The effect of tunnel length and position on postoperative corneal astigmatism: An optical coherence tomographic study

Abstract

Purpose: The purpose of this study is to evaluate the effects of variation in tunnel length of same-sized clear corneal phacoemulsification incisions on the generation of surgically induced astigmatism and corneal astigmatism. Methods: A total of 126 cataract patients treated in four study groups based on location and tunnel length of the clear corneal incisions (superior long, superior short, temporal long, temporal short) were reviewed. In the short tunnel groups, a 2.8 mm keratome was used with a motion parallel to the iris surface, while in the long tunnel groups, the same keratome was advanced in the corneal stroma until the mark on the keratome was reached. The surgically induced astigmatism and the corneal astigmatism were measured with corneal topography. The tunnel lengths were determined by anterior segment optical coherence tomography. Results: The tunnel lengths of the long tunnel groups were significantly longer than the short tunnel groups. The total and anterior corneal surgically induced astigmatism of the superior long group was significantly higher than the other groups. Posterior corneal surgically induced astigmatism was similar. The postoperative total and anterior corneal astigmatism values of the superior long group was significantly higher than the other groups. No difference was observed for mean change in corneal astigmatism between the groups. Conclusion: The tunnel length of a clear corneal incision is a significant determinant of surgically induced astigmatism for superior placed corneal incisions. Therefore, for superiorly positioned clear corneal incision, the incision should be rectangular with a shorter tunnel to keep the surgically induced astigmatism to a minimum. For squarer-shaped clear corneal incision, limbal-temporal incisions may be performed for astigmatic neutrality.

Effect of corneal incision features on anterior and posterior corneal astigmatism and higher‐order aberrations after cataract surgery

“…Choi et al's work standardized the CCI deformities by wound deformity scoring and found positive correlations between SIA and wound instability (Choi et al 2016). Our results were in agreement with the previous studies (Wilczynski et al 2016;Sonmez & Karaca 2020;Hayashi et al 2018b), and we further evaluated the correlation between the CCI features and corneal SIA on the anterior and posterior surfaces at 1 and 6 months postoperatively.…”

Enlargement of main corneal incision: clinical intraindividual comparison of two preloaded intraocular lens injectors

“… 22 , 23 Sonmez et al examined the additional effect of tunnel length on different incision sites and found that a shorter tunnel may be beneficial for a superior CCI to limit the SIA. 24 Apart from that, wound stretching was suggested to be a contributing factor. 12 Vasavada et al compared corneal incision enlargement and SIA using CCIs of 1.8 mm and 2.2 mm.…”

Corneal Biomechanics and Other Factors Associated with Postoperative Astigmatism after Cataract Surgery

“…Regarding the position of the incision, there are corneal, limbal, scleral, and corneoscleral incisions. The most frequently used approach in modern cataract surgery is a corneal incision, and the postoperative astigmatism is smaller with increasing distance from the cornea [ 3 , 4 ]. Most studies suggest that the temporal position of the incision results in smaller surgically induced astigmatism if there is mild preoperative astigmatism and against-the-rule astigmatism [ 5 , 6 , 7 ].…”