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Size of Line in the Maddox-Rod Test*
SIZE O F L I N E IN T H E MADDOX-ROD T E S T * RICHARD G.
SCOBEE,
M.D.+
Saint Louis, Missouri AND E A R L L. G R E E N ,
PH.D.*
Columbus, Ohio
This study is one of several (Scobee and Green 1 ) concerned with the effect of vari ables in testing technique on the measure ment of heterophoria with the Maddox-rod test. The particular variable studied in this report was that of the size of the line of light as seen through the Maddox rod in measuring heterophoria at a testing distance of 13 inches. It is a well-known fact that different examiners using the same test of heterophoria on the same individual may get different results. In a search for possible explanations of this variation, several pos sible variables have already been studied. These include : examiner variation, test used and its correlation with the cover test, amount of illumination in the testing room, color of the Maddox rod used, the eye be fore which the Maddox rod is placed—that is, dominant or nondominant—in performing the test, and individual subject variation from day to day. METHODS FOR MEASURING TEST LIGHTS USED
It was believed that since different ex aminers may use different sized muscle lights at the 13-inch testing distance and produce varying sized lines as seen through the Maddox rod, any possible effect of this size difference should be determined. In the * This study was done under a contract with the Office of Naval Research as Project N6onr-202, Task Order I. t From the Department of Ophthalmology, Washington University School of Medicine, and the Oscar Johnson Institute. t From the Department of Zoology, Ohio State University, Columbus.
beginning, three test lights were used. One was an ophthalmoscope with a May-type head removed; a second was a flashlight fitted with a solid diaphragm in which a hole 1.0 mm. in diameter had been bored; a third was a Welch-Allen ophthalmoscope with the head removed. The May-type oph thalmoscope gave a broad line image when viewed through a white Maddox rod. The 1.0 mm. light gave a narrow, sharply de limited line. The Welch-Allen ophthalmo scope light had such a comparatively large filament and resulted in so many lines of varying brightness when viewed through the Maddox rod that it had to be discarded be cause it was too confusing to the subjects. TESTING DISTANCE
All measurements were made at a test ing distance of 13 inches with the testing technique previously described (Scobee and Green 1 ). In brief, both lateral and vertical heterophoria were measured at 13 inches with a white Maddox rod placed before the right eye of all .subjects. For lateral hetrophoria, a Risley rotary prism mounted on ä phorometer (American Optical Company) was placed before the same eye as the Mad dox rod ; the rotary prism had a total strength of 30 prism diopters and was calibrated in units of 1 prism diopter. For vertical het erophoria, the Maddox rod was used in conjunction with a Stevens phorometer mounted on the same instrument; the prisms were split before the two eyes and had a total strength of 2 prism diopters, being calibrated in 0.2 diopter units. Thirtytwo subjects were tested.
697
RICHARD G. SCOBEE AND EARL L. GREEN
698
R E S U L T S OF M E A S U R E M E N T S LATERAL HETEROPHORIA
The average heterophoria was —4.89 prism diopters (exophoria) when the source of the light was large (ophthalmoscope) and —4.87 prism diopters when the source of light was small (flashlight). The differ ence of 0.02 prism diopters is not statisti cally significant, the standard error of the difference being 0.398 prism'diopters (t = 0.05, df = 31, P > 0 . 9 0 ) . Two tests were made of the justifica tion for using the statistical method of com paring a mean difference with its standard error. The first of these was to see if the frequency distributions of heterophoria under the two conditions of large and small
sources are highly correlated, r = +0.90. This is sufficiently high to indicate that knowledge of a heterophoria reading made under one condition will be equivalent for most practical circumstances to a hetero phoria reading made under the other con dition. Of the 32 subjects examined, only one had as much as 6 diopters difference, a shift from —14 prism diopters with the large light to —8 prism diopters with the small light. Two subjects had shifts of 4 prism diopters, one from + 4 to + 8 , the other from —6 to —10. The remaining 29 subjects gave readings with differences of 3 prism diopters or less. VERTICAL HETEROPHORIA
The average heterophoria was
—0.03
TABLE 1 AVERAGE HETEROPHORIAS FOR 32 SUBJECTS FOR TWO SOURCES OF LIGHT*
Source of Light
Lateral Heterophoria (in prism diopters)
Vertical Hetercphcria (in prism diopters)
-4.89 -4.87
-0.03 +0.03
0.02
0.06
±0.39 ±0.90
±0.12 ±0.85
Ophthalmoscope (large) Flashlight (small) Difference Standard error of difference Coefficient of correlation * Note: — = exophoria; +=esophoria. — =left hyperphoria; 4- = right hyperphoria.
sources of light were approximately normal in form. The distributions were shown to be sufficiently symmetrical and bell-shaped to justify the assumption of normality. The second test was to see if the variances of the two distributions were the same within sampling limits. These variances were found to be 25.67 square prism diopters for the large light source and 25.72 square prism diopters for the small light source. The ratio of these two variances, F = 1.002, indicates they are not significantly different as judged by the method of Morgan 2 for comparing variances of correlated series. The heterophoria determinations under the two conditions of large and small light
prism diopters with a large light source and +0.03 prism diopters with a small light source. The difference of 0.06 prism diop ters is not significant when compared with its standard error of 0.12 prism diopters, (t = 0.48, df = 31, P = 0.70 - 0.60). The correlation coefficient was +0.85 and this is high enough to permit substitution of the large light for the small light reading or vice versa. The same two tests for the justification of using the above test of significance were made. The distributions were approximately normal in form and the variances, 0.664 and 0.660, were homogeneous.
699
REGENERATION OF CORNEAL STROMAL CELLS CONCLUSIONS
There is no significant difference in the measurement of lateral and vertical heterophoria with the white Maddox rod at a test ing distance of 13 inches when the size of the line as seen through the Maddox rod is either large or small. This means that any variation in heterophoria measurements in the same individual by different examiners
using the Maddox-rod test at 13 inches can not be considered due to any variation in the size of the line produced by varying sized muscle lights. Such a conclusion seems justified as long as the size of the muscle light used is within the limits of those in cluded in this study. 640 South Kingshighway (10). Ohio State University.
REFERENCES
1. Scobee and Green : Am. J. Ophth., 30:436,1947.
2. Morgan : Biometrika, 31:13, 1939.
R E G E N E R A T I O N O F T H E CORNEAL STROMAL CELLS* I. TECHNIQUE FOR DESTRUCTION
OF CORNEAL CORPUSCLES BY APPLICATION
SOLIDIFIED (FROZEN) CARBON DIOXIDE ALFRED E. MAUMENEE, M.D.,
AND WALTER KORNBLUETH,*
Baltimore, Maryland
Regeneration of the cornea has been ex tensively studied in the past. The origin and mode of replacement of the epithelium, endothelium, and Descemet's membrane is clearly understood.1'2 There is still, however, a difference of opinion about the origin of the corneal stromal cells. A detailed review of the literature on this subject will be pub lished at a later date. The purpose of this paper is to report the technique of a method for studying the regeneration of stromal cells which appears to be superior to the methods previously used by other investiga tors in this field. PREVIOUS EXPERIMENTAL METHODS
The essence of the previous methods is as follows. Salzer3 made incisions into the * From the Wilmer Ophthalmological Institute of The Johns Hopkins Hospital and University. t Fellow of the Eye-Bank for Sight Restoration, Inc., New York.
Fig. 1 (Maumenee and Kornblueth). Solid brass applicators.
M.D.
OF
SCOBEE,
M.D.+
Saint Louis, Missouri AND E A R L L. G R E E N ,
PH.D.*
Columbus, Ohio
This study is one of several (Scobee and Green 1 ) concerned with the effect of vari ables in testing technique on the measure ment of heterophoria with the Maddox-rod test. The particular variable studied in this report was that of the size of the line of light as seen through the Maddox rod in measuring heterophoria at a testing distance of 13 inches. It is a well-known fact that different examiners using the same test of heterophoria on the same individual may get different results. In a search for possible explanations of this variation, several pos sible variables have already been studied. These include : examiner variation, test used and its correlation with the cover test, amount of illumination in the testing room, color of the Maddox rod used, the eye be fore which the Maddox rod is placed—that is, dominant or nondominant—in performing the test, and individual subject variation from day to day. METHODS FOR MEASURING TEST LIGHTS USED
It was believed that since different ex aminers may use different sized muscle lights at the 13-inch testing distance and produce varying sized lines as seen through the Maddox rod, any possible effect of this size difference should be determined. In the * This study was done under a contract with the Office of Naval Research as Project N6onr-202, Task Order I. t From the Department of Ophthalmology, Washington University School of Medicine, and the Oscar Johnson Institute. t From the Department of Zoology, Ohio State University, Columbus.
beginning, three test lights were used. One was an ophthalmoscope with a May-type head removed; a second was a flashlight fitted with a solid diaphragm in which a hole 1.0 mm. in diameter had been bored; a third was a Welch-Allen ophthalmoscope with the head removed. The May-type oph thalmoscope gave a broad line image when viewed through a white Maddox rod. The 1.0 mm. light gave a narrow, sharply de limited line. The Welch-Allen ophthalmo scope light had such a comparatively large filament and resulted in so many lines of varying brightness when viewed through the Maddox rod that it had to be discarded be cause it was too confusing to the subjects. TESTING DISTANCE
All measurements were made at a test ing distance of 13 inches with the testing technique previously described (Scobee and Green 1 ). In brief, both lateral and vertical heterophoria were measured at 13 inches with a white Maddox rod placed before the right eye of all .subjects. For lateral hetrophoria, a Risley rotary prism mounted on ä phorometer (American Optical Company) was placed before the same eye as the Mad dox rod ; the rotary prism had a total strength of 30 prism diopters and was calibrated in units of 1 prism diopter. For vertical het erophoria, the Maddox rod was used in conjunction with a Stevens phorometer mounted on the same instrument; the prisms were split before the two eyes and had a total strength of 2 prism diopters, being calibrated in 0.2 diopter units. Thirtytwo subjects were tested.
697
RICHARD G. SCOBEE AND EARL L. GREEN
698
R E S U L T S OF M E A S U R E M E N T S LATERAL HETEROPHORIA
The average heterophoria was —4.89 prism diopters (exophoria) when the source of the light was large (ophthalmoscope) and —4.87 prism diopters when the source of light was small (flashlight). The differ ence of 0.02 prism diopters is not statisti cally significant, the standard error of the difference being 0.398 prism'diopters (t = 0.05, df = 31, P > 0 . 9 0 ) . Two tests were made of the justifica tion for using the statistical method of com paring a mean difference with its standard error. The first of these was to see if the frequency distributions of heterophoria under the two conditions of large and small
sources are highly correlated, r = +0.90. This is sufficiently high to indicate that knowledge of a heterophoria reading made under one condition will be equivalent for most practical circumstances to a hetero phoria reading made under the other con dition. Of the 32 subjects examined, only one had as much as 6 diopters difference, a shift from —14 prism diopters with the large light to —8 prism diopters with the small light. Two subjects had shifts of 4 prism diopters, one from + 4 to + 8 , the other from —6 to —10. The remaining 29 subjects gave readings with differences of 3 prism diopters or less. VERTICAL HETEROPHORIA
The average heterophoria was
—0.03
TABLE 1 AVERAGE HETEROPHORIAS FOR 32 SUBJECTS FOR TWO SOURCES OF LIGHT*
Source of Light
Lateral Heterophoria (in prism diopters)
Vertical Hetercphcria (in prism diopters)
-4.89 -4.87
-0.03 +0.03
0.02
0.06
±0.39 ±0.90
±0.12 ±0.85
Ophthalmoscope (large) Flashlight (small) Difference Standard error of difference Coefficient of correlation * Note: — = exophoria; +=esophoria. — =left hyperphoria; 4- = right hyperphoria.
sources of light were approximately normal in form. The distributions were shown to be sufficiently symmetrical and bell-shaped to justify the assumption of normality. The second test was to see if the variances of the two distributions were the same within sampling limits. These variances were found to be 25.67 square prism diopters for the large light source and 25.72 square prism diopters for the small light source. The ratio of these two variances, F = 1.002, indicates they are not significantly different as judged by the method of Morgan 2 for comparing variances of correlated series. The heterophoria determinations under the two conditions of large and small light
prism diopters with a large light source and +0.03 prism diopters with a small light source. The difference of 0.06 prism diop ters is not significant when compared with its standard error of 0.12 prism diopters, (t = 0.48, df = 31, P = 0.70 - 0.60). The correlation coefficient was +0.85 and this is high enough to permit substitution of the large light for the small light reading or vice versa. The same two tests for the justification of using the above test of significance were made. The distributions were approximately normal in form and the variances, 0.664 and 0.660, were homogeneous.
699
REGENERATION OF CORNEAL STROMAL CELLS CONCLUSIONS
There is no significant difference in the measurement of lateral and vertical heterophoria with the white Maddox rod at a test ing distance of 13 inches when the size of the line as seen through the Maddox rod is either large or small. This means that any variation in heterophoria measurements in the same individual by different examiners
using the Maddox-rod test at 13 inches can not be considered due to any variation in the size of the line produced by varying sized muscle lights. Such a conclusion seems justified as long as the size of the muscle light used is within the limits of those in cluded in this study. 640 South Kingshighway (10). Ohio State University.
REFERENCES
1. Scobee and Green : Am. J. Ophth., 30:436,1947.
2. Morgan : Biometrika, 31:13, 1939.
R E G E N E R A T I O N O F T H E CORNEAL STROMAL CELLS* I. TECHNIQUE FOR DESTRUCTION
OF CORNEAL CORPUSCLES BY APPLICATION
SOLIDIFIED (FROZEN) CARBON DIOXIDE ALFRED E. MAUMENEE, M.D.,
AND WALTER KORNBLUETH,*
Baltimore, Maryland
Regeneration of the cornea has been ex tensively studied in the past. The origin and mode of replacement of the epithelium, endothelium, and Descemet's membrane is clearly understood.1'2 There is still, however, a difference of opinion about the origin of the corneal stromal cells. A detailed review of the literature on this subject will be pub lished at a later date. The purpose of this paper is to report the technique of a method for studying the regeneration of stromal cells which appears to be superior to the methods previously used by other investiga tors in this field. PREVIOUS EXPERIMENTAL METHODS
The essence of the previous methods is as follows. Salzer3 made incisions into the * From the Wilmer Ophthalmological Institute of The Johns Hopkins Hospital and University. t Fellow of the Eye-Bank for Sight Restoration, Inc., New York.
Fig. 1 (Maumenee and Kornblueth). Solid brass applicators.
M.D.
OF