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

Figure 17.7: Intraocular pressure in the postoperative follow-up

eye, a postoperative wound leak with low IOP (4-8 mmHg) and flattening of the anterior chamber occurred requiring a suture closure of the corneoscleral tunnel incision. In a left hyperopic eye with an implant torus of 3 D, a reposition of the lens was performed after one week because of a deviation from target axis (175°) of about 15°.

No potentially sight-threatening complications such as iris prolapse, iris atrophy, touch of the anterior lenticular capsule, persistent corneal edema, pupillary block, cataract formation, retinal detachment, or endophthalmitis were observed during the one year postoperative period.

QUESTIONNAIRE

Three months postoperatively, every patient filled out a questionnaire. The mean self estimated satisfaction (1 = not satisfied, 10 = very satisfied) with the outcome after surgery was 9.6 ± 1.1 (min: 6, max 10).

DISCUSSION

In this study, we prospectively evaluated the safety, predictability and efficacy of the new toric ris-claw-TPIOL in 31 eyes of 17 patients for up to 1 year postoperatively in our institution. Special attention was given to irisfixated specific complications such as endothelial cell loss and intraocular pressure. Our data demonstrate that this new toric phakic IOL is an effective surgical option to correct high ametropia and astigmatism in one procedure. An improvement of best-corrected visual acuity from 20/32 preoperatively to 20/25 after six

months was observed in both groups. In group M 18 eyes (83%) had an UCVA of 20/40, or better, 13 eyes (60%) of 20/32 or better. In group H 7 eyes (73%) had an UCVA of 20/40 or better, 6 (62%) of 20/32 or better. 91 percent of myopic eyes and 100 percent of hyperopic eyes were within ± 1.0 D of desired refraction. Our results resemble the previous published data of the European multicenterstudy1 of the toric iris-claw-lens.

Surgical outcome results with the spherical iris-claw lens are similar to ours: Landesz et al3 reported that in correcting high myopia with the Artisan TPIOL, postoperative residual refraction was within ± 1D of emmetropia in 67 percent (45) of eyes after two to three years of follow-up.22 Budo et al5 reported a postoperative refraction within ± 1 D of emmetropia in 78 percent (196) of eyes. The astigmatic correction can be performed in 0.5 D steps, which contributes to good refractive outcomes. A mean astigmatic reduction from –3.57 D preoperative to –0.5 D postoperative in the myopic group and –3.5 D preoperative to –0.56 D postoperative was observed during follow-up.

There are a variety of surgical procedures to treat ametropia and astigmatism. Surgical options for correcting astigmatism include corneal or limbal relaxing incisions, PRK and LASIK. A continuing problem with these surgeries is the variability of the biological tissue, which decreases the predictability of the patient’s final refraction. LASIK, as the current leading refractive technique to correct refractive errors, has been successfully performed, but the results in high myopia with astigmatism are limited. In addition, the amount of tissue ablation is limited in order to maintain a sufficient stromal bed to prevent iatrogenic keratectasia. Moreover, keratorefractive procedures irreversibly change the corneal curvature, which may change optical quality and induce optical aberrations.1, 3, 10, 11

Another surgical option is clear lens extraction. This procedure is still controversial due to an increased risk of retinal detachment in high myopes. The incidence of retinal detachments varies between 1.9 percent12,13 and 8.1 percent,14 depending on the study, and remains a concern for this procedure. Another disadvantage, especially for younger patients, is the concomitant loss of accommodation.

Correcting high ametropia with phakic IOLs offers predictable and stable refractive results, especially for patients with moderate and high myopia.3,15,16 In addition, compared to keratorefractive options, predictability is more accurate with phakic IOLs, especially for myopia of more than -10.00 D.17,18

However, potential risks and complications associated with iris-fixated-IOLs must be taken into consideration. Highly trained surgeons who are familiar with the special implantation technique are crucial for reducing intraand postoperative complications. Surgically related compli-cations, such as transient corneal edema from touching the endothelium, transient elevation of intraocular pressure (e.g. insufficient removal of viscoelastics), or hyphema, can be minimized by accurate surgical training.5

Other reported complications related to the iris-fixated lens include lens de-centration, retinal complications, Urrets/Zavalia syndrome, lens opacity, and ischemic optic neuropathy.1,3 Postoperative complications such as glare/ halos are commonly related to poor centration of the lens during surgery, large iridectomy, or pupils being larger under scotopic conditions than the optic diameter of the IOL. In 1997, a new model with a 6.0 mm optic was introduced to address potential photic phenomena in patients with larger pupils. This model is more forgiving if the lens is somewhat decentered. On the other hand, a 6.3 mm primary incision is needed for this design. In the near future, foldable iris-claw-TPIOLs will reduce the incision size issue.5

Progressive endothelial cell loss, uveitis, pigment dispersion and the development of glaucoma are still major concerns.3 Therefore, an intraoperative iridectomy or preoperative iridotomy is highly recommended, as well as an annual examination that includes endothelial photo-graphy.10 Risk factors for progressive endothelial cell loss are age, flat anterior chamber depth (the original anterior chamber depth is reduced by 30 percent after implantation), and stronger IOL power (because the IOL is thicker).19

Menezo et al20 reported a mean endothelial loss of 3.9 percent at six months, 6.6 percent at one year, 9.2 percent at two years, 11.7 percent at three years, and 13.4 percent at four years after implantation of a Worst-

Fechner TPIOL. Also using the Worst-Fechner TPIOL, Perez-Santonja21 et al described an endothelial cell loss of 7.3 percent at three months, 10.6 percent at six months, 13.0 percent at one year, and 17.6 percent at two years after implantation.

In our population, the mean preoperative endothelial cell count was 3221 ± 405 cells/mm.2 The endothelial cell loss was 1.7 percent (1 week), 4.9 percent (one month), 3.7 percent (three months), 4.5 percent (six months) and 4.9 percent (one year) after surgery compared to preoperative values.

In our one year follow-up, the iris-claw TPIOL was an effective, safe and predictable additional option for eyes with high ametropia and astigmatism. The advantage of this option is the preservation of the corneal curvature and accommodation. However, potential risks19 must be evaluated before implanting this lens. Exclusion criteria such as reduced endothelial cell count or anterior chamber depth less than 2.9 mm should be respected for optimal surgical outcomes. Certainly, a longer followup, especially in regard to endothelial cell loss is mandatory for a final assessment. Our study reveals satisfactory refractive results. There were no major complications, although follow-up time and series numbers were limited.

REFERENCES

1.Dick HB, Alio J, Bianchetti M, Budo C, Christiaans BJ, ElDanasoury MA, Guell JL, Krumeich J, Landesz M, Loureiro F, Luyten GP, Marinho A, Rahhal MS, Schwenn O, Spirig R, Thomann U, Venter J. Toric phakic intraocular lens: European multicenter study. Ophthalmology 2003; 110:150-62.

2.Landesz M, van Rij G, Luyten G. Iris-claw phakic intraocular lens for high myopia. J Refract Surg 2000;17:634-40.

3.Landesz M, Worst JG, van Rij G. Long-term results of correction of high myopia with an iris claw phakic intraocular lens. J Refract Surg 2000;16:310-16.

4.Perez-Santonja JJ, Bueno JL, Zato MA. Surgical correction of high myopia in phakic eyes with Worst-Fechner myopia intraocular lenses. J Refract Surg 1997;13:268-81.

5.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;26:1163-71.

6.Menezo JL, Avino JA, Cisneros A, Rodriguez-Salvador V, Martinez-Costa R. Iris claw phakic intraocular lens for high myopia. J Refract Surg 1997;13:545-55.

7.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;71:630-42.

8.Van der Heijde GL, Rouwen AJ. Optics of intraocular lenses and refractive keratoplasty. Curr Opin Ophthalmol 1990;1:64-68.

9.Koch DD, Kohnen T, Obstbaum SA, Rosen ES. Format for reporting refractive surgical data. J Cataract Refract Surg 1998;24:285-87.

10.Landesz M, Worst JG, Siertsema JV, van Rij G. Correction of high myopia with the Worst myopia claw intraocular lens. J Refract Surg 1995;11:16-25.

11.Seiler T, Koufala K, Richter G. Iatrogenic keratectasia after laser in situ keratomileusis. J Refract Surg 1998;14:31217.

12.Colin J, Robinet A, Cochener B.Retinal detachment after clear lens extraction for high myopia: seven-year followup. Ophthalmology. 1999;106:2281-84.

13.Colin J, Robinet A. Retinal detachment after clear lens extraction in 41 eyes with high axial myopia. Retina. 1997;17:78-79.

14.Barraquer C, Cavelier C, Mejia LF. Incidence of retinal detachment following clear-lens extraction in myopic patients. Retrospective analysis. Arch Ophthalmol 1994;112:33639.

15.Alio JL, de la Hoz F, Perez-Santonja JJ, Ruiz-Moreno JM, Quesada JA. Phakic anterior chamber lenses for the

correction of myopia: a 7-year cumulative analysis of complications in 263 cases. Ophthalmology 1999; 106:458-66.

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

17.Knorz MC, Liermann A, Seiberth V, Steiner H, Wiesinger B. Laser in situ keratomileusis to correct myopia of –6.00 to –29.00 diopters. J Refract Surg 1996;12:575-84.

18.Knorz MC, Wiesinger B, Liermann A, Seiberth V, Liesenhoff H. Laser in situ keratomileusis for moderate and high myopia and myopic astigmatism. Ophthalmology 1998;105:93240.

19.Pop M, Mansour M, Payette Y. Ultrasound biomicroscopy of the iris-claw phakic intraocular lens for high myopia. J Refract Surg 1999;15:632-35.

20.Menezo JL, Cisneros AL, Rodriguez-Salvador V. Endothelial study of iris-claw phakic lens: four year follow-up. J Cataract Refract Surg 1998;24:1039-49.

21.Perez-Santonja JJ, Iradier MT, Sanz-Iglesias L, Serrano JM, Zato MA. Endothelial changes in phakic eyes with anterior chamber intraocular lenses to correct high myopia. J Cataract Refract Surg 1996;22:1017-22.

22.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;15:529-37.

23.Holladay JT, Moran JR, Kezirian GM. Analysis of aggregate surgically induced refractive change, prediction error, and intraocular astigmatism. J Cataract Refract Surg 2001; 27:61-79.

Antonio Marinho

Ramiro Salgado (Portugal)

INTRODUCTION

Phakic IOLs have been used in clinical practice in refractive surgery for 15 years. They have earned an important place in this field, because all of them have shown great accuracy and predictability in all the refractive errors, even in very high ametropias, as well as a stable result from day 1, as this method of correction is not dependant on tissue healing. All of the types of phakic IOLs have shown increase in best corrected visual acuity and the quality of vision obtained has satisfied more than 90 percent of people implanted.1

However the presence of the IOL inside the eye has been associated with complications specific to the type of phakic IOLs involved. Some of these complications have led to changes in design of some lenses and to discontinuing of others.

In this chapter I will try to describe the most frequent complications associated with implantation of phakic IOLs. The complications related to the surgery itself will be disregarded here, as these may be related to surgical skills and not to the implant itself. I will focus on the problems due to the presence of the IOL inside the eye in the short, medium and long terms.

TYPES OF PHAKIC IOLs

Phakic IOLs can be divided in 3 groups:

a.Angle supported anterior chamber phakic IOLs

b.Iris supported anterior chamber phakic IOLs

c.Posterior chamber phakic IOLs

Figure 18.1: Nuvita IOL

Angle Supported Anterior Chamber Phakic

IOLs

a.PMMA Kelman type implants like the Baikoff designed ZB and ZB5 M (DomilensFrance) as well as the Nuvita (Bausch and Lomb) (Fig. 18.1) and the Phakic 6 (OII).

All these IOLs have in common the material (PMMA) and the design (Kelman type with 4 points for angle support). Their differences regard mainly to the optical zone size (4.0 mm in the ZB to 6.0 mm in the Phakic 6) the vault of the lens (very high in the ZB) and subtle changes in the design of the haptics.

b.Semiflexible anterior chamber angle supported phakic IOLs like Vivarte (CIBA Vision)(Fig. 18.2). This implant has a foldable (soft) optic and PMMA haptics. There are 3 points for support and the very tip of the haptics (where they touch the angle is also soft).

c.New totally soft anterior chamber phakic IOL like the AcrySof (Alcon) (Fig. 18.3) or the Icare (Corneal) have 4 points of fixation. However, they are still in an investigative stage and its complications

will not be described.

All these IOLs are dependant on the size of anterior chamber, that is, we need an IOL with a size matching the size of the anterior chamber. As the correct size of the anterior chamber is very hard to determine despite improvements in technology (UBM systems), we

Figure 18.2: Vivarte IOL

Figure 18.3: AcrySof IOL

normally have to rely on the very rough white to white measurement. There are several ways to measure the white to white, such as callipers, Holladay devices or Orbscan. Different IOLs add 0.5 to 1.5 mm to this white to white measurement in order to obtain the correct

size. However as stated above this is only right in 80 percent of the cases. As we will see later this wrong sizing of the IOLs is the main source of complications with this type of phakic IOLs.

Iris Supported Anterior Chamber Phakic IOLs

This group includes the Artisan and its foldable version: the Artiflex.

The great advantage of these type of IOLs is that they are size independent, that is: “one size fits all”. These IOLs are supported by the mid-periphery of the iris (not interfering with normal pupil dilation), do not touch the angle and are at a safe distance from the cornea and the natural lens.

Posterior Chamber Phakic IOLs

a.Sulcus fixated posterior chamber phakic IOLs as the ICL (Staar). This IOL is a foldable IOL made of collamer that sits on the cilliary sulcus. The sizing of this lens is critical, because if the lens is short it will sit on the natural lens without a healthy vault (space between the lens and the natural lens). If on the other hand the IOL is too long it will push the iris forward reducing the angle width. Again, like in the anterior chamber angle supported phakic IOLs it is difficult to extrapolate the sulcus dimensions from the white to white measure-ment.

b.Posterior chamber phakic IOLs “floating” in the posterior chamber like the PRL (CIBA Vision) (Fig. 18.4). This posterior chamber silicone phakic IOL is supposed to “float” in the aquous humour. This has the advantage of keeping this IOL away from size considerations as “one size fits all”.

COMPLICATIONS OF PHAKIC IOLs

Complications of Anterior Chamber Anglesupported Phakic IOLs

The complications of angle supported phakic IOLs can be divided in the following topics:

a.Endothelial complications

b.Sizerelated complications

c.Quality of vision issues

d.Other problems

Endothelial Complications

Everytime anterior chamber IOLs are evaluated, the subject of endothelial complications arise. This is mostly due to previous experience with older designs of aphakic IOLs, that led to many cases of endothelial decompensation, leading to the need of corneal grafts.

Concerning phakic IOLs, only the first model of Baikoff (ZB) was damaging to the corneal endothelium. This was due not to the haptic rigidity or design (like in the aphakic IOLs) but to the high vault of this IOL, that led the IOL to be very close to the mid periphery of the cornea. We know today that a minimum of 1.5 mm between the IOL and the corneal endothelium is needed to long term safety. This explains the damage to the endothelium in most cases with this IOL2,3 leading, if not explanted early to endothelial decompensation.

Modifying the design in the later generations, these IOLs became very safe to the corneal endothelium. Personal experience of 600 eyes implanted of ZB 5M from 1990 to 1996 and 140 eyes implanted with Nuvita from 1997 to 2000 showed a healthy endothelium without pleomorfism and polymegatism and only a physiological decrease in endothelial cell population. Similar results are published in the literature.4

Size-related Complications

As was stated above angle supported anterior chamber phakic IOLs need to have the same size of the anterior chamber in order to fit there exactly without causing damage to the ocular tissues. This would create no problem if we could easily measure the dimensions of the anterior chamber in vivo. In practice it is very difficult to do so. At present this is only possible with very sophisticated (and expensive) UBM devices, that surely are very interesting for investigative use, but not for routine clinical practice.

Most surgeons use the indirect method of “white to white”and then add 0.5 to 1.5 mm in order to choose the IOL.

In our personal study with ZB 5M and Nuvita a factor of 1.0 mm was added to the “white to white” measured

Figure 18.4: PRL IOL

with callipers. We found that about 80 percent of the implanted were the right size.

If an anterior chamber angle-supported phakic IOL is too short, the IOL will rotate in the anterior chamber (Fig. 18.5) causing important glare and potentially damaging the endothelium. This was a rare event in our Nuvita series, where we added 1mm to the white to white, but became common in the Vivarte series (20%), where our surgical protocol added only 0.5 mm.

A more frequent and serious complication is the pupil ovalisation. This situation occurred in 30 percent of ZB5M cases and 15 percent of Nuvita and is rare (although described) with Vivarte. This phenomenon seems to be related with too long IOLs. The rigidity and the shape of the haptics creating a more uniform pressure in the angle may contribute for the reduced rate of this

complication in newer models. Nevertheless pupil ovalisation has not yet been eradicated in this type of phakic IOLs.

Pupil distortion starts after 12 to 18 months of implantation, the pupil showing ovalisation, the longer axis being always the axis of the IOL. At first if ovalisation is mild (Fig. 18.6) there is only a cosmetic effect. Some cases, however, progress to a situation where part of the papillary area is outside of the optic (Fig. 18.7) causing important glare. In this cases there are usually areas of iris atrophy (mainly where there is haptic pressure) that can lead to iatrogenic polyopia.

The etiology of pupil ovalisation and iris atrophy is not clear. The most accepted theory states that the pressure of the haptics (of a too long IOL) on the iris root causes ischemia with consequent tissue atrophy.

The management of these size related complications is controversial. Some advocate that pupil ovalisation is only a cosmetic defect, as the visual acuity is not involved. However, if there is any amount of iris suffering, we always explant these IOLs. If the IOL is explanted early, the pupil may return to the original round shape, however in most advanced cases the pupil will retain the oval shape but the process of ovalisation and iris atrophy will stop.

Figure 18.7: Important pupil ovalisation with iris atrophy

Quality of Vision Issues

Quality of vision has always been a concern in all types of refractive surgery. It easy to evaluate subjectively, as most patients describe “how they see”, but it is very difficult to quantify because the sophisticated tests sometimes used do not correlate well with the conditions of normal life. Although, we have done in the past some studies with contrast sensitivity and mesopic vision, we will not discuss them here and the evaluations of the IOLs will be based on subjective evaluation by the patient.

Generally speaking, patients implanted with anterior chamber angle-supported phakic IOLs refer a very good quality of vision, far superior than that they had with glasses or contact lenses. The only frequent complain is some amount of halos and glare.5

Taking the all group of IOLs about 20 percent of patients refer glare at night (I say “refer” and not “complain “ because most patients are not unhappy about that), but if asked this number increase to 80 percent... This means that glare is indeed there, but is well tolerated. Of course the amount of glare depends on the pupil size and the diameter of the optic zone of the IOL. This explains why glare was more a concern in the early generations of IOLs with smaller optics like the ZB than in the present Phakic 6. This also teaches us to be careful when operating patients with large pupils.

Other Problems

Anterior chamber angle-supported phakic IOLs are not associated with chronic intraocular inflammation, ocular high pressure or cataracts.

It is important to notice that there is never any synechiae between the footplates and the haptics, as was seen in older models of aphakic anterior chamber phakic IOLs. In fact, it is very easy to explant one of these lenses up to 10 years after implantation.

Although there is permanent contact with the angle no glaucoma cases have been associated with these IOLs.

Nuclear cataracts have been observed in these patients. The cataracts usually develop around 50 years of age and have the usual pattern of nuclear cataracts in myopic non-operated patients. However, implanted patients have a tendency to develop cataracts somewhat younger than non-implanted ones. This is believed to be due, not to the implant itself, but to the opening of anterior chamber during surgery and to the alteration of the aquous flow due to the iridectomy.

Complications of Iris-Supported Phakic IOLs

Long-term Complications due to Poor Surgical Technique

Unlike other phakic IOLs, most of Artisan problems arise not from the lens itself, but are consequences of poor surgical technique. One frequent complication is the loosing of the IOL from the iris. This can occur spontaneously or after minor trauma. However, this complication is always the consequence of the so called “weak grasp”, that is insufficient amount iris tissue grasped in the claw. This complication is fairly common during the learning curve, but disappears when an experienced surgeon performs good surgery. Also, other minor complications such as decentration are due to surgery and not to the IOL.

Complications Related with the IOL

There are in fact very few complications related to Artisan/Artiflex. In a few eyes some pigment deposits

have been observed a few weeks after surgery. In most cases these cells do not interfere with visual acuity and go away spontaneously. In more rare instances, we observe a mild anterior uveitis during the first weeks after surgery. These cases respond well to steroid and mydriatic treatment with full recovery in all cases. No chronic intraocular inflammation has been observed and never explantation of Artisan/Artiflex has been needed due to inflammation.

Complications of Posterior Chamber Phakic IOLs

Posterior chamber phakic IOLs are placed in a very thin space (the posterior chamber) between the natural lens and the iris. The relationship of the IOL with these two structures explains the complications of these IOLs. Being further away from the corneal endothelium, no endothelial problems have been raised with this type of phakic IOLs.

Cataracts have always been the main concern. Cataracts related to posterior chamber phakic IOLs are typically anterior subcapsular opacities (Fig. 18.8). These cataracts can occur in two different ways. Cataracts can be the outcome of a traumatic surgical technique or more commonly related to the presence of the phakic IOL inside the eye.

When surgically induced the cataracts are present immediately after surgery and usually do not progress with time. On the other hand the phakic IOLs-induced cataracts typically start between 12 and 18 months after surgery with some anterior sucapsular opacities that at first do not interfere significantly with visual acuity, progressing later causing sometimes the need of cataract surgery.

The reason why these cataracts develop is not well established, although it is widely believed that depends mainly on the space (vault) between the IOL and the natural lens. When this space is too narrow or even nonexistent (the IOL touching the natural lens) the aquous humour cannot flow freely around the lens, causing changes in metabolism responsible for the opacities (Figs

Figure 18.8: Anterior subcapsular opacity with ICL

18.9 and 18.10). This theory of vault-related cataracts has been established while studying different generations of ICL.

As seen in Table 18.1 the mean vault of V2 generation of ICL is much smaller than that of the present V4. In our personal study of ICL we found 40 percent of eyes implanted with V2 with some form of opacity at 2 years follow-up compared to only 2 percent cataract rate at the same follow-up. In this study it is proved that a change in design (increase of vault) reduced dramatically this complication. The main problem when choosing an ICL is how do we get the right vault. The ICL is a posterior chamber phakic IOL, that sits on the cilliary sulcus. As was pointed in relation to angle-supported phakic IOLs we donot have the means to measure directly the cilliary sulcus. Again we rely on the very imprecise white to white measurement. If we choose a short ICL there will be

Figure 18.9: Scheimpflug image showing ICL with good vault

Figure 18.10: Scheimpflug image showing

ICL without vault

Table 18.1: ICL mean vault with different models

a reduced vault with all the known consequences. If on the other hand the ICL is too long we finish with excessive vault and other complications described below.

Another issue related with vault of the ICL is the socalled “loss of vault”. This can occur some months after surgery when the ICL looses its “memory” or more often in the long term when the natural lens grow reducing the vault. In any of these cases the risk of developing cataracts is high. Any time a reduced (less than 0.15 mm) vault is observed the ICL should be explanted.

Although it is widely believed that a sufficient vault is needed to avoid the development of cataracts, it is true that there some eyes implanted for 6 or 7 years without vault, and with a totally clear lens. Other factors, such as age and myopia higher than –15.00 may also

play a role in the pathogenesis of cataracts in ICL.6,7 The other posterior chamber phakic IOL currently used is the PRL. The PRL does not sit on the cilliary sulcus as the ICL, but it supposed to “float” in the aquous between the lens and the iris. Being so, it is size independent, that is “one size fits all”. Although the experience and follow-up are shorter than in the ICL,

cataracts do not seem to be associated with PRL. Posterior chamber phakic IOLs (if well fit) reduce the

width of the angle by 30 percent, because they push the iris forward. This causes some iris pigment dispersion, but for the time being no permanent ocular high pressure cases have been described. However, if the implanted IOL is too long and an excessive vault is present, severe high ocular pressure may arise.

REFERENCES

1.Landesz M, Bouman T, Worst J: Evaluation of psychosocial findings and satisfaction among patients with a Worst Myopia Claw Lens. Chapter 5 Doctoral Thesis University of Groningen The Netherlands. The only scientific study on patient satisfaction with phakic IOLs.

2.Mimouni F, Colin J, Koffi V, Bonnet P. Damage to the corneal endothelium from anterior chamber intraocular lenses in phakic eyes. Refractive Corneal Surgery 1991;7:277-81.

3.Saragoussi JJ, Cotinat J, Renard J, Savoldelli M,Abenhaim A, Pouliquen Y: Damage to the corneal endothelium by minus power anterior chamber intraocular lenses. Refractive Corneal Surgery 1991;7:282-85.

4.Baikoff G, Arne JL, Bokobza Y, Colin J, George J, Lagoutte F, Lesure P, Montard M, Saragoussi J, Secheyron P: Anglefixated Anterior Chamber Phakic Intraocular Lens for Myopia of –7 to –19 Diopters. Journal of Refractive Surgery Vol 14 May/June 1998;282-93.

5.Marinho A: New generation Phakic IOL implant for myopia provides good vision quality. Euro Times 1998;3(6):p.26.

6.Zaldivar R, Davidorf JM, Oscherow S: Posterior Chamber phakic IOL for myopia of –8 to –19 diopters. Journal of Refractive Surgery 1998;14:294-305.

7.Davidorf JM, Zaldivar R, Oscherow S: Posterior chamber phakic intraocular lens for hyperopia of +4 to +11 diopters. Journal of Refractive Surgery 1998;14:306-11.