Changes in Retinal OCT and Their Correlations with Neurological Disability in Early ALS Patients, a Follow-Up Study

BACKGROUND

To compare early visual changes in amyotrophic lateral sclerosis (ALS) patients with healthy controls in a baseline exploration, to follow-up the patients after 6 months, and to correlate these visual changes with neurological disability.

METHODS

All patients underwent a comprehensive neurological and ophthalmological examination. A linear mixed analysis and Bonferroni p-value correction were performed, testing four comparisons as follows: Control baseline vs. control follow-up, control baseline vs. ALS baseline, control follow-up vs. ALS follow-up, and ALS baseline vs. ALS follow-up.

RESULTS

The mean time from the diagnosis was 10.80 ± 5.5 months. The analysis of the optical coherence tomography (OCT) showed: (1) In ALS baseline vs. control baseline, a macular significantly increased thickness of the inner macular ring temporal and inferior areas; (2) in ALS follow-up vs. ALS baseline, a significant macular thinning in the inner and outer macular ring inferior areas; (3) in ALS follow-up vs. ALS baseline, a significant peripapillary retinal nerve fiber layer (pRNFL) thinning in the superior and inferior quadrants; and (4) ALS patients showed a moderate correlation between some OCT pRNFL parameters and Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R) score.

CONCLUSION

The OCT showed retinal changes in patients with motoneuron disease and could serve as a complementary tool for studying ALS.

Neuroprotective and Anti-Inflammatory Effects of a Hydrophilic Saffron Extract in a Model of Glaucoma

Glaucoma is a neurodegenerative disease characterized by the loss of retinal ganglion cells (RGCs). An increase in the intraocular pressure is the principal risk factor for such loss, but controlling this pressure does not always prevent glaucomatous damage. Activation of immune cells resident in the retina (microglia) may contribute to RGC death. Thus, a substance with anti-inflammatory activity may protect against RGC degeneration. This study investigated the neuroprotective and anti-inflammatory effects of a hydrophilic saffron extract standardized to 3% crocin content in a mouse model of unilateral, laser-induced ocular hypertension (OHT). Treatment with saffron extract decreased microglion numbers and morphological signs of their activation, including soma size and process retraction, both in OHT and in contralateral eyes. Saffron extract treatment also partially reversed OHT-induced down-regulation of P2RY12. In addition, the extract prevented retinal ganglion cell death in OHT eyes. Oral administration of saffron extract was able to decrease the neuroinflammation associated with increased intraocular pressure, preventing retinal ganglion cell death. Our findings indicate that saffron extract may exert a protective effect in glaucomatous pathology.

Changes in visual function and retinal structure in the progression of Alzheimer's disease

BACKGROUND

Alzheimer's Disease (AD) can cause degeneration in the retina and optic nerve either directly, as a result of amyloid beta deposits, or secondarily, as a result of the degradation of the visual cortex. These effects raise the possibility that tracking ophthalmologic changes in the retina can be used to assess neurodegeneration in AD. This study aimed to detect retinal changes and associated functional changes in three groups of patients consisting of AD patients with mild disease, AD patients with moderate disease and healthy controls by using non-invasive psychophysical ophthalmological tests and optical coherence tomography (OCT).

METHODS

We included 39 patients with mild AD, 21 patients with moderate AD and 40 age-matched healthy controls. Both patients and controls were ophthalmologically healthy. Visual acuity, contrast sensitivity, colour perception, visual integration, and choroidal thicknesses were measured. In addition, OCT and OCT angiography (OCTA) were applied.

FINDINGS

Visual acuity, contrast sensitivity, colour perception, and visual integration were significantly lower in AD patients than in healthy controls. Compared to healthy controls, macular thinning in the central region was significant in the mild AD patients, while macular thickening in the central region was found in the moderate AD group. The analysis of macular layers revealed significant thinning of the retinal nerve fibre layer, the ganglion cell layer and the outer plexiform layer in AD patients relative to controls. Conversely, significant thickening was observed in the outer nuclear layer of the patients. However, mild AD was associated with significant thinning of the subfovea and the nasal and inferior sectors of the choroid. Significant superonasal and inferotemporal peripapillary thinning was observed in patients with moderate disease.

CONCLUSIONS

The first changes in the mild AD patients appear in the psychophysical tests and in the central macula with a decrease in the central retinal thickness. When there was a disease progression to moderate AD, psychophysical tests remained stable with respect to the decrease in mild AD, but significant thinning in the peripapillary retina and thickening in the central retina appeared. The presence of AD is best indicated based on contrast sensitivity.

Retinal glial changes in Alzheimer's disease - A review

Alzheimer's disease (AD) is a neurodegenerative dementia characterized by the deposition of extracellular β-amyloid (Aβ) plaques and the presence of neurofibrillary tangles. Until now, the techniques used to analyze these deposits have been difficult to access, invasive, and expensive. This leads us to consider new access routes to the central nervous system (CNS), allowing us to diagnose the disease before the first symptoms appear. Recent studies have shown that microglial and macroglial cell activation could play a role in the development of this disease. Glial cells in the CNS can respond to various damages, such as neurodegenerative pathologies, with morphological and functional changes. These changes are a common feature in neurodegenerative diseases, including AD. The retina is considered an extension of the CNS and has a population of glial cells similar to that of the CNS. When glial cells are activated, various molecules are released and changes in glial cell expression occur, which can be indicators of neuronal damage. The objective of this review is to compile the most relevant findings in the last 10 years relating to alterations in the eye in AD, and the role that glial cells play in the degenerative process in the retina in the context of neurodegeneration.

Goniodysgenesis variability and activity of CYP1B1 genotypes in primary congenital glaucoma

Mutations in the CYP1B1 gene are currently the main known genetic cause of primary congenital glaucoma (PCG), a leading cause of blindness in children. Here, we analyze for the first time the CYP1B1 genotype activity and the microscopic and clinical phenotypes in human PCG. Surgical pieces from trabeculectomy from patients with PCG (n = 5) and sclerocorneal rims (n = 3) from cadaver donors were processed for transmission electron microscopy. Patients were classified into three groups depending on goniodysgenesis severity, which was influenced by CYP1B1 enzymatic activity. The main histological changes observed in the outflow pathway of patients with PCG and mutations in CYP1B1 were: i) underdeveloped collector channels and the Schlemm’s canal; ii) abnormal insertion of the ciliary muscle; iii) death of the trabecular endothelial cells. Our findings could be useful in improving treatment strategy of PCG associated with CYP1B1 mutations.

Neuroprotective Effects of Low-Dose Statins in the Retinal Ultrastructure of Hypercholesterolemic Rabbits

To evaluate the pleiotropic effects to statins, we analyze the qualitative and quantitative retinal changes in hypercholesterolemic rabbits after a low-dosage statin treatment. For this purpose, New Zealand rabbits were split into three groups: control (G0; n = 10), fed a standard diet; hypercholesterolemic (G1; n = 8), fed a 0.5% cholesterol-enriched diet for 8 months; and statins (G2; n = 8), fed a 0.5% cholesterol-enriched diet for 8 months, together with the administration of statin (pravastatin or fluvastatin sodium) at a dose of 2 mg / kg / day each diet. The retinas were analyzed by transmission electron microscopy and immunohistochemistry (glial fibrillary acidic protein). The retinal thickness of nuclear and plexiform layers were quantified in semi-thin sections. The results revealed that the low-statin-treated rabbits in comparison with the hypercholesterolemic group showed: i) a more preserved structure in all retinal layers; ii) a significant reduction in retinal thickness; iii) a decrease in cell death in the nuclear-and ganglion-cell layers; iv) a reduction of hydropic degeneration in the plexiform and nerve-fiber layers; v) a preservation of astrocytes and of the retinal area occupied by them; and vi) a better-preserved retinal vascular structure. Our findings indicate that low doses of statins can prevent retinal degeneration, acting on retinal macroglia, neurons and retinal vessels, despite that hypercholesterolemia remained unchanged. Thus, the pleiotropic effects of the statins may help safeguard the retinal ultrastructure.

Automatic Counting of Microglial Cells in Healthy and Glaucomatous Mouse Retinas

Proliferation of microglial cells has been considered a sign of glial activation and a hallmark of ongoing neurodegenerative diseases. Microglia activation is analyzed in animal models of different eye diseases. Numerous retinal samples are required for each of these studies to obtain relevant data of statistical significance. Because manual quantification of microglial cells is time consuming, the aim of this study was develop an algorithm for automatic identification of retinal microglia. Two groups of adult male Swiss mice were used: age-matched controls (naïve, n = 6) and mice subjected to unilateral laser-induced ocular hypertension (lasered; n = 9). In the latter group, both hypertensive eyes and contralateral untreated retinas were analyzed. Retinal whole mounts were immunostained with anti Iba-1 for detecting microglial cell populations. A new algorithm was developed in MATLAB for microglial quantification; it enabled the quantification of microglial cells in the inner and outer plexiform layers and evaluates the area of the retina occupied by Iba-1+ microglia in the nerve fiber-ganglion cell layer. The automatic method was applied to a set of 6,000 images. To validate the algorithm, mouse retinas were evaluated both manually and computationally; the program correctly assessed the number of cells (Pearson correlation R = 0.94 and R = 0.98 for the inner and outer plexiform layers respectively). Statistically significant differences in glial cell number were found between naïve, lasered eyes and contralateral eyes (P<0.05, naïve versus contralateral eyes; P<0.001, naïve versus lasered eyes and contralateral versus lasered eyes). The algorithm developed is a reliable and fast tool that can evaluate the number of microglial cells in naïve mouse retinas and in retinas exhibiting proliferation. The implementation of this new automatic method can enable faster quantification of microglial cells in retinal pathologies.

Macro- and microglial responses in the fellow eyes contralateral to glaucomatous eyes

Most studies employing experimental models of unilateral glaucoma have used the normotensive contralateral eye as the normal control. However, some studies have recently reported the activation of the retinal macroglia and microglia in the uninjured eye, suggesting that the eye contralateral to experimental glaucoma should not be used as a control. This review analyzes the studies describing the contralateral findings and discusses some of the routes through which the signals can reach the contralateral eye to initiate the glial reactivation.

Microglia in mouse retina contralateral to experimental glaucoma exhibit multiple signs of activation in all retinal layers

Background

Glaucomatous optic neuropathy, a leading cause of blindness, can progress despite control of intraocular pressure - currently the main risk factor and target for treatment. Glaucoma progression shares mechanisms with neurodegenerative disease, including microglia activation. In the present model of ocular hypertension (OHT), we have recently described morphological signs of retinal microglia activation and MHC-II upregulation in both the untreated contralateral eyes and OHT eyes. By using immunostaining, we sought to analyze and quantify additional signs of microglia activation and differences depending on the retinal layer.

Methods

Two groups of adult Swiss mice were used: age-matched control (naïve, n = 12), and lasered (n = 12). In the lasered animals, both OHT eyes and contralateral eyes were analyzed. Retinal whole-mounts were immunostained with antibodies against Iba-1, MHC-II, CD68, CD86, and Ym1. The Iba-1+ cell number in the plexiform layers (PL) and the photoreceptor outer segment (OS), Iba-1+ arbor area in the PL, and area of the retina occupied by Iba-1+ cells in the nerve fiber layer-ganglion cell layer (NFL-GCL) were quantified.

Results

The main findings in contralateral eyes and OHT eyes were: i) ameboid microglia in the NFL-GCL and OS; ii) the retraction of processes in all retinal layers; iii) a higher level of branching in PL and in the OS; iv) soma displacement to the nearest cell layers in the PL and OS; v) the reorientation of processes in the OS; vi) MHC-II upregulation in all retinal layers; vii) increased CD68 immunostaining; and viii) CD86 immunolabeling in ameboid cells. In comparison with the control group, a significant increase in the microglial number in the PL, OS, and in the area occupied by Iba-1+ cells in the NFL-GCL, and significant reduction of the arbor area in the PL. In addition, rounded Iba-1+ CD86+ cells in the NFL-GCL, OS and Ym1+ cells, and rod-like microglia in the NFL-GCL were restricted to OHT eyes.

Conclusions

Several quantitative and qualitative signs of microglia activation are detected both in the contralateral and OHT eyes. Such activation extended beyond the GCL, involving all retinal layers. Differences between the two eyes could help to elucidate glaucoma pathophysiology.

Rod-like microglia are restricted to eyes with laser-induced ocular hypertension but absent from the microglial changes in the contralateral untreated eye

In the mouse model of unilateral laser-induced ocular hypertension (OHT) the microglia in both the treated and the normotensive untreated contralateral eye have morphological signs of activation and up-regulation of MHC-II expression in comparison with naïve. In the brain, rod-like microglia align to less-injured neurons in an effort to limit damage. We investigate whether: i) microglial activation is secondary to laser injury or to a higher IOP and; ii) the presence of rod-like microglia is related to OHT. Three groups of mice were used: age-matched control (naïve, n=15); and two lasered: limbal (OHT, n=15); and non-draining portion of the sclera (scleral, n=3). In the lasered animals, treated eyes as well as contralateral eyes were analysed. Retinal whole-mounts were immunostained with antibodies against, Iba-1, NF-200, MHC-II, CD86, CD68 and Ym1. In the scleral group (normal ocular pressure) no microglial signs of activation were found. Similarly to naïve eyes, OHT-eyes and their contralateral eyes had ramified microglia in the nerve-fibre layer related to the blood vessel. However, only eyes with OHT had rod-like microglia that aligned end-to-end, coupling to form trains of multiple cells running parallel to axons in the retinal surface. Rod-like microglia were CD68+ and were related to retinal ganglion cells (RGCs) showing signs of degeneration (NF-200+RGCs). Although MHC-II expression was up-regulated in the microglia of the NFL both in OHT-eyes and their contralateral eyes, no expression of CD86 and Ym1 was detected in ramified or in rod-like microglia. After 15 days of unilateral lasering of the limbal and the non-draining portion of the sclera, activated microglia was restricted to OHT-eyes and their contralateral eyes. However, rod-like microglia were restricted to eyes with OHT and degenerated NF-200+RGCs and were absent from their contralateral eyes. Thus, rod-like microglia seem be related to the neurodegeneration associated with HTO.

"Super p53" mice display retinal astroglial changes

Tumour-suppressor genes, such as the p53 gene, produce proteins that inhibit cell division under adverse conditions, as in the case of DNA damage, radiation, hypoxia, or oxidative stress (OS). The p53 gene can arrest proliferation and trigger death by apoptosis subsequent to several factors. In astrocytes, p53 promotes cell-cycle arrest and is involved in oxidative stress-mediated astrocyte cell death. Increasingly, astrocytic p53 is proving fundamental in orchestrating neurodegenerative disease pathogenesis. In terms of ocular disease, p53 may play a role in hypoxia due to ischaemia and may be involved in the retinal response to oxidative stress (OS). We studied the influence of the p53 gene in the structural and quantitative characteristics of astrocytes in the retina. Adult mice of the C57BL/6 strain (12 months old) were distributed into two groups: 1) mice with two extra copies of p53 (“super p53”; n = 6) and 2) wild-type p53 age-matched control, as the control group (WT; n = 6). Retinas from each group were immunohistochemically processed to locate the glial fibrillary acidic protein (GFAP). GFAP+ astrocytes were manually counted and the mean area occupied for one astrocyte was quantified. Retinal-astrocyte distribution followed established patterns; however, morphological changes were seen through the retinas in relation to p53 availability. The mean GFAP+ area occupied by one astrocyte in “super p53” eyes was significantly higher (p<0.05; Student’s t-test) than in the WT. In addition, astroglial density was significantly higher in the “super p53” retinas than in the WT ones, both in the whole-retina (p<0,01 Student’s t-test) and in the intermediate and peripheral concentric areas of the retina (p<0.05 Student’s t-test). This fact might improve the resistance of the retinal cells against OS and its downstream signalling pathways.

IOP induces upregulation of GFAP and MHC-II and microglia reactivity in mice retina contralateral to experimental glaucoma

Background

Ocular hypertension is a major risk factor for glaucoma, a neurodegenerative disease characterized by an irreversible decrease in ganglion cells and their axons. Macroglial and microglial cells appear to play an important role in the pathogenic mechanisms of the disease. Here, we study the effects of laser-induced ocular hypertension (OHT) in the macroglia, microglia and retinal ganglion cells (RGCs) of eyes with OHT (OHT-eyes) and contralateral eyes two weeks after lasering.

Methods

Two groups of adult Swiss mice were used: age-matched control (naïve, n = 9); and lasered (n = 9). In the lasered animals, both OHT-eyes and contralateral eyes were analyzed. Retinal whole-mounts were immunostained with antibodies against glial fibrillary acid protein (GFAP), neurofilament of 200kD (NF-200), ionized calcium binding adaptor molecule (Iba-1) and major histocompatibility complex class II molecule (MHC-II). The GFAP-labeled retinal area (GFAP-RA), the intensity of GFAP immunoreaction (GFAP-IR), and the number of astrocytes and NF-200 + RGCs were quantified.

Results

In comparison with naïve: i) astrocytes were more robust in contralateral eyes. In OHT-eyes, the astrocyte population was not homogeneous, given that astrocytes displaying only primary processes coexisted with astrocytes in which primary and secondary processes could be recognized, the former having less intense GFAP-IR (P < 0.001); ii) GFAP-RA was increased in contralateral (P <0.05) and decreased in OHT-eyes (P <0.001); iii) the mean intensity of GFAP-IR was higher in OHT-eyes (P < 0.01), and the percentage of the retinal area occupied by GFAP+ cells with higher intensity levels was increased in contralateral (P = 0.05) and in OHT-eyes (P < 0.01); iv) both in contralateral and in OHT-eyes, GFAP was upregulated in Müller cells and microglia was activated; v) MHC-II was upregulated on macroglia and microglia. In microglia, it was similarly expressed in contralateral and OHT-eyes. By contrast, in macroglia, MHC-II upregulation was observed mainly in astrocytes in contralateral eyes and in Müller cells in OHT-eyes; vi) NF-200+RGCs (degenerated cells) appeared in OHT-eyes with a trend for the GFAP-RA to decrease and for the NF-200+RGC number to increase from the center to the periphery (r = −0.45).

Conclusion

The use of the contralateral eye as an internal control in experimental induction of unilateral IOP should be reconsidered. The gliotic behavior in contralateral eyes could be related to the immune response. The absence of NF-200+RGCs (sign of RGC degeneration) leads us to postulate that the MHC-II upregulation in contralateral eyes could favor neuroprotection.

Low-dosage statins reduce choroidal damage in hypercholesterolemic rabbits

PURPOSE

To describe the ultrastructural changes in the choroid of long-term hypercholesterolemic rabbits after a low-dosage statin treatment and to evaluate some pleiotropic effects of these drugs on the morphology of endothelial cells (EC) and vascular smooth-muscle cells (VSMC).

METHODS

New Zealand rabbits were divided into three groups: G0, fed a standard diet; G1, fed a 0.5% cholesterol-enriched diet for 8 months and G2, fed a 0.5% cholesterol-enriched diet for 8 months plus administration of fluvastatin sodium or pravastatin sodium at a dose of 2 mg/Kg/day each. Eyes were processed for transmission-electron microscopy.

RESULTS

G1 had a lipid build-up at the suprachoroidea that compressed the vascular layers with the lumens of the vessels to the point of collapse in some instances. By contrast, G2 underwent a substantial decrease in suprachoroidal foam cells and of lipids in the vascular layers while the vascular lumens were normal. The preservation of cytoplasmic organelles, caveolar system and other ultrastructural features of EC and VSMC in G2 contrasted with the numerous signs of necrosis observed in G1. Bruch's membrane (BM) in G2 contained fewer lipids and more collagen than in G1.

CONCLUSION

Treatment with a low dosage of fluvastatin sodium or pravastatin sodium reduced the lipid build-up as well as the macrophages in the choroid and restored the vascular lumens of choroidal vessels independently of the cholesterol effect. The normal ultrastructural features of choroidal EC and VSMC in statin-treated animals suggest that the endothelial function is preserved and the ischaemia reduced.

Quantification of the effect of different levels of IOP in the astroglia of the rat retina ipsilateral and contralateral to experimental glaucoma

PURPOSE

To analyze the effects of different levels of intraocular pressure (IOP) in the macroglia in ocular hypertension (OHT) and contralateral eyes at 3 weeks after laser photocoagulation and compare these with effects in age-matched control rats.

METHODS

Adult Sprague-Dawley rats were divided into an age-matched control (naive) group and an OHT group. Retinas were processed as whole mounts and immunostained with GFAP for analysis of the retinal macroglia.

RESULTS

The area of the retina occupied by astrocytes (AROA) was quantified. GFAP immunostaining showed common features in ipsilateral and contralateral eyes. First, although the astrocyte network maintained a star-shaped morphology, these cells had fewer secondary processes and thinner cell bodies and primary processes than did naive cells. Second, Müller cells appeared as punctate GFAP+ structures among astrocytes. Third, there was a significant reduction of the AROA in ipsilateral and contralateral eyes compared with naive eyes. Ipsilateral eyes had significantly less AROA than did contralateral eyes. The decrease was greater for OHT eyes with higher IOP levels.

CONCLUSIONS

OHT induces changes in the macroglia of contralateral eyes; thus, these fellow eyes should not be used as control. In eyes with OHT, there is a close relationship between IOP values and decreased AROA.

Vimentin isoform expression in the human retina characterized with the monoclonal antibody 3CB2

The antigen recognized by the monoclonal antibody 3CB2 (3CB2-Ag and 3CB2 mAb) is expressed by radial glia and astrocytes in the developing and adult vertebrate central nervous system (CNS) of vertebrates as well as in neural stem cells. Here we identified the 3CB2-Ag as vimentin by proteomic analysis of human glial cell line U-87 extracts (derived from a malignant astrocytoma). Indeed, the 3CB2 mAb recognized three vimentin isoforms in glial cell lines. In the human retina, 3CB2-Ag was expressed in Müller cells, astrocytes, some blood vessels, and cells in the horizontal cell layer, as determined by immunoprecipitation and immunofluorescence. Three populations of astrocytes were distinguishable by double-labeling immunohistochemistry: vimentin+/GFAP+, vimentin-/GFAP+, and vimentin+/GFAP-. Hence, we conclude that 1) the 3CB2-Ag is vimentin; 2) vimentin isoforms are differentially expressed in normal and transformed astrocytes; 3) human retinal astrocytes display molecular heterogeneity; and 4) the 3CB2 mAb is a valuable tool to study vimentin expression and its function in the human retina.

Substance P and calcitonin gene-related peptide intrinsic choroidal neurons in human choroidal whole-mounts

To determine the presence in the human choroid of substance P (SP)-and calcitonin gene-related peptide (CGRP) positive intrinsic choroidal neurons (ICNs), choroidal whole-mounts were processed for indirect immunofluorescence. An antibody to a component of the neuronal cytoskeleton, neurofilament 200 kDa (NF-200), was combined with antibodies to SP and to CGRP (neuropeptides proper to the sensory nervous system). The human choroid possesses numerous SP(+) and CGRP(+) ICNs. These neurons were observed in the suprachoroid, both in isolation and forming microganglia. For both types of ICNs studied, neurons were more numerous in the temporal than in the nasal regions. In both locations, SP(+) and CGRP(+) ICNs were more abundant in the central choroid (the choroid underneath the macular area of the retina), with cell density diminishing outwards to the choroidal periphery. There were no appreciable differences between the two populations of ICNs studied in terms of size, morphology or immunostaining characteristics. In conclusion, given that peripheral sensory innervation could be involved in the regulation of both choroidal blood flow and vascular architecture, the SP(+) and CGRP(+) ICNs described for the first time in the present work may be involved in these mechanisms of vascular regulation.

Alterations in the choroid in hypercholesterolemic rabbits: reversibility after normalization of cholesterol levels

Endothelial damage in atherosclerosis is characterized by abnormal vascular functionality. Hyperlipidemic patients show alterations in ocular vascularization. However, it is not known whether these alterations are reversible after the lipid profile returns to normal. This study evaluates a rabbit model of hypercholesterolemia, examining the ultrastructural changes in the choroid, and the changes in it after a period of normal blood-cholesterol values induced by a standard diet. Rabbits were divided into three groups: G0, fed a standard diet; G1A, fed a 0.5% cholesterol-enriched diet for 8 months; and G1B, fed a 0.5% cholesterol-enriched diet for 8 months followed by a standard diet for a further 6 months. Eyes were processed for transmission electron microscopy. G1A had a buildup of lipids at the suprachoroidea that compressed the vascular layers, and hypertrophy of endothelial and vascular smooth muscle cells. In G1B there was less lipid accumulation than in G1A, but this was not followed by reversal of the choroidal damage. The suprachoroidea thickness of G1B was still greater than in G0 due to abundant collagen fibers. The intervascular spaces of the choroid had fewer lipids than G1A but more collagen fibers than G0. The large- and medium-sized vessel layers and choriocapillaris were less compressed than in G1A but exhibited basal membrane and endothelial changes similar to those in G1A. Normalization of serum cholesterol levels is not enough to reverse cholesterol-induced vascular damage to the choroid. These choroidal changes could be compatible with a chronic ischemia that could produce retinal degeneration.

Macroglial and retinal changes in hypercholesterolemic rabbits after normalization of cholesterol levels

This study evaluates hypercholesterolemic rabbits, examining the retinal changes in Müller cells and astrocytes as well as their variations after a period of normal blood-cholesterol values induced by a standard diet. New Zealand rabbits were divided into three groups: G0, fed a standard diet; G1A, fed a 0.5% cholesterol-enriched diet for 8 months; and G1B, fed as G1A followed by standard diet for 6 months. Eyes were processed for transmission electron microscopy and immunohistochemistry (GFAP). While G1B resembled G0 more than did G1A, they shared alterations with G1A: a) as in G1A, Müller cells were GFAP+, filled spaces left by axonal degeneration, formed glial scars and their nuclei were displaced to the nerve-fibre layer. The area occupied by the astrocytes associated with the nerve-fibre bundles (AANFB) and by perivascular astrocytes (PVA) in G1A and G1B was significantly lower than in controls. However, no significant differences in PVA were found between G1A and G1B. In G1B, type I PVA was absent and replaced by hypertrophic type II cells; b) Bruch's membrane (BM) was thinner in G1B than in G1A; c) the retinal pigment epithelium (RPE) cytoplasm contained fewer lipids in G1B than in G1A; d) in G1A and G1B choriocapillaris and retinal vessel showed alterations with respect to G0; e) cell death and axonal degeneration in the retina were similar in G1A and G1B. The substitution of a hyperlipemic diet by a standard one normalizes blood-lipid levels. However, the persistence of damage at retinal vessels and BM-RPE could trigger chronic ischemia.

[Structural changes of the anterior chamber angle in primary congenital glaucoma with respect to normal development]

PURPOSE

To compare findings of normal angles with those from primary congenital glaucoma in order to clarify the pathogenic mechanisms of the disease and to explain the success of surgical treatment in some of these patients.

METHODS

Adult normal eyes from cadavers and fragments of surgical trabeculectomies from patients with primary congenital glaucoma previously treated with goniotomy were studied. Eyes were processed for examination using light microscopy and scanning electron microscopy techniques.

RESULTS

The following was evident in congenital glaucoma: 1) high iris insertion; 2) no observable pre-trabecular membrane, but enlarged trabeculae with diminished inter-trabecular spaces; 3) Schlemm's canal (SC) apparently normal, with vacuoles in the wall indicating normal functioning; 4) sectioning of the abnormal trabecular tissue during goniotomy allowed repositioning of the angle structures and hence the appearance of the angular recess.

CONCLUSIONS

Anomalies of the trabecular structures in primary congenital glaucoma do not always parallel an abnormal development of the SC and the collector channels. This fact could explain the success of goniotomy in this type of glaucoma.

[A comparative study of choroidal innervation in the human and the rabbit (oryctolagus cuniculus)]

OBJECTIVE

To analyze morphological differences between the choroidal innervation of the human and the rabbit, the latter being a species frequently used as an experimental model of human ocular diseases.

METHODS

Twelve human and 12 rabbit choroidal whole mounts were processed using an indirect immunohistochemical technique, peroxidase-anti-peroxidase and antibodies against 200 kD neurofilament.

RESULTS

Choroidal nerve fibers were perivascular and intervascular. Perivascular fibers surrounded all arteries forming a network that was more developed in the rabbit. In humans, intervascular fibers were mainly concentrated at the posterior pole where they formed a denser and more highly organized plexus than in the rabbit, which did not exhibit a preferential location for these fibers. Human choroidal ganglion cells were far more numerous than in the rabbit and were concentrated in a circumferential area corresponding to the entrance of the short posterior ciliary arteries of the submacular area. In the rabbit, these cells were restricted to the peripheral choroid.

CONCLUSIONS

Some differences were observed between human and rabbit choroidal innervation. The abundance of ganglion cells and their preferential distribution could be necessary to maintain a constant blood flow in the central area of the human choroid. The lack of organization of rabbit choroidal innervation at the posterior pole could be associated with an absence of the macula. These differences, along with peculiarities of retinal vascularization, should be taken into consideration when using the rabbit as an experimental model to study human eye diseases in which regulation of choroidal blood flow is involved.

A cholesterol-enriched diet induces ultrastructural changes in retinal and macroglial rabbit cells

The purpose of this study was to ascertain whether the excess of cholesterol in rabbits induces ultrastructural retinal changes similar to those observed in human age-related macular degeneration (AMD). New Zealand rabbits were divided into two groups: Control (GO; n=10), fed standard diet for 8 months; hypercholesterolemic (G1; n=10), fed with 0.5% cholesterol-enriched diet for 8 months. Eyes were processed for transmission electron microscopy (TEM) and immunohistochemistry (anti-glial fibrillary acidic protein, GPAP). In comparison with GO, G1 exhibited alterations in all the retinal layers that were more intense in areas overlying altered retinal pigment epithelium (RPE). RPE changes showed no preferential location. In G1, Bruch's membrane was thicker as a result particle build-up in the collagen layers; the cytoplasm of RPE showed dense bodies, debris from cell membranes, vacuoles and numerous clumps of lipids; necrosis and apoptosis were detected in different retinal layers; Müller cells and astrocytes were reactive with instances of apoptosis and necrosis; some Müller cells filled up the empty spaces left by degenerated neurons in all retinal layers; some Müller cell nuclei were displaced to the nerve-fiber layer (NFL); epiretinal perivascular astrocytes contained drops of lipids; the NFL had very few astrocytes and the basal membranes of capillaries in the NFL was thicker. Excess cholesterol induces ultrastructural changes in the rabbit retina similar to those in human AMD. Given that lipid intake is most dependent on food composition, dietary regimen could help induce or prevent retinal disease.