Biomedical subjects

T L van der Schaft

Publications and source records attributed to T L van der Schaft.

10 recordsLinked to original sources

PubMed1997

Morphologic changes in age-related maculopathy.

Age-related maculopathy (ARM) is a degenerative disorder of the central part of the retina with a rising prevalence in patients 50 years of age and older, and comprises different histopathological changes. The morphologic changes in ARM are described and illustrated with light-microscopical, electron microscopical, and fundus pictures. Furthermore, the most important biochemical data are given. The most prominent aging changes in early stages of ARM are drusen and basal laminar deposit (BLD), both extracellular deposits, that are assumed to be important in the development of ARM. Drusen accumulate within Bruch's membrane, whereas BLD is present between Bruch's membrane and the retinal pigment epithelium. Although the histopathologic characteristics of the deposits are well documented, the chemical composition has only been partly resolved. Biochemical analysis of these deposits is necessary to determine the source of the deposits and to find possible ways to avoid or treat them. The late stages of ARM, geographic atrophy, and neovascular (disciform) degeneration, are called age-related macular degeneration (AMD), and result in severe and irreversible visual impairment. Since there is still no adequate therapy for the majority of people disabled by AMD, and because of the aging population resulting in even more patients with this disease, it is necessary to intensify the research on ARM in order to prevent AMD or find a therapy for it.

Basement Membrane↗

PubMed1994

Immunohistochemical light and electron microscopy of basal laminar deposit.

The formation of basal laminar deposit (BLD) is one of the histopathologic changes in the aging human macula. BLD is assumed to be an early stage of age-related macular degeneration. The location of BLD, between the RPE plasma membrane and its basement membrane and in the outer collagenous zone of Bruch's membrane, and its ultrastructure suggest that it is composed of excessive amounts of basement membrane material. The main components of basement membranes are type IV collagen, heparan sulfate proteoglycans (HSPG) and laminin. Labeled antibodies against these components can therefore be used for the identification and localization of basement membrane material by means of immunohistochemical techniques. In this study the presence of type IV collagen, laminin and HSPG was determined in aged human maculae by immunohistochemistry and immunoelectron microscopy. Tests for the presence of type VI collagen and fibronectin were also performed. We obtained 76 eyes from 68 human subjects at autopsy or after surgical enucleation for anteriorly located choroidal melanomas. The finely granular component of BLD stained positive with antibodies against type IV collagen, HSPG and laminin, but the long-spacing collagen component of BLD did not. Neither component of BLD was stained with antibodies against type VI collagen or fibronectin. We conclude that BLD consists partly of excess basement membrane material.

Adult↗

PubMed1994

Increased prevalence of disciform macular degeneration after cataract extraction with implantation of an intraocular lens.

After cataract extraction with implantation of an intraocular lens the increased transmission of ultraviolet and blue light may accelerate the development of age-related macular degeneration by producing free radicals in the retina. The maculae of 82 randomly selected postmortem human pseudophakic eyes and 16 fellow phakic eyes were examined by light microscopy. The presence of a basal laminar deposit, hard and soft drusen, thickening and calcification of Bruch's membrane, geographic atrophy, subretinal neovascularisation, and disciform scars was assessed in a standardised way. An age-matched series of 126 postmortem phakic eyes was used as control group. There was no difference between the two groups, except for a higher prevalence of hard drusen (exact trend test, p = 0.038) and disciform scars for the pseudophakic eyes (Fisher's exact test, p = 0.007). There was no significant correlation between either age-related changes in the macula or disciform degeneration and the length of time between cataract surgery and death. No significant difference was found between pseudophakic eyes with or without ultraviolet filter. These findings do not confirm that disciform scar formation is caused by an increase in ultraviolet or blue light.

Age Distribution↗

PubMed1994

Morphometric analysis of Bruch's membrane, the choriocapillaris, and the choroid in aging.

PURPOSE: To quantify changes in choriocapillary density and in thickness of Bruch's membrane, the choriocapillaris, and the choroid in 95 unpaired, histologically normal human maculae aged 6 to 100 years and in 25 maculae with advanced age-related macular degeneration. METHODS: Light microscopic, computer-aided, morphometric quantitative analysis. RESULTS: In ten decades, Bruch's membrane thickness increased by 135%, from 2.0 to 4.7 microns; the choriocapillary density decreased by 45%; the diameter of the choriocapillaris decreased by 34%, from 9.8 to 6.5 microns; and the choroidal thickness decreased by 57%, from 193.5 to 84 microns in normal maculae. In maculae with basal laminar deposit, geographic atrophy, or disciform scarring, the density of the choriocapillaris was 63%, 54%, and 43% of normal and the choriocapillary diameter was 81%, 73%, and 75% of normal, respectively. Choroidal thickness remained unchanged. CONCLUSIONS: Thickness of Bruch's membrane was only related to age (rs = 0.63) and not to age-related atrophy of the choriocapillaris. Age was also the strongest factor related to choriocapillary density (rs = -0.58). In advanced stages of age-related macular degeneration, the decrease in choriocapillary density and diameter was significantly larger than in normal maculae, but the thickness of the choroid and Bruch's membrane was the same. The latter was significantly thinner (81% of normal) in disciform scarring.

Adolescent↗

PubMed1993

Basal laminar deposit in the aging peripheral human retina.

A basal laminar deposit (BLD) in the human macula has been described as an early sign of age-related macular degeneration. In some eyes with a BLD in the macula, light microscopic sections of the peripheral retina revealed almost similar deposits between the retinal pigment epithelium and Bruch's membrane. Because the exact pathogenesis of age-related macular degeneration and the origin of the BLD are unknown, we studied the ultrastructure of these peripheral sub-RPE deposits. Parts of the equatorial and peripheral regions of the retina of ten human eyes, with BLD-like deposits between the retinal pigment epithelium and Bruch's membrane, were examined by electron microscopy. In eight of these ten eyes the ultrastructure of these deposits was amorphous and finely granular. Five of the eight deposits also contained small amounts of long-spacing collagen. Ultrastructurally, the deposits were similar to an early type BLD in the macula. In the remaining two eyes, the deposits appeared to consist of flat, elongated drusen. Our findings indicate that a BLD can develop not only in the macula but also in the peripheral region of the retina.

Aged↗

PubMed1993

Early stages of age-related macular degeneration: an immunofluorescence and electron microscopy study.

In subretinal neovascularisation capillaries originating from the choriocapillaris must cross Bruch's membrane to reach the subretinal pigment epithelial space. Thus gaps in Bruch's membrane have to be formed before subretinal neovascularisation. Histological examination of eyes with subretinal neovascularisation or disciform scars has shown macrophages adjacent to thin areas and ruptures in Bruch's membrane. This has been interpreted as phagocytosis of Bruch's membrane. The purpose of this study was to investigate whether immune complex depositions can be detected in maculae with early stages of age-related macular degeneration and to explain the macrophage reaction before the disciform reaction. A series of 20 human maculae were examined by direct immunofluorescence light microscopy to detect the presence of immune complexes with antibodies directed against immunoglobulins, fibrinogen, and complement factors. Transmission electron microscopy on several maculae was performed to identify the macrophages. Macrophages were observed in close relation to the readily recognisable long spacing collagen, which suggested that long spacing collagen was selectively internalised by these cells. Definite immune complex depositions were not found in basal laminar deposits or drusen. Linear deposits of fibrinogen and complement were frequently found in the outer collagenous zone of Bruch's membrane. However, because of the absence of immunoglobulins, it seems unlikely that these non-specific deposits might cause chemoattraction of macrophages and play a role in the initial phase of the development of subretinal neovascularisation and disciform macular degeneration.

Adult↗

PubMed1992

Element analysis of the early stages of age-related macular degeneration.

The accumulation of basal laminar deposit (BLD) in the macula is considered to be a precursor of age-related macular degeneration. To learn more about the composition of BLD and the role of zinc in age-related macular degeneration, we investigated the elements in BLD, as well as in surrounding structures in 38 postmortem human maculae by electron-probe x-ray microanalysis. Basal laminar deposit and capillary vessel walls of the choriocapillaris appeared to contain no typical elements. Calcium, phosphorus, sulfur, zinc, and chlorine were detected in the lipofuscin granules in retinal pigment epithelium. Pigment granules of the retinal pigment epithelium and choroidal melanocytes contained predominantly sulfur and copper and, to a lesser degree, zinc, calcium, and iron. Local calcifications in Bruch's membrane were composed of large amounts of calcium and phosphorus and smaller amounts of zinc, iron, and chlorine. Metal-mirror fixation of the maculae, followed by freeze-drying and vapor fixation, showed additional amounts of sodium and potassium. From these experiments, no conclusions could be drawn about the origin of BLD. No relationship was found between the detection of zinc and the presence of BLD or drusen in the macula.

Adolescent↗

PubMed1992

Histologic features of the early stages of age-related macular degeneration. A statistical analysis.

The age distribution, frequency, and correlation among histologic macular changes, including formation of a basal laminar deposit, drusen, and thickening and calcification of Bruch's membrane, were studied by light microscopy. The authors studied 182 unpaired postmortem human maculae from patients between 8 and 100 years of age. In addition, 45 maculae of contralateral eyes and the peripheral retina of 50 eyes were studied. In 92%, Bruch's membrane was thickened starting at age 19, and calcifications in this membrane were found in 59% starting at age 33. In 37% of the maculae, hard drusen were found starting at age 34. Soft drusen were found in 10% beginning at age 54. Basal laminar deposit was found in 39% of the maculae starting at age 40. All changes correlated strongly with age (P less than 0.0001). No sex differences were found. Fellow eyes showed similar aging changes (P less than 0.001). The presence of basal laminar deposit in the macula correlated with basal laminar deposit-like material in the peripheral retina (correlation coefficient, 0.39; P less than 0.003), whereas drusen in the macula correlated with drusen in the peripheral retina (correlation coefficient, 0.42; P = 0.001). Geographic atrophy was found in 6.6% of the eyes from subjects older than 70 years and subretinal neovascularization in 3.8%, especially in the maculae with basal laminar deposit.

Adolescent↗

PubMed1991

Is basal laminar deposit unique for age-related macular degeneration?

The ultrastructural nature and distribution of basal laminar deposit, considered to be a precursor of age-related macular degeneration, were studied in 42 human maculae. Basal laminar deposit was found from age 19 years on, not only between the retinal pigment epithelial cells and their basement membrane but also more often on the choriocapillary side of Bruch's membrane. No direct relationship was found with other aging changes, such as calcifications in Bruch's membrane, accumulation of lipofuscin granules, or drusen in the macular area. Material similar to basal laminar deposit can be found in the trabecular system, in the cornea, and also in many other organs and tissues. On a structural and morphometrical basis, we think that basal laminar deposit is similar to fibrous long-spacing collagen and thus does not seem to be a purely ocular abnormality.

Adolescent↗

PubMed1989

Results of penetrating keratoplasty for pseudophakic bullous keratopathy with the exchange of an intraocular lens.

We report on 29 consecutive patients with pseudophakic bullous keratopathy who underwent in one eye penetrating keratoplasty with an exchange of the original intraocular lens for a Pearce tripod posterior chamber lens, and who were available for a follow up of at least 12 months. The average interval between cataract extraction with lens implantation and the appearance of bullous keratopathy was five and a half years (range 10 months to 16 years). The mean follow-up period after penetrating keratoplasty was 36 months (range 12 to 56 months). The corneal graft remained clear in 22 (76%) eyes. One year after the operation 45% of the eyes had a vision of 20/40 or better, and 20% had visual acuities between 20/40 and 20/100. The remaining 31% had a vision of 20/100 or less (one unknown). Nine eyes (31%) had cystoid macular oedema or macular degeneration. 45% of the eyes had a refraction within approximately 2 dioptres of emmetropia. In patients with pseudophakic corneal oedema we continue to exchange the intraocular lens by a Pearce tripod posterior chamber lens sutured to the iris when it is necessary to remove the lens.

Aged↗