Speech processing studies using an acoustic model of a multiple-channel cochlear implant.

The speech perception of two multiple-channel cochlear implant patients was compared with that of three normally hearing listeners using an acoustic model of the implant for 22 different speech tests. The tests used included a minimal auditory capabilities battery, both closed-set and open-set word and sentence tests, speech tracking and a 12-consonant confusion study using nonsense syllables. The acoustic model represented electrical current pulses by bursts of noise and the effects of different electrodes were represented by using bandpass filters with different center frequencies. All subjects used a speech processor that coded the fundamental voicing frequency of speech as a pulse rate and the second formant frequency of speech as the electrode position in the cochlea, or the center frequency of the bandpass filter. Very good agreement was found for the two groups of subjects, indicating that the acoustic model is a useful tool for the development and evaluation of alternative cochlear implant speech processing strategies.

Glare disability in eyes with intraocular lenses.

For 32 eyes tested for glare disability after undergoing extracapsular cataract extraction with implantation of posterior chamber intraocular lenses, the mean contrast threshold in the presence of the glare source was 23% for undilated pupils and 31% with dilation. A regression analysis of glare scores as a function of the amount of posterior capsule opacification showed a significant (P less than .00001) association between the two.

Clinical trial of a multiple-channel cochlear prosthesis. An initial study in four patients with profound total hearing loss.

The clinical trial of a multiple-channel cochlear prosthesis was undertaken in four patients with postlingual deafness and profound total hearing loss. The results of open-set speech tests confirmed that, using electrical stimulation alone, one patient could have a meaningful conversation without resorting to lipreading (for example, this patient uses the prosthesis to converse with her husband on the telephone). The results of closed-set speech tests also suggested that a multiple-channel stimulator is more effective than a single-channel one in conveying speech information. The cochlear prosthesis was especially effective in all four patients when it was used in conjunction with lipreading, and speech-tracking tests showed that the patients could combine the information obtained from both electrical stimulation and lipreading.

Bilateral intraocular lens implantation.

A study of 1796 consecutive cataract patients in a posterior chamber intraocular lens implant (IOL) series revealed 373 patients (20.8%) who had bilateral IOLs. Visual acuity was 20/40 or better in 87% of first eyes operated and 90% in second eyes. The major cause of vision less than 20/40 was senile macular choroidal degeneration in both first and second eyes. The surgical reintervention rate was 11.8% in first eyes and 3.7% in second eyes. Ninety-two percent of patients had an interval of six months or more between surgery on the first and second eyes.

A fluorescein angiographic study of cystoid macular edema.

We performed a prospective fluorescein angiographic study on 66 patients who had undergone extracapsular cataract extractions with implantation of a Shearing posterior chamber intraocular lens. A primary posterior capsulotomy was performed in every case. The eyes were studied 11 to 23 months postoperatively. The incidence of cystoid macular edema (3%) was lower than that found in three series of cataract extractions previously reported. Extracapsular cataract extraction with either (1) a Shearing posterior chamber intraocular lens and a primary posterior capsulotomy or (2) a Binkhorst intraocular lens and an intact posterior capsule produces a lower rate of cystoid macular edema than does intracapsular cataract extraction either with a Binkhorst intraocular lens or without an intraocular lens. There was no significant difference in the incidence of cystoid macular edema in the two extracapsular series, indicating that preservation of an intact posterior capsule was not a significant factor.