The lens within the capsular bag appears to be well centered, whereas the one in the ciliary sulcus is obviously decentered and has an unusual, crescent-shaped peripheral defect. In increasing order of importance, the three issues are residual myopia, a dislocated and damaged piggyback lens, and the inherent refractive problems following RK.
If the patient desires a refractive result closer to plano, the ciliary sulcus lens would need to have 2.00D less power. One can carry out this calculation using either the published refractive vergence formula or the Holladay R formula contained within the Holladay IOL Consultant (Holladay Consulting, Inc., Bellaire, TX).1 The clinician would use either (1) the average of the 0- and 1-mm annular rings from the numerical view of the Humphrey Atlas corneal topography system (Carl Zeiss Meditec Inc., Dublin, CA) or (2) the adjusted effective refractive power of the Holladay Diagnostic Summary of the Eyesys 2000 Corneal Analysis System (Eyesys Vision, Houston, TX).
With the optic damaged in such a unique way, it is possible that one or both of the haptics may also have been damaged during placement. Alternatively, one of the haptics may have passed through a zonular defect. All in all, I feel that it would be best to exchange the +6.00D piggyback lens.
To remove the damaged lens in the ciliary sulcus, I would create a 3.5-mm scleral incision. Under the protection of abundant viscoelastic, I would rotate the damaged IOL into a central position and, with haptic-cutting scissors, make two cuts in the lens optic for the length of its radius and 90º apart. This right-angle defect would allow the lens to be “walked” out of an incision only half the size of the optic, much in the same way that a large chair is walked around and out a door with an opening smaller than its length.
As a replacement lens, I would inject a +4.00D Staar AQ5010V IOL (Staar Surgical Company). With its 6.3-mm optic and 14.0-mm haptic, this lens should center nicely. On the off chance that the original sulcus lens was decentered because one of its haptics passed through a zonular defect, I would carefully position the new lens with its haptics oriented along an oblique axis while making sure that the lens was completely stable prior to removing the viscoelastic.
After anterior segment surgery in an eye with prior RK, the patient should understand that transient hyperopia frequently occurs in the immediate postoperative period and typically resolves in 4 to 6 weeks. The physician should also explain that fluctuating vision and glare are both common after RK and that these symptoms may persist in some form despite a successful lens exchange. Finally, the all-too-common presence of higher-order aberrations following RK may limit BCVA, especially in the presence of a large pupil.TERRY KIM, MD, AND
D. MATTHEW BUSHLEY, MD
The management of any patient with a refractive surprise after initial cataract surgery should begin with a review of the data and methods used in the primary IOL calculation. Surgeons should review the keratometry, topography, and ultrasound axial-length measurements and compare them to those of the fellow eye. The ophthalmologist must rule out errors in data transcription, IOL packaging and labeling, and ultrasound axial-length measurement due to posterior staphyloma. The IOLMaster (Carl Zeiss Meditec Inc., Dublin, CA) can prove useful by providing a true measurement of the optical axial length.
IOL calculations in patients with a history of previous keratorefractive surgery are less accurate in general due to limitations in physicians' ability to accurately measure corneal refractive power in these eyes. Currently available technology overestimates the refractive power of corneas after myopic keratorefractive surgery, and the subsequent IOL calculation tends to yield a hyperopic postoperative result. Alternative IOL calculation techniques such as the historical and contact lens methods represent attempts to improve accuracy. Despite these advances, hyperopic surprises in these patients are not uncommon, particularly in the post-RK patient subset. Chen et al2 recently reported their results with IOL calculation in post-RK eyes and found that—despite using the flattest K calculated by either the historical or contact lens overrefraction method and targeting an average of -1.50D of postoperative myopia—hyperopia would still have occurred in almost half of the patients. Management options for residual postoperative refractive errors include glasses, contact lenses, keratorefractive procedures such as LASIK, and intraocular procedures, including IOL exchange and a secondary, sulcus-supported piggyback lens.
Assuming the surgeon deemed the initial IOL calculation to be accurate based on the best available data, one can attribute this patient's hyperopic result partly to the inherent inaccuracies of IOL calculations in post-RK patients. More important, however, is the need to recognize that post-RK patients can experience a significant, temporary hyperopic shift after routine phacoemulsification with IOL placement due to corneal hydration and relative central corneal flattening. Patients with a smaller optical zone and those with eight or more radial incisions are more likely to experience this effect, which may last for months.
The surgeon managed this patient's early postoperative hyperopic result with a secondary, sulcus-supported piggyback lens—a technique that should provide an excellent refractive outcome assuming refractive stability and a well-centered, properly positioned piggyback lens. This patient's piggyback lens was probably inserted prior to documented refractive stability after initial cataract surgery. In addition, the silicone piggyback lens has a noted optic defect, a result of either an optic fracture during insertion through a small incision or a pre-existing manufacturing defect. The regions of the optic-haptic junction, however, appear undamaged. The piggyback IOL subsequently decentered, most likely due to the surgeon's inability to achieve adequate fixation in the ciliary sulcus of this highly myopic eye, or possibly due to deficient capsular or zonular support. It would be interesting to know the early postoperative refractive results from the piggyback lens implantation while the lens was centered. Lacking these data, there is no accurate way to determine the correct secondary piggyback IOL power, due to the decentration of the current piggyback lens and its variable effect on the patient's refraction.
After a lengthy discussion with the patient that emphasized the limitations of IOL-power calculations and the increased probability of a refractive complication, we would perform a complete eye examination, including endothelial cell count and a close inspection of the RK wounds. Next, we would recommend removal of the piggyback IOL through a self-sealing, small, clear corneal incision. We would use topical anesthesia, a dispersive viscosurgical device, and partial or complete optic transection within the anterior chamber. We would not attempt to refold the silicone IOL within the anterior chamber, due to the increased difficulty of this maneuver relative to acrylic IOLs and the higher inherent risk to the corneal endothelium. Instead, we would await refractive and topographic stability, and then we would perform manifest refraction and rigid contact-lens overrefraction. After assessing the patient's satisfaction and the quality of vision achieved, we would consider additional intraocular surgery if he were unsatisfied with spectacle or contact lens correction. If we chose a secondary piggyback IOL, the power calculation would be straightforwardly based on refraction, and IOL power would approximate 1.5 times the MRSE at the spectacle plane. We would select a target postoperative spherical equivalent of -0.50 to -1.00D to allow a cushion for IOL calculation inaccuracies as well as the progressive, slow hyperopic drift in the post-RK patient. The IOL would likely be less than +4.00D. We would place a Staar AQ5010V foldable, three-piece, silicone lens in the ciliary sulcus—a lens with a larger haptic-to-haptic diameter (14mm) compared to the previously inserted model—to improve sulcus fixation. The IOL would be positioned in such a way that its haptics were oriented 90º away from their previous location to avoid any areas of possible capsular or zonular instability. We would not consider suture-fixation of a piggyback lens due to possible lens tilt, the unpredictability of the IOL's final position, and potential anterior displacement of the IOL—all of which could prevent adequate optical coupling of the two IOLs.ROBERT A. KAUFER, MD
Because this patient has already had three surgeries, the problem should be solved with minimal surgical intervention. The implanted lens is damaged as well as misaligned, and its power is incorrect. The lens' misplacement is due to the absence or damage of the zonules at the 9-o´clock position. The problem must be corrected, or the IOL may end up in the vitreous cavity.
I recommend explanting the damaged lens and replacing it with a 5.00D Acrysof MA60MA three-piece IOL (Alcon Laboratories, Inc., Fort Worth, TX). I would place the lens in the sulcus with its haptics in the counterclockwise direction from 11 to 5 o'clock. After centering the lens, I would suture the haptics to the iris in order to ensure it does not become decentered. Alternatives include explanting the misplaced lens and placing an ACIOL or an iris-fixated lens. Despite refinements in design, an ACIOL would require a larger incision and involve a greater potential for corneal decompensation and long-term inflammation than the Acrysof. Suturing an ACIOL to the sclera would require transscleral sutures, associated with potential complications, such as choroidal hemorrhage and late endophthalmitis, in addition to a much more complicated surgical technique.
First, I would fill the anterior chamber with Viscoat (Alcon Laboratories, Inc.) through a peripheral 1-mm paracentesis between two RK incisions and bring the damaged lens into the anterior chamber with a Sinskey hook or Lester manipulator (Katena Products, Inc., Denville, NJ). A sclerocorneal incision of approximately 3mm would not alter the RK incisions but would allow me adequate space to cut this damaged lens into two halves and explant them.
Next, I would implant the Acrysof lens. If there were too much dilation, Miochol-E (Novartis Ophthalmics, Inc., Duluth, GA) could help trap the optic in front of the iris. I could then easily fixate the exposed haptics to the peripheral iris. A 10–0 polypropylene suture with a CIF-4 curved needle would be appropriate for the McCannel suture. As described by Chang,3 tilting the lens forward with a Lester hook (Katena Products, Inc.) creates better visualization as the needle passes through the mid-iris stroma. I would use Siepser slipknots to fix each of the haptics into position. Prolapsing the captured optic posteriorly would complete the maneuver.
I believe that this patient's surgery can be safely performed under topical anesthesia, supplemented with intraocular, nonpreserved 1% lidocaine without epinephrine.FRANCESCO CARONES, MD
The piggyback IOL appears decentered for a reason that is difficult to fully understand from Figure 1. The relatively poor BCVA reported after cataract surgery (20/30) suggests reasons other than hyperopia for the patient's complaints. I suspect the original RK induced higher-order aberrations responsible for both the poor BCVA and visual disturbances. The low keratometry readings and the low effective corneal refractive power for a 3-mm pupil support this hypothesis.
I would therefore try to determine the reason for the piggyback IOL's decentration. A slit-lamp examination using a mirror lens for angle visualization, performed at full pharmacologic mydriasis, may reveal whether the problem is related to a defect in the IOL's haptic or to damage of the capsular bag or zonular fibers. If the examination were not revelatory, I would employ high-frequency ultrasound biometry to evaluate the angle and the sulcus.
If the haptic is damaged but the ocular anatomy is not affected, I would remove the piggyback IOL and place a new piggyback IOL in the sulcus. My target would be a slightly myopic final spherical equivalent refractive outcome (in the range of -1.00 to -1.50D). After confirming refractive stability (usually 4 to 6 weeks later), I would assess the patient's satisfaction. If he still complained of symptoms related to higher-order aberrations, I would consider performing a wavefront-based customized ablation that would leave the eye either slightly myopic or plano per the patient's request.
If ocular anatomy (eg, damaged capsular bag or lysis of zonular fibers) caused the piggyback IOL's decentration, I would remove the IOL but then consider piggybacking a Verisyse aphakic IOL implant (Advanced Medical Optics, Inc., Santa Ana, CA). All other issues would be the same.
Section Editors Robert J. Cionni, MD; Michael Snyder, MD; and Robert H. Osher, MD, are cataract specialists at the Cincinnati Eye Institute in Ohio. They may be reached at (513) 984-5133; firstname.lastname@example.org.
D. Matthew Bushley, MD, is Clinical Associate, Cornea and Refractive Surgery Services, Duke University Eye Center in Durham, North Carolina. He states that he holds no direct financial interest in the products or companies mentioned herein. Dr. Bushley may be reached at (919) 681-3568; email@example.com.
Francesco Carones, MD, is Co-Founder and Medical Director of the Carones Ophthalmology Center in Milan, Italy. He states that he holds no direct financial interest in the products or companies mentioned herein. Dr. Carones may be reached at +39 02 7631 8174; firstname.lastname@example.org.
Warren E. Hill, MD, FACS, is Medical Director of East Valley Ophthalmology in Mesa, Arizona. He has served as a consultant for Alcon Laboratories, Inc., and Carl Zeiss Meditec Inc. but states that he holds no direct financial interest in the products or other companies mentioned herein.Dr. Hill may be reached at (480) 981-6130;
Robert A. Kaufer, MD, is Medical Director of the Kaufer Eye Clinic in Buenos Aires, Argentina. He did not disclose a financial interest in any product or company mentioned herein. Dr. Kaufer may be reached at email@example.com.
Terry Kim, MD, is Associate Professor of Ophthalmology, Cornea and Refractive Surgery Services, at Duke University Eye Center in Durham, North Carolina. He states that he holds no direct financial interest in the products or companies mentioned herein. Dr. Kim may be reached at (919) 681-3568; firstname.lastname@example.org. Holladay JT. Standardizing constants for ultrasonic biometry, keratometry, and intraocular lens power calculations. J Cataract Refract Surg. 1997;23:1356-1370.
2. Chen L, Mannis MJ, Salz JJ, et al. Analysis of intraocular lens power calculation in post-radial keratotomy eyes. J Cataract Refract Surg. 2003;29:65-70.
3. Chang DF. Siepser slipknot for McCannel iris-suture fixation of subluxated intraocular lenses. J Cataract Refract Surg. 2004;30:1170-1176.