Ординатура / Офтальмология / Английские материалы / Mastering theTechniques of Lens Based Refractive Surgery (Phakic IOLs)_Garg, Alio, Dementiev_2005

astigmatism can be reduced by choosing a suitable incision in relation to the astigmatism axis. The implantation of a toric VerisyseTM should be considered for the correction of relatively high astigmatism.

BIBLIOGRAPHY

1.Alexander L, John M, Cobb L, Noblitt R, Barowsky RT. U.S. clinical investigation of the Artisan myopia lens for the correction of high myopia in phakic eyes. Report of the results of phases 1 and 2, and interim phase 3. Optometry 2000; 71(10):630-42.

2.Budo C, Hessloehl JC, Izak M, Luyten GP, Menezo JL, Sener BA, Tassignon MJ, Termote H, Worst JG. Multicenter study of the Artisan phakic intraocular lens. J Cataract Refract Surg 2000; 26(8):1163-71.

3.Chipont EM, Garcia-Hermosa P, Alio JL. Reversal of myopic anisometropic amblyopia with phakic intraocular lens implantation. J Refract Surg 2001; 17(4):460-2.

4.Dick HB, Alio J, Bianchetti M, Budo C, Christiaans BJ, ElDanasoury MA, Guell JL, et al. Toric phakic intraocular lens: European multicenter study. Ophthalmology 2003; 110(1):150-62.

5.El Danasoury MA, El Maghraby A, Gamali TO. Comparison of iris-fixed Artisan lens implantation with excimer laser in situ keratomileusis in correcting myopia between –9.00 and -19.50 diopters: a randomized study. Ophthalmology 2002;109(5):955-64.

6.Fechner PU, Haubitz I, Wichmann W, Wulff K. WorstFechner biconcave minus power phakic iris-claw lens. J Refract Surg 1999; 15(2):93-105.

7.G.L. van der Heijde. Some Optical Aspects of Implantation of an IOL in a Myopic Eye. Eur J Implant Ref. Surgery. 1989; 245-48.

8.Guell JL, Vazquez M, Gris O, De Muller A, Manero F. Combined surgery to correct high myopia: iris claw phakic intraocular lens and laser in situ keratomileusis. J Refract Surg 1999; 15(5):529-37.

9.Guell JL, Vazquez M, Gris O. Adjustable refractive surgery: 6-mm Artisan lens plus laser in situ keratomileusis for the correction of high myopia. Ophthalmology 2001; 108(5):945-52.

10.Malecaze FJ, Hulin H, Bierer P, Fournie P, Grandjean H, Thalamas C, et al. A randomized paired eye comparison of two techniques for treating moderately high myopia: LASIK and artisan phakic lens. Ophthalmology 2002;109 (9):1622-30.

11.Maloney RK, Nguyen LH, John ME. Artisan phakic intraocular lens for myopia:short-term results of a prospective, multicenter study. Ophthalmology 2002; 109(9):1631-41.

12.Menezo JL, Cisneros AL, Rodriguez-Salvador V. Endothelial study of iris-claw phakic lens: four year followup. J Cataract Refract Surg 1998; 24(8):1039-49.

13.Tehrani M, Dick HB. Implantation of an ARTISANtrade mark toric phakic intraocular lens to correct high astigmatism after penetrating keratoplasty. Klin Monatsbl Augenheilkd 2002; 219(3):159-63.

14.Tehrani M, Schwenn O, Dick HB. Toric intraocular lens to correct high astigmatism after penetrating keratoplasty in a pseudophakic eye-a case report]. Klin Monatsbl Augenheilkd 2001; 218(12):795-9.

Yoon H, Macaluso DC, Moshirfar M, Lundergan M. Traumatic dislocation of an Ophtec Artisan phakic intraocular lens. J Refract Surg 2002;18(4):481-3.

Birgit Lackner (Austria)

INTRODUCTION

Poor visual quality of spectacle corrected high ametropia and frequent intolerance to contact lenses justified the introduction of a new technology in the correction of high ametropia.1-4 The concept of the posterior chamber phakic intraocular lens for the correction of moderate to high myopia carries certain advantages over previous surgical methods, like preservation of accommodation and potential reversibility.5,6 The STAAR posterior chamber phakic intraocular lens, termed ICLTM, was introduced in 1993. This lens, similar to the last generation of Fyodorov lenses, is made of a hydrophilic copolymer of porcine collagen and Hydroxy-Ethyl-Methyl-Acrylate (HEMA). Initial investigations reported excellent efficiency, predictability and peri-operative safety of this design. 5-7

In some cases eyes are not suitable for anterior phakic IOL implantation, because of relatively flat anterior segments, reduced intraocular space, an increased risk of angle closure glaucoma and uveal effusion.8

Clear lens extraction (CLE) has been used with good results in high myopia, but a higher risk of retinal detachment and consequent loss of accommodation must be considered.9-11

With longer observation times, it has become obvious that ICL implantation is associated with an elevated incidence of opacifications of the crystalline lens, which can worsen visual outcome after ICL, and even necessitate cataract surgery.12-16

The introduction of the recent model ICM V4 was therefore followed with considerable expectations due

to a improved lens design and vaulting to reduce the risk for cataract formation.

Our clinical experience with the ICM V4 model is herein considered as a report of the outcome of 76 eyes of 46 patients, with a mean patient age of 48.3 ± 7.4 years. In all 76 eyes, the ICL was implanted successfully without the necessity of revisions. Mean and median observation times after ICL implantation were 20.1 months and 24.0 months (± 11.5 months), respectively. The postoperative visual and refractive outcome was excellent. Anterior subcapsular lens opacifications occurred in 11/76 (14.5%) eyes. Eyes with opacifications showed reported difficult surgeries with possible intraoperative microtrauma of the crystalline lens and advanced age over 50 years. We did not observe a correlation between ICL vaulting and the risk of lens opacifications. After onset of lens opacification, 6/11 eyes (55%) showed stable best corrected visual acuity 0.5 lines. The remaining 5 eyes showed progressive opacificationsandlostbetween3.5and0.5linescompared to the best postoperative values. Three eyes in the progressive group showed best corrected visual acuity loss between 1 and 2 lines compared to preoperative data and subsequently underwent cataract surgery.

PATIENT SELECTION

The candidate for an ICL implant must be subjected to a preselection process to accomplish following criteria: Preoperative refractive error over –5 D of spherical equivalent, age over 21 years, stable refraction for >12 months, corneal diameter >11 mm, and anterior chamber depth (ACD) >2.8 mm, absence of opacifications of the crystalline lens, intraocular pressure in the normal range (10 – 21 mmHg), absence of iris pigment defect or iris transillumination, absence of retinal breaks or degenerations.

ICL SELECTION AND IMPLANTATION

ICL power is selected based on subjective refraction, keratometry and ACD. Lens power calculations are aimed at emetropia for refractive errors that required ICL powers up to –21.0 D, and at reduction of myopia (after

consenting to a residual myopic error) if the necessary correction exceeds the strongest available lens power. ICLs are manufactured in appropriate size (length), which is determined based on horizontal white-to-white corneal diameter measured with a corneal topography system (Orbscan II, Bausch & Lomb), and ACD measured by optical pachymetry (Jaeger II, Haag-Streit). All calculations regarding lens power and size are performed by STAAR Surgical Inc. using a modified vertex formula based on the above parameters.

Two weeks before scheduled ICL implantation, two peripheral neodymium:yttrium-aluminium-garnet laser iridectomies performed at the 10:30 and 1:30 positions are recommended to prevent the possibility of postoperative pupillary block after ICL insertion.

ICL

The STAAR ICL CollamerTM Implantable Contact Lens (ICLTM) is a proprietary biocompatible hydrophilic copolymer consisting of hydroxyethyl methylacrylate (HEMA) and porcine collagen. Collamer is a hydrophilic material with high biocompatibilty and permeability to oxygen and metabolites. The lens has a water content of 34 percent, a light transmission of 99 percent, and a refractive index of 1.45.

The current ICL model shows a one-piece plate design with a rectangular shape, 7.5 to 8.0 mm wide, available in four standard overall lengths (with differences of 0.5 mm between different lengths): 11.5 to 13.5 mm for myopic lenses (ICM) and 11.0 to 13.0 mm for hyperopic lenses (ICH) in order to adapt to eyes of different sizes. The size of the central optic is variable, ranging from 4.65 to 5.5 mm in the ICM, depending on the chosen dioptric power, and constantly 5.5 mm for ICHs. The ICL is supplied in powers ranging from –3.00 to –23.0 D for myopic, and +3.0 D to +21.0 D for hyperopic lenses.

In our department a standardised surgical technique is used under peribulbar anesthesia. After pupil dilation a viscoelastic fluid is instilled into the anterior chamber. The ICL is implanted through a 3.2 mm temporal clear cornea incision (CCI) with the use of an injector cartridge

(STAAR Surgical AG Nidau, Switzerland). The ICL is placed in the posterior chamber, anterior to the crystalline lens under protection of the previously applied viscoelastic substance. Viscoelastics were removed with an irrigation/aspiration system and mioticum is instilled. The corneal incision is left sutureless.

During surgery, care should be taken to prevent the surgical instruments from touching the anterior crystalline lens capsule. Postoperatively, nonsteroidal antiphlogistic and antibiotic medications should be administered locally four times daily over four weeks.

COMPLICATIONS

Reports of ICL—induced anterior subcapsular lens opacifications have been described in the literature, but no clear etiology has been established.12,14,17,18 The genesis of lens opacification after ICL implantation may be multifactorial. Initially, surgical trauma secondary to learning curves associated with surgical skill was proposed to be a main reason for immediate cataract. 17,19

Earlier studies postulated direct surgical trauma of the crystalline lens to be responsible for the majority of opacifications.6 Long-term studies have revealed a substantial amount of late events (>12 months after surgery), thus arguing against direct trauma having a causative role.16 Manipulations during implantation surgery may influence the integrity of the lens capsule and can lead to proliferation of subcapsular lens epithelial cells. Other studies do indicate that direct contact between the ICL and the crystalline lens represents a significant risk factor for opacifications.14,17

Prolonged subclinical inflammation and induced changes of the blood-aqueous barrier, could also cause metabolic disturbances of the crystalline lens that in turn could trigger a decrease in lens transmittance. These phenomena have also been observed after the implantation of angle-fixated anterior chamber phakic lenses.

A relationship between ICL vaulting and cataract formation is subject of discussion.

A lens to lens contact could induce metabolic changes in the crystalline lens caused by alteration of the lens

nutrition and reduced aqueous flow. The myopic ICL lens has a convex-concave optic zone, which allows for the presence of a central space between the ICL and the crystalline lens that is occupied by aqueous humor. The vaulting of the anterior capsule of the crystalline lens and posterior surface of the ICL influence the central distance between these two structures. Given the natural convex shape of the anterior crystalline lens surface, the vaulting is reduced peripherally. But during pupillary activity and accommodation there is a potential risk of ICL-lens touch at the rim of the shoulder, which is the thickest part of the posterior ICL surface.

The most recent ICL model V4 has higher inherent vaulting and is designed to provide a larger distance to the crystalline lens. However, the ratio of ICL length/ posterior chamber width is difficult to reliably predict due to the inaccuracy of the approximation of the posterior chamber width (calculated from the corneal white-to-white distance).20

The well positioned ICL does not rest on the zonules and is not in contact with the crystalline lens, allowing a continuous flow of aqueous humor. Given the good biocompatibility to uveal structures of Collamer it seems that the suspected disrupted blood-aqueous barrier is caused by microtraumas due to the constant friction between the posterior iris surface on the ICL or its haptic on the ciliary sulcus.

In individual cases also biocompatibility has to be discussed. Individual sensitiveness of the crystalline lens may also be an explanation of bilateral developed opacifications. Moreover, the age of the patients is of some importance, because in older and female patients opaci-fications tended to occur earlier.16

In our patient collective, perioperative complications were low. The only severe complication is the formation of opacifications of the crystalline lens.

Old age, female sex and early opacification of the contralateral eye after ICL implantation are independent significant risk factors for early formation of opacifications, whereas previous surgery, different ICL models or degree of ametropia had no significant effect.

Figure 12.1: Opacification

Figure 12.2: ICM 3D

Figure 12.3: ICM flat

Our experience suggest that treatment with the ICL of severe myopia is feasible, produces favourable and predictable results, but also a certain risk of the necessity of subsequent cataract surgery, which has to be communicated to the patient (Figs 12.1 to 12.3).

REFERENCES

1.Applegate RA, Howland AC. Magnification and visual acuity in refractive surgery. Arch Ophthalmol 1993;111: 1335-42.

2.Lovisolo CF, Pesando PM, eds. The Implantable Contact Lens (ICLTM) and other phakic IOLs. Fabiano Editore, Canelli (AT) Italia, 1999:315-8.

3.Colin J, Mimouni F, Robinet A, Conrad H, Mader P. The surgical treatment of high myopia: comparison of epikeratoplasty, keratomileusis and minus power anterior chamber lenses. Refract Corneal Surg 1990;6:245-51.

4.Baikoff G Joly P. Comparison of minus power anterior chamber intraocular lenses and myopic epikeratoplasty in phakic eyes. Refract Corneal Surg 1990;6:252-60.

5.Rosen E, Gore C. Staar Collamer posterior chamber phakic intraocular lens to correct myopia and hyperopia. J Cataract Refract Surg 1998; 24:596-606.

6.Zaldivar R, Davidorf JM, Oscherow S. Posterior chamber phakic intraocular lens for myopia of –8 to –19 diopters. J Refract Surg 1998;14:294-305.

7.Assetto V, Benedetti S, Pesando P. Collamer intraocular contact lens to correct high myopia. J Cataract Refract Surg 1996; 22:551-56.

8.Davidorf JM, Zaldivar R, Oscherow S. Posterior chamber phakic intraocular lens for hyperopia of +4 to +11 diopters. J Refract Surg 1998;14(3):306-11.

9.Goldberg MF. Clear lens extraction for axial myopia: an appraisal. Ophthalmology 1987; 94:571-82.

10.Siganos DS, Siganos CS, Pallikaris IG. Clear lens extraction and intraocular lens implantation in normally sighted hyperopic eyes. J Cataract Refract Surg 1994;10:117-24.

11.Lyle WA, Jin GJ. Clear lens extraction for the correction of high refractive error. J Refract Corneal Surg 1994; 20:273-6.

12.Fink AM, Gore C, Rosen E. Cataract development after implantation of the Staar Collamer posterior chamber phakic lens. J Cataract Refract Surg 1999; 25:278-82.

13.Zaldivar R, Oscherow S, Ricur G. The STAAR posterior chamber phakic intraocular lens. Int Ophthalmol Clin 2000;40:237-44.

14.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; 29:91824.

15.Jimenez-Alfaro I, Benitez del Castillo JM, Garcia-Feijoo J, et al. Safety of posterior chamber phakic intraocular lenses for the correction of high myopia: anterior segment changes after posterior chamber phakic intraocular lens implantation. Ophthalmology 2001;108:90-99.

16.Lackner B, Pieh S, Schmidinger G, et al. Outcome after treatment of ametropia with implantable contact lenses. Ophthalmology 2003.

17.Sanchez-Galeana CA, Smith RJ, Sanders DR, et al. Lens opacities after posterior chamber phakic intraocular lens implantation. Ophthalmology 2003; 110:781-85.

18.Trindade F, Pereira F. Cataract formation after posterior chamber phakic intraocular lens implantation. J Cataract Refract Surg 1998; 24:1661-63.

19.Sanders DR, Vukich JA, Doney K, et al. US Food and Drug Administration clinical trial of the Implantable Contact Lens for moderate to high myopia. Ophthalmology 2003; 110:255-66.

20.Gonvers M, Othenin-Girard P, Bornet C, et al. Implantable contact lens for moderate to high myopia: short-term follow-up of 2 models. J Cataract Refract Surg 2001; 27:380-88.

Maria I Kalyvianaki

George D Kymionis

Ioannis G Pallikaris (Greece)

INTRODUCTION

Refractive surgery is characterized by its constant evolution and the development of new techniques. After many improvements in their design, phakic intraocular lenses (IOLs) have grown to be the method of choice for the correction of high refractive errors. To this contributes the fact that the use of excimer laser has some limitations concerning the amount of corneal tissue that can be removed.1,2 Specifically, the predictability and stability of photorefractive techniques decrease with the amount of the attempted correction while corneal ectasia might occur as a consequence of large ablation depths. Additionally, altering the shape of the cornea in high attempted photorefractive corrections may result in poor quality of vision,3 while the implantation of a phakic intraocular lens is a potentially reversible technique, which doesn’t affect the shape of the cornea. Compared with the clear lens extraction method for treating high refractive errors,4,5 phakic IOL implantation is less invasive and preserves accommodation. Therefore it is more appropriate than clear lens extraction for treating myopia in young patients.

Currently, three kinds of refractive lenses are used for correcting refractive errors: anterior-chamber lenses, which are supported in the anterior chamber angle, irisfixated lenses, and posterior-chamber refractive lenses.

The surgical technique of the implantation of an anterior chamber lens supported in the anterior chamber angle is comparatively simple. Yet the complications of these lenses are the damage to the corneal endothelium, mostly during the first year after their implantation, pupil ovalization with iris atrophy, anterior uveitis and elevation of IOP.6-8

Iris fixated lenses require a more sophisticated surgical technique.9 Although they may have a good refractive outcome10 and are considered safer for the corneal endothelium,11 as they are not fixated in the angle, they also may result in localized iris ischemia and to endothelial cell loss due to surgical trauma.12

The Phakic Refractive Lens (PRL™, Medennium, Inc., USA) is a posterior chamber lens made of silicone. Its hydrophobic material allows the lens to float in the posterior chamber having no contact with the crystalline lens.13,14

HISTORY OF POSTERIOR

CHAMBER LENSES

In 1986 Fyodorov and his colleagues15 implanted the first posterior chamber phakic IOL that was made of silicone and constituted the first generation of PRLs. This first design was a pupil-fixated IOL that was implanted with the optic in the anterior chamber while the haptics remained in the posterior chamber. The complications of pupillary block, iridocyclitis, and cataract formation forced those developing the lens to improve the design. The second generation PRL rested in the posterior chamber and was supported in the sulcus.

At the end of 1993, a posterior chamber lens made of Collamer16 (a copolymer of Hydroxy-Ethyl-Methyl- Acrylate and porcine collagen), the Implantable Contact Lens (Staar Surgical AG, Switzerland), was developed. The implant, which is supported in the posterior chamber angle vaulting over the crystalline lens, is reported to have good refractive results.16-21

The PRL™ presented in this chapter is a third generation silicone posterior-chamber IOL, which floats in the posterior chamber, rather than relying on the angle for support.13,14

PREOPERATIVE EVALUATION—PRL MODEL

SELECTION

High myopes over the age of 18 with a stable refraction who wish refractive surgery are candidates for PRL

implantation for the treatment of their myopia. Exclusion criteria include age less than 18 years, previous intraocular surgery, anterior chamber depth less than 3 mm, glaucoma or intraocular pressure at initial measurement greater than 20 mmHg, any sign of cataract and any intraocular or systemic disease.

A thorough preoperative examination is mandatory in all patients. This includes manifest and cycloplegic refraction, corneal topography, pachymetry, A-scan ultrasonography (Axis-II, Quantel medical, Bozeman, MT, USA), slit-lamp microscopy, pupil size measurement under scotopic conditions, white-to-white corneal diameter measurement with the use of a calliper, applanation tonometry, measurement of high order aberrations, and dilated fundus examination.

The selection of the myopic PRL™ model to be implanted is based on the white-to-white measurement. If this is more than 11.3 mm, PRL101 is chosen, otherwise PRL100 is inserted. The power of the implant is calculated by the company using the preoperative cycloplegic spherical equivalent, the anterior chamber depth calculated by the A-scan ultrasonography, the keratometry readings and the target postoperative refraction.

OPERATIVE TECHNIQUE

PRL™ implantation requires gentle manipulations, as the implant is rather delicate and it should not touch the endothelium or the crystalline lens of the eye during surgery.

One hour before surgery cyclopentolate 1 percent and phenylephrine 5 percent are used every fifteen minutes to dilate the pupil. No atropine should be used for this purpose, because at the end of the surgery the pupil must be constricted. Surgery is performed under retrobulbar anesthesia that ensures the immobility of the eye. PRLs™ are implanted through a 3.2 mm clear cornea temporal incision made with a diamond knife. The anterior chamber is then filled with a low viscosity viscoelastic agent. At this step, the special loading block

is filled with basic salt solution (BSS) and PRL™ is placed on its recess with the special forceps. With the use of these forceps the lens is inserted through the main incision parallel to the iris. A high viscosity viscoelastic agent can be used at this point, in order to push the implant downwards. With a manipulator through the main incision the haptics of the lens, one after another, are placed under the iris. To prevent pupillary block, an iridectomy is performed at 12 o’clock as peripherally as possible using the probe of a vitreotome. When iridectomy is made with the use of scissors, a paracentesis has to be performed at 12 o’clock.

POSTOPERATIVE MANAGEMENT—

EVALUATION

At discharge each patient is given one tablet of Acetazolamide 250 mg. Antibiotic-steroid combination drops are prescribed for two weeks. In case of elevated intraocular pressure during the first postoperative month, IOP-suppressants are used until the normalization of IOP.

Patients are typically examined on the first postoperative day, at one week and at one, three, six, nine and twelve months postoperatively. After the first postoperative day, the examination includes uncorrected visual acuity, best-corrected visual acuity, manifest refraction, corneal topography, slit lamp microscopy, tonometry and wavefront aberrometry. At six and twelve months the examination also includes gonioscopy and dilated fundoscopy. The implant is most easily observed behind a dilated pupil and can be rotated (Fig. 13.1), as it floats in the posterior chamber.23

COMPLICATIONS

The main short or long-term risk of the implantation of a posterior chamber lens is cataract formation in case of touch of the crystalline lens during surgery or because of contact between the phakic and the crystalline lens.20,23 In case of focally-stable (not progressing) anterior capsule opacification that can occur during surgical iridectomy (5%) or because of touch of the crystalline lens during surgery (1% in our case series), no further treatment is needed (Fig. 13.2) while in progressive cataract formation (1% in our case series, due to surgical trauma), the lens has to be explanted and cataract extraction has

Figure 13.1: Slit-lamp photograph of an eye one-year post PRL™ implantation (dilated pupil). The implant is better observed with retroillumination. The rotation of the PRL™ causes no visual symptoms

to be performed.

Another uncommon complication is iris atrophy (Fig. 13.3), due to surgical manipulations and bleeding during surgical iridectomy that usually ceases in few minutes with no further consequences. In addition, 20 percent of the patients complain of glare and halo during night. These night phenomena could be explained by the fact that these patients had large pupils, 6 and 7 mm at scotopic conditions, while the optic zone of the implant is 5 mm. Because not all the patients with large pupils

Figure 13.2: Slit-lamp photograph of an eye six months post PRL™ implantation. A focal opacity behind surgical iridectomy is noticed

Figure 13.3: Slit-lamp photograph of an eye three months post PRL™ implantation. A temporal iris trauma due to surgical manipulations is observed with retroillumination, as well as a large iridectomy at 12 o’clock

experienced these phenomena, perhaps other factors besides the size of the pupil contribute to their existence. However, the quick visual recovery during the first postoperative week, the stable refractive outcome, the satisfactory UCVA and the gain in BCVA Snellen lines compensated the patients for these night problems.

Increased intraocular pressure (IOP) (higher than 20 mmHg) has been observed during the first postoperative month (18%). In most of the cases high IOP occurred due to corticosteroid-response (or residual viscoelastic during the first postoperative days), which is frequent in high myopic patients, because intraocular pressure returns to normal levels after discontinuation of steroid drops. In case of resistant increase of IOP (such as in patients with undiagnosed preoperative glaucoma), several options have to be discussed with the patient (topical medications, removal of the implants).

PRL™ RESULTS

Our first published clinical results have shown the effectiveness, the predictability, the stability and the safety of this technique in treating high myopia.22 In our study (61 eyes) mean preoperative spherical equivalent ranged from –7.50 to –21.625D (mean value –13.76 ± 2.96D) and decreased to –0.47 ± 0.78 (mean value, SD) with a range from –2.50 to 0.875D 1-year post PRL

implantation. The refractive outcome demonstrated stability from the first postoperative month. Eighty percent and 54 percent of the treated eyes were within ±1.00D and ±0.50D of target refraction respectively. One eye lost two lines of BCVA, while 70 percent of the treated eyes gained 1 to 5 Snellen lines (decimal scale) of BCVA. These results are comparable with those reported for other posterior chamber refractive lenses.16-21

Higher order aberrations of a small case series measured at pupil of 5 mm with the use of WASCA analyzer (Carl Zeiss, Meditec, Jena, Germany) remained almost unchanged after the operation. A decrease in spherical aberration after PRL™ implantation was noticed, which could be a benefit for the mesopic vision of these eyes.

Of great importance is the evaluation of intraocular pressure at all postoperative intervals, as well as the correlation of the findings to the preoperative values, in order to early estimate any IOP changes due to the presence of the phakic lens. We found an IOP increase only during the first postoperative month, probably due to residual viscoelastic during the first postoperative days and to corticosteroid-response after the first fifteen days.

In conclusion, phakic refractive lens implantation is a promising technique for correcting high myopia. It is an effective and safe technique, which provides a stable refractive outcome and a good quality of vision with a low rate of intraoperative and short-term complications. In almost four years, no eye has developed cataract due to contact between the crystalline lens and the implant and no eye has presented pigment dispersion, which is a vision threatening complication that might follow the implantation of a posterior chamber IOL due to irritation of the posterior surface of the iris.24 However, close monitoring of all treated eyes is essential, in order to detect any crystalline lens changes caused by this posterior chamber phakic lens, or any other potential consequences of the PRL™ existence inside the eye. More patients and longer follow-up period are needed to establish this method as the long-term safest one for treating high myopia.