DR. GAUREE GATTANI

PHAKIC IOL

Phakic IOLs

Artificial lenses implanted in the anterior or posterior chamber of the eye in the presence of the natural crystalline lens to correct refractive errors

Limitations of laser refractive surgery - high ametropia - irreversibility - permanent damage to cornea

History

1889 - Clear lens extraction for the correction of myopia - Fukala in Austria/Germany : “Fukala Surgery” - abandoned due to complications1950s - correcting myopia by inserting a concave lens into the phakic eye1988 - Baikoff : anterior chamber angle-fixed IOLMid 1980s - Posterior chamber phakic IOLs : Fyodorov1991 - Artisan-Worst iris claw lens

Angle-supported Baikoff ZB5M (left) and the NuVita MA20 (right).

Iris-fixated Verisyse lens in situ.

Posterior chamber phakic refractive lens for myopia (top) and hyperopia (bottom).

Posterior chamber sulcus supported implantable contact lens.

Indications

Stable refraction (less than 0.5D change for 6months)    Clear crystalline lens    Ametropia not suitable/appropriate for excimer laser surgery    Unsatisfactory vision with/intolerance of contact lenses or spectacles    Anterior chamber depth greater than or equal to    - 3.2mm for the iris-claw lens and angle-supported PIOLs  - 2.5mm for posterior chamber PIOLs    A minimum endothelial cell density of - ≥3500 cells/mm2 at 21years of age - ≥2800 cells/mm2 at 31years of age - ≥2200 cells/mm2 at 41years of age    - ≥2000 cells/mm2 at 45years of age or more    No ocular pathology (corneal disorders, glaucoma, uveitis,

maculopathy, etc.)

Advantages

Large range of myopic, hyperopic, and astigmatic refractive error   

Allows the crystalline lens to retain its function preserving accommodation   

Excellent visual and refractive results (induces less coma and spherical aberration than LASIK)

Removable and exchangeable    Frequently improve BCVA in myopic eyes by

eliminating minification effect of glasses   Results are predictable and stable   Flat learning curve

Disadvantages

Potential risks of an intraocular procedure   Nonfoldable models require large incision that

may result in high postoperative astigmatism   Highly ametropic patients may require additional

photorefractive surgery (“Bioptics”)    May cause irreversible damage to natural lens

and corneal endotheliumImplantation in hyperopic patients can be followed

by loss of BSCVA due to loss of magnification effect of glasses  

IOL power calculation

Phakic anterior chamber (AC) lens - central corneal curvature (power) – keratometry (K) - anterior chamber depth - patient refraction (preoperative spherical equivalent)Posterior chamber phakic IOL power - corneal thickness and axial length are also taken into consideration

It is same as transferring the pre-operative spectacle power somewhere between the back surface of cornea and front surface of crystalline lens.

Consider the optical system as consisting of three powers: Spectacle correction Cornea IOL

The object and image vergence are defined as:

L= n/l ; L’=n’/l’

Then for spherical surface of the lens with radius of curvature r, the Power is defined as:

•F =(n’-n)/rLens maker formula: L’=L+FObject vergence L= n/ (b-d)Image vergence L’ = n/(a-d)FIOL = L’-L = n/ (a-d) – n/ (b-d)Fs

Investigations

Unaided and best corrected VAAnterior and Posterior segment evaluationwhite-to-white (w-w) measurement High-frequency (50MHz) ultrasound

biomicroscopy Corneal endothelial cell count

Artemis high-frequency (50 MHz) 3D-digital ultrasound imaging of the anterior segment. Red arrows indicate angle-to-angle distance; yellow arrows indicate sulcus-to-sulcus distance.

Deciding the size

AC angle supported IOL - length of IOL: 11.5 to 14 mm with 0.5mm intervals - w-w measurement - significant inaccuracies - intraoperative AC sizer - Anterior segment OCT

AC Iris-Fixated Phakic IOLs - one-size-fits-all length - 8.5 mm Posterior Chamber Phakic IOLs - w-w measurement plus 0.5mm - UBM and AS OCT to measure - sulcus-to-sulcus distance

AC Angle supported Phakic IOL

AC Angle supported Phakic IOL

rigid PMMA IOLsfoldable hydrophilic acrylic IOLs

Rigid PMMA angle-supported ZSAL-4 lens.

Foldable hydrophilic acrylic angle-supported Vivarte lens.

Rigid PMMA angle-supported Phakic 6 lens.

Foldable hydrophilic acrylic angle-supported I-CARE lens (A and B).

Ultrasound biomicroscopy (UBM) showing the position of the haptic in the anterior chamber angle (C).

Foldable “two parts” (Silicone optic/PMMA haptics) Kelman-Duet lens (A). The haptics are implanted initially through a small incision

(B), then the optic is injected (C). The complex optic-haptics is assembled inside the anterior chamber (D).

Procedure

Topical pilocarpinetopical or peribulbar anesthesiaIncisioncohesive viscoelastic lens is introduced , footplate is inserted

in the iridocorneal angle, second haptic is then placed, lens is then rotated in place

peripheral iridectomy incision is closed

Complications

Haloes and glarePupillary ovalizationEndothelial damageElevation of intraocular pressureUveitisCataractRetinal detachmentRarely - Urrets-Zavalia syndrome,

malignant glaucoma, endophthalmitis

Pupil ovalization 2years after implantation of an angle-supported phakic IOL (A).

At 5years, progressive ovalization was observed and the lens was explanted (B).

IRIS-FIXATED PHAKIC IOL

IRIS-FIXATED PHAKIC IOL

midperipheral fixation by a claw mechanism

Veriseye lens

Artisan/Verysise lens. Detail of the mid-

peripheral iris stroma enclavated by the haptic

claw.

Artisan/Verysise lens {FDA-approved models}

(A) 204 (6.0 mm optic) and (B) 206 (5.0mm optic) forthe correction of myopia.

(A) Foldable iris-fixated Artiflex lens.

(B) Foldable iris-fixated Artiflex lens.

Indications of Iris Claw lens

Treatment of refractive errors after penetrating keratoplasty.

Treatment of anisometropic amblyopia in children.

Secondary implantation for aphakia correction.Treatment of refractive errors in patients with

keratoconus.Correction of progressive high myopia in

pseudophakic children, andpostoperative anisometropia in unilateral

cataract patients with bilateral high myopia

Procedure

topical pilocarpineTopical / peribulbar anaesthesiaIncision, viscoelasticsIOL insertionEnclavation Closure of incision

Enclavation spots are marked on the cornea to guide fixation.

The incision is enlarged to the appropriate size.

Blunt iris entrapment needles are used to create a fold of midperipheral iris tissue through vertical movement of the needle.

B) The foldable Artiflex (Veryflex) lens is introduced vertically with a special spatula through a clear corneal incision.

The foldable Artiflex (Veryflex) lens is introduced vertically with a special spatula through a clear corneal incision.

Complications

Glare and haloesAnterior chamber inflammation/pigment

dispersionEndothelial cell lossGlaucomaIris atrophy or dislocationCataracthyphema, retinal detachment rarely

Poorly fixated Artisan lens with pseudophakodonesis causingchronic uveitis

Note the ciliary congestion

Artisan lens dislocation after blunt trauma

After relocation

Posterior Chamber Phakic IOL

Posterior Chamber Phakic IOL

Implantation of a phakic IOL in the prelenticular space

Materials: Silicone Collamer Hydrophilic acrylic

Posterior Chamber Phakic IOL

Properties desired in the IOL are:allow permeability of nutrientscirculation of aqueous humornot cause crystalline lens or zonular trauma.

Silicone IOL

The PRL is a hydrophobic silicone single-piece plate design IOL with a refractive index of 1.46.

Mechanical touch, impermeability of nutrients, and stagnation of aqueous flow without the elimination of waste products cataract formation

Changes its vaulting to avoidThe new models (PRL-100 and 101 (myopia), and PRL-200

(hyperopia), which are claimed to float in the posterior chamber with its haptics resting on the zonules, decreased the incidence of cataract formation to almost zero.

But complications, such as lens decentration and zonular dehiscence with dislocation of the lens into the vitreous cavity.

Implantable Collamer Lens

In 1993, a posterior chamber phakic IOL made of hydrophilic flexible material collamer, which is a copolymer of HEMA (99%) and porcine collagen (1%), was developed.

Despite these characteristics, cataract formation and glaucoma are still the main complications of this lens

high biocompatibility and permeability to gas , metabolites

free space left

between the IOL and the

crystalline

lens,

Avoid the development of

cataracts.

Procedure

MydriasisTopical or peribulbar anesthesiatemporal clear corneal tunnelViscoelasticFoldable IOL insertion into AC (with an

injector or with forceps)Check orientationPlacement of footplates below irisIridotomyClosure of incision

A posterior chamber lens is folded (A) and inserted through a small incision (B) with a forceps.

At the end of the procedure a peripheral iridectomy is performed.

Complications

Glare and haloesCataractPigmentary dispersion and elevated

intraocular pressureDecentrationEndothelial cell damage

Glare and haloes

Incidence 2.4-54.3%. The frequency of haloes

was higher when the ICL’s optical zone size was small. The rate of haloes correlated to the difference between

the scotopic pupil diameter and the optical zone size. In the ICL FDA study, approximately 8.5% of the

patients had glare and haloes postoperatively. The authors concluded that the incidence of glare,

haloes, double vision, night vision problems, and night driving difficulties decreased or remained unchanged from before the operation after ICL surgery.

Cataract

As a result of trauma to the crystalline lens during the implantation procedure

Due to long-term contact between the IOL and the crystalline lens.

Metabolic disturbancesThe majority of these cases were anterior

subcapsular.Explantation of the ICL is easily performed through the

same incision

Piment Dispersion Syndrome

Rubbing at the optic–haptic junction on the posterior face of the iris iris abrasion release of pigments into the aqueous humor.

The pigment deposits had no visual consequences as they were located at the optic–haptic junction rather than the central optic.

If PC phakic IOL is: Undersized decreased vaulting contact between the IOL

and the crystalline lens Too large iris friction pigmentary dispersion

This is one important reason for adequately measuring the sulcus-to-sulcus distance.

Pigmentary deposits are seen in the angle in an eye with a posterior chamber phakic intraocular lens.

Decentration

Since the PRL lens floats in the posterior chamber with the haptics resting on the zonular apparatus, zonular erosion by the IOL haptics seems to be the main mechanism for IOL instability and dislocation.

Bioptics

The combination of phakic IOL implantation followed by LASIK in patients with extreme myopia or hypermetropia and high levels of astigmatism.

When an anterior chamber phakic IOL is planned to be combined with LASIK, the corneal flap can be created just prior to the insertion of the lens; then, at a later time, usually after 1month, the flap is lifted for laser correction of the residual ametropia. This two-step technique was called adjustable refractive surgery (ARS) by Guell.

The rationale in performing the flap first is to avoid any possibility of contact between the endothelium and the IOL during the suction and cut for the LASIK procedure.