Ramiro S. Maldonado

Optimizing Hand-held Spectral Domain Optical Coherence Tomography Imaging for Neonates, Infants, and Children

PURPOSE To describe age-related considerations and methods to improve hand-held spectral domain optical coherence tomography (HH-SD OCT) imaging of eyes of neonates, infants, and children. METHODS Based on calculated optical parameters for neonatal and infant eyes, individualized SD OCT scan parameters were developed for improved imaging in pediatric eyes. Forty-two subjects from 31 weeks postmenstrual age to 1.5 years were imaged with a portable HH-SD OCT system. Images were analyzed for quality, field of scan, magnification, and potential clinical utility. RESULTS The axial length of the premature infant eye increases rapidly in a linear pattern during the neonatal period and slows progressively with age. Refractive error shifts from mild myopia in neonates to mild hyperopia in infants. These factors affect magnification and field of view of optical diagnostic tools applied to the infant eye. When SD OCT parameters were corrected based on age-related optical parameters, SD OCT image quality improved in young infants. The field of scan and ease of operation also improved, and the optic nerve, fovea, and posterior pole were successfully imaged in 74% and 87% of individual eye imaging sessions in the intensive care nursery and clinic, respectively. No adverse events were reported. CONCLUSIONS SD OCT in young children and neonates should be customized for the unique optical parameters of the infant eye. This customization, not only improves image quality, but also allows control of the density of the optical sampling directed onto the retina.

Integration of a spectral domain optical coherence tomography system into a surgical microscope for intraoperative imaging.

PURPOSE To demonstrate an operating microscope-mounted spectral domain optical coherence tomography (MMOCT) system for human retinal and model surgery imaging. METHODS A prototype MMOCT system was developed to interface directly with an ophthalmic surgical microscope, to allow SDOCT imaging during surgical viewing. Nonoperative MMOCT imaging was performed in an Institutional Review Board-approved protocol in four healthy volunteers. The effect of surgical instrument materials on MMOCT imaging was evaluated while performing retinal surface, intraretinal, and subretinal maneuvers in cadaveric porcine eyes. The instruments included forceps, metallic and polyamide subretinal needles, and soft silicone-tipped instruments, with and without diamond dusting. RESULTS High-resolution images of the human retina were successfully obtained with the MMOCT system. The optical properties of surgical instruments affected the visualization of the instrument and the underlying retina. Metallic instruments (e.g., forceps and needles) showed high reflectivity with total shadowing below the instrument. Polyamide material had a moderate reflectivity with subtotal shadowing. Silicone instrumentation showed moderate reflectivity with minimal shadowing. Summed voxel projection MMOCT images provided clear visualization of the instruments, whereas the B-scans from the volume revealed details of the interactions between the tissues and the instrumentation (e.g., subretinal space cannulation, retinal elevation, or retinal holes). CONCLUSIONS High-quality retinal imaging is feasible with an MMOCT system. Intraoperative imaging with model eyes provides high-resolution depth information including visualization of the instrument and intraoperative tissue manipulation. This study demonstrates a key component of an interactive platform that could provide enhanced information for the vitreoretinal surgeon.

Dynamics of Human Foveal Development after Premature Birth

PURPOSE To determine the dynamic morphologic development of the human fovea in vivo using portable spectral domain-optical coherence tomography (SD-OCT). DESIGN Prospective, observational case series. PARTICIPANTS Thirty-one prematurely born neonates, 9 children, and 9 adults. METHODS Sixty-two neonates were enrolled in this study. After examination for retinopathy of prematurity (ROP), SD-OCT imaging was performed at the bedside in nonsedated infants aged 31 to 41 weeks postmenstrual age (PMA) (= gestational age in weeks + chronologic age) and at outpatient follow-up ophthalmic examinations. Thirty-one neonates met eligibility criteria. Nine children and nine adults without ocular pathology served as control groups. Semiautomatic retinal layer segmentation was performed. Central foveal thickness, foveal to parafoveal (FP) ratio (central foveal thickness divided by thickness 1000 μm from the foveal center), and 3-dimensional thickness maps were analyzed. MAIN OUTCOME MEASURES In vivo determination of foveal morphology, layer segmentation, analysis of subcellular changes, and spatiotemporal layer shifting. RESULTS In contrast with the adult fovea, several signs of immaturity were observed in the neonates: a shallow foveal pit, persistence of inner retinal layers (IRLs), and a thin photoreceptor layer (PRL) that was thinnest at the foveal center. Three-dimensional mapping showed displacement of retinal layers out of the foveal center as the fovea matured and the progressive formation of the inner/outer segment band in the opposite direction. The FP-IRL ratios decreased as IRL migrated before term and minimally after that, whereas FP-PRL ratios increased as PRL subcellular elements formed closer to term and into childhood. A surprising finding was the presence of cystoid macular edema in 58% of premature neonates that appeared to affect inner foveal maturation. CONCLUSIONS This study provides the first view into the development of living cellular layers of the human retina and of subcellular specialization at the fovea in premature infant eyes using portable SD-OCT. Our work establishes a framework of the timeline of human foveal development, allowing us to identify unexpected retinal abnormalities that may provide new keys to disease activity and a method for mapping foveal structures from infancy to adulthood that may be integral in future studies of vision and visual cortex development. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosure may be found after the references.

Insights into Advanced Retinopathy of Prematurity Using Handheld Spectral Domain Optical Coherence Tomography Imaging

PURPOSE To elucidate the subclinical anatomy of retinopathy of prematurity (ROP) using spectral domain optical coherence tomography (SD OCT). DESIGN Prospective, observational case series. PARTICIPANTS Three low-birth-weight, severely premature infants. METHODS Clinical examination was performed using a portable slit lamp and indirect ophthalmoscope. Imaging was performed by using a handheld SD OCT device and Retcam (Clarity Medical Systems, Pleasanton, CA) or video-indirect recording. Spectral domain optical coherence tomography imaging was conducted without sedation at the bedside in the neonatal intensive care unit on 1 patient. The other 2 patients had an examination under anesthesia with SD OCT imaging in the operating room. MAIN OUTCOME MEASURES In vivo determination of vitreoretinal morphology, anatomy, and pathology by clinical examination, imaging, and SD OCT. RESULTS Linear and volumetric imaging was achieved with the handheld system in infant eyes despite tunica vasculosa lentis and vitreous bands. Imaging was not possible in eyes with notable vitreous hemorrhage. Analysis of SD OCT images revealed preretinal structures (ranging from 409 to 2700 microm in width and 212 to 440 microm in height), retinoschisis, and retinal detachment in the posterior pole of patients with advanced ROP. Both the retinoschisis and the preretinal structures were not identified on conventional examination or imaging by expert pediatric ophthalmologists. The preretinal structures varied in location and size, and may represent preretinal fibrovascular proliferation. Some were found in close proximity to blood vessels, whereas others were near the optic nerve. CONCLUSIONS Handheld SD OCT imaging can be performed on the sedated or nonsedated neonate and provides valuable subclinical anatomic information. This novel imaging modality can reveal the location and extent of posterior ROP pathology not evident on standard examination. This could affect future clinical decision-making if studies validate a management strategy based on findings from this imaging technique.

Intraoperative use of handheld spectral domain optical coherence tomography imaging in macular surgery.

Purpose: To describe the intraoperative use of handheld spectral domain optical coherence tomography (SDOCT) imaging in macular surgery. Design: Prospective, observational case series. Methods: A handheld SDOCT device was used to obtain preincision optical coherence tomography imaging in patients undergoing vitrectomy for macular diseases. After removal of the internal limiting membrane or the epiretinal membrane, repeat intraoperative imaging was obtained. Spectral domain optical coherence tomography findings were characterized. Results: An efficient technique was established for obtaining intraoperative SDOCT imaging. A total of eight patients were included in the study. Four patients underwent surgery for macular hole, three patients for epiretinal membrane, and one for vitreomacular traction. Comparison of the preincision and intraoperative SDOCT images demonstrated distinct changes in retinal contour and macular hole configuration. Intraoperative SDOCT imaging identified additional membranes in two patients. Conclusion: The intraoperative use of handheld SDOCT imaging provides an efficient method for visualizing macular pathology. This technology may, in certain cases, help confirm or identify diseases that may be difficult to visualize during surgery.

Visualization of real-time intraoperative maneuvers with a microscope-mounted spectral domain optical coherence tomography system.

The advent of optical coherence tomography (OCT) has revolutionized our diagnostic and therapeutic capabilities in ophthalmology and vitreoretinal disease. In the clinic setting, OCT has touched nearly every aspect of vitreoretinal disease. More recently, OCT has been introduced the operating room theater. Intraoperative OCT (iOCT) has been used to successfully further our understanding of optic pit maculopathy, macular holes, epiretinal membranes, and retinopathy of prematurity.1–6 Limited systems are available for intraoperative use. All commercially available systems are handheld OCT devices or modified tabletop units, which allow for intraoperative imaging but require cessation of the surgical procedure to complete imaging. This precludes real-time feedback to the surgeon of the anatomical impact of surgical maneuvers and increases the duration of the surgical procedure. A microscope-mounted/integrated OCT (MMOCT) system allows for the integration of OCT into the real-time surgical platform.7,8 At the time of this report, two unique prototype systems have been described in the literature.5,7,8 Using a prototype MMOCT system, we previously demonstrated the feasibility of intraoperative imaging of surgical instruments, retinal effects of surgical contact, and primarily static surgical steps.7 To further seamlessly integrate OCT into the surgical platform, visualization of intraoperative motion and manipulation will be critical. Another critical component of integration will include the rapid localization of the surgical area of interest with the intraoperative spectral domain OCT (SD-OCT) device and quantitative information regarding the relative locations of the surgical instruments to the retinal tissue layers of interest. In this report, we describe a novel technique for visualizing intraoperative motion of surgical instruments with an MMOCT system.

Analysis of Pars Plana Vitrectomy for Optic Pit-Related Maculopathy With Intraoperative Optical Coherence Tomography A Possible Connection With the Vitreous Cavity

Optimal management of optic pit-related maculopathy remains to be determined. The fluid source for the maculopathy also remains controversial. In this article, we present a unique surgical technique for internal drainage of the intraretinal fluid and describe the intraoperative use of spectral-domain optical coherence tomography to assist in the surgical management of this condition. Pars plana vitrectomy was performed with elevation of the posterior hyaloid. Following an air-fluid exchange, aspiration over the optic nerve pit was performed. Following aspiration, intraoperative spectral-domain optical coherence tomography demonstrated collapse of the retinoschisis, strongly suggesting a connection between the vitreous cavity and the intraretinal fluid.

Macular Features From Spectral Domain Optical Coherence Tomography as an Adjunct to Indirect Ophthalmoscopy in Retinopathy of Prematurity

Purpose: To compare vitreoretinal pathology imaged with portable handheld spectral-domain optical coherence tomography (SD-OCT) to conventional indirect ophthalmoscopic examination in neonates undergoing screening for retinopathy of prematurity. Methods: Spectral-domain optical coherence tomography images were collected from 76 eyes of 38 neonates during 118 routine retinopathy of prematurity examinations. Imaging sessions in the Neonatal Intensive Care Unit were performed immediately after the subjects underwent a standard ophthalmic examination with indirect ophthalmoscopic by a pediatric ophthalmologist. Masked certified SD-OCT graders evaluated scans for preretinal and retinal findings including material in the vitreous, epiretinal membrane, intraretinal cystoid structures and deposits, optic nerve and vascular features, and severity and location of retinopathy of prematurity. The frequency of detection of these features by clinical examination and evaluation of SD-OCT images was compared to determine potential clinical advantages for each modality. Results: Portable SD-OCT imaging characterized macular features of retinal cystoid structures in 39% of examinations and epiretinal membrane in 32% of examinations. Neither feature was visualized by indirect ophthalmoscopy in any cases. The clinician using indirect ophthalmoscopy detected stage of retinopathy of prematurity and the presence or absence of Plus or pre-Plus disease. These were not visualized with SD-OCT. Conclusion: Spectral-domain optical coherence tomography provides new information about the premature infant retina that is of unknown importance relative to visual development and acuity. As used in this study, SD-OCT does not replace indirect ophthalmoscopy for evaluation of retinopathy of prematurity.

The Use of Optical Coherence Tomography in Intraoperative Ophthalmic Imaging

Optical coherence tomography (OCT) has transformed diagnostic ophthalmic imaging but until recently has been limited to the clinic setting. The development of spectral-domain OCT (SD-OCT), with its improved speed and resolution, along with the development of a handheld OCT scanner, enabled portable imaging of patients unable to sit in a conventional tabletop scanner. This handheld SD-OCT unit has proven useful in examinations under anesthesia and, more recently, in intraoperative imaging of preoperative and postoperative manipulations. Recently, several groups have pioneered the development of novel OCT modalities, such as microscope-mounted OCT systems. Although still immature, the development of these systems is directed toward real-time imaging of surgical maneuvers in the intraoperative setting. This article reviews intraoperative imaging of the posterior and anterior segment using the handheld SD-OCT and recent advances toward real-time microscope-mounted intrasurgical imaging.

Choroid Development and Feasibility of Choroidal Imaging in the Preterm and Term Infants Utilizing SD-OCT

PURPOSE To determine whether choroidal imaging is feasible in preterm and term infants using an 840-nm portable spectral domain optical coherence tomography (SD-OCT) system without the use of enhanced-depth imaging techniques and to assess choroidal development by comparing choroidal thickness of preterm infants, term infants, and adults. METHODS SD-OCT images were obtained from 86 preterm infants, 59 term infants, and nine adults using a portable SD-OCT system plus nine adults using a tabletop system. An unprocessed image across the macula from one randomly selected eye of each participant was selected for determination of whether the choroidal-scleral junction (CSJ) could be visualized and for measurement of choroidal thickness. RESULTS Subfoveal CSJ was visualized in 96% of young-preterm infants (imaged from 30-36 weeks postmenstrual age [PMA]); 78% of term-aged preterm infants (imaged from 37-42 weeks PMA); 49% of term infants; and 39% of adult subjects. Racial pigmentation did not affect CSJ visibility in young-preterm infants (P = 0.57). Subfoveal choroidal thickness (SFCT) in young-preterm infants, term-aged preterm infants, term infants, and adults was 176 ± 53 μm, 289 ± 92 μm, 329 ± 66 μm, and 258 ± 66 μm, respectively, and these were all statistically significantly different from one another except term-aged preterms to adults. CONCLUSIONS Infant choroid can be imaged with a portable SD-OCT system without enhanced depth imaging. Melanin in the RPE and choroid does not hinder outer choroidal imaging in young-preterm infants without advanced retinopathy of prematurity (ROP). In preterm infants, choroidal thickness increased with age but was thinner when compared to term infants suggesting delayed development due to ROP.