Cataract surgery is one of the commonest procedures in the world. As technology improves, better refractive outcomes can be achieved, and more patients are seeking greater spectacle independence. The latter is often achieved using multifocal intraocular lenses (IOLs). Multifocal IOLs achieve their effects by either refractive optics or diffraction. Diffractive multifocal IOLs have a series of centered concentric rings on the front or back surface of the optic. The AT Lisa tri IOL (Carl Zeiss Meditech AG) is a hydrophilic plate diffractive multifocal lens with the rings on the anterior surface.
There are a large number of lens manufacturers and lens types with differing production methods. Manufacturing defects have been reported in the past involving both the haptics and optics.1–3 Optic opacities have been noted to be present at the time of surgery, or developing later.2,3 We report a case of a defective Zeiss multifocal IOL being inserted and subsequently exchanged.
Patient Consent Statement
The patient gave verbal consent for use of her data in this case report.
A 58-year-old woman was referred for cataract surgery. She had a low hyperopia, and the rest of history and examination was unremarkable. Seeking spectacle independence after cataract surgery, it was decided to use a toric multifocal IOL.
Right eye surgery was initially without complications, and the IOL was implanted into the capsular bag. However, prior to aspiration of the ophthalmic viscosurgical device ,it was noted that the diffractive rings were off-center and out of alignment with the toric markings (Figure 1). The IOL was not tilted, so it was assumed that there was a manufacturing defect. Ophthalmic viscosurgical device was injected to prolapse the IOL out of the capsular bag. A replacement IOL was injected into the bag beneath the defective IOL. The defective IOL was then cut into 4 pieces using IOL-holding forceps and IOL-cutting scissors (MicroSurgical Technology), and the fragments were explanted.
The postoperative period was unremarkable, and the left eye underwent insertion of a toric trifocal IOL 1 week later. At the 1-month postoperative visit, the uncorrected distance visual acuity in the right eye was 6/7.5 + 2 correcting to 6/6 with a low myopic correction.
The IOL fragments were put into a container of balanced salt solution and given to a company representative with a request for an explanation. Four months later, no further communication from the company had been received.
To the authors’ knowledge, this is the first report of a manufacturing defect in the multifocal component of an IOL. There are few reports of IOL manufacturing defects in the literature. Most describe either glistenings or calcification, which develop postoperatively.
Ideally, the surgeon would check for IOL defects under the operating microscope prior to insertion into the eye. However, this may have an undesirable effect on workflow. Moreover, many IOLs, including multifocal ones, now come in a preloaded format, making a preimplantation check impossible.
Therefore, it is important that surgeons are familiar with explantation techniques and have dedicated instruments to facilitate removal on hand at all practice locations. Ideally, explantation of the lens needs to occur without wound enlargement as one would expect that any induced cylinder from wound enlargement would be poorly tolerated by a patient seeking a good refractive outcome. This case also underlies the need for keeping a backup IOL on hand.
The 2 main types of manufacturing of IOLs are injection molding or lathe cutting of a blank.4 We assume the Zeiss hydrophilic range is lathe cut. This would presumably mean that in this case, both the optic and the diffractive rings were decentered. This raises the serious concern that the same defective process could occur with manufacture of a nonmultifocal IOL. For example, the Zeiss Torbi or Asphina range, which could result in an off-center optic that would go completely undetected by the clinician but result in a significant drop in visual quality for the patient.
Surgeons need to remain vigilant that IOL manufacturing defects can occur. If defects do occur, surgeons need to pressure industry both to address these instances and to disseminate this information to other surgeons and the regulatory authorities. Returning defective fragments to the manufacturer may not achieve this, so we would encourage surgeons to retain explanted fragments for further examination and proper documentation of the defects.
WHAT WAS KNOWN
- Manufacturing defects of IOLs can occur.
WHAT THIS PAPER ADDS
- This is the first report, to the authors’ knowledge, of a decentration defect of the diffractive rings of a multifocal IOL.
- Surgeons need to be aware that this possible complication exists and be prepared to explant.
- This finding raises the possibility of manufacturing defects occurring in centration of monofocal IOLs that would not be obvious to the surgeon but could cause visual degradation.
1. Oner FH, Durak I. Intraocular lens with short haptics: a manufacturing defect. J Cataract Refract Surg 2002;28:918–919
2. Sammouh FK, Baban TA, Warrak EL. Defective toric intraocular lenses with no subsequent effects on visual outcomes. JCRS Online Case Rep 2018. doi: 10.1016/j.jcro.2018.05.001
3. Bompastor-Ramos P, Póvoa J, Lobo C, Rodriguez AE, Alió JL, Werner L, Murta JN. Late postoperative opacification of a hydrophilic-hydrophobic acrylic intraocular lens. J Cataract Refract Surg 2016;42:1324–1331
4. Yu N, Fang F, Wu B, Zeng L, Cheng Y. State of the art of intraocular lens manufacturing. Int J Adv Manufacturing Tech 2018;98:1103–1130