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PubMed1999

Image analysis of implanted rigid and foldable intraocular lenses in human eyes using Scheimpflug photography.

We evaluated the quality of imaging posterior chamber intraocular lenses (PC IOL) by Scheimpflug photography. We took photographs of 190 rigid or foldable PC IOLs using the Scheimpflug system EAS-1000 from Nidek and provided digital image analysis. We found a good imaging of PC IOLs and the cristalline lens capsule, data obtained by digital image analysis were reliable and reproducible and Scheimpflug photography could be demonstrated as a sensitive tool to show any irregularities of IOL material. Thus, we found in foldable IOLs 'glistenings', which did not have any influence on functional results and we could distinguish them from lens damage. We propose to use Scheimpflug tests regularly for the examination of implanted new types of IOLs.

Humans↗
PubMedDate not supplied

Speech perception in nucleus CI24M cochlear implant users with processor settings based on electrically evoked compound action potential thresholds.

Adjusting the speech processor of a cochlear implant, per electrode, to the individual's response is a laborious task that may interfere with a user-friendly start of implant-mediated hearing, particularly in children. This research concerns the possibility of processor adjustment based on a profile derived from measurements of the electrically evoked compound action potential (ECAP) thresholds across the electrode array, followed by adjustment of the overall level of the profile to the hearing threshold and maximum comfortable loudness level using live voice. The results for CVC word lists show that speech perception is quite insensitive to the threshold setting of the speech processor. On average, the speech score does not decrease by more than 10% when, with the new method, the threshold setting comes out so much lower that the dynamic range has doubled. In contrast, the speech score appears to be sensitive to an increase of the maximum high-frequency stimulation settings for the basal electrodes, resulting in lower scores at these higher settings. The correlation between the overall ECAP thresholds and conventionally measured subjective thresholds is weak (r = 0.64). However, the correlation between the slopes of these threshold curves is satisfactory (r = 0.82). The correlation between the ECAP thresholds and the maximum stimulation levels is poor, both with respect to overall level and slope (r = 0.39 and 0.36, respectively). Applicability of the ECAP threshold in processor adjustment could not be demonstrated in this study. Prediction of the most critical factor in speech perception, the slope of the maximum stimulation curve, from the ECAP thresholds is poor. However, considering habituation to the initial processor setting of at least 6 months, the small decrease in the CVC scores with the new setting suggests that a more user-friendly adjustment procedure can be developed.

Acoustic Stimulation↗
PubMedDate not supplied

Cochlear implantation in Mondini dysplasia.

The use of cochlear implantation to treat patients with inner ear malformations such as Mondini dysplasia has been increasingly successful. Until now, conventional hearing aids in these patients have not performed well. Consequently, the hearing problem for patients with this condition has been somewhat improved with the use of cochlear implants. Various results of cochlear implantation have been reported in these patients so far. This is a report of 5 patients with Mondini malformation who have undergone cochlear implant surgery.

Child, Preschool↗
PubMedDate not supplied

The Clarion Electrode positioner: approximation to the medial wall and current focussing?

In order to establish whether the electrical field created by a cochlear implant electrode is more focussed in a perimodiolar than in a medial position, voltages at non-stimulated electrodes were collected from the Clarion 1.2 implant before and after insertion of the Clarion Electrode Positioning System. The positioner is inserted lateral to the electrode array and is intended to bring the array close to the medial wall of the scala tympani. These intracochlear electrode voltages (IEVs) were collected in 9 surgeries with the HiFocus I electrode array with positioner. Stapedius reflex thresholds were decreased after insertion of the positioner on 20 out of 22 electrodes. Electrode impedances did not increase significantly. IEVs increased slightly for all stimulated electrodes. However, the positioner did not significantly affect the slope of the IEVs for any of the stimulated electrodes. Individual differences between patients in the mean IEV amplitude were considerable; 2 patients deafened by otosclerosis showed particularly low amplitudes. Thus, IEVs provided no evidence of a focussing of the electrical field by introducing the positioner. Possible benefits of a perimodiolar position regarding efficiency and channel separation are discussed in terms of a reduced distance between electrodes and neural elements.

Cochlear Implants↗
PubMed2004

The total artificial heart: where we stand.

The AbioCor total artificial heart (TAH) is undergoing clinical feasibility testing as destination therapy in patients with end-stage congestive heart failure. So far, the device has been implanted in 11 of a projected 15 patients. The TAH has performed reliably, providing adequate circulatory support while extending survival and improving quality of life in most recipients. Thromboembolism remains a problem but is being addressed by optimizing device and patient management and refining the anticoagulation protocol. Because the device is totally implantable and requires no penetration of the skin, infection has been minimized. All recipients so far have been men. The device is large and this limits its use in smaller patients (i.e. women, small men and children). A smaller version is being developed. Although it has yet to receive Food and Drug Administration approval, the early clinical results suggest that the AbioCor TAH may become an accepted alternative to heart transplantation for selected patients with end-stage congestive heart failure. Further investigation with regard to its primary clinical applicability, i.e. as a rescue device for sudden catastrophic heart failure, is warranted.

Aged↗
PubMed2006

Further investigation of the tolerance and mechanical adjustability of the *Acri.Tec AR-1 PC/IOL in rabbit eyes: an intraocular lens with reversibly adjustable optical power.

PURPOSE: To examine the tolerance and mechanical function of an adjustable intraocular lens (IOL) in rabbit eyes. METHODS: Implantation of the *Acri.Tec AR-1 PC/IOL into 14 rabbit eyes. Manipulation of the lens 8 weeks after implantation in order to change the refractive power. Follow-up for up to 5 months. Histopathologic examination of the eyes. RESULTS: Implantation and mechanical adjustment of the PC/IOL were possible. Eyes healed normally. No difference between eyes containing the *Acri.Tec AR-1 PC/IOL and eyes containing the control PC/IOL could be detected with respect to signs of inflammatory reaction, corneal transparency, intraocular pressure and histopathologic appearance. Histopathologic examination of the eyes showed that the *Acri.Tec AR-1 PC/IOL did not cause any damage in rabbit eyes. CONCLUSION: The *Acri.Tec AR-1 PC/IOL is well tolerated in rabbit eyes for extended periods of time, suggesting that this PC/IOL should be well tolerated in the long run. Surgical adjustment of the adjusting element can be performed with little effort several weeks after implantation.

Animals↗
PubMed1996

Cochlear implants in children.

The authors give an account of their experiences with cochlear implants on the basis of 10 years' work. Preoperative evaluation, operating methods and postoperative rehabilitation are presented. During a decade 56 operations were performed, 11 of them on children. Results with prelingually deaf children are demonstrated together with the phenomenon of hearing improvement observed on the contralateral side of the operation.

Child, Preschool↗
PubMed2000

Prosthesis-patient mismatch affects survival after aortic valve replacement.

BACKGROUND: Surgeons traditionally avoid the use of "small" aortic prostheses because of the potential for residual left ventricular outflow tract obstruction and persistent transvalvular gradients. This study examines the ratio between prosthetic valve size and the body surface area (BSA) of patients undergoing aortic valve replacement (AVR). We sought to determine the effect of potential "prosthesis-patient" mismatch on long-term survival. METHODS AND RESULTS: Follow-up was conducted on 2981 patients who underwent AVR with stented bioprostheses between 1976 and 1996. To account for differences between manufacturers' labeled valve sizes, we calculated the ratio between the prosthetic valve effective orifice area (EOA) and the patient's BSA (recorded for 2154 patients). The lowest decile in this cohort had a calculated EOA/BSA of <0.75 cm(2)/m(2) (Small group, n=227) compared with the control group (n=1927), in whom the EOA/BSA ratio was >0.75 cm(2)/m(2). Operative mortality was higher in the Small group (8% versus 5%, P:=0.03). Actuarial survival at 12 years was 50+/-5% in the Small group compared with 49+/-2% in the control group (P:=0.27). However, freedom from valve-related mortality was significantly lower in the Small group (75+/-5% versus 84+/-2%, P:=0.004). Cox regression analysis determined age and NYHA functional class to be the multivariate predictors of overall mortality, whereas advanced age and EOA/BSA <0.75 cm(2)/m(2) were found to be the predictors of valve-related mortality. CONCLUSIONS: Prosthesis-patient mismatch results in significantly higher early and late mortality after bioprosthetic AVR. We recommend careful selection of stented bioprostheses to ensure an adequate ratio of EOA to BSA. An EOA/BSA ratio of >0.75 cm(2)/m(2) may avoid residual left ventricular outflow tract obstruction and persistent transvalvular gradients. Careful prosthesis-patient matching will improve both early and late survival after AVR.

Aortic Valve↗
PubMed1999

SAS-CIS preference study in postlingually deafened adults implanted with the CLARION cochlear implant.

This study examined the speech perception performance of 71 postlingually deafened adults implanted with the CLARION Multi-Strategy Cochlear Implant. After 3 months of implant use, one third of the patients (n = 23) preferred to use the Simultaneous Analog Stimulation (SAS) strategy, and two thirds of them (n = 48) chose to use the Continuous Interleaved Sampler (CIS) strategy. The mean CID sentence scores were similar for the SAS and CIS user groups at the 3-month postoperative interval. In contrast, the mean CNC word score of the SAS users was significantly higher than the mean score of the CIS users after 3 months of implant experience. Patients who preferred to use SAS demonstrated significantly shorter duration of deafness at time of implantation than did the CIS users, whereas the CIS users demonstrated significantly higher preoperative sentence recognition scores than the SAS users. The results suggested that access to a preferred processing strategy improved the overall group performance of postlingually deafened adults in the present study compared to the results of previous studies in which only the CIS strategy was available to most patients with the Clarion.

Choice Behavior↗
PubMed1996

Control of the residual tibia in transtibial amputation.

Eight transtibial amputees had localized unremitting discomfort and pain in the distal anterior residual limb during prosthetic wear while weightbearing. Modification of the prosthetic socket did not change this pain. It was not consistent with "phantom limb" or causalgia/reflex sympathetic dystrophy-type etiologies. Thirteen randomly selected, pain-free, transtibial amputees were selected for comparison. The subjects in both groups used similar total-contact, "patellar tendon-bearing" prosthetic sockets fabricated and aligned with similar technique. The angles formed between the femur and tibia, femur and prosthetic socket, and tibia and socket were measured. Significant differences were found at each angle measurement between those patients who experienced pain and those who did not. The variable of tibia length had no effect. We conclude that bone alignment within the transtibial total-contact prosthetic socket may be partially dependent on surgical technique and not solely on prosthetic socket configuration.

Amputation, Surgical↗
PubMed2004

Music perception with cochlear implants: a review.

The acceptance of cochlear implantation as an effective and safe treatment for deafness has increased steadily over the past quarter century. The earliest devices were the first implanted prostheses found to be successful in compensating partially for lost sensory function by direct electrical stimulation of nerves. Initially, the main intention was to provide limited auditory sensations to people with profound or total sensorineural hearing impairment in both ears. Although the first cochlear implants aimed to provide patients with little more than awareness of environmental sounds and some cues to assist visual speech-reading, the technology has advanced rapidly. Currently, most people with modern cochlear implant systems can understand speech using the device alone, at least in favorable listening conditions. In recent years, an increasing research effort has been directed towards implant users' perception of nonspeech sounds, especially music. This paper reviews that research, discusses the published experimental results in terms of both psychophysical observations and device function, and concludes with some practical suggestions about how perception of music might be enhanced for implant recipients in the future. The most significant findings of past research are: (1) On average, implant users perceive rhythm about as well as listeners with normal hearing; (2) Even with technically sophisticated multiple-channel sound processors, recognition of melodies, especially without rhythmic or verbal cues, is poor, with performance at little better than chance levels for many implant users; (3) Perception of timbre, which is usually evaluated by experimental procedures that require subjects to identify musical instrument sounds, is generally unsatisfactory; (4) Implant users tend to rate the quality of musical sounds as less pleasant than listeners with normal hearing; (5) Auditory training programs that have been devised specifically to provide implant users with structured musical listening experience may improve the subjective acceptability of music that is heard through a prosthesis; (6) Pitch perception might be improved by designing innovative sound processors that use both temporal and spatial patterns of electric stimulation more effectively and precisely to overcome the inherent limitations of signal coding in existing implant systems; (7) For the growing population of implant recipients who have usable acoustic hearing, at least for low-frequency sounds, perception of music is likely to be much better with combined acoustic and electric stimulation than is typical for deaf people who rely solely on the hearing provided by their prostheses.

Audiometry↗
PubMed2004

Challenges and recent developments in hearing aids. Part II. Feedback and occlusion effect reduction strategies, laser shell manufacturing processes, and other signal processing technologies.

This is the second part of a review on the challenges and recent developments in hearing aids. Feedback and the occlusion effect pose great challenges in hearing aid design and usage. Yet, conventional solutions to feedback and the occlusion effect often create a dilemma: the solution to one often leads to the other. This review discusses the advanced signal processing strategies to reduce feedback and some new approaches to reduce the occlusion effect. Specifically, the causes of three types of feedback (acoustic, mechanical, and electromagnetic) are discussed. The strategies currently used to reduce acoustic feedback (i.e., adaptive feedback reduction algorithms using adaptive gain reduction, notch filtering, and phase cancellation strategies) and the design of new receivers that are built to reduce mechanical and electromagnetic feedback are explained. In addition, various new strategies (i.e., redesigned sound delivery devices and receiver-in-the-ear-canal hearing aid configuration) to reduce the occlusion effect are reviewed. Many manufacturers have recently adopted laser shell-manufacturing technologies to overcome problems associated with manufacturing custom hearing aid shells. The mechanisms of selected laser sintering and stereo lithographic apparatus and the properties of custom shells produced by these two processes are reviewed. Further, various new developments in hearing aid transducers, telecoils, channel-free amplification, open-platform programming options, rechargeable hearing aids, ear-level frequency modulated (FM) receivers, wireless Bluetooth FM systems, and wireless programming options are briefly explained and discussed. Finally, the applications of advanced hearing aid technologies to enhance other devices such as cochlear implants, hearing protectors, and cellular phones are discussed.

Acoustics↗
PubMed2005

Principles of digital dynamic-range compression.

This article provides an overview of dynamic-range compression in digital hearing aids. Digital technology is becoming increasingly common in hearing aids, particularly because of the processing flexibility it offers and the opportunity to create more-effective devices. The focus of the paper is on the algorithms used to build digital compression systems. Of the various approaches that can be used to design a digital hearing aid, this paper considers broadband compression, multi-channel filter banks, a frequency-domain compressor using the FFT, the side-branch design that separates the filtering operation from the frequency analysis, and the frequency-warped version of the side-branch approach that modifies the analysis frequency spacing to more closely match auditory perception. Examples of the compressor frequency resolution, group delay, and compression behavior are provided for the different design approaches.

Algorithms↗
PubMed2003

Automated, patient-interactive, spinal cord stimulator adjustment: a randomized controlled trial.

OBJECTIVE: Programmable, multicontact, implanted stimulation devices represent an important advance in spinal cord stimulation for the management of pain. They facilitate the technical goal of covering areas of pain by stimulation-evoked paresthesiae. Adjustment after implantation requires major investments of time and effort, however, if the capabilities of these devices are to be used to full advantage. The objective of maximizing coverage should be met while using practitioners' time efficiently. METHODS: We have developed a patient-interactive, computerized system designed for greater ease and safety of operation, compared with the standard external devices used to control and adjust implanted pulse generators. The system automatically and rapidly presents to the patient the contact combinations and pulse parameters specified by the practitioner. The patient adjusts the amplitude of stimulation and then records drawings of stimulation paresthesiae (for comparison with pain drawings), followed by visual analog scale ratings for each setting. Test results are analyzed and sorted to determine the optimal settings. We compared the automated, patient-interactive system with traditional, practitioner-operated, manual programming methods in a randomized controlled trial at two study centers, with 44 patients. RESULTS: The automated, patient-interactive system yielded significantly (P < 0.0001) better technical results than did traditional manual methods, in achieving coverage of pain by stimulation paresthesiae (mean 100-point visual analog scale ratings of 70 and 46, respectively). The visual analog scale ratings were higher for automated testing for 38 patients, higher for manual testing for 0 patients, and equal (tied) for 6 patients. Multivariate analysis demonstrated that the advantage of automated testing occurred independently of practitioner experience; the advantage was significantly greater, however, for experienced patients. The rate of testing (number of settings tested per unit time) was significantly (P < 0.0001) greater for the automated system, in comparison with the rate with a human operator using traditional, manual, programming methods (mean of 0.73 settings/min versus 0.49 settings/min). The automated system also identified settings with improved estimated battery life (and corresponding anticipated cost savings). No complications were observed with automated testing; one complication (transient discomfort attributable to excessive stimulation) occurred with manual testing. CONCLUSION: Automated, patient-interactive adjustment of implanted spinal cord stimulators is significantly more effective and more efficient than traditional manual methods of adjustment. It offers not only improved clinical efficacy but also potential cost savings in extending implanted battery life. It has the additional potential advantages of standardization, quality control, and record keeping, to facilitate clinical research and patient care. It should enhance the clinical application of spinal cord stimulation for the treatment of chronic intractable pain.

Adult↗