Retinoblastoma, microphthalmia, coloboma, and neuroepithelioma of the pineal body

A one-month-old infant boy was examined early in life because his mother had bilateral retinoblastoma and his father had bilateral microphthalmia. The ophthalmologist found his right eye was normal size with a coloboma of the iris, choroid, and retina. The left eye was microphthalmic with a coloboma of the uveal tract and retina. A vascularized fluffy white mass in the posterior pole was diagnosed clinically as a retinoblastoma. The tumor regressed with radiation. When the patient was four years of age, a large tumor was found in the region of the pineal recess, causing hydrocephalus and seizures. A biopsy showed an undifferentiated malignant neuroepithelial neoplasm. The patient died within three months of diffuse central nervous system tumor. The unusual findings of a retinoblastoma in a microphthalmic eye with bilateral colobomas and a neuroepithelial neoplasm of the pineal gland are discussed.

Embryology and morphology of microphthalmia in transgenic mice expressing a gamma F-crystallin/diphtheria toxin A hybrid gene

BACKGROUND

Transgenic mice in which elongating lens fiber cells were ablated resulting in microphthalmia have been reported, however, their embryology and detailed morphology have not.

EXPERIMENTAL DESIGN

The morphology of homozygous and hemizygous CDI, transgenic mice carrying the gamma FDT-A gene was studied by light microscopy on different days of gestation as well as postpartum. The findings were compared with normal CD-1 wild type controls.

RESULTS

The earliest changes in mouse embryos transgenic for the gamma F-crystallin/diphtheria toxin A transgene are seen on day 12, when apoptotic cells appear in the area of elongation. In hemizygous embryos, ocular development is relatively normal until day 17 when the lens and eye are slightly smaller than normal and the lens vesicle is filled with abnormal lens material. At this time, the posterior capsule of the lens may rupture, releasing abnormal lens material which disperses throughout the eye, perturbing growth and other ocular structures. Additional breaks may subsequently occur and the ultimate morphology of the hemizygotes correlates with when the posterior capsule ruptures, how much lens material is released, and where it disperses. In homozygous embryos, due to extensive ablation of lens fiber cells, the "lens" becomes a diminutive mass of abnormal lens material, posteriorly located within the eye, and otherwise unable to fulfill its mechanical or inductive role in the development of the cornea, anterior chamber, iris, ciliary epithelium, and zonules with the result that all of these structures are markedly abnormal or absent. In addition, the lens is necessary for the accumulation of vitreous which in turn is required for the growth of the eye as a whole. In homozygous animals, vitreous does not accumulate and severe microphthalmia results.

CONCLUSIONS

This study confirms and extends previous observations and conclusions on the central, orchestrating role of the lens in the development of the eye and illustrates the power of transgenic technology to elucidate the finer points of mammalian ocular development.

Refractive evaluation in thalidomide embryopathy

To evaluate the ocular findings associated with thalidomide embryopathy, we examined 86 of 100 Swedes who had a proven correlation between birth defects and the mother's intake of thalidomide during pregnancy. Cycloplegic refraction, keratometry, and axial length measurements were performed. The subjects were divided into four groups according to their physical malformations, giving a time frame for when in gestation the insult occurred (the sensitive phase for thalidomide is 20-36 days after conception). The results indicate a trend toward shorter and longer axial lengths, high refractive errors, and corneal astigmatism in thalidomide embryopathy compared to controls, and in addition there was a tendency for those anomalies to occur in the group with the earliest thalidomide-induced defects. It is suggested that thalidomide disturbs the growth and shape of the eye and that this effect is exerted early in its teratogenic period.

Abnormal sclerocytes in nanophthalmos

Scleral tissue from a nanophthalmic patient was examined morphologically and by a tissue culture method. Collagen in the unusually thickened scleral tissue was arranged in irregularly interlacing bundles. Results of tissue culture studies showed sclerocytes that seemed to secrete many granules that stained positively with Alcian blue and periodic acid-Schiff (PAS). No granules were seen in cells of scleral tissue cultured from two control eyes. These findings may be the result of the modified glycosaminoglycan metabolism, which in turn contributes to the abnormal packing of collagen bundles and thickening of sclera in nanophthalmos.

Neuroepithelial adenocarcinoma of the eye

A 29-year-old male patient with a microphthalmos on the right side since birth was seen in June 1987 in the University Eye Clinic because of a massive exophthalmus of the former microphthalmic eye. Computer tomography revealed a diffuse, infiltrating tumor of the right orbit. The bulbus was not demarcated, and the whole orbita had to be eviscerated. Histologically, we found a solid, undifferentiated tumor with clear signs of malignancy. It consisted of epithelial cells, partly in nest formation, which were keratin positive and vimentin negative, and of more spindle-shaped formations which were keratin negative and vimentin positive. In some areas, the tumor showed a tubular or an adenoid proliferation. CEA or S-100 could not be demonstrated. The histopathological diagnosis was neuroepithelial adenocarcinoma of the eye. The differential diagnosis and the genesis of the tumor are discussed.

Morphology of a dicephalic cat

A detailed anatomical study of a dicephalic iniodymic monosomic cat in conjunction with the morphogenetical implications of the observed anomalies is presented. The animal exhibited two heads joined at the level of an anomalous medial exoccipital bone. Two brains and two foramina magna were present. The vertebral column was single but the cranial cervical vertebrae (C2 to C5) had doubled bodies. Cervical rachischisis with myeloschisis were associated defects. Two nasopharyngeal and oropharyngeal cavities converged caudally into a single laryngopharynx. The esophagus, larynx and trachea were single. Duplication of the tongue and hyoid apparatus was present. Palatoschisis affected both oral cavities. Hypoplasia of the anatomical structures in the medial aspects of both heads was observed. Microphthalmia was also observed in both medial eyes. Comparative aspects of the morphology, causative agents, and mechanisms and anomalous morphogenesis of anterior duplications are reviewed and discussed.

Developmental analysis of ocular morphogenesis in alpha A-crystallin/diphtheria toxin transgenic mice undergoing ablation of the lens

The role of the lens in early eye development was examined in transgenic mice carrying the cytotoxic diphtheria toxin A gene driven by hamster alpha A-crystallin promoter sequences. Mice hemizygous for this construct are microphthalmic and contain a vacuolated and highly disorganized lens, whereas adult homozygous mice are completely ablated of the lens and lack a pupil, aqueous and posterior chamber, vitreous humor, iris, and ciliary body and show extensive convolution of the sensory retina. Developmental analysis of animals homozygous for the transgene revealed that the optic cup and lens vesicle form normally and that ablation of the lens occurs as a gradual degenerative process beginning between Days 12 and 13 of gestation. Degeneration of the lens vesicle coincides with retarded growth and development of the neuroretina, sclera, and cornea. The anterior lip of the optic cup fails to differentiate into the normal epithelium of the iris and ciliary body and the vitreous body does not develop. Although the retinal layers apparently form normally, retinal folding becomes prominent following lens degeneration. These results suggest that development of a functional lens from Embryonic Day 12.5 onward is critical for formation of the ciliary epithelium, iris, and vitreous body, as well as for appropriate growth, development, and maintenance of morphology of the retina, cornea, sclera, and optic nerve. Our results also provide information on the time course of DT-A-mediated cell destruction in vivo and are discussed in context with previous lens ablation studies and the importance of developmental analysis for interpretation of the extent to which morphogenetic aberrations are concurrent with or secondary to genetic ablation of the target tissue.

The prenatal development of the optic fissure in colobomatous microphthalmia

The coloboma in the cinnamon mouse homozygous for the microphthalmia gene is caused when optic fissure closure, which normally occurs between the 11th and the 13th gestational day, does not occur. This study sought to determine the cause of this fusion failure, and to identify any foci of fusion that occur later in gestation. Microphthalmic fetuses from the 11th-20th gestational day were obtained by datemating cinnamon mice heterozygous for the microphthalmia gene. Coronal serial sections of the eyes were examined at light and electron microscopy. Initially, the fissure margins became apposed only in the posterior aspects of the eye. A failure of basement membrane disintegration at the fissure margins prevented fusion at the 12th and 13th days. On the 14th day, small foci of basement membrane disintegration were identified in the area of the developing optic disc. Although the fusion zone enlarged later in gestation, it was limited to the area of the optic disc and showed that the two retinal layers did not separate. This study has shown that abnormal growth and invagination lead to delayed apposition of the optic fissure margins. These features together with a failure of basement membrane disintegration appear to be the main factors involved in coloboma formation. It is suggested that the excessive number of outer-layer cells that are inverted into the fissure, as well as abnormal or reduced numbers of phagocytic cells, may affect the persistence of the basement membrane. Alternatively, a primary defect of the pigment epithelial cell may lead to the development of the hypercellular and nonpigmented outer layer associated with the lack of basement membrane disintegration and nonfusion in this mutant.

Abnormal scleral collagen in nanophthalmos. An ultrastructural study

Ten patients with bilateral nanophthalmos underwent sclerectomies for uveal effusion. Ultrastructural examination of the sclera revealed abnormal collagen in seven patients. Four showed dramatic fraying of the collagen fibrils into fine filaments 2 to 3 nm in diameter. In three of these cases and three other cases without fraying, there were foci of 10- to 35-nm small collagen fibrils, some appearing to arise by splitting of otherwise normal collagen fibrils. In areas of fraying, elastic fibers were absent. All patients had a wider range of collagen diameters than did control subjects. The youngest patient with fraying also had Hallermann-Streiff syndrome. In three patients, no collagen abnormality was found. The clinical feature correlating best with the presence of abnormal collagen was an extremely small eye, since the three patients without collagen abnormality had the largest eyes (range of anteroposterior diameters, 19.2 to 20.3 mm). Nanophthalmos appears to result from several distinct defects.

Histological examination of chick embryos with bilateral microphthalmus with reference to laterality in the visual apparatuses

The histological abnormalities of chick embryos with bilateral microphthalmus were examined in serial paraffin sections with special reference to laterality in the visual apparatuses, including the cornea, lens, neural retina and pigment epithelium. There was marked laterality in the above structures; some eyeballs had individual, if incomplete, sublayers of the cornea and the neural retina, and others not. The sublayers of the neural retina were occasionally observed even in eyeballs at the stage of optic vesicle formation, in contrast to the previous notion that the pigment epithelium induces the maturation of the primordial neural retina after optic vesicle differentiation into the optic cup. There was also a case where developmental differences between the right and left eyeballs were absent except in the lens. These findings suggest that chick embryos with bilateral microphthalmus exhibit a more complex histological profile or diversity than previously considered, possibly as a result of the differential actions of various mutagens and endogenous trophic factors on the developing visual system.

Relationship of cell death to cyclophosphamide-induced ocular malformations

C57BL/6J mice were used to study the ocular teratogenic effects of cyclophosphamide administered to pregnant females on d 9 of pregnancy at a dose of 5 mg/kg body weight. Nile blue staining demonstrated increased cell death at the base of the optic stalk, in the optic vesicle, and in the perivesicular mesenchyme in treated embryos. Malformations studied at gestational d 11 and 16 by light and scanning electron microscopy included microphthalmos, microphakia, and aphakia and were predictable based upon patterns of increased cell death. These anomalies are similar to those reported with exposure to ethanol or isotretinoin on gestational d 7.

Ocular abnormalities in Patau syndrome (chromosome 13 trisomy syndrome)

The ocular pathology in eight patients with trisomy 13 (Patau syndrome) is discussed and compared with the undisturbed development of the eye.

Microphthalmos with colobomatous orbital cyst: clinical, histological, immunohistological, and electronmicroscopic findings

A case of unilateral microphthalmos with orbital cyst is presented. This rare and severe malformation is a non-hereditary disorder. Pathologically it represents a failure in the closure of the embryonic fissure at the 7-14 mm stage of gestation. Staining for neurofilaments permitted the identification of rudimentary optic nerve fibers within the gliomatous cyst wall. Special stains for glial fibrillary acidic protein as well as scanning and transmission electron microscopy were used to characterise the neuroglial cell lining of the cyst wall, and to show microvilli on its inner surface.

Simple microphthalmos

Simple microphthalmos was diagnosed in 22 patients on the basis of a normal-appearing eye and a total axial length at least 2 SDs below the mean for age. Anterior segment length was normal in most patients while posterior segment length was at least 2 SDs below the mean in all patients, indicating that disproportionate reduction in posterior segment length accounted for the microphthalmos. The normal values for total axial length, anterior segment length, and posterior segment length were determined from the analysis of axial length measurements obtained from age-similar controls. Ten patients had isolated microphthalmos. One of them was diagnosed as having nanophthalmos on the basis of microcornea, total axial length less than 18 mm, and absence of systemic disease. Twelve patients had associated systemic disorders, such as fetal alcohol syndrome, myotonic dystrophy, and achondroplasia, which implicated decreased size of the optic cup, altered vitreous proteoglycans, low intraocular pressure, and abnormal release of growth factors in the pathogenesis of microphthalmos.

Complex microphthalmos

Forty patients were diagnosed as having complex microphthalmos on the basis of a malformed globe with a total axial length measurement at least 2 SDs below the mean for age-similar controls. Three had anterior segment dysgenesis; 4, congenital lens abnormalities; 14, chorioretinal colobomas; 12, persistent hyperplastic primary vitreous; 4, retinal dysplasia; and 3, complex malformations due to ipsilateral facial malformations. Measurements of total axial length indicated that complex microphthalmos was congenital and that postnatal growth of the malformed eye was similar to that of normal eyes. In most patients the anterior segment length was normal, while in all patients the posterior segment length was at least 2 SDs below the mean. Corneal diameter correlated significantly with total axial length (r2 = .57) and decreased linearly as total axial length decreased. In most patients in whom measurements were obtained, the lens and corneal power were increased, thereby compensating for decreased total axial length. We propose that inadequate production of secondary vitreous is the cause of the microphthalmos, given that the posterior segment was disproportionately reduced in size and the secondary vitreous is its predominant component. Evidence that each of the various ocular malformations can influence the production of secondary vitreous is presented.

The optic fissure in the normal and microphthalmic mouse

The gene for microphthalmia in the homozygous cinnamon mouse produces colobomatous microphthalmia due to failure of closure of the optic fissure. Optic fissure formation and closure were examined in control cinnamon and homozygous microphthalmic foetuses from the 10th to the 13th gestational day using light and electron microscopy. This study showed that basal lamina degeneration and cell death occurred in the area of fusion in the control eyes. Examination of the optic fissure in homozygous microphthalmic foetuses showed cell death in the fissure margins, but there was failure of optic fissure closure associated with persistence of the basal lamina. It is therefore suggested that absence or abnormality of programmed disintegration of the basal lamina prevents fusion in the mutant leading to the development of colobomatous microphthalmia.

[Unilateral congenital cataract, iridic hypoplasia and macular degenerative lesions]

The present paper reports on the case of an 18-year-old man with congenital cataract and microphthalmos of the left eye, divergent strabismus and sursum vergens. Macular degenerative lesions were also present in the right eye, hypoplasia of the iris in both eyes and fixation nystagmus with equal jerks in both directions. The general physical examination showed congenital atrial septal defect. The morbid cardiac and ocular association plead for rubella embryopathy.

[Unilateral congenital glaucoma]

The paper reports on the case of a 6-year-old child with OD congenital glaucoma and increase of the ocular globe volume with ruptures of Descemet's membrane. VARE = 1/8 non correcting, VALE = 34 mmHg, RE--divergent strabismus. The left microphthalmus with the corneal diameter of 9 mm. Normal karyotype. Trabeculectomy was performed at the right eye. Good postsurgical evolution. This is a case of phenocopy because in the development and formation of the iridocorneal angle in the sixth month of pregnancy, a series of extrinsic teratogenous factors appeared: measles, influenza, toxemia of pregnancy that produced modifications of the trabecula.

Pulmonary agenesis association with nonimmune hydrops

Bilateral pulmonary agenesis is a rare malformation with 13 cases previously reported. To our knowledge, none of these cases have been associated with hydrops fetalis. We report a 36 weeks, hydropic female infant (46XX) with bilateral pulmonary agenesis, unilateral microophthalmia, and bilateral renal dysplasia. These eye and pulmonary findings have now been associated several times and may constitute a new syndrome. Ultrasound examination before delivery showed polyhydramnios and fetal hydrops. At autopsy the heart was structurally normal, aside from absent pulmonary connections. The ductus arteriosus was partially closed. This was felt to be etiologic in the hydrops. As the source of the amniotic fluid here could not be urine or pulmonary secretions, direct fluid transfer from fetal vasculature or skin was the likely origin.

Retinal projections to the medial terminal nucleus of the rat with induced unilateral congenital eye defects

Retinal projections, particularly the ipsilateral projections, to the medial terminal nucleus (MTN) of the accessory optic system were investigated by autoradiography in adult rats after being reared in one of three different conditions: (1) normal visual experiences, (2) an application of trypan blue for intrauterine induction of congenital unilateral anophthalmia; and (3) the procedures for intrauterine production of congenital microphthalmia in which both eyes are reduced in size. In congenital monocular rats, there was an increase of uncrossed retinal projections to the MTN which does not normally exist. The expansion of the ipsilateral projection was markedly greater in the monocular rats than those inflicted with microphthalmia. The expansion may be due to the failure of the retraction of the ipsilateral retinal projections to the MTN and the collateral sprouting of optic fibers from the remaining eye.

Genetical and histological studies on a mouse displaying microphthalmia and cataract

A male mouse displaying bilateral microphthalmia and cataract was found among the offspring of pregnant Slc: ICR mouse treated intraperitoneally with 10 mg/kg methylnitrosourea on gestational day 4. This mutant has been maintained by brother-sister mating. By the mating test with normal Slc: ICR mice, this character was revealed to be inherited by an autosomal single recessive gene. Linkage test with the brown locus showed that this mutant gene is linked with the B gene and mapped on chromosome 4. The histological study of the eyes of adult mutant mice revealed various abnormalities all over the eyes, especially in the lens and neural retina. Embryologically, the mutant mice showed persistent connection between the lens vesicle and the surface ectoderm by a cellular stalk, and also the formation of retinal infolding, in the early stages of eye development. Both were considered to be responsible for the consequent abnormal development and degradation of the lens. These results suggest that the mutant mouse we found may be an allele of the dysgenetic lens (dyl) reported by Sanyal and Hawkins.

Morphological and genetic characteristics of the open-eyelid mutant spontaneously occurring in NC-strain mice

A heritable open-eyelid mutant which arose spontaneously in the NC strain of mouse in 1982 has been maintained as the NC-eob line through brother-sister matings. When the line exceeded the 12th generation, its reproductive capabilities were initially compared with those of the NC strain. Then eye abnormalities were investigated morphologically and genetically. Although most of the reproductive parameters in the NC-eob line were comparable to those in the NC strain, a significant decrease was observed in the mean number of pups delivered, and the viability of pups at 7 days of age was reduced to 55%. The eyelids of pups were widely open at birth. The exposed cornea dried within a few hours and a bloody exudate appeared around the margin of the eyelids. At 1 day of age, the eye opening was smaller in size and covered with a scab. Histological examination demonstrated apparent inflammatory changes in the cornea and conjunctiva. At 21 days of age, the eyes revealed opacity, a rough surface, and microphthalmia. Histological findings in the cornea, such as keratosis and vascularization, coincided with the eye opacity. The weight and size of the eyeballs were almost the same as those in normal NC pups. However, a significant decrease in the length of the palpebral rima was evident and this was considered to be the cause of the microphthalmia. The results of genetic analysis indicated that these eye abnormalities were caused by an autosomal recessive gene, eob. These results suggested that the eob gene might be a new mutation manifesting semi-lethality as a pleiotropic effect.

Isolated "clinical anophthalmia" in an extensively affected Arab kindred

A highly inbred kinship is described, in which 19 individuals were afflicted with bilateral profound microphthalmia without associated anomalies and with normal intelligence. Autosomal recessive inheritance is demonstrated. This kindred is instructive for genetic counseling since the affected individuals always have bilateral microphthalmia in the absence of other affected organ systems.

Experimental induction of microphthalmia in the chick embryo with a single dose of cisplatin

Chick embryos were injected on the fifth day of incubation with 75 ng cis-diamminedichloroplatinum II (cisplatin) and killed at daily intervals. Bilateral microphthalmia appeared in 88% of the surviving embryos; the decrease in eye size was noticeable 2 or 3 days after injection. Coinciding with this, macroscopic, histological, and ultrastructural changes started to appear in the ciliary body: ciliary processes failed to form and the cells in the inner layer of the ciliary epithelium underwent degenerative changes. Changes in the retina appeared somewhat later. Despite the decreased growth rate of the whole eye the neural layer of the retina continued to grow rapidly; as a result, it formed numerous folds and acquired a glandular appearance. In the most severe cases the rapidly growing retina would invade the ciliary region and replace completely the degenerated inner layer of the ciliary epithelium. It has been shown by previous authors that intraocular pressure is a determinant of eye expansion and also that the secretion of water and ions by the ciliary epithelium is important for the maintenance of that intraocular pressure. On this basis, our results are interpreted as indicating that the primary lesion induced by cisplatin was in the ciliary epithelium and that microphthalmia was the consequence of decreased pressure. It is also concluded that the retinal changes were due to the fact that the retina continued to grow despite the lack of expansion of the eye as a whole.

The Lenz microphthalmia syndrome

We examined two patients with the Lenz microphthalmia syndrome. When findings from these two patients and those from ten other patients in the literature were combined, the following abnormalities were observed: microphthalmos in all patients; developmental retardation in 11 patients (92%); external ear abnormalities in ten patients (83%); microcephaly in ten patients (83%); blepharoptosis in nine patients (75%); skeletal anomalies (excluding digital anomalies) in eight patients (67%); dental abnormalities of number and position in eight patients (67%); digital anomalies in seven patients (58%); urogenital anomalies in six patients (50%); and cleft lip and palate abnormalities in four patients (33%). Cardiac anomalies, imperforate anus, hearing loss, spastic diplegia, sacral pits, webbed neck, and abnormal dermatoglyphs were rarely seen. One of our two patients had a dislocated lens and retinal detachment.

Nanophthalmic uveal effusion

A nanophthalmic patient with hypermetropia, shortened anterior-posterior axial length, and thickened choroid presented with a choroidal detachment and nonrhegmatogenous retinal detachment (NRRD). He underwent partial thickness, 5 x 7 mm, sclerectomies and 1-2 mm central sclerostomies 9.5 mm posterior to the limbus, specifically avoiding vortex veins. Complete resolution of the retinal and choroidal detachments occurred in spite of postoperative ultrasonograms demonstrating residual choroidal-scleral thickening. The effectiveness of this technique in our patient, in light of recent studies demonstrating histochemical and microscopic abnormalities in nanophthalmic sclera, suggests impairment of trans-scleral protein transport as the primary pathophysiologic mechanism in nanophthalmic uveal effusion.

A morphologic study of osteoclasts isolated from osteopetrotic microphthalmic (mi/mi) mouse and human fetal long bones using an instrument permitting combination of light and scanning electron microscopy

Cell surface structures of isolated osteopetrotic (mi/mi) and normal murine (+/+ and +/mi) and human osteoclasts were examined in a microscope combining light and scanning electron microscopy (LM/SEM). Tartrate-resistant acid phosphatase (TrAP) was used as an histochemical osteoclast marker. In osteopetrotic bone, as in normal murine bone, TrAP activity was exclusively seen in osteoclasts and preosteoclasts and was therefore judged a suitable marker for identification of isolated osteoclasts. A method was developed for preparation of LM/SEM specimens from osteoclast-enriched cell suspensions. In the LM/SEM isolated osteoclasts were easily recognized in the LM mode by TrAP contents. In specimens prepared from murine cells, but not human cells, LM identification of osteoclasts by TrAP was essential. This was in particular true for small, mononuclear, mi/mi osteoclasts. All osteoclasts examined had a villous appearance and were well spread over the glass substrate. There were no differences in cell surface morphology and in adherence to glass between osteopetrotic and normal osteoclasts.

Congenital retinal folds in Sheffield-Wistar rats

Retinal folds are described in male rats of a Wistar-derived strain, which occasionally shows microphthalmia and cataract. The less severe lesions mainly affect the outer retinal layers and contain microretinal detachment, cell rosettes, phagocytic cells and lipid debris. More severe folds involve all the retinal layers, exhibit subretinal haemorrhage, and photoreceptor outer segment debris throughout the lesion and on the vitreal surface. The lesions are discussed in relation to previous observations of retinal folds.

Genetic ablation: targeted expression of a toxin gene causes microphthalmia in transgenic mice

Lineage-specific regulatory elements can be used to direct expression of a variety of genes to specific tissues in transgenic mice. If the hybrid constructs contain a gene encoding a cytotoxic gene product, then genetic ablation of a specific cell lineage can be achieved. We have generated six transgenic mice by introducing into fertilized eggs the mouse gamma 2-crystallin promoter fused to the coding region of the diphtheria toxin A-chain gene. Three of these mice and all the transgenic offspring analyzed were microphthalmic. The lenses of these mice displayed considerable heterogeneity: some were almost normal morphologically but reduced in size, whereas others were grossly aberrant and deficient in nuclear fiber cells. These studies indicate that programmed ablation of specific cell types can be stably transmitted through the germ line.

Corneal transplantation in microphthalmic eyes

We performed corneal transplantation in nine microphthalmic eyes of five patients, who ranged in age from 1 to 63 months. The anteroposterior diameter of the eyes ranged from 12.5 to 16 mm. Complications from the surgery included superficial epithelial erosions in three eyes, leading to superficial scarring in one eye, glaucoma, and suture microabscesses. Despite these complications, seven of nine grafts have remained clear and vision developed in all eyes.

The development of the teeth of the microphthalmic (mi/mi) mouse

The histological development of the teeth of mice homozygous for the osteopetrotic mutation microphthalmia (mi) in the mouse is described for the period 1-20 days post partum. The abnormalities described, including overall retardation, impaired root formation, encapsulation by bone and consequent non-eruption, are discussed and compared to the defects seen in the grey lethal (gl) mouse.

Organization of the dorsal lateral geniculate nucleus in a cat with congenital microphthalmia

The effects of congenital monocular microphthalmia on the development of the lateral geniculate nucleus were examined in a 10-week-old cat. The left eye and optic nerve in this animal appear normal. The right eye is about 30% smaller in volume than the left and the optic nerve from this eye has a cross-sectional area that is only 15% that of the left. In addition, this nerve contains few, if any, large myelinated axons. Both lateral geniculate nuclei are abnormal and the abnormality differs rostrally and caudally. The caudal portion most closely resembles the normal nucleus. Retinal input from both eyes is segregated into cellular laminae that are separated from each other by cell sparse interlaminar zones. However, the input from the microphthalmic eye seems to be sparse and patchy and it does not support normal cell growth. All neurons, including glutamic acid decarboxylase-positive (GAD+) neurons, in laminae innervated by the small eye are reduced in size in a pattern similar to that seen following the removal of retinal input. In comparison, the rostral portion of the nucleus receives very little input from the microphthalmic eye. Instead the normal eye densely innervates nearly the entire nucleus. In this region, interlaminar zones fail to form but the input from the normal eye is able to support cell growth including the growth of GAD+ neurons.

Extraocular muscles in the microphthalmic rat

The extraocular muscles in a mutant microphthalmic strain of rat were studied. The eyeball of this strain of rat is reduced to about a third in diameter of that of the normal rat. Nevertheless, in the orbit of the mutant rat, every one of the extraocular muscles was identified; their origins and courses were the same as in the normal rat, but differences existed in the insertions. These insertions could be classified into three groups: Group A (retractor bulbi): like normal insertion into the eyeball. Group B (superior rectus and superior oblique): attachment of tendonlike insertions to each other; these muscles come from opposite directions and form a loop. Group C (lateral, medial, and inferior rectus and inferior oblique): insertion into connective tissue surrounding the reduced eyeball. The volume of each muscle of the mutant rat was smaller than that of the normal rat; moreover, significant differences existed in the degree of reduction in the volume of each muscle group classified according to the change of insertion. In the group A muscle the volume was only 33% of the normal volume, whereas group B was 74% and group C was about half of normal.

Neurons of the ventral lateral geniculate nucleus of the hereditary microphthalmic rat: a Golgi study

Neurons of the lateral part of the ventral lateral geniculate nucleus in the microphthalmic rat were examined by the Golgi-Cox method. These neurons were divided into the same three types as normal neurons. However, the number of branches and the length of primary dendrites of these neurons were fewer and shorter, and the size of their perikarya was smaller, compared with normal cases.

Uncrossed retino-geniculate and retino-tectal projections in the hereditary unilaterally microphthalmic rats

The dorsal lateral geniculate nucleus (CGLd) of the hereditary unilaterally microphthalmic rats showed a diminution of volume and an increase of neuronal density on the contralateral side of the vestigial eye without the optic nerve (about 60 and 160% of the normal, respectively; P less than 0.001). No significant changes were observed in the ipsilateral CGLd. Uncrossed retino-CGLd and -tectal projections were studied using the anterograde axonal transport of HRP in adult rats with the congenital unilateral microphthalmia. Aberrant expansions of the uncrossed retinal projection widely covered CGLd and the superficial layers of the superior colliculus (SCS). The distribution pattern of expanded uncrossed retinal pathway in the mutant was essentially similar to that of neonatally one-eyed rats.

Quantitative analysis of the oculomotor nuclei in the mutant microphthalmic rat

A quantitative analysis of the oculomotor, trochlear, and abducens nuclei was carried out in the mutant microphthalmic rat. In this strain of rat, the eyeball is reduced to about one-third in diameter, and there is no optic nerve. Nevertheless, this strain possesses all the types of extraocular muscles; however, the volume of these muscles is reduced from 33 to 74% of the normal values. The oculomotor, trochlear, and abducens nuclei in this mutant rat were found in the same location as in the normal ones. Moreover, the neurons in these nuclei in the microphthalmic rat did not appear to be any different from those in the controls. The neuronal population of these nuclei was reduced by 63% (oculomotor), 50% (trochlear), and 61% (abducens) of normal values, respectively. The long axis of all neurons of these nuclei in the microphthalmic and normal rats was measured. In all three nuclei of both strains, the size histograms showed a unimodal distribution ranging from 10 to 35 micron, with peaks at 20 to 25 micron. There was no significant difference between the normal and mutant strains. Consequently, the only influence of the shrinkage of the muscles which they supply was seen in the reduction of the cell populations of these nuclei.

Uncrossed retinal projection to the medial terminal nucleus of the accessory optic system in the hereditary unilaterally microphthalmic rat

The uncrossed optic projection to the medial terminal nucleus of the accessory optic system was studied in adult rats with hereditary unilateral microphthalmia. The vestigial eye of the mutant completely lacks the optic nerve. After injection of HRP into the remaining eye the ipsilateral labeled fibers of the accessory optic system via the superior fasciculus distinctly covered the three terminal nuclei. No ipsilateral inferior fasciculus of the accessory optic system was labeled. Aberrant expansion of the uncrossed superior fasciculus fibers was observed in the medial terminal nucleus.

Internal hydrocephalus, optic nerve aplasia, and microphthalmia in CPB-WE (Wezob) and Cpb:WU (Wistar) rats

Wistar rats of the inbred CPB-WE and the random bred Cpb:WU strains have been used in neuroanatomical studies. In both groups of rats a high incidence of hydrocephalus was observed. In the CPB-WE rats the ventricular dilatation was accompanied by optic tract lesions and microphthalmia. The present report describes the gross and microscopic findings in these rats and discusses the possible aetiology.

Neurons of the dorsal lateral geniculate nucleus of the hereditary microphthalmic rat: a Golgi study

Neurons of the dorsal lateral geniculate nucleus (LGNd) in the microphthalmic rat were examined by the Golgi-Cox method. LGNd neurons in the microphthalmic rat were classified into the multipolar (I) and bipolar (II) types as in the normal rat. The multipolar type was further divided into two subclasses (Ia and Ib) on the basis of their dendritic patterns. The proximal portion of their primary dendrites was thinner than in normal LGNd neurons. The Ia cells had 6-7 primary dendrites extending radially, while the Ib cells had 3-4 primary dendrites spreading primarily parallel to the optic tract. Type II cells had two or three primary dendrites emerging from the cell bodies. In both types, primary dendrites were shorter in length or less branched than usual. These results suggested that LGNd neurons in the microphthalmic rat had smaller dendritic fields than those in the normal rat.