Tecnis Toric II IOL shows good rotational stability and uncorrected distance visual acuity: Study
Many patients with cataract have levels of corneal or refractive astigmatism sufficient to impact clinical outcomes after cataract surgery. Astigmatism management at the time of cataract surgery results in better postoperative visual outcomes, higher satisfaction with vision, greater spectacle independence, and improvement in patients' vision-related quality of life compared to patients in whom astigmatism management is not attempted during cataract surgery. Moreover, astigmatism management during cataract surgery is a cost-effective approach compared to postoperative vision correction with spectacles.
The surgical management of astigmatism requires the integration of multiple steps throughout the preoperative period to achieve an optimal outcome. The toric intraocular lens (IOL) power must be properly calculated and selected. Toric IOL stability has been implicated as a potential source of postoperative rotational malposition.
The Tecnis Toric II (Model ZCU) IOL is an ultraviolet light-absorbing posterior chamber lens designed to compensate for the spherical aberration of the average cornea and correct astigmatism. The IOL incorporates a proprietary wavefront-designed toric aspheric optic with a square posterior optic edge that provides a 360⁰ barrier to reduce cell migration across the posterior capsule. The edge of the optic is frosted to reduce potential edge glare effects.
A post-market study was conducted by Chang et al to determine the rotational stability of these frosted haptic IOLs. Short-term rotational stability, defined as 1-day and 1-week postoperatively, and clinical performance of the Tecnis Toric II (Model ZCU) IOL from this were described in a previous publication. In this study, short- and long-term lens rotation, visual acuity, manifest refraction, and patient and surgeon satisfaction were evaluated over a 3-month period following implantation.
A post-market, prospective, multi-center, single-arm, open-label study conducted at seven clinical sites in the United States. Two hundred and two eyes of 133 subjects with unilateral or bilateral cataracts and corneal astigmatism were implanted with the Tecnis Toric II IOL, Models ZCU150 to 600. Lens axis misalignment/ rotation, visual acuity, manifest refraction, and surgeon and patient satisfaction were evaluated 3 months postoperatively. Lens rotation was determined with operative and postoperative visit photographs and was analyzed by two independent masked analysts.
Mean absolute lens rotation was 0.82° ± 1.00° and 0.94° ± 0.71° at 1 day (n = 189 eyes) and 3 months (n = 185 eyes), respectively. Absolute lens rotation was ≤5° in 98.9% and 100% of eyes at 1 day and 3 months, respectively.
At 3 months, postoperative monocular uncorrected and corrected distance visual acuities were 0.004 ± 0.115 LogMAR (20/20) and −0.066 ± 0.092 LogMAR (20/17), mean spherical equivalent was −0.25 D ± 0.35 D and residual refractive cylinder was +0.27 D ± 0.33 D. Surgeons were satisfied/very satisfied with overall clinical outcomes and rotational stability in 99% of eyes, and with uncorrected distance vision in 98.5% of eyes.
Rotational stability of toric IOLs following implantation is critical to good visual outcomes, particularly with higher magnitude of astigmatism. For each 10° of toric IOL rotation, the residual cylinder is equal to about one-third of the corneal cylinder, creating an under correction of the astigmatic refractive error. Most modern toric IOLs show a relatively low amount of misalignment. The original Tecnis toric IOLs (model ZCT) was the first to meet the ANSI standard for rotational stability for toric IOLs (>90% of eyes having ≤5° axis change between consecutive visits three months apart), with ≥93% of toric first eyes having a ≤ 5°axis change. However, 3–5° of rotation still amounts to a loss of approximately 10–15% of the astigmatism-reducing effect of a toric IOL, with amounts obviously higher for the outlying values of lens rotation.
The novel validated photographic technique for assessing lens position provides evidence that this new toric IOL design with frosted haptics can help to increase surgical success, patient satisfaction, and surgeon confidence in a toric IOL approach for cataract patients with astigmatism. This study, while not a head to head comparison to other toric options, provides confirmation that this improved lens design yields robust technical and clinical outcomes that address past reports of rotational instability with the original Tecnis Toric IOL. This improved toric design is now incorporated into other IOL designs giving physicians presbyopia-correcting options for their patients with clinically significant levels of astigmatism. The ongoing improvements and continued success of toric IOLs is critical to meeting the needs of a greater proportion of the growing presbyopic population in the US and abroad.
Source: Chang et al; Clinical Ophthalmology 2022:16 https://doi.org/10.2147/OPTH.S389304
