Abstract
We compared surgically induced astigmatism (SIA) by a superior incision with a temporal incision in manual small incision cataract surgery (MSICS), in patients with bilateral direct (regular) preoperative corneal astigmatisms. Patients and method: We carried out a prospective study from July 1st 2018 to September 30th 2019 in the department of ophthalmology at the University Hospital of Brazzaville. Keratometric readings were recorded before surgery to assess preoperative corneal astigmatisms. Keratometric evaluation was done 45 days post-operatively. Patients were followed 90 days after surgery in order to assess the healing of the surgical site. The surgically induced astigmatism (SIA) is the difference in the magnitude vectors between the preoperative and postoperative astigmatism. The result was positive if the postoperative astigmatism was greater than the preoperative astigmatism and negative if the postoperative astigmatism was less than the preoperative astigmatism. Results: Our study sample included 48 eyes from 24 patients, including 24 operated on temporal incision and 24 in superior incision. The average SIA for superior incisions was 0.33 ± 1.55 diopters (D), versus 0.33 ± 1.44 for temporal incisions. For superior incisions the SIA was 0.81 for astigmatisms lower than 2D, against 0.16D for the temporal incisions. On the other hand, for preoperative astigmatisms greater than 2D, the surgically induced astigmatism was ±0.62D, marking a decrease in preoperative astigmatism for the superior incisions against an increase of 0.5D for the temporal incisions. The healing was delayed for the temporal incisions responsible for discomfort persisting beyond 45 days. Conclusion: The temporal incision had better results than the superior incision for astigmatisms lower than 2D, and less good for astigmatisms higher than 2D. The temporal incision healed less well.
Highlights
Manual small incision cataract surgery (MSICS) is a surgical technique recommended for developing countries due to its lower technological requirement and these results close to those of phacoemulsification [1]
Keratometric readings were recorded before surgery to assess preoperative corneal astigmatisms
The result was positive if the postoperative astigmatism was greater than the preoperative astigmatism and negative if the postoperative astigmatism was less than the preoperative astigmatism
Summary
Manual small incision cataract surgery (MSICS) is a surgical technique recommended for developing countries due to its lower technological requirement and these results close to those of phacoemulsification [1]. Temporal incisions generate less SIA because of the distance of this site from the visual axis, and the eyelid blink tends to create a drag on the incision [4], and because of the predominance of reverse (irregular) astigmatisms in the elderly [6] most affected by cataracts. In these patients with reverse astigmatism, SIA is opposed to preexisting astigmatism with a tendency to reduce the latter [7]. For direct (regular) astigmatisms, it would rather be the upper incisions which would oppose preexisting astigmatism and are considered as generating the strongest SIA
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