Ординатура / Офтальмология / Английские материалы / Phakic Intraocular Lenses_Hardten, Lindstrom, Davis_2004

INTRODUCTION

The 1960s saw the beginning of the development of implants for phakic eyes. The European pioneers (Barraquer, Choyce, Stampelli, etc) suggested the use of intraocular lenses to correct high myopia while preserving the crystalline lens. At the same time they began to correct aphakia with intraocular lenses (IOLs).

All of these attempts with phakic IOLs led to serious anatomical complications, so the techniques were put aside until 1985 to 1987 when, under the influence of Fyodorov, Fechner, and Baïkoff, they were once again put back on the agenda. Each surgeon developed a different type of fixation: posterior chamber, iris fixated, and angle supported.

Back in 1986, angle-supported anterior chamber implants were already being developed by modifying the characteristics of Kelman’s multiflex lens for the correction of aphakia (Figures 15-1 to 15-4).

Between 1987 and 1989, the first trials with the ZB 5M (Bausch & Lomb Surgical, Rochester, NY) implant gave excellent optical results, but unfortunately, a relatively high endothelial cell loss was noted during the first 18 months.1-11 This lead to a modification of the lens vaulting in order to downsize it and reduce the endothelial damage at the time of implantation.

Starting in 1990, the ZB 5M implant and then its successor, the NuVita implant (Bausch & Lomb Surgical, Rochester, NY), adopted a profile that maintained a minimum 1.5-mm clearance between corneal endothelium and the lens edge for the highest powered lenses (ie, the lens-

es with the thickest edges). By adhering to this secure profile, no serious endothelial cell loss other than the usual physiological loss has been observed since 1990. The only complications related to this lens are pupillary ovalization, most of which is due to oversizing of the lens.

These type of implants have shown that the induced complications such as cataracts, uveitis, glaucoma, and corneal decompensation were extremely rare.

INDICATIONS

Today, the indications are directly linked to the limits of corneal surgery. For the time being, photorefractive keratectomy (PRK) and laser in-situ keratomileusis (LASIK) predominate the indications for refractive surgery. However, the optical quality is less satisfactory in higher corrections. Moreover, the scatter of the results means frequent enhancements.

The creation of an interface during LASIK can bring about a loss in contrast sensitivity that will penalize the optical quality despite a satisfactory anatomical and topographic result. Lastly, LASIK is not without optical or anatomical complications (eg, diplopia, loss of visual acuity, loss of contrast sensitivity, epithelial ingrowth, flap shifting, infections).

Nowadays, it can be said that the range for LASIK is between +3 diopters (D) and -10 D. High myopes and high hyperopes beyond these limits obtain more satisfactory results with refractive implants. In his everyday practice, the author systematically proposes a refractive implant to patients with over -10 D and for patients

between -8 D and -10 D, he gives them the choice. Over time, new indications have appeared and all suspect corneas with subtle topographical abnormalities must be eliminated because it is in this group that post-LASIK corneal ectasia has been observed.

Therefore, the author systematically proposes today a refractive implant if at least one of the following conditions is met:

•Corneal thickness less than 500 µm

•Asymmetric astigmatism

•Irregular astigmatism

•Decentration of the corneal apex

•Forme fruste keratoconus

This means that even with a slight myopia of, for example, -2 D, if one of the aforementioned abnormalities exists, the author systematically suggests either a refractive implant or nothing. While waiting for a transplant, a refractive implant can be proposed to a patient who has started to develop keratoconus. The quality of the correction is almost identical to that of a contact lens, which is typically poorly tolerated on a clinical basis.

Refractive corneal surgery presents additional limits. The author believes that it is contraindicated to suggest a PRK or LASIK for an enhancement if, after radial keratotomy, a decline of the effect and a return toward myopia or a hyperopic shift is observed. Indeed, the evolution of a refractive disorder is proof of the instability of the cornea and today, it seems totally illogical to further damage an unstable cornea with a cut of which the long-term effects are still unknown. This is why the correction of progressive refractive abnormalities following radial keratotomy is an excellent indication for refractive implants. Moreover, if the refractive abnormalities continue to progress, it is relatively simple to

Figure 15-4. ZB 5M implant. It went into production in 1990.

exchange the implant, especially as these former myopic eyes generally have a very deep anterior chamber.

Patients suffering from dry eyes, a condition that deteriorates after corneal surgery, such as PRK or LASIK, are also excellent candidates for refractive implants.

DESCRIPTION OF THE

FOLDABLE ANGLE-SUPPORTED

ANTERIOR CHAMBER PHAKIC

IMPLANT (GBR/VIVARTE)

The interest of angle-supported anterior chamber implants is their simplicity. The lens is perfectly visible in the anterior segment, and any abnormality is easy to visualize with a slit lamp. Gonioscopy will show the effects the footplates have on the iridocorneal angle. A correctly designed lens does not come into contact with the endothelium and respects the iris and the crystalline lens. Should a problem arise, it is easy to remove or change the lens. These angle-supported anterior chamber lenses are of such interest that nine companies are working in that field

Figure 15-5. GBR/Vivarte implant.

(Alcon, AMO, Bausch & Lomb Surgical, CIBA Vision, IOLTech, Morcher, O.I.I., Thinoptx, Tekia). It is perfectly logical to insert an implant in the anterior chamber because that is where the most space is available. It is important to respect rigorous safety profiles in order to keep away from fragile structures, such as the corneal endothelium.

Today, anterior chamber implants with safe designs no longer cause anterior segment complications (ie, corneal decompensation, cataract, glaucoma, uveitis). The only problem noted is a small number of pupillary ovalizations often due to oversizing of the implant. It is, therefore, imperative to evaluate the diameter of the anterior segment before choosing the implant and to use implants with well-designed footplates.

It is also important to have a stable implant in the anterior chamber to avoid the problem of unwanted lens mobility and energy dispersion as was observed with Binkhorst 4 loops implants inserted after intracapsular cataract extraction (ICCE). It is, therefore, necessary to have a sufficiently rigid stable haptic with a soft optic as the risk with a soft haptic is an unstable lens.

The profile of the GBR/Vivarte lens (IOLTechnologie, La Rochelle, France/CIBA Vision, Duluth, Ga) was designed to combine a stable haptic made of a material such as polymethylmethacrylate (PMMA) together with a soft optic made of an acrylic type of material (Figure 15- 5). The approximate “2” shape of the haptic and the three footplates enable the haptic to be inserted easily into the anterior chamber without having to twist or manipulate it in a complicated way. If a Kelman-type implant with four support points had been chosen, there would have been difficulties during the unfolding of the haptic in the anterior chamber. The optic of the GBR/Vivarte lens is round with a 5.5-mm diameter, which makes it possible to reasonably reduce halos and edge effects. Concerning high ametropias, there is no technique (PRK, LASIK, or

Figure 15-6. Measure of the anterior chamber diameter with the plastic sizer.

implants) that will completely eliminate nocturnal halos no matter what the diameter of the pupil. This is only relatively important, as most high myopes normally suffered from nocturnal vision discomfort before surgery whether they wore glasses or contact lenses.

MEASUREMENT OF THE

INTERNAL DIAMETER

OF THE ANTERIOR CHAMBER

An angle-supported anterior chamber implant will be successfully tolerated if it is correctly adapted to the diameter of the anterior chamber. Up until now, the techniques for evaluating the diameter of the anterior chamber were based on indirect evaluations of the outside aspect of the ocular structures: white-to-white measurement with a compass, a photographic white-to-white evaluation, etc. These measures were only approximate and required adding an adaptation factor that was different from one surgeon to the other or even from one eye to the next. Therefore, we had the opportunity to evaluate different techniques that will likely evolve over the next few months or years.

•Measurement with a plastic sizer at the time of surgery

•Preoperative automatic optical measurement based on optical or ultrasonic principles

Manual Sizer

The manual sizer is a small plastic ruler that is inserted into the anterior chamber to measure the internal diameter (Figure 15-6). The tip rests on the angle opposite the incision, and the graduations in the middle of this ruler allow an

154 Chapter 15

Figure 15-7. Evaluation of white-to-white diameter measured with topography.

estimate of their projection on the center of the anterior segment. The author tried to mark the corneal center and study its projection on the center of the ruler, but the mark was very approximate and the estimate subject to parallax errors. The constant anatomic reference nearest to the anatomical center of the anterior segment seems to be the middle of the temporal margin of the pupil. Indeed, the pupil is practically always decentered toward the nose, and the temporal edge is the fixed point nearest to the geometric center of the cornea. The plastic sizer must be used according to the vertical meridian, 6:00 to 12:00, because the pupil is centered on this meridian; however, on the horizontal meridian, the pupil is decentered toward the nose, which means that the sizer must not be used on the 3:00 to 9:00 axis.

The plastic sizer is inserted at the beginning of surgery with regards to the vertical meridian in an anterior chamber reformed with viscoelastic. The extremity of the sizer is pushed into the inferior angle without applying too much pressure, which would falsely elongate the measurement and lead to insertion of a lens that is too long. This would cause the iridocorneal angle to move backward and create pupillary ovalization. It is important to check that the pupil remains perfectly round at that moment. The iris plane must be perpendicular to the microscope’s axis to reduce parallax errors. Finally, the graduations are read opposite the center of the pupil’s temporal edge. If in doubt, it is preferable to choose the smaller size to avoid oversizing of the lens, leading to pupillary ovalization.

This technique has the disadvantage of being done intraoperatively and means that the surgeon must have at his or her disposal several lenses of identical power but of different diameters. It is, therefore, of the utmost importance to focus on a preoperative measuring technique for

Figure 15-8. Evaluation of internal diameter of the anterior chamber with the IOLTech LED sizer.

choosing the right lens while avoiding stocks of lenses that are difficult to manage.

Use of Preoperative Photos of the

Anterior Segment With Topographs

Corneal topographs give calibrated photos of the anterior segment. With a bit of experience, it is possible to have a correct measurement of the internal horizontal anterior chamber diameter by taking into consideration the distance between the external limits of the limbic vessels from their nasal side to their temporal side rather than clear cornea to clear cornea. The projection of the external border of the limbic arch corresponds more or less to the sinus of the iridocorneal angle. In general, three measurements are taken according to the corneal diameter apparent in the pupillary area horizontally and slightly oblique. The average of these three measurements gives us an evaluation very close to the internal diameter of the anterior chamber. As the implants are available on a scale that is in 0.5-mm increments, the implant with the nearest corresponding diameter will be used. For instance, in Figure 15-7, the implant chosen will be one with a 12-mm diameter for a diameter of 11.9 mm.

The LED Sizer

The light emitting diode (LED) sizer (IOLTech) retroilluminates the anterior segment. If the anterior segment is illuminated laterally, the cornea is totally transparent, the sclera behind the uveal tissue insertion is opaque, and the corneoscleral junction is translucent (Figure 15-8). A laterally illuminating probe is applied against the eye and the anterior segment is photographed. The image is interpreted by a computer that analyzes different diameters at the junction between the translucent zone and the opaque zone. Theoretically, this opaque-translucent junction is the exact projection of the angular sinus as it corresponds to the adhesion of the iris root to the sclera.

This process is actually under development and should be available within the next few months.

Figure 15-9. Profile of a presbyopic implant on a phakic eye (UBM Artemis Ultralink).

Figure 15-10. Profile of anterior segment measured with the AC OCT (courtesy of Carl Zeiss Meditec).

Ultra-High Frequency Scanner Study

Ultra-high frequency scanners (over 50 MHz) give a very good quality image of the anterior chamber. One of the leaders in this new generation of machines is the Artemis Ultralink (Ultralink LLC, St. Petersburg, Fla), which the author has been able to use. The process of testing is fairly lengthy and the scan is done directly through a water bath. The images are of excellent quality, but to date, the program does not yet allow for a choice in corneal diameter. We are still at the point where the estimation of the largest diameter is left to the subjectivity of the surgeon.

The advantages over the previous generation of ultrasound biomicroscopy units is the capacity to produce a one-shot image of the anterior chamber, thus avoiding errors due to reconstructing an image from several different shots. It is, therefore, very easy to evaluate the different biometric data of the anterior segment: AC depth, corneal thickness, distance of the implant from the cornea, safety distance between the edge of the implant and the endothelium and to answer the question—internal diameter of the anterior chamber in vivo and preoperatively. The equipment is not yet routinely available but should appear on the market within the next few months (Figure 15-9). The disadvantages of the equipment are mainly its size, the length of time needed for an examination, and the existence of a double water chamber in front of the cornea, making it necessary to balance the pressure of the water bath and the anterior chamber (as too much pressure in the water bath would crush the anterior chamber and modify its biometric data).

Optical Coherence Tomograph Scanner

The last device that might be the most promising is the Anterior Chamber Optical Coherence Tomograph Scanner (AC OCT, Zeiss Humphrey) (Figure 15-10).

This technique is derived from the optical coherence tomograph scanner developed for the posterior segment. A different wavelength is required, which means that the equipment for the posterior segment cannot be used for the anterior segment. With this technique, it is possible to

rapidly obtain an optical cut of the anterior segment without any contact, which avoids pressure and modifications of the biometric settings. It is still necessary to define correlation factors to improve the measurements and it is not always possible to visualize the ciliary body and the sulcus. However, in eyes with widely dilated irises, the images of the crystalline lens and the sulcus are better. Because of its simplicity, rapidity, and precision, this technique will certainly establish its supremacy as far as anterior chamber implants are concerned. The image definition is of excellent quality, and different factors or different biometrics data will be rapidly defined.

ANESTHESIA AND

SURGICAL TECHNIQUE

The surgeon and the patient can choose the type of anaesthesia: general, local/regional, or topical. The technique of topical anesthesia is perfectly feasible, as it is rapid and painless.

A miotic will be instilled preoperatively in order to protect the crystalline lens during surgery.

Incision

The first step is a corneal or corneoscleral incision. It can be done either on the vertical meridian, on the horizontal meridian, or on any other meridian in order to gently control any astigmatism. The less astigmatism-inducing incision is a posterior corneoscleral one on the temporal meridian (Figure 15-11A). If the incision is more anterior in clear cornea, then the astigmatic effect will be greater than a posterior corneoscleral incision. As the size of the incision is moderate, the effect on astigmatism will still typically be limited to between 0.5 and 1 D. Depending on where the incision is made, astigmatism is typically less than 1 D.

Steel or diamond blades can be used; the dimension of the incision for a high myopic eye is at most 3.2 mm, which allows insertion of the implant in a folded configuration. For a presbyopic implant, which is very thin, a 2.8- mm to 3-mm incision is sufficient.

156 Chapter 15

A B

C D

Figure 15-11. A. 3-mm corneal incision. B. Injection of viscous substance in the anterior chamber. C. Insertion of a soft implant in the anterior chamber. D. End of surgery aspect.

Viscoelastic

After a corneal incision, the anterior chamber is filled with a viscoelastic substance. Depending on habit, either a regular or a high viscous substance can be used (Figure 1511B).

Paracentesis

Two paracenteses are done on the axis perpendicular to the main incision. These paracenteses allow the implant to be manipulated at the end of surgery. We believe that they should be done systematically. Indeed, it is preferable to have two paracenteses that will not be needed rather than doing one at the end of surgery, which will be more difficult, when the eye has become soft.

Checking the Diameter

of the Anterior Chamber

This is done as described previously.

Folding the Implant

It is important to follow folding instructions because the simplicity of surgery depends on the quality of the folding. Folding is basically the only part that requires a little training beforehand. A folder and a pair of holding forceps were specially designed for the implant. The folding forceps are a sort of press in which the implant is placed. When the jaws of the press are closed, the optical part is folded into three parts, which allows it to be grasped by the inserting forceps. The operator has to get used to coordinating the opening of the press with the closing of the insertion forceps. Pressure on the folder is gently released and the optic is firmly grasped with the

forceps. Theoretically, the optic folded into three can be grasped, while the haptics remain free.

Inserting Into the Anterior Chamber

The knee of the inferior haptic (double haptic) is inserted first, then guided through the anterior chamber horizontally in front of the pupil (Figure 15-11C). Once the optic is correctly positioned in the anterior chamber, pressure on the optical part is released. The optic will unfold gently and the forceps are removed. If necessary, viscoelastic can be reinjected. Finally, the trailing haptic is gently pushed inside the anterior chamber.

Repositioning of the Haptics

At the end of surgery, it is very important to reposition the lower footplates by using the lateral paracentesis. The footplates are lifted forward slightly with a foam rubber hook (Leister type). This avoids iris tucking and reduces the risk of iris distortion. When the implant is correctly positioned, the roundness of the pupil must be checked and, if necessary, the correct positioning of the footplates can be verified with a gonioscope.

Viscoelastic Removal

At the end of surgery, it is essential that all viscoelastic be removed either with a simple cannula or with a system of irrigation/aspiration. The anterior chamber is refilled with balanced salt solution (BSS), and the water-tightness of the incisions is verified. If the incisions were not perfectly water-tight, saline can be injected into the corneal incision stroma to help sealing or else a 10-0 nylon suture can be placed (Figure 15-11D).

Iridectomy Problems

With angle-supported anterior chamber implants like the NuVita or Vivarte/GBR, it is not necessary to perform an iridectomy because the vaulting is sufficient to avoid a pupillary block. However, if the surgeon wishes to carry out an iridectomy or an iridotomy, it can be done either by laser before or after surgery or during surgery using a surgical procedure. It is preferable to avoid an iridectomy that is too basal because if the implant’s footplates rotate, they could go through the iridectomy and come into contact with the zonules or the crystalline lens.

Postoperative Care

Immediately following surgery, acetazolamide administered intravenously is recommended to reduce the risk of ocular hypertension and a tablet of acetazolamide is prescribed that same evening. By taking these precautions, in the author’s experience, no postoperative Urrets-Zavalla syndrome have been observed over the last 15 years.

Figure 15-12. GBR/Vivarte implant in place (courtesy of Norma Allemann).

Antibiotic steroid eye drops are given for 1 month. Refraction is checked the first day after surgery. In the case of overor undersizing or an error in the power of the lens, the implant can be exchanged quite rapidly.

Bioptics

The bioptics technique (LASIK flap + refractive phakic implant) is interesting where the optical characteristics of the implant cannot correct ametropia (eg, in the case of astigmatism or an optical spherical power not available in the desired implant range).

With the Vivarte/GBR, the LASIK flap is done immediately before opening the anterior chamber by using either a superior or nasal hinge. The IOL surgery is undertaken in the same manner as in cases not utilizing bioptics.

RESULTS IN MYOPIC PATIENTS

Indications

Myopia was the first indication for refractive implants. Unfortunately, the Vivarte/GBR implant is only available today for the correction of myopia or presbyopia. The manufacturers have not made a simple or toric hyperopic implant, although this type of implant could be used in a great number of cases.

The lens is available between -7 D and -20 D and takes into account the depth of the anterior chamber according to the different powers. Between -7 D and -13 D the anterior chamber depth must be equal to or more than 3.2 mm. Between -13 D and -18 D, the depth must be equal to or more than 3.4 mm, and above -18D it must be equal to or more than 3.6 mm. This restriction criteria excludes only a small number of patients and if the anterior chamber is not sufficiently deep, the Vivarte/GBR implant can be combined with a LASIK flap to correct astigmatism or residual ametropia.

Contraindications

The implant is contraindicated in the case of anterior segment pathologies and, in particular, endothelial abnormalities. Uveitis, cataract, synechia, neovascularization, and glaucoma are also contraindications. However, it is much better to propose a refractive implant to a patient with slight ocular hypertension rather than LASIK; indeed, LASIK will lower the intraocular pressure measured with applanation on a reshaped cornea and it will be difficult to know which baseline value to use for the tononometric follow-up of that patient. On the other hand, with a refractive implant, the measuring method is not modified and the risk of glaucoma is extremely low except in the case of postoperative steroid-induced hypertension.

Clinical Results

Clinical results with regards to myopic implants are excellent and are similar to those obtained with all other type of refractive implants (Figure 15-12).1,2,5-7,10-12

FOLDABLE PRESBYOPIC PHAKIC

INTRAOCULAR LENS (VIVARTE,

PRESBYOPIC, GBR NEWLIFE)

Concept

Using a presbyopic phakic implant is an extrapolation from pseudophakic multifocal implants. After placing a multifocal implant for cataract surgery, good results can be obtained (in 70% of cases) if the patient is emmetropic and without astigmatism. If the patient is ametropic or has residual astigmatism, the success rate falls to 30%.

A former study was carried out with Professor Eva Volkova in BRNO, Czech Republic that allowed us to establish the feasibility of the concept with emmetropes. The trial was then extended to cover ametropic patients, and an official study was undertaken in France under the “Huriet Law.”

Equipment and Methods

The lens used had the same optics as the Vivarte or the GBR (PMMA - tripod) (Figure 15-13). The optical part is made of hydrophilic acrylic and divided into three zones: central zone for distant vision, intermediate zone for near vision, and peripheral zone for distant vision. The lens was, therefore, simply a bifocal one. Optical power available for distance vision is between -5 D and +5 D. Addition for near vision is +2.5 D, which is a compromise, allowing the correction of patients between the ages of 50 and 60. The 50-year-old patient is slightly overcorrected and the 60-year-old patient is slightly undercorrected.

158 Chapter 15

Figure 15-13. GBR/Vivarte presbyopic implant.

Results

Forty eyes of 25 patients were operated on between August 2000 and December 2002. Ages were between 45 and 70 years. There were 16 women and 9 men. Preoperative refraction was between -5 D and +5 D. Some patients had LASIK beforehand to correct astigmatism or an associated ametropia. One patient had radial keratotomy. There were five myopic eyes and 35 hyperopic or emmetropic eyes. The results were excellent, with 75% obtaining a postoperative visual acuity above 20/30 and seeing J1/J2 without correction.

One patient suffered loss of visual acuity of greater than two lines between 3 and 4 months postoperatively. Visual

Indications

The eye must be normal, with an anterior chamber depth above 3.1 mm (calculated from the surface of the corneal epithelium to the anterior face of the crystalline lens) and the angle must be open. The minimum required endothelial density is equal to or above 2000 cells/mm². There must be no associated anterior segment pathology. The optical power of the implant is calculated according to Holladay’s formula.

Surgical Technique

The surgical technique is the same as the one described earlier.

fields, fluorescein angiography, and OCT showed no anomalies. After 3 or 4 months, visual acuity was restored.

Four eyes had complementary LASIK or PRK to treat residual ametropia. Visual results are shown in Table 15-1.

It must be noted that preoperative mean refraction is slightly hyperopic and that the postoperative results are slightly myopic. Preoperative uncorrected visual acuity (UCVA) is 20/40 and postoperative UCVA is 20/25. The technique gives a refractive result comparable to other refractive surgery techniques.

Preoperative best-corrected visual acuity (BCVA) is 20/20; this drops slightly postoperatively due to a loss of contrast sensitivity. Near BCVA is J1/J2 preoperatively, near postoperative UCVA is more or less the same.

Three implants were exchanged due to power or sizing errors. No particular problems were encountered.

Postoperative Outcome

LASIK or PRK Enhancement

In four eyes, it was necessary to carry out an enhancement with PRK or LASIK to improve visual acuity.

Removals

Two lenses were removed due to unsatisfactory results. In one case, the patient had an uncomfortable intermediate distance visual acuity; in the other case, there was a reduction in near and distance visual acuity.

Pupillary Ovalization

Five cases of moderate pupillary ovalization were observed along with synechiae in the angle.

Halos

Four patients out of 25 complained of halos. However, these halos did not prevent night driving even if driving was not as fast as before.

Cataracts, Glaucoma, and Corneal Edema

In this series, no cataract, definitive ocular hypertension, or corneal decompensation was observed.

Corneal Endothelium

After 1 year follow-up, endothelial cell loss was between 3% and 6%, which is normal following refractive implant surgery (Table 15-2).

An important loss was observed postoperatively in one patient because only central endothelial cell density was measured. After several months, the endothelial cell density of these patients returned to normal. It is, therefore, a

central intraoperative trauma, which explains the important loss measured at the beginning, cells from the periphery slowly replace cells lost in the center.

Loss of Visual Acuity

An average loss of visual acuity of less than one line was observed. This corresponds to a decrease in contrast sensitivity, which is easy to understand with a multifocal implant. It must be remembered that multifocality reduces light reaching the retina and this is not as accepted with older patients because with age there is a physiological reduction of retinal illumination due to a natural loss of crystalline lens transparency and a reduction of the pupil diameter.

It is, therefore, important to be very careful with patients over 60 to 65 years of age who show the beginning of crystalline lens opacity.

CONCLUSIONS

The results of presbyopic phakic implants are satisfactory on the condition that the following contraindications are taken into account:

•Shallow anterior chamber, below 3.1 mm; rarefied endothelium below 2000 cells/mm², anterior segment pathology, anomalies of the posterior pole

•Patients that are too “critical”

•Finally, because of the risk of nocturnal halos, it is preferable not to do surgery on patients having to drive at night for professional reasons, such as taxi drivers

The results are very good in situations in which the patient is warned that it is an alternative to presbyopic surgery that use of a multifocal implant on a phakic eye is a compromise between an excellent preoperative vision and