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Implantable Contact Lens

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Correspondance:Centre for Sight Group of Eye Hospitals, New Delhi, India

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Introduction:

Management of high refractive errors especially with thin cornea is a refractive challenge.  Lasik for correcting high refractive errors has the drawbacks of lack of predictability, regression, corneal ectasia, and induction of high order aberrations1. The Implantable Contact lens (ICL) is a preferred modality for correction of high myopia and for patients with thin corneas. It was first developed in the late 1980’s in Russia by Dr. S. Fyodorov and the first implant was placed in Europe in 1993. Fyodorov introduced the concept of a soft phakic lens in the space between the iris and the anterior surface of the crystalline lens. Earlier, the material used was silicone; now, the material used is collamer.
 

Indications and pre-requisites:

Implantable contact lens is indicated for placement in the posterior chamber of the phakic eye for correction of moderate to high myopia ranging –3.0 D to –20.0 D. Toric  ICL (TICL) can correct upto -3 to -23 D of sphere and + 1.0 to + 6.0 D of  cyl. The toric ICL has the same overall design as the spherical ICL with the addition of a toric optic. The toricity is manufactured in the plus cylinder axis, within 22 degrees. The STAAR® Visian ICL™ is made from a combination of copolymer and collagen called Collamer®. This Collamer® implantable contact lens reduces reflections and glare, and the collagen makes it extremely biocompatible. It is made-up of 60% poly-HEMA, Water (36%), Benzophenone (3.8%) and Collagen (0.2%), it attracts the deposition of fibronectin on the lens surface, inhibits aqueous protein binding and makes the lens invisible to the immune system.


Calculation of power: ICL/TICL calculation and implantation software (Fig 1) allows calculation of spherical and cylindrical power, length and generates the ICL/TICL implantation diagram (Fig 2).

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Fig 1: TICL calculation software     Fig 2: TICL implantation diagram


Measurement of white to white diameter: In the pre-operative planning, the critical parameter in sizing the ICL is the white-to-white (WW) measurement which can be measured with a Pentacam, OrbScan, UBM or using calipers (Fig 3 a& b). In myopic eyes, to determine the overall length (in mm) of the ICL, add 0.5 mm to the horizontal WW measurement. If the ICL is too short for the sulcus, the lens vault may be insufficient to clear the crystalline lens, exposing it to the risk of an anterior capsular cataract. If it is too long, the lens will vault excessively, crowding the angle and possibly causing closed angle glaucoma.

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Fig 3 a: Measuring the white-to-white diameter with calipers
Fig 3 b: Measuring the white-to-white diameter with pentacam (Schiempflug image)


Vault: Ideal ICL vault is approximately 500 μm, which is roughly one corneal thickness. There are concerns about high vault (1000 μm) leading to angle crowding and resulting in angle closure or synechiae formation. High vault may also increase iris chaffing and pigment dispersion, resulting in pigmentary glaucoma. Furthermore, low vault (125 μm) may also cause ICL contact with the crystalline lens and increase the risk of cataract formation over time.
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Peripheral iridotomy: A peripheral iridotomy is performed 1-2 weeks before the surgery to provide an outlet for the aqueous flow around the lens. Alternatively it may be performed intra-operatively after ICL implantation with a Vannas scissors or a vitrectomy cutter. It should be sufficiently wide (at least 500 μm), positioned superiorly (from 11 to 1 o'clock) and well away from the haptics placement.


PROCEDURE:

The procedure is performed under topical anaesthesia. After making a 0.6mm side port, a 3.2-mm clear corneal incision is made on the steep meridian. The lens is introduced with angled-suture forceps or through the injector and positioned behind the iris on a horizontal axis with a cyclodialysis spatula (Fig 4-7). To control for potential cyclotorsion in a supine position, the zero horizontal axis is marked preoperatively on the slitlamp. The lens is implanted temporally and gently rotated to align the axis with the cylindrical axis of the patient. Complete removal of viscoelastic material is essential. Presence of residual viscoelastic material behind the implant may cause opacification of the crystalline lens. A miotic agent is injected and the aspiration is completed. The incision is closed by hydrating the corneal incision.

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Fig 4: The STAAR ICL Injection System

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Fig 5: Introducing the injector into the eye  Fig 6: ICL being slowly implanted in the eye 

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Fig 7: ICL placed behind the iris and in front of the lens  Fig 8: Post-op slit lamp view of ICL

Discussion

At our hospital,i we have treated 110 eyes of 63 patients of which 23% were males and 77% females. Spherical ICL was implanted in 25% and Toric ICL in 75% of the eyes. Degree of myopia ranged from -2.5 to - 22.5 DS. The highest cylindrical power treated was -5.5 D. Though most patients had a myopic refractive error, we have also done 3 eyes who received ICL after C3R treatment for keratoconus while 2 eyes had hyperopia with astigmatism. 95% recovered BCVA in 1-2 days. 100% recovered BCVA by 1 week. Various studies have reported that phakic TICL implantation is a good option for the correction of moderate to high myopia, 4,5  hyperopia,6  high myopic astigmatism, in eyes with keratoconus 7,8 , correction of hyperopia post radial keratotomy 9,10  and post penetrating keratoplasy 11.
 Kamiya   et al 1 studied long-term clinical outcomes of implantation of Visian implantable lens for moderate to high myopia in  56 eyes of 34 patients with myopic refractive errors of -4.00 to -15.25 diopters (D). They concluded that implantation of ICLs is safe and effective and provides predictable and stable refractive results in the treatment of moderate to high myopia during a 4-year observation period.
Pesando et al 6 evaluated ICL in 49 hyperopic eyes of 34 patients. Preoperatively, the spherical equivalent (SE) was between +2.75 D and +11.75 D and astigmatism was between +0.50 D and +1.00 D. The mean postoperative SE of the manifest refraction was +0.07 ± 0.54 D; refraction stabilized quickly and remained stable throughout the follow-up period. The results confirmed the long-term safety, efficacy, accuracy, and predictability of ICL for hyperopia.
Alfonso et al
7 evaluated the efficacy, predictability and safety of myopic phakic posterior chamber ICL to correct myopia associated with keratoconus. They showed that spherical equivalent refraction was within ±1.00 D of the desired refraction in all cases and 84% of cases were within ±0.50 D.
Alfonso et al
11 suggested that phakic intraocular lens implantation is a viable treatment for myopia and astigmatism after PKP in patients for whom glasses, contact lenses, or corneal refractive surgery is contraindicated.
Studies comparing ICL implantation with wavefront guided lasik by Igarashi et al
12  have shown that ICL implantation induces significantly fewer ocular HOAs than wave front guided LASIK.  Kamiya et al 13  compared Collamer toric ICL implantation and wavefront-guided laser in situ keratomileusis for high myopic astigmatism and found that all eyes in the ICL group and 71% of eyes in the LASIK group were within ±1.00 D of the targeted SE correction at 6 months. They suggested that Toric ICL implantation was better than wavefront-guided LASIK in eyes with high myopic astigmatism in almost all measures of safety, efficacy, predictability, and stability.
The overall complication rate with ICL is low and most patients have a good visual recovery. The incidence of glare, haloes and night driving problems is also minimal.
Intra-operatively, it is crucial to load the ICL in the injector in a straight and smooth manner to implant it correctly in the posterior chamber. Improper loading may lead to an upside down implantation. The visco-elastic material must also be removed carefully and meticulously to prevent a post operative IOP spike. We had 1 case of retinal detachment and one case had shallow AC on 1st POP day which recovered in 5-7 days.
Sanders et al 14 studied incidence of anterior subcapsular opacities and cataracts 5 years after surgery in the Visian implantable collamer lens FDA trial. Approximately 6% to 7% of eyes developed anterior subcapsular opacities at 7+ years following ICL implantation but only 1% to 2% progressed to clinically significant cataract during the same period, especially very high myopes and older patients. Visual outcome following cataract extraction was good. Other reported complications of ICL are pigment dispersion and lens deposits
15, acute angle closure glaucoma16, late subluxation of ICL17, endophthalmitis 18 and retinal detachment19

Conclusion: In our experience, the ICL is a safe and effective modality for correction of high myopia and for patients with thin corneas with excellent and stable post operative results. Advancements in anterior segment imaging and measurement technologies such as ultrasonic biomicroscopy, optical coherence tomography and Scheimpflug imaging are now providing valuable information about anterior segment anatomy. This will further allow custom-designed phakic intraocular lenses with proper sizing making ICLs invaluable for correction of moderate to high refractive errors.

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Video of the procedure

References:

  1. Kamiya K, Shimizu K, Igarashi A, Hikita F, Komatsu M. Arch Ophthalmol. Four-year follow-up of posterior chamber phakic intraocular lens implantation for moderate to high myopia. Arch Ophthalmol. 2009 Jul; 127(7):845-50.
  2. Gonvers M, Othenin-Girard P, Bornet C, Sickenberg M. Implantable contact lens for moderate to high myopia: short-term follow-up of 2 models. J Cataract Refract Surg. 2001; 27:380-388.
  3. Pop M, Payette Y, Mansour M. Predicting sulcus size using ocular measurements. J Cataract Refract Surg. 2001; 27:1033-1038.
  4. Gonvers M, Bornet C, Othenin-Girard P. Implantable contact lens for moderate to high myopia: relationship of vaulting to cataract formation. J Cataract Refract Surg. 2003 May;29(5):918-24.
  5. usitalo RJ, Aine E, Sen NH, Laatikainen L.  Implantable contact lens for high myopia. J Cataract Refract Surg. 2002 Jan; 28(1):29-36.
  6. Pesando PM, Ghiringhello MP, Di Meglio G, Fanton G. Posterior chamber phakic intraocular lens (ICL) for hyperopia: ten-year follow-up. ( J Cataract Refract Surg 2007;33(9):1579-84.
  7. Alfonso JF, Palacios A, Montés-Micó R.Myopic phakic STAAR collamer posterior chamber intraocular lenses for keratoconus. J Refract Surg. 2008 Nov; 24(9):867-74.
  8. Kamiya K, Shimizu K, Ando W, Asato Y, Fujisawa T. Phakic toric Implantable Collamer Lens implantation for the correction of high myopic astigmatism in eyes with keratoconus. J Refract Surg. 2008 Oct;24(8):840-2.
  9. Kamiya K, Shimizu K. Implantable Collamer lens for hyperopia after radial keratotomy.J Cataract Refract Surg. 2008 Aug; 34(8):1403-4.
  10. Srinivasan S, Drake A, Herzig S.  Early experience with implantable collamer lens in the management of hyperopia after radial keratotomy. Cornea. 2008 Apr;27(3):302-4.
  11. Alfonso JF, Lisa C, Abdelhamid A, Montés-Micó R, Poo-López A, Ferrer-Blasco T. Posterior chamber phakic intraocular lenses after penetrating keratoplasty. J Cataract Refract Surg. 2009 Jul; 35(7):1166-73.
  12. Igarashi A, Kamiya K, Shimizu K, Komatsu M Visual performance after implantable collamer lens implantation and wavefront-guided laser in situ keratomileusis for high myopia.  Am J Ophthalmol. 2009 Jul;148(1):164-70.
  13. Kamiya K, Shimizu K, Igarashi A, Komatsu M. Comparison of Collamer toric implantable [corrected] contact lens implantation and wavefront-guided laser in situ keratomileusis for high myopic astigmatism. J Cataract Refract Surg. 2008 Oct; 34(10):1687-93.
  14. Sanders DR. Anterior subcapsular opacities and cataracts 5 years after surgery in the visian implantable collamer lens FDA trial. J Refract Surg. 2008 Jun; 24(6):566-70.
  15. Chung TY, Park SC, Lee MO, Ahn K, Chung ES. Changes in iridocorneal angle structure and trabecular pigmentation with STAAR implantable collamer lens during 2 years. J Refract Surg. 2009 Mar; 25(3):251-8.
  16. Chan KC, Birchall W, Gray TB, Wells AP. Acute angle closure after implantable contact lens insertion unresponsive to surgical peripheral iridectomy. J Cataract Refract Surg. 2008 Apr; 34(4):696-9.
  17. R. Kaufer, G. Kaufer.  Late subluxation of an ICL Journal of Cataract & Refractive Surgery, Volume 31, Issue 6, Pages 1254-1255.
  18. Allan BD, Argeles-Sabate I, Mamalis N. Endophthalmitis rates after implantation of the intraocular Collamer lens: survey of users between 1998 and 2006. J Cataract Refract Surg. 2009 Apr; 35(4):766-9.
  19. Domènech NP, Arias L, Prades S, Pujol O, Rubio M, Caminal JM. Acute onset of retinal detachment after posterior chamber phakic intraocular lens implantation. Clin Ophthalmol. 2008 Mar; 2(1):227-31.