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CATAraCT & REFraCTIvE
EUROTIMES | Volume 17 | Issue 9
With the baby boom generation approaching retirement, presbyopia correction may be the fastest
growing refractive surgery market. Many workable approaches are now available. Which one is best depends on the specific needs and characteristics of individual patients, according to presenters at the annual meeting of the American Academy of Ophthalmology.
Diffractive inlay in a study of 32 eyes in its fourth year of follow-up, the AcuFocus Kamra ACi 7000 diffractive corneal inlay has proven an effective and safe presbyopia treatment, providing J1 or better near visual acuity in half of patients and J3 or better in nearly all patients with minimal loss of distance acuity, said Günther Grabner MD of the Paracelsus Medical University of salzburg, Austria.
The inlay is a 5.0 micron thick circle of polyvinylidene fluoride 3.8mm in diameter with a 1.6mm central aperture. it is implanted under a flap or in a tunnel in the cornea centred over the visual axis of the non-dominant eye to create a pinhole effect that increases depth of focus. in Dr Grabner’s study, 30 eyes improved near visual acuity by up to 6 log-scaled lines. At 48 months, the average gain from J7/8 before surgery was 4.6 lines, with intermediate vision improving from a mean of 20/40 to 20/25.
The Kamra inlay also improves on the performance of monovision, said Vance Thompson MD of sioux Falls south Dakota, Us. Monovision LAsiK with plano in the dominant eye and -1.25 in the other eye show significantly reduced distance visual acuity and contrast sensitivity, as well as reduced stereoacuity, with the impact rising with the add power in the non-dominant eye (Durrie. Trans Am Ophthalmol Soc 2006;
104: 366-401). By contrast, a Us prospective study involving 60 patients found a slight improvement in stereopsis six months after surgery, he reported.
Refractive inlay Refractive inlays also show great promise for exceeding the performance of monovision. Tests of the Flexivue Microlens 3.2mm yield near vision near 20/20 while maintaining contrast sensitivity, distance acuity and stereopsis. The lens has a central zone without power and a peripheral add from 1.5 to 3.5 D. With a small pupil, the near add covers the optical zone for close work, but allows good vision with a wider pupil.
The ReVision Optics Presbylens is a 2.0mm hydrogel inlay that changes the contour of the central cornea, creating an add without side effects such as glare and haloes. it is entering Phase iii clinical trials in the Us. inlays of all types are also longer lasting than presbyopic LAsiK and are removable, Dr Thompson noted.
Presbyopic LASIK Despite some issues with glare and haloes, presbyopic LAsiK remains an attractive alternative for younger presbyopes, those under age 56, said Gustavo E Tamayo MD, Bogota, Colombia. in a retrospective study of 121 eyes in 66 patients undergoing presbyopic LAsiK, he found that 100 per cent of myopes and emmetropes, and 78 per cent of hyperopes achieved 20/25 or better uncorrected near visual acuity, and 100 per cent of all patients achieved 20/25 or better best corrected binocular vision after presbyopic LAsiK treatment.
The procedure works much like multifocal intraocular lenses, Dr Tamayo said. A “knee” contour is ablated in the cornea, creating a central zone of negative spherical aberration and a peripheral zone of positive spherical aberration, increasing depth of focus. The procedure works well, with 92.6 per cent of patients reporting they do not use glasses at any time. The basic procedure is well known and reversible with a CustomVue treatment, he noted.
Multifocal IOLs While multifocal iOLs are not as popular as corneal approaches for patients with clear lenses, they remain a top choice for presbyopia correction for cataract patients. however, they inherently suffer from loss of contrast sensitivity associated with up to 20 per cent light loss, due to splitting of incoming light, and in many cases lack intermediate correction, said Matteo Piovella MD of Monza, Milan, italy.
Dr Piovella noted that pupil size-dependent refractive lenses allow some light
in the intermediate range, but shift the light split from near to far, potentially leaving not enough light at near with a 5.0mm pupil. Apodised diffractive lenses may also be far-dominant, shifting from 40 per cent near at a 2.0mm pupil to 10 per cent at 5.0mm. Theoretically, non-pupil-dependent diffractive designs preserve near vision at larger pupil size, but this may produce haloes, and they still lose 20 per cent of light at all distances.
Nonetheless, about 90 per cent of patients achieve 20/25 or better distance with 20/32 or better near vision with these lenses. An advanced multifocal design from OptiVis minimises light loss and improves intermediate vision with a mix of diffractive, refractive and aspheric zones, he noted. Also new Zeiss AT LisA trifocal improves better light distribution to achieve an increase of depth of focus.
Accommodating IOLs several lenses have been designed to provide accommodation by moving in the capsular bag. According to a study by George Beiko MD of the University of Toronto, Canada, presented by David R hardten MD of Minneapolis, Us, comparing the single optic Crystalens hD implanted bilaterally in 10 patients with the dual optic synchrony lens in 11 patients, the dual optic design is superior. The synchrony group achieved mean 20/20 vision at near, intermediate and far while the Crystalens was 20/20 at distance, 20/25 intermediate and 20/40 near. While the single optic results are better than bilateral plano monofocal lenses, they are about the same as mini monovision with monofocals and the Tetraflex single optic accommodating lens.
Objective data as measured by wavefront, does not support mean accommodation in any single optic accommodating iOL group, Dr Beiko reported. however, the dual optic design provides better near visual acuity and does show evidence of movement in the bag.
Günther Grabner – [email protected] Thompson – [email protected] Tamayo – [email protected] Piovella – [email protected] Hardten – [email protected] Beiko – [email protected]
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PRESBYOPIACorneal inlays, laser surgery and IOLs all show promiseby Howard Larkin in Orlando
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2012-03_EUROTIMES_120x120.indd 4 07.05.2012 18:13:36
Many workable approaches are now available. Which one is best depends on the specific needs and characteristics of individual patients
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