Association between retinal vein occlusion, axial length and vitreous chamber depth measured by optical low coherence reflectometry.

BACKGROUND: Results of ocular biometric measurements in retinal vein occlusion (RVO) eyes are still inconclusive and controversial. The aim of this study was to evaluate the association between ocular axial length (AL), vitreous chamber depth (VCD) and both central (CRVO) and branch retinal vein occlusions (BRVO) using optical low coherence reflectometry (OLCR). METHODS: Both eyes of 37 patients with unilateral CRVO (mean age: 66 +/- 14 years, male:female - 21:16) and 46 patients with unilateral BRVO (mean age: 63 +/- 12 years, male:female - 24:22) were enrolled in this study. The control group consisted of randomly selected single eyes of 67 age and gender matched volunteers without the presence or history of RVO (mean age: 64 +/- 14 years, male:female - 34:33). Optical biometry was performed by OLCR biometer (LenStar LS 900). Average keratometry readings, central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), AL and VCD of eyes with RVO were compared with those of fellow eyes using paired t-tests and with those of control eyes using independent t-tests. RESULTS: Mean CCT, ACD and LT, average keratometry readings of affected RVO eyes, unaffected fellow eyes and control eyes was not statistically different in either groups. In eyes with CRVO mean AL and VCD of affected eyes were significantly shorter than those of control eyes (p < 0.001, p < 0.05), mean difference in AL and VCD between the affected and control eyes was 0.56 +/- 0.15 mm and 0.45 +/- 0.19 mm, respectively. In eyes with BRVO, mean AL of the affected eyes was significantly shorter with a mean difference of 0.57 +/- 0.15 mm (p < 0.001) and the VCD was significantly shorter with a mean difference of 0.61 +/- 0.15 mm (p < 0.001) comparing with the control eyes. CONCLUSION: Shorter AL and VCD might be a potential anatomical predisposing factor for development either of CRVO or BRVO

The effect of cataract on early stage glaucoma detection using spatial and temporal contrast sensitivity tests

Background: To investigate the effect of cataract on the ability of spatial and temporal contrast sensitivity tests used to detect early glaucoma. Methods: Twenty-seven glaucoma subjects with early cataract (mean age 60 ±10.2 years) which constituted the test group were recruited together with twenty-seven controls (cataract only) matched for age and cataract type from a primary eye care setting. Contrast sensitivity to flickering gratings at 20 Hz and stationary gratings with and without glare, were measured for 0.5, 1.5 and 3 cycles per degree (cpd) in central vision. Perimetry and structural measurements with the Heidelberg Retinal Tomograph (HRT) were also performed. Results: After considering the effect of cataract, contrast sensitivity to stationary gratings was reduced in the test group compared with controls with a statistically significant mean difference of 0.2 log units independent of spatial frequency. The flicker test showed a significant difference between test and control group at 1.5 and 3 cpd (p = 0.019 and p = 0.011 respectively). The percentage of glaucoma patients who could not see the temporal modulation was much higher compared with their cataract only counterparts. A significant correlation was found between the reduction of contrast sensitivity caused by glare and the Glaucoma Probability Score (GPS) as measured with the HRT (p<0.005). Conclusions: These findings indicate that both spatial and temporal contrast sensitivity tests are suitable for distinguishing between vision loss as a consequence of glaucoma and vision loss caused by cataract only. The correlation between glare factor and GPS suggests that there may be an increase in intraocular stray light in glaucoma

Measurement of spatial and temporal behavior of H-alpha emission from Aditya tokamak using a diagnostic based on a photomultiplier tube array

A photo multiplier tube (PMT) array based spectroscopic diagnostic with fast time response of 10 mu s and spatial resolution similar to 3 cm has been developed and installed on Aditya tokamak to study the spatial and temporal behavior of H-alpha emissions from typical discharges. Collimated light has been collected from the plasma along 16 lines of sight passing through entire plasma poloidal cross section of Aditya and detected by two 8 channels PMT arrays after selecting H-alpha emission using interference filter. The studies are carried out during plasma formation phase of Aditya by changing vertical field and its delay with respect to loop voltage. It is observed that plasma initiated in the high field side in typical discharges of Aditya. The plasma formation position is matched with null field location estimated through simulation. (C) 2014 AIP Publishing LLC

A Geometrical Approach to a New Unified Field Theory

To identify the risk factors for development of peripapillary retinal splitting (schisis) in patients with glaucoma or suspicion of glaucoma.Glaucoma Clinic, Department of Ophthalmology, Northwestern University Feinberg School of Medicine, Chicago, IL.In this institutional cross-sectional study, 495 patients (990 eyes) who had undergone spectral-domain optical coherence tomography (OCT Spectralis HRA-OCT, Heidelberg Engineering) optic nerve head (ONH) imaging and did not have identifiable optic nerve pits, pseudopits or coloboma were included. OCT scans were reviewed by two observers.Presence of peripapillary retinal splitting identified on OCT raster scans.Eleven of 990 glaucoma and glaucoma suspect eyes (1.1%) of 7 patients (2 females, 5 males, mean age 64.5 ± 9.2 years) had peripapillary retinal splitting. Two of these 11 eyes had extension of the splitting into the macula but none to the fovea. Of these 11 patients, 2 (28.6%) were glaucoma suspects, 3 (42.9%) had primary open-angle glaucoma, 1 (14.3%) had chronic angle-closure glaucoma and 1 (14.3%) had pigmentary glaucoma. 7/11 (63.6%) eyes had vitreous traction to the disc visualized on OCT and 6/11 eyes (54.5%) had beta-zone peripapillary atrophy.We observed peripapillary retinal splitting in 1.1% of a series of 990 glaucoma and glaucoma-suspect eyes. Evidence of adherent vitreous with traction and peripapillary atrophy was found in a majority of the involved eyes. A comparison to an age and axial length matched cohort is required to determine if this is a condition that is associated with glaucoma