Clinical Evaluation of Intraocular Caliper-assisted Capsulotomy for Age-related Cataract

Comparison of Intraocular Caliper-assisted and Verion Navigation System-assisted Capsulotomy in Phacoemulsification Surgery: A Randomized Non-inferiority Trial

The purpose of this study is to compare the accuracy of capsulotomy assisted by intraocular caliper and Verion navigation system in phacoemulsification surgery and postoperative visual quality of patients.

Continuous curvilinear capsulorhexis (CCC) is an important and technically challenging procedure in cataract surgery. However, most surgeons perform CCC by experience or referring to the pupil size, which is highly subjective and the accuracy of capsulorhexis is unsatisfactory. The investigators developed a new modified intraocular caliper with standard calibration on the rinse needle, which can measure and locate the position of capsulorhexis. The surgeon can gently use the blunt needle in the front of the intraocular caliper to further make corresponding markers on the lens anterior capsule, and then carry out capsulotomy according to the marks. We found intraocular caliper-assisted capsulotomy can obviously improve the accuracy of capsulorhexis. The purpose of this study is to compare the accuracy and postoperative visual quality of intraocular caliper-assisted capsulotomy with those of digital image projection device VERION navigation system.

In intraocular caliper-assisted capsulotomy group, a modified intraocular caliper with standard calibration on the rinse needle was used to measure and locate the position of capsulorhexis with 5.3 mm diameter and the principle of pupillary margin in concentric circles. The surgeon could gently use the blunt needle in the front of the intraocular caliper to further make corresponding markers on the lens anterior capsule, and then carry out capsulotomy according to the marks.

In the Verion-assisted capsulotomy group, Verion navigation system was applied to project a 5.3 mm capsulorhexis centered on the corneal vertex. According to the projected capsulorhexis, capsulotomy was performed.

Verion Image Guided System (Alcon Laboratories, Inc.) is a digital image guidance system consisting of a diagnostic reference unit and a surgery pilot for intraoperative surgical assistance. The device can be used to align toric intraocular lens during surgery as well as support manual creation of a capsulorhexis with a predefined target diameter.

Images of the edges of IOL and capsulorhexis are taken at the end of the operation. Image J image analysis software is used to measure the horizontal diameter and vertical diameter of capsulorhexis with the diameter of IOL optical surface (6 mm) as the reference by two independently professional graders at the meantime, and further calculate the deviation of horizontal and vertical diameter of capsulorhexis from the target diameter (5.3 mm) .

Ideal capsulorhexis is defined as a centered and round capsulorhexis, which can cover the edge of IOL optical surface continuously for 360 degrees with a diameter between 5.0 to 5.5 mm.

The capsulorhexis-IOL overlap of each patient is graded as 360-degree continuous overlap, 270~360-degree overlap, 180~270-degree overlap, 90~180-degree overlap, and < 90-degree overlap.

Inclusion Criteria: Adults aged 55 to 80 years with age-related cataract; Pupil diameter ≥ 6.5mm after pupil dilation; Lens nuclear opacity grading score (LOCS III) lower than 4.0. Exclusion Criteria: Patients had previous intraocular surgery; Patients with a diagnosed eye disease that may affect the functions of lens suspensory ligament such as previous ocular trauma, lens subluxation, pseudoexfoliation syndrome, retinal pigment degeneration; Patients had other ocular diseases that impair visual function include optic neuropathy, uveitis, and tumor. Refused to participate the study.