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PubMed2001

Preoperative intradermal acupuncture reduces postoperative pain, nausea and vomiting, analgesic requirement, and sympathoadrenal responses.

BACKGROUND: In a controlled and double-blind study, the authors tested the hypothesis that preoperative insertion of intradermal needles at acupoints 2.5 cm from the spinal vertebrae (bladder meridian) provide satisfactory postoperative analgesia. METHODS: The authors enrolled patients scheduled for elective upper and lower abdominal surgery. Before anesthesia, patients undergoing each type of surgery were randomly assigned to one of two groups: acupuncture (n = 50 and n = 39 for upper and lower abdominal surgery, respectively) or control (n = 48 and n = 38 for upper and lower abdominal surgery, respectively). In the acupuncture group, intradermal needles were inserted to the left and right of bladder meridian 18-24 and 20-26 in upper and lower abdominal surgery before induction of anesthesia, respectively. Postoperative analgesia was maintained with epidural morphine and bolus doses of intravenous morphine. Consumption of intravenous morphine was recorded. Incisional pain at rest and during coughing and deep visceral pain were recorded during recovery and for 4 days thereafter on a four-point verbal rating scale. We also evaluated time-dependent changes in plasma concentrations of cortisol and catecholamines. RESULTS: Starting from the recovery room, intradermal acupuncture increased the fraction of patients with good pain relief as compared with the control (P < 0.05). Consumption of supplemental intravenous morphine was reduced 50%, and the incidence of postoperative nausea was reduced 20-30% in the acupuncture patients who had undergone either upper or lower abdominal surgery (P < 0.01). Plasma cortisol and epinephrine concentrations were reduced 30-50% in the acupuncture group during recovery and on the first postoperative day (P < 0.01). CONCLUSION: Preoperative insertion of intradermal needles reduces postoperative pain, the analgesic requirement, and opioid-related side effects after both upper and lower abdominal surgery. Acupuncture analgesia also reduces the activation of the sympathoadrenal system that normally accompanies surgery.

Abdomen↗

PubMed2001

The thalamus interrupts top-down attentional control for permitting exploratory shiftings to sensory signals.

When attention is involuntarily drawn in a direction different to that of the target, slower motor response times are observed (i.e. the meridian effect). Previous data suggested that the thalamus might participate in the generation of visual salience. What may be the role of the thalamus in the capture by luminance transients when attentional control is in action? A single experiment was administrated in a group of ten healthy volunteers as well as in a group of three patients with unilateral thalamic infarcts. Subjects participated in a task where attentional control was interrupted by a distractor. The meridian effect was present only in the performance of the healthy volunteers and when distractors occurred in the ipsilesional (intact) hemifield of the thalamic patients. These results suggest that when an important signal appears during attentional focalization, the thalamus interrupts current focalization and permits the compilation of an attentional program in the midbrain aiming at generating an orienting response towards the source of this signal.

Adult↗

PubMed2001

Gender- and age-related differences in corneal topography.

PURPOSE: To investigate gender- and age-related differences in the corneal topography of a normal population. METHODS: One hundred thirty-two topographic examinations were collected from 100 patients ranging in age from 23 to 83 years (average, 57.35+/-17.38 years). Data were segregated by gender and further divided into younger (less than 50 years) and older (50 years or more) age groups. The topographic indices of Surface Regularity Index, Surface Asymmetry Index, Irregular Astigmatism Index, Standard Deviation of Corneal Power, Corneal Eccentricity Index, Coefficient of Variation of Corneal Power, Simulated Keratometry 1 and 2, and Average Corneal Power were examined. The astigmatism pattern and corneal irregularity were determined and compared with respect to gender and age. RESULTS: The corneas of older men were flatter than those of older women (p < 0.001). The vertical corneal meridian, but not the horizontal meridian, showed statistically significant gender-related changes with aging (p < 0.001). Older men had a significantly higher potential for against-the-rule astigmatism than women (p < 0.001). Corneal irregularity (measured in terms of the Surface Regularity Index and Irregular Astigmatism Index) increased with age (p < 0.001 and p < 0.001, respectively), although there was no gender-related difference. In the younger group, no gender-related differences in corneal curvature or astigmatism pattern were found. CONCLUSION: Aging influences changes in patterns of astigmatism differently in men and women. Decreases in levels of sex hormones may play a role in gender-related changes in corneal structure with age.

Adult↗

PubMed2002

Evaluation of a microkeratome-based limbal harvester device for limbal stem cell transplantation.

PURPOSE: To assess the cut quality and reproducibility using a novel microkeratome-based limbal harvester. METHODS: An enlarged microkeratome head and stainless steel blades were coupled with a nitrogen gas-driven turbine (15,000 blade oscillations/min) of a microkeratome. A large, 16-mm-diameter suction ring was attached to the globe. A lamellar sclerokeratectomy using head depths of 170 and 200 microm was performed in human donor research eyes. Obtained lenticule thickness was measured by ultrasound pachymetry and the bed size by planimetry. Histologic and scanning electron microscopy (SEM) analyses of the samples were performed. RESULTS: Central lenticule thickness was 294 microm (standard deviation [SD] 37) for the 170 head and 277 microm (SD 91) for the 200 head (p = 0.720). Lenticule diameter was larger in the horizontal meridian using the 170 head (12.8 mm [SD 0.8] vs. 11.9 mm [SD 0.7], p = 0.028), but similar in vertical meridian (12.0 [SD 0.6] versus 11.4 mm [SD 0.6], p = 0.093). Histology showed a multilayer epithelial cell pattern at the lenticule periphery. The SEM showed a smooth cut surface in both the stromal bed and the lenticule. CONCLUSION: Cut reproducibility and quality are similar to those found using standard microkeratomes for corneal lamellar cuts. This system ensures, in a straightforward way, the presence of epithelial cells in the edges of a mechanical sclerokeratectomy for limbal stem cell transplantation.

Aged↗

PubMed1976

Aberrations of spherocylindrical spectacle lenses.

A procedure has been developed for tracing a bundle of rays through and ophthalmic lens and a schematic eye with its primary line of sight pointed through various parts of the lens. A bundle of eight rays can provide data for assessing the quality of the image formed by such a system. To test the procedure and to generate data which can help in selecting a method for evaluating image quality, we selected a single lens as an example. The lens selected has a spherical back surface (-5.00 diopters) and a toric front surface (+15.00 diopters in the vertical and /10.00 diopters in the horizontal). It has a center thickness of 5 mm and glass of index 1.523. Spot diagrams were generated with the eye pointed in various directions through the ophthalmic lens. The data generated showed that peripheral bundles which fall between the principal meridians emerge as astigmatic bundles. This leads to the proposal that blur circle theory can be used for evaluating the quality of the optical image and that it suffices in the case of a spherocylindrical ophthalmic lens to base the tolerances for refractive power on measurements made in the principal meridians.

Astigmatism↗

PubMed1976

Validity of the laser refraction technique for meridional measurement.

This study assessed the validity of the laser refraction technique for determining the refractive status of a given meridian of the eye. A subjective-to-BVA finding was taken on a total of 75 eyes, and the laser technique was then used to refract each of the 2 principal meridians that had been located by the subjective procedure. Correlations between laser and nonlaser findings indicated that the laser technique is a valid method for meridional refraction. Differential findings for against-the-rule astigmatism are also discussed.

Female↗

PubMed1980

The effects of astigmatism on sensitivity to sinusoidal and square wave gratings.

Contrast thresholds for different spatial frequencies were measured for four individuals with optimum optical correction and with 2 D of astigmatism induced at various meridians. Sensitivity for sine waves of low spatial frequencies was unaffected by the astigmatism; however, gross changes were found at high spatial frequencies when the astigmatism was induced with the power meridian perpendicular to the orientation of the stripes. For square waves, the results were comparable at high spatial frequencies, but astigmatism also produced a decrement at 0.2 cycles/degree. This latter effect can be predicted by assuming that astigmatism results in a loss of higher order harmonics in the response to square waves.

Astigmatism↗

PubMed1981

A longitudinal study of corneal astigmatism and total astigmatism.

Cross-sectional studies indicate that mean total astigmatism changes with age; varying from as much as 0.62 D with-the-rule during youth to as much as 0.37 D against-the-rule in samples of elderly patients. The present study involves the examination of adult patients who were seen regularly for a period of at least 40 years. Data are analyzed to determine whether the change in corneal astigmatism accounts for the total astigmatic change, and the magnitude of change with age at each of the principal corneal meridians. Results indicate that steepening of the cornea in the horizontal meridian accounts for a major portion of the increase in against-the-rule total astigmatism among older patients.

Adolescent↗

PubMed1981

The ratio of the size of the optic cup (as determined by the place where the vessels deviate) to size of the disc.

The vessel deviation to disc ratio (VDR) of the optic nerve head can be defined for a given meridian as the ratio of the size of the cup as indicated by small blood vessel deviation in that meridian to the size of the disc. Thus, VDR is a relative measure similar to cup/disc ratio. The difference between VDR and other methods of measuring cup/disc ratio is that the former identifies the rim of the cup with the deviation or bending of the small blood vessels as they fan out over the disc, whereas the latter determine the location by the other criteria which vary from examiner to examiner. The purpose of this study is to quantify the variation in VDR and its relation to age, refractive error, and sex.

Adolescent↗

PubMed1987

Corneal apex in keratoconic patients.

Eyes of 27 patients with keratoconus and 37 normal persons were examined with a photokeratoscope. The photokeratoscopic data were analyzed to obtain information about the corneal apex and a comparison between the two groups was performed. The study demonstrates a significant shift in the position of the corneal apex in relation to the visual axis from a superior-temporal position in the normal group to an inferior position without temporal-nasal preference in the keratoconic group. However, the magnitude of the apex displacement (lxa) was equal in the two groups both in the horizontal and vertical direction. The influence of xa on the stability of the central corneal curvature was established by the apex factor (AF). The magnitude of AF depends as well on xa as the corneal shape. In the keratoconic eyes the vertical AF is about 5 times the horizontal AF, whereas in normal eyes the AF is equal in the two meridians. Thus the increasing astigmatism so characteristic for the keratoconic eyes may be caused by unequal alteration in the shape of the horizontal and vertical meridians.

Adolescent↗

PubMed1988

Ocular effects of hard gas-permeable-lens extended wear.

Thirty-five myopic subjects were fitted with rigid gas-permeable lenses for 6 months of extended wear (EW). These lenses had an average oxygen transmissibility of 37 x 10(-9) (cm x ml x O2)/(s x ml x mm Hg). For six monthly morning visits subjects reported with one eye patched; corneal thickness, corneal curvature, refractive error, endothelial photomicroscopy, and slitlamp examinations were done on both eyes. The average morning corneal swelling was 5.9 +/- 3.3%. Corneal curvature showed 0.24 +/- 0.44 D flattening in the steep meridian and 0.20 D steepening in the flat meridian. Spectacle refraction and corrected visual acuity changes were small in the spherical and cylindrical components. Complications that were important clinically included 10% lens adherence syndrome, 20% superficial limbal keratitis, 6.5% epithelial microcysts, and some increase in endothelial polymegathism. No infections, red eye responses, or infiltrative keratitis were observed during the 6-month follow-up period. These results suggest that hard-lens EW is feasible and that lenses with this Dk/L value will meet oxygen requirements for many patients; however, some patients will require lenses of higher oxygen transmissibility to avoid undesirable complications.

Cell Count↗

PubMed1989

Correcting astigmatism.

Measurement of refraction in the principal meridians and off-axis meridians in both directions from the visual axis was undertaken. The extent of disagreement between the sine-squared law and the actual astigmatism of living astigmatic eyes was calculated. The corrected visual acuity correlates with the residual ametropia. The conoid of Sturm is not the same for each eye.

Astigmatism↗

PubMed1989

Meridional analysis of with-the-rule astigmatism in Oklahoma Indians.

Refraction and keratometry records were obtained for 142 consecutive with-the-rule astigmats and for 100 consecutive nonastigmats from W. W. Hastings Indian Health Service Hospital in Tahlequah, Oklahoma. Patients were 5 to 40 years of age. Patients with higher degrees of Indian ancestry were more common in the astigmatic group than in the spherical refraction group. An analysis of refractive error and keratometry by principal meridian was performed. The horizontal meridian refractive error in astigmats was most often near emmetropia. Compound myopic astigmatism and mixed astigmatism accounted for over 3/4 of the cases. The astigmats as a group had flatter corneas in the horizontal and steeper corneas in the vertical than the nonastigmats. Horizontal refractive errors and horizontal keratometry readings showed a weak but significant correlation in astigmats but not in nonastigmats.

Adolescent↗

PubMed1990

Effect of induced dynamic aniseikonia on fixation performance during oblique gaze.

This is a sequel to other papers dealing with the effect of induced aniseikonia and optical anisophoria on fixation eccentricity during bifixation. To stimulate the effect of induced anisophoria, controlled amounts of differential prism were induced in the vertical meridian. At the same time, stimuli were presented at various angles from the subject's straight ahead orientation. As demonstrated in other studies, it was found that a vertical prismatic difference will cause the eyes to fixate slightly eccentrically in the horizontal meridian. The eccentricity was measured with the border enhancement method, described and tested in other studies. In addition, it was found that the fixation deviation is increased further by oblique gaze, the greatest obliquity having the greatest effect. It was also found that whereas short-term adaptation reduces the prism effect somewhat, it has less influence on the effect of oblique gaze. In general, the study demonstrates the potential oculomotor problems inherent in optical anisophoria.

Adaptation, Ocular↗

PubMed1992

New developments in the application of the multimeridional apparent frontoparallel plane.

This study is a sequel to a previous publication that introduced the multimeridional apparent frontoparallel plane (MAFPP) as a method of measuring aniseikonia. As the term implies, apparent frontoparallel plane (AFPP) responses are obtained not only in the horizontal meridian, but also in oblique meridians. Since the introductory publication, the method has been applied extensively for measuring aniseikonia and has been found to be reliable, accurate, and easily adapted to clinical purposes. This study presents a more detailed and comprehensive account of the underlying theory than did the introductory report. It clarifies some problems inherent in the method originally presented and describes a simplified and improved procedure for measuring aniseikonia. It describes the application of the theory to a number of specific clinical situations. Finally, it is suggested that the method has a much broader application than the clinical measurement of aniseikonia.

Aniseikonia↗

PubMed1992

Multimeridional apparent frontoparallel plane: relation between stimulus orientation angle and compensating tilt angle.

The classical apparent frontoparallel plane (AFPP) setting is typically obtained by having the subject move a series of parallel rods farther or closer until they line up in a plane perceived to be parallel to the face plane. If there is a size difference between the two ocular images, the AFPP setting defined by the rods will exhibit a tilt from the objective frontoparallel plane, about an axis parallel to the rods. The multimeridional apparent frontoparallel plane (MAFPP) is an extension of this procedure to rod orientations other than the vertical meridian. In previous studies, it was found that oblique tilt angle settings corresponding to rod orientations of 45 degrees and 135 degrees are equal to square root 2 times the tilt angle for the vertical rod orientation for the same interocular magnification difference along the meridian perpendicular to the rods. In this study, we measured the tilt angles produced by a series of oblique rod orientations between 15 degrees and 165 degrees, inclusive. Throughout the 150 degrees range tested, the tilt angles were found to be consistently proportional to the cosecant of the rod orientation angle, the factor square root 2 previously used being a specific example of this relation. Within this range, neither empirical cues nor the induced effect cause the cosecant relation to break down. It is suggested that the MAFPP procedure can be applied more extensively than previously anticipated.

Aniseikonia↗

PubMed1993

Effects of early diabetic retinopathy on rod system sensitivity.

Previous studies have shown that S-cone pathway sensitivity is selectively decreased in the early stages of diabetic retinopathy. In the present study, rod system sensitivity was evaluated in a group of diabetic patients using psychophysical techniques. The course of dark adaptation was first determined, then absolute thresholds were measured in the horizontal and vertical meridians. For all patients, although the recovery of the initial portions of rod dark adaptation were normal, absolute thresholds were increased in both the horizontal and vertical meridians. The findings provide evidence that patients with early diabetic retinopathy show a generalized dysfunction of the rod system.

Adult↗

PubMed1995

Clinical findings before the onset of myopia in youth. I. Ocular optical components.

PURPOSE: A study was conducted to identify variables that were different in children who were emmetropic and became myopic and in children who remained emmetropic. METHODS: A cohort of initially emmetropic children had eye and vision examinations at 6-month intervals for a period of 3 years. Ocular optical components were measured by keratometry and ultrasonography. Crystalline lens power was calculated using Bennett's formulas. RESULTS: There was a tendency for keratometer power of both principal meridians to be greater in the became-myopic group than in the remained-emmetropic group. Axial length to corneal radius (AL/CR) ratio was significantly greater in the became-myopic group than in the remained-emmetropic group. The variable with the highest sensitivity and specificity was the AL/CR ratio using the horizontal meridian corneal radius. CONCLUSIONS: Greater corneal powers and greater AL/CR ratios are risk factors for youth onset myopia.

Adolescent↗