Catálogo de publicaciones - libros

After fertilization of the ovum within the uterine tube, cellular mitosis results in formation of a ball of 12 to 16 cells, the morula. A fluid-filled cavity within this embryonic cell mass forms, resulting in a transformation into a blastocyst that begins to penetrate the uterine mucosa on approximately the sixth day postfertilization. The cells of the blastocyst continue to divide with the cells of the future embryo proper (embryoblast) accumulating at one pole. The cells of the primitive embryoblast differentiate into two layers,the epiblast and the hypoblast. These two cellular layers bridge the central cavity of the blastocyst, thus dividing the blastocyst into the amniotic cavity and the yolk sac (Fig.1-1).

This chapter highlights the areas of the eye examination that are of significance in assessing pediatric neuro-ophthalmic disorders. Before beginning the formal examination, spend a few moments interacting with the child in a nonthreatening way. Gaining the child’s confidence early in the exam will be rewarded later when cooperation is imperative. A great deal of information can be gathered by simple observation and, therefore, surveillance for subtle findings should be maintained during the exam. After establishing rapport with the child, the order in which information is collected depends on the conditions of the examination and the cooperation of the child. Rigid adherence to a particular regimen may lead to a frustrating experience. It is fruitless to begin taking a long, detailed history if it is obvious that the child is already somewhat fussy and rapidly losing attention. In such circumstances, the exam will have to be goal directed. By prioritizing the examination to fit the “problem,” the maximum amount of information can be obtained in what often turns out to be a very limited amount of time.

The American Academy of Pediatrics states that 75% of learning during the early years is processed through vision; because vision is a learning sense,children with visual impairment may not learn to perform many tasks as quickly as those with normal vision. Children with subnormal vision often look and act like any other child in the classroom and on the playground making it difficult to distinguish them from normally sighted children. Children with low vision may wear thick glasses or even dark glasses, but they will run and jump as fearlessly as their playmates.

Janet and Marc thought their life was as close to perfection as any family’s life could be. Married for 8 years, they had one daughter, Missy, age 5, and Brian, age 3 months, their long-awaited son. At Brian’s 3-month routine well-baby checkup, the pediatrician remarked that Brian might have strabismus because his eyes appeared to turn in and weren’t “working together,” as Janet later described it. The pediatrician was very reassuring, however, and told Marc and Janet that he would like the baby to be examined by a pediatric ophthalmologist “just to be on the safe side.” Marc had recently started a new and more responsible job so it was decided that Janet would take Brian for the eye examination herself, to minimize the amount of time Marc was away from the office.

Normal individuals and most patients with common concomitant childhood strabismus have full ocular rotations (versions and ductions). This chapter is devoted to some of the more frequently encountered childhood disorders of the central and peripheral nervous systems, neuromuscular junction, and extraocular muscles that appear clinically to have incomitant ocular misalignments.

The ophthalmologist is frequently called upon to evaluate infants and children with decreased vision related to congenital abnormalities of the optic nerve. Such evaluation necessitates a detailed understanding of the ophthalmoscopic features, associated neuro-ophthalmic findings, current theories of pathogenesis, and appropriate ancillary studies in each condition. This chapter examines congenital optic nerve abnormalities, discusses current controversies surrounding their pathogeneses, and reviews associated neuroradiologic findings that may predicate the general medical management of affected patients.

(CVI)is the most common cause of bilateral visual impairment in children in the developed world. In less-affluent countries, the incidence is increasing because the survival rate of premature babies is improving. As a consequence, the mortality of children with complex medical problems has begun to decline. Retinopathy of prematurity (ROP) is also a major cause of visual handicap: its rate is increasing, and it may become the commonest cause of visual impairment in children. A risk factor for CVI is prematurity, which is also a risk for ROP. Thus, these two disease processes often coexist.

Abnormalities of the brain often manifest with problems of either the afferent or efferent visual systems. Many of the disorders discussed in this chapter portend a guarded prognosis and often require urgent or even emergent therapy. This chapter discusses congenital abnormalities of brain development, hydrocephalus, infections, and tumor. The importance of the ophthalmologic examination in each of these clinical settings cannot be overestimated. For example, one-half of intracranial tumors present with ocular signs or symptoms. Thus, the physician must maintain a high index of suspicion that an abnormality that varies from the typical appearance of amblyopia or strabismus might be produced by intracranial abnormalities.

Eye care practitioners may be among the first to evaluate infants and children with involuntary ocular movements. Pediatric ophthalmologists may, in fact, see more patients with nystagmus than any other specialist because of the frequent association of nystagmus with strabismus. Nystagmus may be covered less frequently in literature and research because there is less we understand or can do about it, compared to strabismus or other childhood eye diseases.

The pediatric ophthalmologist is frequently asked to evaluate children with multiple neurological impairments for ophthalmic manifestations of heritable neurological diseases. Occasionally these are diseases with specific ocular findings such as Kayser-Fleischer rings in Wilson’s disease or cherry-red spots in Tay-Sachs disease. More typically, they are diseases with non-specific findings such as optic atrophy or nystagmus. Such findings can be used to help direct the neurological workup. Less commonly, these children present to the ophthalmologist with ocular complaints primarily. The ophthalmologist must recognize those signs and symptoms that may be associated with neurodegenerative conditions and institute an appropriate workup. Although all these conditions are rare, a general ophthalmologist is likely to encounter several of them in their career.