optic and overall diameter of 9.8 mm (Fig. 1). The semicircular open haptics have a diameter of 0.2 mm and an angulation of 8 degrees. Lens power ranged between 15.0 and 27.0 dioptres (D).
The one-piece, all-PMMA Anis lens has a plano-convex optic with a 5.5 mm diameter (Fig. 2). The total diameter of the uncompressed lens is 11.0 mm for those less than 24.0 D and 10.0 mm for those greater than 24.0 D. The closed, semicircular haptics are 0.15 mm thick, making them very fl exible. Lens power ranged between 0 and 34.0 D.
From February to December 1993, 122 corneal lenses were implanted. Because some patients receiving this lens were referred to the university by other ophthalmolo-gists, 19 eyes were unavailable for the follow-up at 6 months, reducing the number of lenses in this series to 103.
From May 1993 to July 1994, the Anis lens was implanted in 335 eyes. All patients were seen at the same private practice and were thus available for the 6-month follow-up.
IOLS WITH CIRCULAR HAPTICS
Fig. 1. The Corneal IS M 5.5 lens
Fig. 2. The Morcher type 18 modifi ed Anis lens
Conclusion: The Corneal IS M 5.5 and the Anis lens with circular haptics prevented late optic decentration and, therefore, would be useful in cases of eccentric capsulorhexis, partial zonulysis, anterior radial tears, and posterior capsule rupture. These IOLs may also prevent capsular con-traction.
III.2. INTRODUCTION
Developments in posterior chamber intraocular lens (IOL) design have focused on reducing incision length and the incidence of postoperative lens decentration and posterior capsule opacifi cation (PCO). Posterior chamber lens decentration can cause visual aberrations (Brems et al., 1986; Apple et al., 1987). In addition, good centra-tion becomes more important as increasing numbers of younger patients still in the workforce and with larger, more mobile pupils have IOL implantation.
Most authors agree that in-the-bag fi xation is a safer, more physiologic means of attaining good long-term results (Hansen et al., 1988; Apple et al., 1989; Legler et al., 1992) and that a concentric anterior capsulorhexis helps prevent asymmetric capsular shrinkage, reducing postoperative IOL decentration (Ohmi, 1993; Ohmi et al., 1993; Ohmi et al., 1995). Today, the most frequently used IOLs for capsular bag fi xation after phacosurgery and concentric anterior capsulorhexis have open haptics with a modifi ed J- or C-loop confi guration (Davison, 1993). Although these lenses were designed to make the area of contact between the peripheral haptic and the capsular bag equator as broad and symmetrical as possible, stress lines in the poste-rior capsule and late optic decentration still occur (Apple et al., 1984; Apple et al., 1989; Colvard et al., 1990; Wasserman et al., 1991; Cumming, 1993).
Intraocular lenses with circular haptics were developed to better distribute forces over 360 degrees of the capsular equator. This study evaluated two models of circu-lar-haptic IOLs.
III.3. PATIENTS AND METHODS
This study comprised patients with no pre-existing vision-impairing disease scheduled for surgery at the University Hospital and the Maria Middelares Hospital, Antwerp.
Patients received either a Corneal IS M 5.5 lens or a Morcher type 18 modifi ed Anis lens, both of which have ultraviolet-absorbing optics.
The all-poly(methyl methacrylate) (PMMA) Corneal lens has a 5.5 mm biconvex
Chapter III IOLS WITH CIRCULAR HAPTICS
III.3.2 Follow-up
Patients were evaluated at 1 day, 1 week, and 1 and 6 months postop-eratively. Best-corrected visual acuity (BCVA) was measured at all visits. At 1 and 6 months, pupils were dilated be-yond the IOL edge (to at least 6.0 mm) with tropicamide and phenylephrine.
Eyes were evaluated at the slit-lamp, and the greatest and smallest distanc-es from the IOL edge and the pupil-lary margin were measured. If the IOL
was equidistant from the pupillary margin in all meridians or if there was less than 0.25 mm of decentration, the IOL was considered to be well centered (no decentra-tion). Decentration was assessed by retroilluminating the lens with a narrow slit placed vertically and horizontally across the center of the cornea, focused on the pupillary plane, with the patient fixating on the surgeon’s ear.
Quantitative evaluation was done using a calibrated ocular at the right side (Fig. 4).
This ocular has a 15.0 mm scale in its optic, with each millimetre divided into 10 units, giving final precision of 0.1 mm. When the examiner looks through the slit-lamp under normal magnification, the millimetre scale is projected on the iris. The pupillary area of the posterior capsule was examined, and PCO was clinically divided into three types: Elschnig pearls, mild fibrosis with intact visual acuity, and severe fibrosis impairing vision. A neodymium:YAG (Nd:YAG) laser capsulotomy was per-formed in eyes that lost two or more Snellen lines of BCVA.
III.4. RESULTS
III.4.1 Corneal lens
Best-corrected visual acuity after 1 month was 20/25 or better in 95 % of eyes.
Impaired visual acuity was correlated with macular degeneration. A refractive error of +0.5 D was noted; thus, the given A-value of 118.5 changed to 119.0.
In eyes with a well-centered 4.0 to 5.0 mm capsulorhexis opening overlapping the anterior lens surface, decentration was less than 0.25 mm in the upward direction (Fig. 5). In 19 %, the capsulorhexis opening was not well centered or was oversized, Mean age of all patients was 73 years (range 44 to 87 years). Pseudoexfoliation was
detected in 5 eyes; however, no eye had signs of pseudo-exfoliation syndrome.
III.3.1 Surgical procedure
Corneal lens: Conventional two-handed divide and conquer phaco-emulsification was performed using sodium hyaluronate (Healon®). A 3.2 mm scleral tunnel open-ing of the anterior chamber and 4.5 to 5.0 mm continuous curvilinear capsulorhexis were made. The epithelial cells lining the internal surface of the anterior capsule were aspirated, and any posterior capsule opacity was removed.
The tunnel was enlarged to 5.5 mm. A standard lens forceps, holding the optics and loops or optic alone, was used to place the lens into the inferior capsular bag. With a hooked lens manipulator, both haptics were brought into the superior part of the bag. The lens centered without being rotated. The small hole in the optic remained around the 12 o’clock position. In-the-bag placement was checked in all cases.
The Healon was aspirated from the anterior chamber and capsular bag, and the sclera was closed with one 10-0 nylon suture. A subconjuntival injection of methylprednis-olone and geomycine was given. Postoperative medication consisted of prednismethylprednis-olone and indomethacin eye drops.
Anis lens: The surgical procedure in the Anis lens group was similar to that in the Cor-neal IOL group except the anterior capsule epithelial cells were not aspirated. In addi-tion, the IOL was placed in the capsular bag with a standard lens forceps holding only the optic. With a hooked lens manipulator, the upper part of the lens loop was brought into the superior part of the bag using one or two hands (with the help of a Dardenne hook) without rota-tion (Fig. 3). The optic hole was placed around the 12 o’clock position. No subcon-juntival injection was given. Postoperative treatment included prednisolone, neo-mycin, and polymixin eye drops.
Fig. 3. An Anis lens is placed in the capsular bag with a standard lens forceps.
Fig. 4. The anterior segment seen through the Haag-Streit ocular. The millimeter scale is projected on the iris.
Chapter III IOLS WITH CIRCULAR HAPTICS
III.5. DISCUSSION
After implantation of modified C- or J-loop IOLs, decentration of more than 0.5 mm occurs in about 6 % of eyes (Heider et al., 1993) or more (Colvard et al., 1990).
In most cases, this does not cause clinical problems. However, there are reports of younger patients with glare and other visual aberrations, especially under dim illu-minations. Thus, proper IOL centration is increasingly important.
Today, in-the-bag IOL fixation is considered the most stable technique (Hansen et al., 1988; Apple et al., 1989; Legler et al., 1992). Several studies define other advantages of capsular fixation (Cumming, 1993), particularly in terms of avoiding uveal contact to minimize low-grade inflammation, iris chafing syndrome with micro-hyphema, and pigmentary dispersion syndrome.
The literature suggests that an IOL designed to reduce excessive stress on the capsu-lar bag may produce the most stable fixation (Amon and Menapace, 1993). Although the newer lenses are designed to make the area of contact of the peripheral haptic and the capsular bag equator as broad as possible to avoid two-point fixation, pos-terior capsule stress lines and late optic decentration can occur (Apple et al., 1984;
Apple et al., 1989; Colvard et al., 1990; Wasserman et al., 1991; Cumming, 1993).
The Anis and Corneal IOLs, which have circular loops, were designed to maximize lens contact with the capsular fornix to better distribute forces over nearly 360 degrees.
The posterior capsule will then be equally stressed, and the lens will have better centration and stability.
Both lens models, when fully lodged in the bag with a well-centered capsulorhexis opening, were almost perfectly centered; decentration was less than 0.25 mm and in the upward direction. Even with a radially torn or eccentric capsulorhexis opening with partial optic capture, there were no cases of lens tilt or decentration of more than 0.5 mm. The broad-based, angulated link to the optic prevents anterior luxa-tion of the optic. In one study of eyes with partial zonular dehiscence, a tear in the posterior capsule, or a split in the anterior rim, only minor decentration (less than 0.5 mm) occurred (Davison, 1986). In our study, any minor decentration of the Cor-neal IOL was mostly in the upward direction. This could be because the loops of the lens are not closed at 12 o’clock. Thus, resistance to capsular shrinkage is least at that position. This hypothesis agrees with the lack of vertical decentration in eyes with a closed-loop Anis lens. However, in the literature, it has been observed that decentration of many IOLs is commonly directed superiorly. The exact mechanism is unknown.
Because of the stress-free design of the lenses, distortion of the capsulorhexis did not occur in any eye in our study. Although a few eyes developed dense anterior capsule opacification, they never had the capsular contraction syndrome (Drews and Kreiner, 1987; Cumming, 1993; Davison, 1993). The rigidity of the circular loops resulting in
incom-plete overlapping of the lens optic.
Despite this partial optic capture, decen-tration (in an upward direction) was less than 0.5 mm. There were no cases of to-tal optic capture, secondary disloca-tion (one haptic out of the bag), or cap-sular contraction.
The anterior capsular
opening was not measured postoperatively in every eye, only in those that seemed to have a smaller diameter. No eye reached the 3.0 mm limit.
Intraoperative posterior capsule rupture occurred in three eyes (one with positive vitreal pressure from retrobulbar bleeding, two had mature cataract) and two eyes with a preoperative traumatic partial zonular dehiscence (one 3 to 4 clock hours, one 5 clock hours). In these five eyes, the IOLs could still be placed in the capsular bag;
after 6 months, the IOLs were decentered less than 0.5 mm.
The posterior capsule was always well stretched and in contact with the posterior optic surface. Postoperative stress folds, seen in 3 eyes, disappeared within a few days. After 6 months, 10 eyes (10 %) had a minimal, faint, posterior capsule fibrosis that did not impair vision. Four eyes (4 %) had significant posterior capsule fibrosis that reduced visual acuity and required an Nd:YAG laser capsulotomy.
III.4.2 Anis lens
After 6 months, all patients except those with macular degeneration had a BCVA of 20/25 or better. The same refractive error was noted as with the Corneal IOL, and the A-value was changed to 119.0.
There were no cases of lens decentration, posterior capsular folds, capsular contraction, or pupillary capture. In the four eyes with an intraoperative posterior capsule rupture, the IOL could still be positioned in the capsular bag and secondary lens decentration was less than 0.5 mm. After 6 months, most eyes had minor, diffuse posterior capsule fibrosis that did not impair visual acuity. Fifteen patients (4 %) had an Nd:YAG laser posterior capsulotomy for severe, vision-impairing posterior capsule fibrosis.
Fig. 5. A well-centered Corneal lens 6 months after implantation.
Chapter III IOLS WITH CIRCULAR HAPTICS