NEW YORK — The third day of the Fourth Annual Primary Care Optometry News Symposium in November covered vision correction options ranging from contact lenses to phakic IOLs to refractive surgery. This is the third part of a three-part series. This year’s meeting is scheduled for Nov. 18 to 20.
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PCON NY meeting: Editor Michael D. DePaolis, OD, FAAO, moderated nearly 20 editorial board members and contributors as they presented 20 hours of continuing education credits over the course of the 3-day meeting.
Jennifer L. Smythe, OD, MS, FAAO, associate professor at Pacific University College of Optometry, Forest Grove, Ore., and Loretta Szczotka-Flynn, OD, MS, FAAO, associate professor in the Department of Ophthalmology at Case Western Reserve University and director of Contact Lens Services at the University Hospitals of Cleveland, discussed the expanding modalities for silicone hydrogel lenses. While these lenses have traditionally been marketed for extended wear, their high oxygen transmissibility makes them desirable for a wide variety of applications, Dr. Szczotka-Flynn said.
“If oxygen is so great, why shouldn’t we have it for daily wear?” she said. “Why not have it for the patient who wears his or her lenses for 16 to 18 hours a day, and who may sometimes sleep in them, whether they tell you or not?” She recommended refitting low-Dk-wear patients into silicone hydrogel or hyper-Dk gas-permeable lenses to reverse endothelial polymegathism.
Dr. Szczotka-Flynn cited findings claiming that by the time most patients reach the age of 50, they will have had their eyes closed for about 16 years during sleep. “Therefore, for patients in their 4th, 5th and 6th decades of life, you might want to consider silicone hydrogels, because these are patients whose endothelium is already somewhat compromised.”
Dr. Szczotka-Flynn cited a study by Cavanaugh and colleagues in which epithelial cells that had been washed from the corneas of patients who had worn contact lenses overnight were then exposed to Pseudomonas bacteria. “The highest binding of the Pseudomonas was to the epithelial cells that were exposed to the lowest Dk lenses,” she said.
“Just how much Dk is necessary to avoid corneal swelling in overnight wear?” Dr. Szczotka-Flynn asked. Holden and Mertz said about 87 Dk/t; and Papas (1998), Harvitt (1998) and Sweeney (2000), individually, said about 125 Dk/t. In 2003, Brennan and Coles used revised numbers and an oxygen flux model and said it is about 77 Dk/t.
Dr. Szczotka-Flynn reviewed published data that cautions clinicians who prescribe silicone hydrogel for daily wear to watch for superficial punctate keratitis (SPK) associated with PHMB products (Jones, Opt Vis Sci, 2002). She noted that Bausch & Lomb’s ReNu with MoistureLoc, CIBA Vision’s ClearCare and other peroxide-based products, and Alcon’s Opti-Free Express have no PHMB.
Dr. Smythe said silicone hydrogel lenses can be used for therapeutic purposes as well. “Focus Night & Day [CIBA Vision] did receive Food and Drug Administration approval in May 2003 as a therapeutic lens,” she said.
Drs. Szczotka-Flynn and Smythe also discussed applications for specialty contact lenses. Dr. Smythe shared a case of a healthy, young, 3-D myope with 13-mm corneas. Several soft contact lenses were attempted, all with poor comfort and decentering inferiorly with superior limbal exposure. The patient’s K readings were about 42, but the sagittal height was excessive due to the large cornea. She noted that, according to Caroline and Andre, 50% of the population has a 11.8±0.2-mm corneal diameter, but 50% of the population has a smaller- or larger-than-normal cornea.
She recommended CooperVision’s Hydrasoft or an Innovations In Sight lens for a large-diameter, step lens. CooperVision’s ToriTrack software calculates the “effective K” by considering the flat K and overall corneal diameter, she added.
In another case report, Dr. Smythe discussed a post-LASIK patient who was interested in CRT (corneal refractive therapy, Paragon). She advised designing the lenses based on preoperative Ks and prescription, steepening the landing zone angle by 2° to compensate for the fact that this patient has had LASIK. “Every-other-night wear may be all that’s necessary,” she said.
Dr. Smythe also shared clinical pearls for prescribing specialty design contact lenses. When fitting GP lenses, “remember that the contact lens is always tightest where the cornea is the flattest,” she said.
The normal, unoperated cornea flattens about 0.5 D from the center to the mid-periphery. The post-RK cornea flattens about another 0.5 D from the center to the mid-periphery. If the pre-RK data are not available, look at the postoperative topography map and take a data point 4 mm temporally to fixation. “Ignore the nasal corneal data,” she added, “because they are artifactually flatter due to angle-lambda effects.”
As with RK, start 4 mm temporally to fixation in post-LASIK patients. “If the patient is overcorrected (hyperopic), and we employ our 4 mm rule, we can often end up too steep,” she said. “The solution is to go with a reverse-geometry lens.”
In the case of a decentered ablation, avoid spherical base curve GPs, Dr. Smythe continued. The Innovations In Sight Jupiter lens, which is a semislceral lens, can be fit about 1 D steeper than the steepest point of the cornea, she said, and can be designed in a reverse-geometry format.
Dr. Szczotka-Flynn said that post-PK patients can be fitted as soon as the cornea is relatively stable, sometimes as soon as 3 months postop. According to Waring and colleagues, post-PK corneal topographies indicate a prolate shape in 31%, oblate in 31% and mixed prolate-oblate in 18%, and about 20% of patients have an asymmetric or steep-to-flat graft tilt.
With prolate corneas, use standard aspheric designs, she said. With oblate corneas, use reverse-geometry lenses. “Asymmetric and steep-to-flat corneas constitute a graft tilt category,” Dr. Szczotka-Flynn said. “Try for lid-attachment if the tilt is superior; go with an intralimbal design if the tilt is inferior.”
She added that intralimbal designs are becoming popular. These include the Lens Dynamics Dyna Intra-Limbal design and the GBL design (11.2/8.8) from Con-Cise Labs. The QLT SynergEyes is a hybrid lens undergoing trials for ametropia, keratoconus and postsurgical uses, and it may eventually be available in multifocal and wavefront-designed options.
Dr. Szczotka-Flynn said that a good place to start in forme fruste keratoconus patients is standard toric soft lenses, but the prescription may differ significantly from their spectacle prescription. She recommended considering carrier lenses of silicone hydrogel or daily disposables when using a piggyback modality.
She cautioned that fitting a GP lens too flat on a keratoconic eye can induce scarring and does not retard the progression of the condition. “Look at the tangential maps to get a better sense of the cone morphology,” she said, “but use the sagittal maps for actual base curve determination.”
Eric D. Donnenfeld, MD, a member of the National Medical Advisory Board for TLC Laser Centers, and Marc R. Bloomenstein, OD, FAAO, refractive clinic medical director at Barnet Dulaney Perkins Eye Center of Phoenix, joined Paul M. Karpecki, OD, FAAO, director of research at Moyes Eye Center, Kansas City, to discuss the role of phakic IOLs in today’s refractive practice and how they may be a good solution for patients who are not suitable LASIK patients.
According to Dr. Karpecki, patient expectations, pupil size, keratometry readings and pachymetry results are crucial in the LASIK patient. Controversy still exists regarding whether or not pupil size is significantly correlated with postoperative symptoms, he said.
In LASIK, you must avoid postoperative K readings that are too flat (<35.5) or too steep (>49.5), he said, and be sure to leave at least 250 µm (preferably 275 µm), according to Dr. Donnenfeld, or 300 µm, according to Dr. Bloomenstein, in the corneal bed. A Donnenfeld study found wide variability among microkeratomes; one labeled as creating 130-µm flaps actually created flaps that were 180±90 µm, he said.
Preoperatively, LASIK patients must have a corneal thickness of at least 410 µm, Dr. Karpecki continued. With standard LASIK, a 5-mm optical zone removes 8 µm/D; a 6-mm OZ removes 12 µm/D and a 7-mm OZ removes 15 µm/D. Phakic IOLs are indicated for patients who do not meet these indications, he concluded.
Dr. Donnenfeld believes phakic IOLs will challenge LASIK over the next 5 or 6 years, and he outlined a number of reasons why.
“Patient satisfaction is very high,” he said. “One study showed that 90% of Verisyse (AMO) patients (n=410) reported they were very pleased with their postoperative vision.” Only three of 1,179 eyes developed cataract, he said.
The measured visual acuity is excellent, he said. “Forty-nine percent of Verisyse patients gained best corrected visual acuity, while only 6% lost one or two lines of BCVA,” he said.
Dr. Donnenfeld said that PMMA optics are better than corneal ablative optics, and contrast sensitivity remains the same or improves with phakic IOLs.
Much like 1 day after cataract surgery, phakic IOLs deliver an extraordinary “wow” factor. Combining phakic IOLs and LASIK — called bioptics — can achieve extraordinary visual results. “The future of refractive surgery is intraocular,” Dr. Donnenfeld said. “Phakic IOLs will eventually be available in multifocal platforms.
“IOLs still have faults,” he concluded. “They can’t correct astigmatism and they can’t correct higher-order aberrations. So when I see a patient for phakic IOLs, I tell them there is still a chance that I will bring them back for laser surgery.”
Dr. Bloomenstein discussed the Staar ICL, which is a collamer plate lens that is implanted through a 2.5-mm incision and sits in the posterior sulcus. “The most critical variable is assessing the ‘vault’ between the ICL and the anterior lens capsule,” he said.
In a clinical trial for the Staar toric ICL, patients have an average 20/20+ uncorrected visual acuity postoperatively, he added.
Drs. Donnenfeld, Karpecki and Bloomenstein also shared clinical applications for today’s wavefront technologies.
According to Dr. Bloomenstein, Visx is moving away from using Zernike polynomial technology in its custom ablations and toward a new classification system called Fourier.
Dr. Donnenfeld said, “The next generation of lasers will allow us to actually create certain higher-order aberrations, such as vertical coma, for a presbyopic effect.
The primary third-order, higher-order aberration concern is coma, said Dr. Karpecki, and the most important fourth-order, higher-order aberration is spherical aberration. Secondary astigmatism (fourth-order HOA) is quite debilitating, Dr. Karpecki said. Dr. Bloomenstein added that it creates a monocular polyopia.
“As we age, lenticular-induced spherical aberration increases,” Dr. Donnenfeld added. “The Tecnis (AMO) and SofPort (Bausch & Lomb) IOLs neutralize spherical aberration.”
“Larger treatment zones, blended zones and aberration-correcting software have virtually eliminated ‘glare and flare’ type symptoms,” Dr. Bloomenstein said.
All the laser platforms, said Dr. Karpecki, from Visx, Bausch & Lomb and Alcon, show increased postoperative quality of vision in association with custom ablation. He cautioned that accommodation, dry eye, lens change, age, cortical interpretation and pupil size can all affect the performance of the aberrometer.
Dr. Donnenfeld said that 80% of his patients undergo wavefront-guided custom ablation.
Dr. Karpecki made note of the Ophthonix aberrometer, which can be used to make wavefront-designed spectacles and contact lenses. “According to Binder and colleagues, patients (n=30) were randomized to receive Z-lenses vs. standard spectacle lenses, and the wavefront patients had better quality visual acuity.”
Refractive surgery clinical pearls
The trio also presented a “Refractive Surgery Grand Rounds” session.
According to Dr. Donnenfeld, striae seen 1-day post-LASIK can be pushed into the periphery using a Q-tip. “Then you massage it out with a small stroking technique,” he said.
Another option would be to refer the patient back to the surgeon, Dr. Donnenfeld said. He added that striae at day 1 postop should not be ignored. “Even if it doesn’t seem significant, optically, they are all significant,” he said.
Dr. Bloomenstein said that negative fluorescein staining can reveal overlying striae. Dr. Donnenfeld added that hyperopic cylinder 1-day postoperative with autorefraction usually implicates striae.
In the past, a superiorly decentered ablation induced vertical coma. Today, a wavefront-guided ablation can correct these problems and provide exceptional vision, Dr. Donnenfeld said.
Dr. Bloomenstein shared a case report of a patient who underwent IntraLASIK with the Visx CustomVue, yielding 1-day postoperative visual acuity of 20/15 in both eyes. After 1 month, the patient complained of burning and light sensitivity, although there was good visual acuity. He referred to the condition as GAPP: good acuity and poor photosensitivity. This condition has also been referred to as DAP: delayed acute photophobia, he said.
GAPP is an anecdotal effect from IntraLase use only, he said, usually occurring 3 to 6 weeks postop, with no visual sequelae. The condition is most often self-limiting and usually resolves in 4 to 6 months. He recommended therapy with Lotemax, Systane, Restasis and even tetracycline (100 mg once a day), he said.
Dr. Karpecki shared a case report of a 1-day postop LASIK patient experiencing irritation secondary to epithelial sloughing. Patients at risk for epithelial sloughing, he said, are better candidates for PRK. Those at risk include patients who have map, dot or fingerprint dystrophy or EBMD, need excessive anesthetic, have experienced previous trauma or recurrent erosion. These patients who undergo LASIK are also at much greater risk for DLK.
Dr. Donnenfeld advised that if the EBMD is central, perform epithelial debridement/PTK first, then have the patient return for PRK or LASIK.
For more coverage of the Primary Care Optometry News Symposium, see our February and March issues.