UDAY DEVGAN, MD
Toric IOLs, particularly those with higher dioptric amounts of toric correction, are excellent choices for patients with regular, symmetric, and stable corneal astigmatism. In cases of significant corneal asymmetry, irregularity, or instability, however, toric IOLs may not be the best choice.
For optimal performance, the toric IOL must be aligned at the correct steep corneal meridian as well as aligned in the central visual axis. This means that the center of the toric IOL should be aligned with the center of the “bowtie” of the corneal topography. With the asymmetry and floppy bowtie seen on this patient’s topography, the manufactured perfect symmetry of the toric IOL will unevenly address his irregular corneal astigmatism. This situation may result in higher-order aberrations, which may present as double vision, ghosting, or a sense of visual discomfort. In eyes with abnormal corneas, even with scleral tunnel incisions, there can be induced corneal changes, which may take weeks to months to stabilize.
In this case, the primary problem is the FFKC, and the secondary problem is the cataract. Given his preoperative measurements, I would have advised the patient that cataract surgery would likely correct only part of his vision and that treatment of the FFKC would be required to maximize his sight. At this point, I would perform an IOL exchange in one eye, during which I would replace the toric IOL with a spherical IOL without toricity. I would fit the patient for a rigid gas permeable (RGP) contact lens in the postoperative period. If this modality proved successful, I would repeat the procedure for his other eye.
MICHAEL EHRENHAUS, MD
Toric IOLs have shown great promise for the treatment of regular astigmatism, both in routine cataract cases and in more complex situations, such as after corneal transplants. Surgeons, however, must remember to use the technology carefully, because it may not be warranted for all types of astigmatism.
Based on this patient’s topography and Orbscan results (Bausch + Lomb, Rochester, NY), it appears that he actually has keratoconus in his right eye and most likely in his left eye as well. The phakic IOLs the Visian TICL (not available in the United States; STAAR Surgical Company, Monrovia, CA) and the Toric Artisan lens (not available in the United States; Ophtec BV, Groningen, The Netherlands) have been reported to work very well in patients like this one to reduce both their refractive cylinder and sphere.1,2 The AcrySof Toric lens is recommended for patients with regular “bowtie” astigmatism but may not work well for individuals with irregular astigmatism, corneal scars, or keratoconus due to the need for the lenses to be aligned precisely along the cylindrical axis, which is not shared equally across the cornea in these patients.3,4
The current options for management depend on whether the source of the patient’s complaint is the cornea or the lens. If overrefracting with an RGP contact lens does not eliminate the subjective complaint, then one can attribute the diplopia in that eye to the aberrant visual system created by the irregular cornea plus the toric IOL. In that case, exchanging the lens for a monofocal IOL (after ensuring that the lens is in the correct orientation and that the macula is without pathology) would be the correct next intervention. If the diplopia remained after the overrefraction, then corneal intervention would be the next prudent step. If the patient were contact lens intolerant, placing Intacs (Addition Technology, Inc., Des Plaines, IL) with the aid of a femtosecond laser could improve both the contact lens’ tolerability and the irregular astigmatism.
WARREN E. HILL, MD
Toric IOLs are generally indicated for the treatment of regular corneal astigmatism. Patients with the irregular astigmatism of keratoconus generally have a steep zone on one side of the visual axis rather than a well-defined, symmetrical pattern that straddles it. Even if a toric IOL were aligned with the center of this steep zone on one side of the visual axis, it would unnecessarily add astigmatic correction to the other side. This situation typically results in an astigmatic undercorrection at an unpredictable axis, with the potential addition of higher-order aberrations such as coma. The generation of higher-order aberrations could well be the cause of this patient’s monocular diplopia.
For the keratoconus patient who is accustomed to using RGP contact lenses, there is another unanticipated problem. If the surgeon places a spherical IOL at the time of the cataract procedure, an RGP contact lens could then be used to neutralize the irregular corneal astigmatism of keratoconus. After the placement of a toric IOL, however, addressing the inevitable residual refractive astigmatism with a contact lens involves neutralizing both the corneal astigmatism and the pseudophakic lenticular astigmatism, which will be unmasked. What would normally have been a straightforward contact lens exercise in the presence of a spherical IOL now becomes extremely difficult; the iatrogenic astigmatism of a toric IOL must also be addressed on the front surface of a contact lens for keratoconus.
I would not select a toric IOL for a patient with keratoconus or another form of highly irregular astigmatism. I would suggest exchanging the toric IOL in this case for a standard spherical IOL, because the steep keratometry will probably create a low, or even negative, anterior corneal Z(4,0) value. If the patient could not tolerate the irregular astigmatism with glasses, then an RGP contact lens for keratoconus could be considered.
Section editor Stephen Coleman, MD, is the director of Coleman Vision in Albuquerque, New Mexico. Parag A. Majmudar, MD, is an associate professor, Cornea Service, Rush University Medical Center, Chicago Cornea Consultants, Ltd. Karl G. Stonecipher, MD, is the director of refractive surgery at TLC in Greensboro, North Carolina. Dr. Majmudar may be reached at (847) 882-5900; firstname.lastname@example.org.
Uday Devgan, MD, is in private practice at Devgan Cataract, Lens, & LASIK Center in Los Angeles. Dr. Devgan is chief of ophthalmology at Olive View UCLA Medical Center and is an associate clinical professor at the UCLA Jules Stein Eye Institute. Dr. Devgan may be reached at (800) 337-1969; email@example.com.
Michael Ehrenhaus, MD, is in private practice at New York Cornea Consultants in Bayside, New York, and is the director of cornea and refractive surgery at SUNY Downstate Medical Center in Brooklyn, New York. He acknowledged no financial interest in the products or companies he mentioned. Dr. Ehrenhaus may be reached at (718) 425-0903; firstname.lastname@example.org.
Warren E. Hill, MD, is in private practice at East Valley Ophthalmology in Mesa, Arizona. Dr. Hill may be reached at (480) 981-6130; email@example.com.
- Kamiya K,Shimizu K,Ando W,et al.Phakic Toric Implantable Collamer Lens implantation for the correction of high myopic astigmatism in eyes with keratoconus.J Refract Surg.2008;24(8):840-842.
- Venter J.Artisan phakic intraocular lens in patients with keratoconus.J Refract Surg.2009;25(9):759-764.
- Ruíz-Mesa R,Carrasco-Sánchez D,Díaz-Alvarez SB,et al.Refractive lens exchange with foldable toric intraocular lens.Am J Ophthalmol.2009;147(6):990-996.
- Medicute J,Irigoyen C,Aramberri J,et al.Foldable toric intraocular lens for astigmatism correction in cataract patients.J Cataract Refract Surg.2008;34(4):601-607.