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PubMed1998

Validation of a handheld automated keratometer in adults.

PURPOSE: To evaluate the Nidek handheld automated keratometer and compare it with the manual Zeiss keratometer. SETTING: St. Paul's Eye Unit, Royal Liverpool University Hospital, Liverpool, United Kingdom. METHODS: Forty-five normal adult volunteers were included in the study. Three sets of randomized keratometry measurements were taken from both eyes of each adult, with both instruments by two independent observers. Readings included powers of the steep and flat meridians and axis of the flat meridian. The mean difference between the two instruments was calculated. The variance of each instrument was calculated for the axis, the steep and flat meridians, and the mean of the two meridians. RESULTS: There was no significant difference between the mean Nidek and Zeiss keratometry readings for the steep (0.015 mm; P = .167) or flat (0.054 mm; P = .069) meridian or axis measurements (P = .172). On repeated measurements, the within-subject and within-group variabilities, calculated separately for each instrument, were significantly less for the Nidek automated keratometer than the Zeiss keratometer (P < .01) when measuring the steep and flat meridians. There was however, a significant increase in axis variability using the Nidek keratometer (range 20 degrees; P < .01). CONCLUSION: The Nidek automated keratometer was accurate, reliable, and easy to use and compared favorably with the manual Zeiss keratometer when measuring corneal curvature. In the handheld mode, the Nidek is not suitable for axis measurements. It has the additional advantage of portability.

Adult↗
PubMed1993

Clinical and anatomical study of the effect of transscleral fixation of posterior chamber lenses on early postkeratoplasty astigmatism.

We reviewed the pattern of astigmatism after penetrating keratoplasty and transsclerally sutured posterior chamber lens (TSPCL) placement in 73 patients. Thirty-five patients (48%) had an axis of astigmatism oriented perpendicularly to the haptics of the TSPCL. Twenty-seven patients (37%) had an orientation of astigmatism that was in the same meridian of the haptics of the TSPCL. Eleven patients (15%) had an axis of astigmatism oriented obliquely to the meridian of the haptics of the TSPCL. The distance the haptic fixation sutures were placed behind the limbus appeared to be correlated with the orientation of astigmatism. Patients having the lens fixated within 0.75 mm of the limbus were more likely to have astigmatism oriented perpendicular to the meridian of the haptics of the posterior chamber lens in the early postoperative period. Patients having the lens fixated 2-3 mm posterior to the limbus were more likely to have astigmatism oriented in the same meridian as the haptics of the posterior chamber lens in the early postoperative period. In an eye bank model of TSPCLs during penetrating keratoplasty, the placement of a posterior chamber lens with haptics fixated within 0.75 mm of the limbus significantly widens the recipient bed an average of 0.3 mm in the meridian of the haptics of lens placement (p = 0.02). When the posterior chamber lens haptics were fixated 3 mm posterior to the limbus, the recipient bed was significantly narrowed in the meridian of lens placement an average of 0.2 mm (p = 0.02). It appears that the TSPCLs may have an effect on early postkeratoplasty astigmatism by distorting the corneal wound at the time of keratoplasty.

Aged↗
PubMed1985

Peripheral visual field is radially organized.

The visibility of vertical, horizontal, and 45 degrees oblique square wave gratings was measured at 10 to 45 degrees of eccentricity along the vertical, horizontal, and the 45 degrees oblique meridians. A forced-choice orientation identification response to the stimulus grating and a subjective rating of the confidence in response accuracy were the response measurements. The best seen grating orientation was always the one parallel to the meridian upon which it was presented. Along the vertical and horizontal meridians the most poorly seen orientation was the one perpendicular to the meridian. Along the 45 degrees oblique meridians the horizontal grating was as poorly seen as the meridian perpendicular to the grating orientation, except in the infranasal quadrant of the field. Pinhole experiments show these results unlikely to be due to off-axis optical aberrations. It is hypothesized that the radial organization of the peripheral visual field is due to underlying neural factors ontogenically determined, not due to environmental adaptations.

Form Perception↗
PubMed1991

Variability in commercial histoplasma complement fixation antigens.

Using Immuno-Mycologics (IMMY; Norman, Okla.) histoplasmal yeast (HY) and mycelial (HM) antibody complement fixation test antigens, we retested 1,386 samples that were initially tested with Meridian Diagnostics, Inc. (Cincinnati, Ohio), antigens. Histoplasma antibody was identified (greater than or equal to 1:16) in 20% of HY and 5% of HM samples reported to have titers of less than 1:8 with Meridian reagents. IMMY titers were at least fourfold higher than Meridian titers in 39% of HY and 54% of HM samples that initially had titers of greater than or equal to 1:8 with Meridian antigens. Because 30 of 58 (52%) samples from confirmed cases of histoplasmosis yielded negative results with Meridian antigens and positive results upon retesting with IMMY antigens, we concluded that the Meridian antigens had less reactivity with human histoplasmal antibody.

Antigens, Fungal↗
PubMed2000

Effect of acupuncture at Hsien-Ku (St-43) on the pulse spectrum and a discussion of the evidence for the frequency structure of Chinese medicine.

We investigated the pulse spectrum variation of the human radial artery when Hsien- Ku (St 43), an acupoint on the stomach meridian, was needled and compared the results with the acupuncture effects of two other acupoints, Tsu-San-Li (St-36) and Tai-Shih (K-3), reported previously. For Hsien-Ku, the harmonic proportions were redistributed: the second harmonic (C2) decreased, C3, C5, C6, C7, C8 and C9 increased, C3, C6 and C9 became the relative peaks to their neighboring harmonics and C2, C4 became the relative minimums. The phase angles of the 2nd harmonic (P2) and 5th harmonic (P5) decreased, propagating faster. These effects were similar to that of Tsu-San-Li which is also on the stomach meridian. A totally different pattern was found for Tai-Shih on the kidney meridian. These results strengthen the theory that a meridian can be classified according to its effects on the pulse spectrum, and that all the meridian related effects such as those caused by acupuncture or meridian specific herbs are frequency specific.

Acupuncture Therapy↗
PubMed1997

Effects of moxibustion on blood pressure and renal function in spontaneously hypertensive rats.

The aim of this study was to investigate the effects of moxibustion at the meridian points BL-15 (Xin-shu) and BL-27 (Xiao-chang-shu) on renal function, systolic blood pressure, plasma levels of renin activity, aldosterone and atrial natriuretic peptide in spontaneously hypertensive rats. The results showed that urine volume increased significantly after moxibustion at the meridian points BL-15, but decreased at BL-27. Urinary excretion of Na+ decreased after moxibustion at the meridian points BL-15 and BL-27. Systolic blood pressure decreased after moxibustion at the meridian point BL-15. No effect was observed at BL-27. Plasma levels of aldosterone and renin activity increased significantly, but the levels of atrial natriuretic peptide decreased significantly after moxibustion at BL-15. Plasma levels of aldosterone and atrial natriuretic peptide increased significantly after moxibustion at the meridian points BL-27. These results suggest that the meridian points BL-15 and BL-27 are related to the regulation of renal function and the secretion of hormone with body fluid metabolism.

Acupuncture Points↗
PubMed1998

Reliabilität der energetischen Meridianmessung mit Prognos A(R).

Reliability of Energetic Meridian Measurement with Prognos A(R) OBJECTIVE: Is energetic measurement of the Traditional Chinese medicine (TCM) meridians with Prognos A a reliable method? PATIENTS: 30 healthy volunteers from the staff of the Stauferklinik, Schwä bisch Gmü nd, Germany. DESIGN: Measuremeuts are taken 4 times from each person at all terminal locations of the meridians (24 points) on fingers and toes with Prognos A. Breaks between each measurement run lastet 2-5 min. The values of skin resistance are compared. RESULTS: Reliabilities of the single meridian measurements range between 0.44 and 0.82 with an overall reliability of 0.72. Lowest reliability is seen in yang -hollow organs, probably a due to their intense lability. Mediating of 4 single runs shows a reliability of 0.9. CONCLUSIONS: Our measurement of reliability confirms Prognos A as a reliable device of determinating skin resistance, especially with repeated measurements. Variations of the readings are probably due to the special quality of the meridian system; increased variations of special meridians seem to be explainable by their characteristic features defined in TCM.

Journal Article↗
PubMedDate not supplied

Comparison of keratometric and topographic cylinder and axis measurements on normal corneas with low astigmatism.

PURPOSE: To evaluate agreement in measurements of astigmatic axis power and location between keratometry and computer assisted videokeratography (corneal topography) on normal corneas with less than 1.50 D of idiopathic astigmatism. METHODS: Keratometric readings with the 10 SL/O Zeiss ophthalmometer and corneal topographic maps with the TMS-1 were obtained by two independent examiners on 32 normal corneas. Measurement agreement between the two instruments was evaluated in regard to steep and flat meridian power and location, and in astigmatism magnitude (D). RESULTS: The limits of agreement (d-2 SD to d+2 SD) between the two instruments were found to be broad for clinical purposes in measuring the steep meridian power (-0.16 to -1.20 D), flat meridian power (0.43 to -1.25 D), and astigmatism (0.60 to -1.12 D). A constant bias of the TMS-1 towards the 10 SL/O Zeiss ophthalmometer was found, in measuring steeper both principal meridians and higher amount of astigmatism. Mean location difference was 19 degrees (+/-190) for the steep meridian and 17 degrees (+/-20 degrees) for the flat meridian. CONCLUSIONS: Despite the differences seen in measurements between the 10 SL/O ophthalmometer and the TMS-1, these differences may be clinically small enough for the methods to be used interchangeably in measuring only the magnitude of astigmatism on normal corneas. However, the disagreement in astigmatism axes is too great to be ignored.

Adolescent↗
PubMed1992

Three-dimensional changes in direction and interrelationships among enamel prisms in the dog tooth.

This study describes the three-dimensional features of enamel prisms and their arrangement in dog teeth. Tangential semithin sections of demineralized tooth germ were serially cut from the enamel surface to the enamel-dentin junction. Straight rows of enamel prisms parallel or perpendicular to the meridian were selected at the enamel-dentin junction; these prisms were reconstructed from micrographs with a personal computer. Near the enamel-dentin junction, the arrangement of enamel prisms appeared regular. Viewed from the enamel surface, the cut-ends of the enamel prisms that were parallel to the meridian at the enamel-dentin junction appeared as a sine curve, with 16 enamel prisms forming one period. The enamel prisms in a row perpendicular to the meridian were parallel to each other and deflected to the left or right from the enamel-dentin junction. Away from the enamel-dentin junction, the periodicity of the prisms gradually disappeared. The sine curve formed by the cut-ends of prisms in a row parallel to the meridian became irregular, and prisms in rows perpendicular to the meridian crossed each other. The semithin sections showed belt-like zones arranged perpendicular to the meridian. Each belt-like zone consisted of enamel prisms oriented in the same direction, those in neighboring zones being oriented in opposite directions. The disappearance of the regular arrangement of prisms was related to changes in their location in the belt-like zones.

Animals↗
PubMedDate not supplied

Comparison of keratometry and videokeratography after penetrating keratoplasty.

BACKGROUND: As new methods for corneal curvature measurement have evolved, users of videokeratscopes need to know the practical limitations of these instruments. We assessed agreement between keratometry and videokeratography in measuring highly astigmatic corneas. METHODS: Two independent examiners made three keratometric and videokeratographic measurements on each of 33 corneas after penetrating keratoplasty. The non-orthogonal keratometric readings obtained with a Zeiss 10 SL/O keratometer (Carl Zeiss Ltd.) were compared to the non-orthogonal simK readings (maxK, minK) calculated by the algorithms of a TMS-1 videokeratoscope (Tomey). Measurement agreement was evaluated for steep and flat meridian power and location, and astigmatism magnitude (D). RESULTS: A systematic bias of the TMS-1 in measuring steeper than keratometry for the steep meridian was demonstrated (95% confidence interval: -0.34 to -1.20 D). The limits of agreement (d - 2SD to d + 2SD) between the two instruments were found to be unacceptable for clinical purposes in measuring steep meridian power (-3.17 to +1.63 D), flat meridian power (-4.92 to +4.48 D) and astigmatism magnitude (-5.84 to +4.87 D). Clinically acceptable differences were observed in identification of steep and flat meridian location. CONCLUSIONS: The Zeiss 10 SL/O keratometer and the TMS-1 videokeratoscope showed poor measurement agreement for irregular corneal surfaces, despite the good correlation previously shown between keratometry and videokeratography in calibrated spheres and regular corneas. The TMS-1 showed a systematic bias, measuring a greater power in the steeper meridian than the Zeiss 10 SL/O keratometer. It is suggested that the two instruments cannot be used interchangeably in comparing the curvature of corneas after penetrating keratoplasty.

Adult↗
PubMedDate not supplied

Measuring corneal thickness with a rotary scanning system.

PURPOSE: Recently the authors presented a technique that allows measurement of the corneal thickness along a vertical meridian from optical sections obtained using a slit-lamp microscope. We present a new system that allows rotary scanning of the cornea and consequent measurement of the corneal thickness along any meridian. METHOD: The corneal thickness along two perpendicular meridians was measured from optical sections obtained with a new rotary scanning system. To obtain the optical sections, the cornea is illuminated with a light beam that is previously expanded in a fan by a small cylindrical lens rotated on a plane-containing axis to explore the cornea. The light diffused by both corneal surfaces is collected by two video cameras placed at an angle with the light beam. The axes of the two cameras define, with the visual axis, two planes normal to each other. After image acquisition, a processing algorithm is applied in order to compute the corneal thickness along the two meridians. RESULTS: Some preliminary results for the vertical and the horizontal meridians of one eye are shown, as well as all the intermediate computations. CONCLUSIONS: With this system, we expect to be able to measure corneal topography and thickness along an arbitrary meridian. The rotary scanning of the cornea is mechanically simple and will eventually allow automated scanning.

Cornea↗
PubMed2003

The retinotopic organization of primate dorsal V4 and surrounding areas: A functional magnetic resonance imaging study in awake monkeys.

Using functional magnetic resonance imaging (fMRI), we mapped the retinotopic organization throughout the visual cortex of fixating monkeys. The retinotopy observed in areas V1, V2, and V3 was completely consistent with the classical view. V1 and V3 were bordered rostrally by a vertical meridian representation, and V2 was bordered by a horizontal meridian. More anterior in occipital cortex, both areas V3A and MT-V5 had lower and upper visual field representations split by a horizontal meridian. The rostral border of dorsal V4 was characterized by the gradual transition of a representation of the vertical meridian (dorsally) to a representation of the horizontal meridian (more ventrally). Central and ventral V4, on the other hand, were rostrally bordered by a representation of the horizontal meridian. The eccentricity lines ran perpendicular to the ventral V3-V4 border but were parallel to the dorsal V3-V4 border. These results indicate different retinotopic organizations within dorsal and ventral V4, suggesting that the latter regions may not be merely the lower and upper visual field representations of a single area. Moreover, because the present fMRI data are in agreement with previously published electrophysiological results, reported distinctions in the retinotopic organization of human and monkey dorsal V4 reflect genuine species differences that cannot be attributed to technical confounds. Finally, aside from dorsal V4, the retinotopic organization of macaque early visual cortex (V1, V2, V3, V3A, and ventral V4) is remarkably similar to that observed in human fMRI studies. This finding indicates that early visual cortex is mostly conserved throughout hominid evolution.

Anesthesia↗
PubMed1992

[Computerized videokeratoscopy. Indications for postoperative suture removal].

Twenty-three patients who had a high degree of postoperative astigmatism (3 D) after extracapsular cataract extraction were examined in a prospective study with a computerized videokeratoscope. Sutures were removed within the first 3 months postoperatively, and an examination with the videokeratoscope was performed at the same time. In addition, corneal power was measured with a keratometer for comparison. A comparative map demonstrating the change in corneal shape can be obtained by simple subtraction of the pre- and postoperative keratographs (color-coded topographical maps). Immediately after suture removal the corneal curvature was flattened in the steepest meridian (3 mm and 5 mm zone), resulting in an average net change in cylindrical refraction of -1.3 (+/- 1.7)D. The steepest meridian moved slightly in a counterclockwise direction (-5.79 +/- 29.4 degrees). The topographical analysis of all cases showed that suture removal along the steepest meridian reduced astigmatism by flattening the steepest meridian and steepening the flattest meridian. As the peripheral cornea becomes steeper, the central cornea flattens in a meridian. Morphologically, three different patterns were found. In 52% the reduction in astigmatism was "symmetric", in 21% it was "round", and in 26% it was "irregular". As a result of the study, a topographical model of the cornea will be given, showing the average net change in diopters power at various locations on the surface of the cornea. These results cannot be described by the use of ordinary keratometers.

Astigmatism↗
PubMedDate not supplied

Cat keratoplasty wound healing and corneal astigmatism.

BACKGROUND: A major contributor to postkeratoplasty astigmatism may be donor/recipient disparity. Deficient or excess cornea at the wound is thought to influence the directions of the steep and flat meridians. Using an established model of penetrating keratoplasty in the cat, this study evaluated the morphometry of histopathologic wound features in the steep and flat meridians. METHODS: Thirteen cats had successful penetrating keratoplasties after intentionally misshapen donor corneas were misaligned in misshapen recipient beds. At 9.50 +/- 0.32 (mean +/- 1 SEM) months after keratoplasty, photokeratography was performed and analyzed, corneas were sectioned along the steep and flat meridians, and four histologic sections were processed. Features of the wounds were measured using a Zeiss Videoplan. The relationships between the morphometry of each feature and every other feature, between the morphometry of each feature and eccentricity, and between the steep and flat section morphometry of each feature were statistically evaluated. RESULTS: Epithelial thickness, area of lamellar alteration, length of Descemet's membrane produced postoperatively, and the depth that preoperative Descemet's membrane was embedded in the stroma were correlated with eccentricity (corneal astigmatism). Stromal thickness and the presence or absence of folded and fragmented Descemet's membrane were not correlated with eccentricity. Wound morphometry at the steep meridians was neither correlated with nor significantly different from wound morphometry at the flat meridians. CONCLUSIONS: Differences between healing at the steep and flat meridians were not likely contributors to astigmatism. Disproportionate availability of tissue in wound regions may have affected healing throughout the entire wound over time. The absence of Bowman's layer in cats restricts application of our results to understanding the etiology of corneal astigmatism after penetrating keratoplasty in humans.

Animals↗
PubMedDate not supplied

Surgical correction of postoperative astigmatism.

The photokeratoscope has increased the understanding of the aspheric nature of the cornea as well as a better understanding of normal corneal topography. This has significantly affected the development of newer and more predictable models of surgical astigmatic correction. Relaxing incisions effectively flatten the steeper meridian an equivalent amount as they steepen the flatter meridian. The net change in spherical equivalent is, therefore, negligible. Poor predictability is the major limitation of relaxing incisions. Wedge resection can correct large degrees of postkeratoplasty astigmatism, Resection of 0.10 mm of tissue results in approximately 2 diopters of astigmatic correction. Prolonged postoperative rehabilitation and induced irregular astigmatism are limitations of the procedure. Transverse incisions flatten the steeper meridian an equivalent amount as they steepen the flatter meridian. Semiradial incisions result in two times the amount of flattening in the meridian of the incision compared to the meridian 90 degrees away. Combination of transverse incisions with semiradial incisions describes the trapezoidal astigmatic keratotomy. This procedure may correct from 5.5 to 11.0 diopters dependent upon the age of the patient. The use of the surgical keratometer is helpful in assessing a proper endpoint during surgical correction of astigmatism.

Astigmatism↗
PubMed1989

[The significance of static quantitative threshold perimetry and the barring of blind spot in kinetic quantitative perimetry in chronic open angle glaucoma].

The staircase threshold perimetry was measured for the 180 degrees-0 degree, 15 degrees, 165 degrees, 195 degrees and 345 degrees meridians of normal subjects and COAG patients. The kinetic quantitative perimetry was also tested in normal subjects with the I1e, I 2 e, I 3 e and I 4 e targets. The results were as follows: (1) The threshold for the 180 degrees-0 degree meridian at 20 degrees in the nasal side was lower than at 20 degrees in the temporal side in normal subjects (P less than 0.001); (2) the physiological blind spot in static threshold perimetry was 5.4 degrees +/- 0.942 degree in normal subjects and 8.09 degrees +/- 1.126 degree in COAG respectively on the horizontal meridian (P less than 0.001); (3) the nasal visual field defects in static threshold perimetry of COAG progressed from the periphery inward; (4) the upper nasal 15 degrees and 165 degrees meridian were more vulnerable than the lower nasal 195 degrees and 345 degrees meridians in COAG patients; (5) the thresholds of 15 degrees, 165 degrees, 195 degrees and 345 degrees meridians in COAG were much higher than those in normal subjects (P less than 0.001); and (6) in kinetic quantitative perimetry, the pseudobaring of physiological blind spot could be detected using the I1e target, with higher frequency in normal subjects over 40 years of age than under 40 years of age (P less than 0.005). The causes of differences in the visual field threshold, the nasal visual field defects, and pseudobaring of physiological blind spot were discussed, with evaluation of their diagnostic significance for COAG.

Adult↗
PubMed1988

Surgical correction of postoperative astigmatism.

The photokeratoscope has increased the understanding of the aspheric nature of the cornea as well as a better understanding of normal corneal topography. This has significantly affected the development of newer and more predictable models of surgical astigmatic correction. Relaxing incisions effectively flatten the steeper meridian an equivalent amount as they steepen the flatter meridian. The net change in spherical equivalent is therefore negligible. Poor predictability is the major limitation of relaxing incisions. Wedge resection can correct large degrees of postkeratoplasty astigmatism. Resection of 0.10 mm of tissue results in approximately 2 diopters of astigmatic correction. Prolonged postoperative rehabilitation and induced irregular astigmatism are limitations of the procedure. Transverse incisions flatten the steeper meridian an equivalent amount as they steepen the flatter meridian. Semiradial incisions result in two times the amount of flattening in the meridian of the incision compared to the meridian 90 degrees away. Combination of transverse incisions with semiradial incisions describes the trapezoidal astigmatic keratotomy. This procedure may correct from 5.5 to 11.0 diopters depending upon the age of the patient. The use of the surgical keratometer is helpful in assessing a proper endpoint during surgical correction of astigmatism.

Adrenal Cortex Hormones↗
PubMed2005

[Advances of studies on the biophysical characteristics of channels and acupoints].

OBJECTIVE: To summarize recent studies on the biophysical characteristics of meridians and acupoints, so as to provide a basis and thinking for scientific studies. METHODS: Twenty-nine papers about biophysical characteristics of meridians and acupoints were reviewed from studies of electricity, heat, sound, light, magnetic and radionuclide. RESULTS: The biophysical characteristics of meridians and acupoints have been proved in different domains, and meridians and acupoints objectively exist. CONCLUSION: Scientific studies on the biophysical characteristics of meridians and acupoints have vast vistas.

Acupuncture Points↗