Unlocking stray light mysteries in the CoRot baffle with the time-of-flight method

Stray light (SL) has emerged as a primary limiting factor for space telescopes. Pre-launch testing is essential for validating performance and identifying potential issues. However, traditional methods do not enable the decomposition and identification of individual SL contributors. Consequently, when problems arise, resolving them often involves a cumbersome and risky trial-and-error approach. The time-of-flight (ToF) method was recently introduced, employing a pulsed laser source and ultrafast sensor to characterize individual SL contributors. A proof of concept was achieved using a simple three-lens system. In this paper, we apply the ToF method to a real space optical system: the spare model of the CoRoT baffle. We successfully measured individual SL contributors over a dynamic range of 10-11, identifying direct scattering on vane edges and two-step scattering paths. Our results provide a performance breakdown, differentiating intrinsic baffle SL from contributions arising from experimental conditions. Notably, the ToF method allowed us to discriminate air scattering, eliminating the need for expensive vacuum testing. The ToF provides unparallel insights, including defects identification. For instance, we identified the presence of localized dust particles causing significant SL. These results confirm the utility of the ToF method even for the most challenging space systems.

The Far Ultra-Violet imager on the ICON mission

ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N2 ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of O+ ions used to compute the nighttime ionospheric altitude distribution. ICON Far UltraViolet (FUV) imager is a CzernyTurner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to dominate the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with a UV source. The test and calibration program showed that ICON FUV meets its design requirements and is ready to be launched on the ICON spacecraft.

Characterization of human villous and extravillous trophoblasts isolated from first trimester placenta

Trophoblasts of the human placenta differentiate along two pathways to give either extravillous cytotrophoblasts (EVCT) with invasive properties and that are implicated in the implantation process, or villous cytotrophoblasts (VCT) that by cell fusion form multinucleated syncytiotrophoblasts. We report the first isolation and purification of these two cell types from the same chorionic villi of first trimester human placenta. We also studied their differentiation in vitro. Electron microscopy showed that in contrast to VCT, EVCT had no microvilli but contained large fibrinoid inclusions. EVCT cultures required a matrix to invade, and as previously established, VCT cultured on plastic dishes aggregated and fused to form syncytiotrophoblasts. These differentiation processes were characterized by a particular pattern of gene expression as assessed by real-time PCR and confirmed by immunocytochemical analysis of the corresponding proteins. EVCT cultured in vitro expressed high levels of HLA-G, c-erbB2, human placental lactogen, and very little human chorionic gonadotropin. Interestingly, TGFbeta2 was a marker of EVCT in vitro and in situ. These data offer a new tool for cell biologists to study the molecular mechanisms involved in human placental development and its pathology.

[Idiopathic polypoidal choroidal vasculopathy leading to blindness]

Idiopathic polypoidal choroidal vasculopathy (IPCV) has recently been recognized as a distinct cause of recurrent subretinal hemorrhages and exudates as well as multiple hemorrhagic retinal pigment epithelium detachments in the macula. IPCV is usually considered to have a good visual prognosis. We report the case of a 44-year-old woman with particularly severe bilateral macular and peripheral IPCV. The patient was followed for 13 years and had final visual acuity of counting fingers in the right eye and 20/400 in the left eye. Patients with IPCV with macular choroidal neovascularization tend to have a poor visual prognosis. This case of IPCV should alert the physician to be particularly attentive to the follow-up of these patients.

[Bilateral optic neuropathy in acute methanol intoxication. A case report]

We report a case of methanol blindness. Ophthalmoscopic examination disclosed swelling in the disc margins extending along the adjacent retinal nerve fiber layer. Although this optic neuropathy is now rare, prompt diagnosis and proper treatment in the acute phase can dramatically improve the prognosis.

Acute transient myopia induced by indapamide

PURPOSE

To report on a case of acute transient myopia associated with ciliochoroidal detachment induced by indapamide.

METHOD

Case report. Clinical examination, ultrasonography, and fluorescein angiography were performed during the acute phase of disease and convalescence.

RESULTS

After indapamide was discontinued, acute bilateral myopia, which was associated with anterior chamber shallowing and diffuse choroidal thickening, resolved spontaneously 8 days after onset. The initial angiography showed scattered islands of delayed fluorescein filling that disappeared without any permanent change by day 30.

CONCLUSION

Indapamide can induce spontaneously resolving transient myopia associated with diffuse choroidal thickening.

Long-term incidence of reopening of macular holes

OBJECTIVE

To report the incidence of macular hole reopening after initial successful surgery.

DESIGN

A noncomparative retrospective case series.

PARTICIPANTS

From a series of 137 consecutive cases of idiopathic macular holes operated on between August 1993 and May 1996, the authors analyzed the charts of 116 cases of successful surgery.

SETTING

A single university-based ophthalmology department.

INTERVENTION

Pars plana vitrectomy, posterior hyaloid peeling, fluid-air and air-gas exchange with a nonexpansile 17% C2F6 mixture followed by face-down positioning. Eighty-eight patients (64%) received autologous platelets as a biologic adjuvant. The anatomic success rate at the first postoperative month was 116 of 137 (85%). One hundred and six patients (91%) were followed up for more than 2 years.

MAIN OUTCOME MEASURE

Macular anatomic status.

RESULTS

Mean follow-up was 27 months. Eleven eyes of 11 patients (9.5%) had reopening of the macular hole. The mean period between hole surgery and reopening was 15.4 months (range, 8-29). In 8 of these 11 cases, reopening occurred after cataract extraction. In two cases, an epiretinal membrane was noted. In another case cystoid macular edema was present. The final anatomic success rate with one surgical procedure was 105 of 137 (77%). Eight reopened holes were reoperated on and all were anatomic successes at 1 month. However, four patients experienced a second reopening.

CONCLUSIONS

Macular hole reopening occurred in 9.5% of cases (11 of 116). The cause of reopening might have been any anatomic stress such as epiretinal membrane formation or macular edema. However, in most of our reopened cases, no definite cause was evident. Four patients experienced recurrent reopening.

Central retinal artery occlusion associated with head or neck pain revealing spontaneous internal carotid artery dissection

PURPOSE

To report two cases of head or neck pain and central retinal artery occlusion associated with spontaneous dissection of the ipsilateral internal carotid artery.

METHODS

Case reports.

RESULTS

We describe two cases of sudden visual loss caused by central retinal artery occlusion. Both cases were preceded by ipsilateral headaches or neck pain and tinnitus. The patient had no other neurological signs or history of trauma. In both cases, cerebral angiography revealed ipsilateral internal carotid artery dissection.

CONCLUSION

Ipsilateral headache or neck pain with tinnitus preceding central retinal artery occlusion is highly suggestive of internal carotid artery dissection. Early diagnosis and treatment may reduce the risk of hemispheric stroke.

Sclerochoroidal calcification associated with Gitelman syndrome

PURPOSE

To investigate sclerochoroidal calcification in a patient with Gitelman syndrome.

METHOD

Case report. Bilateral fundus abnormalities observed in a 58-year-old woman were documented with fluorescein angiography and tomodensitometry.

RESULTS

Symmetric yellow-white subretinal lesions were observed in the superotemporal midperiphery of the fundus of each eye. Tomodensitometry examination was consistent with calcium deposition. The medical history included Gitelman syndrome. Sclerochoroidal calcification probably resulted from the severe hypomagnesemia.

CONCLUSION

Gitelman syndrome may be a cause of sclerochoroidal calcification.

Macular hole formation: new data provided by optical coherence tomography

OBJECTIVE

To establish the sequence of events leading from vitreofoveal traction to full-thickness macular hole formation.

METHODS

Both eyes of 76 patients with a full-thickness macular hole in at least 1 eye were examined by biomicroscopy and optical coherence tomography.

RESULTS

Sixty-one fellow eyes had a normal macula. Optical coherence tomograms showed central detachment of the posterior hyaloid over the posterior pole in 19 cases (31%) and a perifoveal hyaloid detachment not detected on biomicroscopy in 26 cases (42%). In the 4 impending macular holes, optical coherence tomography disclosed various degrees of intrafoveal split or cyst, with adherence of the posterior hyaloid to the foveal center and convex perifoveal detachment. In the 14 stage 2 holes, eccentric opening of the roof of the hole was observed, and in the 24 stage 3 holes, the posterior hyaloid was detached from the entire posterior pole.

CONCLUSIONS

In fellow eyes of eyes with macular holes posterior hyaloid detachment begins around the macula, but the hyaloid remains adherent to the foveolar center, indicating the action of anteroposterior forces. This results in an intraretinal split evolving into a cystic space, and then to the disruption of the outer retinal layer and the opening of the foveal floor, thus constituting a full-thickness macular hole.

Visual outcome of surgery for epiretinal membranes with macular pseudoholes

OBJECTIVE

To evaluate the effect of macular pseudohole on visual results after epiretinal membrane (ERM) surgery.

DESIGN

Retrospective case-control study.

PARTICIPANTS

The postoperative results for 50 eyes with ERMs combined with pseudohole were compared with the results for a paired series of idiopathic ERMs without pseudohole operated on during the same period.

INTERVENTION

All patients underwent standard three-port pars plana vitrectomy, including core vitrectomy, and removal of the membrane.

MAIN OUTCOME MEASURES

Anatomic and functional evaluations were performed before and after surgery. Main outcome measures were postoperative visual acuity and the persistence or disappearance of the pseudohole.

RESULTS

For the patients with pseudohole, median preoperative visual acuity was 20/63 (range, 20/32-20/860) and median postoperative visual acuity was 20/40 (range, 20/20-20/860). Vision improved by 2 or more lines in 31 (62%) of 50 eyes. Forty eyes (80%) reached visual acuity of 20/50 or more. Pseudohole persisted in 22 eyes (44%) 3 months after surgery and in 15 eyes (30%) at 6 months. There was no difference in visual acuity, whether or not the pseudohole persisted. For the patients without pseudohole, median preoperative visual acuity was 20/63 (range, 20/32-20/860). Median postoperative visual acuity was 20/40 (range, 20/20-20/860). Vision improved by 2 or more lines in 37 eyes (74%). In 36 eyes (72%), it was 20/50 or more. Neither preoperative nor postoperative visual acuity differed significantly in the groups with and without pseudohole.

CONCLUSION

After surgery for idiopathic ERMs combined with pseudohole, visual outcome is good, and pseudohole has no adverse prognostic value. Pseudohole disappears inconstantly after surgery, but its persistence does not preclude good postoperative visual recovery.

Epiretinal membranes surrounding idiopathic macular holes

PURPOSE

To describe the features of the epiretinal membranes (ERMs) surrounding idiopathic macular holes.

METHODS

The charts of 83 consecutive patients (85 eyes) who underwent macular hole surgery with a systematic search for an ERM around the hole were reviewed. Visual acuity testing, fundus biomicroscopy, red free and blue filter fundus photographs, and fluorescein angiograms were performed before and after surgery. Eyes with and without ERM removal were compared.

RESULTS

An ERM was removed from 26 of 85 eyes (30.6%). ERMs were found more frequently in stage 4 than in stage 3 macular holes (76.9% versus 24.6%; P < 0.01). Holes had been present for longer in eyes with ERM than in those without (14.7 versus 8.6 months; P = 0.05). Fewer stage 3 holes with an ERM had an operculum than those without (P = 0.01). The outcome and complication rates were similar in eyes with an ERM and those without. Of the 24 ERMs detectable on blue filter fundus photographs, only 11 (45.6%) were visible on red free photographs.

CONCLUSION

We support the hypothesis that the presence of ERMs surrounding idiopathic macular holes is secondary to hole formation.