Tobias Stupp

Pathological changes in human retinal ganglion cells associated with diabetic and hypertensive retinopathy.

BackgroundTo examine whether systemic diseases like diabetes and arterial hypertension, which frequently cause retinopathies leading to blindness effect the morphology of retinal ganglion cells (RGC).MethodsHistological retina material with a history of being untreated, or laser-coagulated (LC) diabetic retinopathy (DR), or arterial hypertensive retinopathy (AHR) was used. The RGC were labeled by introducing crystals of the fluorescent carbocyanine dye DiI into the nerve fiber layer, which contains ganglion cell axons.ResultsThe typical silhouettes of both major types of RGC, parasol and midget cells, were identified. The axons in DR and AHR retinas showed morphology changes such as irregular swelling and beading. Dendritic field sizes were significantly reduced in RGC of both the hypertonic and diabetic retinas. A significant reduction in branching frequency was evident in both the diabetic and hypertonic retinas, in both the midget and the parasol cells. In LC retinas, both parasol and midget RGC were observed within the LC spots, although their numbers were dramatically decreased compared with normal retinas.ConclusionsThe data suggest that diabetes and arterial hypertonia have similar effects on the morphology of RGC, in addition to causing microvascular alterations and bleeding. Therefore, therapeutic measures and prognostic outcomes in diabetic and hypertensive retinopathy should also consider regressive changes in retinal neurons.

Multifocal Electroretinography Changes in the Macula at High Altitude: A Report of Three Cases

Background: To evaluate the short- and long-term effects of high-altitude hypobaric hypoxia on macula morphology and function during ascents, acclimatizations, and descents between 500 m and 5,650 m, macula function was evaluated in three healthy climbers of a trekking expedition. Methods:Macula physiology was tested with multifocal electroretinography (MF ERG), near and farvisual acuity, and Amsler grid tests. Macula morphology was tested with optical coherence tomography (OCT) and with stereoscopic fundoscopy obtained 1 week before ascent, as well as 1 week and 2 weeks after high-altitude exposure. The following physiological parameters indicative of acclimatization were compared daily during the expedition at altitudes between 500 m and 5,050 m: hemoglobin, oxygen saturation, resting heart rate, retinal findings, and the Lake Louise score of acclimatization. Results: The central macula MF ERG responses were significantly reduced 1 week after high-altitude exposure, and had recovered by the follow-up examination performed during the following week. Near visual acuity and Amsler grid tests remained unaffected at both follow-up examinations. No significant changes were found in the follow-up OCT and daily fundoscopy examinations in all three well-acclimatized climbers. Conclusions: High-altitude hypobaric hypoxia affects the function of the highly sensitive macula region. This suggests that the exposure of persons with macula diseases such as age-related macula degeneration, tapetoretinal degeneration, or diabetic retinopathy to high altitudes may influence the disease progression. For this reason, this population should avoid prolonged and unnecessary high-altitude exposure without proper acclimatization.

Ultrasonic visualization of the effect of blinking on the lacrimal pump mechanism

BackgroundThe role of the lacrimal sac (LS) and the medial canthal tendon in the lacrimal pump mechanism is controversial. This study used ultrasonic visualization to analyze this phenomenon.MethodsMovements of the LS and the medial canthal tendon during blinking were visualized with sonography. In addition, the maximal profile area of the LS was measured before and after blinking using 15-MHz sonography in 14 individuals with a normal lacrimal drainage system and in six patients with lacrimal duct obstruction.ResultsThe upper part of the LS could be located as an echolucent structure between the lacrimal bone and the medial canthal tendon. The medial canthal tendon appeared to compress the LS during lid closure and release the LS during lid opening. The measured profile area of the visible normal LS at the compression time decreased by 50%. The dilated LS of patients with obstruction could also be compressed by the orbital muscle on blinking, but the maximum area decrease was only 15.5%.ConclusionThe findings imply that the lacrimal part of the orbicularis muscle contracts during blinking, with the medial canthal tendon compressing the LS in a cranial direction. Completion of lid closure then compresses both canaliculi and LS, forcing the intrasacral fluid through the drainage system. The expansion of the LS during the opening phase of the blink causes suction, and after opening of the punctal areas the canaliculi and LS vacuum breaks to reload with tear fluid. These findings demonstrate the importance of the orbicularis muscle and the medial canthal tendon for the lacrimal pump mechanism during blinking.

Morphometric examination of human and monkey retinal ganglion cells within the papillomacular area.

Purpose: To examine the morphology of the retinal ganglion cells (RGCs) in the lesser characterized area lying between the optic disk and the macula that consists of the central papillomacular area (PMA) and the arcuate papillomacular bundle (PMB). Methods: Nineteen human and 10 monkey (Macaca fascicularis) retinas obtained after death were used in the study. Perikaryal, axonal, and dendritic silhouettes were examined by postvital application of the fluorescent dye DiI, which specifically labeled RGCs when placed onto the optic fiber layer. The retinas were freed from surrounding tissue, prepared as flat mounts on a nitrocellulose filter, and fixed overnight in 4% paraformaldehyde. DiI diffuses along the membranes of ganglion cell axons, thereby completely labeling them, their cell bodies, and dendrites, which enables the RGCs to be examined with fluorescence microscopy. Results: In both species, midget cells represented most of the RGCs within the PMA (96.15%) and possessed small, umbrella-like dendrites oriented toward the deeper retinal layers. Parasol cells were less abundant in both species and had small, typical symmetric dendrites. Also along the PMB, midget cells represented most cells (91.52%), whereas only 8.47% could be categorized as parasol cells. In both species, parasol cells of the PMB extended dendrites, which were oriented perpendicular to the axons. Conclusions: The data show that the PMA and PMB mainly contain small midget cells of typical morphology and size but with atypically oriented dendrites, which are only characteristic for this retinal area.

A coculture assay to visualize and monitor interactions between migrating glioma cells and nerve fibers

Glioma-cell migration is usually assessed in dissociated cell cultures, spheroid cultures, acute brain slices and intracranial implantation models. However, the interactions between migrating glioma cells and neuronal tracts remain poorly understood. We describe here a protocol for the coculture of glioma cells with myelinated axons in vitro. Unlike other methods, this protocol allows the creation of in vitro conditions that largely mimic the complex in vivo environment. First, long retinal axons from embryonic chicken are formed in an organotypic culture. Glioma cells are then positioned in the vicinity of the explants to allow them to contact the axons, interact with them and eventually migrate along them. High-resolution video microscopy and confocal microscopy can be used to monitor the migratory behavior. This protocol, which takes about 5 days to complete, could be applied to different types of tumor cells that interact with neurites, and is suitable for pharmacological and genetic approaches aimed at elucidating mechanisms underlying tumor migration.

Acute posterior multifocal placoid pigment epitheliopathy with concurrent cerebral vasculitis and sarcoidosis

Dear Editor, Acute posterior multifocal placoid pigment epitheliopathy (APMPPE) is a distinct clinical entity of unknown origin, characterized by the acute onset of multiple lesions at the posterior retinal pole at the pigment epithelium level. The clinical course is usually self-limited. In this report, a case of APMPPE emerging simultanously with sarcoidosis and CNS vascular abnormalities is described, suggesting that APMPPE is associated with a generalized inflammatory disease. A 40-year-old woman presented with bilateral visual field defects. Ophthalmoscopy showed multiple yellowwhite placoid lesions at the posterior pole of both eyes (Fig. 1a). Fluorescein angiography demonstrated an early hypofluorescence and a late hyperfluorescence of the lesions characteristic of APMPPE (Fig. 1b). The medical history included episodes of fever, cough and painful nodular skin lesions. Biopsy of these skin lesions demonstrated granulomatous epitheloid cells consistent with erythema nodosum. X-ray disclosed bilateral enlargement of the hilar lymph nodes, suggestive of sarcoidosis. Bronchoalveolar lavage showed a high CD4/CD8 ratio of 3.6: transbronchial biopsy revealed non-caseating granulomas (Fig. 2a), and the serum level of angiotension-converting enzyme was elevated. Cranial MRI revealed stenosis of the left middle cerebral artery (Fig. 2b). There are a few reports on associations of APMPPE with either probable sarcoidosis [1, 2] or CNS abnormalities [3]. Histopathological studies have shown the latter to be caused by granulomatous arteritis of medium-sized arteries [4].

Implantable visual prostheses.

Visual impairment and blindness is primarily caused by optic neuropathies like injuries and glaucomas, as well as retinopathies like agerelated macular degeneration (MD), systemic diseases like diabetes, hypertonia and hereditary retinitis pigmentosa (RP). These pathological conditions may affect retinal photoreceptors, or retinal pigment epithelium, or particular subsets of retinal neurons, and in particular retinal ganglion cells (RGCs). The RGCs which connect the retina with the brain are unique cells with extremely long axons bridging the distance from the retina to visual relays within the thalamus and midbrain, being therefore vulnerable to heterogeneous pathological conditions along this pathway. When becoming mature, RGCs loose the ability to divide and to regenerate their accidentally or experimentally injured axons. Consequently, any loss of RGCs is irreversible and results to loss of visual function. The advent of micro- and nanotechnology, and the construction of artificial implants prompted to create visual prostheses which aimed at compensating for the loss of visual function in particular cases. The purpose of the present contribution is to review the considerable engineering expertise that is essential to fabricate current visual prostheses in connection with their functional features and applicability to the animal and human eye. In this chapter, 1) Retinal and cortical implants are introduced, with particular emphasis given to the requirements they have to fulfil in order to replace very complex functions like vision. 2) Advanced work on material research is presented both from the technological and from the biocompatibility aspect as prerequisites of any perspectives for implantation. 3) Ultimately, experimental studies are presented showing the shaping of implants, the procedures of testing their biocompatibility and essential modifications to improve the interfaces between technical devices and the biological environment. The review ends by pointing to future perspectives in the rapidly accelerating process of visual prosthetics and in the increasing hope that restoration of the visual system becomes reality.

Association between congenital nasolacrimal duct obstruction and delivery by cesarean section.

OBJECTIVE Congenital nasolacrimal duct obstruction (CNDO) is the most common cause of neonatal epiphora. Persistence can lead to chronic dacryocystitis and amblyopia. This study analyzed the association between the incidence of CNDO and delivery by cesarean section. STUDY DESIGN This was a retrospective cohort study of 386 children with CNDO (born between 2000 and 2008). The incidence of the delivery mode in patients with CNDO was compared with data from a corresponding population derived from annual birth statistics. RESULTS There was no statistically significant association between the overall cesarean section rate and the incidence of CNDO, but primary cesarean section was significantly more frequent among patients with CNDO (73.15%, p < 0.05). The difference was significant for both genders for the period from 2000 to 2008 (p < 0.05%). The relative risk for CNDO was 1.7-fold increased in children delivered by primary cesarean section. CONCLUSION Primary cesarean section may be a risk factor for CNDO.

Postnatal visual deprivation in rats regulates several retinal genes and proteins, including differentiation-associated fibroblast growth factor-2.

Little is known about the retinal cellular basis of amblyopia, which is a developmental disease characterized by impaired visual acuity. This study examined the retinal transcripts associated with experimentally induced unilateral amblyopia in rats. Surgical tarsorrhaphy of the eyelids on one side was performed in pups prior to eye opening at postnatal day 14, thereby preventing any visual experience. This condition was maintained for over 2 months, after which electroretinograms (ERGs) were recorded, the retinal ganglion cell (RGC) arrangement and number were determined using neuroanatomical tracing, the retinal transcripts were studied using microarray analysis, regulated mRNAs were confirmed with quantitative reverse-transcriptase PCR, and proteins were stained using Western blotting and immunohistochemistry. An attenuated ERG was found in eyes that were deprived of visual experience. Retrograde neuroanatomical staining disclosed a larger number of RGCs within the retina on the visually deprived side compared to the non-deprived, control side, and a multilayered distribution of RGCs. At the retinomic level, several transcripts associated with retinal differentiation, such as fibroblast growth factor 2 (FGF-2), were either up- or downregulated. Most of the transcripts could be verified at the mRNA level. To unravel the role of a differentiation-associated protein, we tested FGF-2 in dissociated postnatal retinal cell cultures and found that FGF-2 is a potent factor triggering ganglion cell differentiation. The data suggest that visual experience shapes the postnatal retinal differentiation, whereas visual deprivation induces changes at the functional, cellular and molecular levels within the retina.

Effect of botulinum toxin A on the intraocular pressure and the retina in an animal model

Objective: The purpose of our study was to investigate the effect of an inadvertent intravitreal injection of botulinum toxin A (BTA) on the intraocular pressure (IOP) and the retina in an animal model. Methods: BTA was injected intravitreally in normotensive rats. IOP was measured preoperatively as well as 1, 2, and 4 weeks postoperatively. Retinas were stained in vivo using a retrograde labelling technique and the density of retinal ganglion cells (RGCs) was determined. Immunohistochemistry was performed for rhodopsin and retinal glial fibrillary acidic protein (GFAP). Results: Significant temporary IOP elevation occurred in all groups in the immediate postoperative period (ANOVA, p < 0.05). IOP changes in the intermediate period were not statistically significant (ANOVA, p > 0.05). The differences in the density of RGCs after BTA injection were not statistically significant (ANOVA, p > 0.05). All retinas displayed the same immunostaining pattern for rhodopsin and GFAP. Conclusion: Our findings indicate that BTA has probably no severe impact on IOP and the retina after an inadvertent intravitreal injection. However, temporary rise of IOP may possibly occur in the immediate postoperative period due to a volume-effect.