American journal of optometry and physiological optics最新文献

Convergence insufficiency (CI) is a well-known syndrome of binocular visual dysfunction. In a review of 58 papers, considerable variation was noted in the criteria used to define the condition. Symptoms and decreased positive fusional vergences (both at the nearpoint) were the only criteria named in more than one-half of the studies. An extended nearpoint of convergence (NPC) and increased exophoria at near were criteria in about one-third of the papers. Examination of data in the reviewed papers shows that although considerable variability was noted, the distance exodeviation, distance negative vergences, visual acuity, refraction, and stereopsis were about the same as population norms. Positive vergences, negative vergence at near, and NPC were somewhat less than population norms. Vergences relative to Sheard's criterion, the near exophoria, accommodative amplitude, and the AC/A ratio were consistently below those derived from population norms. This considerable variation may largely be a result of different criteria used for diagnosis, subpopulations within the data, and other confounding factors.

The etiology of keratoconus is still unknown. This project was designed to study, in a group of keratoconic patients and a control group, the following: clinical, endocrinological, immunological, psychological, and ophthalmological factors. We found mean serum magnesium deficiency and type A behavior to be significantly more common in keratoconic patients than in a control group of patients. In addition changes in gluco-mineral corticoids, changes in glucose metabolism, edema of allergic origin, and genetic factors may collaborate in the development of keratoconus. All these factors could affect the osmotic mechanism of the cornea: Na-K and/or Ca ATPase, the collagen structure by alteration of the adenylate cyclase activity, and other mechanisms. This study suggests an association between keratoconus, magnesium depletion, and type A behavior, which together constitute a new clinical syndrome and confirm an association between keratoconus and atopy.

Traditional vision training or orthoptics has used line or contour targets to eliminate suppression and improve vergence performance. Manipulation of these stimuli is slow and arduous. Line stimuli require an experienced doctor/technician to interpret responses. Recently, automated vision training using microprocessor anaglyph stimuli, i.e., random dot stereograms (RDS), has been used in an operant conditioning paradigm. This technique has improved motivation of the patient, improved reliability, and provided standardization of therapy. In addition, the utilization of RDS associated with operant conditioning has been shown to improve vergence performance and to reduce asthenopia in the convergence insufficiency patient.

A nondestructive method of constructing the three-dimensional refractive index profile of crystalline lenses is presented. The technique is based on earlier work in which the refractive index profile is deduced from measuring the refraction of a set of light rays that traverse the lens in a particular plane. However, the present approach requires fewer assumptions about the form of the refractive index profile so that the deduced results are less likely to reflect preconceived notions about the form of the refractive index distribution. An accurate model for the bovine crystalline lens has been constructed with the present approach. Without further adjustable parameters, our three-dimensional model of the lens refractive index profile is able to predict accurately the refraction of meridional rays that traverse the lens in the sagittal plane. Preliminary data on human lenses are also presented.

This paper is a review of the literature relative to treatment results for convergence insufficiency utilizing vision therapy training procedures. Vision therapy is shown to improve the nearpoint of convergence and fusional convergence and to ameliorate associated symptoms. The overall cure rate is 72%. Furthermore, the training results appear to persist for at least 2 years if the patients are initially cured and are independent of age until the late presbyopic years. Also, recent studies indicate the type of training procedures which yield the most effective training results.

Broca's pupillometer offers a simple and effective means of measuring the diameter of the pupil. However, it is often used without proper attention to the limitations of its optics. Errors of measurement may result from uncorrected refractive error, accommodation, spectacle correction, and spherical aberration (SA). A simple means of minimizing these errors is to hold the pinholes (PH's) of the pupillometer as close to the cornea as is feasible.