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At least 1,621 records · Page 90Linked to original sources
PubMed2003

Neovascular ingrowth site photothrombosis in choroidal neovascularization associated with retinal pigment epithelial detachment.

PURPOSE: To describe the clinical, angiographic and optical coherence tomography (OCT) findings of patients with choroidal neovascularization (CNV) associated with retinal pigment epithelial detachment (PED) who were treated by neovascular ingrowth site photothrombosis. METHODS: Interventional case reports. After identification of the CNV feeder vessels, two patients had focal photothrombosis of the neovascular ingrowth site using continuous 810-nm laser application after intravenous indocyanine green (ICG) injection and were prospectively followed with fluorescein and ICG angiography as well as OCT. RESULTS: Both patients presented an increase of 3 or more ETDRS lines in visual acuity by 12 months of follow-up. Fluorescein and ICG angiography demonstrated reduced lesion perfusion and regression of the PEDs; accordingly, OCT disclosed decrease in retinal thickness and elevation caused by rapid fluid resolution. There were no significant complications related to the procedure. CONCLUSION: Photothrombosis using 810-nm light to direct laser energy continuously at the neovascular ingrowth site after intravenous ICG infusion is effective in restoring macular architecture and improving vision in patients with CNV complicated by PEDs by means of substantial decrease in the lesion perfusion and resolution of exudative manifestations.

Aged↗
PubMed2003

Changes in macular thickness and depth of anterior chamber in patients after filtration surgery.

BACKGROUND: The prospective study was undertaken to analyze retinal thickness of the macula and anterior chamber depth in patients undergoing filtration surgery at different times of follow-up. METHODS: Forty-four patients (45 eyes) were included. The thickness of the fovea and the extrafoveal retina were measured using optical coherence tomography (OCT). Anterior chamber depth was determined using the IOLMaster. All standard clinical examination and measurements were performed prior to surgery, at the 2nd day (1-3 days), 1 week, 1 month and 3 months after surgery. RESULTS: Preoperative IOP under topical medication was 25.5+/-7.5 mmHg. IOP was significantly decreased at all postoperative visits ( P<0.0001): 10.8+/-5.9 mmHg at the 2nd day, 10.4+/-5.2 mmHg after 1 week, 11.7+/-4.4 mmHg after 1 month and 11.4+/-3.6 mmHg after 3 months. No patient in our study suffered from prolonged postoperative hypotony (IOP<5 mmHg). Foveal thickness at the 2nd day, 1 week and 1 month were elevated compared with baseline ( P<0.004). Macular thickness changed from 164+/-20 microm before surgery to 168+/-20 microm after 2 days, 170+/-21 microm after 1 week, 173+/-19 microm after 1 month and 165+/-16 microm after 3 months. Mean thickness of the extrafoveal retina did not change significantly. Also, there were no significant changes in anterior chamber depth. There was no significant correlation between reduction of IOP and retinal thickness or anterior chamber depth. CONCLUSION: The reduction of IOP after filtration surgery leads to a moderate increase in foveal retinal thickness over approximately 1 month and is not associated with shallowing of the anterior chamber, provided that prolonged postoperative hypotony is avoided with the surgical technique used.

Adult↗
PubMed2003

Laser interference biometry versus ultrasound biometry in certain clinical conditions.

PURPOSE: To compare laser interference biometry (LIB) with conventional ultrasound biometry in certain clinical conditions such as globe deformities, eccentric fixation, retinal detachment, macular edema or silicone oil-filled eyes. SETTING: Department of Ophthalmology, Würzburg University Eye Hospital, Germany. METHODS: We evaluated all patients who came to our university hospital for axial length measurement with our routine immersion biometry system (Grieshaber Biometry System) and compared the results with those obtained using the Zeiss IOLMaster of Carl Zeiss Jena, the commercially available LIB device. RESULTS: Selected case reports demonstrate the advantages and disadvantages of LIB. Advantages of LIB were found in patients with asymmetrically shaped globes, eccentric fixation, silicone oil-filled eyes and a fearful/nervous disposition. Disadvantages of the system were revealed in cases of retinal detachment, severe opacities along the visual axis and poor patient cooperation. CONCLUSION: We showed that LIB is a valuable addition to the choice of biometric devices, when used with medical understanding.

Aged↗
PubMed2001

Optical coherence tomography (OCT) findings in normal retina and laser-induced choroidal neovascularization in rats.

BACKGROUND: To evaluate the optical coherence tomographic (OCT) features of the retina of rats, we compared the OCT images with the histological appearance of normal retinas and retinas with laser-induced choroidal neovascularization. METHODS: Twelve eyes of 12 adult pigmented rats (Brown-Norway) were used. Color fundus photography, fluorescein angiography (FAG), and OCT images of normal retinas and retinas with laser photocoagulation-induced choroidal neovascularization were studied. RESULTS: OCT showed a double-layered structure in the normal sensory retina with a highly reflective layer located in the inner retina and a low reflective layer located in the outer retina. The retinal pigment epithelium (RPE) and choriocapillaris were imaged as a layer with the highest reflection. On the first day after photocoagulation, OCT showed a disruption of the highly reflective layer corresponding to the RPE, and an enhanced reflectivity in the choroid under the lesion. Choroidal neovascularizations (CNVs) which appeared 2 weeks after photocoagulation was seen as a multi-layered, highly reflective area protruding from the RPE into the subretinal space A CNV beneath a subretinal hematoma was difficult to detect because of the low transmission of the scanning light through the hematoma. The histopathological appearance was well correlated with the OCT images. CONCLUSION: The two reflective bands in the OCT images were identified as coming from the inner layers of the retina and from the photoreceptors. The highest reflective band arose from the RPE and choriocapillaris. In the future, OCT combined with FAG or indocyanine-green angiography will be a useful tool for the evaluation of animal studies of choroidal neovascularization and other retinal diseases.

Animals↗
PubMed2001

Morphological and functional analyses of diabetic macular edema by optical coherence tomography and multifocal electroretinograms.

PURPOSE: To determine the correlation between the tomographic features and the visual functions of eyes with diabetic macular edema. METHODS: Optical coherence tomographic (OCT) images and multifocal electroretinograms were obtained from 45 eyes of 25 patients with diabetic macular edema and from 21 eyes of 21 normal subjects. RESULTS: The OCT images showed cystoid macular edema in 18 eyes and diffuse retinal swelling without cystoid edema in the other 27 eyes. The fovea was significantly thicker in eyes with cystoid macular edema and in those with diffuse retinal swelling than in normal eyes. The fovea of eyes with cystoid edema was significantly thicker than the fovea of eyes with diffuse swelling. The best-corrected visual acuity and the electrical response density from the macular area were significantly reduced in eyes with diabetic macular edema, particularly in those with cystoid edema. The best-corrected visual acuity and macular response density of the multifocal ERGs were inversely correlated, and the implicit times were directly correlated with foveal thickness. CONCLUSION: The visual acuity was correlated significantly with morphological changes revealed by OCT and with multifocal ERGs. The combination of OCT and multifocal ERGs may provide objective criteria for the evaluation and assessment of diabetic macular edema.

Adult↗
PubMed2000

Slit-lamp-adapted optical coherence tomography of the anterior segment.

PURPOSE: To evaluate the diagnostic potential of a slit-lamp-adapted optical coherence tomography (OCT) system as an in vivo imaging device for routine clinical examination of the anterior segment of the eye. PATIENTS AND METHODS: In a pilot study, healthy volunteers and patients with different pathologies of the anterior segment were examined with a slit-lamp-adapted OCT system using 100-200 axial scans with 100-Hz line-scan frequency. The scan length is variable up to 7 mm, and the axial depth is 1.5 mm in tissue. RESULTS: The slit-lamp-adapted OCT system allowed direct biomicroscopic imaging of the measured area. Anatomic structures and morphological changes anterior to the attenuating iris pigment epithelium could be visualized with high accuracy. Biometric analyses of the cornea, the chamber angle, the iris and secondary cataract were possible. Complete demonstration of the chamber angle was difficult due to the backscattering properties of the anterior part of the sclera and the consequent shadowing of the most peripheral part of the iris. CONCLUSIONS: Slit-lamp-adapted OCT is a useful diagnostic tool which allows in vivo microscopic cross-sectional imaging of the anterior segment and precise measurement of ocular structures.

Anterior Eye Segment↗
PubMed1998

Limitations of imaging choroidal tumors in vivo by optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) produces two-dimensional cross-sectional images with a longitudinal resolution of 10 microns. Its capacity for imaging retinal structure has been shown in a variety of diseases. There are no reports on its capacity and limitations in imaging choriocapillary and choroidal structures. METHODS: Twenty-two patients with the diagnosis of malignant melanoma of the choroid were submitted to OCT. We used a prototype and a commercial device, both with an 850-nm superluminescent diode with a band-width of 30 nm (reported longitudinal resolution 10 microns). The images were evaluated for retinal thickness, changes in retinal pigment epithelium, subretinal fluid accumulation and changes in choriocapillary or choroidal reflectivity. RESULTS: Retinal edema and detachment found on biomicroscopic examination for fluorescein angiography was detected by OCT in all such cases. In 2 of 22 cases small retinal detachments were detected only by OCT. Tumor extension through the retinal pigment epithelium was not seen in this series, either by biomicroscopy or by OCT. The pattern of choroidal or choriocapillary reflectivity was nonspecifically lower than that of normal choroid, but did not yield any additional information about tumor histology. When normal retina was present, the OCT appearance of a malignant melanoma resembled that of normal choroid. CONCLUSION: OCT may provide information about the retinal structure overlying prominent tumors and the extent of adjacent retinal detachment. In its present state of development, OCT is of little value in the differential diagnosis of choroidal tumors. Its potential value for the follow-up of shallow tumors needs further investigation.

Adult↗
PubMed2001

Staging of idiopathic choroidal neovascularization by optical coherence tomography.

PURPOSE: To assess the clinical course of idiopathic choroidal neovascularization (ICNV) by optical coherence tomography (OCT). METHODS: Thirty-two patients with a clinical diagnosis of ICNV were examined between December 1995 and October 1999. The ages of the patients ranged from 18 to 53 (mean 35.9) years, and the mean period of observation was 5.8 months. Color fundus photography, fluorescein angiography, Indocyanine green angiography, and OCT were performed. The stage of the ICNV was classified as active, intermediate, or cicatricial, based on past history, fundus findings, and fluorescein angiography (FAG). The characteristic OCT images at these three stages were determined. RESULTS: OCT revealed that there were characteristic tomographic images of the choroidal neovascularization (CNV) at each stage. In the active stage, OCT revealed the CNV as a highly reflective, multi-layered area protruding into the subretinal space. In the intermediate stage, the reflectivity of the CNV became stronger and its margin in the subretinal space became smooth. With regression of the ICNV, the lesions consisted of two different areas: a most reflective area corresponding to the fibrotic changes of the CNV (imaged white in OCT images), and a reddish highly reflective area representing a compound protrusion of the CNV. In the cicatricial stage, the ICNV was observed as a moderately high reflective area covered by a dome-shaped highly reflective layer corresponding to the retinal pigment epithelium. CONCLUSION: These findings demonstrated clearly the changes in the OCT images during the development and regression of ICNV. OCT was useful for following the clinical course and understanding the mechanism of the CNV regression.

Adolescent↗
PubMed2001

Thinning and small holes at an impending tear of a retinal pigment epithelial detachment.

BACKGROUND: A tear of a retinal pigment epithelial detachment (PED) suddenly exposes a large area of bare Bruch's membrane. We report here the case of a patient whom we observed during the gradual, spontaneous development of a PED tear. METHOD: A 5.25-year case study of a 67-year-old woman with bilateral serous PEDs. RESULTS: Retinal pigment epithelial (RPE) thinning or small holes were seen along the PED margin in both eyes. Fluorescein angiograms showed intense hyperfluorescence without leakage, and indocyanine green angiography showed choroidal vessels through regions of RPE thinning or small holes. Optical coherence tomographs showed an interruption of a hyperreflective band corresponding to retinal pigment epithelium. A typical tear of the PED ensued later. CONCLUSION: Multiple, small regions of RPE thinning or holes along the margin of PED can be a sign of an impending PED tear.

Aged↗
PubMed2001

Surgical posterior vitreous detachment combined with gas/air tamponade for treating macular edema associated with branch retinal vein occlusion: retinal tomography and visual outcome.

PURPOSE: To assess the effectiveness of surgical posterior vitreous detachment (PVD) together with gas/air tamponade in treating visual impairment from macular edema associated with branch retinal vein occlusion (BRVO-macular edema). METHODS: A cohort study was conducted. To treat visual disturbance caused by BRVO-macular edema in 19 consecutive patients at a University Hospital, phacoemulsification, intraocular lens implantation, and vitrectomy were performed, together with gas/air tamponade. Patients were followed up postoperatively for 3-18 months. Foveal structure was defined using optical coherence tomography (OCT). Preoperative visual acuity, central retinal thickness, and interval between BRVO onset and operation were compared between patients with postoperative visual improvement and those without improvement. RESULTS: Ten patients recovered normal or near-normal foveal configuration, while nine patients did not. Mean postoperative visual acuity in the former group of patients was significantly higher than in the latter. Mean foveal retinal thickness decreased significantly after the operation. The interval from onset of BRVO until operation was significantly shorter in patients with improved postoperative vision than in other patients, and patients operated on within 11 months had significantly increased postoperative visual acuity. CONCLUSIONS: Surgical PVD and gas/air tamponade appears effective in treating BRVO-macular edema, although relatively short duration from disease onset until operation is critical for improvement of vision. When a good postoperative foveal contour is seen, it seems to be associated with better visual outcome.

Adult↗
PubMed2005

Hydrodynamic detection by cupulae in a lateral line canal: functional relations between physics and physiology.

In the present review, signal-processing capabilities of the canal lateral line organ imposed by its peripheral architecture are quantified in terms of a limited set of measurable physical parameters. It is demonstrated that cupulae in the lateral line canal organ can only partly be described as canal fluid velocity detectors. Deviation from velocity detection may result from resonance, and can be characterized by the extent to which a single dimensionless resonance number, N ( r ), exceeds 1. This number depends on four physical parameters: it is proportional to cupular size, cupular sliding stiffness and canal fluid density, and inversely proportional to the square of fluid viscosity. Situated in a canal, a cupula may benefit from its resonance by compensating for the limited frequency range of water motion that is efficiently transferred into the lateral line canal. The peripheral transfer of hydrodynamic signals, via canal and cupula, leads to a nearly constant sensitivity to outside water acceleration in a bandwidth that ranges from d.c. to a cut-off frequency of up to several hundreds of Hertz, significantly exceeding the cut-off frequency of the lateral line canal. Threshold values of hydrodynamic detection by the canal lateral line organ are derived in terms of water displacement, water velocity, water acceleration and water pressure gradients and are shown to be close to the detection limits imposed by hair cell mechano-transduction in combination with the physical constraints of peripheral lateral line signal transfer. The notion that the combination of canal- and cupular hydrodynamics effectively provides the lateral line canal organ with a constant sensitivity to water acceleration at low frequencies so that it consequently functions as a low-pass detector of pressure gradients, supports the appropriateness of describing it as a sense organ that "feels at a distance" (Dijkgraaf in Biol Rev 38:51-105, 1963).

Animals↗
PubMed2000

Feasibility of optical coherence tomography for high-resolution imaging of human gastrointestinal tract malignancies.

Optical coherence tomography (OCT) is a new imaging technology which can perform high-resolution, cross-sectional imaging of the internal microstructure of biological tissues. OCT is analogous to ultrasound, except that it measures the intensity of back-reflected infrared light rather than sound waves. OCT performs two- and three-dimensional imaging of tissue microstructure in situ and in real time. It can achieve image resolutions approaching the cellular level over approximately the same imaging depths as a conventional biopsy. In this article we examine the feasibility of OCT for high-resolution imaging of gastrointestinal malignancies with ex-vivo imaging of normal and pathologic microstructures. Tissue, both normal and neoplastic, was obtained from patients undergoing surgical resection after an initial diagnosis of a gastrointestinal malignancy. The tissue samples were imaged prior to fixation using a laboratory OCT system. The OCT system consists of a fiber optic-based Michelson interferometer, a commercially available amplified superluminscent light source, and a computer for data acquisition. The images were subsequently compared with histological cross-sections corresponding to the imaged areas. The stratified squamous epithelium of the normal esophagus was clearly visible in the OCT images and contrasted to the disorganized and non-uniform nature of the mucosal layers of Barrett's esophagus and squamous carcinoma. The columnar epithelial morphology as well as other mucosal structures in normal colon were distinctly visible using OCT. In contrast, disorganization of the normal mucosal layers and ulcerative lesions were identified in tissues from ulcerative colitis and adenocarcinoma of the colon. The ability of OCT to image tissue microstructure at high resolutions makes it a potentially powerful technology for minimally invasive assessment of the gastrointestinal tract and the evaluation of early neoplastic changes.

Adenocarcinoma↗
PubMed2006

Quasi-static transfer function of the rabbit middle ear' measured with a heterodyne interferometer with high-resolution position decoder.

Due to changes in ambient pressure and to the gas-exchange processes in the middle ear (ME) cavity, the ear is subject to ultra-low-frequency pressure variations, which are many orders of magnitude larger than the loudest acoustic pressures. Little quantitative data exist on how ME mechanics deals with these large quasi-static pressure changes and because of this lack of data, only few efforts could be made to incorporate quasi-static behavior into computer models. When designing and modeling ossicle prostheses and implantable ME hearing aids, the effects of large ossicle movements caused by quasi-static pressures should be taken into account. We investigated the response of the ME to slowly varying pressures by measuring the displacement of the umbo and the stapes in rabbit with a heterodyne interferometer with position decoder. Displacement versus pressure curves were obtained at linear pressure change rates between 200 Pa/s and 1.5 kPa/s, with amplitude +/-2.5 kPa. The change in stapes position associated with a pressure change is independent of pressure change rate (34 microm peak-to-peak at +/-2.5 kPa). The stapes displacement versus pressure curves are highly nonlinear and level off for pressures beyond +/-1 kPa. Stapes motion shows no measurable hysteresis at 1.5 kPa/s, which demonstrates that the annular ligament has little viscoelasticity. Hysteresis increases strongly at the lowest pressure change rates. The stapes moves in phase with the umbo and with pressure, but the sense of rotation of the hysteresis loop of stapes is phase inversed. Stapes motion is not a simple lever ratio mimic of umbo motion, but is the consequence of complex changes in ossicle joints and ossicle position. The change in umbo position produced by a +/-2.5 kPa pressure change decreases with increasing rate from 165 microm at 200 Pa/s to 118 microm at 1.5 kPa/s. Umbo motion already shows significant hysteresis at 1.5 kPa/s, but hysteresis increases further as pressure change rate decreases. We conclude that in the quasi-static regime, ossicle movement is not only governed by viscoelasticity, but that other effects become dominant as pressure change rate decreases below 1 kPa/s. The increasing hysteresis can be caused by increasing friction as speed of movement decreases, and incorporating speed-dependent friction coefficients will be essential to generate realistic models of ossicle movements at slow pressure change rates.

Animals↗
PubMed2003

Silicone antifoam performance enhancement by nonionic surfactants in potato medium.

The ability of a silicone antifoam to retard foaming in a liquor prepared from potatoes is enhanced by the addition of ethoxylated nonionic surfactants. The enhancement is non-linear for surfactant concentration, with all 12 surfactants tested possessing a concentration at which foam heights strongly diminish, referred to as the surfactant critical antifoaming concentration (SCAFC). SCAFCs vary between surfactants, with lower values indicating better mass efficiency of antifoaming enhancement. SCAFCs decrease with degree of ethoxylation and decrease with the hydrophilic-lipophilic balance for ethoxylated nonionic surfactants. Surfactant addition produces a mixed water-surface layer containing surfactant and surface-active components in the potato medium. Surface tension reduction does not correlate well with antifoam performance enhancement. A model is proposed where surfactant adsorption promotes desorption of surface-active potato medium components from the water surface. At the SCAFC, desorption is not complete, yet the rate of bubble rupture is sufficiently enhanced to provide excellent foam control.

Antifoaming Agents↗
PubMed2006

A new miniaturised optical system for chemical species spectroscopic detection based on a scanning integrated Mach-Zehnder microinterferometer on LiNbO3.

Absorption or emission spectroscopy is a powerful tool for detecting chemical compounds, diluted in fluid media: the sensitivity of this technique depends on the optical path of the source radiation, on the spectral window used for analysis and on the spectrometer performances. In this view, we designed and produced the first prototypes of an integrated scanning Fourier Transform Microinterferometer with Mach-Zehnder geometry, by using MEOS (Micro Electro Optical Systems) technologies. The microdevice, obtained by fabricating integrated optical waveguides on LiNbO(3) (LN) crystals, is electrically driven, without moving parts, by exploiting the electrooptical properties of the material. The microdevice operates the Fourier Transform of the input radiation spectral distribution, which can be reconstructed starting from the output signal by means of Fast Fourier Transform (FFT) techniques. The microinterferometer weights few grams, the power consumption is of a few mW and, in principle, can operate in the LN transmittance range (0.36-4.5 microm). The microinterferometer performances were preliminary tested in the (0.4-1.7 microm) spectral window. In the Visible region (0.4-0.7 mum) this microsystem demonstrated a spectral resolution suitable for detecting the characteristic lines of the solar spectrum together with the absorption bands of common gases present in Earth's atmosphere. In a further experiment we tested its performances for gas trace detection by using a calibrated NO(2) optical gas cell, showing the possibility to reveal up to 10 ppb, when suitable optical paths are used. Finally, colorimetry tests for the titration of an organic dye (E131) in alcohol solution are presented.

Crystallization↗
PubMed2006

The effect of the lipid layer on tear film behaviour.

This paper investigates the effect of surfactants during tear film deposition and subsequent thinning. The surfactants occur naturally on the surface of the tear film in the form of a lipid layer. A lubrication model is developed that describes lipid spreading and film height evolution. It is shown that lipids may play an important role in drawing the tear film up the cornea during the opening phase of the blink. Further, nonuniform distributions of lipids may lead to a rapid thinning of the tear film behind the advancing lipid front (shock). Experiments using a fluorescein dye technique and using a tearscope were undertaken in order to visualise the motion of the lipid layer and any associated shocks immediately after a blink. It is found that the lipid layer continues to spread upwards on the cornea after the opening phase of the blink, in agreement with the model. Using the experimental data, lipid particles were tracked in order to determine the surface velocity and these results are compared to the model predictions.

Blinking↗
PubMed1983

Laser interferometric prediction of postoperative visual acuity in patients with cataracts.

I used the laser interferometer to test 137 eyes to determine whether preoperative interference visual acuity tests could accurately predict postoperative Snellen visual acuities. In 60 patients with immature cataracts and normal maculas the postoperative Snellen visual acuity was predictable within one line in 53 patients and within two lines in seven others. In 29 other patients with cataracts and senile macular scars or macular degeneration without subretinal fluid postoperative Snellen visual acuity was predictable within one line in 26 patients and within two lines in two others. Several easily recognizable clinical conditions make the interferometer test unreliable. Those that produce false-positive responses are serous detachment of the sensory epithelium of the macula, cystoid macular edema, visual fields cut through fixation, amblyopia, macular holes or cysts, geographic atrophy of the pigment epithelium of the macula, and early postoperative retinal detachment. Those that produce false-negative responses are mature cataracts and testing without pupillary dilatation.

Cataract↗
PubMed1988

A clinical index for predicting visual acuity after cataract surgery.

We developed a clinical index for predicting postoperative visual acuity of cataract patients and cross-validated it using data from 182 patients aged 70 years and older. The index consisted of four statistically combined indicators: age, preoperative visual acuity, frequency of reading, and comorbidity. Validation of the index included comparisons to two standard technical instruments for measurement of retinal visual acuity. For the clinical index, 72% of predictions were accurate within one Snellen line of postoperative visual acuity compared to 37% using a laser interferometer and 33% using a potential acuity meter. Testing of the clinical index's external validity using data from 111 patients in a different ophthalmology clinic disclosed 61% of predictions accurate within one Snellen line.

Aged↗