A comparison of three different corneal marking methods used to determine cyclotorsion in the horizontal meridian

Abstract

During toric intraocular lens (IOL) implantation, surgeons must take particular care to ensure that inaccurate preoperative measurement and intraoperative misalignment do not cause unexpected postoperative residual astigmatism. This retrospective, comparative case series study aimed to analyze the rotational deviation, or cyclotorsion, of three corneal marking methods: VERION digital marker (VDM; reference), horizontal slit beam marking (HSBM), and subjective direct visual marking (SDVM) on the table (using a bevel knife tip). Subjects included 81 eyes of 61 patients (mean age: 65.70±13.14 years; range: 32–91 years) undergoing scheduled cataract surgery. A preoperative reference image was taken of each eye. Subsequently, a slit lamp with the light beam turned to the horizontal meridian was used to align the seated patient’s head, and two reference marks were placed at the 3- and 9-o’clock positions of the corneal limbus using a 27-gauge needle and marking pen (HSBM). Upon transfer to the surgical table, the VDM was used to display a real-time dial scale on the patient’s eye, with the entrance of the temporal clear corneal incision (CCI) at 0° (horizontal meridian). Simultaneously, a bevel knife tip was used to create a marker based on the surgeon’s visual determination of the temporal 0° point (SDVM). We used the VDM to quantitatively evaluate the accuracy of axis alignment via deviation from the horizontal reference meridian. Compared with the reference meridian, the SDVM (−3.46°±7.32°, range: −18° to 13°) exhibited greater average relative cyclotorsion versus the HSBM (0.41°±4.92°, range: −10° to 10°). Furthermore, the mean average misalignment was significantly less in the HSBM group versus the SDVM group (t=4.179, P<0.001). The VDM is likely a reliable marking method, similar to the HSBM. In contrast, the SDVM is not entirely reliable. The VDM usage may prevent inaccurate preoperative manual marking during toric IOL implantation.

Do limbal relaxing incisions during cataract surgery still have a role?

“…All procedures were performed by the same experienced surgeon using standard phacoemulsification under topical anesthesia. All patients had immediate pre-operative limbal-corneal marking while sitting upright and looking straight ahead using the slit lamp to avoid any cyclotorsion of the eyeball which could be induced by lying supine as per previously published technique [ 10 ]. All patients were fully consented and informed about the expectations along with potential complications.…”

Intraoperative capsular marking for toric intraocular lens placement

“…Cyclotorsion of the eye from the upright to supine position is approximately 2°–4° on an average but can be up to 15° in individual patients. [ 9 ]…”

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“…The slit lamp is turned to the horizontal position with the light centered on the apex of the cornea. Subsequently, the horizontal meridian is marked by scratching the cornea with a 27-gauge needle and a marking pen under topical anesthesia, as described in our previous study 9. The final step is the intraoperative alignment of secondary modalities with reference markers.…”

“…Deviation from target axis in toric IOLs implantation can be significantly decreased with Callisto Eye (Carl Zeiss Meditec AG, Jena, Germany) image-guided system (3.6°±2.6°) compared to that with manual marking (5.5°±3.3°) 8. Our previously published data also demonstrated that horizontal slit beam marking resulted in a misalignment of 3.66° compared with the Verion (Alcon Laboratories, Inc., Fort Worth, TX, USA) digital marking technique 9. Intraoperative imaging using the Verion image-guided system matched the preoperative image displaying the scleral vessels, limbal vessels, and iris morphology of the eyes, known as iris fingerprint registration 10.…”