Journal of Refractive Surgery

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Original Articles 

Posterior Chamber Silicone Phakic Intraocular Lens

António Marinho, MD, PhD; Manuel C Neves, MD; Maria C Pinto, MD; Fernando Vaz, MD

Abstract

ABSTRACT

BACKGROUND: We investigated the efficacy, safety, and stability of correction achieved with a silicone posterior chamber intraocular lens used to correct high myopia in phakic eyes.

PATIENTS AND METHODS: A silicone posterior chamber plate-style intraocular lens (Chiron, Adatomed) was implanted in 38 consecutive phakic eyes with high myopia (-7.00 to -28.00 diopters (D) over a period of 21 months. Follow-up ranged from 3 to 24 months.

RESULTS: Three months after surgery, refractions in 27 eyes (71%) ranged from -1.00 to +1.00 D and remained stable thereafter. Spectaclecorrected visual acuity improved at least two lines in 24 eyes (63%), and none was lost in any eye. Patient satisfaction was high (92%). The few complications that occurred were mostly related to imperfections in the surgical technique rather than lack of biocompatibility of the lens. No cataract or other vision-threatening complication was present at the end of the study.

CONCLUSION: This silicone posterior chamber plate-style intraocular lens provides a reasonably predictable, safe, and stable means of correcting high myopia. [J Refract Surg 1997;13:219-222]

Abstract

ABSTRACT

BACKGROUND: We investigated the efficacy, safety, and stability of correction achieved with a silicone posterior chamber intraocular lens used to correct high myopia in phakic eyes.

PATIENTS AND METHODS: A silicone posterior chamber plate-style intraocular lens (Chiron, Adatomed) was implanted in 38 consecutive phakic eyes with high myopia (-7.00 to -28.00 diopters (D) over a period of 21 months. Follow-up ranged from 3 to 24 months.

RESULTS: Three months after surgery, refractions in 27 eyes (71%) ranged from -1.00 to +1.00 D and remained stable thereafter. Spectaclecorrected visual acuity improved at least two lines in 24 eyes (63%), and none was lost in any eye. Patient satisfaction was high (92%). The few complications that occurred were mostly related to imperfections in the surgical technique rather than lack of biocompatibility of the lens. No cataract or other vision-threatening complication was present at the end of the study.

CONCLUSION: This silicone posterior chamber plate-style intraocular lens provides a reasonably predictable, safe, and stable means of correcting high myopia. [J Refract Surg 1997;13:219-222]

Using intraocular lenses (IOLs) to correct high myopia in phakic eyes is not new. The first attempts (Strampelli1 and Choyce2) failed because of poor quality IOLs and lack of required surgical equipment, eg, operative microscopes. The idea resurfaced in 1987 with the development by Fechner and Worst3'6 of an iris-claw phakic IOL fixed to the iris without touching the anterior chamber angle. Later, Baikoff began to use an anterior chamber multiflex-style IOL, which has since undergone improvements in design.7,9 Both of these IOLs work well and have few complications, but damage to the corneal endothelium can occur.

To eliminate this potential problem, Fyodorov10,11 designed a silicone-plate IOL to be inserted in the posterior chamber between the iris and the crystalline lens. This IOL was modified by ChironAdatomed (Munich, Germany) under the guidance of Fechner and is now commercially available.

We present our experience using this IOL to correct high myopia in phakic eyes and suggest ways of improving its design.

PATIENTS AND METHODS

The Chiron-Adatomed IOL is rectangular, with an overall length of 10.5 to 12.5 mm and an actual width of 6.0 mm. The optical zone is circular, with a diameter of 5.5 mm. It is made completely of silicone (Figure).

The IOL was implanted in 38 eyes of 24 patients (7 men and 17 women) with myopia ranging from -7.00 to -28.00 D (mean, -17.30 ± 5.30 D). Mean patient age was 35 ± 9.18 years. Baseline spectaclecorrected visual acuity was 20/25 in three eyes (7.9%), 20/40 in 16 eyes (40.2%), 20/100 in 15 eyes (39.5%), and 20/200 in four eyes (10.5%). None of the patients had any systemic or ocular disease other than myopia. Eight eyes had peripheral retinal lesions that were treated by argon laser photocoagulation before surgery. All of the patients gave their informed consent before surgery. The goal of correction was emetropía in all eyes.

The size and power of the IOL appropriate for each patient were determined before surgery. We used the following sizes, based on the horizontal limbal white-to-white diameter: white-to-white minus 1 mm, 5 eyes; white-to-white, 8 eyes; whiteto-white plus 1 mm, 25 eyes.

Figure: Present model of Fechner-Fyodorov, Chiron-Adatomed minus power phakic intraocular lens. [Courtesy Fechner P et al. J Cataract Refract Surg 1996;22:179]

Figure: Present model of Fechner-Fyodorov, Chiron-Adatomed minus power phakic intraocular lens. [Courtesy Fechner P et al. J Cataract Refract Surg 1996;22:179]

Ideally, the IOL should have a white-to-white size that allows it to fit perfectly in the ciliary sulcus between the iris and the crystalline lens. However, due to changing indications from the manufacturer during the study and a lack of availability of all sizes in our stock, theoretically ideal sizes were not always used.

We used the following IOL powers base on the baseline spherical equivalent of the mean refraction: -7.00 to -10.00 D, add -1.00 D; -11.00 to -15.00 D, the same power; -16.00 to -20.00 D, subtract -1.00 D; greater than -20.00 D, subtract -2.00 D.

The vertex distance used was always 12 mm.

Before surgery the pupil was maximally dilated with cyclopentolate 1% and phenylephrine 10%. All of the surgeries were performed under peribulbar anesthesia.

A 6.0-mm-long incision was made 1 mm behind the limbus at 12 o'clock and viscoelastic was injected in two steps. In the first step, the anterior chamber was filled, as in cataract surgery; in the second step, the viscoelastic was injected beneath the iris to create a space between it and the crystalline lens. The zonules were clearly visible at this stage. Care was taken not to touch the crystalline lens while injecting the viscoelastic behind the iris.

The cannula was inserted at the 12 o'clock position behind the iris and then moved to the 6 o'clock position along the temporal side, injecting the viscoelastic. The maneuver was repeated along the nasal side.

The superior haptic was grasped with forceps and the IOL was introduced in the eye, placing the inferior haptic in the space created at the 6 o'clock position between the iris and the crystalline lens, as in the previous step. When the inferior haptic was in place, the IOL was pushed downward and the superior haptic was inserted at the 12 o'clock position.

Then, using the viscoelastic cannula, a slight pressure was applied at the optic and the IOL was rotated so that the haptics were positioned at the 2 and 9 o'clock positions. In all eyes, we performed a peripheral iridectomy at the 12 o'clock position. Finally, the viscoelastic was withdrawn by injecting balanced salt solution, and a continuous 10/0 nylon suture was placed.

Postoperatively, all patients used a topical antibiotic (tobramycin) and dexamethasone four times a day for 1 week. Spherical equivalent refraction, cylinder, and spectacle-corrected visual acuity were measured at 24 hours, 1 week, 1 month, 3 months, and yearly thereafter. Patient satisfaction was assessed by verbally questioning patients about their satisfaction with the procedure and their willingness to recommend it to family or friends.

RESULTS

Five eyes were followed for 2 years, 22 eyes for 1 year, nine eyes for 6 months, and two eyes for 3 months.

The mean spherical equivalent of the manifest refraction achieved postoperatively was -0.47 + 1.06 D. Seventy-one percent (27 eyes) had a spherical equivalent refraction between -1.00 to +1.00 D, and 65% (25 eyes) had a spherical equivalent refraction between -0.50 and +0.50 D. Eighteen percent (seven eyes) had a refraction between -1.25 to -2.00 D.

In eyes with baseline myopia greater than -22.00 D, the results obtained were closer to emmetropia than expected, eg, for an eye with -26.00 D of baseline myopia implanted with a 20.00 D lens, the expected residual myopia was -4.00 D, but actually resulted in only -2.50 D of residual myopia. Therefore, in eyes implanted with lenses more powerful than 20.00 D, we should deduct 3.00 D from the lens power.

The mean refractive cylinder before surgery was -1.56 + 1.25 D; after surgery it was -1.16 + 1.80 D. Eighteen percent (seven eyes) retained the same amount of astigmatism; 21% (eight eyes) had increased astigmatism and 60% (23 eyes) had decreased astigmatism.

Safety was evaluated in terms of the effect of the surgery on spectacle-corrected visual acuity. Seven (18.4%) of the eyes retained the same visual acuity, seven gained one line, 14 (37%) gained two lines, and 10 (26%) gained three or more lines. The fact that no eye lost spectacle-corrected visual acuity is an important indicator of the safety of the procedure.

As for stability of correction, there was no significant difference between the refractive and visual acuity results at 1 month for any eye. The mean spherical equivalent refraction at 1 month was -0.47 ± 1.06 D; at 6 months, -0.45 ± 1.23 D; and at 24 months, -0.43 ± 1.37 D. Thus, the results at 1 month remained stable for as long as 24 months.

Ninety-two percent (35) of the patients said they were very satisfied with the results, 8% (three) said they were not.

Complications and Side Effects

Glare was reported at some time in eight eyes. In six, moderate glare was reported by the patients when they were specifically questioned about it. One patient reported severe glare in both eyes and demanded explantation 3 months after surgery; decentration was not observed in this patient.

Moderate uveitis developed in two eyes 5 days after surgery. A hypopyon was present in one of these. In both eyes, the uveitis resolved within 1 week, following use of local and systemic prednisolone and local mydriatics.

In one eye, the IOL was not correctly rotated during surgery, causing the superior haptic to protrude through the iridectomy and touch the cornea, resulting in a focal edema. This IOL was removed 12 months after surgery and replaced with an anterior chamber (Baikoff) IOL, with no further complications. The edema disappeared 3 days after the exchange.

A retinal detachment that developed 9 months after surgery in one eye was successfully managed by a vitreoretinal surgeon. We do not believe this complication was related to the IOL surgery (Table).

Explantation was performed in the three abovementioned eyes as follows: the previous suture was removed and the previous wound was reopened. Viscoelastic was injected in the same way as for the implantation. The IOL was pushed down, causing the superior haptic to move above the iris. Finally, the IOL was gently pulled out of the eye and a new suture placed. No complications resulted from these explantations.

DISCUSSION

Implantation of the silicone plate posterior chamber phakic IOL corrected high myopia with reasonable predictability (27 eyes [71%] were between -1.00 and +1.00 D after implantation) and safety (all of the eyes either retained or gained lines of spectacle-corrected visual acuity). In addition, the results were stable.

Table

TableComplications in 32 Eyes with Silicone Posterior Chamber Platestyle Intraocular Lenses

Table

Complications in 32 Eyes with Silicone Posterior Chamber Platestyle Intraocular Lenses

Although the method we used to calculate the power of the IOL for individual eyes appears simplistic, it was derived using more complicated formulas based on biometry, keratometry, and anterior chamber depth, and proved to be reliable. Determining the ideal size, however, remains problematic. For the time being, based on our data, were prefer to use a whiteto-white (nasal to temporal) +1 mm IOL.

Although ideally the crystalline lens should not be touched at all during surgery, it is difficult to avoid doing so; the practical rule is to touch it as little as possible. We believe an iridectomy is indicated in order to avoid postoperative pupillary block.

Although we feared that cataracts might develop because the IOL is located just in front of the anterior surface of the crystalline lens, after 2 years of follow-up, there was no sign of cataract. The complications that did occur appear unrelated to the IOL material; two were the result of deficient surgical technique (failure to rotate the implant and failure to removal all of the viscoelastic in an eye in which uveitis developed), and one due to an apparently aberrant psychological profile (severe glare).

We suggest the following modifications of the silicone IOL. First, the IOL should be at least 1 mm larger than the white-to-white measurement in order to assure some space between it and the crystalline lens, thereby possibly decreasing the risk of cataract. The cataracts reported to develop following implantation of this IOL (Fechner and Wichmann, personal communication, and at the Congress of the European Society for Cataract and Refractive Surgery, Amsterdam, 1995.) may have resulted from use of a smaller IOL, which left no space between it and the crystalline lens.12 However, if the IOL were vaulted more anteriorly, the same effect might be achieved with a smaller IOL. Second, a softer silicone would allow the IOL to be folded, and hence a smaller incision could be used. Folding the present IOL not only would be difficult but also it might unfold uncontrollably inside the eye, with potentially dangerous consequences for the crystalline lens.

REFERENCES

1. Strampelli B. Supportabilita' di lenti acriliche in camera anteriore nella afachia e nai vizi di refrazione. Ann Ottalomol Clin Oculist 1954;80:70-82.

2. Choyce P. Discussioneto Barraquer: anterior chamber plastic lenses. Results of and conclusions from five years experience. Trans Ophthalmol Soc UK 1959;79:432.

3. Fechner PU, Worst JGF. A new concave intraocular lens for the correction of myopia. Eur J Implant Refract Surg 1989;1:41-43.

4. Fechner PU. Intraocular lenses for the correction of myopia in phakic eyes: short-term success and long-term caution. Refract Corneal Surg 1990;6:242-244.

5. Fechner PU, Strobel J, Wichmann W. Correction of myopia by implantation of a concave Worst iris-claw lens into phakic eyes. Refract Corneal Surg 1991;7:284-298.

6. Fechner PU, Wichmann W. Correction of myopia implantation of minus optic (Worst iris claw) lenses into the anterior chamber of phakic eyes. Eur J Implant Refract Surg 1993;5:55-59.

7. Baikoff G, JoIy P, Bonnet P. Evolution de !'endothelium corneen apres implant myopique. Etude retrospective. Ophtalmologie 1991;5:525-526.

8. Baikoff G. The refractive IOL in a phakic eye. Ophthalmic Practice 1991;9:58-61, 80.

9. Baikoff G. Anterior Chamber Lenses in High Myopic Phakic Eyes. Thorofare, NJ; SLACK; 1992:211-220.

10. Fyodorov SN, Zuev VK, Tumanyan ER1 et al. Analysis of long-term clinical and functional results of intraocular correction of high myopia. Ophalmo Surg (Moscow) 1990;2:3-6.

11. Fyodorov SN, Zuev VK, Aznabayev BM. Intraocular correction of high myopia with negative posterior chamber lens. Ophalmo Surg (Moscow) 1991;3:57-58.

12. Fechner P, Haigis W, Wichmann W. Posterior chamber myopia lenses in phakic eyes. J Cataract Refract Surg 1996;22:178-182.

Table

Complications in 32 Eyes with Silicone Posterior Chamber Platestyle Intraocular Lenses

10.3928/1081-597X-19970501-06

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