On relationship between lens optical characteristics, preoperative biometric data and clinical outcomes of patients implanted with bioanalogic polyfocal IOL Roman Chaloupka 1, Jiří Kopřiva 2, Vladimír A. Stoy 1 1 Medicem Institute, Kamenné Žehrovice, Czech Republic 2 Medical Dpt., Medicem Prague, Czech Republic Financial interests: Authors are employed by a for-profit company with an interest in the subject of the presentation.
Bioanalogic approach to IOL design WIOL-CF Inspiration from young Natural Crystalline Lens (NCL) For a long time, people are trying more or less successfully to find ideal replacement for the natural crystalline lens, which would ensure functional vision at all distances from far to near. Currently, the most widely used solution to the problem is the use of refractive or diffractive multifocal IOLs. This purely technical solution, however, has several unpleasant consequences for the patient resulting from the presence of transitions between optical zones, including low contrast sensitivity especially at mesopic conditions and occurrence of photic phenomena. It can be suggested that these difficulties are linked to incompatibility of IOL design and retinal&neural image processing needs. WIOL-CF is looking for an alternative to achieving sufficient depth of focus by seeking inspiration in the nature assuming better compatibility with retinal&neural image processing patterns. Spherical aberration (SA) seems to be a good (and retinal&neural image processing compatible) mean to achieve suffient depth of focus since NCL of a important part of the population has negative SA at a young age. Figure: Spherical aberration of the eye - from Athaide, H. V., et al. (2009). "Study of ocular aberrations with age." Arq Bras Oftalmol 72(5): 617-621. WIOL-CF - refractive power is maximal in the center and gradually decreases to the periphery Polyfocal optics with negative spherical aberration is used in order to extend the depth of focus and consequently, to achieve good vision at all distances from far to near. Moreover, the focus changes continuously with changing aperture without the presence of transitions between optical zones.
Study details Introduction Methodology The main goal of this paper is elucidation of relationship between patient s biometric data, optical properties of the implanted IOL, and quality of vision in patients implanted with bioanalogic polyfocal intraocular lens (WIOL-CF, Medicem). This bioanalogic IOL is made of an optically homogeneous hydrogel and its polyfocality (wide depth of focus due to controlled amount of negative spherical aberration) is achieved strictly by geometry of its optical surfaces. Statistical analysis of clinical results of implantations (clinical trial 2012-2013/210 eyes, post-op follow-up from 3 to 12 months) complemented by WIOL-CF optical characteristics using statistical software QC.Expert version 3.3 (TriloByte Statistical Software) aiming to find the most important predictors for good visual acuity at near (40cm), intermediate (70cm) and distance (4-6m), for photopic and mesopic contrast sensitivity and other clinical outcomes. Multidimensional linear regression was used in order to test whether the individual clinical outcomes depend on 7 possible predictors: gender, age, biometric data including axial length (AL), anterior chambre depth (ACD), keratometry (K1/K2) and manufacturing data including value of IOL spherical aberration (SA).
Factors influencing visual acuity (VA) in WIOL-CF patients Figure: Age distribution of WIOL-CF patients in the study. Monocular and binocular UCVAs at all distances in WIOL-CF patients can be found in the table below. These values demonstrate very good vision at far and intermediate distances and good functional vision at near distance. The difference between binocular and monocular UCVAs nicely illustrates the effect of binocular summation. UDVA - predictors LR coefficient estimate std. error conclusion probability abs 2,890224 1,761429 insignificant 0,102596 gender 0,012539 0,03614 insignificant 0,72903 age -0,00496 0,002128 significant 0,020873 SA -0,437578 0,187923 significant 0,021009 AL -0,049815 0,044767 insignificant 0,267318 ACD 0,076189 0,057952 insignificant 0,1903 K1-0,033424 0,042219 insignificant 0,429604 K2 0,025137 0,038569 insignificant 0,515418 UIVA - predictors LR coefficient estimate std. error conclusion probability abs -0,881552 1,455027 insignificant 0,545371 gender -0,01854 0,029244 insignificant 0,526899 age 0,001686 0,001726 insignificant 0,330113 SA 0,098991 0,15528 insignificant 0,524614 AL 0,022969 0,037003 insignificant 0,535557 ACD 0,114786 0,047877 significant 0,017535 K1/K2 0,004523 0,014161 insignificant 0,749773 UNVA - predictors LR coefficient estimate std. error conclusion probability abs -0,95659 1,451387 insignificant 0,510692 gender -0,027399 0,029779 insignificant 0,358769 age 0,002177 0,001753 insignificant 0,216079 SA 0,104793 0,154845 insignificant 0,499437 AL 0,023269 0,036887 insignificant 0,528974 ACD 0,116999 0,047751 significant 0,015246 K1-0,041831 0,034788 insignificant 0,23078 K2 0,046334 0,03178 insignificant 0,146621 Statistical analysis of clinical data using multidimensional linear regression shows that: UDVA is influenced by patient s age and slightly also by the value of spherical aberration (SA). UIVA and UNVA depend on preoperative anterior chamber depth (ACD) (they are better in patients with lower ACD) and do not depend on patient s age. This effect of ACD on near and intermediate vision should be taken into account in patients with greater ACD. binocular UDVA (dec) binocular UIVA (logmar) binocular UNVA (logmar) monocular UDVA (dec) monocular UIVA (logmar) monocular UNVA (logmar) average 0,94 0,17 0,31 0,82 0,25 0,41
Contrast Sensitivity Value in Log units Factors influencing contrast sensitivity (CSF) in WIOL-CF patients Polyfocal IOL can achieve sufficient depth of focus without compromising contrast sensitivity whereas multifocal technology decreases substantially the contrast sensitivity (see the graph below). It can be seen that the mesopic CSF of WIOL-CF patients exceeds population norm for healthy eyes of the corresponding age group. 2,5 2,0 1,5 1,0 0,5 multifocal diffractive IOL - Fine Vision * Population Norm /50-75 years/ ** mesopic Population Norm /20-55 years/ ** polyfocal IOL - WIOL-CF (mesopic CSF) 0,0 0 5 10 15 20 Spatial Frequency (c/deg) mesopic CSF - predictors LR coefficient estimate std. error conclusion probability abs 80,551452 38,990309 significant 0,041205 gender 1,118859 0,803408 insignificant 0,166562 age -0,115966 0,049421 significant 0,02076 SA -11,759276 4,285783 significant 0,007103 AL -1,022341 0,987587 insignificant 0,302871 ACD 1,531235 1,234657 insignificant 0,217561 K1-0,002464 0,849105 insignificant 0,99769 K2-0,43555 0,753979 insignificant 0,56468 Multidimensional linear regression demonstrates that both mesopic and photopic contrast sensitivities of WIOL-CF patients (see tables) depend on patient s age. It is not very surprising, since the population norm for healthy population is also age dependent. Moreover, mesopic CSF decreases slightly with the value of spherical aberration. Other factors including gender and biometric data influence neither photopic nor mesopic contrast sensitivity. Since the mesopic CSF exceeds the population norm, it seems that slight decrease of mesopic CSF with SA is clinically inconsequential. photopic CSF - predictors LR coefficient estimate std. error conclusion probability abs 36,522117 41,775014 insignificant 0,383739 gender 0,876126 0,839789 insignificant 0,298939 age -0,152111 0,051956 significant 0,004093 SA -6,234546 4,562061 insignificant 0,174325 AL -0,262286 1,048178 insignificant 0,802841 ACD 0,830469 1,278798 insignificant 0,517323 K1 0,955278 0,892029 insignificant 0,28638 K2-0,809293 0,798099 insignificant 0,312627 Figure: The graphs show mean values of contrast sensitivity, error bars correspond to standard deviations. * Alio, J.L. "Experiences with multifocal IOLs FineVision (Physiol): 1st trifocal Diffractive IOL ESCRS 2012 Milan ** Pomerance, G and D. Evans (1994). "Test-Retest Reliability of the CSV-1000 Contrast Test and Its Relationship to Glaucoma Therapy." Invest Ophthalmol Vis Sci. 35(9); 3357-3361.
IOL design with controlled amount of negative spherical aberration can lead to good vision at all distances without compromising the contrast sensitivity Statistical analysis revealed important predictors for good clinical outcomes : Better clinical outcomes including UDVA, UIVA, photopic and mesopic contrast sensitivity (CSF) and occurrence of photic phenomena can be achieved in patients of lower age. It could be due to the fact that postoperative CYL value at all distances is significantly higher in older patients. Pre-operative anterior chambre depth (ACD) influences exclusively UIVA and UNVA, better vision at intermediate and near distances can be achieved in WIOL-CF patients with smaller preoperative ACD. Spherical aberration (SA) of WIOL-CF influences slightly UDVA and mesopic contrast sensitivity (CSF). Nevertheless, even so the mesopic CSF of WIOL-CF patients exceeds population norm of corresponding age group. The slight impairment of mesopic CSF and UDVA can be expected in patients requiring WIOL-CF with higher negative SA value, as compared to WIOL-CF patients with lower SA value. This trend can be taken into account in WIOL-CF patient selection, but it is clinically inconsequential since all SA values used in WIOL- CF provide good visual acuity at all distances and excellent CSF even at mesopic conditions. Overall, the data demonstrated that: UCVA at all distances are very good in WIOL-CF patients Photopic as well as mesopic CSF of WIOL-CF patients exceed population norm WIOL-CF shows low incidence of glare and halo Conclusions Although one can assume that lenses with spherical aberration should cause lower contrast sensitivity (particularly at mesopic conditions), the polyfocal WIOL-CF do not suffer from this adverse effect. Excellent visual acuity and very good contrast sensitivity can be achieved even with an IOL having controlled amount of negative spherical aberration. The WIOL-CF spherical aberration has detrimental effect neither on photopic nor on mesopic contrast sensitivity, and provides an indisputable advantage of vision at all distances from far to near. We explain this effect by high compatibility of the retinal and neural image processing system for images projected by polyfocal optics.