Crystalens AO in the Practice
Clinical experience and surgical pearls.
I have been practicing ophthalmology for 14 years, and I started working with the Crystalens Accommodating IOL (Bausch + Lomb, Rochester, NY) in 2000. Therefore, more than two-thirds of my career has been spent watching the development of this lens. Every day, I explain to my presbyopic patients what wonderful visual quality a monofocal accommodating IOL can deliver.
Image quality is incredibly important to IOL recipients. Each patient has his or her own tolerance for visual performance. Unfortunately, we cannot test this tolerance preoperatively, so we implant the IOL we think will suit the individual best. Sometimes, we have to exchange a presbyopia-correcting IOL, more often a multifocal, due to intolerable visual imagery.
What visual problems do recipients of presbyopiacorrecting IOLs complain about most? With multifocal IOLs, a definable percentage of patients will experience significant halos and a loss of contrast sensitivity as noted by symptoms of “waxy vision.” Some patients simply cannot tolerate or adapt to these symptoms. I still use multifocal IOLs, but I discuss their possible visual effects in detail with the candidate. If these issues arise postoperatively, forewarned patients are much easier to work with and will not loose confidence in the physician.
Some comparative data available illustrate the difference in performance between the monofocal, aspheric Crystalens 5–O IOL and the AcrySof IQ ReSTOR IOL +4.0 D. I conducted a large study of mixed IOL technologies. I implanted 172 consecutive patients with a Crystalens 5–0 in one eye and an AcrySof IQ ReSTOR IOL +4.0 D in the other eye. I probably do more mixing than anyone, and I know that there is a distinct difference. At 3 months postoperatively, I found that the eyes implanted with the AcrySof IQ ReSTOR IOL +4.0 D (n = 172) averaged one line worse of best distance-corrected vision than the monofocal optic of the Crystalens 5–0. I think this finding speaks directly to the optical quality of a monofocal versus a multifocal optic.
In a more recent evaluation of the Crystalens AO versus the AcrySof IQ ReSTOR IOL, significantly more of the Crystalens AO eyes achieved 20/20 UCVA at distance (Figure 1) and intermediate (Figure 2) than the AcrySof IQ ReSTOR IOL. The importance of optimal uncorrected vision is a judgement call for the surgeon and patient. At worst, Crystalens recipients can always put on a pair of readers if they are unable to perform a near task. The upside is that they will have excellent visual performance at all focal points. Although the AcrySof ReSTOR lens has a higher rate of J1 acuity at near, it requires a trade-off. Patients who experience unwanted imagery with multifocal IOLs cannot put on a pair of glasses to resolve their issues, and these visual symptoms may never fully resolve. I recently saw a patient in whom I had implanted AcrySof IQ ReSTOR IOLs, and she asked when her vision was going to improve. Since she noted these symptoms immediately after the implantation, I told the patient that they may never resolve. She responded that she did not think she could live with the quality of vision the lens was delivering.
Monofocal IOLs offer superior optical performance, contrast sensitivity, and modular transfer function, because they refract light to a single point (Figure 3). Multifocal lenses that split the light necessitate a trade-off between a greater quantity of vision from near to distance, but the trade-off is reduced visual quality. This is why refractive and diffractive IOLs have greater reported rates of halo and glare and the waxy vision phenomenon.
Currently in the United States, Crystalens implantations are composed of 80% Crystalens AO and 20% Crystalens HD. Although I know some surgeons now use the AO platform for 100% of their implantations, I still use the Crystalens HD lens, particularly when I plan to mix IOLs. I often place the Crystalens AO IOL in the dominant-distance eye and the Crystalens HD in the nondominant eye to give the patient slightly stronger near vision. I have found that this strategy improves patient satisfaction across the entire spectrum of vision.
Each model of the Crystalens requires a slightly different A-constant (see Crystalens AOMeasurements) and therefore requires a different IOL formula. The SRK/T formula works best for eyes with axial lengths measuring 22.01 mm or longer. I now use the Holladay II formula (Holladay Consulting, Inc., Bellaire, TX) for shorter eyes and those with keratometry readings that are flatter than 42.00 D or steeper than 47.00 D (independent of axial length).
There are a few surgical tips I recommend for creating the incision and the capsulorhexis, inserting the lens, and completing the case. I recommend using a scleral tunnel, which I feel is of higher quality than a clear corneal incision. Whatever incision you use must be watertight, and multiplanar incisions are more watertight than a single-plane incisions. A watertight Wong pocket is ideal (Figure 4).
At the conclusion of the case, the goal is to achieve a posterior vault of the Crystalens’ optic to prevent a surprise myopic effect on the first postoperative day. The reports of asymmetric vaulting, or Z syndrome, with the Crystalens did not occur until we began using small capsulorhexis of 4.0 to 4.5 mm. Creating a 5.5- to 6.0-mm capsulorhexis eliminates this problem.
To remove the remaining lens epithelial cells, I recommend polishing the undersurface of the anterior capsule using a Whitman-Shepherd polisher (Baush + Lomb/ Storz Ophthalmics). Personally, I polish the posterior capsule and do not spend much time on the anterior capsule.
Before inserting the Crystalens AO, coat the capsular bag with a cohesive viscoelastic to help prevent the lens’ thin optic from flexing inside the eye. The OVD will also expand the bag to the point that you may easily rotate the lens. For insertion, I use the Crystalsert injector (Bausch + Lomb), which is designed to implant the lens though a 2.8-mm incision. Rotate the IOL 90° after inserting it, and make sure the haptics are in the capsular sulcus. The more bulbous haptic should be on the right. If it is on the left, it means the lens was inserted upside down.
At the close of the case, make sure that all four of the Crystalens' polyimide loops are in the capsular bag. If the lens will not rotate, it is a good indication that two of the loops are not fully in the bag. You should be able to directly visualize the lens completely in the capsular bag. Once the lens is in place, make sure that both the paracentesis and the main incisions are watertight, because this does make a difference in the refractive outcome.
For those surgeons just starting to implant presbyopiacorrecting lenses, I recommend performing cycloplegia. On the first postoperative day, you will be able to see that everything is where it is supposed to be anatomically. However, make sure the patient can function visually for the first 2 weeks after the surgery. This is critical to his or her satisfaction with the procedure. If he or she needs reading glasses to function during that time, by all means, provide them.
Postoperative medication is often taken for granted. I recommend prescribing NSAIDs for every patient who receives presbyopia-correcting lenses for 5 to 6 weeks longer than what you would prescribe for typical cataract patients.
Finally, there are many resources available for surgical pearls. The online ASCRS chat board is easily accessible. Also, the clinical pearls booklet by Bausch + Lomb (available at http://www.bauschsurgical.com) is a review of all of the strategies that have been learned throughout the years with this lens and implantation procedure.
Although multifocal IOLs do work, certain patients will have issues with them and must be educated about the tradeoff. Because some patients will not adapt to that imagery, patient selection is crucial. My experience with the Crystalens is that everyone tolerates this implant. Those who do not achieve the full breadth of visual focal points will need a simple pair of readers for fine near work. Finally, a proper surgical technique will solve most of the potential issues with using this lens technology.
John F. Doane, MD, specializing in corneal and refractive surgery, is in private practice with Discover Vision Centers in Kansas City, Missouri, and he is a clinical assistant professor for the Department of Ophthalmology, Kansas University Medical Center. He is a consultant to Bausch + Lomb and was a clinical investigator for the Crystalens Accommodating IOL. Dr. Doane may be reached at (816) 478-1230; email@example.com.
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