Coherent Off-Axis Terahertz Tomography with a Multi-Channel Array and f-theta Optics.

Terahertz tomography is a promising method among non-destructive inspection techniques to detect faults and defects in dielectric samples. Recently, image quality was improved significantly through the incorporation of a priori information and off-axis data. However, this improvement has come at the cost of increased measurement time. To aim toward industrial applications, it is therefore necessary to speed up the measurement by parallelizing the data acquisition employing multi-channel setups. In this work, we present two tomographic frequency-modulated continuous wave (FMCW) systems working at a bandwidth of 230-320 GHz, equipped with an eight-channel detector array, and we compare their imaging results with those of a single-pixel setup. While in the first system the additional channels are used exclusively to detect radiation refracted by the sample, the second system features an f-θ lens, focusing the beam at different positions on its flat focal plane, and thus utilizing the whole detector array directly. The usage of the f-θ lens in combination with a scanning mirror eliminates the necessity of the formerly used slow translation of a single-pixel transmitter. This opens up the potential for a significant increase in acquisition speed, in our case by a factor of four to five, respectively.

Dalteparin in the management of recent onset central retinal vein occlusion: a comparison with acetylsalicylic acid.

BACKGROUND: The present study assessed the therapeutic effects of dalteparin in patients who had recent onset central retinal vein occlusion (CRVO) as compared with those of acetylsalicylic acid (ASA). METHODS: Patients with recent onset of CRVO were randomly assigned to receive dalteparin subcutaneously every day for 20 days or ASA daily for the same period. Complete ophthalmic examinations were conducted at baseline and at each follow-up interval: 1 week and 1, 2, 3, 4, and 6 months later. Best-corrected visual acuity was assessed by an investigator blind to the treatment group. RESULTS: The mean 6-month change in logMAR visual acuity for dalteparin-treated patients was an increase of 5.5 letters (Early Treatment Diabetic Retinopathy Study chart) (-0.11 [SD 0.71] logMAR) and for ASA-treated patients was a decrease of 14 letters (+0.28 [SD 0.79] logMAR), representing a significant difference between the 2 groups (p = 0.016). One patient in the dalteparin group and 14 in the ASA group showed iris neovascularization (NVI) (2.1% vs. 30.4%, p = 0.0001). INTERPRETATION: Dalteparin was found to be superior to ASA in terms of improving visual acuity and preventing NVI over the first 6 months of treatment. Similar studies are recommended of other newer types of anticoagulants, especially those that could be used orally.

Dalteparin versus aspirin in recent-onset branch retinal vein occlusion: a randomized clinical trial.

BACKGROUND: Retinal vein occlusion is the second most common vascular disease of retina after diabetic retinopathy, affecting 1.6% of the population above the age of 40. The aim of this study was to compare the effect of dalteparin and aspirin in patients with recent-onset branch retinal vein occlusion. METHODS: A randomized clinical trial was conducted on patients with branch retinal vein occlusion of less than 30 days' duration. Ophthalmic, systemic, and hematologic evaluations were made. Visual acuity was measured with Early Treatment Diabetic Retinopathy Study chart. Patients in the dalteparin group received subcutaneous dalteparin 100 IU/kg twice daily for 10 days, then 100 IU/kg once daily for another 10 days while the patients in the aspirin group were given aspirin 100 mg daily throughout the study. RESULTS: Seventy-eight patients were enrolled, 37 in the dalteparin and 41 in the aspirin group. The patients were followed for six months. The visual outcomes of the two groups were compared. Although dalteparin improved mean visual acuity slightly more than aspirin, no statistically significant differences were found between the groups at one (P=0.37), two (P=0.16), three (P=0.11), or six (P=0.13) months. Resolution of macular edema and development of new vessels made no statistically significant difference between the groups [(P=0.08) and (P=0.49), respectively]. CONCLUSION: In recent-onset branch retinal vein occlusion, no significant difference was found in the final visual acuity between the patients treated by dalteparin or aspirin. A further study with larger sample size is recommended.

The impact of macular laser photocoagulation on contrast sensitivity function in patients with clinically significant macular edema.

BACKGROUND: Contrast sensitivity is an important aspect of visual function and is even more important for ordinary daily tasks than visual acuity. Contrast sensitivity function may be deteriorated to a significant level in diabetic retinopathy, especially in diabetic macular edema. The objective of this study was to determine the impact of macular laser photocoagulation-as the standard treatment of clinically significant macular edema-on contrast sensitivity function. METHODS: In a prospective noncomparative interventional case series, 17 patients with clinically significant bilateral macular edema and no history of prior macular laser photocoagulation were enrolled. Baseline visual acuity, contrast sensitivity function, and fluorescein angiography were obtained and reassessed three months after macular laser photocoagulation. RESULTS: Clinically significant macular edema resolved in 22 (65%) of 34 eyes, three months after their first session of macular laser photocoagulation. The mean pretreatment visual acuity was 24.5/40 (0.21 logMAR) +/-10.3/40. Three months after macular photocoagulation, visual acuity remained stable in 19 eyes, decreased in 12 eyes, and increased in three eyes. The mean post-treatment visual acuity was 24/40 (0.24 logMAR) +/-10.8/40. There was a statistically significant (P = 0.02) decrease in visual acuity following laser therapy. In subgroup analysis, this decrease in visual acuity was only observed in those with unresolved clinically significant macular edema. The mean contrast sensitivity threshold increased in all spatial frequencies by three months after macular photocoagulation. The maximum rise was observed in the frequency of 6.4 cycles per degree in the mid range of frequencies, with a pretreatment mean of 9.41 dB and a post-treatment mean of 11.50 dB (P<0.05). CONCLUSION: Contrast sensitivity function improved after macular laser photocoagulation in clinically significant macular edema patients.

Multifocal electroretinogram in clinically significant diabetic macular edema.

OBJECTIVE: To explore the multifocal electroretinogram in patients with nonproliferative diabetic retinopathy with clinically-significant macular edema. METHODS: Forty-one eyes with clinically significant macular edema were tested. The latencies and amplitudes of average responses of 5 eccentric rings from 0 to 26 degrees relative to the fixation point were compared with normal values obtained from 13 nondiabetic subjects. RESULTS: Local electroretinogram responses were significantly delayed and decreased in amplitude in patients with clinically-significant macular edema. CONCLUSION: Multifocal electroretinogram can be used to quantify the visual function in clinically significant macular edema.

Long-term effect of dalteparin in the prevention of neovascularization of iris in recent-onset central retinal vein occlusion.

BACKGROUND: To compare the long-term effect of dalteparin in the prevention of neovascularization of iris in recent-onset central retinal vein occlusion with that of aspirin. METHODS: A randomized controlled clinical trial was conducted on patients with central retinal vein occlusion of less than 30 days duration. Patients in the dalteparin group received subcutaneous dalteparin 100 IU/kg twice a day for 10 days, and then 100 IU/kg once a day for another ten days. In the aspirin group the patients received 100 mg aspirin daily throughout the study. RESULTS: Forty seven patients were enrolled, 24 in the dalteparin group and 23 in the aspirin group, and were followed up for one year. One (4.1%) of the 24 patients in dalteparin group, and 9 (39.1%) of 23 patients in aspirin group developed iris neovascularization. the difference was significant (P=0.0001). The visual outcomes of the two groups were compared, and a significant difference was found (P=0.016). CONCLUSION: Patients treated with dalteparin within 30 days of the onset of central retinal vein occlusion were less likely to develop neovascularization of iris. There was also a significant difference in the visual acuity between two groups.