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

age in hyperopes in whom natural lenses are growing in a narrow anterior chamber

•This PIOL should perform well in patients who have a shallow anterior chamber and a narrow angle such as in high hyperopia in which implantation becomes impossible54

•The iris claw lens has a high rate of efficiency, predictability and safety in correction of hyperopia53

•The lens respects the angle issue which becomes narrower by age, avoiding angle supported lens complications

•There is no stress exerted on the Zonules as in posterior chamber IOLs.

The ArtisanTM Toric PIOL for the correction of astigmatism in hyperopes was added in 1999.

In 1980 a modified iris claw lens with an occluding optic was implanted for the first time in an aphakic eye of a patient suffering from untreatable diplopia after cerebral trauma. This lens is still in situ today and the patient has a clear cornea and no lens opacification.10 The ArtisanTM phakic IOL is a typical spin-off of the fixation principle of the claw lenses.

The one-piece convex-concave ArtisanTM PIOL is made of Perspex CQ (clinical quality UV absorbing PMMA). The lenses are manufactured by Ophtec BV in Groningen. The Netherlands using a special compression moulding technology to obtain “claws” with a high tensile strength and superb flexibility of the haptics.55 The overall diameter of the lenses is 8.5 mm with an optic of 5 or 6 mm. The height of the lenses (regardless of power) does not exceed 0.96 mm. The two diametrically opposed haptics attach the lens to the mid-peripheral, virtually immobile, iris stroma, allowing relatively unrestricted dilation and constriction of the pupil.52

The power of the ArtisanTM Myopia PIOL with 5 mm optic ranges from –3.0 to –23.0 D. The ArtisanTM Myopia PIOL with 6 mm optic ranges from –3.0 to –15.5 D while the ArtisanTM Hyperopia PIOLs range from +1 to +12 D).53 The Artisan TM Toric PIOLs correct cylinders from 2 to 7 D. All lenses are manufactured in 0.5 D increments. The Artisan TM Phakic IOLs can correct:

•Myopia, hyperopia, astigmatism (Toric PIOL)

•Presbyopia (monocular low plus power IOL)

•Incorrect power of posterior chamber (PC) IOLs (Piggyback IOL).

Designs

In 1990 Worst and Fechner modified the Worst-Fechner biconcave lens in order to reduce postoperative complications.56 The new design, called Artisan iris fixated lens (Ophthec BV Groningen, The Netherlands), is a onepiece all-PMMA lens with a convex-concave optic of 5 or 6 mm in diameter (Figs 14.2 and 14.3). The vault height of the lens does not exceed 0.96 mm in myopic lenses, regardless of their power, and 1.0 mm in hyperopic lenses.59 The Artisan Hyperopia lens (model 203) has a power range from +1.0 D to +12.0 D, and optic diameter of 5 mm. All the lenses are manufactured in 0.5 D steps. The two diametrically opposed haptics fixate the lens on the iris by enclavation of midperipheral iris stroma. The distance from the edge of the optic to the corneal endothelium is 1.5 to 2.0 mm depending on the eye anatomy and lens power.59

The Artisan lens is also available for hyperopic astigmatism correction since 1999. The Artisan Toric lens corrects astigmatism from 2 to 7 D, and it is a biconcave lens. The fixation is versatile, as the lens may be fixed with the necessary angle to correct any astigmatism. There are two different models of this lens depending on the axis location:

a.Model “A”: The cylinder axis runs on the axis that runs through the claws.

b.Model “B”: The cylinder axis is perpendicular to the axis that runs through the claws.

Technique of Artisan lens implantation : personal experience and technique

Local anesthesia is preferred. Topical anesthesia is not advisable for Artisan lens implantation.

If local anesthesia is given, the para-bulbar injection of 8 ml of Bupivacaine 0.75 percent and Lidocaine 2 percent with 1 cc of hyaluronidase. This technique is preferred and should result in total immobility of the

Figure 14.2: Artisan (Ophtec, Netherlands)

Figure 14.3: Artisan lens, details of the iris claw

globe and the eyelids. Perform orbital compression with a Honan Balloon (Lebanon Corporation, Lebanon, IN) and /or massage for 20 minutes until low preoperative pressure is obtained. This will improve the accessibility to and operative space in the anterior chamber. Pupillary miosis, using one drop of pilocarpine 2 percent (Alcon

– Cusi, Barcelona, Spain), 30 minutes before surgery.15 Cover all eye lashes since they are potential sources of infection. Do not allow fluid-filled reservoirs between

the plastic drapes and the skin and eyelashes during surgery.

Because the white-to-white distance is shorter vertically than horizontally, we recommend a horizontal enclavation and also a superior approach for the ArtisanTM hyperopia lens.52

With an astigmatic marker (Katena, Denville, NJ) the horizontal 180º corneal axis is identified and two

1.5 mm stab incisions, 2 mm away from the limbus and directed toward the peripheral iris are done at the 3 and 9 o’clock position using a 1.4 mm MVR blade (Sharpoint, Surgical Specialities Corporation Reading,PS).3

Inject a miotic solution through the lateral incision, followed by regular cohesive viscoelastic material (Healon). Be careful with dispersive viscoelastics because their removal is difficult and there is a postoperative pressure risk. Dispersive and cohesive viscoelastic have different effects on lens epithelial cells. Dispersive viscoelastics could cause the lens to float in the viscoelastic material and have no contact with the iris during the implantation. The enclavation would also be more difficult.5 High viscosity cohesives such as Healon GV are not advised due to rise in intraocular pressure.

A 6 mm incision is made at the superior clear cornea just in front of the vascular arcades.This incision size was selected after finding difficulties in lenses with power higher than +5 through 5.5 mm.3

Cover the conjunctiva with the viscoelastic material to avoid any contact between it and the PIOL during the implantation. Then the implant is inserted using a specially designed implantation forceps (Artsan lens forceps, Ophtec) and then rotated to a horizontal position in the centre of the anterior chamber with a Lester hook (Catena, Denville, NG). It is then held in this position at the 12 o’clock position of the optic with Artisan lens forceps and the optic was centred on the pupil.3

There are, two techniques of enclavation available: the hook technique and the forceps. With the hook technique, hold the lens in the centre of the optic with the implantation forceps, push a fold of mid-peripheral iris tissue forward with the blunt enclavation Needle (snow-ploughing) and place the fold between the claws. The handle provided carries a right and a left needle.5

If using the enclavation forceps, through the stab incision take a fold of mid-peripheral iris tissue into the specially designed iris forceps (Alio iris forceps, ASICO, Westmont, IL) and engage into the claw of the lens. During these maneuvers, hold the lens in the centre over the pupil with the implantation forceps and depress the lens slightly.

For both instruments it is important not to pull on the iris, but bringing the iris fold gently between the claws. Never pull on the iris. The pupil is used as a reference for centring the lens.

Make a peripheral iridotomy using a specially designed iris forceps (Alio iris scissors, ASICO) as an additional precaution to prevent pupillary block, glaucoma, and iris prolapse during surgery. An iridotomy is cosmetically more attractive and prevents ghost images.3

The incision is then sutured with a three –bite running nylon 10/0 suture (ALCON).

Before closing the knot, the cohesive viscoelastic should be removed by careful washing with a 27 –gauge cannula using a total of 10 cc of balanced saline solution (BSS, Alcon –Cusi, Barcelona Spain). It was found that automated irrigation is not a safe maneuver when performed after the fixation of the implant.3

The big advantage of this lens is that it can be centred over the pupil. The disadvantage is that more surgical skill is required for its insertion than for insertion of other kinds of lenses.

Although these lenses are more difficult to insert, the clinical results are usually spectacular. The quality of vision after insertion of the iris claw and the anterior chamber lenses appears to be significantly better than the quality of vision after LASIK, and usually these patients see well either the next day or shortly thereafter with improvements that are dramatic.

The future challenging phakic IOL for implantation should be designed to:

•Not put a pressure on the angle,

•Not move in the anterior chamber

•Not flex against the peripheral endothelium

•Not rub against the iris

•Not cause damage to the endothelium on insertion

•Not cause damage to the lens on insertion

•Not require an incision of more than 1.5 to 2 mm

•Not be difficult to insert

•Not be difficult to remove

•Not be difficult to exchange4

Long-term follow-up shows that the Artisan is a

lens made to stay for life in the eyes of hyperopes. The

lower incidence of complication, the high BCVA, and the minimal effect on the total endothelial count is on its behalf in front of the other PIOLs.

In 2002 we carried on a study on the Artisan PIOL, 3 for high hyperopic patients, which is a modified model of the iris claw Fechner Worst phakic lens for the correction of myopia. Its lack of angular support reduces the possibility of peripheral contact with the corneal endothelium. This PIOL works well in patients who have an anterior chamber less than 3.4 mm or a narrow angle, as it is placed at the central anterior chamber without interfering with the anterior chamber angle, allowing an intact accommodation mechanism. This is especially important when we consider previous reports that hyperopia greater than + 6.00 D shows a shallower anterior chamber when compared with the emmetrope or low myope, a tendency that becomes even more evident with increase in age. This fact makes it even more compelling to have a PIOL placed at the central area of the anterior chamber, where this space will be better maintained over time.

The hyperopic Artisan PIOL seems to be an adequate lens to correct high hyperopia; further improvement in predictability and implantation technique, using a foldable model, will enhance its application for correction of hyperopia. Alió, advocated its use in hyperopia higher than +5.00 to +6.00 D, or in eyes in which central corneal steepening induced by corneal surgery will be higher than 50 D, a limit frequently associated with night vision disability and loss BSCVA.

A three years follow-up study carried by Saxena et al, 2003, recorded that implantation of the Artisan hypermetropic lens leads to accurate and stable refractive results with no significant loss of vision. More attention should be paid to convex iridis and shallow anterior chamber during the preoperative screening to avoid unnecessary complications.60

SPECIFIC COMPLICATIONS IN HYPEROPIC

ARTISAN LENS IMPLANTATION

How to Avoid Complications

Any kind of complication is surgery dependent and

not due to the implant itself. Therefore, learning the exact technique is essential. It is very important for the surgeon to receive training before operating in vivo.

For beginners, general anesthesia is more comfortable for both the patient and the surgeon. If a local anesthetic is chosen, a peribulbar is less dangerous than a retrobulbar. A scleral perforation can always arise, especially in myopic eyes (≥ –17 D). A purely topical anesthetic appears dangerous, in our opinion. Any uncoordinated movement may cause contact between the implant, the anterior capsule, or the endothelium. Patient sedation never protects the surgeon from a sudden, brusque movement and the subsequent consequences.

When the pupil is insufficiently constricted, viscoelastic material may be trapped in the pupillary area under the implant and is the difficult to remove. Insufficient miosis might also lead to touch of the natural lens during implantation. Under these circumstances centring of the PIOL is more difficult. Manipulation of the PIOL in the anterior chamber can cause endothelial touch or touch of the crystalline lens. This contact could happen when the anterior chamber has collapsed due to external loss of viscoelastic material. That is why the use of a high viscosity viscoelastic material such as ArtiviscTM or HealonGVTM is mandatory. It should be entirely washed out. Other viscoelastic materials with lower viscosity fail to maintain the anterior chamber and cannot be washed out completely.

Due to the typical hydrostatic and hydrodynamic conditions present during insertion of a high myopia implant, iris prolapse tends to occur more easily than in normal cataract surgery. Once incarcerated in the

incision, reposition is more difficult and the incarceration tends to recur. Iris prolapse tends to occur more often in corneoscleral incisions than in tunnel incisions.

The most difficult step of this surgical technique is encountered when the surgeon enclavates the iris fold in the slit of the haptics. This could make perfect centering of the PIOL difficult. Proper centering needs a lot of attention because of the possible postoperative problems of glare and halos. One should also pay attention to creating a fold that is not too small; otherwise the PIOL can luxate into the anterior chamber and cause damage to the corneal endothelium. Another potential complication that can occur during enclavation is the traumatizing effect on the iris or endothelium, especially when instruments are used that are not made for this type of surgery. Iris damage can easily occur when “home-made” enclavation needles are used, which have sharp tips. The special “Ophtec Enclavation Needles” have soft polished tips.55

Intraoperative Complications

Implant Damage

Damage to the implant can occur during its insertion into the anterior chamber if the special forceps are not used. It can also occur during its release and manipulation under the iris. Both the surgeon and the technician must be very careful when the lens is taken from the package and inserted into the forceps. Do not forget the implant is very thin and rather expensive and can be damaged easily.56

Hemorrhage

Bleeding can occur during the manual surgical iridectomy, but should not be common. If it occurs, inject

some viscoelastic through the paracentesis, wait several minutes for the bleeding to stop, then remove it.

Iris Damage

It is possible to damage the posterior pigment surface of the iris with the implant, and we recommend injecting viscoelastic under the iris to avoid this complication. The surgeon has to be very careful during the manual iridectomy not to pull and tear the iris strenuously through the paracentesis because this can cause iris damage and actual bleeding.

Lens Damage

The worst complication during the actual procedure is the immediate creation of lens damage and cataract. The surgeon must always be ready to convert the surgery to phacoemulsification with IOL implantation. The lens can be damaged in the following steps during surgery.

Corneal incisions due to sudden knife insertion or eye ball movement

•Paracentesis due to insufficient viscoelastic in the anterior chamber, too quick blade movement, or eye ball movement

•Implant insertion due to contact between the forceps and the anterior capsule of the lens

•Implant manipulation due to pushing the implant on the lens

•Viscoelastic removal due to inadvertent movement of irrigation or aspiration needle, and excessively forceful BSS irrigation.

Endothelial Damage

Inadequate viscoelastic protection may allow endothelial cell damage during implant insertion. Postoperative endothelial cell loss was found by Alió to be similar to that reported in previous studies with anterior chamber PIOLs57 although other reports on the Artisan lens in myopic eyes have shown larger losses and a trend to chronic cell loss57,51,59 (Table 14.4).

Zonular Fibre Damage

Pushing the implant too strenuously under the iris may cause the edge of the implant to damage the Zonular

fibres. We have to remember that a large number of Zonular fibres stretch across the anterior periphery of the lens capsule. This could lead to implant dislocation and optic zone decentration if the future. That is why we try to fold and the release the implant allowing it to go under the iris, never pushing it there with force.56

Postoperative Complications

Corneal Edema

A persistent corneal oedema, especially at 12 o’clock, is due to implant endothelium contact at the time of the implantation. This oedema usually disappears.

Iris Damage

At the time of enclavation, the surgeon may damage the iris, which will result in a localized iris atrophy that is not progressive.

Implant Decentration

This implies that if the implant is not well centred at the end of procedure it will remain that way and this will cause halos and glare that the patient will complain about. Therefore, it must be recentred, preferably during the primary surgery.

Pupil deformation was present in small degrees in three eyes (5.26%). Two eyes (3.51%) showed minor degrees of decentration of the PIOL optic of less than 1 mm from the pupillary centre. None of these eyes were symptomatic.2

Early rise of IOP

Pupillary blocks occurs if an iridectomy or an iridotomy is not well checked. This can be performed with an Nd:Yag laser preoperatively. Make sure that both layers of iris are perforated and that the anterior capsule of the crystalline or the zonular fibres is visible. Preferably it should be performed at 12 o’clock to avoid any diplopia.

Another cause of high pressure in the immediate postoperative period is the persistence of viscoelastics in the anterior chamber. Therefore, cohesive viscoelastic

material is recommended because it can be removed more easily than a dispersive one.

Retinal Detachment

It was reported in 0.8 percent of eyes in the same publication. No relationship with the implant has been shown.52

Implant Induced Astigmatism

If the implant has induced astigmatism of more than 1.25 D to 1.50 D, remove the stitches five weeks after the operation.

Cataract

An age-related cataract may develop in some patients. Since postoperative keratometry readings are practically unchanged and because a preoperative biometry will always be carried out, the implant is removed and cataract surgery is proceeded as usual.

Postoperative Inflammation

Most of the cases develop mild uveitis grade 1+/– 2. rarely grade 3 iridocyclitis is seen with membranes and small sterile hypopyon and absence of ciliary injection. or pain. This anterior iridocyclitis is controlled with an intensive steroid therapy and cycloplegics.

Endothelial Cell Density Changes

The endothelial cell loss in the first six months was 6.8 percent of the baseline endothelial count,while after

one year the losses accounts for 9.4 percent of baseline records.3

Halos and Glare

The problem of halos and glare is secondary to the relationship between the pupillary diameter and the diameter of the Artisan lens (Table 14.5).

Halos and night glare usually occurs if pupillary diameter in scotopic or mesopic conditions exceeds the lens optical diameter. Decentration and tilting of the implant may cause in addition diplopia and astigmatism. If necessary, a 5 mm Artisan lens can be replaced by a 6 mm one.

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Antonio Marinho

Ramiro Salgado (Portugal)

WHY TORIC PHAKIC IOLs?

Phakic IOLs have been used as a refractive surgery tool for quite a while. Different types of phakic IOLs have shown a very large range of correction of refractive errors (–23.00 to +12.00) with exceptional predictability, accuracy and stability without disturbing the normal mechanism of accommodation. One of the drawbacks of the classical phakic IOLs has been the inability to address the correction of astigmatism. As most patients implanted with phakic IOLs have some degree of astigmatism, the issue has been solved in three ways:

a.Spectacles or contact lenses

b.Management of suture

c.Bioptics

Of course, the first option (spectacles or contact

lenses) is not suitable for most patients, as their motivation for surgery is to get rid of glasses. The management of the suture is very helpful in astigmatisms up to 2 diopters. Nevertheless, it is only possible when we perform a large incision (Phakic 6 or Artisan), but not with small incision phakic IOLs (Icare, Vivarte, Acrysof, ICL, PRL). So, the real and reliable way to correct astigmatism after implantation of phakic IOLs (preexisting or induced) is to perform Laser surgery (commonly Lasik). This technique of surgery in two steps (Phakic IOL + Lasik) has been named Bioptics a few years ago by Roberto Zaldivar (Argentina).

These problems led to the development of toric phakic IOLs that is, a phakic IOL that is able to correct simple astigmatism or associated with a spherical refractive error.

The advantages of this type of IOLs are clear:

a.Only one surgery

b.Possibility of full correction in special cases (contraindications of Lasik)

For most patients the most important advantage of

toric phakic IOL, is that in one surgery the full correction will be achieved. This is important, not only for economic factors (cost of 1 vs 2 surgeries), but also avoids the mandatory interval (usually 3 months) between implantation and Lasik, thus achieving full rehabilitation much faster. However there are cases, where the availability of a toric phakic IOL is much more important. In fact in some eyes it is not possible to perform Lasik.The more frequent of these cases include: keratoconus (even subclinical forms) or patients previously submitted to corneal refractive surgeries (with thin corneas). Also in high astigmatisms after penetrating keratoplasty, although Lasik has been attempted, the results are usually erratic and poor, so if intraocular correction is possible, it would serve the patient better. In all these patients a toric phakic IOL is the key to success.

TYPES OF TORIC PHAKIC IOLs

There are only available two toric phakic IOLs:

a.Toric Artisan

b.Toric ICL

The Artisan is a well known anterior chamber PMMA

iris supported phakic IOL. It is available for myopia and hyperopia and now for astigmatism.

The ICL is a posterior chamber collamer phakic IOL. A toric type has been presented, although very few and scattered clinical data are available. As we do not have personal experience or knowledge of reliable data about the toric ICL, further discussion in this chapter will be limited to the toric Artisan.

TORIC ARTISAN—THE IOL

a.PMMA

b.Oveall diameter of 8.5 mm

c.Optical zone of 5.0 mm

d.Convex/concave design

e.Spherical anterior surface

f.Spherocylindrical posterior surface

g.Available (sphere) –3.00 to –23.50

h.Available (sphere) +1.00 to +12.00

i.Available (cylinder) 2.00 to 7.00

According to the axis of astigmatism, there are two

types of toric Artisan. In Type A the axis of astigmatism is in the longer axis of the IOL (Fig. 15.1).This IOL is labelled 0º and is implanted if the axis of the cylinder is between 0º and 45º or between 135º and 180º. In Type B the axis of the astigmatism is perpendicular to the longer axis of the IOL (Fig. 15.2). This IOL is labelled 90º and is implanted if the axis of the cylinder is between 45º and 135º. The important advantage of the availability of these two types of toric Artisan is to enable the surgeon to retain his surgical technique as close as possible to standard cases. For instance, if the surgeon usually performs a 12 o’clock incision and has a cylinder at 90º it would be almost impossible to implant if only Type A was available.