Abstract. Med. J. Cairo Univ., Vol. 78, No. 2, December: , 2010

Transcription

1 Med. J. Cairo Univ., Vol. 78, No. 2, December: , A Comparative Study of Endothelial Cell Loss after the Implantation of Posterior Chamber Phakic IOL (ICL) Versus Foldable Anterior Chamber Iris-Fixated Phakic IOL (Veriflex) HAZEM M. YASSIN, M.D.; AHMED E.M. HABIB, M.D.; AHMED A. ABD EL-KADER, M.D. and NAHLA B. ABU HUSSEIN, M.D. The Department of Ophthalmology, Faculty of Medicine, Cairo University Abstract Purpose: To evaluate the endothelial cell loss after implantation of posterior chamber phakic intraocular lenses as compared to anterior chamber iris fixated phakic intraocular lenses. Setting: Al-Oyoun Al Dawli Hospital, Cairo, Egypt. Methods: A comparative prospective non randomized study involved 30 eyes divided into 2 groups. Group A included 15 eyes of 9 patients that have implanted posterior chamber phakic intraocular lens (ICL, Staar Surgical). Group B included 15 eyes of 8 patients that have implanted foldable anterior chamber iris fixated phakic intraocular lens (Veriflex, AMO). Non contact specular microscopy was done preoperatively and at the 3 rd, 6th and 12th months postoperatively. Results: In both groups, there was a statistically significant loss of endothelial cells over time at 3 months, 6 months and ly (p<0.001). In the ICL group, the mean percentage loss of endothelial cells at 3 months, 6 months and ly was 1.34% ±0.51, 2.53%±0.9 and 4.74%±1.24 respectively. In the Veriflex group, the mean % loss of endothelial cells at 3 months, 6 months and ly was 2.42% ±2.4, 4.0%±2.86 and 5.47±3.23 respectively. However, the difference between both groups was statistically insignificant ( p=0.749). Conclusion: Continuous endothelial cell loss was observed after the implantation of posterior chamber phakic IOLs (ICL) (Implantable collamer lens) as well as in anterior chamber iris fixated foldable phakic IOLs (Verifelx) during the first year of postoperative follow-up. However the differences in cell loss observed between the two groups of patients were statisticaslly insignificant. Further analysis of the relation between endothelial cell loss and the distance between the corneal endothelium and the implanted lens may be required in further studies. Long term follow-up of those patients could help demonstrate the long term pattern of cell loss. Key Words: Posterior chamber phakic intraocular lenses ICL Iris claw lenses Veriflex. Correspondence to: Dr. Hazem M. Yassin, The Department of Ophthalmology, Faculty of Medicine, Cairo University. 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 photo-refractive techniques decreases 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 while the implantation of a phakic intraocular lens is a potentially reversible technique, which doesn t affect the shape of the cornea [3]. Compared with the clear lens extraction method for treating high refractive errors, phakic IOLs implantation is less invasive and preserves accommodation in addition to the reduced risk of development of retinal detachment after surgery. Therefore, it is more appropriate than clear lens extraction for treating myopia in young patients [4]. Currently, three kinds of refractive lenses are used for correcting refractive errors: Anteriorchamber lenses (implanted between the cornea and the iris and are supported in the anterior chamber angle), iris-fixated lenses, and posterior-chamber lenses (placed between the iris and the crystalline lens) [5]. The surgical technique of the implantation of angle-supported anterior-chamber lens is comparatively simple. Yet the complications of these lenses 731

2 732 A Comparative Study of Endothelial Cell Loss after the Implantation are the damage to the corneal endothelium, pupil ovalization with iris atrophy, anterior uveitis and elevation of IOP [6,7]. The iris fixated foldable claw lense in this study (Veriflex, AMO) is a convex-concave lens design with 2 opposed haptics to enable fixation on the midperipheral iris. It requires a more sophisticated surgical technique [5,8]. Although they may have a good refractive outcome, [9] and are considered safer for the corneal endothelium, [10] 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 [11-13]. Yet, although the surgery with the iris claw principle is demanding, it has the considerable optical advantage that the centering of the lens over the pupil or visual axis is dependent on surgeon ability rather than angle situation (as with angle supported PIOLs) or difficult sulcus measurements (as with posterior chamber PIOLs) [14]. The posterior-chamber phakic intraocular lense in this study (ICL, Staar Surgical) is implanted in the posterior chamber of the eye, that is, between the iris and the crystalline lens). Since that, these lenses can produce acute glaucoma due to pupillary block, such that two Yag laser iridotomies or a wide surgical iridectomy need to be undertaken before the implant procedure [12,15,16]. The introduction of recent model ICM V4 (FDA approved 2004) for myopic eyes with improved lens design and vaulting reduced incidence of cataract formation and increased its safety [5]. Aim of work: To evaluate the endothelial cell loss after the implantation of posterior chamber phakic intraocular lenses (Implantable collamer lens ICL, Staar surgical) as compared to anterior chamber iris fixated phakic intraocular lenes (Veriflex, AMO). Patients and Methods This study is a prospective non randomized comparative case series involving 30 eyes divided into 2 groups. The study was started in February 2008 and the last visits of the final patients were in May Group A includes 15 eyes that have done implantation of posterior chamber phakic IOL (ICL, Staar Surgical). Group B includes 15 eyes that have done anterior chamber iris-fixated foldable phakic IOL (Veriflex, AMO). Inclusion criteria for ICL implantation were stable myopia greater than 10.0 diopters (D), unsuccessful attempts to wear contact lenses, a normal anterior segment with an anterior chamber depth greater than 2.8mm for ICL implantation or greater than 3.2mm for Veriflex implantation, a white to white distance greater than 1 1mm in cases of ICL implantation and an endothelial cell density greater than 2300cells/mm 2. Exclusion criteria were corneal pathology, crystalline lens opacity, pseudoexfoliation or pigment dispersion glaucoma, intraocular inflammation, macular pathology and personal or family history of retinal detachment. All patients provided written informed consent. The preoperative examination included uncorrected and best corrected visual acuities, subjective refraction, biomicroscopy, Goldmann applanation tonometry, and indirect ophthalmoscopy in mydriasis. Anterior segment scheimpflug imaging by pentacam HR (Oculus GmbH, Germany) was done for keratometry, pachymetry and assesment of the anterior chamber depth and white to white distance. Endothelial cell density was assessed by non contact specular microscopy. Photographs were taken of the central corneal endothelium at each visit. ICL diameter, power and optic size calculations were performed by STAAR surgical Inc. using a modified vertex formula with targeted postoperative emmetropia and adequate lens vaulting. Similarly, the Veriflex power was calculated by AMO using the mean corneal curvature, adjusted ACD, and the SE of the subjective manifest refraction at a 12mm vertex. The insertion of the ICL was carried out under either general or local anesthesia. Maximal pupil dilation was obtained with tropicamide 1%, and phenylephrine 2.5%. A 3.2mm self sealing temporal clear corneal incision was made and Sodium hyaluronate 1% was injected into the anterior chamber in all cases. The ICL was implanted with an injector anterior to the iris plane. Both haptics of the ICL were placed beneath the iris with an intraocular lens manipulator, achieving a horizontal orientation. After the remaining viscoelastic material was removed, a miotic solution is then injected into the eye to constrict the pupil. A couple of peripheral iridotomies were then done using vitrectomy cutter to avoid potential postoperative pupillary block. The corneal wound was closed by stromal hydration. Patients who were implanted with Veriflex were prepared with topical miotic to avoid the risk of lens touch during surgery and to facilitate the haptics enclavation and lens centration over the visual axis. Surgery was performed under general or local anesthesia. Typically, a primary 3.2mm incision was performed at 12 o clock (for inserting

3 Hazem M. Yassin, et al. 733 the lens) and 2 stab incisions were placed at 10 and 2 o clock (8.5 to 9.0mm apart, for enclavation needle access) in the direction of the enclavation sites. Sodium hyaluronate 1% was injected into the anterior chamber in all cases and the lens was inserted using the implantation Spatula. After the lens positioning, the iris tissue was grasped and enclavated into the haptics with aid of an enclavation needle. A peripheral iridotomy was then made surgically. The remaining viscosurgical material was then removed and the corneal self sealing wound was closed with stromal hydration. In both groups of patients, topical antibiotic (gatifloxacin 0.3%) and prednisolone acetate (1%) were administered 4 times daily postoperatively and were gradually tapered over 4 weeks. Patients in both groups were followed-up over a year after implantation. After the first postoperative month, follow-up visits to assess the endothelial cell density were scheduled at 3, 6 and 12 months postoperatively. In this study, data was analyzed using the ANO- VA two-way test for repeated measurements. Numerical data is expressed as mean ± standard deviation. The comparison between two groups was done using the corresponding non-parametric Mann-Whitney test for variables not normally distributed. A p-value less than 0.05 is considered significant and less than is considered as highly significant. Results In Group A, 44.4% of patients were males and 55.6% were females while in group B, 50% were males and 50% were females. The mean age of patients in The ICL group was 25±4.6 while the mean age of patients in the Veriflex group was 25.9±3.9. The difference between both groups was not statistically significant (p= 0.39). Patients' characteristics in both groups are shown in Table (1). Table (1): Patients' characteristics. Characteristics Group A (ICL) Group B (Veriflex) Number of patients 9 8 Sex, N (%): Male 4 (44.4%) 4 (50%) Female 5 (55.6%) 4 (50%) Number of eyes Age (years): Mean 25± ±3.9 Range The change between preoperative and postoperative spherical equivalent (SE), BSCVA & UCVA between both groups are shown in Table (2). Table (2): Mean preoperative and postoperative SE, UCVA and BSCVA in both groups. Examination Group A (ICL) Group B (Veriflex) SE: Mean 16.95±2.86D 11.87± 1.91D Range Postoperative SE (12 months): Mean 0.57±0.65D 0.4±0.8D Range BSCVA (Snellen decimal): Mean 0.7± ±0.2 Range Postoperative UCVA (12 months): Mean Range 0.8± ± Postoperative BSCVA (12 months): Mean Range 0.9± ± Table (3) and Chart (1) show the mean endothelial cell density (ECD) and its change over time in both groups. In both groups, there was a statistically significant loss of endothelial cells over time at 3 months, 6 months and ly ( p<0.001). In the ICL group, the mean percentage loss of endothelial cells at 3 months, 6 months and 12 months postoperatively was 1.34% ±0.51, 2.53%± 0.9 and 4.74% ± 1.24 respectively. In the Veriflex group, the mean % loss of endothelial cells at 3 months, 6 months and ly was 2.42%±2.4, 4.0%±2.86 and 5.47±3.23 respectively. However, the difference between both groups was statistically insignificant (p=0.749). Table (3): Mean endothelial cell density (ECD) and its change over time in both groups (cells/mm 2 ). Examination Group A (ICL) Group B (Veriflex) Preoperartive: Mean ± ±320.8 % loss 3 months postoperative: Mean ± ±313.3 % loss 1.34± ±2.4 6 months postoperative: Mean ± ±316.9 % loss 2.53± ±2.86 : Mean ± ±328.3 % loss 4.74± ±3.23

4 734 A Comparative Study of Endothelial Cell Loss after the Implantation Group A (ICL) Group B (Veriflex) Mean ECD 12m Mean ECD 6m Mean ECD 3m Mean postopertively postopertively postopertively preoperative ECD Chart (1): Mean endothelial cell density (ECD) and its change over time in both groups (cells/mm 2 ) The changes in endothelial cell density in selected cases in both groups are shown in the fol- lowing figures as captured by non contact specular microscopy. Fig. (1): and specular microscopy results for case number 5 in group A. Fig. (2): and specular microscopy results for case number 10 in group A.

5 Hazem M. Yassin, et al. 735 Fig. (3): and specular microscopy results for case number 9 in group A. Fig. (4): and specular microscopy results for case number 9 in group B. Fig. (5): and specular microscopy results for case number 2 in group B.

6 736 A Comparative Study of Endothelial Cell Loss after the Implantation Fig. (6): and specular microscopy results for case number 4 in group B. In both groups, there were no serious intraoperative complications. In the ICL group, 4 eyes had a spike of elevated intraocular pressure exceeding 21mmHG during the first 48 hours after surgery (range 24-36mmHG). In 3 of the 4 eyes, elevated IOP was probably due remnants of viscoelastic material behind the lens while a YAG laser iridotomy had to be done after surgery in one eye to complete a non patent surgical peripheral iridotomy. All eyes regained normal IOP by the end of the first postoperative week. In the Veriflex group, 6 eyes had an IOP exceeding 21mmHg during the first postoperative 48 hours (range, 23-32mmHg) and normal IOP was regained after the first postoperative week. The elervated IOP in those eyes was due to pigment dispersion and anterior uveitis which was treated with topical corticosteroids. Along the course of one year follow-up, there was no evidence of lens changes or opacification in both groups, no reported retinal complications or persistent IOP elevation. However, in the Veriflex group, pigmernt precipitates were observed on the lens haptics and optic in 5 eyes and were persistent during the first year but without affecting visual acuity or IOP levels. Discussion Although implantation of phakic lenses is an effective and predictable method of correcting high myopia or hyperopia, the surgical correction of high degree ametropia is still controversial [17]. In our study, there was a significant loss of endothelial cells over the first year after surgery in both groups of phakic IOL implantation. In the ICL group, there was continuous cell loss over the first postoperative year after the implantation of ICL compared to preoperative levels. This agrees in some way with those results in another study of the long-term effects of ICL implantation on the corneal endothelium, [18-20] in which continuous cell loss (6.6%) was observed over a 2-year followup. Similarly, endothelial cell loss after Veriflex implantation was confirmed in other studies involving similar anterior chamber foldable irisfixated phakic IOLs, [21] in which there was a cell loss of 1.79% after the first year of surgery. However, such difference in the percentage endothelial loss compared to our study could be due differences in the type and design of IOL implanted (Artiflex, Ophtec.), differences in surgical technique or postoperative treatment. Therefore, it is of great importance to consider several parameters during preoperative patient selection, such as patient age and configuration of the iris and the ACD. The importance of sufficient ACD recently was emphasized in a publication by Saxena, et al. [22]. The cause of endothelial cell loss after phakic IOL implantation is multifactorial. After any surgical procedure in the anterior segment, endothelial cell density decreases in proportion to the time of surgery and the type of procedure [23]. For example, after cataract surgery with posterior chamber IOL implantation, the endothelial loss is approximately 2.5% a year [24]. Thus, the endothelial cell loss after phakic IOL implantation may be mainly a result of the surgical procedure. It is likely that significant cell loss occurs in a temporal or superior direction to the corneal incision because of the creation of the incision and implantation of the IOL. The compensatory changes that occur in the endothelium during recovery from surgical trauma, such as the migration of cells from the central cornea to the area where the surgical trauma occurred, may account for the significant central cell loss over the first postoperative years [25].

7 Hazem M. Yassin, et al. 737 With a mean cell density of 3000cells/mm 2 at 20 years of age, physiological endothelial cell loss is reported to be approximately 0.6% per year [26]. This indicates that apart from aging as a factor of endothelial loss over time, phakic IOL implantation plays an additional role in endothelial cell loss. A mean of 1.34%, 2.53% and 4.74% loss of endothelial cells was observed after the 3 rd, 6th and 12th month following surgery in the ICL group respectively while a mean of 2.42%, 4.00% and 5.47% loss of endothelial cells was observed at the 3 rd, 6th and 12th month following implantation in the Veriflex group respectively. The IOL might also be a reason for the endothelial cell loss. In studies of the long-term effects on the corneal endothelium after IOL implantation in cataract patients, the endothelial cell loss was higher in eyes with IOLs than in those without [27,28]. Progressive endothelial cell loss has been suggested to be the result of a chronic, smoldering uveitis associated with IOLs. Chronic subclinical inflammation has also been observed in phakic eyes with IOLs [29]. This smoldering uveitis may be the reason for the higher rate of loss of endothelial cells observed in the Veriflex group compared to the ICL group. Also,with anterior chamber phakic IOLs, endothelial cell loss may ensue from intermittent contact between the IOL optic edge and the corneal endothelium at the midperiphery when the patient rubs his or her eyes; this may set off a mechanism that causes endothelial damage in phakic eyes with anterior chamber IOLs [18-20]. In conclusion, continuous endothelial cell loss was observed after the implantation of posterior chamber phakic IOLs (ICL) as well as in anterior chamber iris fixated foldable phakic IOLs (Verifelx) during the first year of postoperative follow-up. However the differences in cell loss observed between the two groups of patients were statisticaslly insignificant. Further analysis of the relation between endothelial cell loss and the distance between the corneal endothelium and the implanted lens maybe required in further studies. Long term follow-up of those patients could help demonstrate the long term pattern of cell loss. References 1- PEREZ-SANTONJA J.J., BELLOT J.J., CLARAMONTE P., et al.: Laser in situ keratomileusis to correct high myopia. J. Cataract Refract Surg., 23: , PALLIKARIS I.G., KYMIONIS G.D. and ASTYRAK- AKIS N.L.: Corneal ectasia induced by LASIK. J. Cataract Refract Surg., 27: , APPLEGATE R.A. and HOWLAND H.C.: Refractive surgery, optical aberrations, and visual performance. J. Refract Surg., 13: 295-9, LYLE W.A. and JIN G.J.C.: Clear lens extraction for correction of high refractive error. J. Cataract Refract Surg., 20: 273-6, LOVISOLO C.F. and REINSTEIN D.Z.: Phakic Intraocular Lenses: Diagnostic and Surgical Techniques. Surv. Ophthalmol., 50 (6) November-December PEREZ-SANTONJA J.J., IRADIER M.T., SANZ- IGLASIAS L., et al.: Endothelial changes in phakic eyes with anterior chamber lenses to correct high myopia. J. Cataract Refract Surg., 22: , ALIO J.L., DE LA HOZ F., PEREZ-SANTONJA J.J., RUIZ-MORENO J.M. and QUESADA J.A.: Phakic anterior chamber lenses for the correction of myopia. A 7- year cumulative analysis of complications in 263 cases. Ophthalmology, 106: , DOORS M., EGGINK F.A., WEBERS C.A. and NUIJTS R.M.M.A.: Late-Onset Decentration of Iris-Fixated Phakic Intraocular Lenses: A Case Series. Am. J. Ophthalmol., 147: , BUDO C., HESSLOEHL J., IZAK M., LUYTEN G.P.M., MENEZO J.L., SENER B.A., TASSIGNON M.J., TER- MOTE H. and WORST J.G.F.: Multicenter study of the Artisan phakic intraocular lens. J. Cataract Refract Surg., 26: , MALONEY R.K., NGUYEN L.H. and JOHN M.E.: Artisan Phakic Intraocular Lens for myopia. Short-term results of a prospective, multicenter study. Ophthalmology, 109: , MENEZO J.L., CISNEROS A.L. and ROTRIQUEZ- SALVADOR V.: Endothelial study of iris-claw phakic lens: Four year follow-up. J. Cataract Refract Surg., 24: , ALIO J.L.: Advances in phakic intraocular lenses: Indications, efficacy, safety, and new designs. Current Opinion in Ophthalmology, 15: 350-7, TAHZIB N.G., BOOTSMA S.J., EGGINK F.A.G.J. and NUIJTS R.M.M.A.: Functional Outcome and Patient Satisfaction after Artisan Phakic Intraocular Lens Implantation for the Correction of Myopia. Am. J. Ophthalmol., 142: 31-9, COPPENS J.E., VAN DER BERG T.J. and BUDO C.J.: Biometry of phakic intraocular lens using Scheimpflug photography. J. Cataract Refract Surg., 31: , HOYOS J.E., DEMENTIEV D.D., CIGALES M., HOYOS-CHACON J. and HOFFER K.J.: Phakic refractive lens experience in Spain. J. Cataract Refract Surg., 28: , LOVISOLO C.F. and PESANDO P.: ICL Posterior Chamber Phakic IOL. In; Ali J.J., Perez-Santonja J.J., Eds. Refractive Surgery with Phakic IOLs. Fundamentals and Clinical Practice. Panama: Highlights of Ophthalmology International, Chapter 11: , SANDERS D.R., BROWN D.C., MARTIN R.G., et al.: Implantable contact lens for moderate to high myopia: Phase 1 FDAclinical study with 6 month follow-up. J. Cataract Refract Surg., 24: , 1998.

8 738 A Comparative Study of Endothelial Cell Loss after the Implantation 18- ROSEN E. and GORE C.: Staar Collamer posterior chamber phakic intraocular lens to correct myopia and hyperopia. J. Cataract Refract Surg., 24: , SANDERS D.R., BROWN D.C., MARTIN R.G., et al.: Implantable contact lens for moderate to high myopia: Phase 1 FDA clinical study with 6 month follow-up. J. Cataract Refract Surg., 24: , ASSETTO V., BENEDETTI S. and PESANDO P.: Collamer intraocular contact lens to correct high myopia. J. Cataract Refract Surg., 22: 551-6, DICK H.B., BUDO C., MALECAZE F., et al.: Foldable Artiflex phakic intraocular lens for the correction of myopia. Two year follow-up results of a prospective European multicentric study. Ophthalmology, 116: 671-7, SAXENA R., BOEKHOORN S.S., MULDER P.G., et al.: Long-term follow-up of endothelial cell change after Artisan phakic intraocular lens implantation. Ophthalmology, 115: , RAO G.N., AQUAVELLA J.V., GOLDBERG S.H. and BERK S.L.: Pseudophakic bullous keratopathy; relationship to preoperative corneal endothelial status. Ophthalmology, 91: , BOURNE W.M., NELSON L.R. and HODGE D.O.: Continued endothelial cell loss ten years after lens implantation. Ophthalmology, 101: , DEJACO-RUHSWURM I., SCHOLZ U., PIEH S., et al.: Long-term endothelial changes in phakic eyes with posterior chamber intraocular lenses. Journal of Cataract and Refractive Surgery September (Vol. 28, Issue 9, Pages ), BOURNE W.M., NELSON L.R. and HODGE D.O.: Continued endothelial cell loss ten years after lens implantation. Ophthalmology, 101: , RAO G.N., STEVENS R.E., HARRIS J.K. & AQUAVEL- LA J.V.: Longterm changes in corneal endothelium following intraocular lens implantation. Ophthalmology, 88: ; discussion by HM Leibowitz, 379, Oxford Cataract Treatment and Evaluation Team (OCTET). Long-term corneal endothelial cell loss after cataract surgery; results of a randomized controlled trial. Arch. Ophthalmol., 104: , PÉREZ-SANTONJA J.J., IRADIER M.T., BEN ıtez DEL CASTILLO J.M., et al.: Chronic subclinical inflammation in phakic eyes with intraocular lenses to correct myopia. J. Cataract Refract Surg., 22: , 1996.