Bernard Szirth

Effects of Prone and Reverse Trendelenburg Positioning on Ocular Parameters

Background:In a pilot study of awake volunteers, intraocular pressure (IOP), choroid layer thickness, and optic nerve diameter were shown to increase in the prone position over 5 h with a nonsignificant trend of attenuation using a 4-degree increase of table inclination. These effects have previously not been isolated from anesthetic and fluid administration over a prolonged period, using an adequate sample size. Methods:After institutional review board approval, 10 healthy volunteers underwent IOP measurement (Tono-Pen XL, Medtronic Solan, Jacksonville, FL) as well as choroidal thickness and optic nerve diameter assessment (Sonomed B-1000, Sonomed, Inc., Lake Success, NY, or the I3 System-ABD, Innovative Imaging, Inc., Sacramento, CA) on a Jackson table (Orthopedic Systems, Inc., Union City, CA), during 5 h horizontal prone and 5 h 4-degree reverse Trendelenburg positioning. Measurements were assessed as initial supine, initial prone, and hourly thereafter. Vital signs were recorded at each position and time point. Results:IOP, choroidal thickness, and optic nerve diameter were observed to increase with time in the prone position. A small degree of reverse Trendelenburg attenuated the increase in choroidal thickness but not IOP or optic nerve diameter. Conclusions:Prolonged prone positioning increases IOP, choroid layer thickness, and optic nerve diameter independent of anesthetics and intravenous fluid infusion and 4 degrees of table inclination (15 cm of head to foot vertical disparity) may not attenuate these effects.

DICOM transmission of simultaneous stereoscopic images of the optic nerve in patients with glaucoma.

We evaluated the Digital Imaging and Communications in Medicine (DICOM) standard for the transmission of stereoscopic images of the optic nerve. Digital optic nerve images were obtained from patients with glaucoma. Fifteen simultaneous stereo images from consecutive patients were analysed independently twice, in random order, by two glaucoma specialists to establish baseline values of vertical and horizontal cup-to-disc (CDV and CDH) ratios and image quality (1 = worst, 5 = best). Images were transmitted to a distant location and returned to the sending site using DICOM standards in both directions. The received images were reassessed again by the two glaucoma specialists. The image file size slightly increased for all received images (mean 2545 kByte) in comparison with the transmitted images (mean 2460 kByte). The mean baseline values for CDV, CDH and quality score were 0.66, 0.59 and 3.9, respectively. The corresponding mean values for the received images were 0.66, 0.62 and 3.73, respectively. The differences between transmitted and received images were not significant. Clinical interpretation of digital stereoscopic images of glaucomatous optic nerves appears to be unaffected by DICOM capture and transmission.

Software-Assisted Optic Nerve Assessment for Glaucoma Tele-Screening

Increased optic nerve head (ONH) cup-to-disc ratio (CDR) may indicate glaucoma but evaluation needs to be performed by a trained examiner. This research assessed new software to calculate CDR from ONH images. Digital stereoscopic ONH images from 28 subjects acquired during screening using a nonmydriatic 45-degree camera with 8.2-Megapixel resolution (Canon, Tokyo, Japan) were analyzed by 3 individuals with different levels of ophthalmic training: glaucoma specialist (GS), an optometrist (OD), and trainees. Images were logged and accessed by raters masked to each others evaluations. Images from two groups were included: normal-appearing ONH (Group 1) and confirmed glaucoma (Group 2). All images were captured in DICOM format. Images were evaluated on a 32-bit, 1,600 x 1,200-pixel resolution monitor. EyeScape software (v. 7.4, Synemed, Inc., Benicia, CA) was used for CDR analysis. Software CDR determination requires an operator to place ONH disc and cup contour lines. Once lines were placed, the software provided CDR calculations (range 0.00-1.00). A total of 84 ONH evaluations were analyzed. Overall CDR mean, standard deviation, standard error of the mean, and mean difference from GS CDR evaluations were determined. Reproducibility was similar for all operators. The trainee had a small, statistically significant greater CDR in group 1 and 2 evaluations. Evaluation of ONH images for CDR can be performed using EyeScape software, by individuals with different levels of ophthalmic training. Accurate determination of CDR is important in tele-screening for vision-threatening diseases, and can aid in identifying subjects with suspicious ONH in need of specialty eye care.

Use of the Proneview Helmet System with a modified table platform for open access to the eyes during prone spine surgery.

Permanent, perioperative visual loss (POVL) is a rare but devastating complication of surgery. The majority of reported POVL cases are associated with spine surgery conducted in the prone position (67%) (1). POVL appeared to be related to a change in a patient’s retinal and/or optic nerve perfusion (1–3). Our goal was to provide a clinically practical method for measuring intraocular pressure, ocular perfusion pressure, and ocular perfusion (using digital retinal vessel/optic disk imaging), so that clinicians may be guided in preventing POVL. Limited access to a prone surgical patient’s eyes makes it challenging to obtain safe, physiologic ocular measurements.

Feasibility of retinal screening in a pediatric population with type 1 diabetes mellitus.

PURPOSE To study the feasibility of using a nonmydriatic camera to screen children with type 1 diabetes mellitus (DM1) as young as 2 years for diabetic retinopathy. METHODS Prospective pilot imaging study involving children with DM1 aged 2 to 17 years. The screening consisted of: (1) intake form; (2) measurement of blood pressure, pulse, and oximetry; (3) assessment of visual acuity (SIMAV, Padova, Italy); and (4) nonmydriatic color imaging (Canon CX-1 45° 15.1 megapixel camera; Canon Corp., Tokyo, Japan). Images were assessed for signs of diabetic retinopathy and graded for quality on a scale of 1 to 5 by two clinicians. Kappa coefficient was calculated to determine inter-observer agreement. RESULTS One hundred four of 106 (98%) children underwent imaging (mean age: 11.1 years, 51% male, 88% white). One (1%) child had nonproliferative diabetic retinopathy and 2 (1.9%) had incidental findings. Only 62% of children had an eye examination within the past year, with children with DM1 for more than 5 years significantly more likely to have done so (P = .03). Children who had an eye examination within the past year were significantly older than their counterparts (P = .01). Images of high quality (grades 4 and 5) were acquired in 178 (86%) eyes, and images of some clinical value (grades ≥ 2) were obtained in 207 (99.5%) eyes. Inter-observer agreement for image quality was 0.896. CONCLUSIONS The feasibility of using a nonmydriatic camera to screen children as young as 2 years for changes related to diabetic eye disease was demonstrated. Nonmydriatic imaging may supplement standard dilated clinical ophthalmology examinations for select patient populations.

Fundus autofluorescence imaging in an ocular screening program

Purpose. To describe integration of fundus autofluorescence (FAF) imaging into an ocular screening program. Methods. Fifty consecutive screening participants were included in this prospective pilot imaging study. Color and FAF (530/640 nm exciter/barrier filters) images were obtained with a 15.1MP Canon nonmydriatic hybrid camera. A clinician evaluated the images on site to determine need for referral. Visual acuity (VA), intraocular pressure (IOP), and ocular pathology detected by color fundus and FAF imaging modalities were recorded. Results. Mean ± SD age was 47.4 ± 17.3 years. Fifty-two percent were female and 58% African American. Twenty-seven percent had a comprehensive ocular examination within the past year. Mean VA was 20/39 in the right eye and 20/40 in the left eye. Mean IOP was 15 mmHg bilaterally. Positive color and/or FAF findings were identified in nine (18%) individuals with diabetic retinopathy or macular edema (n = 4), focal RPE defects (n = 2), age-related macular degeneration (n = 1), central serous retinopathy (n = 1), and ocular trauma (n = 1). Conclusions. FAF was successfully integrated in our ocular screening program and aided in the identification of ocular pathology. Larger studies examining the utility of this technology in screening programs may be warranted.

Optic disc drusen in a child: diagnosis using noninvasive imaging tools.

Purpose To describe a case of bilateral optic nerve head drusen (ONHD) in a pediatric patient and the complementary use of advanced noninvasive imaging techniques to confirm this diagnosis. Case Report A 15-year-old female adolescent with type 1 diabetes and no ocular history was seen at a routine screening without complaints. Visual acuity was 20/20 bilaterally, and visual fields using frequency doubling technology (Zeiss Humphrey Systems, Dublin, CA) were within normal limits. Fundus photography (CX-1 Mydriatic/Non-Mydriatic Hybrid Digital Retinal Camera, Canon, Toyko, Japan) showed slight elevation of the left disc margin, with lack of physiologic cup, elevation of the inferior neuroretinal rim, and no swelling of the nerve fiber layer. Fundus autofluorescence image of the left eye showed hyperfluorescence in the inferior optic disc. Red/green/blue channel separation analysis using the blue channel (Eye-Q software, Canon, Irvine, CA) showed elevation of the nerve fiber layer without obscuration of small vessels surrounding the left optic disc. Embossed technique highlighted the drusen in the left disc. B-scan ultrasound (Eye Cubed, Ellex, Adelaide, Australia) showed a hyperechoic focus on the optic disc with posterior shadowing and corresponding spike on A-scan in both eyes, indicative of bilateral drusen. Optical coherence tomography (RTVue, Optovue, Fremont, CA) showed an elevation in the ONH corresponding to the drusen. Conclusions The complementary use of noninvasive imaging modalities such as fundus autofluorescence, red/green/blue separation, B-scan, and optical coherence tomography is important in confirming the diagnosis of ONHD in pediatric patients. They allow us to rule out more serious conditions and avoid unnecessary, costly, and invasive investigative procedures, relieving young patients and their families of potential financial and emotional burdens.

Structural Changes by Spectral Domain Optical Coherence Tomography in Patients With Type 1 Diabetes Mellitus

Background: With a possible increase in the prevalence of type 1 diabetes mellitus (DM1), the pediatric patient population is expected to be at risk for other health care complications. Current imaging modalities, such as the spectral domain optical coherence tomography (SD-OCT), that allow micron resolution imaging of the retina have become a standard of care for showing morphological changes seen in the retina in adults with diabetes. Such pathologies can be associated with known risk factors such as poor glycemic control (HbA1C) and body mass index (BMI). Methods: A comprehensive screening was performed in subjects with DM1 including nonmydriatic fundus imaging (Canon, CR2 Plus-AF with EOS-60D, Tokyo, Japan) and SD-OCT imaging (Optovue, iVue, Fremont, CA). SD-OCT scans were acquired showing macular thickness (MT) and thickness of the parafoveal regions and the perifoveal regions. Associations of macular, paramacular, and perimacular thickness were analyzed as a function of HbA1C and BMI by simple linear regressions. Results: SD-OCT changes were analyzed in eyes of subjects with DM1 and normal fundus appearance by color imaging. Linear regression analysis of thickness of macula right eye (RT), paramacula RT, paramacula left eye (LT), perimacula LT with BMI were statistically significant (P < .05). HbA1C >7.5% was also found statistically significant in the macula RT, paramacula RT, paramacula LT, perimacula RT, and perimacula LT. A general trend of thickening of the macula, paramacula, and perimacula was observed with increasing HbA1C (>7.5%) and increasing BMI; however, no statistical significance was found. Conclusions: SD-OCT with retinal imaging was feasible in young individuals with DM1 and revealed ultrastructural macular and perimacular changes prior to manifest clinical disease.

Effect of Head Elevation on Intraocular Pressure and Retinal Imaging in the Prone Position

Conclusions: Non-invasive cerebral oxygenation monitoring in pediatric Moyamoya patients undergoing pial synangiosis is technically feasible. Surgical field illumination through a craniotomy does not significantly affect rSO2 measurement. Our preliminary experience suggests that NIRS is an insensitive predictor of pre-existing infarct or intraoperative cerebral ischemia in this patient population. Continued research may reveal whether rSO2 is correlated with other physiologic parameters or clinical outcome. References: 1. Adelson PD, Scott RM. Pial synangiosis for Moyamoya syndrome in children. Pediatr Neurosurg. 1995;23(1):26–33. 2. Scott RM, Smith JL, Robertson RL, et al. Long-term outcome in children with Moyamoya syndrome after cranial revascularization by pial synangiosis. J Neurosurg (Pediatrics 2). 2004;100:142–49. 3. Tobias JD. Cerebral oxygenation monitoring: near-infrared spectroscopy. Expert Rev Med Devices. 2006;3(2):235–43.

Are Disposable and Standard Gonioscopy Lenses Comparable

Purpose: Gonioscopy is important in the evaluation and treatment of glaucoma. With increased scrutiny of acceptable sterilization processes for health care instruments, disposable gonioscopy lenses have recently been introduced. Single-time use lenses are theorized to decrease infection risk and eliminate the issue of wear and tear seen on standard, reusable lenses. However, patient care would be compromised if the quality of images produced by the disposable lens were inferior to those produced by the reusable lens. The purpose of this study was to compare the quality of images produced by disposable versus standard gonioscopy lenses. Materials and Methods: A disposable single mirror lens (Sensor Medical Technology) and a standard Volk G-1 gonioscopy lens were used to image 21 volunteers who were prospectively recruited for the study. Images of the inferior and temporal angles of each subject’s left eye were acquired using a slit-lamp camera through the disposable and standard gonioscopy lens. In total, 74 images were graded using the Spaeth gonioscopic system and for clarity and quality. Clarity was scored as 1 or 2 and defined as either (1) all structures perceived or (2) all structures not perceived. Quality was scored as 1, 2, or 3, and defined as (1) all angle landmarks clear and well focused, (2) some angle landmarks clear, others blurred, or (3) angle landmarks could not be ascertained. The 74 images were divided into images taken with the disposable single mirror lens and images taken with the standard Volk G-1 gonioscopy lens. The clarity and quality scores for each of these 2 image groups were averaged and P-values were calculated. Results: Average quality of images produced with the standard lens was 1.46±0.56 compared with 1.54±0.61 for those produced with the disposable lens (P=0.55). Average clarity of images produced with the standard lens was 1.47±0.51 compared with 1.49±0.51 (P=0.90) with the disposable lens. Conclusions: We conclude that there is no significant difference in quality of images produced with standard versus disposable gonioscopy lenses. Disposable gonioscopy lenses may be an acceptable alternative to standard reusable lenses, especially in conditions where sterilization is difficult.