Evaluation of Corneal Changes Evaluation of Corneal Changes following Pterygium Surgery following Pterygium Surgery

Using PentacamUsing 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.

IntroductionIntroductionPterygium

◦ 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

IntroductionIntroduction 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 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 & MethodsMaterials & 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

Value are expressed as mean ± standard deviation

SIA: Surgically-induced astigmatismBFS: Best fit sphereCCE: Central corneal elevation

Preop 1 month 3 months 6 months

SIA 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

ResultsResults 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 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.

ReferencesReferences 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.