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

3.Alio JL, de la Hoz F, Perez-Santoja JJ, et al . Phakic anterior chamber lenses for the correction of myopia. A 7-year cumulative analysis of complications in 263 cases. Ophthalmology 1999;106:458-66.

4.Ferreira de Souza, R, Forseto A, Nosè R, et al. Anterior chamber intraocular lenses for high myopia. Five-year results. J Cataract Refract Surg 2001; 27:1248-53.

5.Aliò JL, de la Hoz F, Ruiz-Moreno JM, Salem TF. Cataract surgery in highly myopic eyes corrected by phakic anterior chamber angle-supported lenses. J Cataract Refract Surg 2000; 26:1303-11.

6.Brauweiler PH, Wehler T, Busin M. High incidence of cataract formation after implantation of a silicone posterior chamber lens in phakic, highly myopic eyes. Ophthalmology 1999; 106:1651-5.

7.Alio JL, Ruiz-Moreno JM, Artola A. Retinal detachment as a potential hazard in surgical correction of severe myopia

with phakic anterior chamber lenses. Am J Ophthalmol 1993;115:145-8.

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

9.Mimouni F, Colin J, Koffi V, Bonnet P. Damage to the corneal endothelium from anterior chamber intraocular lenses in phakic myopic eyes. Refract Corneal Surg 1991; 7:282-5.

10.Ardjomand N, Kölli H, Vidic B, et al. Pupillary block after phakic anterior chamber intraocular lens implantation. J Cataract Refract Surg 2002; 28:1080-1.

11.PerezSantonja JJ, Ruiz-Moreno JM, de la Hoz F, et al. Endophthalmitis after phakic intraocular lens implantation to correct high myopia. J Cataract Refract Surg 1999; 25:1295-8.

Antonio Marinho (Portugal)

INTRODUCTION

Phakic intraocular lenses have been used in refractive surgery during the last 15 years and are more and more widely accepted. They present important advantages over corneal (laser) surgery in high ametropias showing high accuracy, predictability and stability of refractive result, as they are independent of tissue healing. They also preserve accommodation (very important in young patients)what is an advantage over lens surgery.

There are today phakic IOLs designed for the anterior and posterior chamber. Those for the anterior chamber can have an angular support (Phakic 6, Vivarte; Icare) or an iris support (Artisan). Those to be placed in the posterior chamber can rest on the sulcus (ICL) or float in the aqueous humour (PRL).

Although the refractive results are extremely good in phakic IOLs regardless the model used, different types of long-term complications may be present. The anterior chamber angle supported phakic IOLs are often associated with pupil distortion (ovalisation) and the posterior chamber phakic IOLs may induce cataracts. Neither of these problems is seen with the Artisan lens.

The Artisan is a phakic IOL made of PMMA with an overall length of 8.5 mm (on size fits all) supported by the iris tissue. As there is no contact with the angle and the IOL is at a safe distance from the corneal endothelium and the natural lens, almost no complications are associated with Artisan. There is now an worldwide experience with this lens in myopia, hyperopia and astigmatism with excellent results.

ARTIFLEX SURGERY

To introduce an Artiflex, we use the following rules:

a.Constrict the pupil (2 drops of 2% pilocarpine 15 minutes before surgery).

b.Topical anesthesia.

c.Two 1 mm sideport incisions at 10 and 2 o’clock.

d.Main incision (3.2 mm) at 12 o’clock (clear cornea)

e.Put the Artiflex in the introduction spatula (Fig. 10.2).

f.Fill the anterior chamber with vioscoelastic.

g.Introduce the Artiflex (the IOL folds upon itself).

h.Take out the spatula (pushing it gentle downwards).

i.Rotate the Artiflex to the horizontal position.

j.Grasp the PMMA haptics with the forceps (Fig. 10.3) and with the enclavation “needle” introduce sufficient amount of iris tissue in both claws.

Figure 10.3: Grasping forceps

k.Check good centration of the IOL.

l.Perform iridotomy/iridectomy (mandatory).

m.Remove viscoelastic.

n.Hydrate the incisions (no suture needed).

o.Topical antibiotic and steroids for 1 week post-op.

Figure 10.4: 1 day post-op

ARTIFLEX REFRACTIVE RESULTS

We have implanted 23 eyes of 15 patients (Fig. 10.4). 11 were female and 4 male. The myopia ranged from –5.50 to –11.75 (mean value: –8.75 ). The patients age is between 20 and 43 years (mean: 31.7).The followup is from two to 13 months.

Concerning accuracy, 95 percent of the eyes had a final refraction between +0.50 and –0.50. All the eyes were between +1.00 and –1.00. The Artiflex proved to be very accurate and the residual refraction that we see in 5 percent is due to pre-op cylinder, as the Artiflex is not available yet in toric model.

None of the operated eyes lost any line of best corrected visual acuity (BCVA) and eight of the eyes gained lines (7 gained one line and 1 gained 2 lines).

The stability of the refraction was also impressive. In most cases the refraction at day one remained unchanged throughout the study.

One concern with all the new anterior segment surgical procedures is the safety for the corneal endothelium. Before the implantation the eyes had amean endothelial cell population of 2425 cells/mm. Three months after surgery the density was 2370 cells/

mm. These results show that the surgical technique is safe, although it is too early to judge the endothelial safety of the Artiflex.

ARTIFLEX COMPLICATIONS

In our series there were almost no complications. In four eyes there were mild pigment precipitates on the Artiflex. These precipitates did not cause any symptoms or visual disturbance. No treatment was implemented and the precipitates went away.

In two eyes there were also iris pigment, but with reduced visual acuity (2 lines). In these eyes oral steroids were given for nine days and the pigment disappeared with full recovery.

ARTIFLEX FUTURE

Artiflex proved to be a very accurate and safe phakic IOL associated with very few and unimportant complications.

It presents all the advantages of the classical Artisan, such as absence of angle problems and pupil distortion as well as a safe distance to the corneal endothelium and the natural lens. As the Artisan one size fits all, thus having the great advantage of not needing to determinate exactly the size of the eye to be implanted (which is very difficult).

What turns Artiflex unique is the fact that being a foldable IOL it is possible to introduce though a standard phaco incision (3.2 mm) adding to the previous mentioned advantages the following:

a.Possible use of topical anesthesia.

b.No astigmatism induced.

c.Rapid recovery.

d.Patient comfort.

In the future Artiflex will be available for higher myopia, hyperopia and astigmatism.

It will be certainly the gold standard for future phakic IOLs.

Sanjay Chaudhary (India)

INTRODUCTION

The iris claw fixation technique for the correction of aphakia following extra or intracapsular cataract surgery has been used since 1978. This design was introduced by Dr Jan Worst and in India it was popularised by Dr Daljit Singh with slight modifications. With the advent of Posterior Chamber lenses, this lens lost most of its popularity. The design has again found place as a back up lens in lieu of angle supported anterior chamber lens in cases of complicated cataract surgery.

The uniqueness of the fixation principle and the decades of successful use in cataract surgery led to the development of phakic intraocular lenses. In 1986, Worst and Fechner introduced the first phakic biconcave intraocular lenses for the correction of myopia. In 1990, the design was further developed into today’s convexconcave lens.

LENS DESIGN

Verisyse (Artisan) phakic intraocular lens is an iris fixated lens. It has a unique one piece design. The size of the lens is 8.5 mm and it bears a central rounded optical part of 5.0 mm. This lens is also available in an optic diameter of 6.0 mm.

The extreme end of the haptic loop bears a fine cut and is refered to as the iris claw. The periphral part of the iris is enclaved through this claw to secure the fixation of the lens.

These lenses are enclaved in the peripheral, practically immobile part of the eye. The enclaved part of the iris forms a cushion, which shields the cornea from possible contact with the haptics. Because of the concave design, the

CRITICAL DISTANCES TO THE

ENDOTHELIUM

Figure 11.5: Pupil dilation is virtually unaffected by the lens

This is the distance to be maintained between the phakic lens and the corneal endothelium. It is recommended not to reduce the critical distance to less than 1.5 mm.

Veriflex (Artiflex) is a foldable iris claw lens. The optic is made of silicon while the haptics are of PMMA.

The lens can be folded and pass through a 3.0 mm incision.

Verisyse Toric phakic IOL has a spherical anterior and a toric posterior surface. It can also correct cylinder from 2 to 7 diopter.

Because of the concave design of the lens, an adequate gap between the phakic implant and the natural lens is always guaranteed, including during bowing of the anterior surface of natural lens during accommodation in young patients.

The size of the retinal image. The size of the retinal image is changed by the implant because of the reduction in the minification of the retinal image as produced by high spectacle concave lens, with resultant increase in the visual acuity of the patient.

RANGE OF CORRECTION

The range of correction available is

•Myopia of –3.0 to –23.5 D

•Hyperopia of +1.0 D to +12.0 D

•Toric power of 2 to 7 diopters.

MINIMUM REQUIREMENTS

•Minimum age should be 18 years

•The number should be stable for at least one year.

PREOPERATIVE EVALUATION

Discontinue the use of contact lens before screening, two weeks before for hard/rigid contacts and one week before for soft contacts.

•History especially for refractive stability

•Refraction: Cycloplegic refraction is a must (particularly in hyperopia). It is important to remember that certain autorefractometers have a design limit to their scanning range and may not be able to handle extremes of refractive errors.

•Slit lamp

•Corneal topography

•Keratometry

•Biometry

•Pachymetry

•Pupil width (mesopic)

•Endothelial cell count

•Fundus by indirect ophthalmoscopy in a fully dialated pupil

•Status of other eye.

PREOPERATIVE MANAGEMENT

•Stop use of contact lenses 48 hours prior to surgery.

•Topical antibiotics one day before the operation.

•One drop of pilocarpine 1 percent 45 min before surgery.

OPERATION

Anesthesia

The decision whether to opt for local or general anesthesia made by the doctor in consultation with the patient. The considerably greater axial length of highly myopic eyes harbours the risk of globe perforation in the case of retrobulbar or peribulbar anesthesia. General anesthesia completely removes this risk.

If the surgeon opts for local anesthesia, a parabulbar or sub-Tenon’s injection technique is recommended. Topical anesthesia is a good alternative but the surgical steps are sometimes painful especially when the iris is being tucked in the claw of the lens.

SURGICAL TECHNIQUE

When Using an Enclavating Needle

Make two paracentesis, one at 10 and the other at 2 o’clock. The direction of the paracentesis should point to the enclavation site. Fill the anterior chamber through the paracentesis with a viscoelastic, preferably a cohesive one as these are easy to remove later with least chance of a postoperative rise of intraocular pressure.

A 5 mm or a 6 mm point is marked on the cornea depending on the size of the lens.

A fornix based conjunctival flap is made and the episcleral bleeders are cauterised.

A 0.3 mm deep and 5 mm across inverse arcuate or a frown shaped incision is placed on the sclera, with the convexity 0.5 mm away from the limbus.

A scleral tunnel is now made which enters 1.5 mm of the corneal tissue.

The chamber is entered with a 3 mm keratome and is further enlarged with a 5 mm lancet for a 5 mm lens.

The Verisyse phakic IOL is now pushed into the anterior chamber to lie over the iris. It is then dialled with a lens dialler such that the haptics are in the 3 and 9 o’clock position and the optic is centred over the pupil. Inject more viscoelastic over the lens.

If you are a right handed person, enclavate the iris in the right claw first. For this, hold the enclavation needle in the right hand and introduce it through the 10 o’clock port. Hold the lens holder in the left hand and grip the lens from its optical part. Push the enclavating needle against the iris under the claw to raise a small iris fold, and then pass this fold of iris in the claw of the lens with the needle.

Refill the chamber with viscoelastic.

For fixing the other claw, change hands. Pass the needle through the 2 o’clock port and enclavate the iris in a similar fashion.

Lightly push the lens with a lens pusher to ensure a stable and a firm grip of the iris in the lens claws.

To reduce the risk of pupillary block, one peripheral iridectomy is done at the 12 o’clock.

To reduce the risk of a postoperative rise in intraocular pressure, the visco-elastic should be removed as completely as possible.

Hydrate the wound edges and inflate the chamber from a paracentesis to ensure a sutureless closure of the wound.

The Instruments

•Verisyse manipulator

•Verisyse holding forceps

•Verisyse enclavation needle

Figure 11.6: Verisyse manipulator

Figure 11.7: Verisyse holding forceps

Figure 11.8: Verisyse enclavation needle

Enclavation

The enclavation needle has two sides, one for the enclavation of the left haptic and one for that of the right haptic.

While you are holding the Verisyse optic with the implantation forceps, create a small fold in the iris tissue with the enclavation needle underneath the haptics at the desired enclavation site. Perform the enclavation by guiding the fold of iris tissue upwards through the VerisyseTM open haptics with the enclavation needle. In this way, both arms of the haptics open and grasp the iris tissue. The iris tissue must be enclaved significantly and sufficiently between the two haptic arms in order to guarantee a long-lasting stable lens position.

Schematic Representation of Enclavation

Figures 11.9A and B: Using the enclavation needle, create a fold out of iris tissue underneath the haptic apex (A to C). Lift the iris fold slightly or push the lens gently downwards with the implantation forceps. This will cause both ends of the haptics to open and enclose the fold in the iris (D and E). Carefully retract the enclavation needle. The iris is enclaved (F).

Recommendation:

Start the enclavation on the side of your dominant hand. So, if you are right-handed, start on the right.

In this way, the lens will already be fixated to the iris on one side, making it easier to enclave the second side.

Enclavation with the Enclavation Forceps

Figure 11.10

Technique

Using the enclavation forceps, hold one iris fold under the haptics of the lens.

Hold the lens with the implantation forceps and press the lens down carefully, without lifting the enclavation forceps.

Carefully withdraw the implantation forceps before opening the enclavation forceps and releasing the iris folds.

CONTRAINDICATIONS

•Any type of the cataract

•Retinal detachment or a family history of retinal detachment

•Abnormal pupil

•Abnormal cornea

•Abnormal iris

•Patients whose endothelial cell count is < 2,000 cells/ mm²

•Anterior chamber depth too low (less than 2.6 mm.)

•IOP > 21 mmHg or family history of glaucoma

•Chronic or recurrent uveitis/iritis

•Rubeosis iridis

•Pre-existing macular degeneration, retinopathy

•Age below 18 years

•Pupil width under mesopic conditions > 5 mm.

COMPLICATIONS

Intraoperative Complications

•Hyphema

•Iridodialysis

•Claw damage

•Haptic break

•Lenticular damage

•Eccentric fixation of lens.

Early Postoperative Complications

•Intraocular infection

•Wound leak and shallow AC

•Iris prolapse

•Rise in intraocular pressure

•Corneal oedema

•Iritis

•Pigment dispersal in AC

•IOL dislocation

•Pigment deposits on the IOL and natural lens Pupillary block glaucoma and iris bombé.

Late Postoperative Complications (not necessarily lens-related)

•Halo/glare

•Corneal oedema

•Chronic iridocyclitis

•Iris atrophy esp. at site of enclavation

•Rubeosis iridis

•Retinal detachment

•Corneal dystrophy and bullous keratopathy

•Glaucoma

•Cataract

•Induced astigmatism

•Ametropia and aniseikonia

•CME

•Unaccepable refractive error.

POSTOPERATIVE MEDICATION

An antibiotic steroid combination is used four times a day and then slowly tapered off. An early rise od IOP is managed by IOP lowering agents as required.

POSTOPERATIVE EXAMINATIONS

Special emphasis should be laid on:

•Iritis detection

•IOP

•Endothelial cell count

•Residual refractive error

•Lenticular changes.

•Retina evaluation

Patients must be told not to rub the eye that has been operated on because vigorous rubbing can lead to corneal edema as a result of intermittent contact of the IOL with the endothelium.

CALCULATION OF REFRACTIVE POWER

OF LENS

Van der Heijde developed a formula for the preoperative calculation of refractive correction with the phakic intraocular lens Verisyse.

Contrary to the calculation of lens power for aphakic lenses, the axial eye length plays no role in phakic refractive lenses; only the anterior chamber depth, corneal radii in diopters and subjective refraction do so.

Method

P= Predicted refractive power of implant in dioptres for a given anterior chamber depth

K = Mean K-values in diopters R = Refraction in diopters

ACL=Implantation site of the phakic lens (anterior chamber depth minus the convexity correction)

The convexity correction is different for the different lens types:

VRSH 50 Verisyse hyperopia 5.0—5 mm optic – convexity correction: 0.6 mm

VRSM 60 Verisyse myopia 6.0—6 mm optic – convexity correction: 0.8 mm

VRSM 50 Verisyse myopia 5.0 —5 mm optic – convexity correction: 0.8 mm

REFRACTIVE CORRECTION OF MYOPIA

Example

(Verisyse with 5 mm optic)

Patient data: spectacle correction: –14 D K-values: 41.0/43.0 D – mean: 42.0 D Equivalent to a K value of: 8.22/7.83 mm

Corrected anterior chamber depth: 3.9 mm minus 0.8 mm = 3.1 mm

Lens for implantation: VRSM 50 Refractive power of lens: –14.28 D

The VerisyseTM VRSM 50 with an optic diameter of 5 mm has a distance of 0.8 mm to the natural lens. For this reason, the anterior chamber depth has to be corrected by 0.8 mm in order to calculate the ACL value.

Calculation of Refractive Power of Lens for Hyperopia

Example

(VerisyseTM with 5 mm optic)

Patient data: spectacle correction: +7 D K-values: 41.0/43.0 D – mean: 42.0 D Equivalent to a K value of: 8.22/7.83 mm

Corrected anterior chamber depth: 3.4 mm minus 0.6 mm = 2.8 mm

Lens for implantation: VRSH 50 Refractive power of lens: 9.2 D

Note

Pre-existing astigmatism cannot be corrected with a spherical phakic Verisyse IOL. More minor degrees of