Visualization of surgical maneuvers using intraoperative real-time volumetric optical coherence tomography.

Ophthalmic microsurgery is traditionally performed using stereomicroscopes and requires visualization and manipulation of sub-millimeter tissue structures with limited contrast. Optical coherence tomography (OCT) is a non-invasive imaging modality that can provide high-resolution, depth-resolved cross sections, and has become a valuable tool in clinical practice in ophthalmology. While there has been substantial progress in both research and commercialization efforts to bring OCT imaging into live surgery, its use is still somewhat limited due to factors such as low imaging speed, limited scan configurations, and suboptimal data visualization. In this paper we describe, to the best of our knowledge, the translation of the fastest swept-source intraoperative OCT system with real-time volumetric imaging with stereoscopic data visualization provided via a heads-up display into the operating room. Results from a sampling of human anterior segment and retinal surgeries chosen from 93 human surgeries using the system are shown and the benefits that this mode of intrasurgical OCT imaging provides are discussed.

Quantitative measurements of intraocular structures and microinjection bleb volumes using intraoperative optical coherence tomography.

Intraoperative optical coherence tomography (OCT) systems provide high-resolution, real-time visualization and/or guidance of microsurgical procedures. While the use of intraoperative OCT in ophthalmology has significantly improved qualitative visualization of surgical procedures inside the eye, new surgical techniques to deliver therapeutics have highlighted the lack of quantitative information available with current-generation intraoperative systems. Indirect viewing systems used for retinal surgeries introduce distortions into the resulting OCT images, making it particularly challenging to make calibrated quantitative measurements. Using an intraoperative OCT system based in part on the Leica Enfocus surgical microscope interface, we have devised novel measurement procedures, which allowed us to build optical and mathematical models to perform validation of quantitative measurements of intraocular structures for intraoperative OCT. These procedures optimize a complete optical model of the sample arm including the OCT scanner, viewing attachments, and the patient's eye, thus obtaining the voxel pitch throughout an OCT volume and performing quantitative measurements of the dimensions of imaged objects within the operative field. We performed initial validation by measuring objects of known size in a controlled eye phantom as well as ex vivo porcine eyes. The technique was then extended to measure other objects and structures in ex vivo porcine eyes and in vivo human eyes.

Vitamin D deficiency in neovascular versus nonneovascular age-related macular degeneration.

PURPOSE: To compare 25-hydroxyvitamin D (25OHD) levels in patients with neovascular age-related macular degeneration (NVAMD) with patients with nonneovascular age-related macular degeneration and control patients. METHODS: Medical records of all patients diagnosed with age-related macular degeneration and tested for serum 25OHD level at a single medical center were reviewed. Control patients were selected from patients diagnosed with pseudophakia but without age-related macular degeneration. The lowest 25OHD level available for each patient was recorded. RESULTS: Two hundred sixteen patients with nonneovascular age-related macular degeneration, 146 with NVAMD, and 100 non-age-related macular degeneration control patients were included. The levels of 25OHD (mean ± SD) were significantly lower in NVAMD patients (26.1 ± 14.4 ng/mL) versus nonneovascular age-related macular degeneration (31.5 ± 18.2 ng/mL, P = 0.003) and control (29.4 ± 10.1 ng/mL, P = 0.049) patients. The prevalence of vitamin D insufficiency (<30 ng/mL 25OHD), deficiency (<20 ng/mL), and severe deficiency (<10 ng/mL) were highest in the NVAMD group. The highest quintile of 25OHD was associated with a 0.35 (95% confidence interval, 0.18-0.68) odds ratio for NVAMD. CONCLUSION: This is the largest study to compare 25OHD levels in patients with the different clinical forms of age-related macular degeneration. Mean 25OHD levels were lower and vitamin D deficiency was more prevalent in NVAMD patients. These associations suggest that further research is necessary regarding vitamin D deficiency as a potentially modifiable risk factor for the development of NVAMD.

Ultra high-resolution anterior segment optical coherence tomography in the evaluation of anterior corneal dystrophies and degenerations.

PURPOSE: To evaluate the clinical usefulness of a spectral-domain ultra high-resolution anterior segment optical coherence tomography (UHR OCT) in examination, diagnosis, and management of various anterior corneal dystrophies and degenerations. DESIGN: Noncomparative case series. PARTICIPANTS: Fifty-nine eyes of 38 consecutive patients were enrolled in the study and included 28 eyes of 14 patients with anterior corneal dystrophies, 21 eyes of 19 patients with anterior corneal degenerations or neoplasia, and 10 eyes of 5 patients with normal corneas. METHODS: Subjects were imaged using a novel custom-built UHR OCT. Images were used to evaluate and describe the characteristics of anterior corneal dystrophies and degenerations. Nineteen patients underwent surgical management, and those histopathologic specimens were analyzed and correlated with the UHR OCT images. MAIN OUTCOME MEASURES: Comparison of clinical findings, UHR OCT images, and corresponding histopathologic specimens. RESULTS: The UHR OCT provided clear delineation of corneal anatomic features and pathologic corneal deposits in most cases. The characteristics and depth of these deposits are illustrated and can be localized to specific layers of the cornea. When available, there was significant correlation between UHR OCT images and histopathologic features, providing a noninvasive confirmation of the clinical diagnosis. CONCLUSIONS: Ultra high-resolution OCT is an innovative technique to perform in vivo optical biopsies and a promising research and clinical tool for the evaluation of corneal pathologic features in a noninvasive manner. The future use of this novel technology will evolve and increasingly is becoming a vital tool in the clinical and surgical management of corneal diseases.