Phakic IOL Hyperopia Treatment & Management
- Author: Daljit Singh, MBBS, MS, DSc; Chief Editor: Hampton Roy, Sr, MD more...
Cycloplegic refraction is most useful.
If a substantial difference exists between the manifest refraction and the cycloplegic refraction, then calculate as follows: cycloplegic refraction minus 0.5 multiplied by (cycloplegic refraction minus manifest refraction).
IOL power calculation
The van der Heijde nomogram may be used to calculate the iris claw lens power.
The Feingold formula (proprietary) may be used for a precrystalline lens implant.
Culture 2 days before surgery, then administer local antibiotic drops.
The most popular medicine is tobramycin 0.3%, 1 drop, 6 times a day.
Laser peripheral iridotomy
Fifteen days before the posterior chamber phakic lens implant, consider performing 2 Nd:YAG iridotomies, 90° apart.
This procedure is most useful when the iris is light colored; it may not work when the iris is brown or dark.
Preoperative eye preparation depends on the type of IOL to be implanted.
Precrystalline lens: Dilate the pupil with homatropine (2%) and phenylephrine (5%), instilled 3 times at 15-minute intervals, starting 1 hour before surgery.
Iris claw lens: Contract the pupil with 1% pilocarpine drops, instilled at 15-minute intervals, starting 45 minutes before surgery.
Nonsteroidal anti-inflammatory drug (NSAID) drops are instilled 2 times before surgery to minimize inflammation.
Some patients prefer general anesthesia, but most patients opt for local anesthesia.
Surface leading to intraocular anesthesia: Use preservative-free 2% intraocular lidocaine.
Local anesthesia: Use 2% lidocaine with 7.5 U/mL hyaluronidase. It may be used as a peribulbar anesthesia or for facial nerve block leading to retrobulbar block. The local anesthesia is given 10 minutes before surgery. Apply orbital compression to make the eye soft and to reduce orbital pressure.
Preparation of the surgical field
Use 5% povidone. Paint the periorbital skin with iodine, then apply the same solution 2-3 times to the lid margin and the conjunctival fornices. Then, the eye is washed with saline.
Exposure of the surgical field
An eye speculum may be used.
The upper and lower lid sutures, as well as superior rectus sutures, are applied in place of the speculum. Adhesive plastic, applied to the surface of the eyelids, is used to pull the eyelashes.
Making small incisions
One 0.6 mm side port is needed to inject viscoelastic material in the anterior chamber. This injection is started at the opposite limbus. As the aqueous drains, it should be replaced with viscoelastic agent. The depth of the anterior chamber is not reduced at any time.
For iris claw lens implantation, 2 side ports are needed to introduce the instruments, which fix the iris to the claw.
Making the larger incision to insert the IOL
The size of this incision depends on the type of IOL to be implanted.
For a soft precrystalline lens, make a 3.2 mm clear corneal incision on the steep meridian.
For an iris claw lens, the width of the incision depends on the diameter of the optic (4.25-5 mm). The incision may be made at the limbus or in the clear cornea. If a pocket section is made, it will allow a wound closure without sutures.
For a foldable iris claw lens (Artiflex), make a 3.2 mm incision.
Insertion of foldable lens in the precrystalline space
The lens is introduced with angled-suture forceps, then it is positioned behind the iris on a horizontal axis with a cyclodialysis spatula.
The lens is manipulated to center the optic on the pupil.
The viscoelastic material is removed from the anterior and posterior chambers with an aspiration syringe (24-gauge cannula).
The anterior chamber is washed thoroughly with saline.
The pupil is contracted with intraocular acetylcholine 1%, carbachol 0.01%, or pilocarpine 0.5% solution.
The incision is closed by hydrating the corneal incisions. A suture rarely is needed.
Insertion of an iris claw lens
The main incision is made at the 12-o'clock position. The width is equal to the size of the optic, which may be 4.25-5 mm. The side incisions are 1.5 mm wide.
The hyperopic convexo-concave polymethyl methacrylate (PMMA) iris claw lens is inserted vertically. The lens is rotated inside the viscoelastic-filled anterior chamber; therefore, both claws of the lens are placed horizontally.
Fixating the iris claw lens
Fixating the iris claw lens is a bimanual procedure.
A vertically holding lens forceps, which enters the anterior chamber through the main incision, centers the optic on the pupil and holds it steadily.
A thin forceps is introduced from the side incision and grasps the iris close to the claw, passing a fold of the iris through the claw, and results in fixing one of the claws.
Both instruments are withdrawn, and the surgeon changes hands for holding each tool.
The anterior chamber is again deepened with viscoelastic material, and the lens-fixation instruments are reintroduced.
The fixation of an Artiflex lens is basically the same technique. This lens has to be introduced in the anterior chamber in a vertical direction with a special spatula. The lens is then rotated to a horizontal position for the iris claw fixation.
Second claw-fixation maneuver
The second claw-fixation maneuver is performed through the incision on the opposite side.
A peripheral iridectomy is performed at 12-o'clock position.
The viscoelastic material is aspirated through the 3 incisions, then the anterior chamber is irrigated gently and inflated with air to remove all viscoelastic material.
Closure of the incision line
For a pocket incision, the apposition may be achieved by 1-2 very superficial sutures. Alternatively, a large air bubble may be left inside the anterior chamber to effect an apposition.
If the limbal incision was made without a pocket, a regular closure of the incision line should be performed. An operating keratoscope is used to monitor the corneal curvature at the end of the operation.
End of surgery
Subconjunctivally inject 20 mg of gentamicin and 2 mg of dexamethasone.
Apply a sterile pad and a protective shield.
Monitor the patient as with any other IOL surgery. In particular, carefully look at the incision line and be watchful of the IOP and any inflammation.
The first examination is performed 8-12 hours after the surgery.
Protecting the eye from injury: The restrictions are less rigid for posterior chamber lens cases. Patients should use protective goggles during the day and a protective shield at night. Do not bump the eye when applying eye drops.
Cleaning the eye
The corners of the eye and the surrounding area may be cleaned with sterile cotton swabs.
The patient should be careful when bathing.
Using the eye
No restrictions exist (eg, watching television, reading).
No restriction on walking exists.
The patient should avoid heavy exercise for 2 weeks.
Contact sports should be avoided for 2 months.
Swimming is allowed after 2 months, but diving should be avoided.
Rubbing of the eye
This should be avoided throughout life regardless of the lens design.
The patient can drive a car after 1-2 days.
Early postoperative care
On postoperative days 1, 2, 3, and 7, perform slit lamp examination, and record any uncorrected or corrected visual acuity and IOP.
Long-term follow-up care
Patients should receive follow-up care after 1 month, 6 months, and once annually thereafter
The pupil is dilated at every visit.
Use slit lamp examination to find evidence of inflammation, pigment dispersion, adhesion formation with the uveal tissues, and touch to the anterior lens capsule. Look for any opacification of the crystalline lens.
Perform a careful refraction.
Regularly monitor the endothelial cell density with specular endothelial microscopy.
Use gonioscopy to look for peripheral anterior synechiae formation. Look for the presence of pigment that is derived from the iris and the ciliary body.
Observe any crowding of the angle that is due to the IOL behind the iris.
Precrystalline lens phakic implant
Early problems can develop within 24 hours of the operation. Pupillary block glaucoma may develop because of the blockage of previous laser iridotomies or viscoelastic material residue in the posterior chamber. The vasovagal response causes pain, blurred vision, and systemic symptoms. Red eye, corneal edema, shallow anterior chamber, dilated pupil, and a marked rise in IOP occur.
If the condition does not respond to systemic therapy with acetazolamide, hyperosmotic agents, local miotics, and beta-blockers, opening the eye under general anesthesia to explant the lens is recommended. In 2-3 weeks, the eye might regain the earlier corrected vision.
Specular endothelial microscopy may reveal a substantial loss of endothelial cells. The closure of the peripheral iridotomies and pupil block glaucoma can occur after 1 or more weeks. Such cases may be treated by a repeat laser iridotomy, surgical peripheral iridectomy, or a lens explantation.
An anterior subcapsular cataract may form due to contact with the natural lens. A small IOL has greater chances of having direct contact with the crystalline lens. Uveitis also can occur in an acute or a chronic form. Pigment dispersion may be seen on the artificial lens or the natural lens. Late glaucoma may occur because of crowding of the angle and pigment deposits in the angle. In some cases, the pupil may become partially dilated and not respond to the usual miotics. The implanted lens may dislocate due to the dissolution of the zonular fibers.
Iris claw lens
Early dislocation is due to inadequate fixation. Early or late anterior uveitis can occur. If a patient compulsively rubs the eyes and produces recurrent endothelial touch, late corneal decompensation can occur. Postoperative endophthalmitis has not been reported; however, since it is an intraocular procedure, the possibility cannot be excluded.
Outcome and Prognosis
A successful IOL procedure does not cause a loss of best-corrected visual acuity. The vision improves from day 1. Many patients with amblyopia may recover partially or completely in several months.
A sutureless procedure exists for inserting a soft, biocompatible lens. The optical correction is good. Although empirically measured from a formula (white-to-white diameter minus 0.5 mm), this IOL size works in most cases.
An extremely small lens will rub against the lens epithelium, iris pigment epithelium, and ciliary epithelium. A lens that is larger than required lifts in the middle and develops more than desired intimate contact with the posterior surface epithelium of the iris. In some cases, especially eyes with dark irises, the iridotomies might fail to remain patent, and the IOP may rise. A surgical iridectomy is often necessary in these situations; sometimes, the IOL must be removed.
A regular follow-up visit is essential to detect cataract formation, in which event the lens must be explanted with appropriate treatment for the cataract. With increasing age, consider crowding of the angle and increasing IOP.
An ophthalmologist who has received training to implant such lenses should perform an iris claw lens.
Although it may not be cosmetically acceptable by some patients with light-colored irises, a surgical iridectomy always is performed. Early dislocation of the lens is rare but indicative of improper fixation. Late dislocation is not reported. The lens avoids the angle of the anterior chamber, never touching the crystalline lens, posterior pigment layer of the iris, or the ciliary processes. Therefore, the lens is devoid of the above complications in connection with the posterior chamber lens. The edge and the optic of the IOL are far removed from the corneal endothelium; under normal circumstances, touch does not occur. If a patient rubs the eye vigorously for any reason, an endothelial touch can occur. Many people rub their eyes during sleep.
The phakic iris claw lens has been used and well tolerated for 20 years. Even this long follow-up is not sufficient to address all the long-term safety concerns. If necessary, the lens is easy to explant (eg, natural cataract development). A regular follow-up examination is essential, with particular emphasis on counting endothelial cells on an annual basis. The lens is available in the United States under the name of Verisyse.
Future and Controversies
IOL implantation for phakic eyes is only one of many controversial modalities to alleviate hyperopia. Several attractions include the following:
Minimum surgical injury to the ocular tissues occurs, even though it means opening the eye and closing it after making a few manipulations.
Viscoelastic materials make lens implantation easy and safe, although the viscoelastic material should be removed thoroughly from the eye at the end of the surgery.
As long as surgical quality is not compromised, the optical results are highly predictable, immediate, and lasting.
No large investment is involved for beginning this kind of refractive surgery. It can be performed in the most remote corners of the world.
The ocular tissues tolerate and survive the presence of an IOL in a phakic eye. However, it will only survive if the lens implantation occurs as a one-time event and not as the beginning of a process, which may initially appear innocuous. Thus, every new modality, especially an IOL, must prove itself over a long period. In spite of the many modifications of posterior chamber lens designs, a stigma of cataract formation still exists.
It has been proven repeatedly that pressure or friction between the IOL and the ocular tissue damages this tissue. For this reason, a phakic lens in the posterior chamber suffers from certain serious flaws. The posterior chamber lens permanently positioned in narrowly confined space raises the following concerns:
What is the right size for the posterior chamber phakic lens? How is it realized that the selected lens is really the right size for a particular eye?
The IOL is thickest in the central area, and the pupillary margin of the iris naturally touches the crystalline lens. How can a posterior chamber phakic lens possibly avoid touching or rubbing both the posterior surface of the iris and the crystalline lens? It is inevitable that 1 of the 2 surfaces will be constantly touched or rubbed. What will be the consequences of such a friction over years? Decades? A lifetime? When raising this question, it is presumed that the surgery was flawless without immediate postoperative problems.
When discussing phakic posterior chamber lenses, only 2 structures (the iris and crystalline lens) usually are mentioned. A safety concern should exist for the delicate ciliary processes, its epithelia, and its vasculature. The plate haptic lens owes its survival to the support and leverage that it gets from there, so as to stay clear of the crystalline lens. Lifelong contact, pressure, and micropressure or macropressure/movements (pressing or rubbing the eye) adversely affect the integrity of the ciliary epithelia and the ciliary vasculature. For this reason, closely monitoring blood-aqueous barrier breakdown in this group of patients for months and years is important. Presently, this measure is not observed.
Reports have emphasized the accuracy of correction and the improvement of uncorrected visual acuity. However, the much larger issue, long-term tissue tolerance, is more significant than any short-term benefits (which some cite as justification for proliferating use).
In aphakic eyes, posterior chamber lens implantation in the sulcus was abandoned in favor of a more difficult, in-the-bag implantation. The reason is that sulcus-fixation leads to many unacceptable complications, which are produced in the roomy aphakic compartments by the sulcus-supported lenses. It is difficult to believe that sulcus-supported phakic lenses fare any better in a more restricted space (ie, the normal posterior chamber). Another responsibility is saving the crystalline lens from inadvertent damage, which leads to cataract formation.
In a group of patients who are prone to angle-closure glaucoma, nothing prevents the plate haptics of the phakic posterior chamber lens from pushing forward the iris periphery and crowding the angle.
The phakic posterior chamber lens is pushed intentionally into the space, so the ocular structures that bound the space catch the lens. This phenomenon is possible only if the lens is larger than the fixation space. A slightly smaller lens moves freely in the space and rubs against the crystalline lens. It logically follows that no lens design can perfectly fit an individual eye.
The iris claw lens is a pure iris support lens. The lens is smaller than the area where it is fixed. The ocular tissues cannot catch this lens (unlike the posterior chamber lens), so the lens is designed to catch the tissues (the anterior surface of the iris).
The surgeon who centers it controls the fixation site. The lens remains permanently placed unless it dislocates because of poor fixation or injury. The principle of iris fixation inside the claws was tested clinically on thousands of aphakic eyes over 9 years before the lens was redesigned for phakic eyes. These changes help the implant lens to stay clear of the natural crystalline lens and the corneal endothelium, but the principle of time-tested claw fixation remains the same.
The lens design permits it to stay far from the angle tissues and allows freedom to the pupillary movements. The lens floats in the aqueous humor, while fixated at 2 points. It totally avoids the narrow posterior chamber, which is surrounded by potentially reactive tissues. The iris claw lens has proven itself for a long time, both in aphakic eyes (>34 y) and phakic eyes (>25 y). Other lenses must surmount many difficult problems before they can become a serious alternative.
Hypermetropia is a childhood disease and is present at birth. Unequal refractive error or high refractive error can and does produce severe amblyopia. The youngest age for a phakic lens implantation in a patient with hyperopia has not yet been determined, considering that many patients with hyperopia have a shallow anterior chamber. Also, children are more prone to eye trauma than adults. Thus, phakic lenses for this important group of patients with hyperopia are contraindicated.
Refractive corneal procedures have come of age. Wave analyzed supported customized ablation (WASCA) has brought greater confidence in application and results.
Using MEL 70 excimer laser, during the course of 5 years, the author treated 69 patients with hyperopia (age range 5-68 y, average 24.6 y) with WASCA. The spherical error varied between 2 D and 11 D, with an average of 5.86 D. The cylindrical error varied between 0 D and 5 D, with an average of 0.84 D. The average follow-up period is 11 months. The final spherical error varied between -2.5 D and 6 D, with an average of -0.003 D. The cylindrical error varied between -1 D and 0 D, with an average of 0.08 D.
Preoperatively, the best visual acuity varied between 6/6 and 6/60, with an average of 6/26.56. Postoperatively, the best visual acuity varied between 6/6 and 6/60, with an average of 6/22.66. One patient lost 2 lines, and 12 patients lost 1 line. Among the rest, 32 patients had no change, 10 patients gained 1 line, 8 patients gained 2 lines, and 6 patients gained 3 lines.
One patient required the removal of the epithelium because of haze formation. Two patients had transient superficial punctate keratitis (SPK). Six patients had minor haze that disappeared over time. No cases of steroid glaucoma occurred.
In refractive laser surgery, the author finds many advantages. It is independent of the internal anatomy of the eye and is applicable to very young patients. One year of follow-up care is usually sufficient to determine that no more active follow-up care is needed for the rest of that patient's life. Some patients with very high hyperopia and with a favorable depth of the anterior chamber are best served with a phakic intraocular lens plus laser refractive surgery.
Amblyopia is common among hyperopes, especially in unilateral cases. Orthoptic and pleoptic exercises, which have proven useful, are not used widely to improve these patients. The goal of refractive hyperopia surgery should not only be freedom from glasses but also freedom from the clutches of amblyopia. Unfortunately, today's only effort to overcome amblyopia is patching. All other measures are avoided because they are costly. The fight against hyperopia should go hand-in-hand with the fight against amblyopia; only then will a universal interest in recognizing hyperopia exist.
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