الفهرس 
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Abstract
Pterygia are elevated superficial external ocular lesions that usually developed from the perilimbal conjunctiva and extend over the cornea. they are varying in size and could be atrophic, fleshy, quiescent or progressive leading to changes in the topography of the cornea. pterygium may occur in the nasal and/or temporal sides of the cornea. in advanced cases, they may obscure the corneal center leading to severe affection of vision. Regardless of the many techniques that used in excision of pterygium, resection is the first step in repair.
This study was carried out during the period from June 2021 to June 2022. All surgeries were performed by one surgeon in Suhag University Hospital.
The aim of this prospective comparative case series study is to assess the corneal topographic changes before and after excision of primary pterygium and to evaluate the colleration between the size of pterygium and these changes which obtained by Pentacam. The following measurements were obtained from central 3 mm optical zone of 3 composite refractive maps (anterior sagittal curvature map, anterior elevation map and corneal thickness map): K1, K2, astigmatism, axis, value of elevation of anterior corneal surface in comparison with BFS and finally apical corneal thickness. Additionally, we studied the changes in VA, BCVA as well as refractive sphere and cylinder.
Thirty-eight eyes of thirty-eight patients with primary pterygium fulfilling the inclusion criteria were included in this study. The patients were divided into 2 groups according to pterygium size that was graded according to the advancing edge position from the limbus: group 1: equal or less than 3 mm from limbus. group 2: more than 3 mm from limbus. And that was done just before surgery under operating microscope using Castroviejo caliper.
We used the same technique for management of pterygium in all cases which include surgical excision of pterygium with bare sclera technique and intraoperative application of MMC. All patients underwent follow up for 6 months after surgery.
In our study, the mean preoperative astigmatism significally decreased after surgery during the whole postoperative follow up visits (p<0.05). Additionally, the mean value of astigmatism was higher in large sized pterygium group than small sized one not only preoperatively but also through the three postoperative follow up visits (p<0.05). On the other hand, the mean preoperative K1 (flattest meridian) increased significally after surgery during the whole postoperative follow up visits (p<0.05). Preoperatively, large sized pterygium group has significally lower K1 mean values than small sized one. mean values of K2 (steepest meridian) did not change significally at three and six months after surgery. Also, there was no significant difference in mean value of K2 between the two groups neither preoperatively nor at one month postoperatively but at three and six months after surgery, the mean value of K2 was significally higher in large sized pterygium group(p<0.05).
In this study, there was a decrease in mean value of central 3 mm anterior elevation map after surgery but that decrease was clinically significant only at three and six months postoperatively. also, there was no significant difference(p>0.05) in mean values of anterior elevation map preoperatively between the two groups, but after surgery, small sized group has significant lower mean value of anterior elevation map than large sized group.
Mean value of apical corneal thickness significally (p<0.05) decreased after surgery but there was no significant difference between two groups neither preoperatively nor after surgery.
In the current study, the mean values of UCVA and BCVA were statistically better during the three visits postoperatively. Additionally, the mean values of both were better in small sized pterygium group than the large sized one.
The mean value of refractive sphere significally decrease after surgery but there was no significant difference in mean values of refractive sphere between the two groups preoperatively and after surgery. On the other hand, the mean value of refractive cylinder decreased significally (p<0.05) after surgery. Additionally, the mean values of refractive cylinder was higher in large sized group preoperatively and during the three visits of postoperative follow up.
Conclusion:
Pterygia lead to deterioration of visual acuity by causing refractive and topographic changes. Excision of pterygium leads to changes in astigmatism, keratometric power, apical corneal thickness as well as values of anterior elevation map.
Refractive and topographic values vary with pterygium size. Furthermore, topographic and refractive results after excision of pterygium are better in small sized pterygia than that of large sized ones.