Base-out Research Articles

Role of botulinum toxin A in surgically overcorrected exotropia

Purpose: The purpose of this study was to define the role of botulinum toxin type A (BTXA) in surgically overcorrected exotropia. Methods: A retrospective review was performed using the BTXA clinic database of more than 3500 patients to identify patients with a consecutive esotropia. Results: Sixty patients met the inclusion criteria; the patients' ages ranged from 5 to 80 years. Before toxin treatment, an average of 1.8 operations had been performed per patient. The mean distance deviation was 17 PD base out and near deviation was 18 PD base out. The time from the last operation to an injection of BTXA averaged 28.3 months. We divided our patient population into 2 groups: those with fusion potential and those with no expected fusion potential. Of the 36 patients with fusion potential, 15 patients achieved and maintained good ocular alignment and resolution of their diplopia with an injection of BTXA. In the 24 patients with no expected fusion potential, 4 patients (17%) achieved and maintained good alignment with an injection of BTXA. Although they were not cured, 10 additional patients chose to have repeated BTXA injections to maintain their ocular alignment, whereas only 2 patients required occlusive methods to eradicate intractable diplopia. Five patients had additional surgery, of which 3 patients obtained a functional result. Conclusions: BTXA has a role in surgically overcorrected exotropia for patients in whom a functional result may be obtained. BTXA is of less value for patients with poor binocular function. It has proved especially useful as a treatment given only once for 42% of patients who could regain high-quality stereopsis. The safety and ease of administration of this treatment add to its merit. (J AAPOS 1999;3:269-71)

Vergence facility: establishing clinical utility.

Vergence facility testing attempts to assess the ability of the fusional vergence system to respond rapidly and accurately to changing vergence demands over time [defined as the number of cycles per minute (cpm) that a stimulus can be fused through, alternating base-in (BI) and base-out (BO) prisms]. Decisions to use vergence facility as a clinical test are hampered by a lack of systematically gathered normative data. Twenty symptomatic and 20 control subjects with ages between 18 to 35 years of either sex and any race were pooled, based on vision-symptom level determined by a self-report questionnaire. Inclusion/exclusion criteria included vision correctable to 6/6 (20/20) Snellen acuity or better in each eye and normal phorias. Vergence facility response was tested over a 1-min period, using 16 combinations of BI/BO flip prisms at 4.0 and 0.4 m, based on Morgan's norms and pilot data. Horizontal vergence facility responses were not the same among those with and without symptoms, and not all magnitudes of BI/BO flip prisms produced the same response difference. A single flip prism, 3 delta BI/12 delta BO, was found to differentiate optimally between groups at distance and near. Repeatability of test results (with the 3 delta BI/12 delta BO prism) was poor at distance and good at near. In addition to providing valuable normative data, this study indicates that the vergence system nearly resets its "zero point" at any distance and sheds further light on the results of dynamic convergence and divergence stimulation on the accommodative-vergence system. From a clinical standpoint, the results improve the diagnosis of binocular vision abnormalities. The recommended near vergence facility test is easily implemented, using a commonly available flip prism (3 delta BI/12 delta BO) and having a clinical failure criterion that is easily recalled (15 cpm, sum of the BI and BO magnitudes).

Vergence facility and target type.

Target suppression-cues are considered important for valid binocular accommodative facility response. However, there are no comparable recommendations concerning the effect of target type on vergence facility response. Ten subjects ages 16 to 19 years of either sex and any race were pooled, based on the lack of any asthenopic symptoms determined by a verbal interview with the investigator. Inclusion/exclusion criteria included vision correctable to 6/6 (20/20) Snellen acuity or better in each eye, and near-normal phorias. Vergence facility response was tested over a 1-min period using 8 delta base-in (BI) and 20 delta base-out (BO) loose prisms at near (0.4 M) for 3 different vertically oriented targets: 6/9 (20/30) Snellen letters, back-illuminated anaglyphic shapes, and modified Wirt circles. For the group, the mean facility response was similar among the target types [Snellen letters: 9.5 cycles per minute (cpm) +/- 5.6; anaglyphic shapes: 9.0 cpm +/- 6.3; and Wirt circles: 9.4 cpm +/- 4.5]. Group response-differences were not significantly different by one-way ANOVA polynomial regression testing at the 0.05 level (F-value = 0.03, p = 0.97, df = 2). Whereas a binocular accommodative facility target must have additional vectographic or anaglyphic suppression-cues, vergence facility testing may incorporate a simple and available vertical row of 6/9 (20/30) Snellen letters, which provide inherent fusional suppression-cues, for a valid binocular response.

The mechanism of bacteriorhodopsin functioning. II. Ejection and injection of proton

AbstractTransmission of vibrational excitation energy conserved in cis‐conformation of retinal to the outlet proton channel is considered from the perspective of quantum theory. A distribution of vibrational excitations in the channel is found; it allowed to calculate the magnitude of the directed drift proton current. The differences between velocities of proton movement in active and passive channels are considered. A transition of retinal from cis‐ to all ‐trans‐ conformation with the subsequent capture of proton by Schiff base out of the inlet channel is described. The lack of proton in this channel, i.e., in the H‐bonded chain, is eliminated at the expense of the capture of a proton out of the cytoplasmic water enviroment. The correspondence between theoretically established states and spectroscopically identified forms of bacteriorhodopsin (inter‐mediates L, M, N, and O) is proposed.

Effect of a central fusion stimulus on fixation disparity.

Fixation disparity (FD) measurements were made with a 1.5 degree diameter fusional stimulus both with and without a central fusion stimulus. Measurements were made at 40 cm with no prism, 5 delta base-in (BI) and base-out (BO), and 10 delta BI and BO, on a group of asymptomatic subjects. The central fusion stimulus results in less variable measurements and a flatter slope of the fixation disparity curve (FDC). Implications of the use of the central stimulus for clinical measurements are discussed.

The Use of Aerial Photographs for Geological Exploration and Detailed Mapping in Regions of Low Dip: ABSTRACT

Linears (linear arrangements of drainage lines) many miles in length are common in the plains and low-strata-bench-lands, and are frequently aligned with deep-seated faults, flexures, and synclines. They may be useful in locating buried anticlines of regional size that are not otherwise visible. They may assist the geomorphologist and aero-geologist in the proper interpretation of geomorphic features, such as hogbacks, cuestas, consequent streams, angular or trellis drainage, etc., by means of the stereoscopic study of aerial photos. They themselves, however, are hardly to be classed with such features. They, no doubt, represent the effects of erosion and repeated slight movements along pre-Cambrian faults, and are more regional in scope than ordinary geomorphic feature . Aerial photographs may be studied stereoscopically for a number of reasons which may or may not include associated field work. They have justified their use for many purposes. Their most rewarding use in the flat-lands is for discovery of hitherto unknown structures. Though it is difficult, if not impossible, in the continental United States to find large structures not hitherto known to someone, many structures of smaller size have been discovered by use of aerial photos. Prismatic and magnifying spectacles are preferred for geological study in the plains regions, the prismatic correction varying from 2 to 5 diopters, base out. The smaller prism is useful for strike and dip determinations and makes it possible to recognize dips as low as one-third of one degree. The larger prism is better for tracing resistant beds. The magnification found most useful by the writer is ½ of one diameter. In plains regions the problem of securing aerial photographs that are good enough for use by geologists is one that requires special knowledge and experience. The 7-inch by 9-inch vertical photos with which most of the United States was photographed 10-15 years ago by the U. S. Department of Agriculture are better for geological purposes than the 9-inch by 9-inch photos now being made. The lens focal-length of 8¼ inches is barely long enough; a 10- or 12-inch focal-length would be much better for dip determinations. Photos made with a 4-inch focal-length are practically worthless. The flight photo-scale of 3.1 inches per mile, being used by the Department of Agriculture, is much to be preferred to scales of less than 2 inches per mile, which are usually employed by the U. S. Geol gical Survey and some private aerial photographers. The Geological Survey, being, no doubt, aware of the needs of geologists, will presumably one day take the lead in the choice of suitable flight-scale, focal-length, and size of aerial photographs. Aerial photographers who try to sell geologists vertical photos where a square mile is approximately the size of a 3-cent postage stamp are, in effect, presuming that drainage is much more significant than it really is in the discovery of geological structure anomalies. Photo-enlargements made from these small-scale negatives are seldom very useful either, because of the lack of sufficiently sharp definition in the outcropping beds. End_of_Article - Last_Page 2609------------

The Opticians' Dispensing Manual.

While this book is intended primarily for those who are concerned with the grinding of lenses and the fitting and sale of various types of lenses and frames, it contains much information with which the ophthalmologist should have at least a cursory acquaintance. Moreover, as the author states in his preface, his theories can be applied with merely the aid of a pencil, cardboard, a caliper and a ruler. The first chapters deal with Oxfords, spectacles and the adjusting of frames. While Mr. Hartinger seems overly fond of Oxfords, he is not unnecessarily prejudiced in their favor. The chapters on lenses, transpositions and bifocals are of especial value, particularly those in which he mentions some impossible prescriptions that are received, such as decentering a cylinder with a horizontal axis to obtain the effect of a prism base in or base out. His chapter on transposition of compound lenses