Selective laser trabeculoplasty reduces mean IOP and IOP variation in normal tension glaucoma patients

Mohammed K El Mallah1, Molly M Walsh2, Sandra S Stinnett2, Sanjay G Asrani21Ocala Eye, Ocala, Florida, USA; 2Duke University Eye Center, Durham, North Carolina, USAPurpose: To evaluate the effect of selective laser trabeculoplasty (SLT) in normal tension glaucoma (NTG) patients.Patients and methods: A retrospective review was performed of NTG patients who had undergone SLT at the Duke University Eye Center between 12/2002 and 7/2005. For each eye of each patient at pre-laser and post-laser time points, the IOP measurements were summarized by mean, standard deviation, and range. Then for each of these descriptive statistics, the differences between pre-laser and post-laser values were obtained. Statistical analysis was performed using a random effects model. Main outcome measures: difference in mean IOP, standard deviation of IOP, and range of IOP.Results: Thirty-one eyes of 18 patients were included for analysis. The average of the mean ­pre-operative IOP measurements was 14.3 ± 2.6 mmHg compared to 12.2 ± 1.7 mmHg (P < 0.001) post-operatively. The mean pre-operative standard deviation was 1.9 ± 0.9 mmHg compared to 1.0 ± 0.6 mmHg (P = 0.002) post-operatively while the mean IOP range prior to treatment was 4.5 ± 2.5 mmHg compared to 2.5 ± 1.9 mmHg (P = 0.017) after treatment.Conclusion: In this pilot study, SLT was found to lower mean IOP and intervisit IOP ­variation in NTG patients. Given the importance of IOP variation and its association with glaucoma ­progression, measurement of IOP variation following treatment with SLT may be considered.Keywords: SLT, NTG, laser, glaucom

Artifacts in Spectral-Domain Optical Coherence Tomography Measurements in Glaucoma

IMPORTANCE Spectral-domain optical coherence tomography (SD-OCT) has an integral role in the diagnosis and treatment of glaucoma. Understanding the types of artifacts commonly seen in the imaging of patients being evaluated for glaucoma will help physicians better implement these data in the care of patients. OBJECTIVES To determine the frequency and distribution of SD-OCT imaging artifacts in patients being evaluated for glaucoma and to provide examples of common artifacts. DESIGN, SETTING, AND PARTICIPANTS A retrospective cross-sectional study design was used to examine SD-OCT images (using Spectralis SD-OCT) of 277 consecutive patients who had a diagnosis of glaucoma of any stage or had suspected glaucoma. Retinal nerve fiber layer (RNFL) and macular thickness scans were included. For each scan, the final printout and the source images that generated the final printout were examined. If present, artifacts were classified as evident on the final printout or not and were categorized as to the primary source of the artifact (eg, ocular pathologic features or technician errors). Examples of common artifacts are provided. MAIN OUTCOMES AND MEASURES The presence of imaging artifacts. RESULTS In 277 consecutive patients, 131 macular thickness scans were obtained, and 277 RNFL scans were obtained. Of the macular thickness scans, 37 (28.2%; 95% CI, 20.8%-36.1%) had imaging artifacts. Six of these artifacts were not obvious on the final printout. Of the RNFL scans, 55 (19.9%; 95% CI, 15.2%-24.6%) contained artifacts. Seven of these artifacts were not evident on the final printout. The most common cause of artifacts for macular thickness and RNFL scans was ocular pathologic features, primarily the presence of an epiretinal membrane. CONCLUSIONS AND RELEVANCE It is likely that SD-OCT-related imaging artifacts occur in 15.2% to 36.1% of scans obtained in patients being evaluated for glaucoma. Some of these artifacts may not be evident on the final printout. Physicians should be alert to the possibility of artifacts, particularly in patients with ocular pathologic features such as an epiretinal membrane

COMPUTATIONAL MECHANICS OF THE SCLERA AND OPTIC NERVE HEAD (ONH): EFFECTS OF ONH SIZE AND PRESSURE RANGE

ABSTRACT Computational modeling was performed to study how loss of compliance of the eye and abnormally high pressures result in changes in stresses and strains that may impact the optic nerve in diseases such as glaucoma. Hemispherical finite element models of the eye were created in which scleral thickness varied from the equatorial region to the optic nerve head (ONH). Nonhomogeneous material properties were used to model the ONH as a continuous region softer than the adjacent sclera. The ONH and an adjacent buffer zone in the sclera were modeled with enough detail that the size of the ONH could be changed to account for variations observed in humans. The model was provided with appropriate dimensions typical of patients and nonlinear material properties with decreased compliance. Models with different ONH sizes were inflated in small steps to 55 mmHg (7.33 kPa), providing deformed configurations at intermediate pressures of 15, 30 and 45 mmHg, respectively. Color-coded maps of stress and strain components were rendered directly on deformed configurations of the eye model; and animations were produced that show both spatial and temporal variations of stresses and strains as internal pressure increases. Three-dimensional stresses and accompanying finite strains were similar for ONH sizes ranging form 1.5 to 2.5 mm in diameter. Stress and strain differences were estimated as pressure was increased from 15 to 25 mmHg, 30 to 40 mmHg, and 45 to 55 mmHg. Substantial changes occurred in stress and strain differences as the pressure range was varied with large changes occurring in the lowest pressure range for strain components and moderate increases in stress differences as pressures increase. INTRODUCTION High internal eye pressures associated with diseases such as glaucoma may contribute to elevated stresses in the sclera and increased deformation of the ONH. These mechanical factors may result in optic nerve damage emphasizing the need for detailed experimental studies correlated with realistic computational analysis under pathophysiologic conditions [1]

Feasibility of laser-targeted photoocclusion of the choriocapillary layer in rats

Purpose. A new method, laser-targeted photoocclusion, was developed to occlude choroidal neovascularization while minimizing damage to the overlying retina. The ability to occlude normal choriocapillary layer in rats was evaluated as a first test of die feasibility of treating choroidal neovascularization with this method. Method. A photosensitive agent, aluminum phdialocyanine tetrasulfonate, encapsulated in heat-sensitive liposomes, was administered intravenously along with carboxyfluorescein liposomes. A low-power argon laser (retinal power density of 5.7 W/cm 2 ) locally released a photosensitizer bolus, monitored by the simultaneous release of carboxyfluorescein. A diode laser (operating at 675 nm with a retinal power density of 0.27 W/cm 2 ) activated the photosensitizer with its release. Results. Vessels in the choriocapillary layer were occluded at day 3 after laser treatment and remained unchanged during die 30-day follow-up. Larger choroidal vessels and retinal capillaries remained perfused. Control experiments excluded possible effects of heat or activation of free photosensitizer. Pilot histologic studies showed no damage to the retinal pigment epithelium. Conclusions. Laser-targeted photoocclusion caused selective occlusion of normal choriocapillaries while sparing overlying retinal pigment epithelium and retinal vessels. The method has potential as a treatment of choroidal neovascularization diat may minimize iatrogenic loss of vision. Invest Ophthalmol Vis Sci. 1997;38:2702-2710 Age-related macular degeneration (ARMD) is one of the leading causes of severe loss of vision in people more than 50 years old. " 3 Choroidal neovascularization (CNV), which occurs in ARMD, is often treated by laser photocoagulation. However, the thermal damage and the scarring of large macular areas can caus

Cirrhosis and liver transplantation in patients co-infected with HIV and hepatitis B or C:an observational cohort study

This study assessed the likelihood of referral for liver transplantation assessment in a prospective cohort of patients co-infected with HIV and hepatitis B or C with complications of cirrhosis. There were 141 co-infected patients from 11 UK centres with at least one complication of cirrhosis recorded (either decompensation or hepatocellular carcinoma) out of 772 identified with cirrhosis and/or HCC. Only 23 of these 141 (16.3%) were referred for liver transplantation assessment, even though referral is recommended for co-infected patients after the first decompensation episode

Hue: A Quantitative Measure of Optic Nerve Color

Optic nerve color is one of the three cardinal features used to evaluate the optic nerve. Quantitative measures have been used to aid in evaluating each feature; however, most methods for evaluating optic nerve color require specialized non-commercially available equipment (microdensitometry and fundus reflectometry). Hue is a quantitative measurement of color that has been separated from an image's intensity and can be easily obtained from routine fundus photography without significant image manipulation. We hypothesize that hue can be easily used to differentiate between glaucomatous optic neuropathy (GOA) versus non-glaucomatous optic neuropathy (NGOA)