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Quality will always distinguish itself
J CATARACT REFRACT SURG - VOL 33, FEBRUARY 2007
FROM THE EDITOR
Quality will always distinguish itself The heady days of refractive relief by transformation of gross ametropia to emmetropia are past; quality of vision is the new buzz phrase. Kymionis et al. (page 191) confirm, albeit with a small sample, the long-term efficacy of laser in situ keratomileusis (LASIK) to partly answer the doubters who forecast doom and gloom for long-term outcomes. It is satisfying to realize the promise of the early investigators with this most welcome longitudinal study. It follows that of Rajan et al.,1 whose 12-year follow-up of ablation zones in photorefractive keratectomy (PRK) reveals that better refractive predictability resulted from a larger ablation zone. This was reflected in early hyperopic shift, regression, corneal transparency, and night halos. As we have come to expect, no eye had sight-threatening complications such as ectasia or late-onset corneal haze during the extended follow-up. As we learn these lessons, we apply corneal laser technical attributes to intraocular lens (IOL) implantation, the goal being to seek constant improvement in vision quality. The aphorism ‘‘one man’s meat is another man’s poison’’ could be applied to vision and quality; with similar demonstrable aberrant visual elements, it seems possible to make one patient happy and another not so. The way we interpret such disparities is by invoking psycho-optics or neural adaptation (the refractive surgeon’s friend), wherein the individual image processing in our visual cortex may or may not filter out unwanted image degradation. As scientific physicians, all we can do is attempt to level the playing field by reducing or eliminating lower- and higher-order optical aberrations. What is meant by the term quality of vision? This is evaluated by measuring visual acuity; wavefront aberration; contrast; and unwanted visual effects such as glare, low contrast, shadows, and starbursts. We are now able to measure all these parameters to convince ourselves that one technique or one lens is better than another, which almost assumes a universality of the human response in both sexes and at all ages. One aspect of the practicality of vision quality is discussed by Schmitz et al.,2 who compared contrast sensitivity and glare disability by halogen light to simulate the glare seen with oncoming vehicle headlights by patients with multifocal or monofocal IOLs. At the lowest spatial frequency (3 cpd) without halogen glare, contrast sensitivity was lower in the multifocal group than in the monofocal group (P Z.0292). With additional glare, there was no difference between the groups. At all other spatial Q 2007 ASCRS and ESCRS Published by Elsevier Inc.
frequencies, there was no statistically significant betweengroup difference. In both groups, patients 70 years and older had reduced contrast sensitivity without halogen glare and with moderate and strong glare. Astigmatism greater than 1.0 diopter had no significant influence on contrast sensitivity and glare disability when monofocal and multifocal IOLs were compared. Chen et al.3 have looked at whether Tecnis IOLs are able to improve the quality of vision by measuring visual acuity, wavefront aberration, and contrast sensitivity. They report that the Tecnis Z9001 IOL with a modified prolate anterior surface produces negative spherical aberrations, reducing higher-order aberrations in pseudophakic eyes. This leads to enhanced contrast and improves functional vision compared with conventional spherical IOLs. Three articles in this issue investigate aspects of vision quality after refractive lenticular interventions. Bellucci et al. (page 203), like Chen et al.,2 evaluate the optical aberrations in eyes with the aspheric Tecnis Z9000 IOL and compare the results with those in eyes with the parent spherical 911 CeeOn Edge IOL and in phakic age-matched eyes after uneventful cataract surgery and in-the-bag IOL implantation. The aspheric IOL design yielded better results than the parent spherical design for ocular aberrations and vision quality. Although induced coma was somewhat higher, the overall results were not affected. The physiologic IOL decentration following correct in-the-bag implantation did not cancel the advantages of asphericity. The difference between the spherical aberrations in the Tecnis eyes and those in the phakic eyes was not significant (P Z.149), suggesting some negative spherical aberration of the aging transparent lens of their patients. Denoyer et al. (page 210) also consider the quality of vision after cataract surgery with the Tecnis Z9000 IOL and ask whether improvements in contrast sensitivity and wavefront aberration mean better daily vision quality. Their answer is that implantation of the aspheric IOL with negative spherical aberrations results in reduced ocular spherical aberrations and thereby improves mesopic contrast sensitivity, leading to better subjective quality of vision. Finally, Alfonso et al. (page 197) investigate the quality of vision with the Acri.Twin asymmetric diffractive bifocal IOL system and note that asymmetric bilateral implantation of Acri.Twin IOLs resulted in good simultaneous distance and near vision, with improved contrast under photopic and mesopic conditions. The differences between 0886-3350/07/$-see front matter doi:10.1016/j.jcrs.2006.12.001
173
FROM THE EDITOR
monocular and binocular visual acuity and contrast sensitivity were obtained because of the distance/near weighted light distribution of Acri.Twin IOLs. Advances in wavefront technology prompted their application to corneal laser surgery, especially improvement in visual outcomes for night vision. Their application to lens-based refractive surgery has followed. As aberrations are pupil dependent and younger patients generally have larger pupils, it is refractive lens exchange eyes that will achieve the most benefit from aspheric lens designs.
REFERENCES 1. Rajan MS, O’Brart D, Jaycock P, Marshall J. Effects of ablation diameter on long-term refractive stability and corneal transparency after photorefractive keratectomy. Ophthalmology 2006; 113:1798–1806 2. Schmitz S, Dick HB, Krummenauer F, et al. Contrast sensitivity and glare disability by halogen light after monofocal and multifocal lens implantation. Br J Ophthalmol 2000; 84:1109–1112 3. Chen WR, Ye HH, Qian YY, et al. Comparison of higher-order aberrations and contrast sensitivity between Tecnis Z9001 and CeeOn 911A intraocular lenses: a prospective randomized study. Chin Med J (Engl) 2006; 119:1779–1784
Emanuel S. Rosen, FRCSE
174
J CATARACT REFRACT SURG - VOL 33, FEBRUARY 2007
FROM THE EDITOR
Quality will always distinguish itself The heady days of refractive relief by transformation of gross ametropia to emmetropia are past; quality of vision is the new buzz phrase. Kymionis et al. (page 191) confirm, albeit with a small sample, the long-term efficacy of laser in situ keratomileusis (LASIK) to partly answer the doubters who forecast doom and gloom for long-term outcomes. It is satisfying to realize the promise of the early investigators with this most welcome longitudinal study. It follows that of Rajan et al.,1 whose 12-year follow-up of ablation zones in photorefractive keratectomy (PRK) reveals that better refractive predictability resulted from a larger ablation zone. This was reflected in early hyperopic shift, regression, corneal transparency, and night halos. As we have come to expect, no eye had sight-threatening complications such as ectasia or late-onset corneal haze during the extended follow-up. As we learn these lessons, we apply corneal laser technical attributes to intraocular lens (IOL) implantation, the goal being to seek constant improvement in vision quality. The aphorism ‘‘one man’s meat is another man’s poison’’ could be applied to vision and quality; with similar demonstrable aberrant visual elements, it seems possible to make one patient happy and another not so. The way we interpret such disparities is by invoking psycho-optics or neural adaptation (the refractive surgeon’s friend), wherein the individual image processing in our visual cortex may or may not filter out unwanted image degradation. As scientific physicians, all we can do is attempt to level the playing field by reducing or eliminating lower- and higher-order optical aberrations. What is meant by the term quality of vision? This is evaluated by measuring visual acuity; wavefront aberration; contrast; and unwanted visual effects such as glare, low contrast, shadows, and starbursts. We are now able to measure all these parameters to convince ourselves that one technique or one lens is better than another, which almost assumes a universality of the human response in both sexes and at all ages. One aspect of the practicality of vision quality is discussed by Schmitz et al.,2 who compared contrast sensitivity and glare disability by halogen light to simulate the glare seen with oncoming vehicle headlights by patients with multifocal or monofocal IOLs. At the lowest spatial frequency (3 cpd) without halogen glare, contrast sensitivity was lower in the multifocal group than in the monofocal group (P Z.0292). With additional glare, there was no difference between the groups. At all other spatial Q 2007 ASCRS and ESCRS Published by Elsevier Inc.
frequencies, there was no statistically significant betweengroup difference. In both groups, patients 70 years and older had reduced contrast sensitivity without halogen glare and with moderate and strong glare. Astigmatism greater than 1.0 diopter had no significant influence on contrast sensitivity and glare disability when monofocal and multifocal IOLs were compared. Chen et al.3 have looked at whether Tecnis IOLs are able to improve the quality of vision by measuring visual acuity, wavefront aberration, and contrast sensitivity. They report that the Tecnis Z9001 IOL with a modified prolate anterior surface produces negative spherical aberrations, reducing higher-order aberrations in pseudophakic eyes. This leads to enhanced contrast and improves functional vision compared with conventional spherical IOLs. Three articles in this issue investigate aspects of vision quality after refractive lenticular interventions. Bellucci et al. (page 203), like Chen et al.,2 evaluate the optical aberrations in eyes with the aspheric Tecnis Z9000 IOL and compare the results with those in eyes with the parent spherical 911 CeeOn Edge IOL and in phakic age-matched eyes after uneventful cataract surgery and in-the-bag IOL implantation. The aspheric IOL design yielded better results than the parent spherical design for ocular aberrations and vision quality. Although induced coma was somewhat higher, the overall results were not affected. The physiologic IOL decentration following correct in-the-bag implantation did not cancel the advantages of asphericity. The difference between the spherical aberrations in the Tecnis eyes and those in the phakic eyes was not significant (P Z.149), suggesting some negative spherical aberration of the aging transparent lens of their patients. Denoyer et al. (page 210) also consider the quality of vision after cataract surgery with the Tecnis Z9000 IOL and ask whether improvements in contrast sensitivity and wavefront aberration mean better daily vision quality. Their answer is that implantation of the aspheric IOL with negative spherical aberrations results in reduced ocular spherical aberrations and thereby improves mesopic contrast sensitivity, leading to better subjective quality of vision. Finally, Alfonso et al. (page 197) investigate the quality of vision with the Acri.Twin asymmetric diffractive bifocal IOL system and note that asymmetric bilateral implantation of Acri.Twin IOLs resulted in good simultaneous distance and near vision, with improved contrast under photopic and mesopic conditions. The differences between 0886-3350/07/$-see front matter doi:10.1016/j.jcrs.2006.12.001
173
FROM THE EDITOR
monocular and binocular visual acuity and contrast sensitivity were obtained because of the distance/near weighted light distribution of Acri.Twin IOLs. Advances in wavefront technology prompted their application to corneal laser surgery, especially improvement in visual outcomes for night vision. Their application to lens-based refractive surgery has followed. As aberrations are pupil dependent and younger patients generally have larger pupils, it is refractive lens exchange eyes that will achieve the most benefit from aspheric lens designs.
REFERENCES 1. Rajan MS, O’Brart D, Jaycock P, Marshall J. Effects of ablation diameter on long-term refractive stability and corneal transparency after photorefractive keratectomy. Ophthalmology 2006; 113:1798–1806 2. Schmitz S, Dick HB, Krummenauer F, et al. Contrast sensitivity and glare disability by halogen light after monofocal and multifocal lens implantation. Br J Ophthalmol 2000; 84:1109–1112 3. Chen WR, Ye HH, Qian YY, et al. Comparison of higher-order aberrations and contrast sensitivity between Tecnis Z9001 and CeeOn 911A intraocular lenses: a prospective randomized study. Chin Med J (Engl) 2006; 119:1779–1784
Emanuel S. Rosen, FRCSE
174
J CATARACT REFRACT SURG - VOL 33, FEBRUARY 2007