Astigmatism Management With Iris-registration Guided Corneal Relaxing Incisions or Toric IOLs During Cataract Surgery

Most of the patients presenting for cataract surgery also have pre-existing corneal astigmatism which if left uncorrected can adversely affect visual and refractive outcomes after cataract surgery. Pre-existing astigmatism at the time of cataract surgery can be corrected by either corneal relaxing incisions or implantation of toric IOLs. While the safety and efficacy of these procedures are well established, there are various challenges associated with these techniques that surgeons need to overcome to achieve good outcomes postoperatively.

The use of iris registration technology that automatically compensates for cyclotorsion has the potential to improve the alignment accuracy of CRI or toric IOLs. The Cassini Ambient and Catalys Femtosecond Laser incorporate this technology to help cataract surgeons accurately align toric IOLs on the intended axis of implantation or accurately place CRI on the intended meridian. The present study is aimed at evaluating the efficacy of astigmatism correction during femtosecond laser-assisted cataract surgery with Catalys femtosecond laser. The patients will either undergo iris registration guided CRIs or iris registration guided alignment of toric IOLs.

Surgical correction of astigmatism using corneal relaxing incisions or toric IOLs have been widely adopted to correct pre-existing astigmatism in cataract surgery patients. While the safety and efficacy of these procedures are well established, there are various challenges associated with these techniques that surgeons need to overcome to achieve good outcomes postoperatively; for instance, correction of astigmatism either with corneal relaxing incisions (CRIs) or toric IOLs during cataract surgery requires appropriate pre-operative planning based on corneal curvature measurements, biometry, nomogram/IOL selection, accurate marking for the placement of CRI/implantation of toric IOL on the intended axis, intraoperative alignment, cyclotorsion compensation, and postoperative IOL rotation, etc.

The Cassini Ambient and Catalys Femtosecond Laser incorporate this technology to help cataract surgeons accurately align toric IOLs on the intended axis of implantation or accurately place CRI on the intended meridian. This is expected to improve patients' visual functioning and reduce spectacle dependence postoperatively. The Cassini Ambient provides the preoperative anterior and posterior astigmatism with iris registration. The new Catalys Precision Laser System (Johnson \& Johnson Vision) with cOS 6.0 software facilitates direct importation of preoperative data from the Cassini via a wireless connection or USB drive, eliminates the need for manual axis marking as it compares the pre- and intra-operative iris anatomy data and compensates for tilt and rotation so that the laser marks are perfectly aligned to the steep meridian and the target axis. Linking preoperative diagnostic information to the laser minimizes data entry and transcription errors. It also eliminates several steps in the planning process for toric IOLs and CRI, thus improving the overall accuracy of the astigmatism correction procedure and reducing chances for error.

Eligibility Criteria:
Inclusion Criteria:

* Patients desirous of undergoing cataract surgery.
* Pre-existing corneal astigmatism requiring either CRIs or toric IOL implantation.
* Patients in whom iris registration link between Cassini Ambient and Catalys femtosecond laser is successful.

Exclusion Criteria:

Patients will be excluded from participating in the study due to any of the following reasons:

* Insufficient pupil dilation to complete Catalys treatment
* Clinically significant corneal pathology precluding reliable Cassini topographical measurement of any cause
* Preoperative corneal astigmatism greater than 4.00 D, or astigmatism requiring both CRIs and implantation of toric intraocular lens for correction.
* Cassini topographical measurement deemed inconsistent with historical topographies and refractive error based on clinical judgment
* Visually significant ocular surface disease (OSD) precluding reliable measurements and/or anticipated to affect refractive stability
* Lid position abnormalities that may affect vision
* Moderate or severe stage glaucoma or optic nerve disease, that would interfere with assessment of or achievement of optimal BCVA
* Visually significant macular disease