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Biomedical subjects

R Gerl

Publications and source records attributed to R Gerl.

4 recordsLinked to original sources
PubMed2001

[Accommodative lens implant].

PROBLEM: To date, approaches to restore accommodation following cataract surgery have been based on the principle of a liquid or solid implant that moves within the capsular bag and thereby changes the optical characteristics of the eye. However, these implants have been associated with shrinking and fibrosis of the capsular bag, a problem that will not be solved in the foreseeable future. APPROACH: If accommodation is effected by shifting the whole capsule including its contents on the optical axis, capsular fibrosis will virtually no longer play a role. In order to execute this shift via the neuronal feedback mechanisms of the ciliary muscle in a controlled way, radial zonular forces or movements must be transformed into axial ones, which is possible by means of tiny permanent magnets. This paper describes the basic aspects of such an implant. The dependence of accommodation on all relevant parameters is quantified in a computer simulation. CONCLUSION: The implant described appears to be practicable with justifiable technical and surgical efforts.

Accommodation, Ocular↗
PubMed1999

Pathological examination of an explanted phakic posterior chamber intraocular lens.

PURPOSE: To report the clinicopathological correlation of an explanted phakic posterior chamber intraocular lens (PPC IOL) and to study the conformation of this lens implanted into human eyes obtained postmortem. SETTING: Center for Research on Ocular Therapeutics and Biodevices, Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: Three silicone PPC IOLs were explanted. One lens, explanted from a 38-year-old woman with complicated cataract, was submitted for pathological analysis. In addition to gross and scanning electron microscopy (SEM), the lens was studied after experimental implantation in human eyes obtained postmortem using frontal, posterior, and side-view techniques. RESULTS: Although gross and SEM showed that the IOL was well polished, examination of the lens in human cadaver eyes showed it was oversized and poorly fixated. It was relatively bulky in its anterior-posterior dimension and revealed evidence of significant contact with the iris and crystalline lens. CONCLUSIONS: This study illustrates many pitfalls to be avoided in the design of a plate PPC IOL. The lens in this report was too large, and instead of ciliary sulcus fixation, it showed poor fixation through the zonules onto the posterior face of the pars plicata. Present and future PPC IOLs should be submitted for similar preclinical studies to clarify the type and site of fixation.

Adult↗
PubMed1985

A large section of the gene locus encoding human immunoglobulin variable regions of the kappa type is duplicated.

The structure of a new segment of the gene locus encoding the variable regions of human immunoglobulins of the Kappa type (VK) has been elucidated. This segment (cluster B) encompasses six VK sequences, which belong to three different subgroups and which are arranged in the same transcriptional orientation. Part of cluster B was found to be very similar to another region of the VK gene locus, which was cloned previously (cluster A). Sequence differences between the homologous region of clusters A and B range from 0.2% to 3.7% depending on the position of the VK sequences. The divergence is in the same range for genes and pseudogenes. Hybridization experiments with DNAs from different individuals clearly demonstrate that the two segments are located at different positions within the VK locus and do not represent allelic variants. The sequence homology between clusters A and B is higher than the homology of both clusters to an allelic variant, which is represented by a DNA segment that had been isolated from another individual. These results, together with a report in the literature of two other homologous regions in the VK locus, make it very likely that a major part of even the whole locus is duplicated. In this case, VK gene numbers would be higher than previously estimated on the basis of hybridization studies. An inverse orientation of VK gene clusters would explain published data on rearrangement products in B-cells if an inversion-deletion mechanism is assumed.

Alleles↗