The Analysis of Corneal Asphericity and its Related Factors in Cataract Patients

Abstract

Purpose: To determine the corneal asphericity and its related factors in cataract patients.
Methods: This study enrolled 121 eligible eyes of 121 cataract patients. The corneal Q values of anterior and posterior surface were measured in the central 3.0, 4.0, 5.0, and 6.0 mm zone using the Sirius System. Age, gender, and corneal higher-order aberrations (HOAs) were recorded. Comparison of preoperative and postoperative Q value was conducted in 103 eyes of 103 patients three months after surgery.
Results: The Q value of the anterior corneal surface at 6.0 mm zone and the posterior surface in 3.0, 4.0, 5.0, and 6.0 mm zone were statistically significant across the different age groups. The Q value of the posterior surfaces in 3.0, 4.0, 5.0, and 6.0 mm zone was statistically significant between the male and the female groups. The Q values of the anterior corneal surface in the 6.0 mm zone were positively correlated with Z4⁰ cornea, Z4⁰ CF, Z33,-3 CF, and total corneal HOAs; While the Q value of the posterior surface in the 6.0 mm zone were negatively correlated with Z31,-1 cornea, Z33,-3 cornea, Z33,-3 CF, Z31,-1CB, Z4⁰ CB, and total corneal HOAs. Besides, no significant change was found in corneal Q value 3 months after surgery.
Conclusion: There were great individual differences between the corneal asphericity of the cataract patients. Age, sex, and HOAs seemed to be correlated with the corneal asphericity. The preoperative Q value can be used as one of the parameters for personalized selection of intraocular lens.

Full text

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The Analysis of Corneal Asphericity and its Related
Factors in Cataract Patients
Chen Li
the First Aliated Hospital of Soochow University
Peirong Lu (  lupeirong@suda.edu.cn )
the First Aliated Hospital of Soochow University
Research Article
Keywords: cataract, corneal asphericity, aberrations
Posted Date: September 17th, 2021
DOI: https://doi.org/10.21203/rs.3.rs-798555/v1
License:   This work is licensed under a Creative Commons Attribution 4.0 International License. 
Read Full License

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Abstract
Purpose: To determine the corneal asphericity and its related factors in cataract patients.
Methods: This study enrolled 121 eligible eyes of 121 cataract patients. The corneal Q values of anterior
and posterior surface were measured in the central 3.0, 4.0, 5.0, and 6.0 mm zone using the Sirius
System. Age, gender, and corneal higher-order aberrations (HOAs) were recorded. Comparison of
preoperative and postoperative Q value was conducted in 103 eyes of 103 patients three months after
surgery.
Results: The Q value of the anterior corneal surface at 6.0 mm zone and the posterior surface in 3.0, 4.0,
5.0, and 6.0 mm zone were statistically signicant across the different age groups. The Q value of the
posterior surfaces in 3.0, 4.0, 5.0, and 6.0 mm zone was statistically signicant between the male and the
female groups. The Q values of the anterior corneal surface in the 6.0 mm zone were positively correlated
with Z40 cornea, Z40 CF, Z33,-3 CF, and total corneal HOAs; While the Q value of the posterior surface in the
6.0 mm zone were negatively correlated with Z31,-1 cornea, Z33,-3 cornea, Z33,-3 CF, Z31,-1CB, Z40 CB, and
total corneal HOAs. Besides, no signicant change was found in corneal Q value 3 months after surgery.
Conclusion: There were great individual differences between the corneal asphericity of the cataract
patients. Age, sex, and HOAs seemed to be correlated with the corneal asphericity. The preoperative Q
value can be used as one of the parameters for personalized selection of intraocular lens.
Introduction
The cornea is the most signicant refractive component in the eye, contributing a major share of around
70% of the refractive power. Previous researches demonstrated that the cornea could be described as a
quadric surface having asphericity on the surface.1,2 The radial variation from the center towards the
periphery of the quadric surface determines the Q value, the quantied aspherical degree indicator. The Q
value, being the crucial parameter of the mathematical cornea model, is reective of the shape of the
cornea and its optical properties. 3 Today, the corneal Q value along with its distribution properties have
garnered the focus of attention of the relevant studies, besides the manner in which the optical properties
are impacted in the eye. 4,5
Alongside the popularization and application of aberration theory in ophthalmology, the inuence of
corneal Q value on spherical aberrations following corneal refractive surgery and intraocular refractive
surgery is garnering an increasing amount of attention from ophthalmologists. Corneal Q value provides
an essential reference for personalized intraocular refractive surgery and aspheric intraocular lens (IOL)
implantation. Although corneal Q value in elderly populations is an essential factor in the design of IOL
procedures and for the treatment of refractive errors, there is little formal studies have been conducted to
evaluate its relevance for cataract patients.

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The Q value of different corneal surface areas is disparate, and a single value does not accurately reect
the shape of the cornea. 6 It is crucial to examine the Q value of different ranges to improve the visual
acuity of cataract patients following aspheric IOL implantation. Many different factors affect corneal Q
value. Previous studies have focused on the relationships among Q value, age, refractive error7, refractive
status8, and spherical aberrations9, while studies concerning Q value and other high-order aberrations
(HOAs) of the cornea are limited at present. In addition, the majority of previous studies focus on the Q
value of the anterior corneal surface, little attention has been paid to the posterior corneal surface, but it
does affect the optical properties of the eye.10 Previous studies have conrmed that LASIK can
signicantly change the asphericity of the anterior corneal surface and this morphological change have a
negative impact on visual quality. As a result, personalized keratotomy guided by topographic maps
came into being to reduce the negative effect. However, little is known about whether phacoemulsication
affects corneal asphericity. This study aims to determine the Q value of anterior and posterior corneal
surface in cataract patients and its characteristics and correlations with corneal HOAs. At the same time,
we observed the changes of Q value between preoperative and postoperative.
Method
Study population
This retrospective study recruited patients scheduled for cataract surgery, from July 31st, 2020 to May
31st, 2021, at the First Aliated Hospital of Soochow University, Suzhou, China. The grade of cataract
was assessed using a slit-lamp microscope and classied using the Lens Opacities Classication System
III (LOCS III). A total of 121 eyes of 121 cataract patients including 58 males and 63 females were
enrolled in the study after excluding patients who underwent ocular surgery or had corneal disease,
glaucoma, uveitis, dry eye or had worn contact lenses in the last 2 weeks, as well as patients with
incomplete topographical mapping, and/or poor repeated measurements during preoperative
examination. The study protocol adhered to the tenets of the Declaration of Helsinki and was approved
by the institutional review board of the First Aliated Hospital of Soochow University. Consenting to
allow their clinical data to be retrospectively evaluated, all the patients endorsed the consent letter with
their signature.
Surgical Technique
All operations were performed by one experienced surgeon (P.R.L), and using the centurion
phacoemulsication platform (Alcon Laboratories, Inc., Lake Forest, CA, USA) at the Cataract Center of
the First Aliated Hospital of Soochow University. The phacoemulsications were performed through a
2.2 mm corneal limbus incision, and all the patients underwent IOL implantation in the capsular bag. No
stitches were required in any of the patients in this study. Postoperative treatment consisted of 0.3%
Lavooxacin (Cravit, Santen Pharmaceutical Co, Ltd, Osaka, Japan) eye drops four times a day for 2
weeks and TobraDex (tobramycin 0.3%, dexamethasone 0.1%; Alcon, Fort Worth, TX, USA) eye drops four
times a day for 4 weeks.

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Method
Corneal topography measurement was repeated three times for all patients using Sirius (Sirius, CSO Inc,
Florence, Italy) system. The data were analyzed for the full topographic map measurements in the central
3.0, 4.0, 5.0, and 6.0 mm zones. All examinations were done by the rst author (C.L.), the corneal reex
rings were clear, and the tear lm rupture was not disturbed during the examinations. The Q value in the
central 3.0, 4.0, 5.0, and 6.0 mm zone was calculated by the Sirius system. The analysis of the correlation
between the HOAs and Q value, along with the mean corneal Q value (mean ± SD) having varying
diameters on the anterior and posterior surfaces were included in the results. The HOAs in pupillary areas
of 6.0 mm analyzed included the root mean square (RMS) values of primary spherical aberration (Z40),
primary coma aberration (Z31,−1), primary trefoil aberration (Z33,−3) of the total cornea, corneal front
surface, and corneal back surface and total corneal HOAs. The statistical analysis was conducted using
high centrality, high repeatability, and high quality aberration values. A classication of the device signal
according to the composite index of the keratoscopic and Scheimpug images with xation states,
described high quality. The high-quality images with the coverage of Scheimpug tomographic images
over 98% were used for analysis. The anterior and posterior difference of elevation < 5 mm and the
difference of the tangential anterior corneal curvature < 0.5D explained high repeatability. A percentage-
based signal of the device, according to a keratoscopic image of > 90% described high centrality. Three
months after the operation, 103 patients were examined again with the same method and the
corresponding data were recorded.
Statistical analysis
The SPSS software (version 25.0) was used for data analysis. The average Q value (mean ± SD) for
varying diameters was determined using descriptive statistics. Variance analysis (One-way ANOVA) was
used to compare the Q value for different diameters. Kruskal-Wallis H test was used to compare the Q
value for three age groups. T-test was performed to compare Q value between the male and female
groups, and to compare Q value before and 3 months after operation. Pearson’s correlation was used to
explore the relationship between corneal Q value and HOAs. We considered a p-value of < 0.05 to be
statistically signicant.
Results
Subject’s age distribution
In a range of 38–92 years, 67.44 ± 10.66 years was the average age. 5.79% of the subjects belonged to
the group aged 38 to 50 years, 51.24% belonged to the 50–70 years group, while 42.97% of the study
population was accounted for by persons aged 70 years and above. In this study, around 94.21% of the
population was composed of persons aged 50 years and above, the period was considered most prone to
develop senile cataract.
Corneal Q values

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The anterior surface indicated, respectively, the mean corneal Q values as: 0.09 (± 0.42), 0.02 (± 0.27),
-0.04 (± 0.20) and − 0.11 (± 0.17) in 3.0, 4.0, 5.0 and 6.0 mm zone. The mean Q values of the posterior
corneal surface were: 0.02 (± 0.81), -0.28 (± 0.56), -0.37 (± 0.43) and − 0.41 (± 0.30) in 3.0, 4.0, 5.0 and 6.0
mm zone, respectively (Table 1). The corneal Q value of anterior and posterior corneal surfaces decreased
with the enlargement of the measurement range (Table 1). The negative Q values of anterior surfaces
were 37.19%, 49.59%, 59.50%, and 76.86% of the total eyes. The negative corneal Q values of 3.0, 4.0, 5.0,
and 6.0 mm zone on the posterior surface were 44.63%, 69.42%, 80.99% and 95.04% of the total eyes. It
can be seen that the corneal Q values of most cataract patients were negative at the 6.0 mm diameter
zone of the cornea. That is to say, the anterior and posterior corneal surface of most cataract patients
was prolate.

Table 1
Corneal Q values.
diameter
(mm)
Q value (anterior) Q value (posterior)
Mean ± SD Negative constituent
ratio Mean ± SD Negative constituent
ratio
3.0 0.09 ± 0.42 37.19% 0.02 ± 0.81 44.63%
4.0 0.02 ± 0.27* 49.59% -0.28 ± 0.56* 69.42%
5.0 -0.04 ± 0.20** 59.50% -0.37 ± 0.43** 80.99%
6.0 -0.11 ±
0.17*** 76.86% -0.41 ±
0.30*** 95.04%
F 27.085  44.861 
p
< 0.001 < 0.001 
Note: "*" means compared with 3.0 mm diameter
p
< 0.05; "**" means compared with 4.0 mm
diameter
p
< 0.05; "***" means compared with 5.0 mm diameter
p
< 0.05.
Corneal Q value distribution at large zone of 6.0mm
In 121 eyes, the mean Q value of anterior corneal surface was: -0.11 ± 0.17, 95% condence interval (95%
CI): -0.07 ~ -0.14 (Fig. 1A), and that of posterior corneal surface was: -0.41 ± 0.30, 95% CI: -0.36 ~ -0.46
(Fig. 1B).
Corneal Q value of different age groups
Table 2 showed the distribution of the Q value at various stages of age. The study participants were
divided into three groups according to their ages: 38–49 years old; 50–69 years old; and ≥ 70 years old.
The one-way ANOVA analysis results indicate that the anterior corneal surface Q values of the ≥ 70 years
old group (in 6.0 mm zone) was signicantly higher than those of the 38–49 years old group; posterior

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corneal surface Q values (in 4.0 mm and 5.0 mm zone) of the ≥ 70 years old group were signicantly
lower than those of the 50–69 years old group; and the posterior corneal surface Q value (in 6.0 mm
zone) of the ≥ 70 years old group were signicantly lower than those of the 38–49 years old and 50–69
years old groups. It was quite evident that with increasing age, the Q value of the anterior surface of the
cornea also increased. Nevertheless, as indicated in Table 2, with an increase in the age, the posterior
surface Q value seemed to decrease.
Table 2
Corneal Q values for different age groups.
diameter
(mm)
Age Group (years old)
38–49 50–69 ≥ 70 χ2
p
3.0 (Anterior) 0.04(-0.09-0.34) 0.07(-0.09-0.24) 0.08(-0.14-0.24) 0.657 0.720
4.0 (Anterior) -0.06(-0.16-0.08) 0.03(-0.10-0.14) -0.02(-0.15-0.10) 1.072 0.585
5.0 (Anterior) -0.16(-0.21-0.01) -0.06(-0.16-0.09) -0.04(-0.17-0.06) 1.176 0.556
6.0 (Anterior) -0.22(-0.31-0.18) -0.10(-0.21-0.02) -0.10(-0.20-0.03)* 6.569 0.037
3.0 (Posterior) 0.14(-0.26-0.38) 0.24(-0.24-0.58) -0.06(-0.57-0.47) 4.376 0.112
4.0 (Posterior) -0.08(-0.16-0.01) -0.06(-0.28-0.21) -0.46(-0.68-0.12)# 15.702 < 0.001
5.0 (Posterior) -0.23(-0.27-0.08) -0.19(-0.39-0.02) -0.51(-0.77-0.32)# 20.448 < 0.001
6.0 (Posterior) -0.21(-0.39-0.17) -0.29(-0.44-0.18) -0.46(-0.68-0.38)*# 20.277 < 0.001
Note: "*" means compared with 38–49
p
< 0.05; "#" means compared with 50–69
p
< 0.05.
Corneal Q value in male and female groups
The mean Q value (mean ± SD) at varying diameters for both the female and male groups was
determined as indicated in Table 3. There was no signicant difference in Q values of anterior surface in
3.0, 4.0, 5.0, and 6.0 mm zone between female and male groups, whereas, for the posterior surface with
zone of 3.0, 4.0, 5.0, and 6.0 mm, the Q values were found to be signicant (
p
< 0.05) statistically. 

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Table 3
Corneal Q values for male and female groups.
diameter
(mm)
Male Female t
p
3.0 (Anterior) 0.11 ± 0.39 0.07 ± 0.45 0.397 0.692
4.0 (Anterior) 0.04 ± 0.28 -0.01 ± 0.25 1.131 0.260
5.0 (Anterior) -0.02 ± 0.21 -0.06 ± 0.19 0.944 0.347
6.0 (Anterior) -0.10 ± 0.17 -0.11 ± 0.17 0.377 0.707
3.0 (Posterior) -0.17 ± 0.87 0.19 ± 0.71 -2.505 0.014
4.0 (Posterior) -0.40 ± 0.59 -0.17 ± 0.51 -2.336 0.021
5.0 (Posterior) -0.47 ± 0.46 -0.28 ± 0.38 -2.404 0.018
6.0 (Posterior) -0.47 ± 0.33 -0.35 ± 0.26 -2.303 0.023
The correlations of corneal Q value and HOAs
Next, correlations between corneal Q values and HOAs were investigated. A linear correlation analysis
revealed that the Q value of the anterior surface (in 6.0 mm zone) positively correlated with total corneal
primary spherical aberration (Z40 cornea) (Pearson correlation = 0.796,
p
< 0.001); with primary spherical
aberration of the corneal front surface (Z40 CF) (Pearson correlation = 0.840,
p
< 0.001); with primary
trefoil aberration of the corneal front surface (Z33,−3 CF) (Pearson correlation = 0.236,
p
= 0.009) and with
total corneal HOAs (Pearson correlation = 0.305,
p
< 0.001) (Fig. 2). However, negative correlations were
found to exist between the Q value of the posterior surface (in 6.0mm zone) and total corneal primary
coma aberration (Z31,−1 cornea) (Pearson correlation=-0.212,
p
= 0.019); total corneal primary trefoil
aberration (Z33,−3 cornea) (Pearson correlation=-0.179,
p
= 0.049); primary trefoil aberration of the corneal
front surface (Z33,−3 CF) (Pearson correlation=-0.190,
p
= 0.037); primary coma aberration of the corneal
back surface (Z31,−1 CB) (Pearson correlation=-0.534,
p
< 0.001); primary spherical aberration of the
corneal back surface (Z40 CB) (Pearson correlation=-0.878,
p
< 0.001); and total corneal HOAs (Pearson
correlation=-0.220,
p
= 0.015) (Fig. 3).
However, no correlation was found to exist between the Q value of the anterior surface (in 6.0mm zone)
and total corneal primary coma aberration (Z31,−1 cornea); total corneal primary trefoil aberration (Z33,−3
cornea); primary coma aberration of the corneal front surface (Z31,−1 CF); primary coma aberration of the
corneal back surface (Z31,−1 CB); primary trefoil aberration of the corneal back surface (Z33,−3 CB); or
primary spherical aberration of the corneal back surface (Z40 CB). Similarly, no signicant correlation
was found to exist between the Q value of the posterior surface (in 6.0 mm zone) and total corneal

Page 8/15
primary spherical aberration (Z40 cornea); primary coma aberration of the corneal front surface (Z31,−1
CF); primary spherical aberration of the corneal front surface (Z40 CF); or primary trefoil aberration of the
corneal back surface (Z33,−3 CB).
The comparison of corneal Q value before and after
operation
Three months after surgery, a total of 103 patients were recorded, the Q value (in 6.0 mm zone) and visual
acuity due to 18 patients was lost to follow-up. As shown in Table 4, there was no signicant change in Q
values of anterior and posterior corneal surface at 3 months after operation. The results showed that our
phacoemulsication did not change the corneal Q value. 
Table 4
Comparison of corneal Q values before and after operation.
Q value eyes Pre Post 3M t
p
Anterior (6mm) 103 -0.10 ± 0.17 -0.11 ± 0.17 1.815 0.072
Posterior
(6mm)
103 -0.40 ± 0.31 -0.40 ± 0.30 -1.677 0.097
Discussion
The cornea is the rst surface of light gateway to the retina, representing two-thirds of the dioptric power
of the human eye, making it the most important refractive element. The parameter most used to describe
how the curvature of a parabola differs from the curve of a circle is the asphericity,Q value is one of the
most common and important parameters for describing the asphericity of the cornea. The Q value
characterizes the change on cornea curvature from the center to the periphery. When Q = 0, it represents a
circle, but if Q < 0 or Q > 0, it represents a prolate or oblate ellipse, respectively. 11 The anterior and
posterior surface corneal Q value with a zone of 6.0 mm were observed to be -0.11 ± 0.17 and − 0.41 ±
0.30, respectively in this study, whereas, in some earlier studies the corneal mean Q values were reported
as -0.22 (Cheung (Chinese), 12 -0.08 (Horner (Indian)), 13 -0.20 (Fuller (American Caucasian)) 4 and − 0.19
(Read (Australian)). 14 The subtle differences between our study and the earlier studies could have been
possibly due to the impact of various factors like age, race, sample size, and the differences in testing
equipment.
The anterior and posterior corneal surfaces were separately calibrated using the Sirius system in the
study, which we had used for a related study before.15 While some other studies had utilized varying
methods, like: Pentacam HR system, TMSI mapping system, and the EyeSys corneal topography. Sirius
system was routinely employed in research and clinical use, and preceding studies that measured
anterior segment parameters have demonstrated the system’s high degree of repeatability and
reproducibility. The system’s repeatability is akin to that reported for the Pentacam tomographers.16, 17

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Regarding the study of Q values across different ages, Dubbleman et al.18 investigated corneal
asphericity in 114 cases (aged between 18–65 years old), nding that the Q values increased with age.
Age-related changes in corneal thickness and asphericity are believed to be due to the increase in the
number of patients with corneal arcus senilis with age. Guirao et al.,19 examined changes in corneal
curvature across three groups, namely, young people (between 20–30 years old), middle-aged people
(between 40–50 years old), and elderly people (between 60–70 years old), nding that corneal asphericity
progressed and became increasingly circular (from oblate to round) with age. Out of the 1,991 subjects in
the study conducted by Davis 20 for the children in the age group of 6 to 15 years old, the mean Q value
they determined was found to be -0.346. The subjects in Zhang’s 5 studies were Chinese youngsters at an
average age of 25.4 years old with − 0.30 as the Q value. In our study, the average age of the subjects
was 67.44 years, the corneal Q value of the anterior surface with 6.0 mm zone was found to be much
higher in the group with an age above 70 years than in the group ranging from 38–49 years, which is
consistent with the previous study conducted by Dubbleman. However, few studies have measured the Q
values of the posterior corneal surface. Our results have shown that the Q value decreased signicantly
with age across the zone of 4.0 mm, 5.0 mm, and 6.0 mm. A correlation between sex and the Q value was
aptly established in our study. Scholz21 and Chan22 arrived at similar conclusions. For the anterior
surface in our study, the female group was found to have a smaller Q value than the male group. For the
posterior surface, the opposite was found and the difference was statistically signicant. However, sex
was found to be an irrelevant factor for the corneal Q value in the study conducted by Fuller 4, it may be
attributed to the difference in the subject’s age and race.
Wavefront aberration refers to the optical path difference between wavefront and ideal wavefront at each
point on the imaging plane of the eye. Some aberrations are the primary causes of glare, halos, and
decreased night vision in patients following cataract surgery, including total HOAs, spherical aberration,
coma, and trefoil aberration.23 The corneal Q value is a morphological parameter representing the
geometric shape of the cornea, whereas corneal aberration (e.g., spherical aberration) describes the
optical quality of the cornea and is representative of the degree of corneal optical error. However, few
studies have investigated the correlation between Q values and HOAs. Calossi11 analyzed the relationship
between asphericity and the degree of spherical aberration of the anterior corneal surface. It was found
that, as long as the corneal refractive index and the pupil diameter remained constant, the atter corneal
surfaces from the center to the periphery (negative Q value), the lesser degree of spherical aberration, and
steeper corneal surfaces from the center to the periphery (positive Q value) equated to greater degrees of
spherical aberration. Our results indicated that both the anterior and posterior surfaces of the cornea
correlate signicantly with the degree of spherical aberration of the corresponding ranges. That is to say
that, alongside higher Q value, the degree of spherical aberration increases accordingly, which is
consistent with previous studies. Coma and trefoil were both third-order aberrations, which reected the
asymmetry of refractive characteristics of the eye and were the representation of irregularity, inclination,
eccentricity, and other symmetry of the eye. Related studies have indicated that spherical and coma
aberration is associated with decreased visual acuity and contrast sensitivity in healthy people. In this
study, a positive correlation was found to exist between Q value and the degree of trefoil aberration of the

Page 10/15
front corneal surface, while a negative correlation exists between Q value and total coma aberration,
coma aberration of the corneal back surface, total trefoil aberration, and trefoil aberration of the front
corneal surface. These ndings suggest that evaluation of corneal Q-value before cataract surgery may
have certain signicant to the postoperative recovery of visual function and enhancing patients’ visual
quality.
There was no signicant change in Q value before and after surgery, which indicated that the surgery did
not cause corneal morphology change. The possible reason may be that all patients underwent limbal
incision with a length of 2.2 mm. Firstly, the incision was small enough and relatively far away from the
cornea. Secondly, the change of corneal vertical diameter was limited by the outer edge of the large
curved tunnel, so the change of corneal morphology was limited. It is important that the
phacoemulsication did not change the corneal Q value, because it is meaningful to observe whether the
preoperative corneal Q value can be used as a parameter for personalized selection of IOL, only when
there is no signicant change in the corneal Q value before and after surgery.
The present study differs from the previous studies in that the corneal Q values for 3.0mm, 4.0mm,
5.0mm, and 6.0 mm zone were tallied separately. It was found that the Q value relates to aperture size
and that the average values vary statistically across different diameters. Meanwhile, the Q values of the
posterior corneal surface were also examined. Although the posterior corneal surface is seldom relevant
in the design of refractive products, it does affect the optical properties of the eye. Prior research around
the Q value of the posterior corneal surface is limited. In conclusion, there were great individual
differences between the corneal Q values of the cataract patients. Age, sex, and HOAs seemed to be
correlated with the Q value. The preoperative Q value can be used as one of the parameters for
personalized selection of intraocular lens.
Abbreviations
HOAs: higher-order aberrations; IOL: intraocular lens; LOCS III: Lens Opacities Classication System III;
RMS: root mean square; CI: condence interval; CF: corneal front surface; CB: corneal back surface
Declarations
Acknowledgements
Not applicable.
Authors' contributions

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LC was involved in the study design, data collection, statistical analysis, and drafted the manuscript. LPR
was involved in the analysis and interpretation of study data. Both authors read and approved the nal
manuscript.
Funding
Design of the study and collection of data was supported by Soochow Youth Science and technology
project of invigorating health through science and education (No. KJXW2019008).
Availability of data and materials
The datasets analyzed during the current study are not publicly available for condentiality reasons;
nevertheless, the corresponding author will provide them on reasonable request. 
Ethics approval and consent to participate
This non-interventional retrospective chart-review study was approved by the ethics committee of the
First Aliated Hospital of Soochow University, and the committee waived the need for informed consent
from the patients because the data were anonymized. 
Consent for publication
Not applicable. 
Competing interests
The author declares no competing interests.
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J Refract Surg.
2009 May; 25(5):435–443.
3. Queiros A, Villa-Collar C, Jorge J, et al. Multi-aspheric description of the myopic cornea after different
refractive treatments and its correlation with corneal higher order aberrations.
J Optom.
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Figures
Figure 1
Corneal Q values distribution of the anterior (A) and posterior corneal surface (B).

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Figure 2
Correlations between Q value of anterior corneal surface and HOAs. (cornea=total cornea; CF=front
corneal surface; Z33, -3=primary trefoil aberration; Z40=primary spherical aberration; Total HOA
RMS=total corneal HOAs)

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Figure 3
Correlations between Q value of posterior corneal surface and HOAs. (cornea=total cornea; CF=front
corneal surface; CB=back corneal surface; Z33, -3=primary trefoil aberration; Z40=primary spherical
aberration; Z31, -1=primary coma aberration; Total HOA RMS=total corneal HOAs)