Clinical research of the corneal aberration and anterior segment parameters changes after pterygium surgery

Abstract

Objective To assess the changes in corneal higher order aberrations and changes in the elevation of the front and back corneal surfaces using the Sirius anterior segment analysis system. Methods From February 2017 to March 2018, 50 patients (63 eyes) with pterygium were studied in Taizhou E&ENT Hospital, Huaxia Eye Hospital Group. Among them, there were 29 males (38 eyes) and 21 females (25 eyes), with an average age of (53.32±9.14) years. All patients underwent pterygium excision combined with autologous conjunctival transplantation. The corneal astigmatism, corneal refractive power, asphericity value, corneal aberration (including total aberration, higher order aberration, coma, spherical aberration, clover aberration) and corneal anterior and posterior surface height were recorded by Sirius three-dimensional anterior segment analysis system before and 6 months after surgery, respectively. The data of the patients were expressed by mean standard deviation(±s). Before and after surgery were compared by paired t-test. Results The astigmatism of anterior and posterior corneal surfaces were (3.96±2.7) D and (0.40±0.15) D respectively. The astigmatism of anterior and posterior corneal surfaces were (1.45±1.1) D and (0.19±0.1) D respectively, 6 months after surgery. The astigmatism of anterior and posterior corneal surfaces was lower than that of preoperative corneal surfaces, and the difference was statistically significant (t=6.83, 9.25; P 0.05). The preoperative total aberration, higher order aberration, coma aberration and clover aberration were (6.29±3.18) microns, (2.4±1.18) microns, (0.006±0.46) microns and (-0.15±0.32) microns, respectively. The total aberration, higher order aberration, coma aberration and clover aberration were (4.13±2.28) microns, (1.24±0.57) microns, (-0.015±0.28) microns and (-0.07±0.61) microns respectively at 6 months after surgery. Except spherical aberration, the total corneal aberration, higher order aberration and coma aberration decreased 6 months after surgery, and the differences were statistically significant (t=5.96, 12.15, 2.02; P 0.05). The anterior and posterior corneal surface heights were (-3.52±25.92) microns and (3.42±56.05) microns in 4 mm area before surgery, respectively. The anterior and posterior corneal surface heights were (-3.46±10.37) microns and (-8.96±32.01) microns in 6 months after surgery. The differences of anterior and posterior corneal surface heights in 4 mm area between preoperatively and 6 months after surgery were not statistically significant (t=1.45, 1.72; P>0.05). The anterior and posterior corneal surface heights were (-44.84±46.59) microns and (-157.07±117.85) microns in the 8 mm area before surgery, respectively. The anterior and posterior corneal surface heights were (-68.14±25.14) microns and (-198.40±66.50) microns in the 6 months after surgery, respectively. The anterior and posterior corneal surface heights in the 8 mm area were higher than those before surgery. The difference was significant (t=6.38, 12.93; P<0.05). Conclusion Pterygium affects the corneal surface and induces heights changes and aberrations that is why it should be removed to improve the visual performance of the patients. We should consider pterygial excision before any refractive surgery or lens surgery planned for those patients. aberrations that is why it should be removed to improve the visual performance of the patients. We should consider pterygial excision before any refractive surgery or lens surgery planned for those patients. Key words: Pterygium; Aberration; Asphericity; Elevation; Sirius three-dimensional anterior segment analysis system