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Show / ollmal ll( C/ i" ical N"""'- 0l'hthal"' l,/ oXI/ 11 ( 1): 66- 69, 1991. Relationship Between Visual Acuity and Nasal Field Thresholds in Patients with Temporal Hemianopia Riri S. Manor, M. D" and Zvi Dickerman, M. D. © 1991 Raven Press, Ltd., New York The area of nasal field found with Goldmann static perimetry and the sum of decibels by Humphrey threshold 30/ 2 was calculated in normal subjects and in subjects with chiasmatic lesions, temporal field loss, and normal or abnormal visual acuity. There was a significant reduction of the mean of the area of the nasal field by static Goldmann perimetry and of the mean of decibels in the nasal field on Humphrey perimetry in patients with temporal field loss and chiasmatic lesions, as compared with normal controls. There were significant correlations of nasal field depression ( Goldmann) and visual acuity and for sums of nasal field decibels ( Humphrey) and visual acuity. Thus, a generally depressed nasal field was found in patients with chiasmatic lesions and temporal field loss when accompanied by lowering of visual acuity. This would appear to be the earliest stage of nasal field involvement. Key Words: Visual acuity- Nasal field thresholdsTemporal hemianopia- Humphrey automatic perimetry- Goldmann static perimetry. From the Neuro- Ophthalmologic Unit, Department of Ophthalmology ( R. S. M.) and the Institute of Pediatric and Adolescent Endocrinology ( Z. D.), Beilinson Medical Center, Petah Ti. kva, and the Sackler School of Medicine, Tel Aviv University, Ramat Aviv, Israel. Address correspondence and reprint requests to Dr. R. S. Manor at Neuro- Ophthalmologic Unit, Department of Ophthalmology, Beilinson Medical Center, 49 100 Petah Tikva, Israel. 66 Cogan has stated that lesions of the retrochiasmal pathways that produce hemianopia will not impair the visual acuity unless there is bilateral disease ( 1). It appears logical that chiasmallesions producing only temporal field loss would not impair visual acuity as long as there is no involvement of the uncrossed afferent fiber tracts. The purpose of this study was to investigate the relationship between visual acuity and the nasal field thresholds in patients with chiasmatic lesions producing temporal field loss. MATERIALS AND METHODS OUf sample consisted of 13 patients with temporal field loss due to chiasmatic lesions and 7 normal subjects matched for age. The normal subjects, aged 21- 46 years ( m ± S. D. = 35.1 ± 10.1 years, median 35 years), had no detectable visual or ocular abnormalities and only the field of one eye was included in the study. The patients with chiasmatic lesions presented an age range from 20 to 69 years ( m ± S. D. = 52.6 ± 13.9 years, median = 55 years) and had no other ocular pathology or mental disability that could interfere with the results of the field examination. In 6 of the 13 patients 1 eye was blind; thus only 20 eyes were examined. Visual acuity was measured at 6 meters, with correction of refraction. Near addition was provided during the field examinations. Kinetic perimetry with the isopters V/ 4, 1/ 4, 1/ 3 and 1/ 2 was performed with the Goldmann 940 perimeter. Static perimetry was performed by two methods: ( a) Goldmann static perimetry- the 180- 0° meridian of the given field was studied on the Goldmann 940 perimeter at each 5 degrees of nasal ./---------"'. ( VISUAL ACUITY, NASAL FIELD THRESHOLDS, AND HEMIANOPIA 67 DISCUSSION TABLE 2. Goldmann static perimetry area under curve ( mean ± SD) of nasal field Nasal field sensitivity changes are usually not focused upon by the perimetrist in cases of temporal field loss with chiasmatic lesions. Yet in 1964 Hoyt ( 3) pointed out that total functional interruption of crossing projections rarely occurs before evidence of uncrossed fiber involvement is detected. The findings of our study indicate that, in patients with a chiasmatic lesion producing a temporal field loss and a lowering of visual acuity, the nasal field sensitivity at Humphrey perimetry and the area of nasal field at Goldmann static perimetry are significantly reduced as compared with those in normal subjects and in patients with temporal field loss but good visual acuity. The results obtained with Humphrey automatic perimetry thresholds measured in decibels of the central and peripheral area of the nasal field in the two groups are presented in Table 3, which shows significant differences in the mean readings of the controls versus the temporal field loss group in both the central and peripheral areas of the nasal field. It is of note that no significant difference was found in comparing the mean area under curve and the mean of Humphrey automatic perimetry thresholds readings between patients and controls in whom both methods were used, versus those in whom only one of the methods was used. Hence all the examined eyes were included in the correlation analysis ( Fig. 1). There were significant correlations obtained between the individual area under curve of the Goldmann static perimetry versus visual acuity and between the individual sums of Humphrey decibel readings versus visual acuity ( Figs. 2 and 3). p 8,424 ± 1,394 ( 17)" < 0.01 Controls Temporal field loss " Number of eyes. 13,358 ± 1920 ( 7)" The mean area under curve obtained in Goldmann static perimetry cuts of the nasal field in the normal controls and in the patients with temporal field loss is presented in Table 2, which demonstrates a significant reduction of the area under curve in the patients with temporal field loss. RESULTS Evaluation of the Goldmann perimetric static cut at the 180- 0° meridian was made by calculating the area under the curve using the trapezoidal method for each individual curve. The trapezoidal rule calculates the integral of a function on the basis of a successively closer approximation of the true area under the curve by subdividing it into a series of trapezoids ( 2). Evaluation of the Humphrey automatic perimetric decibels was done by calculating the sum, mean, and standard deviation of all decibels obtained in the points examined in the central ( 30/ 2) and peripheral ( 60/ 2) nasal field. Comparison between the means of the two groups was done using the nonpaired Student's t test with calculation of the two- tailed level of significance. A regression correlation analysis was made between the area under curve of each subject's nasal field and the sum of the decibels in the examined points of the central and peripheral areas of the nasal field obtained with Humphrey perimetry, versus the visual acuity in each individual. Statistical Methods field; ( b) Humphrey automatic perimetry thresholds- the 30/ 2 and 60/ 2 programs were used. Because of problems of compliance, we were not able to test all the eyes with both methods. The number of eyes examined by Humphrey and Goldmann's static perimetry in accordance with the diagnosis is presented in Table 1. TABLE 1. Number of eyes examined by Humphrey automated perimetry thresholds and/ or Goldmann static perimetry TABLE 3. Humphrey automated perimetric decibels ( m ± S. D.) of central and peripheral nasal field Total no. HAPT GSP HAPT + GSP of eyes Controls 0 4 3 7 Temporal Hemianopia 3 10 7 20 HAPT, Humphrey automated perimetric thresholds; GSP, Goldmann static perimetry. Temporal Nasal field loss field Controls patients Central ( 30.2)" 29.2 ± 2.6 ( 3) 23.8 ± 5.4 ( 10) Peripheral ( 60.2) 14.7 ± 10.6 ( 3) 7.2 ± 7.5 ( 10) " In parentheses: number of eyes. p < 0.05 < 0.01 / JClin Neuro- ophthalmol. Vol. II, No. 1, 1991 68 R. S. MANOR AND Z. DICKERMAN --./-- o eyl ey' 5ph :: N o V 1 6301 - _ i- looo 10 0 10' 50 40 30 20' 10 0 o , o cyl Sph :: cy! C sph :: - f':- -~ -- - r--.- '- r- i- I ~: jC-~ 1'~-,---, --- .- -.- -- j-.-- 40!-- r-- I I 631! l 0010;-- · - - t - .--+---- t--- j--- j------:;;, jt- - 16! i - iN 25[_..~--_~--+--+. . 40! 63i ! . -- 0100f- · · - · - l---- i 16Qj ! ' jptl :- 50 40 30 N C V C 0001 - B 1.8 25 4.0 6.3 0010~ o , 20' 10 0 o cyl ,: yl c ~. ph 000,1, A R ~ S: ,10' b. J I 0,1l0' Jri! N ....... II}; ' i, j" U100! 160; FIG. 1. Horizontal 0- 180° meridian cut of nasal field by Goldmann static perimetry- demonstration of changes in area under the curve ( AUC): Normal control with visual acuity = 1.2 ( A); patient with temporal field loss and visual acuity = 1.0 ( 8); patient with temporal field loss and visual acuity = 0.4 ( C). This early involvement of the nasal field is usually missed by perimetry, although Goldmann kinetic perimetry may demonstrate a relative inward displacement of the isopters in the nasal field. The same progression of field defect, i. e., depression followed only later by localized defect, was observed in the development of temporal field loss. Frisen ( 4) described the earliest field defect in midchiasmal compression as a bitemporal foreshortening of central isopters, usually more pronounced above, and often lacking a clear vertical step. At this stage of initial field involvement patients may be visually asymptomatic, and the field disturbance can be detected only by serial perimetry or by comparison of " normal" preoperative fields with the improved postoperative fields ( correcting the previous criteria for normalcy). Accord-ing to Frisen, these early defects were generally easier to detect in kinetic perimetry isopters than in static profiles. In a case of cyclic compression of the intracranial optic nerve, Frisen et al. ( 5) found that a drop in visual acuity preceded the measurable change in field and that the first field change was an increasingly severe uniform depression of field. This was interpreted to reflect a uniform distribution of conduction failure across the optic nerve. In all our patients with temporal hemianopia in whom the uncrossed axons were most probably still spared by the compressive/ ischemic processes, there was a normal visual acuity correlating Significantly with normal thresholds of the whole nasal hemifield. Anatomical variations of vessels, chiasmal po- •• ••• 13000 r - 0.85 peO. O! • • • • 0 5000 12 1000 9000 11000 Area under the curve ( AUC) FIG. 3. Regression of visual acuity on area under the curve of Goldmann's nasal field static perimetry of each subject. • r - 0.82 p<. 002 • • 1.2 • 700 800 900 1000 1100 1200 Sum of points per subject FIG. 2. Regression of visual acuity on sum of decibels of Humphrey's nasal field threshold 30/ 2 perimetry of each subject. ~ 0.8 ' u5 • « 0.6 ' i • .~ 0.4 • > 02 J1 No. i i'-~'): Y /--------'" VISUAL ACUITY, NASAL FIELD THRESHOLDS, AND HEMIANOPIA 69 sition ( pre- or post- fixed), degree of compression, and the speed of the tumoral growth all may play a role in the extent of vascular occlusion and the resultant axonal damage, with varying extent of field involvement and prognostic implications. REFERENCES 1. Cogan DC. Nellrology of the l, isllal system. Springfield: CC Thomas, 1966. / 2. Kelly L. Handbook of numerical methods and applications Reading, Massachusetts, Addison- Wesley, 1967; 54- 5. 3. Hoyt WF. The human optic chiasm. In: Smith JL, ed. Neuroophthalmology. Springfield: CC Thomas, 1964; 1-- 48. 4. Frisen L. The earliest visual field defects in mid- chiasmal compression. In: Heijl A, Greve EL, eds. Sixth Internatio1Ul1 Visual Field Symposium, Dordrecht, Boston, Lancaster: Dr. W Yung Pub}, 1985, 191- 5. 5. Frisen L, Sjostrand 1. Norrsell K, Lindgren, S. Cyclic compression of the intracranial optic nerve: patterns of visual failure and recovery. / Neurol Nellrosurg Psychiatry 1976; 39: 1109. J Clin Neuro- ophtlwlmol, Vol. 11, No.!, 1991 |
