The Effect of Corneal Anterior Surface Eccentricity on Astigmatism after
Cataract Surgery
Choul Yong Park MD1
Sung Jun Lee MD1
Prabjot Channa MD2
Roy S. Chuck MD, PhD2
1. Department of Ophthalmology, Dongguk University, Ilsan Hospital
2. Department of Ophthalmology, Montefiore Medical Center, Albert Einstein College of Medicine
The authors have no financial interest in the subject matter of this poster
Purpose
• In the pursuit of better control of SIA, in this
study, we investigated the relationship between
SIA and anterior corneal eccentricity after
routine cataract surgery.
Materials and Methods
• 125 Asian eyes• Phacoemulsification with 2.8mm clear corneal incision• Check preop keratometry (Full Auto Ref-Keratometer RK-F1,
Canon, Japan) and preop Scheimpflug corneal image (Pentacam, Oculus, Germany)
• Eccentricity of anterior corneal surface : Pentacam analysis within 8 mm diameter centered at the visual axis
• Check postop keratometry (Full Auto Ref-Keratometer RK-F1, Canon, Japan )
• Calculate surgically induced astigmatism (SIA) using vector calculation formula
• Statistics– ANOVA and multiple linear regression analysis
Materials and Methods
• Exclusion criteria– irregular preoperative astigmatism – any defect in the posterior capsule or zonules – post-operative best spectacle corrected visual acuity (BSCVA) less than 20/20 – glaucomatous ocular change, – severe keratoconjunctivitis sicca, – significant corneal pathology and opacity
• The eyes were grouped according to the amount of SIA. – group 1: the eyes with SIA from zero to 0.25 D, – group 2: the eyes with SIA from 0.26D to 0.5D, – group 3: the eyes with SIA from 0.51D to 0.75D, – group 4: the eyes with SIA from 0.76D to 1.0D, – group 5: the eyes with SIA greater than 1.0D.
• The characteristics of each group were analyzed and compared.
Results 1
Eyes included(N=125)
Mean ±SD max min
Age 69.5± 8.4 91 50
Preop corneal cylinder 0.93 ± 0.53 2.50 0
Eccentricity 0.28 ± 0.28 0.79 -0.82
Central corneal thickenss 534.2±30.6 611 445
Axial length 23.47±1.01 29.39 21.35
Postop refractive sphere 0.20±0.70 1.75 -3.25
Postop refractive cylinder -0.85±0.55 2.75 0
Postop spherical equivalent -0.23±0.69 1.13 -3.38
SIA (magnitude) 0.67±0.45 2.10 0
Postop UCVA (Snellen acuity) 0.72±0.20 1.25 0.125
Table 1. Descriptive data of study eyes UCVA: post-operative uncorrected distance visual acuity, preop: pre-operative, postop: post-operative, SE: spherical equivalent, max: maximum, min: minimum
Results 2
Location of Main
Incision
Superior(min/max)
Superior-Nasal(min/max)
Superior-Temporal(min/max)
Temporal(min/max)
Nasal(min/max)
p-value
Number of eyes 63 15 11 23 13
age66.8±8.3(50/86)
75.7±6.4(67/91)
71.3±9.4(52/86)
70.6±8.0(50/85)
71.7±6.2(64/83)
0.002
Sex (M/F) 24/39 2/13 4/7 5/18 4/9
Preop corneal cylinder1.03±0.58(0.25/2.5)
0.75±0.48(0.25/1.75)
0.62±0.33(0.25/1.25)
0.93±0.48(0/2.0)
0.94±0.41(0.25/1.5)
0.135
Preop corneal cylinder
axis112.0±70.7 72.8±35.1 41.4±25.9 89.0±29.9 21.6±11.6 0.135
Eccentricity0.32±0.29
(-0.82/0.79)0.25±0.22
(-0.28/0.65)0.39±0.23(0.05/0.73)
0.26±0.29(-0.36/0.68)
0.12±0.30(-0.31/0.79)
0.114
Central corneal
thickenss
533.7±30.5(445/609)
529.1±34.1(470/606)
548.0±32.2(489/598)
530.8±29.2(473/594)
538.5±29.3(501/611)
0.564
Axial length23.4±1.17
(21.35/29.39)23.4±0.70
(22.45/24.99)23.4±0.81
(22.44/24.60)23.7±0.90
(22.38/25.50)23.6±0.87
(22.50/25.80)0.759
Postop refractive
sphere
0.19±0.52(-1.5/1.25)
0.15±0.41(-0.5/0.75)
-0.05±1.23(-3.25/0.75)
0.21±0.87(-2.25/1.25)
0.42±0.87(-1.75/1.75)
0.619
Postop refractive
cylinder
0.82±0.59(0/2.75)
0.85±0.58(0/2.00)
0.58±0.37(0/1.25)
1.00±0.45(0/1.50)
1.00±0.54(0.25/2.25)
0.262
Postop spherical equivalent
-0.22±0.54(-1.50/0.88)
-0.28±0.40(-1.25/0.13)
-0.34±1.17(-3.38/0.75)
-0.29±0.82(-3.00/0.88)
-0.08±1.00(-2.88/1.13)
0.982
SIA 0.82±0.49 0.50±0.38 0.63±0.40 0.45±0.24 0.55±0.47 0.004
Table 2.The comparison among different location of main incision. SIA: surgically induced astigmatism, preop: pre-operative, postop: post-operative, max: maximum, min: minimum, P-value calculated using ANOVA test
Results 3
groupsGroup 1
(min/max)Group 2
(min/max)Group 3
(min/max) Group 4 (min/max)
Group 5 (min/max)
p-value
Number of eyes 19 39 22 22 23
SIA 0.14±0.09 0.36±0.08 0.63±0.07 0.92±0.09 1.43±0.27
age68.2±11.1
(50/91)71.0±7.6(52/86)
72.0±6.8(62/87)
67.3±9.0(50/84)
67.8±7.2(51/84)
0.187
Sex (M/F) 24/39 2/13 4/7 5/18 4/9
Preop corneal cylinder0.741.03±0.58
(0.25/2.5)0.75±0.48(0.25/1.75)
0.62±0.33(0.25/1.25)
0.93±0.48(0/2.0)
0.94±0.41(0.25/1.5)
0.135
Preop corneal cylinder
axis112.0±70.7 72.8±35.1 41.4±25.9 89.0±29.9 21.6±11.6 0.001
Eccentricity0.18±0.29
(-0.22/0.79)0.20±0.31
(-0.28/0.65)0.34±0.25
(-0.11/0.70)0.34±0.28
(-0.36/0.79)0.44±0.18(0.25/0.76)
0.006
Central corneal
thickenss
533.7±30.5(445/609)
529.1±34.1(470/606)
548.0±32.2(489/598)
530.8±29.2(473/594)
538.5±29.3(501/611)
0.564
Axial length23.4±1.17
(21.35/29.39)23.4±0.70
(22.45/24.99)23.4±0.81
(22.44/24.60)23.7±0.90
(22.38/25.50)23.6±0.87
(22.50/25.80)0.759
Postop refractive
sphere
0.19±0.52(-1.5/1.25)
0.15±0.41(-0.5/0.75)
-0.05±1.23(-3.25/0.75)
0.21±0.87(-2.25/1.25)
0.42±0.87(-1.75/1.75)
0.619
Postop refractive
cylinder
0.82±0.59(0/2.75)
0.85±0.58(0/2.00)
0.58±0.37(0/1.25)
1.00±0.45(0/1.50)
1.00±0.54(0.25/2.25)
0.262
Postop spherical equivalent
-0.22±0.54(-1.50/0.88)
-0.28±0.40(-1.25/0.13)
-0.34±1.17(-3.38/0.75)
-0.29±0.82(-3.00/0.88)
-0.08±1.00(-2.88/1.13)
0.982
Table 3. The comparison among different groups divided by the amount of SIA SIA: surgically induced astigmatism, preop: pre-operative, postop: post-operative, max: maximum, min: minimum, P-value calculated using ANOVA test
Results 4
The correlation between the age and eccentricity in all study eyes (125 eyes)The eccentricity of the anterior cornea showed significant negative correlation with the age of the eyes. p=0.008 (Pearson’s rho=-0.236)
The correlation between SIA and eccentricity in all study eyes (125 eyes)This scatter plot shows the significant positive correlation between SIA and eccentricity. (p<0.001, Pearson’s rho=0.310) Each cross represents each case. SIA: surgically induced astigmatism
Results 5
The comparison of anterior corneal eccentricity between groups divided by the amount of SIAGroups 1 and 2 showed significantly lower eccentricity when compared to group 5. (group 1 vs group 5:p=0.025, group 2 vs group 5:p=0.012) The number inside each column shows the mean value of eccentricity. ANOVA test was used.
The correlation between SIA and preoperative amount of corneal astigmatism (diopters)SIA showed significant positive correlation with preoperative amount of corneal astigmatism (preop cylinder). (p<0.001, Pearson’s rho =0.346)
Results 6
The comparison of SIA between eyes with different locations of the main incisionsSuperior incision induced the greatest SIA compared to temporal incision. (p=0.007) The other incision locations (SN, ST, T and N) showed no significant difference in SIA. The number inside each column shows the mean value of SIA. S:superior, SN: superior-nasal, ST: superior-temporal, T: temporal, N: nasal, ANOVA test was used.
The correlation between SIA and the eccentricity of anterior corneal surface in eyes with superior location of the main incision.This scatter plot shows significantly positive correlation between SIA and eccentricity. (p=0.028, Pearson’s rho =0.276) Each cross represents each case. SIA: surgically induced astigmatism
Conclusion
• In this study, we found the SIA is affected by several factors in modern cataract surgery.
• We found that superior location of the main incision induced the greatest SIA compared to other locations.
• We also found that corneas with high amounts of preoperative astigmatism resulted in greater SIAs compared to corneas with low amounts.
• Interestingly, we also found that corneas with higher amounts of anterior eccentricity resulted in greater SIAs.
• These findings lead us to conclude that corneas having both low preoperative astigmatism and low anterior eccentricity (more close to sphere or oblate ellipse shape) may result in relatively the least SIA after cataract surgery.