Transcript Corneal Topographic and Astigmatic Changes After Pterygium

Evaluation of Corneal Changes
following Pterygium Surgery
Using Pentacam
Ahmad Kheirkhah MD, Hasan Hashemi MD
Rahman Nazari MD, Hamid Safi
Farabi Eye Hospital, Tehran, Iran
The authors have no financial interest in the subject
matter of this poster.
Introduction

Pterygium
◦ Definition: Encroachment of a fibrovascular tissue from
the bulbar conjunctiva onto the cornea.
◦ Causes regular or irregular astigmatism 1
◦ Produces significant alterations in corneal shape and
curvature

Pterygium surgery
◦ Improves the visual acuity
◦ Reduces the corneal astigmatism and irregularity
◦ Changes corneal topographic indices
Introduction

Corneal topographical changes with decreased corneal
astigmatism after pterygium surgery have been documented.
2,3

But,
◦ Few studies have calculated the surgically-induced
correction of the astigmatism. 4,5
◦ Corneal elevation changes after surgery has not been
studied yet.
◦ No study has used Pentacam (Oculus, Wetzlar, Germany)
for investigating the effects of pterygium and its excision on
cornea.

Purpose: To use Pentacam for evaluation of corneal changes
in patients undergoing pterygium surgery.
Materials & Methods

Study population: 80 eyes of 80 consecutive patients with
primary pterygium at Farabi Eye Hospital, Tehran, Iran from
August 2008 to January 2009.

Surgical technique: Excision of pterygium, mitomycin C
application, free conjunctival autograft or amniotic membrane
transplantation.

Pentacam examination was performed preoperatively and at
1, 3, and 6 months after surgery.

Measured corneal indices: mean keratometry, best fit sphere
(BFS) and central corneal elevation(CCE).
Materials & Methods

Surgically induced astigmatsm (SIA) was calculated from
the topographical keratometric and astigmatic values by
vectoral analysis using Holladay’s method.

Statistical analysis was performed by SPSS software and
statisical significance was tested using ANOVA and Paired
t-test.
RESULTS
Preop
SIA
1 month
3 months
6 months
3.72
3.60
3.57
Keratometry(front)
42.88 ± 1.91
44.30 ± 1.78
44.13 ± 1.72
44.02 ± 1.67
Keratomery (back)
-6.35 ± 0.33
-6.29 ± 0.28
-6.30 ± 0.27
-6.31 ± 0.29
BFS (front)
8.02 ± 0.32
7.76 ± 0.28
7.75 ± 0.48
7.77 ± 0.56
BFS (back)
6.44 ± 0.25
6.54 ± 0.25
6.54 ± 0.22
6.54 ± 0.26
CCE (front)
5.21 ± 4.55
4.70 ± 5.60
4.24 ± 4.04
4.93 ± 6.54
CCE (back)
4.66 ± 5.59
6.23 ± 4.63
5.24 ± 7.04
6.34 ± 5.72
Value are expressed as mean ± standard deviation
SIA: Surgically-induced astigmatism
BFS: Best fit sphere
CCE: Central corneal elevation
Results

SIA showed steepening of the cornea in the horizontal
meridian.

After surgery, the mean front keratometry increased
(P<0.001) while mean back keratometry decreased (P=0.11).

Decreases in front BFS and increases in back BFS were
statistically significant (P<0.001).

Decreases in front CCE and increase in back central
elevation were not statistically significant.
Discussion & Conclusion

Pterygium surgery improves pterygium-induced with the
rule astigmatism.

Cornea becomes steeper after surgery.

Pterygium surgery causes non-significant alteration in
central corneal elevation.

Further studies are needed to evaluate the factors
influencing surgically-induced astigmatism.
References

1. Oldenburg JB, Garbus J, McDonnell JM, McDonnell PJ.
Conjunctival pterygia. Mechanism of corneal topographic changes.
Cornea. 1990 Jul;9(3):200-4.

2. Bahar I, Loya N, Weinberger D, Avisar R. Effect of pterygium
surgery on corneal topography: a prospective study. Cornea. 2004
Mar;23(2):113-7.

3. Wu PL, Kuo CN, Hsu HL, Lai CH. Effect of pterygium surgery on
refractive spherocylinder power and corneal topography. Ophthalmic
Surg Lasers Imaging. 2009;40(1):32-7.

4. Ozdemir M, Cinal A..Early and late effects of pterygium surgery on
corneal topography. Ophthalmic Surg Lasers Imaging.
2005;36(6):451-6.

5. Fong KS, Balakrishnan V, Chee SP, Tan DT. Refractive change
following pterygium surgery. CLAO J. 1998 Apr;24(2):115-7.