Argon laser trabeculoplasty for intractable glaucoma following intravitreal triamcinolone.
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Adult↗
Biomedical subjects
Francesco Viola
Publications and source records attributed to Francesco Viola.
Lamina puncture for central retinal vein occlusion: results of a pilot trial.
OBJECTIVE: To evaluate the effect of treatment by lamina puncture, a novel procedure to create a perivascular opening within the optic nerve head by a transvitreal approach, on visual acuity after central retinal vein occlusion (CRVO) in older patients. METHODS: The patients comprised a nonrandomized, consecutive, interventional case series of older patients being seen with CRVO. Patients 65 years or older with CRVO and a visual acuity of 20/200 or worse were treated with vitrectomy and lamina puncture of the optic disc. Preoperative visual acuity, clinical examination results, and fluorescein angiography results were compared with postoperative results. RESULTS: Twenty patients (12 men and 8 women), an average age of 72 years, were enrolled. The mean duration of CRVO was 5.4 months; 14 eyes had nonischemic CRVO when first seen, while 6 had substantial ischemia. The mean preoperative visual acuity was in the counting fingers range, and the mean postoperative visual acuity was also in the counting fingers range. Complications included 5 eyes with iris neovascularization, of which 4 progressed to neovascular glaucoma; also, preoperative ischemia seemed to predispose to neovascular complications. CONCLUSION: Lamina puncture does not restore visual acuity in older patients with CRVO.
Aged↗
A comparison between spline-based and phase-domain time-delay estimators.
We previously presented a novel time-delay estimator that uses cubic splines to estimate continuous time delays from sampled data. Previous simulation results showed that the spline-based algorithm yields superior performance when compared to the normalized correlation and the sum squared differences (SSD) algorithms implementing a variety of subsample interpolators. In this short communication, we present additional simulation results that compare the spline-based time-delay estimator to well-known phase-domain estimators. Under comparable conditions, spline-based methods exhibit biases approximately one tenth and standard deviation only one hundredth of those observed for the phase-based approaches.
Letter↗
Treatment of retinal angiomatous proliferation in age-related macular degeneration: a series of 104 cases of retinal angiomatous proliferation.
OBJECTIVE: To report the management of retinal angiomatous proliferation (RAP), a recently described intraretinal neovascular lesion occurring in age-related macular degeneration. METHODS: This was a retrospective review of consecutive patients with age-related macular degeneration who underwent treatment of RAP from January 1, 2000, through January 31, 2003. Inclusion criteria were age 55 years or older, signs of age-related macular degeneration, and diagnosis of RAP based on dynamic indocyanine green angiography. Baseline angiograms were reviewed and RAP was classified into the following 3 stages: stage 1, intraretinal neovascularization, early stage; stage 2, subretinal neovascularization, middle stage; and stage 3, choroidal neovascularization, late stage. Treatment and concomitant treatment results were assessed separately for each RAP stage. The clinical data were statistically analyzed (chi2 test and analysis of variance) for 2 main outcome measures--complete obliteration of the lesion and final visual acuity. RESULTS: Eighty-one patients (99 eyes) with 104 RAPs were identified. Forty-two lesions were at stage 1, 42 at stage 2, and 20 at stage 3. The following 5 treatments were performed: direct laser photocoagulation of the vascular lesion, laser photocoagulation of the feeder retinal arteriole, scatter "gridlike" laser photocoagulation, photodynamic therapy, and transpupillary thermotherapy. Complete obliteration of RAP was achieved in about 24 (57.1%) of the stage 1 lesions (direct laser photocoagulation of the vascular lesion, 73% success rate; photodynamic therapy, 45%), 11 (26.2%) of the stage 2 lesions (scatter gridlike laser photocoagulation, 38% success rate; direct laser photocoagulation of the vascular lesion, 17%), and only 3 (15.0%) of stage 3 lesions (P = .001). Predictive factors with a significant effect on final visual acuity were initial visual acuity (P = .003) and early lesion stage (P = .04). Best final visual acuity was 0.41 (mean, direct laser photocoagulation of the vascular lesion in stage 1) and 0.39 (mean, photodynamic therapy in stage 1), with a mean decrease of 2.5 and 3 lines from baseline, respectively. CONCLUSIONS: Treatment of RAP remains difficult. Early detection of the lesion and subsequent direct conventional laser photocoagulation seems to be associated with better anatomical and functional outcome. Once the vascular complex is well established, anatomical closure is rarely achieved. Further study is warranted to assess the long-term efficacy and the need for re-treatment.
Aged↗
Scanning laser ophthalmoscopy and angiography with a wide-field contact lens system.
OBJECTIVE: To perform fluorescein and indocyanine green angiography for large or peripheral chorioretinal structures using a contact lens system that provides a 5-fold increase in the field of view of a confocal scanning laser ophthalmoscope (SLO). METHODS: Separate handheld contact and noncontact ophthalmoscopic lenses were manually aligned with the optical axis of a confocal SLO to demonstrate the feasibility of wide-field SLO angiography. An integrated, wide-field contact lens system was then designed and constructed to increase the SLO's 10 degrees , 20 degrees , and 30 degrees imaging fields to 50 degrees , 100 degrees , and 150 degrees , respectively. RESULTS: Simultaneous fluorescein and indocyanine green angiography was performed with the integrated, wide-field contact lens system for more than 50 patients with disorders that affect their peripheral retina and choroid. Retinal and choroidal abnormalities, including neovascularization and capillary nonperfusion, are easily detected and documented well beyond the range of conventional fundus cameras and SLOs. Peripheral retinal and choroidal hemodynamics can be readily observed and recorded. CONCLUSIONS: A confocal SLO has adequate resolution for clinically useful reflectance and angiographic imaging even when its field size is increased 5-fold by a wide-field contact lens system. Dynamic and static wide-field angiography can be performed without the limitations of manual or computer-automated photomontages. Peripheral retinal conditions can be studied and recorded to confirm observations from indirect ophthalmoscopy and to facilitate retinal photocoagulation and vitreoretinal surgery.
Adult↗
Dystrophic calcification of the fibrous capsule around a hydrogel explant 13 years after scleral buckling surgery: capsular calcification of a hydrogel explant.
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Adult↗
A spline-based algorithm for continuous time-delay estimation using sampled data.
Time delay estimation (TDE) lies at the heart of signal processing algorithms in a broad range of application areas, including communications, coherent imaging, speech processing, and acoustics. In medical ultrasound for example, TDE is used in blood flow estimation, tissue motion measurement, tissue elasticity estimation, phase aberration correction, and a number of other algorithms. Because of its central significance, TDE accuracy, precision, and computational cost are of critical importance. Furthermore, because TDE is typically performed on sampled signals-and delay estimates are usually desired over a continuous domain-time delay estimator performance should be considered in conjunction with associated interpolation. In this paper we present a new time-delay estimator that directly determines continuous time-delay estimates from sampled data. The technique forms a spline-based, piecewise continuous representation of the reference signal then solves for the minimum of the sum squared error between the reference and the delayed signals to determine their relative time delay. Computer simulation results clearly show that the proposed algorithm significantly outperforms other algorithms in terms of jitter and bias over a broad range of conditions. We also describe a modified version of the algorithm that includes companding with only a minor increase in computational cost.
Algorithms↗
Ocular hypotony secondary to spontaneously ruptured sclera in choroidal coloboma.
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Choroid Diseases↗
Sonorheometry: a noncontact method for the dynamic assessment of thrombosis.
Inappropriate blood coagulation plays a central role in the onset of myocardial infarction, stroke, pulmonary embolism, and other thrombotic disorders. The ability to screen for an increased propensity to clot could prevent the onset of such events by appropriately identifying those at risk and enabling prophylactic treatment. Similarly, the ability to characterize the mechanical properties of clots in vivo might improve patient outcomes by better informing treatment strategies. We have developed a technique called sonorheometry. Unlike existing methods, sonorheometry is able to assess mechanical properties of coagulation with minimal disturbance to the delicate structure of a forming thrombus. Sonorheometry uses acoustic radiation force to produce small, localized displacements within the sample. Time delay estimation is performed on returned ultrasound echoes to determine sample deformation. Mechanical modeling and parametric fitting to experimental data yield maps of mechanical properties. Sonorheometry is well suited to both in vitro and in vivo applications. A control experiment was performed to verify that sonorheometry provides mechanical characterization in agreement with that from a conventional rheometer. We also examined thrombosis in blood samples taken from four subjects. This data suggests that sonorheometry may offer a novel and valuable method for assessing the thrombogenicity of blood samples.
Blood↗
A comparison of the performance of time-delay estimators in medical ultrasound.
Time-delay estimation (TDE) is a common operation in ultrasound signal processing. In applications such as blood flow estimation, elastography, phase aberration correction, and many more, the quality of final results is heavily dependent upon the performance of the time-delay estimator implemented. In the past years, several algorithms have been developed and applied in medical ultrasound, sonar, radar, and other fields. In this paper we analyze the performances of the widely used normalized and non-normalized correlations, along with normalized covariance, sum absolute differences (SAD), sum squared differences (SSD), hybrid-sign correlation, polarity-coincidence correlation, and the Meyr-Spies method. These techniques have been applied to simulated ultrasound radio frequency (RF) data under a variety of conditions. We show how parameters, which include center frequency, fractional bandwidth, kernel window size, signal decorrelation, and signal-to-noise ratio (SNR) affect the quality of the delay estimate. Simulation results also are compared with a theoretical performance limit set by the Cramér-Rao lower bound (CRLB). Results show that, for high SNR, high signal correlation, and large kernel size, all of the algorithms closely match the theoretical bound, with relative performances that vary by as much as 20%. As conditions degrade, the performances of various algorithms differ more significantly. For signals with a correlation level of 0.98, SNR of 30 dB, center frequency of 5 MHz with a fractional bandwidth of 0.5, and kernel size of 2 micros, the standard deviation of the jitter error is on the order of few nanoseconds. Normalized correlation, normalized covariance, and SSD have an approximately equal jitter error of 2.23 ns (the value predicted by the CRLB is 2.073 ns), whereas the polarity-coincidence correlation performs less well with a jitter error of 2.74 ns.
Algorithms↗
Radiation force imaging of viscoelastic properties with reduced artifacts.
It is well-known that changes in the mechanical properties of tissues are correlated with the presence of disease. In the eye, for example, the vitreous body undergoes dramatic changes in mechanical properties during age-related degradation. These changes may play a significant role in the formation of retinal detachment or other vitreoretinal diseases. We previously presented a noninvasive method called kinetic acoustic vitreoretial examination (KAVE), which may be used to detect these mechanical changes. KAVE uses acoustic radiation force as a means to produce small, localized displacements within the tissues. Returning echoes are processed using ultrasonic motion tracking so that the response of the tissue to the induced force can be evaluated. By repeating this process at a number of locations, images depicting viscoelastic properties of tissues can be formed. Through the combination of appropriate mechanical modeling and signal processing, we are able to generate images of parameters such as relative mass, relative elasticity, and relative viscosity. These parameters are called relative because they depend on the force applied, which is typically unknown. In this paper, we present new force-free images depicting the time constant tau, the damping ratio xi, and the natural frequency omega of the phantom material. These images are significant in that they lack the artifacts common in the relative property images. Experiments were conducted on a set of three acrylamide-based phantoms with varying gel concentrations. We present images depicting B-mode echogenicity, maximum radiation force-induced displacement, relative material parameters, and force-free characteristics of the series of phantoms. The presented force-free images depict mechanical properties without artifacts from local force variation due to acoustic reflection, refraction, and attenuation. Force-free images should prove particularly useful for in vivo imaging through inhomogeneous tissues.
Artifacts↗
Development and characterization of a vitreous mimicking material for radiation force imaging.
In many medical ultrasound applications tissue-mimicking phantoms are of fundamental importance for the performance of controlled experiments. Traditionally, such phantoms have been constructed using gelatin and agar gels. Although the use of these materials has become standard, few alternative materials have not been fully explored. In this paper, we present a protocol developed in our laboratory that reliably produces very soft, acrylamide-based phantoms that can mimic both acoustical and mechanical characteristics of the vitreous body of the eye. Following the described protocol, a series of phantoms were constructed ranging in acrylamide concentration from 1.60% to 1.70%. Measurements across the series yielded attenuation coefficients of 0.067-0.140 dB/cm/MHz, depending on acrylamide concentration. Speed of sound ranged between 1499 and 1510 m/s, also depending on acrylamide concentration. Published values for the vitreous gel indicate an attenuation of 0.10 dB/cm/MHz and a speed of sound of 1510 m/s, making our phantoms an excellent analog of this tissue. One application of these acrylamide phantoms is to test the efficacy of the Kinetic Acoustic Vitreoretinal Examination (KAVE), a tool developed in our laboratory with the potential to aid in the diagnosis of vitreoretinal disorders. KAVE utilizes acoustic radiation force to generate small, localized displacements within the vitreous-mimicking gel. These localized displacements are quantified to yield maximum displacement, relative elasticity, and relative viscosity images. We present KAVE images of a set of four phantoms with different gel concentrations. Although B-mode and relative viscosity images exhibit no significant differences, maximum displacement, and relative elasticity images clearly differentiate gels of different concentrations. Maximum displacements ranged between 30 and 5 microns, depending on acrylamide concentration. The results presented in this paper show that soft gel phantoms can be produced in a range of elasticities not previously reported, and that these phantoms are useful for testing ultrasound instruments designed for evaluation of the vitreous gel. Furthermore, the use of acrylamide-based gels may also offer a valuable and attractive alternative for many other ultrasound applications.
Acrylic Resins↗
Retinal toxicity of intravitreal triamcinolone acetonide: a morphological study.
PURPOSE: To evaluate the morphologic effects of intravitreal triamcinolone acetonide (TA) on rabbit retina. METHODS: Intravitreal injections of 0.5 mg, 1 mg, 4 mg, 8 mg, and 20 mg of TA (Kenalog-40; Bristol-Myers Squibb, Princeton, NJ) in 0.1 mL were given to pigmented rabbits. For control, 0.1 mL of TA vehicle and saline were injected. Animals were killed on day 14, and retinas were analyzed by light as well as electron microscopy. RESULTS: No ophthalmoscopic change was found. Eyes injected with 0.5 mg and 1 mg of TA did not have morphologic abnormality. Eyes injected with 4 mg, 8 mg, and 20 mg showed destruction of photoreceptor outer segments and migration of macrophage-like cells in the subretinal space. Eyes injected with 20 mg showed more extensive damage and increased pigment granules in the retinal pigment epithelium cells with large oil droplets in the cytoplasm. Electron microscopy also showed loss of photoreceptor/retinal pigment epithelium interdigitations. Eyes injected with vehicle or saline did not show morphologic changes. CONCLUSION: Single intravitreal injection of 0.5 mg or 1 mg of TA did not produce morphologic retinal changes in pigmented rabbits. However, injections of 4 mg, 8 mg, and 20 mg of TA produced outer retina toxic effects. These findings suggest that long-term retinal toxicity studies should be carried out, using single and repeated injections before this therapy becomes more widely used.
Animals↗