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You are watching: Which of these conditions would be treated with phakic iols

StatPearls . Treasure Island (FL): StatPearls Publishing; 2021 Jan-.


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Continuing education Activity

The phakic intraocular lens (IOLs) is a an innovation that broadens the range of refractive surgical procedure to cover greater degrees of myopia, hyperopia, and astigmatism that were formerly not feasible to treat. It gives an effective solution to high refractive errors in candidates who space not suited for corneal refractive treatments. This task reviews the evaluation and also management the patients with high myopia undergoing treatment through phakic IOLs and also highlights the role of the interprofessional team in improving treatment for patients v this condition.

Objectives:
Describe the epidemiology of myopia and the development of phakic IOLs.
Summarize the management considerations for patients through high myopia using phakic IOLs.
Review the usual complications that phakic IOLs supplied in high myopia.
Summarize the prestige of collaboration and communication amongst the interprofessional team to improve outcomes for patients affected by high myopia v phakic IOLs.
Access complimentary multiple choice questions ~ above this topic.


Introduction

Myopia is a condition of nearsightedness in i beg your pardon parallel rays indigenous infinity space focused prior to they with the retina through the accommodation at rest. Various refractive surgical actions are offered to treat myopia specific laser in situ keratomileuses (LASIK), photorefractive keratectomy (PRK), laser-assisted subepithelial keratectomy (LASEK) or Epi-LASEK, intracorneal ring segment (ICRS or INTACS), clean lens exploit (CLE) or phakic intraocular lens/IOL (PIOL) implantation.

Excimer laser actions are efficient for the treatment of low and moderate myopia. Intracorneal ring segments may be offered to treat short myopia, yet their results are highly unpredictable. Extremely ametropic eyes room not perfect candidates for laser measures or ICRS and require alternatives such as phakic IOL implantation. This gives for a better quality that vision not easily accessible with various other techniques. The conservation of accommodation and also minimal manipulation that the crystalline lens are other advantages.<1>

History of Phakic IOLs

In 1953, Benedetto Strampelli implanted one anterior room IOL (ACIOL) for the mediate of major myopia in phakic eyes. These did not come into practice due come endothelial complications, iritis, pupillary block, and glaucoma. Joaquin Barraquer introduced an IOL through elastic loops far better adaptable to the anterior chamber for myopic phakic eyes. This IOLs additionally caused similar complications and thus did not become very popular.<2>

Over time phakic AC-IOLs significantly improved. Crucial contributions in the advancement of phakic IOL’s encompass the donation by:

Fechner and Worst – iris addressed IOLs <3>

Baikoff – angle supported AC-IOLs <4> 

Fyodorov - posterior room IOLs (PC-IOLs) v ciliary groove fixation <5>


Etiology

The normal process of emmetropization starts with hyperopia in the infancy of roughly +2 D. Throughout the very first two year of life, and there is a fast decrease in this hyperopia to approximately +1 D. The shift towards emmetropia continues in ~ a slower rate after 3 years until about six years of age.<6>

This is concerned the rate of expansion of the eyeball. In myopic individuals, the axial length increases at a much much faster rate. Axial myopia is an increase in axial length and thinning that the sclera the is due to increased collagen degradation and also reduced collagen synthesis.<7> Myopia might be categorized together mild myopia (0 D come −1.5 D), moderate myopia (−1.5 D come −6.0 D), and high myopia (−6.0 D or more).<8> Pathological myopia is normally seen with -8 D or an ext and is linked with common retinal and also macular degeneration.<8>

Various environmental factors play a function in the development of myopia, back no clean association has actually been created yet. Several day-to-day activities, together as diminished outdoor time and increased near work activities, including increased use of electronic devices, play a contributory duty in the development of myopia.<9> Other proposed causes include genetic predisposition, low everyday light exposure, and diet.<10>


Epidemiology

There is a large variation in the prevalence of myopia in different regions and also ethnic groups.<11> The prevalence of myopia have the right to be approximated to be approximately 70% come 90% in Asia, about 30% to 40% in Europe and also America, and 10% to 20% in Africa.<12> 

High myopia contributes approximately 10 to 20% of the situations in young adults.<13> The significant risk components identified are intensive education and learning and restricted outdoor time.<13> Myopia development in eastern children is much faster than in west children.<14> No sex predilection has actually been report in the prevalence of myopia.  

The morbidity caused because of vision disability from uncorrected myopia in addition to irreversible visual loss from myopia-related symptom warrants accurate worldwide estimates that the situation and temporal trends vital for planning management.<9> 

The portion of moderate and high myopes opting for refractive surgical procedure is roughly ten times and also sixteen times more than short myopes, respectively.<15>


History and Physical

Preoperative background for implantation that a phakic IOL should start with establishing realistic expectations for the procedure. A complete history of the refractive stability, comfort, and also satisfaction through glasses or call lenses, the age of first spectacle correction, any background of amblyopia or strabismus must be taken. Frequent adjust in the prescription of glasses needs to be evaluated in detail for problems like keratoconus or pellucid marginal degeneration.

Patient’s Age: A young aged urged patient that has completed refractive stability and has less than 0.5 D that refractive change in 1 year is perfect candidate for phakic IOL.<16> The principle of presbyopia demands to be clearly explained while counseling a patient for any kind of kind that refractive surgery.<17>

Pupil Size: A scotopic pupil size bigger than the optical zone that the implant would lead to glare and halos, which might be severely debilitating in the postoperative duration and might even demand explantation of the IOL.<18>

A finish corneal review with endothelial cell count and topography is important prior to planning a phakic IOL implantation.

A substantially deep anterior chamber is mandatory because that a phakic IOL. Many phakic IOLs need an anterior chamber depth that at the very least 3 mm.<19>

Relative Contraindications for Phakic IOLs Include:<16>


Cataract
Chronic uveitis
Low endothelial cabinet count

Indications for FDA (Food and also Drug Administration, USA) authorized Phakic IOLs:<20> 

Visian ICL: mediate of myopia indigenous -3.0 come -15.0 D and also reduction the myopia native -15.0 come -20.0 D with much less than 2.5 D the astigmatism at the spectacle aircraft in patients aged 21 to 45 years with an anterior room depth of much more than 3.0 mm and refractive security within 0.5 D for one year prior to implantation.

Artisan/ Verisyse IOL: correction of myopia from -5.0 to -20.0 D with less than 2.5 D the astigmatism in ~ the spectacle plane in patients aged much more than 21 years through an anterior room depth of more than 3.2 mm and also refractive stability within 0.5 D for six months before implantation. 

Contraindications because that FDA authorized Phakic IOLs:<20>

Visian ICL: Anterior room angle less than grade 2 established by gonioscopy, pregnant or parenting females, endothelial density in the range 1900 to 3875 cells/mm^2 relying on age.

Artisan/Verisyse IOL: any angle abnormality, iris abnormalities such as peaked pupil or elevated iris margin, pregnant or nursing females, endothelial thickness in the range 2000 to 3550 cells/mm^2 depending on age.


Evaluation

The following components need come be thought about in the preoperative evaluation:

Refraction: Both manifest and also cycloplegic refraction have to be performed. The best-corrected visual acuity in the undilated and cycloplegic state (after performing cycloplegia with homatropine or tropicamide) should be recorded.

Anterior room depth (ACD): most phakic IOLs need ACD the at least 3 mm.

Anterior chamber angle and gonioscopy: Gonioscopy must be carry out preoperatively to identify narrow or abnormal angles, which might lead to more postoperative narrowing and second glaucoma after phakic IOL implantation. The accepted selection of iridocorneal angle aperture because that phakic IOL implantation is much more than or same to 30 degrees, which corresponds to Shaffer great 3 and 4 or Scheie grade 0 and also 1.<21>

Corneal topography need to be performed as is done in all refractive workups.

Specular microscopy: consisting of specular microscope measurement of endothelial cell count, cell form (polymorphism), and variation in cell dimension (polymegathism). Phakic IOL implantation leader to endothelial cabinet loss in the postoperative period, more so because that the anterior chamber IOLs (ACIOLs) and so a healthy preoperative endothelium with a cell count of at least 2300 per millimeter square must be ensured.<16><22>

Sulcus come sulcus (STS) measurements: This is necessary for sizing of the phakic IOL and measurement the lens vault (distance in between the posterior surface of the IOL and also the anterior lens capsule) in case of a phakic posterior room IOL (PCIOL). An approximate calculation the the dimension of the IOL relying on the vault is made making use of the white to white (WTW) measurement by adding 0.5 mm to the measured worth in myopes and subtracting 0.5 mm in hyperopes. WTW might be measured making use of calipers, scanning cleft topography, digital caliper, Scheimpflug-based devices, ultrasound biomicroscopy (UBM), or digital ultrasounds.<23><24><25> As the measurement values may vary depending upon the an approach used, it is way to usage an mean of the values. It has been argued that directly measuring the STS diameter using ultrasound biomicroscopy or an extremely high frequency (VHF) digital ultrasound may be a much more reliable method for the dimension estimation of phakic IOLs.<26><27>

Ideal vault size for phakic posterior room IOLs is 1 to add or minus 0.5 of the corneal thickness, i beg your pardon is in the range of 250 to 750 microns.<28>

IOL strength calculation: Biometry, keratometry, anterior chamber depth (ACD), lens thickness, preoperative refraction have to be correctly measured, and also the ideal formula applied. Van der Hejde nomogram might be supplied for IOL power calculation.<29>

Peripheral retinal examination and also laser the retinal breaks are crucial to protect against complications the retinal detachments in the postoperative period, especially as pupil dilation remains restricted with anterior room IOLs.


Treatment / Management

Treatment the high myopia deserve to be done using spectacles, call lenses, keratorefractive procedures, CLE, and also phakic IOLs Spectacles may induce aberrations in situations of high myopia, and also the patient may for this reason be intolerant to their use. Call lens use is cumbersome, and they must be readjusted and cleaned periodically, making castle unsuitable for countless candidates. Keratorefractive procedures transform the normal asphericity and shape of the cornea and also may result in various complications in the postoperative period, such as haze (PRK) or flap connected complications and also ectasia (LASIK). Moreover, the patient demands to fit into the corneal topography and also thickness criteria to have the ability to undergo these procedures. CLE leads to a loss of accommodation and also thus is unsuitable because that young age patients.<30><31> Also, CLE in high myopia may be connected with an raised risk that retinal detachment.<32>

Preoperative laser iridotomy or intraoperative operation iridectomy requirements to be performed to prevent pupillary block in the postoperative duration for the anterior room IOLs, and also the posterior chamber PRL and Visian ICL 4 models.<33>


Prognosis

Success through the lens depends greatly on accurate preoperative evaluation, which identify the vaulting in instance of a PCIOL and also sizing in instance of one ACIOL.<34> Newer models the IOLs have actually incorporated attributes to minimize contact with iris and also conform better to the geometry of the eye.<35>

Refractive outcomes are good, and also with optimum calculations, this IOLs can efficiently correct myopia of up to 20 dioptres (D) with good results. 

Studies have shown PIOLs come have good postoperative visual outcomes such together a median postoperative uncorrected intuitive acuity (UCVA) of better than 20/40 in the bulk of patients.<36><37>


Complications

Endothelial cell loss: that is much more common through ACIOLs. This may lead to corneal decompensation, and in excessive cases, explantation that the IOL may be required when the endothelial counting drops listed below 2000 cells every millimeter square. A 1% mean yearly reduction in endothelial cabinet count has actually been viewed in angle addressed IOLs once the distance between the corneal endothelium and also the sheet of the IOL is 1.43 mm.<38> This rises to 1.7% once the street reduces to 1.2 mm and also is minimal as soon as the distance is 1.66 mm.<38>

In a study on the implantation the anterior room phakic IOLs, the NuVita IOL report 2.35% endothelial cell loss in ~ one year and was for this reason withdrawn.<39> average endothelial cabinet loss at one year, as checked out in different studies on various other models, to be 3.86% in ZSAL-4,<40> 1.83% in iris fixated IOL"s,<41> 2% in IPCL<42>, 0.9% in ICL.<43>

In a 12 year retrospective study on 144 eyes implanted with ICL, Moya et al. Report 6.46% surgically induced endothelial cell loss throughout the very first year, past which an median yearly decrease rate of 1.20% was noted.<44>

IOL rotation happens as result of inappropriate sizing. May lead to induced astigmatism in instances of toric IOLs.

Pigment dispersion may result in lens deposits. Usually, no intervention is required.

Chronic inflammation and also uveitis are more common through ACIOLs.

Pupil distortion is seen in ACIOLs. This may result in intractable glare and also maybe cosmetically unacceptable.

Pupillary block and glaucoma: Pupillary block might occur as result of inappropriate vaulting in the instance of PCIOLs. It may resolve after ~ pupil dilation and also use of pressure-lowering agents, but the definitive treatment is the production or enhancement of a previously developed peripheral iridotomy. Kept viscoelastic material may additionally cause elevated intraocular press (IOP). Angle fixed IOLs may block the angles and lead to a climb in IOP.

Glare and halos are seen once the scotopic pupil size is better than the optic the the IOL. Miotic agents might be given for resolution.

Cataract development occurs in short PIOL vault or undersized PCIOL. This is greatly in the kind of anterior subcapsular opacities that develop due to the press of the IOL top top the crystalline lens. Lens material additionally plays a role. Silicone in PRL may predispose more come cataract development than Collamer of ICL.<45><46><47> 

In a 5-year retrospective study, Brar et al. Report that, in a complete of 957 eyes, significant anterior subcapsular cataract (ASC) requiring explantation arisen in four eyes (0.4%).<48> In an eight-year monitor up the 41 eye implanted through V4 ICL by Igarashi et al., asymptomatic ASC was reported in 4 eyes (9.8%).<49> Sanders et al., in their examine on 106 eyes with -12.00 D or an ext of preoperative myopia report clinically far-reaching cataracts in 7 eyes (6.6%), vice versa, no cataract developed in 420 eyes v preoperative myopia less than -12.00 D. They hence concluded the a higher degree the baseline myopia more frequently predisposes to cataract formation.<50>

As most instances are high myopes, over there are possibilities of rhegmatogenous retinal detachments (RRD) much more than emmetropic eyes, in the selection of 0.7% come 3.2%.<51> However, together eyes with high myopia are already predisposed to retinal detachment, and also the combination of PIOL v RRD needs additional evaluation.


Deterrence and also Patient Education

Patients need to be aptly counseled preoperatively with complete knowledge that all easily accessible options and realistic expectations collection for postoperative outcomes in addition to necessary details on the feasible complications.


Pearls and Other Issues

Any residual refractive error may be corrected utilizing bioptics, i m sorry is the mix of one intraocular procedure v a keratorefractive procedure. Pseudophakic ametropia may likewise be corrected with the assist of phakic IOLs.<52>


Enhancing health care Team Outcomes

A high myopia-patient may generally present come a primary healthcare provider, so the patient should be counseled appropriately about the miscellaneous treatment alternatives available. The patient have to be evaluated totally by one optometrist and efficiently operated up by one ophthalmic technician as the success of the procedure largely depends top top the preoperative measurements.

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Proper factor to consider needs come be provided to any medical problem the patient might be having and should receive treatment for the same. The nurses are also an essential members that the interprofessional group as they monitor the patient"s an essential signs and also assist with the education and learning of the patient and also family and compliance on follow up. Pharmacists deserve to ensure ideal postoperative dosing that medication. This collaborative, interprofessional method to treatment can certain optimal patient outcomes.