Ectopic Lens Research Articles

Lens Induction by Pax-6 inXenopus laevis

Despite extensive study following the pioneering work of Spemann on lens development (Spemann, H. (1901)Verh. Anat. Ges.15, 61–79) and the subsequent establishment of the concept of embryonic induction, the molecular mechanism of vertebrate lens induction remains largely unknown. Here we report that inXenopusexpression of Pax-6 results in lens formation in a cell autonomous manner. In animal cap experiments, Pax-6 induced expression of the lens-specific marker βB1-crystallin without inducing the general neural marker NCAM. Ectopic Pax-6 expression also resulted in the formation of ectopic lenses in whole embryos as well as in animal cap explants indicating that in vertebrates, as well asDrosophila(Halder, G., Callaerts, P., and Gehring, W.J. (1995)Science267, 1788–1792), Pax-6 can direct the development of major components of the eye. Interestingly, ectopic lenses formed in whole embryos without association with neural tissue. Treatments giving rise to anterior neural tissue in animal cap explants resulted in the expression of both βB1-crystallin and Pax-6. Given the ability of Pax-6 to direct lens formation, we propose that the establishment of Pax-6 expression in the presumptive lens ectoderm during normal development is likely to be a critical response of lens-competent ectoderm to early lens inducers.

Ectopic lens induction in fish in response to the murine homeobox gene Six3

Recent findings show an unexpected conservation of genes involved in vertebrate and insect eye development. The Drosophila homeobox gene sine oculis is crucial for eye development. Its murine homologue, Six3 is expressed in the anterior neural plate, a region which is involved in lens induction in Xenopus. To examine whether Six3 participates in the process of eye formation, mouse Six3 was ectopically expressed in fish embryos. The results show that Six3 is sufficient to promote ectopic lens formation in the area of the otic vesicle and that retinal tissue is not a prerequisite for ectopic lens differentiation. Our findings suggest a conserved function for Six3 in metazoan eye development.

The surgical management of nontraumatic ectopic lenses.

We report the results of limbal lensectomy for ectopia lentis in 50 eyes of 30 children over a period of 7 years. The reasons for surgery were poor visual acuity in 47 eyes and dislocation of the lens into the anterior chamber in three. Best-corrected visual acuity improved in all except two patients, both of whom had glaucoma: in one (with an unusual syndrome), a vitreous hemorrhage occurred that resulted in light-perception-only vision; in the other, a persistent uveitis developed that eventually required secondary vitrectomy. Visual acuity was unchanged in two patients. Peaked pupil occurred in seven. We conclude that, unless there are associated ocular diseases, limbal lensectomy in childhood ectopia lentis effectively improves visual acuity with few complications.

Sclerosis of the Skin in the GEMSS Syndrome

We describe a recently observed set of autosomal dominant GEMSS (glaucoma, lens ectopia, microspherophakia, stiffness of the joints, and shortness) syndrome in a 47-year-old woman and her 23-year-old son. In addition, sclerosis of the skin, from which both patients suffered, is investigated in detail. The histologic examination of skin biopsy specimens obtained from the upper aspects of the backs of both patients revealed a markedly thickened dermis. Immunohistochemical examination of the dermal collagen bundles showed a collagen pattern similar to systemic sclerosis and normal control skin. In situ hybridization showed a markedly enhanced gene expression of transforming growth factor beta 1. The sclerotic skin changes in GEMSS syndrome are the result of an abnormally increased production of normal collagen that might be attributable to the enhanced in situ production of transforming growth factor beta 1.

Management of the Subluxed Crystalline Lens

There has been a traditional reluctance to remove a subluxed (ectopic) lens because of the high surgical risk. The use of closed intraocular microsurgical techniques, however, now allows greater intraoperative control with few complications. The authors present the results of subluxed lens extraction, by limbal or pars plana lensectomy, in 44 eyes of 24 patients, in which the indication for surgery was lens subluxation causing a reduction in visual acuity or uncorrectable refractive error. Visual acuity was improved in all cases after surgery, with no significant complications. Patients with reduced visual acuity secondary to ectopic lenses have a good visual prognosis after lensectomy using a closed intraocular microsurgical technique.

Lens-specific expression of recombinant ricin induces developmental defects in the eyes of transgenic mice.

An expression system for cell lineage ablation in transgenic mice was constructed in which a modified form of the A subunit of ricin, a toxic lectin produced by the castor bean Ricinus communis, can be expressed under the direction of tissue-specific regulatory signals. A chimeric gene was formed by fusing the promoter and 5'-flanking sequences of the lens-specific mouse alpha A-crystallin gene with a modified ricin A cDNA, and this construction was integrated into the germ line of transgenic mice. These animals develop profound microphthalmia with severe developmental defects of the eye, relating primarily to the disorganization and death of cells forming the lens. In addition, this defect is associated with several abnormalities, including eye size, folding of the retina, and ectopic lens material in other regions of the eye. The phenotype of this engineered developmental mutation suggests that the normal development of alpha A-crystallin-producing lens fiber cells is essential for the proper growth, organization, and orientation of optic structures.

The anterior hyaloid membrane of the vitreous body in congenital ectopic lens

Congenital, bilaterally symmetrical dislocation of the lens within the posterior chamber is referred to as lens ectopia. The behavior of the anterior hyaloid membrane in congenital lens ectopia has not been considered hitherto. The anterior hyaloid membrane in the aphakic area of the pupil is intact or ruptured and the ciliovitreal connex in the region of the lens dislocation may be normal or absent. If surgery is planned because of the dislocation, a knowledge of biomicroscopic details of the anterior hyaloid membrane might be useful.

The marfan skull.

The classic clinical features of Marfan syndrome include ectopic lens, valvular heart disease and dissecting aneurysm, and long, narrow extremeties associated with tall stature. When the classic features are incomplete, diagnosis is uncertain. This study presents some radiographic measurements of the skull in patients with the Marfan syndrome, in an attempt to aid diagnosis by quantitating the features defining the syndrome. Compared with the normal skull, the Marfan skull was found to be longer, taller, thicker, and to have have increased frontal sinus area. The most consistent and therefore diagnostic abnormality ws increased height.

A Case of the Cryptophthalmos Syndrome

A case of the cryptophthalmos syndrome is presented, showing bilateral absence of separate eyelids and of the palpebral fissure, the facial skin being continuous over both eyes. Low set ears, marked syndactylies, absence of the urinary tract and external genital hypertrophy were noted, while laryngeal atresia allowed a survival of 5 min only at birth. Histopathological study showed the absence of the conjunctiva, and the ectopic lens surrounded by coarse connective tissue in both eyes. The eyes showed a single chamber: no normal corneal elements, iris or anterior chamber were identifiable and the ciliary body was abnormal. An excessive vascularisation of the peripheral retina and a subretinal deposit of lenticular bladder cells were additional features. The karyotype was that of a normal female.

Ultrastructural abnormalities in a microspherical ectopic lens

In order to establish the congenital structural defects which lead to lens luxation (ectopia lentis), several cases of dislocations are being studied. In this study, the three-dimensional ultrastructure of a congenital microspheric ectopic lens revealed lens structural anomalies as well as malformations of the zonules. The lens fibers were abnormal in distribution, size, and morphology. The most striking difference was the decrease in lens fiber cross-sectional area to 20% of normal. This decrease is seen in all zones of fiber lamellae and may be the direct cause of the abnormal size and shape of the lens. The cortical lens fibers also displayed surface openings which appeared to communicate with intracellular cavities. Two types of zonules were observed; one composed of fibrils of normal dimension which were attached on the anterior inferior lens surface and the ciliary body; the other, composed of abnormally large fibrils, and attached only to the lens surface. From our observations, the primary defect which produced the lens luxation was the decrease in lens fiber dimensions causing a decrease in lens size and thus an increased circumlental space. The spatial relationships between the lens and surrounding tissue is essential for zonular development. the maintenance of the suspensory system and the functions of accommodation.

Iris Transillumination and Variable Expression in Ectopia Lentis Et Pupillae

Six children in three families showed variations of the rare genetic syndrome, ectopia lentis et pupillae. The siblings in two affected families demonstrated intermingling of simple lens ectopia with ectopia lentis et pupillae, suggesting that some types of simple ectopia lentis represent an incompletely expressed form of the full ectopia lentis et pupillae syndrome. Those patients with simple lens ectopia as well as those with ectopic lenses and pupils had striking transillumination of the iris periphery. Microphakia, cataract, and other anterior segment abnormalities were also observed.

The lenticular attachment of the zonular apparatus in congenital simple ectopia lentis.

One normal and one ectopic lens have been examined with scanning and transmission electron microscopy. Some areas of the Jens from the abnormal eye were completely devoid of zonular threads while some irregular remnants were present in other areas. The ultrastructure of the capsula propria was essentially identical to the ultrastructure seen in a normal lens. The granular inclusions found in the anterior lens capsule are probably not a part of the zonular apparatus.

SPONTANEOUS PNEUMOTHORAX AND PULMONARY DISEASE IN THE MARFAN SYNDROME. REPORT OF TWO CASES AND REVIEW OF THE LITERATURE.

Case Studies1 June 1965Spontaneous Pneumothorax and Pulmonary Disease in the Marfan SyndromeReport of Two Cases and Review of the LiteratureEDWARD M. DWYER JR., M.D., FRANK TRONCALE, M.D.EDWARD M. DWYER JR., M.D.Search for more papers by this author, FRANK TRONCALE, M.D.Search for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-62-6-1285 SectionsAboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail ExcerptThe Marfan syndrome is a rare but well-defined hereditary disorder of connective tissue (1). Prominent features of the syndrome include abnormalities of the skeletal, cardiovascular, and ocular systems that are manifested as either a congenital anomaly (microphakia, coarctation of the aorta) or a degenerative lesion of elastic tissue (aortic dissection, ectopic lens, hernia). Lesser known areas of involvement are renal (2, 3), dermatologic (4), and pulmonary. The spectrum of pulmonary lesions in the Marfan syndrome includes congenital malformations, cystic disease, emphysema, spontaneous pneumothorax, and susceptibility to respiratory infections. In spite of several recent reports (5-7), the etiology, pathogenesis, and pathology...

Developmental abnormalities in the head region of the talpid3 mutant of the fowl

ABSTRACT The inherited abnormality talpid3 in the fowl causes embryonic death on or before the 14th day of incubation, and developmental defects have been observed to appear on the 2nd day. Abnormalities in the head region include a tendency for the eyes to be drawn together in the mid-line, and absence of the upper beak. Rathke’s pouch is abnormal or absent, and in some cases ectopic lenses are produced within the head. Multiple epiphyseal structures are produced from the roof and abnormal ventral evaginations from the floor of the diencephalon. The developmental interrelations of these abnormalities are described, and the possible nature of the basic developmental disturbance isdiscussed. The production of extraocular lens tissue is discussed in the light of information on lens induction in normal embryos.

CONGENITAL BILATERAL SUBLUXATION OF THE LENS

Partial dislocation of the lens presents a definite problem both for the patient and for the surgeon. Recently, Clapp 1 reported on a family with ectopic lenses in which 8 out of 11 children showed this defect. Burch 2 gave a rather complete report of cases of ectopia of the lens, in some of which the additional feature of arachnodactyly was presented. Attempts to improve vision in cases of partial dislocation of the lens frequently have met with failure. Clarke 3 expressed the opinion that the best treatment was removal of the lens. This usually involves the use of a loop, with more or less loss of vitreous, as pointed out by Duke-Elder. 4 Knapp 5 stated the belief that the most satisfactory way to remove the lens is by needling—two needles being used, one to impale the lens and the other to produce a rent in its capsule.

A Report on a Family with Ectopic Lenses

A Report on a Family with Ectopic Lenses

OPERATIVE TREATMENT OF CONGENITAL SUBLUXATION OF THE LENS

Congenitally ectopic lenses need no treatment as long as the vision can be brought up sufficiently by refractive correction through the lens or through the aphakic area. Vision through the lens is generally impossible to correct, because of the deformity of the lens and the marked astigmatism. The correction through the aphakic portion of the pupil depends on the size of this area. It frequently is insufficient. The subluxation of the lens may remain stationary, giving rise to no symptoms beyond the loss of vision; the ectopia may increase in later years, allowing better vision, or total dislocation may occur. More frequently, however, the condition gives rise to cyclitis and glaucoma. When satisfactory vision in a congenitally subluxated lens cannot be obtained by refractive means, operation is indicated. The operations that come under consideration are iridectomy and discission. A satisfactory iridectomy is not easy to perform and does not prevent