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PubMed1999

Predictive validity of a procedure for pediatric hearing instrument fitting.

In 1994, Moodie, Seewald, & Sinclair described the development of a clinical procedure for predicting real-ear hearing instrument performance in young children. The purpose of the present study was to determine the validity of this procedure for predicting the real-ear aided gain (REAG) and real-ear saturation response (RESR) of hearing instruments worn by children. To this end, both the REAG and RESR were measured, through probe-microphone measures, and predicted, using the Moodie et al. procedure. The findings confirmed that the 2-cc coupler-based procedure, with individualized acoustic transforms, described by Moodie et al., resulted in highly accurate predictions of real-ear hearing instrument performance for both REAG and RESR at five test frequencies. The implications of these findings for the clinical fitting of hearing instruments in infants and young children are discussed.

Acoustic Stimulation↗
PubMed2003

Predicted gain and functional gain with transcranial routing of signal completely-in-the-canal hearing aids.

Transcranial routing of signal (TCROS) was accomplished using completely-in-the-canal (CIC) hearing aids in 5 profoundly unilaterally hearing-impaired individuals. The functional gain realized by the participants far exceeded the gain predicted by measuring the acoustic output and real ear aided response of the hearing aids. The difference between predicted and functional gain increased with signal frequency and was attributed at least in part to mechanical vibration of the hearing aid in the external canal. Implications for fitting unilateral hearing loss using TCROS amplifying systems are discussed.

Aged↗
PubMed2005

Manufacturer predicted and measured REAR values in adult hearing aid fitting: accuracy and clinical usefulness.

Audiologists may fit hearing aids using real-ear aided response (REAR) values predicted by manufacturer's fitting software, rather than actual measured REARs. This study examined how well one manufacturer's software was able to predict REARs for a DSP behind-the-ear product in 41 adults (N = 79 ears) under four conditions (two hearing loss configurations and two inputs). Results showed that for all ears tested, measured REAR values were significantly different from predicted for most of the audiometric frequencies for all four test conditions. Discrepancies between measured and predicted REAR values were greater in males' ears than females'. Few ears' REAR values (< or = 12%) were judged to be clinically similar to predicted. Results suggest audiologists should consider using individual real-ear measures in adult hearing aid fittings until manufacturer software is shown to accurately predict real-ear hearing aid performance.

Adult↗
PubMed1995

Probe-tube microphone measures with very young infants: real ear to coupler differences and longitudinal changes in real ear unaided response.

OBJECTIVE: The feasibility and practicalities of performing probe-tube microphone measures with infants is addressed, as well as two aspects of acoustic functioning of infant ears: the real ear unaided response (REUR) and the real ear to coupler difference (RECD). DESIGN: Part 1 is a longitudinal study involving 12 infants. Serial measures of REUR were obtained over an 18-mo period. Infants were < or = 3 mo for the first test and < or = 21 mo at the last test visit. Practicalities of probe-tube microphone testing of unsedated infants and changes in the position (i.e., frequency) of the primary REUR peak were addressed. For part 2 of the project, 33 infants under 12 mo of age took part. A comparison of real ear hearing aid gain versus coupler gain was made. Test-retest differences for real ear aided response were estimated. RESULTS: Part 1 results indicate that probe-tube microphone measures in unsedated infants are feasible and show good within-subject repeatability. REUR measures for the more alert and mobile older subjects, as for the younger infants, showed an acceptably small degree of intersubject variability. The frequency of the primary REUR peak decreased during the first year of life, with a group mean of 2932 Hz reached at the end of the first year. However, thereafter, instead of stabilizing at around this value there was considerable fluctuation in the frequency of REUR peak. For Part 2, results a) confirmed the large RECD value for infants in the first year of life and b) showed a high degree of intersubject variability. Test retest measures of real ear aided response (REAR) gave values small enough to indicate the clear potential of probe-microphone use with infants during the hearing aid selection and fitting process. CONCLUSION: These findings should encourage attempts to carry out individual probe-tube microphone measurements with very young infants. They point to the need for infant hearing aid fitting procedures which involve such measurements to secure appropriate amplification.

Amplifiers, Electronic↗
PubMed2000

Four earplugs in search of a rating system.

OBJECTIVE: The performance of four insert earplugs was evaluated by determining the Noise Reduction Rating (NRR) and the Subject-Fit Noise Reduction Rating [NRR(SF)]. The NRR and NRR(SF) were calculated from real-ear attenuation at threshold (REAT) data collected using the experimenter-fit protocol described in the now-rescinded ANSI S3.19-1974 (American National Standards Institute, 1974) and the subject-fit protocol of the recently revised ANSI S12.6-1997 (American National Standards Institute, 1997) standards for REAT measurement. DESIGN: A comparison of the experimenter-fit and subject-fit REAT performance was conducted using four pools of subjects, one pool per protector. Each device was tested with at least 20 subjects, the minimum size necessary to estimate the NRR(SF) for an earplug. The REAT was measured with third-octave narrowband noise stimuli for center frequencies at 0.125, 0.25,0.5, 1, 2, 3.15, 4, 6.3, and 8 kHz. The REAT means and standard deviations were compared with the manufacturer data. RESULTS: This study showed that the NRR(SF) is typically lower than the NRR and that the NRR(SF) is not well-predicted by the NRR derating schemes recommended by the National Institute for Occupational Safety and Health and required by the Occupational Safety and Health Administration. CONCLUSION: The difference between the present NRR on hearing protector labels and the NRR(SF) is sufficiently large and unpredictable enough to render the application of derating schemes meaningless even though these schemes attempt to account for the difference between the laboratory and real-world outcomes. The only way to provide a protector noise rating that is predictive of a real-world outcome is to retest the protector according to the subject-fit method of ANSI S12.6-1997 (American National Standards Institute, 1997).

Auditory Threshold↗
PubMed2000

Pediatric prosthetics. Current trends and future possibilities.

The child's growing, ever-changing nature presents a dynamic challenge to clinics that provide pediatric prostheses for children. Over the years clinics have developed strategies for prescribing and fitting pediatric prostheses. As new components, materials, or techniques are introduced, management of children with limb deficiencies may begin to take on a new look as well.

Artificial Limbs↗
PubMed2002

[Workshop of military reconstructive surgery in Conakry May 1999: example of civilian-military cooperation in responding to medical-surgical crisis emergencies].

During the period from 1998 to 1999, civil wars broke out in number of west African countries including Liberia, Sierra Leone, and Guinea Bissau. Due to the situation in surrounding countries, Guinea Conakry was forced to accept nearly 650000 refugees whose presence represented a major risk for the socio-political stability of the country. International organizations and NGOs condemned the atrocities inflicted on civilian populations by the children serving as soldiers in the RUF rebels organizations of Sierra Leone and Liberia. These attacks included murders, gang rapes, abduction of children and young people, and mutilation of extremities of people of all ages ranging from infants to elderly. Treatment of mutilation victims requires the availability of facilities for surgical treatment and prosthetic fitting in Guinea Conakry. The humanitarian action division of the French Foreign Affairs Department and the NGO Handicap International decided to provide specialized training in the management of mutilation injuries to surgical groups in hospitals of Guinea and Sierra Leone. The program consisted in a workshop on reconstructive surgery for war-related injuries to allow optimal prosthetic fitting for reinsertion of mutilation victims into society.

Adolescent↗
PubMed1995

Reaming technique of the femoral diaphysis in cementless total hip arthroplasty.

Distal fixation enhances initial torsional stability of cementless femoral components in primary and revision total hip arthroplasty. Surgical technique affects the quality of distal fixation, and too aggressive a technique can cause femoral fracture during insertion of the stem. Thirty-five adult human cadaveric femoral specimens were implanted with either a standard or long femoral stem. Control specimens were reamed 0.5 mm less than the diameter of the distal cylindrical portion of the stem and were broached line to line proximally. The proximal femur was removed from the remaining specimens to allow assessment of distal fixation. The controls outperformed the distal-only fixation groups in all testing modes, illustrating that proximal and distal fixation work in concert to resist torsional load. The average failure torque in underreamed specimens with only distal fixation was 23.6 Nm for standard length stem specimens and 41.3 Nm for long stem specimens, whereas the average failure torque for specimens with only distal fixation prepared by a line-to-line reaming technique was only 6 Nm. The estimated length of tight distal fit should be 10 to 40 mm to obtain sufficient initial torsional stability of the stem and still avoid intraoperative femoral fracture.

Adult↗
PubMed1997

Long-term stability of fitting parameters with the COMBI 40.

Having experience with the COMBI 40 for over two years, it is now possible to look at the development of patient fittings over a longer period of time. In this study we look at patient fitting data (thresholds, dynamic ranges, etc.) at two days, one month, three months, six months and twelve months post first fitting. Subjects are CI-users participating in the COMBI 40 European Multicentric Study. Long-term fitting parameters show a favourable development. Stable fitting parameters and the safety features implemented in the COMBI 40 serve as a basis for a reliable long-term speech understanding.

Auditory Threshold↗
PubMed2000

Controlled polymerization system for fabricating precise dentures.

STATEMENT OF PROBLEM: Most processed resin denture bases do not fit the cast accurately because of polymerization changes in the resin. The fit is more noticeable in the palate between the denture base and the cast. Therefore, development of a polymerization system that will improve the fit of a denture base to the cast is lack of worth considering to improve the fit and retention of the denture. PURPOSE: A newly developed polymerization system for dentures is presented that results in excellent adaptability of the denture base to the cast when compared with 2 other polymerization systems. MATERIAL AND METHODS: Forty-five maxillary dentures were made with 3 resins and 3 polymerization systems (a new polymerization system, SR-Ivocap system, original microwave polymerization system). Each denture and cast was sectioned through the second molar area parallel to the posterior border. Discrepancies between denture base and stone cast were measured at several points immediately after polymerization and after 30 days of immersion in water. In addition, disks of 3 materials processed in each system were examined for absorption of water and hardness at 2 measurement stages. Data were analyzed with the split-plot or 2-way ANOVA test. RESULTS: Dentures made with the new polymerization system had significantly smaller discrepancies, compared with dentures processed with the SR-Ivocap system and the microwave method. The amount of water absorption of the resin disks processed by the new system was less than the disks made by the other 2 systems. Dentures made with the new system exhibited significantly better adaptation to the cast than those made with the other 2 systems. CONCLUSION: The new polymerization system produced a more accurate method of processing dentures when fit was compared with the fit of dentures made with the other 2 denture base resins.

Acrylic Resins↗
PubMed2001

Survey of hearing aid fitting practices for children with multiple impairments.

The fitting of amplification on young children with multiple impairments in addition to hearing loss is a challenge faced regularly by audiologists. However, very little has been published on this topic in the audiological literature. The purpose of this survey was to document hearing aid fitting practices for this population within the United States. Specifically, audiologists who regularly serve children were asked to complete a series of questions on their educational preparation and their hearing aid selection, fitting, and verification practices for children with multiple impairments. For purposes of this survey, multiple impairments included vision impairment, mental retardation, physical impairment, and autism spectrum disorders. Findings from this survey suggest that children with special needs in addition to hearing loss are typically fit in the same way and with the same type of amplification as those with hearing loss only. In addition, differences were noted in hearing aid selection, fitting, and verification practices across work settings. Future directions and research needs are suggested.

Abnormalities, Multiple↗
PubMed2000

Presence of microorganisms on the fitting denture complete surface: study 'in vivo'.

It was the intention to study if glazing the fitting surface of maxillary dentures with a light-curing acrylic resin would diminish the bacterial counts. The study included the application of a photopolymerizing glaze to one half of the fitting denture surface; after 15 days microbial plaque was collected from a 1 cm2 area of the glazed and the untreated resin, respectively. At the same time bacteria were collected from a 1 cm2 area of the corresponding sites on the palatal mucosa. The application of the glaze had modified the number of bacteria cultured from the glazed surface versus the untreated surface. Denture surface: total aerobic bacteria, 1:4; aerobic streptococci, 1:4; aerobic staphylococci, 1:5; anaerobic bacteria, 1:3.5; mucosal surface aerobic bacteria, 1:4; streptococcal, 1:4. The differences were statistically significant at P<0.002. However, from a quantitative and qualitative point of view these differences were minor compared with the actual concentrations of the microorganisms of 104-106/cm2 observed on the fitting denture surface and the palatal mucosa.

Acrylic Resins↗
PubMed2002

Cochlear implantation in a patient with superficial siderosis of the central nervous system.

OBJECTIVE: To perform an assessment of the viability of cochlear implantation in a patient with superficial siderosis of the brain. STUDY DESIGN: Case review. SETTING: Tertiary referral center. PATIENTS: Patient with superficial siderosis of the brain. INTERVENTION: Cochlear implantation. MAIN OUTCOME MEASURES: Electrically evoked auditory brainstem responses and fitting strategy for cochlear implant based on patient's subjective responses. RESULTS: After some time, C levels and T levels showed a pattern comparable with the evoked auditory brainstem responses. CONCLUSIONS: Bilateral profound hearing loss after superficial siderosis of the brain is no absolute contraindication for implantation. Furthermore, evoked auditory brainstem measurements can potentially guide the fitting process of the implant in difficult cases.

Brain Diseases↗
PubMed2004

Contact lens prescribing in a specialist medical contact lens clinic based in an NHS hospital: an audit of changing practice.

PURPOSE: To describe the range of indications for contact lenses and the types of lenses being used in an NHS hospital-based specialist medical contact lens clinic and contrast this with information from 12 years ago. METHODS: A retrospective audit of 596 clinic attendances was performed in the contact lens clinic at the Western Eye Hospital between April 2002 and March 2003. The results were compared with a similar audit performed in 1991. We used the hospitals electronic records, and information on contact lens prescribing was obtained directly from the receipts generated by the contact lens department and the accounts department. RESULTS: We saw 392 patients with 88.5% of patients requiring 2 or less visits per year. The majority of referrals are for high myopia (28.6%) closely followed by aphakia (25.2%) and keratoconus (24.7%). This is in contrast to 1991 when 68% of referrals were for aphakia and twice as many myopes (17%) were seen as keratoconus patients (8%). A total of 560 lenses were prescribed with 68 different types of lens in use. The seven most commonly used lens types accounted for 61% of all lenses prescribed. CONCLUSIONS: Medical contact lens clinics provide a specialist service and also provide an important training resource for junior ophthalmologists. Safer cataract surgical techniques have had a significant impact on the case mix seen in our clinic, with the emphasis moving away from aphakic and myopic patients and toward the more challenging to fit eyes with keratoconus or postcorneal surgery.

Adolescent↗
PubMed2000

Use of a loudness model for hearing aid fitting. IV. Fitting hearing aids with multi-channel compression so as to restore 'normal' loudness for speech at different levels.

Many researchers have proposed that multi-channel compression hearing aids should process sounds so as to restore loudness perception to 'normal'. However, procedures for achieving this have generally been based on measurements or calculations using narrowband stimuli, and these procedures may not be accurate for broadband sounds such as speech. Here, a model for predicting loudness for people with cochlear hearing loss is used to calculate the frequency- and level-dependent gains that would be required to restore loudness perception to 'normal' for speech-like signals. The calculations are based entirely on the pure tone audiogram, and do not require measures of loudness growth. The model was applied to several different hypothetical hearing losses, varying in slope and severity. In each case, the model was used to calculate the insertion gains (IGs) that would be required as a function of frequency so that speech-shaped noise with a level of 65 dB SPL would evoke a specific loudness pattern matching that for a normal ear. A similar procedure was applied using speech-shaped noise with a level of 85 dB SPL (with the spectral characteristics of shouted speech). The results were used to derive functions relating the required IG to hearing loss for each audiometric frequency and each speech-shaped noise level. These functions were used in turn to derive compression ratios and gains for each channel of a multi-channel compression system. The derivations apply to systems with any number of channels. The outcome is a method than can be used for the initial fitting of multichannel compression hearing aids, so as to restore loudness perception to near 'normal' for broadband speech-like signals.

Acoustic Stimulation↗
PubMed1999

Use of a loudness model for hearing aid fitting: II. Hearing aids with multi-channel compression.

A model for predicting loudness for people with cochlear hearing loss was applied to the problem of the initial fitting of a multi-channel compression hearing aid. The fitting was based on two constraints: (1) The specific loudness pattern evoked by speech of a moderate level (65 dB SPL) should be reasonably flat (equal loudness per critical band), and the overall loudness should be similar to that evoked in a normal listener by 65-dB speech (about 23 sones for binaural listening); (2) Speech with an overall level of 45 dB SPL should just be audible in all frequency bands from 500 Hz up to about 4 kHz, provided that this does not require compression ratios exceeding about 3. These two constraints were used to determine initial values for the gain, compression ratio and compression threshold in each channel of a multi-channel compression system. This initial fitting was based entirely on audiometric thresholds; it does not require suprathreshold loudness measures. The fitting method was evaluated using an experimental fast-acting four-channel compression system. The initial fitting was followed by an adaptive procedure to 'fine tune' the fitting, and the aids were then used in everyday life. Performance was evaluated by use of questionnaires and by measures of speech intelligibility. Although the fine tuning resulted in modest changes in the fitting parameters for some subjects, on average the frequency response shapes and compression ratios were similar before and after the fine tuning. The fittings led to satisfactory loudness impressions in everyday life and to high speech intelligibility over a wide range of levels. It was concluded that the initial fitting method gives reasonable starting values for the fine tuning.

Acoustic Stimulation↗
PubMed2000

Contact lens fitting difficulties following refractive surgery for high myopia.

PURPOSE: To describe the clinical and optical problems encountered in contact lens fitting following refractive surgery for high myopia. METHODS: Following refractive surgery for high myopia (greater than -10.00 D) we corrected residual refractive errors with contact lenses in the four eyes of two patients. The first patient had undergone bilateral laser in situ keratomileusis (LASIK),with two subsequent LASIK retreatments in the left eye. Ten months later she was fit with rigid gas permeable (RGP) lenses in both eyes. The second patient had undergone a clear lens extraction in the right eye and radial keratotomy followed by photorefractive keratectomy(PRK) in the left eye. She was fit with toric soft lenses six years postoperatively. RESULTS: Final visual acuity obtained with contact lenses was 20/25-20/20 in all eyes. The first patient required significant minus lens power compensation. Furthermore, the RGP lens in the left eye was slightly decentered due to corneal irregularity induced by LASIK. The second patient had regular corneal surfaces and was successfully fit with daily wear toric soft lenses despite the 2.75 D of residual astigmatism in the left eye. CONCLUSIONS: Following refractive surgery for high myopia a proportion of patients will remain undercorrected. In these patients the alterations in corneal architecture that ensue make contact lens fitting more challenging. Patients with regular astigmatism may be fitted successfully with toric soft lenses. Patients with corneal irregularities should be fit with RGP lenses.

Adult↗
PubMed2002

Clinical performance and factors affecting the physical fit of a soft toric frequent replacement contact lens.

BACKGROUND: Differences in ocular parameters between Chinese and Caucasian eyes may lead to differences in the success rate of soft contact lens fittings. As most disposable or frequent replacement lenses are manufactured based on data of Caucasian eyes, the aim of this study was to investigate the clinical performance and factors affecting the preliminary fitting of a 'one-fit' bi-weekly replacement soft toric lens on Hong Kong (HK)-Chinese. METHOD: Forty-one HK-Chinese were fitted with Acuvue soft toric lenses (on one eye only). The success rate, the comfort, vision and the effects of central corneal curvature, horizontal visible iris diameter (HVID) and palpebral aperture size (PAS) on the physical fit of the toric lenses were determined. RESULTS: Twenty-four of 41 eyes (58.6 per cent) attained acceptable fit and satisfactory vision with these lenses. The main reason for unsuccessful lens fit was loose fitting. Only central corneal curvatures were significantly correlated (statistically) to the looseness of the lens. DISCUSSION: The results showed that about 40 per cent of our subjects were unable to obtain acceptable fit with this one-fit frequent replacement lens, the main reason for which was loose fit. This was expected due to the steeper corneas of the Chinese eyes and we would expect similar results with other one-fit soft lenses. Only the central corneal radii were significantly correlated with the looseness of the lens fit. However, this factor was not the main factor affecting the contact lens fitting. HVID and PAS did not appear to play any significant role in the physical fit of this lens. As there are individual variations of lens fitting behaviour, trial lens fitting assessment is the most suitable way to select the appropriate lens.

Adolescent↗