Biomedical subjects

T Akin

Publications and source records attributed to T Akin.

9 recordsLinked to original sources

PubMed2003

The effect of capsulorhexis size on development of posterior capsule opacification: small (4.5 to 5.0 mm) versus large (6.0 to 7.0 mm).

PURPOSE: The most common surgically related cause of reduced vision after extracapsular cataract extraction is posterior capsule opacification (PCO), which occurs in up to 50% of eyes following cataract extraction. This study examined whether small capsulorhexes of 4.5 to 5.0 mm, which lie completely on the 5.5 mm intraocular lens (IOL), and large capsulorhexes of 6.0 to 7.0 mm, which lie completely off the lens optic, are effective in preventing PCO development. METHODS: In this prospective study, 496 eyes of 367 patients underwent standardized phacoemulsification with capsulorhexis and capsular bag foldable acrylic IOL implantation. The patients were randomly assigned to receive either a small capsulorhexis of 4.5 to 5 mm to lie completely on the IOL optic or a large capsulorhexis of 6 to 7 mm to lie completely off the lens optic. Retroillumination photographs were taken at 6 months and then yearly. RESULTS: Throughout the follow-up, there was less PCO in the small capsulorhexis group than in the large capsulorhexis group. CONCLUSIONS.:Small capsulorhexes were associated with less wrinkling of the posterior capsule and less PCO than were large capsulorhexes. PCO after IOL implantation has a multifactored pathogenesis. Small (4.5 to 5.0 mm) capsulorhexis and capsular bag implantation of 5.5 mm acrylic IOL are likely to reduce the PCO incidence when compared with the 6.0 to 7.0 mm capsulorhexis. The significance of the IOL optic diameter in association with the capsulorhexis size should also be documented by further studies.

Aged↗

PubMed1999

A modular micromachined high-density connector system for biomedical applications.

This paper presents a high-density, modular, low-profile, small, and removable connector system developed using micromachining technologies for biomedical applications. This system consists of a silicon or polyimide electrode with one end in contact with the biological tissue and its back-end supported in a titanium base (12.5 mm in diameter and 2.5 mm in height) that is fixed on the test subject. An external glass substrate (6 x 6 x 0.75 mm3), which supports a flexible polyimide diaphragm and CMOS buffers, is attached to the titanium base whenever electrical contact is required. The polyimide flexible diaphragm contains high-density gold electroplated pads (32 pads, each having an area of 100 x 100 micron 2 and separated by 150 microns) which match similar pads on the electrode back-end. When vacuum is applied between the two, the polyimide diaphragm deflects and the corresponding gold pads touch, therefore, establishing electrical connection. In vitro electrical tests in saline solution have been performed on a 32-site connector system demonstrating < 5 omega contact resistance, which remained stable after 70 connections, and -55 dB crosstalk at 1 kHz between adjacent channels. In vivo experiments have also confirmed the establishment of multiple contacts and have produced simultaneous biopotential recordings from the guinea pig occipital cortex.

Animals↗

PubMed1997

Long term chronic recordings from peripheral sensory fibers using a sieve electrode array.

The use of an implanted micromachined silicon sieve electrode array to make long term chronic recordings from the glossopharyngeal nerve is described. The implant consists of an array of small holes in a silicon substrate, four of which are surrounded by electrodes connected with an integrally fabricated ribbon cable to a percutaneous headcap. Using this device we have been able to monitor the integrity of the electrodes from the time of implantation and subsequently to record evoked sensory responses from mechanoreceptors on the tongue.

Animals↗

PubMed1994

A micromachined silicon sieve electrode for nerve regeneration applications.

A micromachined silicon sieve electrode has been developed and fabricated to record from and stimulate axons/fibers of the peripheral nervous system by utilizing the nerve regeneration principle. The electrode consists of a 15-microns-thick silicon support rim, a 4-microns-thick diaphragm containing different size holes to allow nerve regeneration, thin-film iridium recording/stimulating sites, and an integrated silicon ribbon cable, all fabricated using boron etch-step and silicon micromachining techniques. The thin diaphragm is patterned using reactive ion etching to obtain different size holes with diameters as small as 1 micron and center-center spacings as small as 10 microns. The holes are surrounded by 100-200 microns 2 anodized iridium oxide sites, which can be used for both recording and stimulation. These sites have impedances of less than 100 k omega @ 1 kHz and charge delivery capacities in the 4-6 mC/cm2 range. The fabrication process is single-sided, has high yield, requires only five masks, and is compatible with integrated multilead silicon ribbon cables. The electrodes were implanted between the cut ends of peripheral taste fibers of rats (glossopharyngeal nerve), and axons functionally regenerated through holes, responding to chemical, mechanical, and thermal stimuli.

Animals↗

PubMed1992

Functional regeneration of glossopharyngeal nerve through micromachined sieve electrode arrays.

To assess the potential of micromachined silicon sieve electrodes for long term recordings from single afferent sensory fibers, we implanted them between the cut ends of rat glossopharyngeal nerves which innervate taste and somatosensory receptors on the posterior tongue. After the implants had been in place for an average of 101 days nerve regeneration was measured using histological and electrophysiological methods. Axons of the glossopharyngeal nerve regenerated through holes in the sieves and supported the functional regeneration of taste, thermal and mechanoreceptors.

Animals↗

PubMedDate not supplied

Review of sterile, postoperative, anterior segment inflammation following cataract extraction and intraocular lens implantation.

PURPOSE: To evaluate unexpected, acute intraocular anterior segment inflammation following uneventful cataract extraction by phacoemulsification and foldable posterior chamber intraocular lens (PCIOL) implantation. METHODS: This retrospective study evaluated five cases of postoperative inflammation that occurred after cataract extraction with foldable PCIOL implantation. Medical records were reviewed to analyze the unexplained postoperative inflammation. RESULTS: The five patients who developed inflammatory activity during the postoperative period responded well to corticosteroid treatment. Toxic maculopathy developed in one patient after aggressive antibacterial therapy. Vitrectomy was performed for one patient with prolonged vitreal inflammatory activity. CONCLUSIONS: Noninfectious endophthalmitis developing upon surgery may be caused by a multifactorial process or an interindividual variable response to a common factor as a hypersensitivity reaction. It should be remembered in inflammatory cases after surgery in order to prevent the toxic, irreversible side effects of bacterial endophthalmitis treatment.

Acute Disease↗

PubMedDate not supplied

The effects of three-piece or single-piece acrylic intraocular lens implantation on posterior capsule opacification.

PURPOSE: To evaluate the development of posterior capsule opacification (PCO) in patients implanted with 5.5 mm optics, single-piece or three-piece acrylic intraocular lens (IOL) in cataract surgery prospectively. METHODS: This study was carried out on 267 eyes of 249 patients implanted with three-piece, 5.5 mm optics, acrylic IOL and 252 eyes of 244 patients implanted with single-piece, 5.5 mm optics, acrylic IOL by phacoemulsification technique between September 2001 and February 2003. A total of 519 eyes of 493 patients were prospectively evaluated for PCO development during the 25-month period. All the patients were analyzed periodically with anterior segment retroillumination photography. The data provided were analyzed with chi-square method. RESULTS: The results between the two groups for PCO development were not statistically significant. However, there was a prominent opacification of the posterior capsule where the optic and haptic junction of IOL was positioned in some patients implanted with single-piece IOL. During the follow-up period, no patients implanted with either three-piece or single-piece acrylic IOL required Nd:YAG laser capsulotomy. CONCLUSIONS: Biocompatibility and reduced rate of PCO development are among the leading features of new generation IOLs. The intracapsular implantation of 5.5 mm optics acrylic IOLs resulted in decreased incidence of PCO and therefore greater patient satisfaction. Further studies investigating the effects of IOL optics, haptic structure and length, capsulorrhexis size, and IOL material and design features on PCO development will clarify the subject.

Acrylic Resins↗

PubMedDate not supplied

The effect of hyperbaric oxygen on intraocular pressure.

The effects of hyperoxia on intraocular pressure (IOP) have been studied in experiments on human beings and animals. The changes occurring in IOP in patients during routine HBO2 therapy are unknown. In this study we investigated IOP changes arising during the HBO2 therapy at 2.5 ATA. Fifty-six patients receiving HBO2 therapy for various reasons were included in the study. Bilateral IOPs of patients measured with the Tono-pen XL (Medtronic, Solan, USA) tonometer before, during and after HBO2 therapy. Average IOPs were 14.85 +/- 3.17 mmHg (range, 10-24), 13.00 +/- 2.97 mmHg (range, 9-21) and 14.74 +/- 3.12 mmHg (range, 10-22), respectively. IOP was reduced significantly during HBO2 therapy and returned its pre- HBO2 levels after therapy. Our data indicated a statistically significant decrease in IOPs during therapy at 2.5 ATA. This decrease was of minor physiological significance in these patients whose baseline IOP values were within the normal range.

Adult↗

PubMedDate not supplied

The effects of artificial tear application on contrast sensitivity in dry and normal eyes.

PURPOSE: To investigate the effects of artificial tear application on contrast sensitivity in dry and normal eyes. METHODS: A total of 55 patients with normal (10/10) corrected or uncorrected visual acuity referring to GATA Gulhane Military Medical Academy Haydarpasa Ophthalmology Outpatient Clinic were evaluated in regard to dry eye diagnostic criteria, and assigned into the dry eye group (Group 1; 35 patients) and the control group (Group 2; 20 patients). All patients were given a contrast sensitivity testing at low and high spatial frequencies using the gradual contrast sensitivity chart before and at 5 minutes after application of artificial tears, and the two groups were compared. Wilcoxon test was used in statistical analysis, accepting a p value of <0.05 as significant. RESULTS: In the dry eye group, there was a statistically significant increase in contrast sensitivity scores both at low and high frequencies after application of artificial tears (p<0.05). In the control group, although there was a significant increase in low frequency scores after artificial tear application (p< 0.05), there was not a significant change in high frequency scores (p>0.05). CONCLUSIONS: The decreased contrast sensitivity in dry eyes improves with application of artificial tears. Therefore, the impeded quality of vision seen in dry eye patients could be restored closer to normal with artificial tear therapy. Besides, contrast sensitivity testing could be used in the follow-up of artificial tear therapy.

Adult↗