IOL SELECTION FOR SULCUS FIXATION

Liliana Werner, MD, PhD and Nick Mamalis, MD

Several studies have described the advantages of implantation of posterior chamber intraocular lenses (PCIOLs) in the capsular bag, in comparison to sulcus fixation after cataract surgery.^1,2 Symmetric in-the-bag IOL fixation, with a complete coverage of the optic periphery by the capsulorrhexis edge, prevents optic interaction with the posterior iris surface. Posterior iris chafing by the loop or the optic portion of sulcus-fixated IOLs may cause a spectrum of disorders, including iris transillumination defects, pigment dispersion with or without elevation of intraocular pressure (IOP), intermittent microhyphemas, and uveitis-glaucoma-hyphema syndrome.^1,2 Therefore, if sulcus fixation is necessary due to posterior capsule complications, selection of the appropriate IOL is of utmost importance (Figure 17-1). In this chapter, we discuss the ideal characteristics of IOLs for standard sulcus fixation or sulcus fixation in a piggyback configuration.

Single-Piece IOLs

Since the introduction of single-piece hydrophobic acrylic lenses in the market, there have been several reports on complications related to the presence of their relatively thick and bulky haptics in the sulcus, whether this fixation site was inadvertent or elective after complicated cataract surgery.^3–6

Single-piece AcrySof lenses (Alcon Laboratories, Inc) have a square optic edge on the anterior and posterior optic surfaces. The finishing of the square edges of these lenses was modified to give the side walls an unpolished or “textured” appearance, which was found to improve postoperative glare phenomena.⁷ This feature was extended along the length of the optic and haptics in the single-piece lenses. Because of the flexibility and thickness/bulk of its haptics, the square optic and haptic edges, and the unpolished side walls, implantation of the single-piece AcrySof lens in the sulcus is not recommended. Furthermore, the haptics of the single-piece lens are planar and therefore do not vault the optic posteriorly from the iris. The overall lens diameter is up to 13.0 mm, which is too short for sulcus fixation in many eyes; if the haptics do not fully extend because of their low compressive force, the IOL will be prone to decentration in the ciliary sulcus of larger eyes.⁴ This same reasoning can also be extended to other commercially available single-piece lenses.

A study from our laboratory reported on single-piece lenses that were explanted because of pigment dispersion syndrome related to the presence of their haptics in the ciliary sulcus (Figure 17-2).³ Those cases revealed the presence of significant amounts of iris pigment on the anterior surface of the lens (optics and haptics). Other similar cases of pigment dispersion with this lens have been described in the literature, which were generally managed with explantation/exchange of the lens or by surgical repositioning within the capsular bag.^4,5

In a retrospective study compiling cases from members of the American Society of Cataract and Refractive Surgery Cataract Clinical Committee, Chang et al described the findings in 30 eyes with sulcus-fixated single-piece lenses (29 single-piece AcrySof, 1 Rayner 570C hydrophilic acrylic design).⁴ Posterior capsule rupture and IOL decentration were observed in approximately two-thirds of the eyes. No IOL was suture fixated to the iris or sclera. At the time of initial consultation, the corrected distance visual acuity ranged from 20/20 to 20/400 and the mean IOP was 22.1 mm Hg. Approximately one-third of the patients were taking at least one IOP-lowering medication. The most common complications were pigment dispersion and iris transillumination defects, followed by IOL edge symptoms and elevated IOP. Intraocular hemorrhage and cystoid macular edema were relatively infrequent. The authors hypothesized that the latter may have been underreported because of the retrospective nature of the data collection.

Similar complications have also been reported with 3-piece AcrySof lenses in a piggyback configuration or standard sulcus fixation.8–14 These lenses also have a square optic edge on the anterior and posterior optic surfaces, with side walls exhibiting a textured appearance. In piggyback implantation, fixation of the anterior lens in the sulcus has been recommended to prevent interlenticular opacification, which is the opacification in the interface between 2 IOL optics implanted within the capsular bag. However, we have described a case of pigment dispersion syndrome resulting from secondary piggyback implantation of a low-power 3-piece hydrophobic acrylic, square-edged IOL in the ciliary sulcus (AcrySof MA60MA; +5 diopters [D]).⁸ Other reports also described cases of pigment dispersion syndrome with these 3-piece hydrophobic acrylic lenses implanted in a piggyback configuration^9,10 or placed electively in the ciliary sulcus following a posterior capsule tear.^11,12 Nevertheless, some authors did not show excessive interaction between these 3-piece, sulcus-fixated lenses and the posterior iris surface, but mostly a transient pigment dispersion.^13,14

Cadaver Eye Studies From Our Laboratory

Two large studies from our laboratory, using pseudophakic human eyes obtained postmortem, highlight the importance of IOL selection for sulcus fixation.^15,16 In the first study, the objective was to provide histopathological evidence of complications related to out-of-the-bag fixation of single- or 3-piece hydrophobic acrylic IOLs with anterior and posterior square optic edges.¹⁵ Pseudophakic cadaver eyes obtained from eye banks within the United States were included in the study. Anterior segment scanning of the eyes with a high-frequency ultrasound system or with a high-resolution anterior segment magnetic resonance imaging was performed followed by gross examination. The eyes were processed for complete histopathological analysis. Some of the IOLs were explanted before histopathological evaluation to allow for direct light microscopic evaluation of the lenses. Eighteen eyes implanted with hydrophobic acrylic IOLs with anterior and posterior square optic edges had asymmetric or sulcus IOL fixation (6 with single-piece, 12 with 3-piece IOLs). They were compared to the contralateral eyes with symmetric in-the-bag IOL implantation.

Pathological findings were composed of IOL decentration and tilt, pigment dispersion within the anterior segment and on the IOL surface, iris transillumination defects, iris changes including vacuolization/disruption/loss of the pigmented layer, iris thinning, and iris atrophy, as well as synechiae and loop erosion in the case of 3-piece lenses. Findings were more significant in comparison with the control contralateral eyes, and were particularly evident in relation to the sulcus-fixated haptic in the case of single-piece lenses (Figure 17-3). The majority of the eyes with 3-piece lenses showed signs of complicated surgery; therefore, all pathological findings in those cases could not be strictly attributed to the out-of-the-bag fixation.¹⁵

In order to further understand these findings, we compared the previous series of 3-piece lenses (square anterior and posterior optic edges) to a series of eyes with out-of-the-bag fixation of 3-piece IOLs that had round anterior optic edges and similar signs of complicated surgery (eg, posterior capsule rupture) in a second study.¹⁶ The methods used were similar to the first study. Thirteen eyes had 3-piece hydrophobic acrylic IOLs with anterior and posterior square optic edges, and 14 eyes had 3-piece lenses with anterior round edges (13 silicone lenses and 1 hydrophobic acrylic lens) without symmetric in-the-bag fixation. These 27 eyes were processed for complete histopathologic analysis. Gross findings in both groups were composed of IOL decentration and tilt, pigment dispersion within the anterior segment and on the IOL surface, and iris transillumination defects. Histopathology of the 14 eyes with 3-piece IOLs with round anterior optic edges showed mild focal disruption of the iris pigmented layer and loop protrusion/erosion in the ciliary sulcus. Additional changes observed in the 13 eyes with square-edged anterior optic IOLs included iris changes such as vacuolization, disruption, and loss of the pigmented epithelial layers; iris thinning and atrophy; synechiae; and pigment dispersion within the trabecular meshwork. One eye also exhibited initial signs of optic nerve disc cupping.¹⁶

The severity of the iris changes in the second study was more prominent in relation to 3-piece lenses with square anterior optic edges.¹⁶ Also, all eyes with these lenses had pigment dispersion within the trabecular meshwork, in comparison to only 1 eye in the group of lenses with round anterior edges.¹⁶ This indicates continuous trauma to the posterior surface of the iris, likely related to rubbing by the square optic edge, although the possibility of preexisting pigment dispersion syndrome prior to cataract surgery cannot be ruled out. Pathologic findings were therefore more severe in eyes implanted with 3-piece IOLs with square anterior optic edges, suggesting that IOLs with round anterior optic edges are more suitable for sulcus fixation.

Ideal Characteristics for Sulcus-Fixated IOLs

Table 17-1 summarizes the ideal characteristics for a sulcus-fixated IOL. Any IOL placed in the ciliary sulcus should have sufficient posterior iris clearance, which can be obtained with a posterior optic-haptic angulation. A 3-piece PCIOL has the advantage of thin, posteriorly angulated C-shaped haptics that will enhance posterior iris clearance and minimize interaction with uveal tissues. The anterior optic surface should be smooth and have rounded and smooth edges to minimize iris chafing should any posterior iris contact occur (Figure 17-4). The overall IOL diameter must be sufficiently long to enhance centration and allow for stable fixation in the sulcus. Most available foldable IOLs intended for fixation within the capsular bag measure 13.0 mm or less from end to end and may be too short for eyes with larger ciliary sulcus dimensions. A larger corneal diameter (12.5 mm or greater) is generally associated with a larger anterior segment.⁴

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