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Scanning electron microscopy of vitrectomy material shows a disintegrated vitreous fibril network which is partly replaced by newly formed collagen fibers and invaded cells.
The vitreous contains collagen and soluble non-collagen proteins. The degeneration of collagen takes place in a different manner than in the other proteins. It has been detected that the cattle vitreous does not show any collagenolytic activity against the basic types of collagen (I, II, IX, and XI). The vitreous digests haemoglobin only in the acidic section of pH (optimum 3.5-4.5). No proteolytic activity towards Hb in physiological pH has been found.
The vitreous is feebly antigenic and is characterized by the absence of gamma-globulins and immunocompetent cells. Moreover, it is isolated from the aqueous humour by a mucopolysaccharide molecular filter. It represents an incomplete and primitive immunological system, reacting like an embryonic tissue and exhibiting only phagocytosis.
The rheological properties of the vitreous body of the eye are believed to be a function of composition and to differ among species, as well as to vary regionally within the vitreous. These properties are essential to the mechanical functioning of the eye. Although there are gross, qualitative data on vitreous rheology available in the literature, quantitative rheological measurements on human vitreous and on eyes of other species are sparse and incomplete. The aim of the research reported in this series of papers is to study the rheological behavior of human, bovine, and porcine vitreous, to measure the macromolecular and electrolyte content of these samples, and to correlate and compare these values for the different species as a function of location in the vitreous. In this paper, the rheological model used to correlate viscoelasticity of the vitreous is presented, and a detailed description of the rheological instrumentation and methods of analysis used is given. Data on the rheological properties of human vitreous, as a function of location within the eye, are presented. The results show that in the human eye there are significant differences in a number of the viscoelastic parameters as a function of location within the vitreous body.
The vitreous body of both the healthy and the affected eyes of 25 patients suffering from unilateral acute anterior uveitis was examined by ultrasound, and the results were compared with the optical observations made on the affected eye. In 14 eyes the optical examination of the vitreous body was impossible either due to exudation in the anterior chamber or to posterior synechias of the iris or to cataract. In 17 eyes the vitreous body was acoustically highly inhomogeneous, in three eyes slightly inhomogeneous and in five eyes no acoustic changes due to exudation were found. In cases of acute anterior uveitis, ultrasound examination often provides more information than optical examination by slit lamp. Ultrasound can also be useful in the treatment and follow-up of the disease.
The effect of age on degeneration of the vitreous body was studied in 77 patients and in 123 eyes. The patients were divided into three groups by age, with a mean age of 16, 35 and 72 years, respectively. In the two younger groups the vitreous body generally appeared to be acoustically homogeneous, while the oldest group showed heterogeneity of the vitreous body in a majority of cases. Syneresis of the vitreous body yielded a highly characteristic echogram. A total of 22 eyes with unilateral idiopathic detachment of the retina were examined, and in all of them degeneration of the vitreous body was clearly detected. Examination of the other, "normal" eye revealed only four eyes with an acoustically homogeneous vitreous body. Six patients had severe syneresis in bthe eyes. The evident conclusion is that detachment of the retina even in a single eye is often accompanied by degeneration of the vitreous body in the other eye as well.
Vitreous body fibrils and zonula fibers are analyzed by disc-electrophoresis. In both tissues the presence of collagen is established. The disc-electrophoresis patterns of vitreous body fibrils and zonula fibers show that a different type of collagen is present in each tissue. The absence of the alpha 2-chain indicates that the tissues investigated contain no type I collagen but types consisting of three identical alpha-chains.
Amyloidosis of the vitreous body is an uncommon and often misdiagnosed condition that causes progressive visual loss. It is usually associated with primary familial systemic amyloidosis. The patient described in this report has amyloidosis of both vitreous bodies; her case is unusual because no other family members are affected and because there has been no evidence of systemic involvement over a seven-year observation period. After part of the vitreous body of her right eye was removed surgically, visual acuity improved from light perception to 20/60. New concepts regarding the nature, classification, and histochemical identification of amyloid are discussed.
Two different cells types have been shown to synthesize embryonic chick vitreous collagen (vitrosin) at different stages of development. Identification of vitrosin was established by labeling the embryos in ovo [3H]proline at stages 23 and 28 and separating the extracted vitreous collagen alpha-chains by carboxymethylcellulose chromatography. The labeled collagen consisted predominately of alpha 1 chains, indicating a molecule in the form of a trimer of identical chains designated (alpha 1)3. The molecular weight of the labeled chains measured approximately 95,000 daltons by molecular sieve chromatography, and contained 41% of their imino acid as 4-hydroxyproline. To establish which eye tissues synthesize vitrosine, the collagens produced in organ culture by the isolated neural retina, lens and vitreous body from stages 26-27, 29-30, and 40 were examined. At the two earlier stages, only the neural retina synthesized large quantities of (alpha 1)3 collagen whereas the lens and the cells within the vitreous body itself synthesized relatively small amounts of collagen characterized by an alpha 1:alpha 2 ratio of about 2:1. At stage 40, however, the cells of the vitreous body itself synthesized the greatest quantities of collagen, which now was predominantly an (alpha 1)3 type molecule. Stage 40 neural retina and lens synthesized lesser amounts of collagen with an alpha 1:alpha 2 ratio of 2 to 3:1. Chick vitrosin thus appears to be synthesized by the neural retina in early embryonic stages, whereas the major contribution derives from cells within the vitreous body in later development.
From pepsin-solubilized vitreous body collagen three different precipitates were collected by differential salt precipitation. These three different protein fractions contain hydroxyproline and show different patterns in polyacrylamide gel electrophoresis suggesting different collagen types.
In the isolated unfixed vitreous body a structural organization can be visualized by slitlamp microscopy or by an ink-injection technique. We discuss the observations on human and rhesus monkey (Macaca mulatta) vitreous bodies using the ink-injection technique. Advantages and disadvantages of this method compared with slitlamp microscopy are described. Eventual functional implications of vitreal organization are mentioned briefly.
A total of 444 healthy eyes in 290 subjects of varying age were examined ultrasonically with a frequency of 6 MHz. In subjects under 20 years the structure of the vitreous body was acoustically homogeneous, and in those between 21 and 40 there was slight degeneration in 5% of the eyes. In the age group 41-50 the incidence of degeneration was 19%, in the group 51-60 63% and in that over 60 more than 80%. There was a clear increase in acoustically observable degeneration after the 40th year; nevertheless, in about 10% of those over 60 years an acoustically homogeneous vitreous body was observed. Ultrasonic observation can be used to supplement optical observations, and in the case of elderly patients is often the only way of obtaining information on the structure of the vitreous body.
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Persistent hyperplastic primary vitreous is a disease whose spectrum has continued to widen throughout the years; in fact, it probably comprises a number of nosological entities considered as isolated symptoms until today. Our study has shown that the disease can be congenital and affect both eyes in the same individual. The possibility of an etiopathogenic connection with retrolental fibroplasia cannot be excluded.
The structure of the vitreous body and the retinal periphery have been examined in 180 eyes after the use of different extraction methods of the lens. The smallest changes have been observed after cryoextraction without alpha-chymotrypsine. The investigations have been conducted using the three-mirror contact glass of Goldmann and concerned early observations.
As a rule there are two pre-formed holes at the posterior hyaloid membrane in cases of recent rhegmatogenous posterior detachment of vitreous body. This finding remains stationary only in some patients. In others an extensive denudation of the posterior surface of the vitreous body occurs by progressive destruction of the posterior hyaloid membrane, the causes of which are unknown.
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The senile destructions of the vitreous body which can be seen with the slit-lamp (formation of visible fibres, vacuoles and posterior vitreous detachment) cause, if sufficiently advanced, small echoblips visible at echographic examination. We reexamined aphakic patients who had no complications during cataract cryo-extraction. In aphakic eyes without postoperative vitreous prolapse into the anterior chamber the echograms usually consisted of uninterrupted series of small amplitude echoes in the vitreous area. In aphakic eyes with postoperative vitreous prolapse into the anterior chamber echo-free parts were found in the vitreous area and also parts showing closer placing of vitreous echoes. The echo-free parts may represent fluid-filled vacuoles. In malignant aphakic glaucomas, which could not be controlled otherwise, we succeeded inaspirating aqueous humour from these echo-free parts by punction. Echography facilitated, in this way, the punction of the trapped aqueous. Echography of the senile vitreous destructions approaches the limits of present ultrasonographic facilities; artefacts may occur, and technical improvements are desirable and possible.