clinical and experimental study

Doctoral thesis German OPEN
Tornow, Christoph (2011)
  • Publisher: Freie Universität Berlin Universitätsbibliothek, Garystr. 39, 14195 Berlin
  • Subject: 610 Medizin und Gesundheit | 610 Medical sciences; Medicine | multifocal intraocular lens | EPCO | posterior capsule opacification
    • ddc: ddc:610
    mesheuropmc: eye diseases | genetic structures | sense organs

Posterior capsule opacity (PCO) is a frequent complication in extracapsular cataract extraction in conjunction with an intraocular lens implant. Different studies have shown that a reduction in PCO frequency can be achieved via a number of factors. Lens design is a significant criterion in this process. In this study, two multifocal intraocular lenses (MIOLs) were compared. The design of these lenses differed due to their varying optical principles. They are the refractive MIOL Allergan 154 N (R Group) and the diffractive MIOL Pharmacia 811 E (D Group). The difference in lens design resulting from the varying optical principles lies in the different posterior surface properties of the lens optics. The aim of this study was to determine whether the differences in the surface properties of the lenses lead to a different PCO rate or to a different form of posterior capsule opacity. We also sought to establish whether the two MIOLs provide differeing results in terms of visual acuity, contrast sensitivity and YAG capsulotomy rate. The study consists of a clinical and an experimental part. The clinical part takes the form of a prospective long-term study and consisted of examining patients and evaluating the data gathered. At the beginning of the study two comparable groups of patients to be examined were established. Patients in each group were each given the same intraocular lens model. The first examination as part of this study took place over a period of about four to six weeks after the lens implant [40]. The final examination as part of this study was undertaken on the R Group (154 N) after an average 5.6 years and on the D Group (811 E) after an average 5.7 years. In this investigation, digital retroillumination image photos of the MIOLs and the posterior capsule were taken and then evaluated quantitatively using EPCO software. The experimental part of the study consisted of investigating the lenses using the modified capsular bag model [43] developed by Liu et al. This showed a good correlation with clinical results [42]. The 18 donor bulbi (nine pairs of eyes) were shared between the two groups. Each group received a bulb from one pair of eyes. The IOLs were first implanted into the donor bulbi, then the capsular bags along with the IOLs were dissected out and cultivated in Petri dishes. Finally, the time that it took for a complete, confluent LEC monolayer to take shape on the posterior surface of the lens was determined. The maximum observation period was set at two months. There were no significant differences found between the posterior capsular opacity of the the types of lens examined in either of the two parts of this study. In the group of patients with the diffractive MIOL the percentage of patients receiving a YAG capsulotomy was higher than in the group with the refractive MIOL. There was no significant difference in acuity of the corrected near vision or of the uncorrected and corrected far vision. Patients in the diffractive group alone achieved better uncorrected near vision rates. The difference in uncorrected near vision of the two lenses had already been established in the first tests over a period of about four to six weeks after the lens implant and was related to the different add power of the two lenses [41]. Patients in the refractive group were found to have significantly better rates of maximum achieved contrast sensitivity. There were no differences between the two groups with regard to this criterion during the initial examination [41]. This change in contrast sensitivity can be regarded as either a consequence of the YAG capsulotomy or an effect of the different lens optics. This study showed that the differences in the design of the two lenses investigated had no significant influence on the occurrence of posterior capsule opacity. It may therefore be inferred from the study results that the rear surface properties of an intraocular lens is of only minor significance for the occurrence of PCO.
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