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.