Ординатура / Офтальмология / Английские материалы / Hyperopia and Presbyopia_Tsubota, Boxer Wachler, Azar_2003

Figure 1 Hyperopic Artisan phakic intraocular lens. (Courtesy of Ophtec, Groningen, the Netherlands.)

tissue into the two diametrically opposed “claws” of the lens. It is a one-piece, UVabsorbing, polymethylmethacrylate lens with an overall length 8.5 mm (IOLs 7.5 mm long may also be available) and a diameter of the optical part of 5.0 mm. Its power range is 1.0 to 12.0 D with a 0.5–increment increase (Figs. 1 and 2).

2. Posterior Chamber Phakic IOL

The only marketed hyperopia PC phakic IOL is the STAAR Collamer intraocular lens, also called an implantable contact lens (ICL) and manufactured by STAAR Surgical. It is made of a flexible hydrophilic collagen copolymer, a compound combining HEMA and porcine collagen (less than 0.1%). Its refractive index is 1.45 at 35 C. It is available with lengths of 11.0 to 13 mm. The diameter of the optical zone is 5.5 mm, and the dioptric power ranges from 3 to 17 D (Fig. 3).

C. INDICATIONS/CONTRAINDICATIONS

The best indications are hyperopes of 4 D or more who do not tolerate contact lens, cannot wear spectacle correction for occupational or psychological reasons, and cannot or do not want to undergo alternative refractive procedures. Candidates are often middle-aged or older patients whose visual discomfort is increased by presbyopia. Hyperopes also experience more difficulties in inserting their contact lenses.

Contraindications include

One-eyed patients Unstable refraction

History of ocular disease, including glaucoma, cataract, uveitis, and progressive and/ or severe retinal/choroidal disease

History of connective tissue disease

Corneal endothelial disease and/or endothelial cellular density less than 2000 mm2 Central anterior chamber depth less than 3.0 mm for the Artisan iris-claw lens, and

2.8 mm for the ICL STAAR lens

Pupil larger than 6.0 mm in scotopic luminance

Patients who will obviously not be compliant for lifelong ophthalmological followup

D. PREOPERATIVE PREPARATION

1. IOL Power Calculation

The Artisan iris-claw lens dioptric power is calculated on the basis of the curvature of the cornea (K), the anterior chamber depth, and the spectacle correction by applying the van der Heijde formula (15). It is approximatively the same as the power of the spectacles at a vertex distance of 12 mm.

The STAAR Collamer’s IOL dioptric power is determined using Feingold’s formula (proprietary) that utilizes the refraction, keratometric power, corneal thickness, and anterior chamber depth. The IOL length is the horizontal limbal white-to-white measurement 0.5 mm (not well defined).

2. Anesthesia

Most patients are operated on on an outpatient basis. The anesthesia methods are based on patient and surgeon preferences: general anesthesia or peribulbar injection. Topical anesthesia can be applied for STAAR Collamer lens implantation but not for Artisan irisclaw lens surgery, for which full akinesia and analgesia are required.

3. Pupil Size

Artisan iris-claw lens implantation requires preoperative miosis to protect the natural lens during the insertion and fixation of the IOL. A constricted pupil also facilitates proper centration of the lens. For this purpose, two argon laser marks can be made on the iris at diametrically opposite sites to facilitate proper centration of the IOL during the surgery, contrary to STAAR Collamer phakic lens implantation, which requires full pupillary dilation.

4. Prevention of Pupil Block

A perioperative peripheral surgical iridotomy is performed during the Artisan iris-claw lens implantation procedure, rather than preoperative laser iridotomies. Two generous peripheral laser iridotomies separated by 80 degrees are required before implantation of the STAAR Collamer phakic lens.

E. SURGICAL TECHNIQUE

1. Artisan Iris-Claw Lens

Two side port incisions and a 5.2-mm (superior or temporal) clear corneal or (superior) scleral tunnel incision are made. High-viscosity sodium hyaluronate is injected, and the

Figure 8 Positioning of the haptic of the ICL phakic intraocular lens into the sulcus using a tucker.

2. STAAR Collamer Phakic IOL

A side port incision is performed and viscoelastic material is injected. The foldable implant is inserted through a 3.2-mm clear corneal beveled incision on the steepest axis, either with an injector (Fig. 6) or MacPherson forceps. Care must be taken to orient the lens properly while it unfolds and to avoid any central touch of IOL with the natural lens. The optic disk is centered, and gentle downward pressure using a specially designed instrument makes it possible to place each footplate one after the other behind the iris (Figs. 7 and 8). Then, the viscoelastic material is removed and acetylcholine chloride is injected into the anterior chamber. Postoperative care consists of steroidal and antibiotic eyedrops for 1 to 2 weeks.

F. VISUAL OUTCOMES/COMPARISON OF RESULTS (Tables 1 and 2)

1. Artisan Iris-Claw Lens

Fechner et al. (10) published in 1998 the only study on hyperopic correction using the iris-claw phakic lens. A total of 67 hyperopes were divided into three groups: 6.0 to8.9 D (group 1), 9.0 to 11.9 D (group 2), and more than 12.0 D (group 3). In all groups, the standard deviation between intended and final postoperative uncorrected visual acuities was less than 2.80 D. The refractive results were stable at a follow-up of 4 months, and there was no loss of the mean best corrected postoperative best-corrected visual acuity (BCVA). We implanted nine hyperopic patients, 4.4 to 8.1 D, with a mean follow-up of 12 months (personal communication). Postoperative spherical equivalent (SE) ranged from 0.75 to 0.75 D; 100% and 66.7% of eyes were within 1.00 and 0.50 D of emmetropia, respectively. Because of the loss of magnification, 78% of patients demonstrated a loss in postoperative spectacle BCVA compared to the preoperative spectacle BCVA.

2. STAAR Collamer Phakic IOL

Four studies on hyperopic correction using the STAAR Collamer phakic lens have been published (11–14).

These studies included 9, 24, 15, and 10 hyperopes respectively, the latter study (14) being a phase I clinical trial sponsored by the U.S. Food and Drug Administration. In total, 58 patients underwent STAAR Collamer phakic IOL implantation.

Cumulative data show that preoperative SE ranged from 2.25 to 11.75 D. Mean follow-up ranged from 3 to 12 months. Postoperative SE ranged from 3.88 to 1.50 D; 58 to 80% of eyes were within 0.50 D of emmetropia and 79 to 92.3% of eyes were within 1.00 D of emmetropia. In Rosen’s study (11), the efficacy index was 0.98, which was superior to the index for myopic patients implanted with the same type of phakic IOL in series published by the same authors. Davidorf et al. (12) also compared their results favorably to the predictability in their series of high myopic eyes.

Seven of 24 eyes (29%) (12) and one of 15 eyes (7.69%) (13) lost one or more lines of postoperative BCVA. Conversely, only 8% of hyperopic eyes operated on by Davidorf et al (12) demonstrated a gain in postoperative spectacle BCVA compared to the preoperative spectacle BCVA. This is explained by the loss of magnification induced by the surgery.

G. COMPLICATIONS

In Fechner’s series of the artisan lens, one patient had glaucoma and corneal edema in both eyes (10). In our study, no complications occurred and no change in endothelial cell density was noted after a follow-up of 1 year (personal communication).

For the ICL, postoperative pupillary block glaucoma occurred in 3 of 24 eyes and in 2 of the 15 eyes in the series of Davidorf et al. (12) and Pesando et al. (13), respectively. This complication was due to iridotomies that were too small.

H. SUMMARY

Two types of phakic IOLs are available to correct hyperopia: the Artisan iris-claw lens and the STAAR Collamer PC IOL. These represent the only surgical refractive procedures capable of correcting hyperopia of 4 D or more. There have been very few publications, but the results are encouraging. The predictibility, efficacy, stability, and safety of these procedures are excellent, as well as the quality of the resultant vision. The time of recovery is short and the surgeries are reversible. Long-term follow-up is, however, mandatory with respect to delayed complication such as iris atrophy at the fixation sites and progressive endothelial cell loss (iris-claw lens), and cataract and pigmentary dispersion (PC phakic lens).

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