Article Date: 10/1/2009

IOL Fixation Techniques

IOL Fixation Techniques

The case for AGIOL

KARIM N. JAMAL, MD · PRAVIN U. DUGEL, MD

There are usually three instances requiring the implantation of an intraocular lens for the vitreoretinal surgeon: a primary implant following pars plana lensectomy a secondary implant in an aphakic eye, and secondary implant in an eye with a subluxed intraocular lens. Since capsular support is either poor or nonexistent in these cases, the surgeon is faced with a decision to place either a sulcus-fixated posterior chamber intraocular lens (PCIOL) or an anterior chamber intraocular lens (ACIOL).

While both are viable options, the surgical technique employed in placement of an open-loop ACIOL is easier and faster.1 Improved surgical approaches have greatly reduced complications in this procedure.2,3 This article outlines why placement of an ACIOL is our preferred IOL technique.

Karim N. Jamal, MD, and Pravin U. Dugel, MD, both practice with Retinal Consultants of Arizona in Phoenix. Neither author reports any financial interest in products mentioned in this article. Dr. Dugel can be reached via e-mail at pdugel@gmail.com.

ADVERSE OUTCOMES OF SUTURED PCIOLs

Sulcus-fixation of PCIOLs is technically complex and requires a considerably longer surgical time.1 Increased time in the operating room carries its own risks: prolonged anesthesia exposure, phototoxicity from the operating microscope, etc.4 In one series, fluorescein angiography revealed light-induced macular injury in 33% of patients undergoing the sulcus-sutured technique.5

The sutures themselves can also lead to complications. Suture entry tracks provide a wick, whereby bacteria may enter the eye, leading to endophthalmitis.6 Over time, suture breakage, which leads to subluxation and possible dislocation of the sulcus-flxed PCIOL, as well as suture erosion, can occur. Inaccurate placement of, or unequal tension on, suture knots can lead to lens tilt with oblique astigmatism,7 suprachoroidal hemorrhage,8 retinal detachment,9 reverse pupillary block,10 or, rarely, extrusion of the implant itself.11

Surgical manipulations in the vicinity of the well-vascularized ciliary body have risks as well. For instance, intraoperative vitreous hemorrhage is a concern. In the postoperative phase, recurrent hemorrhage either from irritation of the pars plicata or from chafing of the posterior iris can lead to decreased vision and increased pain and may necessitate surgical explantation.

A retrospective series examining complications associated with primary and secondary implantation of scleral-sutured PCIOLs found that 51.9% of patients with primary and 48.1% of eyes with secondary implantation had an early postoperative complication.12 The most frequent were vitreous hemorrhage (24.7%), CME (19.5%), and keratopathy (14.3%). There was no significant difference between primary versus secondary implantation.

Subluxed posterior chamber intraocular lens, partially supported by capsular remnants.

DISPELLING MYTHS SURROUNDING THE ACIOL

While some vitreoretinal surgeons eschew the use of ACIOLs, fears imprinted years ago are, in our opinion, currently largely unfounded. Such concerns have included corneal decompensation, secondary glaucoma, uveitis, hyphema and cystoid macular edema (CME).

It is important to note that the majority of these adverse events are associated with the older closed-loop ACIOL. Modern open-loop, vaulted ACIOLs have been designed to prevent these complications.13 In 2003, an ophthalmic technology assessment authored by the American Academy of Ophthalmology reported that open-loop ACIOLs do not have the unacceptable rate of complications associated with the closed-loop model.14 The review also stated that there was no evidence indicating that visual outcomes following open-loop ACIOL implantation were any less satisfactory when compared to scleral- or irissutured PCIOLs. Along with the improved lens design, further safety is afforded by deepening of the anterior chamber following cataract surgery, as evidenced by recent anterior-segment imaging modalities.15,16

A longitudinal cohort study found no difference in endothelial cell loss two years following corneal transplantation with placement of an open-loop ACIOL vs an iris-sutured PCIOL.17 Another recent study reported that, at two years, endothelial cell density in eyes with an ACIOL was not significantly different from values obtained on initial examination, indicating that endothelial cell loss was related more to surgical trauma itself rather than the continued presence of the lens implant.18 Moreover, patients who had an ACIOL in one eye and a PCIOL in the fellow eye did not have a statistically significant difference in endothelial cell density between the two eyes.

Additional compelling evidence regarding the risks of the ACIOL itself has been provided by Hennig and associates,19 who prospectively evaluated outcomes of open-loop ACIOL insertion to aphakic controls. This study confirmed that there was no significant increase in corneal decompensation or CME between the two cohorts. While the population receiving intraocular lenses did have a significant increase in glaucoma, the number of patients affected was low (1.3%). However, in light of this data, we feel that it is reasonable to obtain consultation from a glaucoma specialist in any patient with a history of, or at high risk for, glaucoma prior to ACIOL implantation.

Chronic uveitis following ACIOL implantation, such as toxic lens syndrome and uveitis-glaucoma-hyphema (UGH) syndrome, are also mostly of historic interest. These complications were caused by poorly finished lenses and designs that caused mechanical injury to the iris and angle structures, leading to a breakdown of the blood-aqueous barrier.20 Improvements in ACIOL design have made these adverse events rare. Although traditionally associated with ACIOLs, UGH syndrome is not exclusive to this lens type. Several case reports exist of UGH syndrome developing in eyes with sutured PCIOLs, requiring explantation.21–23

COMPARISON STUDIES

There are several case series that compare outcomes of ACIOL placement to scleral-sutured PCIOLs. One comparison study of secondary implantation of openloop ACIOL vs scleral-fixated PCIOL found no significant difference in best corrected postoperative visual acuity between the two groups.24 A study by Donaldson et al.25 similarly found no significant differences in postoperative visual acuity or in side-effect profiles of ACIOLs compared to sutured PCIOLs. Kwong et al.26 published a series of primary implantation of the two lens designs in which a significantly higher percentage of eyes receiving an ACIOL implant achieved a postoperative best-corrected visual acuity of 20/40 or better.

In the largest series comparing open-loop ACIOL placement versus a control group receiving scleral-sutured PCIOLs, the incidence of CME and glaucoma escalation was nearly identical.27

CONCLUSION

Advances in surgical technique, as well as lens design, have made the traditional adverse events associated with ACIOL placement largely of historical interest only. As the American Academy of Ophthalmology notes, the overall incidence of the most common complications seen with open-loop ACIOLs is relatively low and is likely not further reduced by scleral-fixed lenses.14 Since the implantation of scleral-sutured PCIOLs carries a higher technical difficulty, is more time-consuming, and does not yield a superior safety profile, placement of an ACIOL should be, in our opinion, the procedure of choice for the vitreoretinal surgeon in patients without advanced glaucoma. RP

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Retinal Physician, Issue: October 2009