Showing papers by "Mark S. Humayun published in 2009"

Artificial vision: needs, functioning, and testing of a retinal electronic prosthesis.

Abstract: Hundreds of thousands around the world have poor vision or no vision at all due to inherited retinal degenerations (RDs) like retinitis pigmentosa (RP) Similarly, millions suffer from vision loss due to age-related macular degeneration (AMD) In both of these allied diseases, the primary target for pathology is the retinal photoreceptor cells that dysfunction and die Secondary neurons though are relatively spared To replace photoreceptor cell function, an electronic prosthetic device can be used such that retinal secondary neurons receive a signal that simulates an external visual image The composite device has a miniature video camera mounted on the patient's eyeglasses, which captures images and passes them to a microprocessor that converts the data to an electronic signal This signal, in turn, is transmitted to an array of electrodes placed on the retinal surface, which transmits the patterned signal to the remaining viable secondary neurons These neurons (ganglion, bipolar cells, etc) begin processing the signal and pass it down the optic nerve to the brain for final integration into a visual image Many groups in different countries have different versions of the device, including brain implants and retinal implants, the latter having epiretinal or subretinal placement The device furthest along in development is an epiretinal implant sponsored by Second Sight Medical Products (SSMP) Their first-generation device had 16 electrodes with human testing in a Phase 1 clinical trial beginning in 2002 The second-generation device has 60+ electrodes and is currently in Phase 2/3 clinical trial Increased numbers of electrodes are planned for future versions of the device Testing of the device's efficacy is a challenge since patients admitted into the trial have little or no vision Thus, methods must be developed that accurately and reproducibly record small improvements in visual function after implantation Standard tests such as visual acuity, visual field, electroretinography, or even contrast sensitivity may not adequately capture some aspects of improvement that relate to a better quality of life (QOL) Because of this, some tests are now relying more on "real-world functional capacity" that better assesses possible improvement in aspects of everyday living Thus, a new battery of tests have been suggested that include (1) standard psychophysical testing, (2) performance in tasks that are used in real-life situations such as object discrimination, mobility, etc, and (3) well-crafted questionnaires that assess the patient's own feelings as to the usefulness of the device In the Phase 1 trial of the SSMP 16-electrode device, six subjects with severe RP were implanted with ongoing, continuing testing since then First, it was evident that even limited sight restoration is a slow, learning process that takes months for improvement to become evident However, light perception was restored in all six patients Moreover, all subjects ultimately saw discrete phosphenes and could perform simple visual spatial and motion tasks As mentioned above, a Phase 2/3 trial is now ongoing with a 60+ device A 250+ device is on the drawing board, and one with over 1000 electrodes is being planned Each has the possibility of significantly improving a patient's vision and QOL, being smaller and safer in design and lasting for the lifetime of the patient From theoretical modeling, it is estimated that a device with approximately 1000 electrodes could give good functional vision, ie, face recognition and reading ability This could be a reality within 5-10 years from now In summary, no treatments are currently available for severely affected patients with RP and dry AMD An electrical prosthetic device appears to offer hope in replacing the function of degenerating or dead photoreceptor neurons Devices with new, sophisticated designs and increasing numbers of electrodes could allow for long-term restoration of functional sight in patients with improvement in object recognition, mobility, independent living, and general QOL

Feasibility Study of a Retinal Prosthesis : Spatial Vision With a 16-Electrode Implant

Abstract: Objective To demonstrate that an epiretinal prosthesis can produce patterned visual perception in patients blinded by photoreceptor degeneration who have no other treatment options. Methods A totally blind subject with retinitis pigmentosa had a 16-electrode epiretinal prosthesis implanted. The implant is controlled wirelessly by an external computer or a head-mounted video camera. Spatial vision was assessed by measuring the subject's response to direct stimulation of patterns and by comparing the ability of the subject to identify the orientation of gratings with the system on and off. Results In response to stimulation of 2 orthogonal rows of electrodes, the subject drew 2 lines with a mean (SEM) angle of 87.4° (1.8°) between them. With the system on, the subject identified the orientation of the grating target up to a spatial resolution that matches the spacing between the adjacent electrodes. In contrast, with the system off, the subject could not detect or identify the target's orientation. Conclusion Synchronized stimulation of different retinal locations with an epiretinal prosthesis implanted long-term can produce spatial vision with an acuity level determined by the distance between the electrodes. Trial Registration clinicaltrials.gov Identifier:NCT00279500

A passive MEMS drug delivery pump for treatment of ocular diseases.

Abstract: An implantable manually-actuated drug delivery device, consisting of a refillable drug reservoir, flexible cannula, check valve, and suture tabs, was investigated as a new approach for delivering pharmaceuticals to treat chronic ocular diseases. Devices are fabricated by molding and bonding three structured layers of polydimethylsiloxane. A 30 gauge non-coring needle was used to refill the reservoir; this size maximized the number of repeated refills while minimizing damage to the reservoir. The check valve cracking pressure was 76 +/- 8.5 mmHg (mean +/- SE, n = 4); the valve sustained > 2000 mmHg of reverse pressure without leakage. Constant delivery at 1.57 +/- 0.2 microL/sec and 0.61 +/- 0.2 microL/sec (mean +/- SE, n = 4) under 500 mmHg and 250 mmHg of applied pressure, respectively, was obtained in benchtop experiments. The valve closing time constant was 10.2 s for 500 mmHg and 14.2 s for 250 mmHg. Assembled devices were successfully demonstrated in benchtop, ex vivo, and in vivo experiments.

Drug-delivery pumps and methods of manufacture

Abstract: Embodiments of method of manufacturing an implantable pump, including providing an upper layer comprising a dome structure for housing a drug chamber and a cannula in fluid communication with the drug chamber, providing a middle deflection layer adjacent the drug chamber, providing a bottom layer comprising electrolysis electrodes, and bonding the upper layer, middle deflection layer, and bottom layer to form the pump.

Preliminary 6 month results from the argus tm ii epiretinal prosthesis feasibility study

Abstract: The Argus™ II 60 channel epiretinal prosthesis has been developed in order to provide partial restoration of vision to subjects blinded from outer retinal degenerative disease. To date the device has been implanted in 21 subjects as part of a feasibility study. In 6 month post-implantation door finding and line tracking orientation and mobility testing, subjects have shown improvements of 86% and 73%, respectively, for system on vs. system off. In high-contrast Square Localization tests using a touch screen monitor 87% of tested subjects performed significantly better with the system on compared with off. These preliminary results show that the Argus II system provides some functional vision to blind subjects.

Predicting Visual Sensitivity in Retinal Prosthesis Patients

Abstract: Retinitis pigmentosa and age-related macular degeneration are frequent causes of blindness in the developed world.1–3 Both diseases begin with the degeneration of photoreceptors, though in later stages the number of bipolar, amacrine, and ganglion cells are significantly decreased4–6 and their spatial organization and circuitry are significantly disorganized.7 More than 150 different gene mutations result in photoreceptor diseases for which there are currently no Food and Drug Administration (FDA)–approved treatments,8 motivating the development of technologies to restore visual function that do not require targeting each genetic defect independently. One approach is to target bipolar and ganglion cells with engineered photo gates9–11 and light-sensitive proteins.12–17 However, the successful development of such treatments will require several advances, such as in vivo delivery and activation methodologies that are safe for human use. Another approach is to develop implantable microelectronic visual prostheses that, analogous to cochlear implants, would directly stimulate remaining retinal neurons with electrical current. The ultimate goal of most implants is to generate useful vision in blind patients by transforming visual information into a spatial and temporal sequence of electrical pulses. To date, several groups have succeeded in generating visual percepts in patients with implanted acute, semiacute, and long-term retinal prostheses (Zrenner E, et al. IOVS 2006;47: ARVO E-Abstract 1538).18–21 However, to create perceptually meaningful images, it is necessary to predictably generate a range of brightness levels over both space and time. Although the literature examining the perceptual consequences of electrical stimulation has a long history,19,21,22–34 there is still relatively little data in humans systematically quantifying the effects of retinal electrical stimulation as a function of stimulation current levels and the temporal stimulation pattern. In the current study, at the single electrode level, retinal electrical stimulation resulted in predictable visual qualia that can be described with a relatively simple linear–nonlinear model that predicts the relationship between electrical stimulation and sensitivity for a wide variety of temporally varying stimulation patterns. This model not only can be used to determine the “optimal” pattern of stimulation, given a variety of engineering constraints (such as stimulating at safe levels of charge density and minimizing overall charge), but may also provide some insight into the neural pathways that underlie the perceptual effects of electrical stimulation.

Brightness as a Function of Current Amplitude in Human Retinal Electrical Stimulation

Abstract: Retinitis pigmentosa and age-related macular degeneration are two of the more frequent causes of blindness in the developed world.1-3 Both diseases are progressive and begin with the degeneration of photoreceptors. In later stages of these diseases, bipolar, amacrine, and ganglion cells are still present, though their numbers are significantly decreased4-6 and their spatial organization and circuitry are significantly disorganized.7,8 There are more than 180 different gene mutations that result in photoreceptor diseases for which there is currently no cure or treatment.1 Ideally, it would be possible to develop a treatment for these conditions that would not require targeting each genetic defect independently. Several groups are developing implantable microelectronic visual prostheses that produce percepts by electrically stimulating remaining retinal neurons. To date, several groups have succeeded in generating visual percepts via electrical stimulation with implanted acute, semi-acute, and long-term retinal prostheses in human patients.9-14 The ultimate goal of these projects is to generate useful vision in blind patients by transforming a video stream into a spatial and temporal sequence of electrical pulses that represents meaningful visual information. However, creating a perceptually meaningful pattern of stimulation is dependent on a detailed understanding of the perceived intensity of any given stimulation pattern; to date, the literature examining the perceptual consequences of electrical stimulation remains relatively sparse.10-12,15-20 A visual prosthesis should produce regions of constant brightness across a range of brightness levels, and ideally these brightness levels should be consistent with the apparent brightness of objects as they appear to those with normal vision. Our goal was to examine how apparent brightness changes as a function of stimulation intensity in two blind human subjects chronically implanted with a prototype epiretinal prosthesis consisting of a 4 × 4 array of 16 stimulating electrodes. In experiment 1, subjects rated the apparent brightness of pulse stimuli on individual electrodes using a reference pulse of fixed amplitude. We found that apparent brightness as a function of current amplitude can be described using a simple power function. In experiment 2, a brightness-matching technique was used to compare apparent brightness across pairs of electrodes. We found that the apparent brightness of a given electrode can be related to other electrodes on the array using the same simple power function model. The results from these two experiments suggest that a relatively simple model for scaling current across electrodes may, to a first approximation, be capable of producing equivalently bright phosphenes across an entire array.

Implantable drug-delivery devices, and apparatus and methods for filling the devices

Abstract: In various embodiments, a tool is employed in filling a drug-delivery device. The tool may include, for example, a needle that is admitted through a fill port of the drug-delivery device.

Implantable pumps and cannulas therefor

Abstract: In various embodiments, an implantable pump includes a cannula. The pump (e.g., the cannula thereof) may include, for example, flow sensors, pressure sensors, filters, and/or other components.

Implantable drug-delivery devices, and apparatus and methods for refilling the devices

Abstract: In various embodiments, a refill needle (120) is employed in refilling drug-delivery devices. The refill needle (120) encompasses a hollow shaft (212) which may extend from a proximal end (200) of the needle to a proximal end (216) of a terminating tip (208). The refill needle includes at least one fluid exit port (220) positioned along the shaft (212), e.g. near the tip (208) and a means (224) suitable for limiting an extent of entry of the refill needle into the entry port (116) of a drug -delivery device (100).

Toward a wide-field retinal prosthesis.

Abstract: The purpose of this paper is to present a wide field electrode array that may increase the field of vision in patients implanted with a retinal prosthesis. Mobility is often impaired in patients with low vision, particularly in those with peripheral visual loss. Studies on low vision patients as well as simulation studies on normally sighted individuals have indicated a strong correlation between the visual field and mobility. In addition, it has been shown that an increased visual field is associated with a significant improvement in visual acuity and object discrimination. Current electrode arrays implanted in animals or human vary in size; however, the retinal area covered by the electrodes has a maximum projected visual field of about 10 degrees. We have designed wide field electrode arrays that could potentially provide a visual field of 34 degrees, which may significantly improve the mobility. Tests performed on a mechanical eye model showed that it was possible to fix 10 mm wide flexible polyimide dummy electrode arrays onto the retina using a single retinal tack. They also showed that the arrays could conform to the inner curvature of the eye. Surgeries on an enucleated porcine eye model demonstrated feasibility of implantation of 10 mm wide arrays through a 5 mm eye wall incision.

Specific Absorption Rate and Current Densities in the Human Eye and Head Induced by the Telemetry Link of an Epiretinal Prosthesis

Abstract: The fields induced in the human head by the wireless telemetry used for Second Sight Medical Product, Inc.'s epiretinal prosthesis system are characterized for compliance testing with international safety standards using a three-dimensional (3-D) finite-difference time-domain (FDTD) code in D-H formulation. The specific system under consideration utilizes an inductive link with a primary coil mounted on the subject's eyeglasses and a secondary coil that is strapped on the eye, over the sclera. The specific absorption rate (SAR) and the current density have been obtained computationally for different relative positions of the primary and secondary coils to account for the relative misalignment of the two due to the movement of the eye with the implant. For a peak normalized current of 0.62 A in the primary coil at 10 MHz, the highest peak 1-g SAR was found to be 0.45 W/Kg, and the maximum root mean square (rms) current density averaged over a 1-cm2 area was found to be 16.05 A/m2, both of which are within the limits imposed by IEEE and ICNIRP safety standards. Simulations between 2 and 20 MHz indicated that the induced electric field values scale well with frequency, thus providing guidelines for the determination of the final frequency and input power requirements of operation for the telemetry system to meet safety standards.

Measurements of attenuation coefficient for evaluating the hardness of a cataract lens by a high-frequency ultrasonic needle transducer

Abstract: A cataract is a clouding of the lens in the eye that affects vision. Phacoemulsification is the mostly common surgical method for treating cataracts, and determining that the optimal phacoemulsification energy is dependent on measuring the hardness of the lens. This study explored the use of an ultrasound needle transducer for invasive measurements of ultrasound attenuation coefficient to evaluate the hardness of the cataract lens. A 47 MHz high-frequency needle transducer with a diameter of 0.9 mm was fabricated by a polarized PMN-33%PT single crystal in the present study. The attenuation coefficients at different stages of an artificial porcine cataract lens were measured using the spectral shift approach. The hardness of the cataract lens was also evaluated by mechanical measurement of its elastic properties. The results demonstrated that the ultrasonic attenuation coefficient was increased from 0.048 ? 0.02 to 0.520 ? 0.06 dB mm?1 MHz?1 corresponding to an increase in Young's modulus from 6 ? 0.4 to 96 ? 6.2 kPa as the cataract further developed. In order to evaluate the feasibility of combining needle transducer and phacoemulsification probe for real-time measurement during cataract surgery, the needle transducer was mounted on the phacoemulsification probe for a vibration test. The results indicated that there was no apparent damage to the tip of the needle transducer and the pulse?echo test showed that a good performance in sensitivity was maintained after the vibration test.

Finite element modeling of retinal prosthesis mechanics

Abstract: Epiretinal prostheses used to treat degenerative retina diseases apply stimulus via an electrode array fixed to the ganglion cell side of the retina Mechanical pressure applied by these arrays to the retina, both during initial insertion and throughout chronic use, could cause sufficient retinal damage to reduce the device's effectiveness In order to understand and minimize potential mechanical damage, we have used finite element analysis to model mechanical interactions between an electrode array and the retina in both acute and chronic loading configurations Modeling indicates that an acute tacking force distributes stress primarily underneath the tack site and heel edge of the array, while more moderate chronic stresses are distributed more evenly underneath the array Retinal damage in a canine model chronically implanted with a similar array occurred in correlating locations, and model predictions correlate well with benchtop eyewall compression tests This model provides retinal prosthesis researchers with a tool to optimize the mechanical electrode array design, but the techniques used here represent a unique effort to combine a modifiable device and soft biological tissues in the same model and those techniques could be extended to other devices that come into mechanical contact with soft neural tissues

Implantable Flexible-Coiled Wireless Intraocular Pressure Sensor

Abstract: This work presents an implantable wireless passive pressure sensor for long-range continuous intraocular pressure (IOP) monitoring of glaucoma patients. The sensor is microfabricated with use of parylene C (poly-chloro-p-xylylene) to create a flexible coil substrate that can be folded during implantation for suture-less minimally invasive surgery, while stretched back without damage for enhanced inductive sensor-reader coil coupling and the corresponding sensing signal. Extensive device characterizations including on-bench testing and in vivo and ex vivo animal studies verify the device feasibility in both engineering (1 mmHg pressure sensing accuracy and 2 cm sensing distance) and surgical (robust fixation to the iris and long-term biocompatibility in the intraocular environment) aspects, all meeting specifications for future practical implementation of such IOP sensing technology.

Mini Drug Pump for Ophthalmic Use

Abstract: Purpose: To evaluate the feasibility of developing a novel mini drug pump for ophthalmic use. Methods: Using principles of microelectromechanical systems engineering, a mini drug pump was fabricated. The pumping mechanism is based on electrolysis, and the pump includes a drug refill port as well as a check valve to control drug delivery. Drug pumps were tested first on the benchtop and then after implantation in rabbits. For the latter, we implanted 4 elliptical (9.9 × 7.7 × 1.8 mm) non-electrically active pumps into 4 rabbits. The procedure is similar to implantation of a glaucoma seton. To determine the ability to refill and also the patency of the cannula, at intervals of 4 to 6 weeks after implantation, we accessed the drug reservoir with a transconjunctival needle and delivered approximately as low as 1 µL of trypan blue solution (0.06%) into the anterior chamber. Animals were followed up by slit-lamp examination, photography, and fluorescein angiography. Results: Benchtop testing showed 2.0 µL/min delivery when using 0.4 mW of power for electrolysis. One-way valves showed reliable opening pressures of 470 mm Hg. All implanted devices refilled at 4- to 6-week intervals for 4 to 6 months. No infection was seen. No devices extruded. No filtering bleb formed over the implant. Conclusions: A prototype ocular mini drug pump was built, implanted, and refilled. Such a platform needs more testing to determine the long-term biocompatibility of an electrically controlled implanted pump. Testing with various pharmacologic agents is needed to determine its ultimate potential for ophthalmic use.

A comparison of retinal prosthesis electrode array substrate materials

Abstract: Simulations of artificial vision suggest that 1000 electrodes may be required to restore vision to individuals with diseases of the outer retina. In order to achieve such an implant, new technology is needed, since the state-of-the-art implantable neural stimulator has at most 22 contacts with neural tissue. A critical component of this system is the multi-channel, stimulating electrode array. This array must meet very challenging, competing requirements for manufacturing, integration, surgical handling, and biocompatibility. Our lab has evaluated 3 polymers as retinal prosthesis substrates: polyimide, parylene, and silicone.

Minimally Invasive Parylene Dual-Valved Flow Drainage Shunt for Glaucoma Implant

Abstract: A parylene-enabled microvalved shunt implant for glaucoma drainage is presented in this paper. Enabled by the dual-checkvalve operation, this device can physically drain the extra intraocular fluid and regulate the intraocular pressure (IOP) within the normal range (15-20 mmHg). Improved surgical features, in addition to the functional/microfluidic components, such as parylene-tube carrier and anchors, are also incorporated in such device to realize minimally invasive suture-less implantation, suitable for practical in vivo use. With the optimized micromachining and post-fabrication process procedures, the developed implant is the first checkvalved glaucoma drainage device (GDD), which is passive, consumes no additional power, and functions without any circuit involved to pursue its medical application.

Ocular Imaging System

Abstract: An imaging system for examining the interior structure of the eye at high-resolution under ambient light without the need for chemical dilation of the pupil.

Subchoroidal retinal prosthesis

Abstract: Embodiments of the present disclosure are directed to utilization of one or more arrays that are placed under the choroid. In this approach, an array is placed under the choroid. To achieve this, a scleral incision can be made without cutting the underlying choroid or retina. The array can then be inserted into the space between the sclera and choroid and is pushed to the desired place. It is possible to make several of such scleral incisions in each quadrant of the eye to insert arrays of similar or different shapes into the subchoroidal space. Following insertion of the electrode array the scleral wound may be sutured around the cable to make the array and the eye more stable.

Guillotine performance: duty cycle analysis of vitrectomy systems.

Abstract: Purpose To evaluate the duty cycle of different vitrectomy cutters and classify their blade movement. Methods A precise weighing (0.01 g) high speed (2 samples/s) balance was used to study the 20-gauge and 25-gauge Bausch & Lomb Lightning-Millenium (St. Louis, MO), the 20-gauge (1500 cpm) and the 25-gauge Alcon Accurus (Fort Worth, TX), the 20-gauge Alcon Innovit, and the 23-gauge DORC (Netherlands) cutters. The weight of balanced saline solution (BSS) was recorded in real time using LabView software and then translated into a graph of volume removed versus time. Variable cut rates and vacuum pressures were analyzed in vitreous and BSS. A high-speed (400 frames/s) camera was used to record cutting for each condition. Results Three types of duty cycle were investigated: parabolic incomplete (pneumatic), sinusoid (electric), and trapezoid (double pneumatic). The parabolic incomplete and trapezoid had a decreased duty cycle at 1500 cuts per minute when it was compared to 600 cuts per minute. The sinusoid had no statistical difference between cut rates. Conclusions Systems showed different performances of duty cycle. This new classification will be useful for improved understanding of vitrectomy in these different systems.

Feasibility of rotational scan ultrasound imaging by an angled high frequency transducer for the posterior segment of the eye

Abstract: High frequency ultrasound over 40 MHz has been used to image the anterior segment of the eye, but it is not suitable for the posterior segment due to the frequency-dependent attenuation of ultrasound and thus the limitation of penetration depth. This paper proposes a novel scan method to image the posterior segment of the eye with an angled high frequency (beyond 40 MHz) ultrasound needle transducer. In this method, the needle transducer is inserted into the eye through a small incision hole (~1 mm in diameter) and rotated around the axial direction to form a cone-shaped imaging plane, allowing the spatial information of retinal vessels and diagnosis of their occlusion to be displayed. The feasibility of this novel technique was tested with images of a wire phantom, a polyimide tube, and an excised pig eye obtained by manually rotating a 40 MHz PMN-PT needle transducer with a beveled tip of 45deg. From the results, we believe that rotational scan imaging will help expand the minimally invasive applications of high frequency ultrasound to other areas due to the capability of increased closeness of an angled needle transducer to structures of interest buried in other tissues.

Biomimetic image processing for retinal prostheses: Peripheral saliency cues

Abstract: Retinal prosthesis recipients may still have degraded vision, such that additional information about their surroundings may help them perform certain tasks. We evaluate a system that provides cues that point towards important objects. Using a simulated vision grid of 6 × 10 pixels, subjects perform object location and mobility tasks with and without the help of cues. The velocity of head movement in degrees per second and the time taken by subjects to finish the tasks are recorded. Results show that a cueing system may help to reduce and organize the head movements of the subjects, whereas a time benefit exists in object location but not in mobility tasks.

Metabolic Prosthesis for Oxygenation of Ischemic Tissue

Abstract: This communication discloses new ideas and preliminary results on the development of a metabolic prosthesis for local oxygenation of ischemic tissue under physiologically neutral conditions. We report for the first time selective electrolysis of physiological saline by repetitively pulsed, charge-limited electrolysis for the production of oxygen and suppression of free chlorine. Using 800-mu A amplitude current pulses and < 200 mus pulse duration, we demonstrate prompt oxygen production and delayed chlorine production at the surface of a fused 0.85-mm diameter spherical platinum electrode. The data, interpreted in terms of the ionic structure of the electric double layer, suggest a strategy for in situ production of metabolic oxygen via a new class of ldquosmartrdquo prosthetic implants for ischemic disease such as diabetic retinopathy. We also present data indicating that collateral pH drift, if any, can be held constant using a feedback-controlled three-electrode electrolysis system that chooses an anode and cathode pair based on pH data provided by a local sensor.

Visual prosthesis for phosphene shape control

Abstract: The present invention is an improved method of stimulating visual neurons to create artificial vision. It has been found that varying current of visual stimulation can create varying percept brightness, varying percept size, and varying percept shape. By determining the attributes of predetermined current levels, and using those attributes to program a video processor, more accurate video preproduction can be obtained. The present invention also includes an electrode array having alternating large and small electrodes in rows at a 45 degree angle to horizontal in the visual field.

In situ measurements of attenuation coefficient for evaluating the hardness of cataract lens by a high frequency ultrasonic needle transducer

Abstract: A cataract is a clouding of the lens in the eye that affects vision. Phacoemulsification is the mostly common surgical method for treating cataracts, and determining the optimal phacoemulsification energy is dependent on measuring the hardness of the lens. This study explored the use of an ultrasound needle transducer for in situ minimally invasive measurements of ultrasound attenuation coefficient to evaluate the hardness of cataract lens. A 47 MHz high frequency needle transducer with a diameter of 0.9 mm was fabricated by a polarized PMN-33%PT single crystal in the present study. The attenuation coefficients at different stages of artificial porcine cataract lens were measured using the spectral shift approach. The hardness of the cataract lens was also evaluated by mechanical measurement of its elastic properties. The results demonstrated that the ultrasonic attenuation coefficient was increased from 0.048±0.02 to 0.520±0.06 dB/mm-MHz corresponding to an increase of Young's modulus from 6 to 96 kPa as the cataract further developed. In order to evaluate the feasibility of combining needle transducer and phacoemulsification probe for real time measurement during cataract surgery, the needle transducer was mounted on the phacoemulsification probe for vibration test. The results indicated that there was no apparent damage to the tip of needle transducer and the pulse-echo test showed a good performance in sensitivity was maintained after the vibration test.