Yasuo Uemura

Glycosaminoglycan and collagen distribution in the developing human vitreous

Abstract · Background: We determined the distribution of glycosaminoglycans and collagens in the developing human vitreous. · Methods: Eighty human eyes from 5 gestational weeks to 2 postnatal years of age were used. Glycosaminoglycan components were determined by enzyme digestion with hyaluronidase or chondroitinase AC and ABC and immunohistochemistry for chondroitin, chondroitin-4-sulfate, chondroitin-6-sulfate, and dermatan sulfate. Collagen distribution was determined by immunohistochemistry for types I, II, and III collagens. · Results: Enzyme digestion showed that throughout development hyaluronic acid is the main glycosaminoglycan in the vitreous and in the extraocular space at 5–7 gestational weeks. Both areas were filled with mesenchymal cells. Immunohistochemistry showed chondroitin-6-sulfate in the vitreous between 6 and 40 gestational weeks, and chondroitin-4-sulfate between 12 and 40 gestational weeks. Hyaluronic acid and chondroitin sulfate appeared in the retina and around the hyaloid vessels at 12–40 weeks. Immunohistochemistry showed type III collagen in the vitreous and around the mesenchymal cells at 5–7 weeks that was replaced by type II collagen after 8 weeks. · Conclusions: Hyaluronic acid is the major glycosaminoglycan in the vitreous throughout development, except for the transient appearance of chondroitin sulfate at 6–40 gestational weeks. Type III is the main collagen in the early developing vitreous that converts to type II collagen at 8 weeks. The primary and secondary vitreous has the same components as these macromolecules. These vitreous glycosaminoglycans and collagens seem to be produced by mesenchymal cells at an early stage and by the retina and hyaloid vessels during middle and late development.

Visual developmental delay

A new concept and classification of visual developmental delay is presented and illustrated with selected cases. A difference between visual developmental delay associated with mental retardation and cerebral blindness is discussed. the importance of two methods, the visually evoked potential (VEP) and preferential looking (PL), for the objective evaluation of simple visual developmental delay is stressed.

The Tokyo Metropolitan Home Vision Screening Program for Amblyopia in 3-Year-Old Children

In August 1989, the Tokyo Metropolitan Government officially began a vision screening program for children aged 3 years 1 month. A 1988 pilot study of 1,303 children this age disclosed five cases (0.38%) of amblyopia. The home vision test, which uses picture cards of familiar figures, proved to be an efficient and inexpensive method of screening when incorporated into the existing health-check program for 3-year-old children. In the initial eight months of the program, 21,906 children were screened. Of these, 419 children (1.9%) were referred to an ophthalmologist for follow-up, and amblyopia was detected in 41 children (0.19%).

Morphological Study on Glycosaminoglycans in the Developing Human Vitreous

The vascular and the avascular vitreous in 7th- and 8th-week human embryos and 9th-week fetuses were stained strongly by alcian blue, while marked decrease in staining by alcian blue was observed in 12th- and 13th-week human fetuses. The nature of alcian blue positive materials was identified as hyaluronic acid and chondroitin sulfate or dermatan sulfate by enzymatic digestion methods and the Scott-Dorling method. The results suggest that distinction between primary and secondary vitreous is difficult by classical histochemical techniques and electron microscopy, and that the vitreous glycosaminoglycans concentration seems to be high at 7th- and 8th-week embyonic stages and decreases at later fetal stages.

Development of visual acuity in infants and young children up to three years evaluated with the preferential looking method

The normal patterns of development of the visual acuity in infants and young children up to the age of three were investigated using the preferential looking method. For those under 12 months old, the forced choice preferential looking method was used; for those above 13 months, a new modified method was used, developed by the authors. From the results it was estimated that the visual acuity of the normal infant at six months is 10 to 15 min; at 12 months, it is about 6 min. The acuity at 24 months is estimated to be 3 min of arc and reaches the value of 1.0 to 1.5 min, which is very near to the level of the adult, at 27 to 30 months. As to the success rate of the preferential looking method, the highest success rate under the age of 30 months was found in the age group from three to six months. The success rate was lowest in the age group from 13 to 18 months.

Electron microscopic comparative studies of phagocytic processes between outer segments and latex microspheres in cultured human retinal pigment epithelial cells

SummaryThe process of phagocytosis in cultured human retinal pigment epithelium (RPE) cells was observed after more than 2 h of incubation with human outer segments and latex microspheres. Fingerlike microvilli were attached to outer segments and entwined around both its ends. The microvilli enveloped the outer segment and cut into the membranous structure, and the same process as that seen in in vivo shedding was observed. The looplike disk membranes and the whole of the outer segment were ingested into the cytoplasm and degraded by the lysosome. Latex microspheres were also ingested into the cytoplasm so as to be enveloped in many fingerlike microvilli. Microfilaments were concentrated in the vicinity of latex microspheres and outer segments, and latex microspheres were placed between two microtubules. Furthermore, when latex microspheres and outer segments were ingested into the cytoplasm, the dilated rough endoplasmic reticulum (rER) contained materials of high electron density and attached ribosomes increased. The rER of the cultured human RPE cells seemed to show a high level of protein synthesis during the phagocytic process. It was observed that cytoskeletons, such as microfilaments and microtubules, and lysosomes had important functions in the phagocytic process, and that there were basically no differences among the objects phagocytized by the cultured RPE cells.

Form-vision deprivation amblyopia and strabismic amblyopia

The treatment program for form-vision deprivation and strabismic amblyopia currently followed in our orthoptic clinic is presented. In unilateral congenital cataract, a disease that causes form-vision deprivation amblyopia, good vision up to 20/20 can be obtained through surgery performed before the patient reaches 8 weeks of age, employing new surgical techniques such as lentectomy and vitrectomy, combined with early aphakic eye correction and occlusion of the healthy eye. In strabismic amblyopia, prevention and/or early treatment are very important, particularly in cases of unilateral infantile esotropia. Our success rate with occlusion therapy was 84.6% using a patch and 83.3% employing atropine cycloplegia. Occlusion therapy is monitored with the preferential looking technique to prevent the development of occlusion amblyopia. The visual prognosis for amblyopia due to unilateral congenital cataract and infantile strabismic amblyopia has been improved compared with previous reports. The prognosis for binocular function remains poor.

Electron microscopic study of the developing human vitreous collagen fibrils.

Vitreous fibrils, and collagen fibrils in other ocular tissues, were observed in 5-, 6- and 7-weeks human embryos. The vitreous fibrils in 7-weeks embryos were distinctly different from the fibrils of other ocular tissues. The vitreous fibrils near the rim of the optic cup were similar to the fibrils in the anterior cavity of the lens vesicle in the 6-week embryo. Broad fibrils were demonstrated with a diameter of 30-40 nm and a striated banding pattern of about 60 nm periodicity.

Morphological Study on the Human Developing Vitreous Collagen Fibrils and Persistent Hyperplastic Primary Vitreous

The human primary vitreous fibrils were similar to the secondary vitreous fibrils on electron microscopic observation. On the other hand, the intravitreal strand in a persistent hyperplastic primary vitreous (PHPV) contained large numbers of collagenous fibrils with 40-50 nm diameters and about 65 nm cross-striation periodicity. Besides these, other types of noncross-striated fibrils, ranging in diameter from 10 to 30 nm were observed in the circumferential region of the intravitreal strand. Moreover, there was complete morphological continuation between the intravitreal strand and the optic disc. Their histochemical properties were very likely collagenous and in part glial. Although the results are based only on 1 case of PHPV, present observations showed that components of the intravitreal strand of PHPV considerably differed from the primary vitreous.

Specular microscopy of posterior polymorphous endothelial dystrophy

Corneal endothelial conditions in two children with posterior polymorphous endothelial dystrophy were studied by specular microscopy. The localized vesicular lesions seen by slit lamp formed demarcated blackout areas where two distinct populations of cells were adjacent. Focal areas of highly pleomorphic cells with increased reflective highlights, which may represent epithelial-like cells, were surrounded by enlarged and pleomorphic endothelial cells (background cells). The average background endothelial cell area was three to four times larger than the control area. The composite cells which appeared to coalesce were also observed among the enlarged background cells.