eMedicine Specialties > Ophthalmology > Refractive Disorders

Myopia, Phakic IOL: Treatment

Author: Arun Verma, MD, Senior Consultant, Department of Ophthalmology, Dr Daljit Singh Eye Hospital, India
Coauthor(s): Daljit Singh, MBBS, MS, DSc, Professor Emeritis, Department of Ophthalmology, Guru Nanak Dev University, Amritsar, India; Director, Daljit Singh Eye Hospital
Contributor Information and Disclosures

Updated: May 16, 2008

Treatment

Medical Therapy

• Perform both manifest refraction and cycloplegic refraction.
• Conjunctival swab is taken for culture 2 days before surgery, after which topical antibiotics (tobramycin 0.3%) are started, 6 times a day.
• Preoperative drops: Preoperative eye preparation depends on the type of IOL to be implanted.
• Angle-supported lens and iris claw lens: Contract the pupil with 1% pilocarpine drops, instilled at 15-minute intervals, starting 45 minutes before surgery.
• Precrystalline lens: Dilate the pupil with homatropine (2%) and phenylephrine (5%), instilled 3 times at 15-minute intervals, starting 1 hour before surgery.
• Nonsteroidal anti-inflammatory drug (NSAID) drops are instilled 2 times before surgery.

Surgical Therapy

Nd:YAG laser peripheral iridectomy may be performed 1-2 weeks prior to a phakic lens implantation. This procedure prevents pupillary block in the postoperative period. The other alternative is to perform a manual iridectomy at the time of the phakic lens implantation.

Every phakic IOL demands meticulous care in the performance of the finest detail of implant surgery. There should be minimal surgical trauma. The incision lines should be meticulously closed. The protection of the endothelium with viscoelastics is of the utmost importance as is the complete removal of viscoelastics at the end of the surgery. Making the incision as well as closing the incision should be meticulous and should preferably not introduce an astigmatic error.

Preoperative Details

Preparation and anesthesia need detailed attention.

Anesthesia

• By mutual consultation, the patient and the surgeon can choose the type of anesthesia, whether topical, intraocular, local, or general.
• Surface anesthesia leading to intraocular anesthesia: Use preservative-free, 2% intraocular lidocaine.
• Local anesthesia: Use 2% lidocaine with adrenaline (1:200,000) and 7.5 U/mL hyaluronidase. It may be used as a peribulbar anesthesia or for facial nerve block and retrobulbar block. The local anesthesia is given 10 minutes before surgery. Apply orbital compression to make the eye soft and to reduce orbital pressure.
• General anesthesia: A phakic lens implantation surgery only takes a few minutes. General anesthesia makes the surgery more comfortable for the surgeon, who can concentrate better on the steps of the surgery.

Preparation of the surgical field

• 5% povidone: Paint the periorbital skin with povidone 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 and the superior rectus suture are applied in place of the speculum. Adhesive plastic drape, applied to the surface of the eyelids, is used to pull the eyelashes away from the surgical field.

Intraoperative Details

Angle-supported lens

• A 6.00-mm corneoscleral incision is made in the steepest meridian, attempting to correct the preoperative astigmatism. A smaller incision is needed for a foldable lens.
• A 1-mm tunnel incision is placed at the limbus or in the clear cornea, depending on the preoperative astigmatism.
• The anterior chamber is irrigated with acetylcholine and then filled with a viscoelastic material.
• A 5.00-mm silicone Sheets glide is introduced into the anterior chamber, and more viscoelastic material is injected over the glide.
• The phakic IOL is held at the optic with a Kelman-McPherson forceps, and the inferior haptic is slipped into the anterior chamber.
• With the forceps pushing the superior edge of the optical zone, the IOL is carefully slid over the silicone Sheets glide until both ends of the inferior haptics are in contact with the angle. Then, the glide is removed from the anterior chamber.
• The upper haptic is pushed gently into the anterior chamber and under the posterior lip of the wound using a double-tip nucleus manipulator.
• The phakic IOL is rotated, using a Sinskey or Lester hook, to the horizontal meridian where the white-to-white distance is measured. During this maneuver, special care is taken to prevent damage to the angle structures. If a temporal or nasal incision is performed, this rotating maneuver is not required.
• A peripheral iridectomy, 0.5-1 mm in length, is performed.
• If the pupil is not round, the Sinskey hook is used to push the haptic away from the angle; then, it is released.
• Verifying that the lens is well centered, the pupil is completely round, and no traction forces from the haptic footplate are present on the iris is important.
• A 2- to 3-bite running 10-0 nylon suture is used to close the incision, but before the knot is tied, all the viscoelastic material is removed carefully with balanced salt solution. Finally, the suture is tied.
• If a limbal incision is used, a nylon suture is used to close the conjunctival flap.
• After the incision is closed, gonioscopic evaluation is performed to visualize the haptic ends and to verify that they are in a good position and that there is no iris tuck.

Iris claw lens

• Two pocket-type side incisions, one 1-mm wide and one main incision 5- to 6-mm wide, at the 12-o'clock position, are made in the form of a pocket. A foldable version of the lens needs a smaller incision.
• The anterior chamber is filled with viscoelastic material.
• The iris claw lens is slipped into the anterior chamber vertically. Once inside the anterior chamber, the lens is rotated horizontally.
• 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 that grasps a fold of iris under the haptic and passes it through the claw, thereby fixing it. Both instruments are withdrawn, and the surgeon changes hands for holding each tool.
• The anterior chamber is again filled with viscoelastic material, and the lens-fixation instruments are reintroduced.
• The second claw-fixation maneuver is performed through the incision on the opposite side.
• A peripheral iridectomy is performed.
• Viscoelastic material is washed out thoroughly.
• The incision line is closed with 1 or 2 very superficial sutures.

Posterior chamber lens

• One 0.6-mm side port is made. It is needed to inject viscoelastic material in the anterior chamber.
• For a precrystalline lens, a 3.2-mm clear corneal incision is made on the steep meridian.
• 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) or by copious irrigation 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.

End of surgery

• Subconjunctivally inject 20 mg of gentamicin and 2 mg of dexamethasone.
• Apply a sterile pad and a protective shield.

Postoperative Details

• Monitor the patient as with any other IOL surgery. In particular, carefully look at the incision line and be watchful of IOP and any inflammation.
• The first dressing is completed 8-12 hours after the surgery.
• Protecting the eye from injury: 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.
• Patients should be careful when bathing, so as not to spill bathing water into the eye.
• Using the eye: No restrictions for such activities as watching television or reading are indicated.

Physical activity

• No restriction on walking is indicated.
• Patients 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 should be avoided throughout life regardless of the lens design.
• Patients can drive a car after 1-2 days.

Follow-up

• 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.
• Longer follow-up care
  • Patients should receive follow-up care after 1 month, 6 months, and once every year.
  • 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.
  • Gonioscopy is mandatory in angle-supported or posterior chamber lenses. Look for peripheral anterior synechia formation, growth of uveal tissues on the footplates of the lenses, and the presence of pigment that is derived from the iris and the ciliary body.
  • Observe for any crowding of the angle that is due to the IOL behind the iris.

Complications

Complications after phakic lens implantation

General

The early problems are related to the design of the lens and the meticulous details of surgery. The late postoperative complications are related to the interaction of the IOL and the intimate ocular tissues during the lifetime of the patient. Lifelong, regular follow-up care is essential in all cases.

Explantation of the lens may ameliorate some of the complications. Later in life, if the patient develops a cataract, it should be possible to do an atraumatic explantation, followed by cataract extraction and implantation of another appropriate IOL. Development of a newer, safer technology to correct myopia may necessitate explantation of the IOL.

Anterior chamber IOLs

The anterior chamber lens has 2 features; it lies completely in front of the pupil, and it is supported by the delicate tissues of the angle of the anterior chamber. The anterior chamber lens can be safe, if the following occur:

• Minimum contact with the drainage angle
• No micromovement or macromovement and erosion in the angle
• No adverse effect on the integrity of the iris
• No endothelial touch

At present, no single anterior chamber lens can guarantee all 4 of these requirements. A lens has to be somewhat oversized to stay in place; otherwise, it will rotate or move anteroposteriorly. If perforce, it is oversized, it is impossible to avoid erosion of the angle tissues, occurring over a period of time. An endothelial touch can occur if the eye is rubbed even moderately, especially if the flexible and the semiflexible haptics become vaulted due to size mismatch.

Operative complications

If the lens is longer, it may be forced into the ciliary body, leading to severe intraoperative hemorrhage. Hemorrhage from iridectomy site may occur.

Postoperative complications

A lens may press upon the ciliary body and cause tenderness, which is accentuated with the slightest touch, especially if the lens has been placed vertically.

The pressure on the ciliary body can cause low-grade UGH syndrome. Cystoid macular edema may occur.

An undersized lens can rotate in the angle or move anterior-posteriorly and, thus, injure the corneal endothelium. Unmanaged, it leads to corneal decompensation. A mismatched oversized lens or undersized lens can decenter, causing many optical problems, such as reduced vision, prism effect, glare, or diplopia.

An oval pupil can occur, regardless of all the precautions that might have been taken at the time of surgery. Round pupils at the time of surgery and the confirmation of the correct placement of the feet by intraoperative gonioscopy may not prevent the occurrence of pupil ovalization later on. An oval pupil as such produces no symptoms. However, if the process of ovalization continues to increase optical problems, low-grade uveitis and decentration can occur. The late ovalization of the original round pupil is caused by callous formation where the feet of the implant impinges on the iris. The callous formation can contract, causing a progressive pupillary distortion.

Iris overgrowth of the loop can occur. Other postoperative complications include erosion of the uveal tissue in the angle, peripheral iris synechia formation and glaucoma, and neovascularization of the angle. Corneal decompensation may be caused by intermittent touch by rubbing the eye or by size mismatch.

Iris claw lens

Operative complications

Operative complications include off center fixation, pull on the iris root causing hyphema, and hyphema during peripheral iridectomy. Clumsy efforts at iris enclavation can cause a crystalline lens injury.

Postoperative complications

Early dislocation is caused by inadequate fixation. Early or late anterior uveitis can occur. Late dislocation is caused by trauma, leading to momentary opening of the claw through which the iris may wriggle out. The iris tissue in the claw may atrophy and cause dislocation.

Corneal decompensation can be produced by forcible rubbing. Corneal decompensation may occur if a dislocated phakic lens is not corrected or explanted well in time. Cystoid macular edema may occur.

Precrystalline phakic posterior chamber implant

Operative complications

Operative complications include trauma to the lens, which may or may not manifest later.

Early postoperative complications

Pupillary block glaucoma may develop due to the blockage of previous laser iridotomies or viscoelastic material residue in the posterior chamber. It shows itself within the first 24-48 hours. 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 also occur. If the condition does not respond to systemic therapy with acetazolamide, hyperosmotic agents, local miotics, and beta-blockers, surgery may be needed to control this serious problem.

Transciliary filtration in such a case should be performed under general anesthesia. A Fugo blade is used for this surgery. With a 600-µm Fugo blade tip, the sclera is ablated 1 mm behind the surgical limbus until the anterior part of the ciliary body becomes visible. The next step uses a 100-µm Fugo blade tip. An ablation path is made through the anterior part of the ciliary body and into the posterior chamber. Drainage of the posterior chamber deepens the anterior chamber and allows the possibility to save the eye as well as to keep the phakic lens in place. This filtration is recommended once medical management is clearly not working. A delay in surgery means damage.

Explantation of the posterior chamber phakic lens may be performed as either a first resort or a last resort, preferably as the latter.

Delayed management or mismanagement can cause variable degrees of visual loss.

Specular endothelial microscopy in these cases may reveal a substantial loss of endothelial cells. The closure of peripheral iridotomies and pupillary block glaucoma can occur after one or more weeks. Such cases may be treated by a repeat laser iridotomy, surgical peripheral iridectomy, transciliary filtration, or lens explantation.

Late complications

An anterior subcapsular cataract may form because of contact with the natural lens. This complication is being observed frequently. Many patients develop cataract within 2 years. However, the offending phakic lens can be explanted, with the cataract being removed at the same time. The long-term incidence of cataract is not yet known. A small IOL has greater chances of having direct contact with the crystalline lens. Uveitis can occur in acute or 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.

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