Transcript Corneal Spherical Aberration in a Population of Patients

Corneal Spherical Aberration in a
Population of Patients Measured by 3
Different Instruments
Background

Spherical aberration (SA) is a fourth-order higher-order
aberration in which peripheral light rays are refracted
more than the central ones

Can be positive or negative depending on where the light
rays focuses

Leads to image spread on the retina instead of point
focus

Average cornea SA is +.27µ compensated by the lens
negative SA in healthy individuals.

After cataract surgery, if a spherical IOL is implanted, it
will add more positive SA to the eye
Background

Several aspheric monofocal IOLs have been developed
with different SA values to compensate for the corneal SA
 Tecnis Z9000
 AcrySof SN60WF
 nanoFLEX Collamer
 Sofport AO
Tecnis
SN60WF
-.27µ
-.20µ
-.019µ
0
Sofport AO
nanoFLEX
Background

Literature suggests getting the patient closest to 0 SA to
achieve the optimum quality of vision

Correct selection of the aspheric IOLs will depend mainly
on SA measurements of the cornea
Purpose

To compare the measurements of corneal spherical
aberration obtained by the Atlas Corneal Topography
(Carl Zeiss, Jena, Germany), Galilei Dual Scheimpflug
Analyzer (Ziemer, Port, Switzerland) and the OPD-Scan
II (Nidek, Tokyo, Japan).
Atlas Corneal
Topography
Galilei Dual Scheimpflug
Analyzer
OPD-Scan II
Methods

A pilot study

SA were measured in patients undergoing cataract surgery
before dilation.

SA measured in the 6 mm optical zone

No history of ocular surgery or injury

No ocular pathology other than cataract

All measurements were done by single trained observer

Difference between measurements were analyzed
Methods
Reports from the 3 tested instruments
Measurements
8 eyes of 6 patients
All females
Average age: 73 years ( 63-81)
Atlas
Galilei
OPD
Eye 1
0.226
0.37
0.267
Eye 2
0.274
0.25
0.129
Eye 3
0.094
0.18
0.206
Eye 4
0.18
0.3
0.217
Eye 5
0.341
0.29
0.255
Eye 6
0.266
0.28
0.255
Eye 7
0.285
0.27
0.261
Eye 8
0.161
0.31
0.169
Average
0.220
(± 0.05)
0.281
(± 0.05)
0.228
(± 0.08)
Difference between Galilei and OPD
measurements compared to Atlas
Galilei - Atlas
OPD-Atlas
Eye 1
0.041
0.144
Eye 2
-0.145
-0.024
Eye 3
0.112
0.086
Eye 4
0.037
0.12
Eye 5
-0.086
-0.051
Eye 6
-0.011
0.014
Eye 7
-0.024
-0.015
Eye 8
0.008
0.149
Average
-0.009
(± 0.079)
0.053
(± 0.081)
Positive sign = overestimate
Negative sign = underestimate
Conclusion

This pilot study showed high consistency of
measurements of SA among the 3 tested
instruments

This finding can help the surgeons choose the
proper aspheric IOL regardless of which
measuring instrument is used.

More studies are needed to determine the
optimal SA surgeons need to target