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O iginal A icle | O o hinola yngology: Oph halmology & Op ome y
Compa a i e analysis o an e io co neal su ace cha ac e is ics
measu ed by wo opog aphe s and wo au oke a ome e s
Ve ónica Noya-Padin1,2^, Hugo Pena-Ve deal1,2^, Jacobo Ga cía-Quei uga1,2,3^, Noelia No es-Palmas1^,
Alba Cas o-Gi aldez1^, E a Yeb a-Pimen el1,2
1Depa amen o de Física Aplicada (Á ea de Op ome ía), Facul ade de Óp ica e Op ome ía, Uni e sidade de San iago de Compos ela, San iago de
Compos ela, Spain; 2Heal h Resea ch Ins i u e o San iago de Compos ela (IDIS), San iago de Compos ela, Spain; 3Facul ad de Óp ica y Op ome ía,
Uni e sidad de San iago de Compos ela, San iago de Compos ela, Spain
Con ibu ions: (I) Concep ion and design: All au ho s; (II) Adminis a i e suppo : H Pena-Ve deal, E Yeb a-Pimen el; (III) P o ision o s udy
ma e ials o pa ien s: J Ga cía-Quei uga, H Pena-Ve deal, A Cas o-Gi aldez; (IV) Collec ion and assembly o da a: J Ga cía-Quei uga, H Pena-
Ve deal, A Cas o-Gi aldez; (V) Da a analysis and in e p e a ion: H Pena-Ve deal, E Yeb a-Pimen el; (VI) Manusc ip w i ing: All au ho s; (VII)
Final app o al o manusc ip : All au ho s.
Co espondence o: Jacobo Ga cia-Quei uga, OD, MSc, PhD. Facul ad de Óp ica y Op ome ía, Uni e sidad de San iago de Compos ela, Campus Vida
s/n, 15782 San iago de Compos ela, Spain; Depa amen o de Física Aplicada (Á ea de Op ome ía), Facul ade de Óp ica e Op ome ía, Uni e sidade
de San iago de Compos ela, San iago de Compos ela, Spain; Heal h Resea ch Ins i u e o San iago de Compos ela (IDIS), San iago de Compos ela,
Spain. Email: [email p o ec ed].
Backg ound: P ecise quan i ica ion o co neal pa ame e s enhances he clinical o he an e io co neal
su ace o a ious clinical assessmen s, wi h ongoing esea ch ocusing on op imizing e e yday p ac ice
h ough de ice compa ison s udies. The s udy aimed o compa e he ag eemen on he an e io co neal
su ace cha ac e is ics alues measu ed by ou comme cially a ailable de ices: EyeSys 2000, Oculus
Easyg aph, ARK700A and ARK510A.
Me hods: Obse a ional c oss-sec ional s udy in ol ing 50 eyes om heal hy olun ee ec ui ed among
subjec s a ending o an eye examina ion. Co neal adius minimum ke a ome y eading (min-K) and
maximum ke a ome y eading (max-K), as igma ism axis and eccen ici y we e measu ed in all pa icipan s
wi h EyeSys, Oculus Easyg aph, ARK700A and ARK510A. Measu emen s we e pe o med h ee imes
only in he igh eye in andom o de by ou op ome is s who we e unawa e o he esul s o he o he
esea che s.
Resul s: A s a is ically signi ican di e ence occu ed o he measu emen s o he co neal adius
(G eenhouse-Geisse and Huynh-Feld : P≤0.001 o bo h max-K and min-K adius) and he axis o
as igma ism (F iedman: P<0.001), be ween he ou de ices. Pai wise compa isons e ealed no adius
di e ences be ween Oculus Easyg aph and ARK510A (Sidak: min-K adius, P=0.231; max-K adius,
P=0.224), and no axis di e ences in all pai wise analyses ha ha e no imply he EyeSys (Wilcoxon: all
P≥0.130). The e was no s a is ical di e ence in he eccen ici y alue ob ained by he opog aphe s (pai ed
- es : P=0.507).
Conclusions: The p esen s udy showed ha EyeSys 2000 measu emen s di e ed om hose o he o he
de ices ac oss all pa ame e s. Al e na i ely, bo h opog aphe s showed a pe ec ag eemen conce ning
eccen ici y measu emen s in e e yday p ac ice.
Keywo ds: Ag eemen co neal opog aphe s; ag eemen au oke a ome e s; EyeSys; Easyg aph; ARK
8
^ ORCID: Ve ónica Noya-Padin, 0000-0002-2815-3653; Hugo Pena-Ve deal, 0000-0001-5103-1374; Jacobo Ga cía-Quei uga, 0000-0001-
7216-4512; Noelia No es-Palmas, 0000-0001-8317-8039; Alba Cas o-Gi aldez, 0009-0000-1321-8154.
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In oduc ion
P ecise quan i ica ion o co neal opog aphy pa ame e s
p o ides a ool o de ine he op ical cha ac e is ics o he
an e io co neal su ace o a p ope con ac lens i ing as
well as a me hod o he ea ly diagnosis and moni o ing o
co neal ecs a ic diso de s, accu a e in aocula lens powe
calcula ions, and p epa a ion o co neal e ac i e su ge y
(1-3). Ke a ome y is a echnique ha measu es he cen al
a ea o he an e io co nea whe e wo axes 90° apa a e
de e mined. These wo axes a e he s eepes and he la es
me idians o he cen al a ea o he an e io co nea. The
s eepes me idian has he highes adius o cu a u e, which
i s wi h he maximum ke a ome y eading (max-K). On
he o he hand, he la es me idian is he smalles adius o
cu a u e, ha i s wi h he minimum ke a ome y eading
(min-K) and is pe pendicula o he max-K (4).
Ke a ome ic measu emen s can be acqui ed using ei he
con en ional ke a ome y o co neal opog aphy (2,5-8).
These de ices p o ide clinicians wi h he cha ac e is ics o
he an e io su ace o he co nea based on he wo p incipal
adii (min-K and max-K), he as igma ism axis and he shape
ac o (2). The an e io co neal cu a u e adius de e mines
wo- hi ds o he op ical e ac i e powe o he eye and is
hus a ele an pa ame e o he ocula op ical sys em (9).
The shape ac o o he co nea can be desc ibed in e ms
o eccen ici y based on he ma hema ical desc ip ion o
an ellipse om 0.00 (a ci cle wi h no la ening) o 1.00
(maximum la ening in he pe iphe y) (10); his pa ame e
is usually only p o ided by he opog aphe s, howe e , he
p oblem wi h hese ins umen s is ha hei sophis ica ion
ine i ably induces a penal y in e ms o cos and he
induc ion o o he e o s because o he cap u e sys ems
used, while an assessmen o co neal opog aphy using a
simple ins umen like ke a ome e s p o ides he possibili y
o opog aphical assessmen o he clinician wi h access
only o basic ins umen a ion.
The di e ences o he p ecision and compa ison be ween
de ices a e s ill a ele an esea ch opic o he op imiza ion
o he e e yday p ac ice (1,11-13). The p esen s udy aimed
o compa e he ag eemen o he an e io co neal su ace
cha ac e is ics alues measu ed by ou comme cially
a ailable de ices ( wo co neal opog aphe s and wo
au oke a ome e s): he EyeSys 2000 (EyeSys Vision, Uni ed
S a es), he Oculus Easyg aph (Oculus Op ikge ä e GmbH,
Ge many), he ARK700 (Nidek Technologies, I aly), and
ARK510A (Nidek Technologies).
Me hods
S udy design
Measu emen s we e pe o med in andom o de
using ou de ices, wo co neal opog aphe s and wo
au oke a ome e s, ollowing manu ac u e ’s ins uc ions:
(I) EyeSys Co neal Analysis Sys em 2000, (II) Easyg aph,
(III) ARK700, and (IV) ARK510A (5-8). Co neal adius
(min-K and max-K) and as igma ism axis we e measu ed by
all he de ices, while he eccen ici y alues we e measu ed
only wi h he Oculus Easyg aph and he EyeSys 2000
opog aphe s. All measu emen s we e pe o med h ee
imes on each de ice only in he igh eye o each subjec
o a oid o e s a ing he p ecision o s a is ical es ima es by
ou expe op ome is s who we e no awa e o he esul s
o he o he esea che s (14).
Sample
Fi y olun ee pa icipan s (mean age =22.9±5.85 yea s;
ange, 19–29 yea s) we e ec ui ed among s uden s and
pa ien s a ending he cen e o an eye examina ion.
Pa icipan s we e excluded i hey had a his o y o
conjunc i al, scle al, o co neal disease, p io eye su ge y,
Highligh box
Key indings
• Ag eemen c oss-sec ional be ween de ices on co neal su ace
measu emen s.
Wha is known and wha is new?
• Di e ences in co neal adius and axis measu emen s be ween
de ices was ound. Oculus Easyg aph and ARK510A showed no
di e ence in adius measu emen .
Wha is he implica ion, and wha should change now?
• EyeSys 2000 showed di e ences in axis measu emen s wi h he
o he de ices. The e was no di e ence in he eccen ici y alue
ob ained by he opog aphe s.
Recei ed: 29 Decembe 2023; Accep ed: 11 June 2024; Published online: 23 July 2024.
doi: 10.21037/amj-23-257
View his a icle a : h ps://dx.doi.o g/10.21037/amj-23-257
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d y eye disease, meibomian gland dys unc ion, glaucoma,
diabe es melli us, a hy oid diso de , wo e con ac lenses,
we e p egnan o b eas eeding (15,16). Pa icipan s we e
only included i hei e ac i e sphe ical e o was less han
±6.00 D and/o as igma ism was less han 4.00 D (17). No
one pa icipan was unde any ype o opical o sys emic
medica ions o used a i icial ea s a he ime o he s udy
ha could in luence he measu emen s. To elimina e any
diu nal a ia ion in co neal cu a u e o ea physiology, all
measu emen s we e made in he mo ning a he same hou
be ween 10:00 and 12:00 am (6,18).
S a is ical analysis
SPSS s a is ical so wa e .23.0 o Windows (SPSS Inc.,
Uni ed S a es) was used o da a analysis. Signi icance was
se a a P≤0.05 o all s a is ical es s (19). Be o e analysis,
he no mal dis ibu ion o he da a was checked using he
Kolmogo o -Smi no es .
Radius alues showed a no mal dis ibu ion
(Kolmogo o -Smi no es : P≥0.074 o all he examined
alues), he e o e di e ences be ween measu emen s on
de ices we e assessed using G eenhouse-Geisse o Huynh-
Feld co ec ion based on Mauchly’s W es o sphe ici y,
while pai wise analysis was pe o med using he Sidak
pos -hoc es (20). Since he axis showed a non-con inuous
dis ibu ion (Kolmogo o -Smi no es : P≤0.001 o all he
examined alues), di e ences in his pa ame e be ween
de ices we e assessed using he F iedman es , while he
Wilcoxon es was used o de ec signi ican pai wise
di e ences; o a oid ype I e o s a ising om mul iple
compa isons in he axis alues, s a is ical signi icance o he
Wilcoxon es o be di ided by he numbe o compa isons
pe o med o gi e a P≤0.0083 (Bon e oni adjus men ) (21).
Eccen ici y alues showed a no mal dis ibu ion
(Kolmogo o -Smi no es : all P≥0.194). Fo eccen ici y
ag eemen be ween opog aphe s, Bland-Al man’s
p ocedu es we e used. This me hod desc ibes he
co ela ion o simila i y be ween wo a iables, ep esen ing
a e ages e sus di e ences (19,22). Thus, di e ences
be ween he se s o measu emen s ob ained in he wo
sessions we e examined. Di e ences we e assessed using
a pai ed - es o ela ed samples and 95% limi s o
epea abili y we e also calcula ed [mean di e ence ± 1.96
× s anda d de ia ion (SD) di e ences] (19); 95% limi s o
ag eemen (95% LoAs) we e also calcula ed (mean di e ence
± 1.96 × SD), as well as he exac 95% con idence in e als
(95% CIs) o uppe and lowe LoAs conside ed as a pai
(mean di e ence ± c 0.025 × SD; mean di e ence ± c 0.975 ×
SD) (19,23).
E hical conside a ion
The s udy was conduc ed in acco dance wi h he
Decla a ion o Helsinki (as e ised in 2013). The s udy
was app o ed by he E hics Commi ee o Uni e sidade
de San iago de Compos ela (USC-40/2020) and in o med
consen was aken om all indi idual pa icipan s.
Resul s
The e was a s a is ical di e ence in he measu emen s o
bo h co neal adii, max-K [Mauchly’s W es : P=0.001,
epsilon (ε) =0.561; Huynh-Feld co ec ion: P<0.001,
Table 1] and min-K (Mauchly’s W es : P<0.006, ε =0.847;
G eenhouse-Geisse co ec ion: P<0.001, Table 1), be ween
he ou de ices. Pai wise compa isons showed ha his
di e ence was no ue when compa ing Oculus Easyg aph
opog aphe and ARK510A au oke a ome e s (Sidak es :
min-K adius, P=0.23; max-K adius, P=0.22, Table 2),
whe eas he e was a s a is ically signi ican di e ence o he
emaining compa isons (Sidak es : all compa isons max-K
o min-K adius, P≤0.02, Table 2).
The e was a s a is ical di e ence in he measu emen s o
he as igma ism axis be ween he ou de ices (F iedman es :
P<0.001). The pai wise analysis showed ha he EyeSys 2000
esul s we e s a is ically signi ican ly di e en om he o he
de ices (Wilcoxon es : all P≤0.001, Table 2), while all he
o he de ices showed no pai ed di e ences be ween hem
(Wilcoxon es : all P≥0.13, Table 2).
The e was no s a is ical di e ence in he eccen ici y
alue ob ained by he wo opog aphe s (pai ed - es :
P=0.51, Table 3 and Figu e 1).
Discussion
In clinical p ac ice, accu a e co neal opog aphy
measu emen s a e essen ial o con ac lens i ing o
he de ec ing o signi ican co neal shape al e a ions.
The measu emen o he an e io co neal cu a u e o
ke a ome y could be pe o med wi h a a ie y o de ices.
Conside ing he mean di e ence and he 95% LoAs o
max-K o he min-K measu emen s, he wo s ag eemen
was ob ained be ween he EyeSys 2000 agains he o he
de ices; his de ice o e es ima ed he adius alues o he
o he de ices. In e -de ice di e ences, al hough small (nea
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Table 1 Desc ip i e s a is ics and di e ence analysis be ween he la o he s eepe adius alues ob ained in each de ice
Pa ame e De ice Mean/median SD/IQR P alue
max-K (mm) EyeSys 2000 7.81 0.26 <0.001†
Oculus Easyg aph 7.72 0.26
ARK700 7.74 0.26
ARK510A 7.70 0.28
min-K (mm) EyeSys 2000 7.93 0.30 <0.001‡
Oculus Easyg aph 7.87 0.29
ARK700 7.88 0.30
ARK510A 7.86 0.30
As igma ism axis (°) EyeSys 2000 159 131–168 <0.001§
Oculus Easyg aph 175 160–180
ARK700 176 144–1
ARK510A 176 147–180
N=50. Mean and SD displayed o pa ame ic a iables while median an IQR o non-pa ame ic a iables. †, Huynh-Feld co ec ion; ‡,
G eenhouse-Geisse co ec ion; §, F iedman es . SD, s anda d de ia ion; IQR, in e qua ile ange; max-K, maximum ke a ome y eading;
min-K, minimum ke a ome y eading.
Table 2 Analysis o di e ences o adios and axis esul s ob ained in each de ice
Pa ame e Pai Mean di e ence
± SD P alue
95% LoAs
Minimum (95% CI) Maximum (95% CI)
max-K (mm) EyeSys 2000-Oculus Easyg aph 0.06±0.034 <0.001†−0.006 (−0.023, 0.004) 0.125 (0.115, 0.143)
EyeSys 2000-ARK700 0.05±0.036 <0.001†−0.026 (−0.044, −0.015) 0.116 (0.105, 0.134)
EyeSys 2000-ARK510A 0.06±0.032 <0.001†0.002 (−0.015, 0.012) 0.126 (0.116, 0.143)
Oculus Easyg aph-ARK700 −0.01±0.033 0.003†−0.078 (−0.095, −0.068) 0.049 (0.039, 0.066)
Oculus Easyg aph-ARK510A 0.004±0.026 0.23†−0.046 (−0.059, 0.038) 0.055 (0.047, 0.068)
ARK700-ARK510A 0.02±0.023 <0.001†−0.026 (−0.038, −0.019) 0.064 (0.057, 0.076)
min-K (mm) EyeSys 2000-Oculus Easyg aph 0.09±0.047 <0.001†−0.003 (−0.027, 0.011) 0.182 (0.167, 0.206)
EyeSys 2000-ARK700 0.08±0.040 <0.001†−0.002 (−0.022, 0.010) 0.154 (0.142, 0.174)
EyeSys 2000-ARK510A 0.10±0.090 <0.001†−0.073 (−0.119, −0.045) 0.282 (0.254, 0.328)
Oculus Easyg aph-ARK700 −0.01±0.038 0.02†−0.091 (−0.111, −0.079) 0.064 (0.052, 0.085)
Oculus Easyg aph-ARK510A 0.02±0.087 0.22†−0.156 (−0.200, −0.129) 0.186 (0.159, 0.231)
ARK700-ARK510A 0.03±0.085 0.02†−0.138 (−0.181, −0.112) 0.195 (0.169, 0.239)
As igma ism
axis (°)
EyeSys 2000-Oculus Easyg aph −14.4±14.69 <0.001‡−43.16 (−50.66, −38.62) 14.42 (9.88, 21.92)
EyeSys 2000-ARK700 −10.5±14.60 <0.001‡−39.11 (−46.56, −34.59) 18.11 (13.59, 25.55)
EyeSys 2000-ARK510A −11.7±1.68 <0.001‡−32.63 (−38.08, −29.33) 9.23 (5.93, 14.68)
Oculus Easyg aph-ARK700 3.9±2.25 0.61‡−35.81 (−46.15, −29.55) 43.55 (37.29, 53.89)
Oculus Easyg aph-ARK510A 2.7±11.93 0.13‡−2.71 (−26.80, −17.02) 26.05 (22.36, 32.14)
ARK700-ARK510A −1.2±12.50 0.26‡−25.71 (−32.09, −21.84) 23.31 (19.44, 29.69)
N=50. †, Sidak es ; ‡, Wilcoxon es . SD, s anda d de ia ion; LoAs, limi s o ag eemen ; CI, con idence in e al; max-K, maximum
ke a ome y eading; min-K, minimum ke a ome y eading.
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o o e 0.10–0.20 mm), we e sugges ed o be clinically
signi ican o ce ain applica ions such as con ac lens
i ing and ollow-up examina ions. The same si ua ion
could be obse ed on he as igma ism axis measu emen ,
whe e he EyeSys 2000 de ice may gene a e di e ences
wi h he o he de ices highe han 10°, which could highly
comp omise a decision o e alua ion o he ini ial con ac
lens chosen du ing a i ing p ocedu e. F om he s udied
de ices he e, he EyeSys 2000 is one o he mos assessed o
accu acy o epea abili y in he li e a u e (5,24-26). P e ious
s udies o he EyeSys 2000 showed accep able epea abili y
o ag eemen wi h o he de ices in he measu emen o
cu a u e pa ame e s on human co neas o calib a ed
e e ence s anda ds (5,25,27), while highe dispa i y was
ob ained on he as igma ism axis assessmen han o he
de ices o in he accu acy while he measu ed su ace
become mo e min-K la ening (5,26,27).
To he au ho s’ knowledge, whe eas a s a is ically
signi ican di e ence occu ed wi h he Oculus Easyg aph,
his de ice was used in p e ious esea ch on co neal op ical
quali y and ke a ome y assessmen (7,8). In he p esen
s udy, a lowe alue o mean di e ence min-K, max-K,
o he axis when he eadings we e compa ed o he
au o e ac ome e esul s. Howe e , while mos o he 95%
LoAs seem o be na ow, a ew o hem showed a bias ha
could comp omise a clinical se ing (e.g., min-K: Oculus
Easyg aph-ARK510A, 95% LoAs =−0.156, 0.186; axis:
Oculus Easyg aph-ARK700, 95% LoAs =−35.81, 43.55). I
was p e iously s a ed hose di e ences could be a ibu ed
o he measu emen a ea o each de ice such as he
no mal p ola e shape o he co nea is max-K in he cen e
and highe K- eadings should be expec ed wi h smalle
measu emen a eas (4).
Bo h s udies au oke a ome e s s udied showed a
eliable ag eemen be ween hem when min-K o axis was
compa ed, whe eas di e ences we e ound ega ding he
max-K measu emen s whe e ARK700 o en o e es ima ed
he alues in e e ence o ARK510A eadings; ne e heless,
he mean di e ences ound could be conside ed non-
clinically ele an (max-K: ARK700-ARK510A, mean
di e ence ± SD =0.02±0.023 mm). O he au oke a ome e s
models we e also s udied by o he au ho s, showing good
epea abili y and ag eemen when compa ed wi h o he
au oma ed de ices and manual Ja al ke a ome e s (4). On
he o he hand, in conco dance wi h p esen esul s o he
s udies ha e p oposed ha EyeSys 2000 and he au oma ed
ARK700A ke a ome e lack in e changeabili y in hei
esul s (6).
Eccen ici y could be de ined as he la ening a e o
he cen al cu e adius o a su ace and is a way o quan i y
asphe ic changes ac oss he diame e o ha cu e (10); he
highe he alue, he mo e quickly he su ace la ens om
he cen e o he pe iphe y (10). This a iable has a ele an
in luence on he gas pe meable i ing and e alua ion
p ocess (e.g., i egula co neas o o ho-k i ing) (28).
In he p esen s udy, EyeSys 2000 and Oculus Easyg aph
Table 3 Desc ip i e s a is ics and pai ed - es be ween he eccen ici y esul s ob ained in each opog aphe
De ice Mean ± SD Mean di e ence ± SD P alue
95% LoAs
Minimum (95% CI) Maximum (95% CI)
EyeSys 2000 0.458±0.083 −0.009±0.097 0.51 −0.200 (−0.250, −0.170) 0.182 (0.151, 0.231)
Oculus Easyg aph 0.467±0.130
N=50. SD, s anda d de ia ion; LoAs, limi s o ag eemen ; CI, con idence in e al.
0.27
0.22
0.17
0.12
0.07
0.02
−0.03
−0.08
−0.13
−0.18
−0.23
−0.28
Oculus easyg aph-EyeSys 2000
0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65
(Oculus easyg aph + EyeSys 2000)/2
Figu e 1 Mean e sus di e ences (Bland-Al man plo ) be ween he
eccen ici y alues ob ained by he wo de ices in 50 pa icipan s.
The hick solid ho izon al line indica es he mean di e ence while
he hin solid ho izon al lines he 95% LoAs (mean di e ence ±
1.96 × SD). The dashed ho izon al lines indica e he 95% CI o
he LoAs. LoAs, limi s o ag eemen ; SD, s anda d de ia ion; CI,
con idence in e al.
AME Medical Jou nal, 2024Page 6 o 8
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showed a high conco dance in he eadings o his
pa ame e (eccen ici y: EyeSys 2000-Oculus Easyg aph,
mean di e ence ± SD =−0.009±0.097). A ew esea che s
ha e s udied he ag eemen in he eccen ici y alues
be ween di e en comme cially a ailable opog aphe s,
whe e signi ican di e ences among hem we e ound (29).
I has been hypo hesized ha he di e ences in he
eadings o all hose pa ame e s be ween de ices could be
mos likely due o he di e en imaging me hods used by
each de ice (29,30); opog aphe s a e based on an image
cap u e o he Placido disc e lec ion om he an e io
co nea while ke a ome y is based on he p o es a ion and
size measu emen o an image in he co nea assumed as a
con ex mi o (29,30). In addi ion, i has been p oposed
ha di e ences be ween ke a ome y assessmen s could
eme ge om no consis en use o an index o e ac ion o
measu emen a ea ( he close o he cen e, he max-K he
co nea will appea ) by manu ac u e s (4). On he o he hand,
he di e ences could eme ge om he cap u e imes (30);
opog aphe s equi e a longe cap u e ime o acqui e
mul iple images o o ocus he image an au oke a ome e s,
he e o e ac o s such as he ixa ion o he subjec ,
compensa o y saccadic mo emen s, and abili y o keep he
eye open may in luence on he measu emen s.
The p esen esul s a e limi ed by he sample used, which
despi e he ac i was ela i ely la ge (50 pa icipan s), was
only composed o heal hy pa icipan s. Fu u e s udies on
hose de ices should include a second g oup composed o
a well-designed g oup wi h a speci ic co neal opog aphic
dis up ion condi ion (e.g., Ke a oconus o pos -Lasik
pa ien s) in o de o enhance he applica ions o he inding.
Conclusions
As p e iously indica ed, he indings o his s udy
demons a e ha he EyeSys 2000 lacks ag eemen wi h
he o he de ices unde examina ion ac oss any o he
pa ame e s in es iga ed, while bo h he Oculus Easyg aph
and ARK510A display comple e in e changeabili y.
Howe e , bo h examined opog aphe s showed pe ec
ag eemen in eccen ici y measu emen s o e e yday
p ac ice.
Acknowledgmen s
Funding: None.
Foo no e
Da a Sha ing S a emen : A ailable a h ps://amj.ameg oups.
com/a icle/ iew/10.21037/amj-23-257/dss
Pee Re iew File: A ailable a h ps://amj.ameg oups.com/
a icle/ iew/10.21037/amj-23-257/p
Con lic s o In e es : All au ho s ha e comple ed he ICMJE
uni o m disclosu e o m (a ailable a h ps://amj.ameg oups.
com/a icle/ iew/10.21037/amj-23-257/coi ). The au ho s
ha e no con lic s o in e es o decla e.
E hical S a emen : The au ho s a e accoun able o all
aspec s o he wo k in ensu ing ha ques ions ela ed
o he accu acy o in eg i y o any pa o he wo k a e
app op ia ely in es iga ed and esol ed. The s udy was
conduc ed in acco dance wi h he Decla a ion o Helsinki
(as e ised in 2013). The s udy was app o ed by he E hics
Commi ee o Uni e sidade de San iago de Compos ela
(USC-40/2020) and in o med consen was aken om all
indi idual pa icipan s.
Open Access S a emen : This is an Open Access a icle
dis ibu ed in acco dance wi h he C ea i e Commons
A ibu ion-NonComme cial-NoDe i s 4.0 In e na ional
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