Cataract Surgery With Adapted Clear Corneal Incisions Can Reduce Corneal Astigmatism – A Retrospective Comparative Cohort Study

Spectacle dependency due to corneal astigmatism may affect patient satisfaction after micro-incision cataract surgery (MICS) with implantation of an aspherical, monofocal intraocular lens (IOL). We used a simple algorithm for main incision adaptions regarding location, width, and use of an opposite clear corneal incision (OCCI) based on preoperative corneal keratometric data. The purpose of this study was to explore to what extent these adaptions can reduce corneal cylinder of 1 diopter (D) or more.

All included cataract surgeries took place at Department of Ophthalmology, Linköping University Hospital, Sweden, and were performed with equipment compatible with MICS (incision size 2.0 mm or less) .

In this study of 170 eyes that underwent MICS, all enrolled eyes had corneal astigmatism > 1.0 D cylinder power before surgery. In 83 eyes, a simple algorithm depending on corneal cylinder power and axis was applied for adaptations of clear corneal incisions. 87 eyes were included as controls and underwent MICS with a standardized 2.0 mm main incision at axis 170°. For all included eyes, data on refractive cylinder power (RCP) before and after surgery was collected, as well as data on corneal keratometric cylinder power (KCP) before surgery. Postoperative KCP data was available for 57 eyes with adapted incisions and 53 controls. The intra-individual differences in KCP and RCP before and after surgery were compared between groups.

With adapted incisions mean KCP decrease was 0.64 D (range -2,5 to +1,25), while for control eyes KCP decreased 0.02 D on average (range -1,25 to +1,25) (p < 0.001 t-test). KCP decreased in 43 eyes (75%), was unchanged in 5 eyes (9%) and increased in 9 eyes (16%) with adapted incisions. For controls, corresponding figures were 19 (36%), 14 (26%) and 20 (38%) respectively (p = 0.007 Chi2).

RCP mean decrease with adapted incisions was 0.62 D (range -3.5 to +1.5), while RCP increased 0.19 D for controls on average (range -3 to +4) (p < 0.001 t-test). With adapted incisions RCP improved in 71% of cases, was unchanged in 12% and increased in 17%, while equivalent rates for controls were 38%, 13% and 49% (p = 0.001 Chi2).

After MICS with a monofocal, non-toric IOL, postoperative corneal astigmatism can be significantly decreased with clear corneal incisions, adapted according to a simple algorithm based on preoperative cylinder power and axis.

In future studies, long-term outcomes in refraction and corneal structure are of interest.  We also plan to study whether this decrease in cylinder power on subjective refraction and on keratometry may decrease patients’ need for astigmatic spectacle correction after cataract surgery.