2008 — 2010 |
Huang, David |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Guiding the Treatment of Anterior Eye Diseases With Optical Coherence Tomography @ Oregon Health &Science University
DESCRIPTION (provided by applicant): The long-term goal of this project is to utilize newly available very high-speed optical coherence tomography (OCT) technology to guide surgical treatments of anterior eye diseases. Measuring aberrations in the optical surfaces of the cornea requires great precision. OCT is well known for its exquisite spatial resolution, but until recently it has not had sufficient speed to overcome the inherent biological motion of the eye and capture the shape of the cornea. The development of Fourier-domain (FD) OCT technology has made the requisite speed possible. The specific aims are: (1) To develop a very high-speed anterior segment OCT instrument. An FD-OCT system capable of 26,000 axial scans/second and 5-5m resolution has been tested. Preliminary data show that it is able to map corneal thickness with a precision of 1-5m root-mean-square and measure corneal power with a precision of 0.2 diopters. Motion correction algorithms will be developed to further improve the precision. (2) To develop OCT-guided corneal laser surgery for the treatment of irregular and opacified corneas. Although wavefront sensing and Placido-ring topography have been used to guide laser corneal surgeries, they are often unable to make valid measurements of irregular corneas. Our preliminary results showed that OCT can reliably make measurements in these diseased corneas that are most in need of surgical remedy. Corneal thickness or topography maps obtained by the OCT system will be used to program the depth of femtosecond laser corneal dissection and excimer laser ablation. OCT-guided femtosecond laser lamellar keratoplasty and excimer laser phototherapeutic keratectomy (PTK) will be tested in rabbit studies. Patients with corneal scar, ectasia, dystrophy, or irregular astigmatism following corneal surgery will be scanned, and laser surgery will be simulated by computer to evaluate the visual outcome. The simulation will take into account measurement variability, laser delivery error, healing effects, and visual optics. These tests will prepare for future human trials. (3) To develop an OCT-based intraocular lens (IOL) power formula. IOL power selection is difficult in patients who have had previous laser vision correction, often resulting in significant near- or far-sightedness after the cataract surgery. Laser ablation alters the natural relationship between the front and back corneal surfaces, causing error in conventional keratometry and IOL calculation. This increasingly common problem could be solved by measuring both anterior and posterior corneal powers with OCT. The OCT-based IOL formula will be tested in a clinical trial. The aim of this project is to develop methods for imaging the cornea with a very high-speed and high-resolution optical coherence tomography (OCT) system that will precisely measure corneal thickness and shape and use this information to guide eye surgery. Patients with irregularly shaped or scarred corneas could have their vision restored by reshaping the corneas with a procedure that combines the precision of OCT and lasers instead of traditional corneal transplantation, which is associated with slow visual recovery and risks of transplant rejection. Cataract surgery in patients with previous laser vision correction often leads to significant near- or far-sightedness, a problem that could be resolved by using a more accurate intraocular lens power selection formula based on the measurement of corneal refractive power with OCT.
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2011 — 2015 |
Huang, David |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Guiding the Treatment of Anterior Eye Disease With Optical Coherence Tomography @ Oregon Health &Science University
DESCRIPTION (provided by applicant): Optical coherence tomography (OCT) is a cross-sectional and 3-dimensional (3-D) imaging technology with very fine spatial resolution (5 5m). This project develops the methods and software needed for high-precision OCT measurements of the eye to guide implant, laser, and transplant surgeries in the front part of the eye. In the proposed continuation of the project, a new generation of OCT that has very high speed (about 10 times faster than before, taking an image in as little as 2/1000 of a second) and extended range will enable new types of measurements to be done accurately. The Specific Aims are as follows: (1) To develop ultrahigh-speed OCT hardware and software for measuring optical surfaces of the anterior eye. Intrinsic eye movements effectively limit measurement of corneal shape by commercial OCT. This will be overcome by several approaches, including ultrahigh-speed OCT at 500 kHz, dual-beam OCT to simultaneously capture the shape of both the cornea and lens, simultaneous capture of Placido-ring videokeratography, and motion correction software. The goal is to provide reliable measurements on front and back surfaces of both the cornea and crystalline lens. (2) To develop an OCT-based intraocular lens power formula. Currently, surgeons lack an accurate way to calculate precise intraocular lens (IOL) power for cataract patients who previously had laser vision correction. These patients may be left near- or far-sighted after cataract surgery. An OCT-based IOL formula, using measurements of both anterior and posterior corneal powers, can give surgeons more precise information that will significantly improve visual outcomes. The OCT-based IOL formula will be tested in a clinical trial. (3) To develop OCT-guided excimer laser surface ablation. The excimer laser can remove cloudy layers from the front of the cornea and correct distorted shape due to keratoconus or transplant surgery. We have developed 3-D OCT-based planning to optimally remove cloudiness due to corneal scars and stromal dystrophies. This method will be tested in a larger clinical trial. We will improve the method by adding 3-D OCT measurement of corneal shape (topography) to plan the correction of any shape distortion. (4) To develop OCT-guided laser-assisted anterior and posterior lamellar keratoplasty. Most corneal diseases involve only the inner or outer layer of the cornea. Thus a partial thickness transplant can treat these diseases while avoiding the complications of full-thickness transplantations (rejection, irregular wound shape, etc). However, manual dissection of corneal layers is technically difficult and vision after surgery is limited by the rough interfaces. We have developed OCT methods to guide the shaping and smoothing of donor and host corneas with a combination of excimer laser to create smooth interfaces and femtosecond laser to create tongue-in-groove edge fits. Pilot clinical trials of these techniques are proposed. The goal is to develop surgeries that reliably improve the vision in patients with keratoconus, corneal dystrophies, and deep scars. PUBLIC HEALTH RELEVANCE: Optical coherence tomography (OCT) performs noncontact mapping of corneal shape and thickness with higher resolution and speed than conventional instruments. This project will develop the next generation of ultrahigh-speed OCT instruments and use them to accurately calculate intraocular lens power and improve outcomes of cataract surgery in eyes with previous laser vision correction. These instruments will also provide data to improve the precision, safety, and effectiveness in laser correction of cloudy or irregular corneas and laser-assisted corneal transplantation.
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2013 — 2021 |
Huang, David |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Functional and Structural Optical Coherence Tomography For Glaucoma @ Oregon Health & Science University
DESCRIPTION (provided by applicant): Glaucoma is a leading cause of blindness. Early diagnosis and close monitoring of glaucoma are important because the onset is insidious and the damage is irreversible. Advanced imaging modalities such as optical coherence tomography (OCT) have been used in the past 2 decades to improve the objective evaluation of glaucoma. OCT has higher axial spatial resolution than other posterior eye imaging modalities, and it has relatively good diagnostic accuracy and reproducibility in the measurement of neural structures damaged by glaucoma. However, the measurement of structure alone, with any imaging modality, has limited sensitivity for detecting early glaucoma and only moderate correlation with visual field (VF) loss. Using high-speed OCT systems, we have developed new methods to image and measure optic nerve head (ONH) and retinal blood flow. Preliminary results showed that VF loss was more highly correlated with retinal blood flow as measured by OCT than any neural structure measured by OCT or other imaging modality. Accordingly, the goal of the proposed project is to improve the diagnostic and prognostic evaluation of glaucoma by further developing novel functional OCT measurements using ultrahigh-speed (70-100 kHz) OCT technology. The specific aims are: 1. Improve Doppler OCT measurement of retinal blood flow. Multi-circular scans of peripapillary retinal arteries and veins measure total retinal blood flow i 2 seconds. The use of faster OCT systems will allow automated measurement with improved reproducibility. 2. Develop quantitative OCT angiography of the ONH. Three dimensional (3D) OCT angiography has been made practical (3x3 mm scan in 3 seconds) by a novel split-spectrum amplitude-decorrelation algorithm. Preliminary results showed dramatic loss of ONH microcirculation in early glaucoma. Algorithmic improvement in angiography, segmentation, quantification, and automation are planned. 3. Measure nerve structure from the ONH to retinal ganglion cells. By registering several volumetric scans, we have demonstrated complete 3D characterization of the retinal fiber pathway from the ONH to the macula. Fully automated quantification of these structures will be developed. 4. Evaluate advanced OCT technologies in clinical studies. The utility of functional and structural OCT in glaucoma will be evaluated in a longitudinal observational study of 150 glaucoma and healthy subjects. The effect of IOP-lowering surgery on blood flow will be studied in 40 subjects. Retinal blood flow, ONH circulation, optic disc rim volume, peripapillary nerve fiber layer volume, and macular ganglion cell complex volume are all pieces of the same glaucoma puzzle. This project will develop novel imaging methods that allow us to look at the whole picture using one tool - ultrahigh-speed OCT.
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2018 — 2021 |
Huang, David |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Applications of Ultrahigh-Speed Long-Range Wide-Field Oct in Anterior Eye Diseases @ Oregon Health & Science University
PROJECT SUMMARY Optical coherence tomography (OCT) is uniquely able to achieve micron depth resolution while imaging a large 3-dimensional (3D) volume. This enables 3D imaging and precise measurements in the anterior segment of the eye, including the cornea, conjunctiva, sclera, anterior chamber, iris, and crystalline lens. Anterior segment OCT is already widely used in ophthalmology. But a number of high-impact applications were held back by limited speed, range, penetration, and disease-specific algorithms. Therefore the specific aims are to: (1) Develop ultrahigh performance OCT for anterior eye. A novel vertical-cavity surface-emitting laser (VCSEL) will be used to develop an OCT prototype with ultrahigh-speed, wide-field, long-range, and high- penetration. The high speed and penetration will allow blood vessel imaging (angiography) in iris tumors. The wide field and long range will enable accurate whole anterior-segment biometry from the apex of the cornea to the posterior surface of the crystalline lens, which will take intraocular lens (IOL) formulas and custom scleral contact lens design to a new level of accuracy. (2) Develop OCT angiography (OCTA) of iris tumors. Distinguishing between benign and malignant tumors, including deadly melanomas, is crucial for planning treatments that minimize damage to sensitive eye tissues and reduce the risk of metastasis. Increased vascularity marks malignant transformation in tumors. The proposed ultrahigh performance OCT prototype will enable OCTA in tumors with sufficient penetration to characterize both tumor vasculature and volume. Novel software algorithms will be used to suppress motion, projection, and shadow artifacts, segment tissue boundaries, and calculate quantitative vascular density and tortuosity measurements. The technology could be useful in the evaluation of tumor angiogenesis elsewhere. (3) Improve OCT-based IOL power formula. Previously we developed an OCT-based IOL formula that improved cataract surgery refractive outcome in post-myopic LASIK eyes. We now propose to further improve the OCT-based IOL formula so that it could improve refractive outcome in all cataract surgeries, and be used to select toric as well non-toric IOL. The long-range OCT can accurately measure the crystalline lens equatorial position to improve the prediction of IOL position, which is a crucial variable that currently limits the accuracy of IOL formulas. High-speed OCT together with ray-tracing will enable more accurate net corneal power and astigmatism measurements, especially in post-radial keratotomy and post-hyperopic LASIK eyes. (4) Improve scleral lens fitting with wide-field OCT. Scleral contact lens vaults over the cornea and offers an important nonsurgical option to restore comfort and vision to patients with irregular corneal shape or ocular surface inflammation. The primary limitation of scleral lens is the difficult trial-and-error fitting process. We will use wide-field OCT corneoscleral topography to improve the selection of the initial trial lens and design advanced radially asymmetric scleral lenses that are highly customized to the subject ocular surface.
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