latenc y, pe ak 275 \nve locity , and a ccu r a cy p aram et er s  o f  t he  vertica l 9 a nd hori z on ta l 20 sac cad e  te st s s how ed onl y 276 \nmodera te t o p oor re pr od ucibil ity. Thi s di scre pa ncy  in repro duci bility b e tween the  s a cca dic a nd 277 \npupil lomet ry te sts c an be a ttrib u ted t o f und ament al d if fe r e nce s in t he phy siologi c al mecha nis m s 278 \nunderly ing the s e ta sk s. Pupil lary li ght r efl exe s  a r e pr i ma rily me diat ed by  the au to nomi c ne r v ous  279 \nsys t e m, whic h i s rela tiv ely s tabl e and le s s inf luenc ed by  highe r -o rde r c ognitive  pr oces se s .  280 \nIn c ontra st, sac cadi c ey e move men t s  a re  compl ex, i nvolv ing the i nt e gra tion o f s en sor y , c ogni tive , 281 \nand motor  sy stem s . Fac to r s such a s  a t t e ntion , le arning  e ff ect s, an d deci sion -mak ing a r e  know n to 282 \ninflue nc e s ac cadi c pe rformanc e, po ten ti al ly in t roduc ing v ariabil i t y  betwe e n visi ts (20-22) . Al though  283 \nprevi ou s  s tudie s h av e repo rte d high  r e prod ucibil ity fo r sa cc ade t e st s  und e r  contr olled conditi on s 284 \n(15), the mode rat e to po or re produc ibili t y o bs erve d in o ur study ma y re flec t indivi dual di ffe renc e s in 285 \natt entio n a nd enga gem ent a cr oss v i s it s. Notab ly, t he  pu rsuit t ask s ex hibi ted le ss varia bility, de s pi t e  286 \nalso b e ing infl u enced  by a tten tion and e ng ageme nt .  Thi s di ff ere nce  may be at tri buted t o the pu r suit 287 \nsys t e m’ s  r eli ance  o n co nt i nuo us, r e f l exiv e track ing me chani sm s, whi ch a r e l ess su s c ep tible  t o 288 \ntran s i e nt f luctua tion s in  at t e n t i on , co gnit ive engag ement , or phy s i ol ogic al sta te s  c ompared t o 289 \nsacc adic  move men t s .  A d di tionally , the s tudy de sign,  whic h requir ed tw o s e pa rat e visit s, coul d h ave  290 \nintroduc e d varia bili ty du e to le a r nin g e ff ec ts or di ff erenc e s  in partici p ant famili ari t y  with the  ta s k . 291 \nThe  us e  of a VR -ba sed te sti ng sy stem , su ch a s  th e Bulbi CAM, mig ht al s o play  a rol e. W hi l e ef fec t i ve 292 \nfor ce r tain  me a sure s, it  may n ot  be op ti mized for c ap tur i ng the fi ne - g r a in ed dy namic s  o f  s a cca dic 293 \ney e move ment s  w ith high  r e p r o ducibi li ty. Fu t ur e s tudie s c ould ex plore modi fic ati ons to th e te s t i ng 294 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n16 \n \nprotocol o r  alt erna tive s et up s to improv e  the r eliabili ty of sac cade  me a surem ent s  u s in g VR -b a s ed 295 \nsys t e m s .  296 \nPaire d As se s sment Bet ween D e vic e s  297 \nThis study de mon stra te s agr eeme n t  bet ween devic e s in pupil lome try te s t  variabl e s, indica t i ng 298 \nrelia bl e mea s ur ement s ac ro ss the ob s erv ed pa r a me te rs. Bul bi CAM con si s t e n t l y mea s ured l o wer 299 \npupil  diame ter s f or bot h ba selin e  and pe a k c ons t ric t io n stat e s, c ompar ed to Pupi l Labs N eon g la s s e s. 300 \nThe se d if f e r e nce s ca n be a ttribu ted t o v ariation s in pa r tic ipa nt s' head  po s i t io ning during  the 301 \nas s e ssme nt s .  D uring  Ne on gla sse s te s tin g,  participa n ts' he ad s were po s i tion ed  s l i ghtly ba ck,  leadi ng 302 \nto va r i able b rig ht n e ss l ev el s. In c on t ra s t, BulbiC AM a sse s s men ts en sure d more c o ns i st ent h ea d 303 \nposi tioning , re s ultin g in brig h t e r  l ight ex pos u re and c on s e qu en tly small e r  pupil dia meter s, 304 \npartic ula rly a t  t h e  peak  con st r i ction ph a se. The ba s eli ne pupil  diam ete r s were al so  meas ured low e r  305 \nwi t h BulbiC AM, lik ely due t o simila r f a cto rs. Alth oug h the va r i able i s t ermed a s  \" b as eline \"  dia met er, 306 \nrepea ted  exposu re t o bright l ight stim uli during t h e t r i al s  ( as  me ntion ed pr ev iousl y on m ethodology  307 \nsec tion) i s  li kely  to in flu enc e th e ba s el in e  dia mete rs. T hi s  ef fec t, kn own a s the p o st-illumi n ation pupi l 308 \nre spon s e ,  r e flect s the del a y in r etu rning  to ba selin e dilati on a f t e r  e xpo sure to a st imulus, whi ch c an 309 \ntake  s e ver al s ec ond s  ( 23) .  Con sequ ently,  diff erenc e s in stimulu s ill uminati on l evel s c ont r ibute d to 310 \nthe v aria tion in ba sel ine p upil dia m ete r i n this study .  311 \nDi screpa nc ie s in ba seli n e mea sur ement s betwee n BulbiC AM a nd PupilL ab s N eon gla sse s a re 312 \nprimarily  at tr i bu t e d t o varia t i on s  i n head  pos i tion ing an d light i llumina n ce, w ith a prev iou sly 313 \npubli s h ed  compa r i son s tudy simila r l y hig hlighting  the e f fec t  o f  ta r g e t illumi nance  variab ility on 314 \ndiff er ent mea s u remen t m eth od s  (24 ) .  De s pi te t he s e fa ct or s , th e obs e r v ed dif fe re nc es  in b a s eline  315 \nand peak con str ic tion pupi l di ame te rs st i l l fall within a cc ep tabl e li mit s  i n our s tud y . Sc hmitz  e t  al 316 \n(2003 )  pre viously c ompar ed th ree di f fere nt met hod s  of pu pil d iame ter me a sure ment a nd s u gge st ed 317 \nthat d ev iation s o f up to 1  mm may  be ac ce pt a bl e if c linic ally  in signifi can t (25 ) .  Con s i der in g  t h e  318 \nfindin g s  o f  t hi s  s tudy a long side p rev iou s r e sea r c h and t h e  pot ential e ffe c t s  o f  var ying  s timu lu s  319 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n17 \n \nill uminanc e, th e a gre ement betw e en Bul b i CAM  an d Pupi lLabs N eon g la s s e s for pu pil diamete r 320 \nmea s u remen t s remai ns robu st  a nd c linic ally applic able.  321 \nThe  BulbiC AM sy ste m mea sur e s  a high er veloc ity of pu pil c on s t riction compa red  to N e on gla s se s.  322 \nPupil  velo city i s  de te r mi ne d by identi fying  a  c onsisten t c on s t ric t i on o r dilatio n  ph as e and calc ulat ing  323 \nthe c hange  in pupi l di ame te r  or a r e a div i ded by  t h e pha s e dura tion (12 ) . Veloc i ty,  defin e d a s the 324 \nch ange in pupil diamet er pe r s ec ond for this  te s t, i s grea ter in Bulbi CA M bec au se the dia me te r 325 \nch ange ( a bs ol u t e  valu e of b a s eline -pe ak c ons t ric tion di f fer enc e ) is l arger , a nd th e  time to r ea ch pea k 326 \nc on s t r i c t i o n  is  f a s te r .  N e o n  g las s es  r e c o rd e d  a  l o n ge r  t im e  t o  c ons t r i c t io n ,  l i k e ly  du e  t o  l o w e r  327 \nbrightne s s leve l s  d u r in g the a s se ssme nt, w hich m ay ha ve c aused a slow er an d more gradual pupi l 328 \nco nstriction comp ared t o t h e  s h a r p e r  r e s pons e observe d with Bulb i CAM.  There fo re, w hile 329 \nBulbi CAM sh ow s  hi ghe r vel ocity mea sure ment s , con sid ering t h e  diame ter c hang e  and time  to  330 \nco nstriction var iab l e s  u se d to calc ula te v eloc ity, Bulbi CAM’ s  v el oci t y  mea sur eme nt is sti ll ac cept able 331 \nand r e liabl e  f or  pupil t e sting.  332 \nThe se re sul ts r e in for c e the r el iabili ty  of b oth dev ice s f or pupil lome try a s s e ssmen t s  w hile 333 \nac know ledgin g the infl u ence o f expe r im e ntal c ondi tion s on mea s u reme nt ou tc o mes .  334 \nL i m i ta ti o n s  335 \nAs a lim iti ng fac to r  o f t hi s study, r eli abili t y was as se ss ed solely  f or  t h e  pair ed c ompari son o f the pu p il 336 \nte st  betwee n Bulb iC AM and P upilL abs  Neon  glas s e s . No e valua t i on s  i nvolv ing oth er dev ice s  or t e st s  337 \nwe r e  conduc t ed, a s r eplic ating t h e  exa ct st i mulu s  wa s no t fe a sible  with a  t radi t i on al infra red ey e 338 \ntrack er.  339 \nAddition a lly, the  r e cen t upda t e s  to the d evic e so ft w a re, r equir e fu rthe r te s t i ng to  as s e ss th eir impa c t 340 \non repro duc ibility  and r eli abili ty.  341 \n 342 \nConc lus ion  343 \nThis study de mon stra te s th e f ea sibility , r eproducibi li ty an d relia bil ity of the Bu l bi CAM a s a tool f or 344 \nboth c linic al a nd r e s ea r c h app lica t i o n s . P a tien t f eedba ck o n t he Bulbi C A M e xamin ation wa s  hi ghly 345 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n18 \n \nposi tive. In te r -v i s i t  repro duc ibili t y  wa s hig h for pur s ui t a nd pupil  te s t s, s up p or ting  the dev ice' s  346 \nco ns i st ency . Whil e s ac cad e s  show ed poo r to moder at e r ep roduc ibili t y , thi s highli ghts  a r e as  for  347 \npoten tial  re fin emen t an d inve stiga tin g fu rt h e r . The pa i r e d a s s e s smen t be twee n d evi ces furthe r  348 \nva lidated the  acc uracy  o f key  pupill omet r i c pa r a me ter.  The se r e sult s  und e rsco r e t he  po ten tial o f 349 \nBulbi CAM a s  a  reli abl e and p atie nt -f r ie nd ly de vic e for ocul omo tor  and pup il lomet r ic ev alua t i on s  i n 350 \nboth c linic al a nd r e s ea r c h s etti ngs.  351 \nThe  finding s of thi s s t ud y provide  a foun da t i on for fut u re res earc h in to th e a pplic a t i on o f VR -ba s ed 352 \ney e- t rac king  s y s t em s ac r o s s variou s di sor der s  a nd c onte xt s . In fut ur e , we f o re see por tabl e V R b a sed 353 \nhea d s e t e ye tr ack ing de vic es  pl ayin g a si gni ficant r ole  in mee t in g the inc rea sing n ee d f or imagi ng 354 \nac r o ss dive rse se tting s, con firmin g the p oin t-of -ca r e  appr oac h.  355 \n 356 \nReference s  357 \n1.Oyam a A, Ta ked a S, It o Y, N a kajima  T, T akami  Y, Ta key a Y, e t  al. Novel  M etho d for Ra pid 358 \nAss es s m e nt o f Cogni tiv e Impa i r me nt  Usi ng Hig h-Pe rfo r ma nce E ye -Trac king  Tec hnology . 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(which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n19 \n \n5.Mor eno -Arjonill a  J, Ló pez-Rui z A, Jim é n ez - Pé rez J R, C al leja s- Aguile ra JE, Ju rado JM. Ey e -t r ac king  on 368 \nvi r tual  r e ality: a  s u r v ey. Vir tual Re ality 20 24 -02-0 5;28 (1) .  369 \n6.Hirot a M, Ka to K, Fuk us hi ma M , Ik eda Y,  H a yashi T,  Miz o ta A. Analy si s of smoo th  purs ui t e ye 370 \nmove ment s  in a c linic al c ont ext by  tr a cki ng the targ et a nd eye s . S ci Rep 2022  May  19 ;12(1):8501 – 6.  371 \n7.THE PO WER OF S IG H T: U S I N G EY E TRACKIN G TO ASSE SS L EARNI NG EXPE RIEN CE  (LX) IN  V IRT U AL  372 \nREAL ITY ENVIR ON ME NTS . 11th Int erna ti ona l Tec hnology , Educ atio n a nd D evel op ment Con f erenc e; 373 \n6-8 Ma r c h, 2017 ; INTED2017 Proc e eding s : 2 017.  374 \n8.Ba r k evic h K, Ba il ey R, Diaz G J. Usi ng De ep  Lea r ni ng to Inc r e ase  Eye-T rac king  Robust ne ss, Ac cur acy , 375 \nand Pre cisi on in  Virtua l R eal it y . Proc AC M C omput G rap h Int erac t Te ch 20 24 -05- 17;7(2 ):1 .  376 \n9.Bul bit ech us er man u al. 20 23; Avai lab le  at: ht t p s: // bu l bit ech.c om/ . 377 \n10.Ma han ama B, J aya wardana  Y, R eng ar ajan S, Jay award ena  G , Chuko skie  L, Snid er J, e t a l. Ey e 378 \nMove ment an d Pu pil M ea sur es:  A Revie w. F r onti e rs in Co mpu t e r  Sci e nce 2022;3.  379 \n11.P upil L abs. Pupil L abs Ne on. 202 4; Av ai lab le a t: ht t p s: //pupi l-l abs.com /produc ts / ne on . 380 \n12.Holmq vis t  K. Eye  tr a ckin g : a compreh ensiv e guid e  to me thod s and me asure s . Oxford : Oxfor d 381 \nUniver sity Pr e s s ; 2011.  382 \n13.Bl ekhe r T,  W e ave r MR, C a i X, Hui S , M arsh all J, Jac ks on J G, e t al. Te st-r et e st  re li abili t y  of sacc adic  383 \nmea s u re s in subjec ts a t ri sk for Hu ntingt on di sea s e . Inve st Oph t h a lmol Vi s Sc i 20 0 9 384 \nDec;5 0 (12):5707 – 5711.  385 \n14.Wei r  JP . Q uan tify ing te s t - re te st reliabi lity using th e intra cla s s correl atio n coef fi c ient and t h e  SEM. 386 \nJ Str ength C o nd Re s 2005 Feb;19(1) :23 1– 240. 387 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n20 \n \n15.Nij B ijvank  JA, P etzol d A, Bal k L J , Tan HS, U itde ha ag BM J, T heodo rou M, et a l . A s t a nda rdized 388 \nprotocol for  q u anti fica ti on o f sa cc adic  eye moveme nts: DEMoNS . PL oS One 20 18 J ul 389 \n16;13 (7) :e020069 5.  390 \n16.Ma rtin Bl and J, Al tman D. STATIS TI CA L MET H ODS F O R AS SESS ING AG REEMEN T BET W E EN TWO  391 \nMETHOD S  O F  CLI NIC AL  MEASUREMENT . The  Lanc et 198 6;327(8476 ) :3 07–310 .  392 \n17.Ma rtin s AJ , Kowl er E, Pa lm er C . Sm oo t h pursuit o f small - a mplitud e sinu soidal  motion. J Opt S oc  393 \nAm A 198 5 Feb;2(2 ):234–24 2 .  394 \n18.S alman  MS, Sh arpe JA, Li llaka s  L , D en nis M, S tei nbach MJ . Smo oth pu rs uit eye  moveme nts in 395 \nch ildren. Ex p Brain R e s  20 06 Fe b;169(1 ): 139– 143.  396 \n19.S chröde r R, K eidel K, Tra utne r P, R a dbr u ch A, E t ting er U . N eu ral  mech ani sm s  of  b ack ground and  397 \nve locity  ef fect s in smoo th pur s u i t  eye m o vement s. Hum Br ain Ma pp 2023 Feb 15 ;44(3) :1002– 1018.  398 \n20.Ge r sch TM, Kowler E , Sc hnitzer BS , Do s he r BA . A t ten tion d ur i ng sequ enc e s  o f  sac ca de s  along 399 \nmarke d and me morized  pa th s . Vis i o n Re s 2009 Jun;4 9 (10) :1256– 1266.  400 \n21.Hutt on SB.  Cognitiv e con trol o f sac ca di c ey e mov ement s .  B r a in C ogn  2008 De c ;68(3):327 – 340.  401 \n22.P ie rce, J .E ., Cleme n t z, B .A ., Mc D owell ,  J.E. Sa cc ad e s: Fund a ment al s and Ne ural  M e chani s ms . In: 402 \nKlei n, C. , E t ting e r, U ,  e dito r. Eye  Movem en t  Re sea r c h : Spring er , Cham ; 2 019.  403 \n23.Ma t h ôt S . Pupil lom etry: P sych ology,  P hysiolog y, and  Func ti on. J Cogn 2018 F eb 21;1(1):1 6 .  404 \n24.Wic krema singhe  SS ,  Smith GT, S teven s J D. Compari so n of dy namic  digita l pupil l ometr y  and st atic 405 \nmea s u remen t s o f pupil  s i ze i n de termini ng s c otopic pupil size  be for e re frac tiv e su r g er y . J Cat arac t 406 \nRef rac t  Surg 2005  Jun ;31(6 ):1171 –1176 .  407 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n21 \n \n25.S chmitz S, Kr um menau er F , He nn S, Dic k HB. Co mpari s o n  of t hr e e dif fe ren t tec hn ologie s fo r pupil  408 \ndia mete r  mea sure men t. G r a e fe s  Arc h Cli n E xp Ophthalmo l 2003 J un ;241 (6) :472– 4 77. 409 \n 410 \nAck nowledge ment s: 411 \nWe tha nk  Vince n t  D w ian ta a nd Gur t ek  Sam r a  fo r  t he i r  in s i ght on P upi lLabs Ne on g las s e s se tup. We 412 \nthank  De nni s H e n s  a nd t he Bulbi CAM  t e c hnic al tea m for  troub l e shooti ng  techni ca l chal lenge s a s 413 \nrequir ed du r in g th e s tudy.  414 \nAuthor  contr i but ions 415 \nMT, IK : study  de sign; MT: s up ervi s i on  of the projec t ; IK, R M: da ta colle cti on; MT,  I K, HY: da t a  416 \nex t rac tio n ana ly sis; IK, RS: d r a f tin g th e or igin al man us c r i p t ; M T , EML,  Q A : fun di ng ac quisi tion; MT, 417 \nIK, E ML, QA , VR , HY, RS , RM, RS , ZT: c r i t i cal r e view  of t he manu s c r ip t.  418 \nAll a utho rs hav e gi ven thei r a pproval for the publi sh ed ve rsion o f t he  man usc ript .  419 \nConflic t  of  Int e r est  420 \nNo con f l ic ting r e la tion ship ex i s t s for any a uthors .  421 \nFundi ng  422 \nThis study w as  s up por ted by  the M edic al  Re sea r c h Counc il (M RC ), L ondon , UK (gr ant num ber:  423 \nMR/X502777/1 ) an d th e Ulver scro ft F ou ndatio n .   424 \n 425 \n 426 \nSumma r y  427 \nWhat wa s  k nown be for e ?  428 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint \n\n22 \n \n• Ey e-t r ac king  devi ces a re e s se ntial i n n eur o-oph thalmic  re s earch a nd cl inica l p racti c e, 429 \nof fering k ey i n s ig ht s  in t o ocul a r  a nd n eur olog ical  functi on.  430 \n• VR hea dset -ba s ed e ye t rack er s  o ff er ob je ctive  as se ssm ent me thod s in a porta bl e, al l-in -on e 431 \nco mpact sy st em.  432 \n• VR ey e t rack ing sy ste ms  a r e  und er -expl o r e d compa re d to t r a di tional sy stem s and  no  433 \nreprod uci bility or r eli ability  s tu die s ha ve bee n con duct ed on VR head s et -ba se d ey e  tr a cke rs 434 \nto dat e.  435 \nWhat t his study  add s?  436 \n• Par tic ipant fe edba ck highlig hted hig h ac c eptabil i ty; whi le pa ire d a s s e s s m en t be twee n 437 \ndev ices (Bulbi CAM  an d Pupi lLab s N eon e y e track ing g las s e s ) showed st rong ag r e e ment 438 \nco nfir m ing Bulbi CAM’s relia bili ty.  439 \n• VR hea dset e ye trac king d evic e Bulbi cam  de monstra ted h igh r eprod uc ibility f o r p ursui t 440 \nand pupil te s t s ; w hile sac cad e te s t s h ad l ower rep roduc ibility ou t c ome s.  441 \n• In fu ture , port able  VR he ad set s coul d pl a y a ke y role i n expa nding point -o f- c a re 442 \nas s e ssme nt s  in va r io u s  se tting s.  443 \n 444 \n 445 \n 446 \n 447 \n 448 \n . CC-BY 4.0 International licenseIt is made available under a \n is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)\nThe copyright holder for this preprint this version posted June 20, 2025. ; https://doi.org/10.1101/2025.06.18.25329788doi: medRxiv preprint","source_license":"CC-BY-4.0","license_restricted":false}