Refractive Surgery for Hyperopia

From EyeWiki
Original article contributed by: Thomas M. Harvey, M.D.
All contributors: Brad H. Feldman, M.D. and Thomas M. Harvey, M.D.
Assigned editor:
Review: Assigned status Update Pending by Natalie Afshari, MD FACS on January 19, 2015.



Background

Hyperopia is the optical term for farsightedness, a condition in which parallel light rays focus behind the retina, making near objects blurry. In severe hyperopia, even distant objects appear blurry. Several vision correction surgeries are available to minimize dependence on glasses and contact lenses in this setting.

Concept

In farsighted eyes, the focusing mechanisms are too weak for the given eye length. Therefore, clear resolution of an image is frequently not possible. Refractive surgery options for hyperopia are designed to increase focusing power (either by changing the cornea's shape or by placing an artificial lens inside the eye). Excimer laser techniques such as Photorefractive Keratectomy (PRK) or Laser in situ keratomilieusis (LASIK) as well as intraocular techniques (phakic intraocular lens or refractive lens exchange) are discussed below. Other techniques such as conductive keratoplasty and laser thermal keratoplasty have had limited acceptance and are not included in this wiki.

History

Farsighted individuals often experience progressive difficulty with uncorrected vision as they age.

Clinical diagnosis

The detection of hyperopia is not difficult with a complete eye exam. In younger patients, cycloplegic (anticholinergic) eye drops often help determine the extent of hyperopia.

Diagnostic procedures

Determination of pupil size, corneal thickness/shape/power as well as endothelial cell counts help determine candidacy. For intraocular procedures, it is beneficial to perform axial lenth measurements. Manifest and cycloplegic refraction are recommended to select the appropriate treatment. The shape of light reflected off the retina can be used to describe elements of aberration or blur and is the basis for custom excimer surgery.

Surgery

Excimer laser (193 nm) surgery is the most common means to surgically correct hyperopia. It modifies the corneal shape.

PRK

After a thorough exam and explanation of the possible risks, the eye is postitioned under the laser. The eye is held open with a sterile speculum. Many patients elect to have an oral sedative to make the entire process less stressful. Numbing eye drops are applied. The area of excimer ablation is exposed by epithelial removal. Epithelial removal may be performed by the laser, a mechanical device, or manual means. The surface of the cornea is dried with a microsurgical sponge. The patient is asked to look at the target light on the laser. Laser pulses are applied in the midperiphery of the cornea to produce steeping in the center. Total treatment times are typically less than 30 seconds. Routinely, a temporary contact lens is used to minimize discomfort after PRK, and it is left in place for overnight wear for less than one week. Prior to eyelid speculum removal, eye drops are sometimes given.

LASIK

After a thorough exam and explanation of the possible risks, the eye is postitioned under the laser. The eye is held open with a sterile speculum. Many patients elect to have an oral sedative to make the entire process less stressful. Numbing drops are applied. The area of excimer ablation is exposed by flap creation using either a mechanical device or an infrared laser. The patient is asked to look at the target light on the laser. Laser pulses are applied in the midperiphery of the cornea to produce steeping in the center. Total treatment times are typically less than 30 seconds. Balanced salt solution irrigates debris and allows repositioning of the corneal flap. The flap is smoothed, the edges dried, and it is verified to be stable.

Surgical placement of an implant can correct hyperopia. It is important to note that there is currently no FDA-approved phakic intraocular lens available to treat hyperopia in the United States.

Phakic Intraocular Lens

Phakic Intraocular Lens surgery involves placement of an artificial lens inside the eye without disturbing the eye's natural lens. After a thorough exam and explanation of the possible risks, the eye is numbed with eye drops or local anesthetic. Microscopic holes are created in the peripheral iris either with a laser or with scissors to encourage normal eye pressure after phakic intraocular lens placement. An eyelid speculum holds the eye open. Small incisions are created near the periphery of the cornea. A space filling jelly-like medication, known as an ophthalmic viscosurgical device, is placed in front of the iris to deepen the structures and create room for lens insertion. Lens insertion follows with an injection apparatus or forceps. The phakic intraocular lens is then either affixed in front of the iris (e.g. Verisyse) or placed behind it (e.g. Visian ICL), depending on the model used. The ophthalmic viscosurgical device is removed and replaces with balanced salt solution. The procedure is performed one eye at a time and may be done sequentially on the same day. Sutures are used to close the Verisyse incision but are not routinely required for the Visian ICL procedure. There is routinely minimal discomfort. Eye drops are prescribed and typically used for about one month after surgery.

Refractive Lens Exchange

Refractive Lens Exchange surgery is simply cataract surgery with intraocular lens placement prior to the formation of a cataract. This option corrects the refractive error as well as eliminates the formation of cataract in the future. After a thorough exam and explanation of the possible risks, the eye is numbed with eye drops or local anesthetic. An eyelid speculum holds the eye open. Small incisions are created near the periphery of the cornea. A space filling jelly-like medication, known as an ophthalmic viscosurgical device, is placed in front of the iris to deepen the structures and to allow controlled access to the eye's natural lens. An opening in the natural lens is created, and the internal material is mobilized with balanced salt solution. A vacuum probe removes the internal material, thereby creating space for an intraocular lens. The intraocular lens is flexible enough to be injected through a small incision and self-fixate inside the remaining capsule of the natural lens. Sutures are not routinely required, and discomfort is usually minimal. Eye drops are prescribed and typically used for about one month after surgery.

Surgical follow up

Hyperopic refractive surgery does require follow up with a qualified doctor. One possible follow up schedule could be: the day after surgery, one week after surgery, and one month after surgery. Annual checks are advisable after most intraocular surgery.

Complications

Excimer surgery risks include: glare, halo, dry eye, decreased best corrected vision, infection, and inflammation/scar.

Intraocular Surgery risks include: pupillary block and cataract (specifically for phakic intraocular lenses), endothelial cell loss, glare, halo, decreased best corrected vision, infection, and inflammation.

Prognosis

Outcomes for techniques described in this wiki have been generally quite good. While no evidence based data exist on this topic, it seems that most patients' vision is greatly improved.

Additional Resources

References

  1. Koivula A, Zetterström C. Phakic intraocular lens for the correction of hyperopia. J Cataract Refract Surg. 2009;35(2):248-55.
  2. Pesando PM, Ghiringhello MP, Di Meglio G, Fanton G. Posterior chamber phakic intraocular lens (ICL) for hyperopia: ten-year follow-up. J Cataract Refract Surg. 2007;33(9):1579-84.
  3. Koch DD, Harvey TM. Vision Correction Procedures.Conn's Current Therapy. 2006;227-30.