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Experimental retinal detachment. VI. The permeability of the blood-retinal barrier.

Fluorophotometry was used to study the permeability of the blood-retinal barrier in six monkeys with stable rhegmatogenous retinal detachments. Fluorescein transport was inhibited by probenecid. The rate of fluorescein disappearance (KvVv) was determined following intravitreal injection. In a separate experiment the equilibrium vitreous-plasma concentration ratio (Cv/Cp) was determined following intraperitoneal administration. Expressed in equivalent volumes of vitreous, the rate of fluorescein diffusion across the blood-retinal barrier (K'vVvCv/Cp) was 0.29 microL/min in control eyes and 0.73 microL/min in detached eyes. The rate of fluid movement across the blood-retinal barrier (K'vVv) [1 - (Cv/Cp)] was 2.89 microL/min in control eyes and 6.38 microL/min in detached eyes. Posterior movement of fluid contributes to retinal apposition under normal conditions and accounts for the rapid resolution of retinal detachment following closure of the retinal hole.

Animals↗

Axial intensity distribution analysis of the human retina with a confocal scanning laser tomograph.

We have analysed the change of reflected light intensity along the optical axis or axial intensity distribution in images acquired with a confocal scanning laser tomographic system in human fundus examination. We hypothesized that confocal light detection units used in scanning laser tomographs register light originating from multiple layers within the human macula and that intraretinal structures might also be observable. To test this hypothesis we examined the axial intensity distribution in human maculas of normal volunteers, patients with cystic and other macular abnormalities and in an artificial retina in a plastic eye model. A total of over 140 patients and volunteers were examined. We analysed this distribution in 20 normal healthy volunteer eyes found the origin of the artifacts that cause retinal vessels to appear elevated. We examined four patients with cystic maculas and were able to detect the presence of two structures in axial direction contributing to the axial intensity distribution. A plastic eye model with a cellophane sheet covering a fluid pocket was developed to mimic the appearance of a large macular cyst. The axial intensity distribution analysis showed the presence of two distinct gaussian profiles. The results of this study show that confocal scanning laser tomographic imaging of the human fundus allows extraction of information regarding the axial position of intraretinal layers and that correction for the deeper retinal reflections may allow more precision in imaging of the retinal surface.

Adult↗

Pressure changes in the eye due to an injection of inert gases: a theoretical model.

In the repair of retinal tears and detachments, the vitreous humor is often completely replaced with a temporary mixture of gases, one of which is not normally found in the bloodstream. The resulting bubble can then support the healing retina. There is diffusion of gases, however, from the bubble into the bloodstream and vice versa. This alters the intraocular pressure, with possible adverse consequences, as the intraocular pressure must be maintained within a certain range for the procedure to be successful. A simple model has been developed to predict the evolution of intraocular pressure over time, given a certain initial mixture of injected gases. This model could be useful in determining what mixture to use to support effectively and safely a healing retina.

Capillaries↗

Rips of the retinal pigmentepithelium.

A rip or rupture of the detached retinal pigment epithelium (RPE) with subsequent retraction of that layer is an often misdiagnosed affection of the posterior pole of the eye. The histologic appearance of this entity has to our knowledge not yet been published, but the fundus aspect and fluorescein angiography show that the focal absence of the pigmentepithelial layer is very likely. A rip is only seen in older age and it always appears in a detached RPE that often exists in combination with other features of a senile macular degeneration. Mostly the rip arises spontaneously but it may develop sometimes directly after laser coagulation of the detached RPE.

Aged↗

Joint application of hyperacuity perimetry and gap tests to assess visual function behind cataracts: initial trials.

We have developed two related clinical tests that offer potential in better assessing visual function behind an ocular opacity. The tests are resistant to the effects of opacities because they utilize a localization task (vernier acuity) rather than a resolution task. In this paper we report the initial trials in which we apply the two tests together. Results from six case studies (some with actual opacities and some with simulated opacities) illustrate both the conduct of the tests and their potential capabilities in detecting even very modest retinal dysfunction in the presence of opacities. These techniques offer considerable potential in the separation of a given acuity loss observed in the presence of cataract into a portion due to the opacity and a portion due to retinal dysfunction.

Aged↗

Epivascular glia and paravascular holes in normal human retina.

We examined the retinal surface of 28 autopsy eyes by scanning electron microscopy (SEM). Glialike cells or their processes, arranged in rows, were observed along retinal vessels in 22 eyes. Additionally, there were clusters of glialike cells over retinal vessels in 8 eyes. These proliferations ranged from focal to extensive ones, the latter resulting in distinct preretinal membranes. Focal defects of the superficial retina along the vessel were noted in 6 of 28 eyes. Transmission electron microscopic study in 2 surgically enucleated eyes with normal retinae revealed epivascular retinal degeneration and thinning of Müller cells. Glial processes appeared to be covering the defect of the internal limiting membrane and some projections of these cells continued inwards. These findings were consistent with the SEM findings of epivascular glialike structure. Our conclusions are that epivascular glialike structures and paravascular surface defects appear as a common finding in normal senile eyes, and that occasionally membranous formations arise from the epivascular area.

Adult↗

Intraocular diathermy coagulation.

Previously used transvitreal diathermy systems were found to be less than adequate. A new, safer 1.25 MHz medium frequency bipolar instrument is presented, which obviates most of the earlier drawbacks. Coagulation at the retinal surface can be obtained with as little as 0.15 J.

Diathermy↗

Types of avulsed retinal vessels associated with rhegmatogenous retinal detachment: treatment and results.

We performed a prospective study of 87 cases with avulsed retinal vessels in conjunction with tears and rhegmatogenous retinal detachment. The postoperative follow-up period ranged from 6 months to 5 years. The avulsed vessels were classified according to their location (peripheral or central) as well as with respect to their form (5 types). The surgical procedure comprised the fixation of an episcleral sponge implant (high indentation), cryoapplication, and, if necessary, laser coagulation or endodiathermy at a later stage. The postoperative condition of the avulsed vessel mainly depended on its location, the type of avulsion, and the buckle height.

Humans↗

Macular translocation with 360 degrees retinotomy for retinal pigment epithelial tear.

PURPOSE: To report a case of retinal pigment epithelial tear treated by macular translocation with 360 degrees retinotomy. METHODS: Interventional case report. A 75-year-old woman with neovascular age-related macular degeneration and retinal pigment epithelial tear underwent macular translocation with 360 degrees retinotomy and silicone oil tamponade. After 3 months, pars plana vitrectomy, silicone oil removal, and muscle surgery were performed. RESULTS: Twenty-two months after macular translocation surgery, the visual acuity of the patient had improved to 20/50 (preoperative 20/200). No proliferative vitreoretinopathy or recurrence of the choroidal neovascularisation was observed. CONCLUSIONS: Macular translocation surgery with 360 degrees retinotomy can improve vision in retinal pigment epithelial tear secondary to neovascular age-related macular degeneration.

Aged↗

Macular hole formation associated with idiopathic parafoveal telangiectasia.

BACKGROUND: To report the occurrence of a full thickness macular hole in association with idiopathic parafoveal telangiectasia. METHODS: Observational case report. RESULTS: A 60-year-old female with a history of bilateral idiopathic parafoveal telangiectasia presented with acute complaints of decreased vision and metamorphopsia in her right eye. The patient's retinal examination was significant for idiopathic parafoveal telangiectasia bilaterally, and a new, full-thickness macular hole in the right eye which was confirmed by optical coherence tomography. CONCLUSIONS: Full-thickness macular hole formation may occur in conjunction with idiopathic parafoveal telangiectasia, which has not been reported to date.

Female↗

Macular hole formation and spontaneous closure after vitrectomy for central retinal vein occlusion.

PURPOSE: The purpose was to describe the formation and spontaneous closure of an iatrogenic macular hole after vitrectomy for central retinal vein occlusion (CRVO). METHODS: A 45-year-old woman presented with loss of vision in the right eye due to CRVO. The left eye was normal. Best-corrected visual acuity (BCVA) was 3/60 in the right eye and 6/6 in the left. She underwent vitrectomy and radial optic neurotomy (RON) in the right eye. Fluorescein angiography and optical coherence tomography (OCT) were performed pre-operatively, on the first post-operative day, and subsequently at 1, 3, 6 and 12 months. RESULTS: There were no intra-operative complications. On the first post-operative day, fundus examination of the right eye revealed a small macular hole, confirmed by OCT. No additional intervention was carried out. Examination after a month revealed clearing of retinal haemorrhages, resolution of macular oedema and spontaneous closure of the macular hole. The closure was maintained until the last follow-up a year later. BCVA improved to 6/24 by 3 months, and was stable over the follow-up period. The left eye remained unchanged. CONCLUSION: While performing vitrectomy for CRVO, the induction of posterior vitreous detachment may deroof a foveal cyst in the highly oedematous macula to form a macular hole. A small macular hole, however, may close spontaneously without further intervention.

Female↗

Horseshoe-like macular tear following recurrent branch retinal vein occlusion.

BACKGROUND: A macular hole can develop as a late complication secondary to a branch retinal vein occlusion (BRVO). We report about an atypical horseshoe-like tear occurring in the fovea after recurrent BRVO. METHODS: An interventional case report. RESULTS: In 1997, a 53-year-old man was seen with an occlusion of macular part of inferior temporal vein of the retina on the left eye. After experiencing several recurrent BRVO in this eye, 6 years later he presented with a horseshoe-like tear in the fovea. Visual acuity was 20/200. The patient underwent standard three-port vitrectomy and installation of C3F8 16%. Intraoperatively, massive traction of the vitreous was detected on the edges of the tear. Six months after the operation, the tear remained attached. The visual acuity was 20/200. CONCLUSIONS: The uniqueness of the presented case is the occurrence of a macular tear following recurrent BRVO, its horseshoe-like shape and foveal location. To the best of our knowledge, this is the first report on a horseshoe-like tear seen in the fovea secondary to BRVO. We assume that chronic macular edema and retinal ischemia following BRVO were additional factors beside the vitreous traction, contributing to the formation of the macular tear. Anatomical closure of the tear and stabilisation of visual acuity can be achieved by vitreoretinal surgery.

Fluorescein Angiography↗

Confocal laser tomographic analysis of the retina in eyes with macular hole formation and other focal macular diseases.

To study the retinal surface in the human eye in normal and diseased states we used laser scanning tomography. The confocal arrangement of the laser tomographic scanner permits examination of retinal topography in the axis perpendicular to the retinal surface. The eyes examined with the laser tomographic scanner included normal eyes, eyes with macular holes, impending macular holes, radiation retinopathy, macular edema, photocoagulation scars, subfoveal scars, and serous detachment of the fovea associated with subretinal neovascularization. The laser tomographic scanner is a new method that allows measurements of the topography of the internal limiting membrane in the macular area and may improve our understanding of the pathophysiologic characteristics and treatment of a variety of disorders of the macula.

Adult↗

An evolutionary perspective on the photoreceptor damage response.

PURPOSE: To review recent advances related to the response to photoreceptor damage and to place this knowledge in an evolutionary context. DESIGN: Synthesis of published laboratory, clinical, and epidemiologic data. METHODS: The authors have synthesized the principal published findings related to the mechanism and function of the photoreceptor damage response with the goal of trying to understand the selective pressures that shaped its evolution. RESULTS: The past several years have seen considerable advances in understanding the molecular and cellular basis of the retina's response to photoreceptor damage. From their analysis of laboratory, clinical, and epidemiologic data, the authors suggest that the photoreceptor damage response may have evolved to counter the effects of retinal tears and detachment, infectious retinitis, and/or light damage. CONCLUSIONS: If the natural response to photoreceptor damage can be fully defined, it may be possible to augment desirable aspects of the damage response and/or suppress undesirable ones in the context of a wide variety of photoreceptor diseases.

Animals↗

High-definition and 3-dimensional imaging of macular pathologies with high-speed ultrahigh-resolution optical coherence tomography.

OBJECTIVE: To assess high-speed ultrahigh-resolution optical coherence tomography (OCT) image resolution, acquisition speed, image quality, and retinal coverage for the visualization of macular pathologies. DESIGN: Retrospective cross-sectional study. PARTICIPANTS: Five hundred eighty-eight eyes of 327 patients with various macular pathologies. METHODS: High-speed ultrahigh-resolution OCT images were obtained in 588 eyes of 327 patients with selected macular diseases. Ultrahigh-resolution OCT using Fourier/spectral domain detection achieves approximately 3-mum axial image resolutions, acquisition speeds of approximately 25 000 axial scans per second, and >3 times finer resolution and >50 times higher speed than standard OCT. Three scan protocols were investigated. The first acquires a small number of high-definition images through the fovea. The second acquires a raster series of high-transverse pixel density images. The third acquires 3-dimensional OCT data using a dense raster pattern. Three-dimensional OCT can generate OCT fundus images that enable precise registration of OCT images with the fundus. Using the OCT fundus images, OCT results were correlated with standard ophthalmoscopic examination techniques. MAIN OUTCOME MEASURES: High-definition macular pathologies. RESULTS: Macular holes, age-related macular degeneration, epiretinal membranes, diabetic retinopathy, retinal dystrophies, central serous chorioretinopathy, and other pathologies were imaged and correlated with ophthalmic examination, standard OCT, fundus photography, and fluorescein angiography, where applicable. High-speed ultrahigh-resolution OCT generates images of retinal pathologies with improved quality, more comprehensive retinal coverage, and more precise registration than standard OCT. The speed preserves retinal topography, thus enabling the visualization of subtle changes associated with disease. High-definition high-transverse pixel density OCT images improve visualization of photoreceptor and pigment epithelial morphology, as well as thin intraretinal and epiretinal structures. Three-dimensional OCT enables comprehensive retinal coverage, reduces sampling errors, and enables assessment of 3-dimensional pathology. CONCLUSIONS: High-definition 3-dimensional imaging using high-speed ultrahigh-resolution OCT improves image quality, retinal coverage, and registration. This new technology has the potential to become a useful tool for elucidating disease pathogenesis and improving disease diagnosis and management.

Adult↗