Parapapillary Retinal Vessel Diameter in Normal and Glaucoma Eyes

Transcription

1 Investigative Ophthalmology & Visual Science, Vol. 30, No. 7, July 1989 Copyright Association for Research in Vision and Ophthalmology Parapapillary Retinal Vessel Diameter in Normal and Glaucoma Eyes //. Correlatio Josr B. Jonas and Gottfried O. H. Naumann The juxtapapillary diameters of the superior temporal and inferior temporal retinal artery and vein have been shown to be significantly smaller in glaucomatous eyes than in normal eyes. They had been measured in 473 eyes of 281 patients with chronic primary open-angle glaucoma and in 275 eyes of 173 normal subjects. In the current study the vessel diameters were correlated with intra- and parapapillary morphometric data and visual field indices. Only one eye per patient and subject was taken for statistical analysis. The retinal vessel calibers were significantly (P < 0.001) correlated with: (1) the area of the neuroretinal rim as a whole and in four different optic disc sectors; (2) the rim width determined every 30 ; (3) the optic cup area and diameters; (4) the horizontal and vertical cup/disc ratios and (5) the quotient of them; (6) the retinal nerve fiber layer score; (7) the area of the parapapillary chorioretinal atrophy; and (8) the visual field indices. In the same eye the vessel caliber was smaller in that sector where the neuroretinal rim loss was highest and the retinal fiber layer score lowest. In intraindividual comparison the vessels were smaller in that eye with less neuroretinal rim tissue and lower nerve fiber layer score. No significant correlatio were found with the form of the optic disc, the area of the peripapillary scleral ring, side, sex and refraction. The correlation coefficients were not significantly different when the control group was matched for age. The parapapillary retinal vessel diameter decreases with advancing glaucomatous optic nerve damage. It is correlated with morphometric intra- and parapapillary glaucomatous changes and perimetric defects. Invest Ophthalmol Vis Sci 30: ,1989 In normal eyes the juxtapapillary retinal vessel diameter has recently been shown to be larger in the inferior temporal arcade compared to the superior temporal arcade. 1 This corresponded with the width of the neuroretinal rim, which is broader at the inferior optic disc pole than at the superior disc pole, 2 ' 3 with the visibility of the retinal nerve fiber bundles, which are better detectable in the inferior temporal retinal area than in the superior temporal region, 4 and with the location of the foveola 0.53 ± 0.34 mm inferior to the optic disc center. 4 In eyes with chronic primary open-angle glaucoma the vessel diameter was significantly smaller than in the normal eyes. It has been suggested that vessel diameter reflects the need for vascular supply in the corresponding super- From the Department of Ophthalmology and Eye Hospital, University Erlangen-Nurnberg, West Germany. Supported by Dr. Helmut und Margarete Meyer-Schwarting- Stiftung, Bremen, Ert-Muck-Foundation, Erlangen, and by Deutsche Forschungsgemeichaft, DFG grant Nr. Jo 155/2-1. Submitted for publication: July 13, 1988; accepted January 9, Reprint requests: Dr. J. B. Jonas, Universitats-Augenklinik, Schwabachanlage 6, D-8520 Erlangen, West Germany. ficial retinal area and that it may be related to ganglion cell deity and retinal nerve fiber layer thickness. In the current study the data of the vessel diameters were correlated with intra- and parapapillary morphometric parameters and visual field indices. Materials and Methods Materials Photographs of 473 eyes of 281 patients suffering from chronic primary open-angle glaucoma and 275 eyes of 173 normal subjects were morphometrically analyzed. Coent was obtained from all patients and subjects. Mean age of the glaucoma patients (137 men, 144 women) was 63.0 ± 13.2 years (mean and standard deviation) (minimum: 20 years; maximum: 91 years), and the mean age in the control group (66 men, 107 women) was 44.5 ± 19.0 years (3-79 years). The refraction was in the glaucoma group on an average ± 2.61 diopters ( 7.35 diopters to diopters), and in the normal group ± 2.14 diopters (-7.88 to diopters). To compare the glaucomatous eyes with the normal eyes the latter were additionally matched for age. This age- 1604

2 No. 7 PARAPAPILLARY RETINAL VESSEL DIAMETER II / Jonas and Naumonn 1605 matched control group coisted of 131 eyes of 32 men and 51 women with a mean age of 62.5 ± 12.1 years and a mean refractive error of ± 2.03 diopters. Highly myopic eyes with a myopic refraction of more than diopters had generally been excluded because they have different morphometric optic disc characteristics. 5 Computerized perimetry (Octopus program or program Gl) had been performed for 310 eyes of 172 glaucoma patients. The criteria for the diagnosis of chronic primary open-angle glaucoma and the glaucoma staging have been described previously. 16 If both eyes had been photographed and morphometrically analyzed, only one randomly chosen eye per patient and subject was taken for interindividual compariso. For intraindividual studies the bilaterally evaluated eyes were taken. Method All optic nerve head photographs (15 color stereo diapositives) had been taken with a telecentric Zeiss fundus camera. They were magnified 15 and projected. The outlines of the optic disc and cup, the peripapillary scleral ring of Elschnig, the parapapillary chorioretinal atrophy zones Alpha and Beta, and the inferior temporal and superior temporal retinal artery and vein at the disc border and 2 mm from the optic disc center were plotted on paper and morphometrically analyzed (Zeiss Morphomat 30). The photographic magnification was corrected according to Littmann. 7 " 10 For the optic disc and optic cup we determined the area, the horizontal, vertical, minimal and maximal diameter, the ratio of minimal to maximal diameter, the angle between the maximal diameter and the horizontal, and a form factor. The latter ranged from 1.0 for an ideal circle to 0.0 for a structure quite uimilar to a circle. The neuroretinal rim area resulted as the difference of disc area minus cup area, and as the sum of the rim areas in the four different disc sectors. The neuroretinal rim width was measured every 30. In the juxtapapillary region the peripapillary scleral ring of Elschnig and zone Alpha and zone Beta of juxtapapillary chorioretinal atrophy were measured. The intra- and parapapillary area was divided into four sectors (Fig. 1). The superior temporal and the inferior temporal sectors B and C were right-angled, and their middle lines were tilted 13 to the vertical optic disc axis. on the temporal side and sector D on the nasal side covered the remaining area (64 and 116 ). The reason for this sectioning was the location of neuroretinal notches that were situated at about 13 temporal to the vertical optic disc poles. 6 The juxtapapillary zones Alpha and Beta and the NASAL Fig. 1. Sectioning of the intra- and juxtapapillary region according to the most frequent location of glaucomatous neuroretinal rim notches at about 13 temporal to the upper and lower optic disc pole: Sectors B and C are right-angled, and their midle lines are titlted 13 (angle /3) temporal to the vertical disc axis. on the temporal side (64 ) and sector D on the nasa! side (116 ) cover the remaining area. (Reprinted with permission from Jonas JB, Gusek GC, and Naumann GOH: Die parapapillare Region in Normal- und Glaukomaugen. I. Planimetrische Werte von 312 Glaukom- und 125 Normalaugen. KJin Mbl Augenheilk 193:52, 1988 (ref. 11)). neuroretinal rim were measured separately in the sectors. The intra- and juxtapapillary optic disc structures were defined as previously described." 12 The optic disc was the area iide of the white peripapillary scleral ring of Elschnig. 13 ' 4 The optic cup was defined on the basis of contour and not of pallor. Vessels were coidered as part of the optic cup if there was no underlying neuroretinal rim tissue; otherwise they were coidered to be part of the rim. The peripapillary scleral ring of Elschnig was the often circular white band surrounding the optic nerve head. It was often better seen on the temporal disc side than on the nasal side. Juxtapapillary chorioretinal atrophy 1215 was divided into two zones: zone Alpha was characterized by an irregular hypo- and hyperpigmentation, and intimated thinning of the chorioretinal tissue layer. It was adjacent to the retina on its outer side and to zone Beta or the peripapillary scleral ring of Elschnig on its inner side. Characteristics of zone Beta were marked atrophy of the retinal pigment epithelium and of the choriocapillaris, small grayfieldson a whitish background, good visibility of the large choroidal vessels, thinning of the chorioretinal tissues, and round bounds to the adjacent zone Alpha on the peripheral side and to the peripapillary scleral ring on its central side. If both zones were

3 1606 INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE / July 1989 Vol. 30 o.ie-t- 0.16" diameter inferior temporal o.m xx xxxnii artery (mm) CBCK K ^ K OOOOOK nil HUM OK) «M 0.08-*OJJMer*«* M K V x x xxw xx» xx xx x 0.06-i- << K total neuroretinal rim area (mm2) Fig. 2. Scattergram of the correlation between the total neuroretinal rim area and the diameter of the inferior temporal artery (measured at the optic disc border) in 473 eyes of 281 patients suffering from chronic primary open-angle glaucoma and in 275 eyes of 173 normal subjects. Only one randomly assessed eye per patient and subject was taken for statistical analysis. Correlation coefficient: 0.55; slope of the regression line: 0.016; significance: P < present zone Beta was always closer to the optic disc than zone Alpha. The retinal nerve fiber layer had been photographed according to Airaksinen 16 in 137 eyes of 79 glaucoma patients, in 127 normal eyes of 72 subjects, and in 68 eyes of 37 subjects of the age-matched control group. The retina had been divided into four sectors similar to the optic disc sectioning (Fig. 1). Retinal nervefibersof the temporal horizontal retinal sector were all those that reached the optic disc in the diameter inferior temporal OH * x xx xnx x xx x xxcxc *xxxx xotxxx KWC x x x _ - xo K aim C x xxw xaoakotifewauoonrtci xxx xxx< xxx xxxa M 1 h H 1 1 h vertical cup / disc ratio x x x x I«xx x xxx**iookx W 4( <4> K Fig. 3. Scattergram of the correlation between the vertical cup/ disc ratio and the diameter of the inferior temporal artery (measured at the optic disc border) in 473 eyes of 281 patients suffering from chronic primary open-angle glaucoma and in 275 eyes of 173 normal subjects. Only one randomly assessed eye per patient and subject was taken for statistical analysis. Correlation coefficient: -0.52; slope of the regression line: ; significance: P < temporal horizontal optic disc sector. The superioi temporal retinal sector was the area with those nerve fibers that reached the optic nerve head in the superior temporal disc sector. A score was given for the visibility of the retinal nerve fibers in each separate retinal sector. This score ranged from 0 for "no nerve fibers detectable" to 4 for "best visibility of the nerve fibers as in normal eyes in the same sector." 4 Results The parapapillary retinal vessel diameters were significantly correlated with: the neuroretinal rim area as a whole (Fig. 2) and divided into four optic disc sectors the ratio of the rim area in the temporal horizontal, in the inferior temporal and in the nasal disc sector divided by the total rim area the neuroretinal rim width measured every 30 the optic cup size the horizontal and vertical cup/disc ratios (Fig. 3) the quotient of the horizontal to vertical cup/disc ratio (Table 1) area of zone Beta of parapapillary chorioretinal atrophy (Fig. 4) the area of the total parapapillary chorioretinal atrophy (zone Alpha plus zone Beta) the retinal nerve fiber layer score as a whole (Fig. 5) and evaluated separately in the four retinal regio, and the mean visual field loss per tested point (Table 2). The correlation coefficients were not significantly different if the control group was matched for age. Concerning the tested parameters, the correlation coefficients were highest for the neuroretinal rim data, followed by the cup/disc ratios, the retinal nerve fiber layer score, the perimetric loss, area of zone Beta, and area of the total parapapillary chorioretinal atrophy (Tables 1,2). Concerning the vessel diameter, the highest coefficients were calculated for the inferior temporal artery (measured at the optic disc border), followed by the superior temporal artery (measured at the disc border). If the neuroretinal rim notch was most marked in the inferior temporal disc sector the superior temporal artery was larger in 46% and the inferior temporal artery was larger in 42%. The superior temporal artery measured on an average ± mm, and the inferior temporal artery ± mm. If the rim notch was more distinct in the superior temporal disc sector the superior temporal artery was

4 No. 7 PARAPAPILLARY RETINAL VESSEL DIAMETER II / Jonos ond Noumonn 1607 Table 1. Correlatio of the retinal vessel diameter Neuroretinal rim Area (total) 0.44 t 0.31 t t 0.55 t 0.42 t 0.42 t 0.45 t 0.44 t t 0.28 t 0.21 t 0.16 t 0.17 t 0.17 t 0.29 t 0.14* 0.19 t 0.37 t t 0.15 t 0.13* 0.14* 0.15 t 0.34 t 0.27 t t 0.16 t 0.26 t 0.22 t t /total /total /total /total Width Temporal horizontal Superior disc pole Inferior disc pole Nasal horizontal Cup area Cup form Cup/disc ratios Horizontal Vertical Hor/vertical 0.45 t 0.44 t t t 0.37 t 0.39 t 0.39 t 0.40 t 0.46 t 0.51 t 0.53 t 0.53 t t t t 0.17 t 0.16 t t 0.24 t 0.28 t 0.24 t 0.19 t 0.22 t 0.22 t 0.21 t t t t t t t t t 0.12* 0.19 t Coefficients of correlatio between the intrapapillary retinal vessel diameter and intrapapillary morphometric intra- and parapapillary data. 1 = diameter of the superior temporal artery at the optic disc border; 2 = diameter of the inferior temporal artery at the optic disc border; 3 = diameter of the superior temporal artery 2 mm from the optic disc center; 4 = diameter of the inferior temporal artery 2 mm from the optic disc center; 5 = diameter of the superior temporal vein at the optic disc border; 6 = diameter of the inferior temporal vein at the optic disc border; 7 = diameter of the superior temporal vein 2 mm from the optic disc center; diameter of the inferior temporal artery 2 mm from the optic disc center. * = P < 0.01; t = P < 0.001; = not significant. larger in 29%, and the inferior temporal artery was wider in 42%. In this group the diameter of the superior temporal artery was ± mm, and the caliber of the inferior temporal artery ± mm. If the rim area in the superior temporal disc sector was larger than the rim area in the inferior temporal 0.12-i W diameter inferior temporal artery 0.08; aoukmoomc diameter inferior temporal total area zone "Beta" Fig. 4. Scattergram of the correlation between the total area of zone Beta of parapapillary chorioretinal atrophy (visible large choroidal vessels and sclera) and the diameter of the inferior temporal artery (measured at the optic disc border) in 473 eyes of 281 patients suffering from chronic primary open-angle glaucoma and in 275 eyes of 173 normal subjects. Only one randomly assessed eye per patient and subject was taken for statistical analysis. Correlation coefficient: -0.20; slope of the regression line: ; significance: P < retinal nerve fiber layer score Fig. 5. Scattergram of the correlation between the retinal nerve fiber layer score and the diameter of the inferior temporal artery (measured at the optic disc border) in 137 eyes of 79 patients suffering from chronic primary open-angle glaucoma and in 127 eyes of 72 normal subjects. Only one randomly assessed eye per patient and subject was taken for statistical analysis. Correlation coefficient: 0.41; slope of the regression line: ; significance: P<

5 1608 INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE / July 1989 Vol. 30 Table 2. Correlatio of the retinal vessel diameter Parapapillary chorioretinal atrophy zone Alpha Total Zone Beta Total Zones Alpha and Beta Total Retinal nerve fiber layer Total Visual field loss (mean loss per test point) t t -0.15* 0.29 t t -0.18* t 0.37 t 0.39 t 0.39 t 0.40 t t -0.16* Coefficients of correlatio between the parapapillary retinal vessel diameter and intrapapillary morphometric intra- and parapapillary data. 1 = diameter of the superior temporal artery at the optic disc border, 2 = diameter of the inferior temporal artery at the optic disc border; 3 = diameter of the superior temporal artery 2 mm from the optic disc center; 4 = diameter of the inferior temporal artery 2 mm from the optic disc center; 5 = diameter of -0.15* -0.16* * 0.25* 0.27 t 0.23* 0.24* 0.22* t t -0.17* 0.34 t 0.28 t -0.16* t 0.34 t 0.31 t 0.31 t t -0.15* -0.19* 0.31 t the superior temporal vein at the optic disc border; 6 = diameter of the inferior temporal vein at the optic disc border; 7 = diameter of the superior temporal vein 2 mm from the optic disc center; diameter of the inferior temporal artery 2 mm from the optic disc center. = P < 0.01; t = P < 0.001; = not significant. disc sector, the artery diameter was larger in 54% in the superior temporal sector and larger in 38% in the inferior temporal sector. Mean artery caliber was superior temporally ± mm and inferior temporally ± mm. If the rim area was larger in the inferior temporal disc sector than in the superior temporal disc sector, the artery was wider in 12% in the superior temporal sector and in 53% in the inferior temporal sector wider. Mean artery caliber was superior temporally ±0.019 mm and inferior temporally ± mm. If the retinal nerve fiber layer score was larger in the superior temporal retinal area than in the inferior temporal one, the artery was wider in 57% in the superior temporal sector and in 35% in the inferior temporal sector. Mean artery caliber was superior temporally ± mm and inferior temporally ± mm. If the retinal nerve fiber layer of the inferior temporal area was higher, the superior temporal artery was wider in 12% and the inferior temporal artery in 53%. Mean diameter of the superior temporal artery was ±0.019 mm and of the inferior artery ± mm. If the neuroretinal rim area was larger or if the retinal nerve fiber layer score was higher in the right eye than in the left eye, the vessels were significantly (P < 0.01) larger in the right eye than in the left eye. If the neuroretinal rim area was larger or if the retinal nerve fiber layer score was higher in the left eye, the vessels were significantly (P < 0.01) larger in the left eye. No correlatio were found with age, refraction, sex and side. Discussion The retinal vessel diameter decreased with increasing glaucoma stage. The reduction of the vessel diameter was correlated with morphologic and perimetric glaucomatous changes. The correlation coefficients were highest for the diameter of the inferior temporal artery (measured at the optic disc border), followed by the diameter of the superior temporal artery (measured at the disc border). This corresponds with: (1) the significantly higher frequency of glaucomatous neuroretinal rim notches in the inferior tern-

6 No. 7 PARAPAPILLARY RETINAL VESSEL DIAMETER II / Jonos ond Noumonn 1609 Fig. 6. (lop) Optic disc with unilateral glaucomatous optic nerve damage (glaucoma stage III IV) due to secondary open-angle glaucoma. Optic disc: area: 1.82 mm2, horizontal diameter: 1.38 mm, vertical diameter: 1.65 mm. Optic cup: area: 1.50 mm2, horizontal diameter 1.22 mm, vertical diameter: 1.52 mm. Cup/disc ratio horizontal: 0.88, vertical: 0.91, horizontal/vertical: Neuroretinal rim: area: 0.32 mm2, width at the upper disc pole: 0.10 mm, at the lower disc pole: 0.04 mm, nasal: 0.10 mm, temporal: 0.06 mm. Zone Alpha (arrowheads) of parapapillary chorioretinal atrophy: 1.71 mm2; zone Beta (arrows) of parapapillary chorioretinal atrophy: 0.54 mm2. Retinal vessel diameter (measured at the optic disc border): superior temporal artery: 0.07 mm, inferior temporal artery: 0.06 mm, superior temporal vein: 0.13 mm, inferior temporal vein: 0.12 mm. Note: No parapapillary retinal nerve fiber bundles detectable, in contrast to Figure 7. Fig. 7. (bottom) Normal optic nerve head (contralateral eye of Fig. 6). Optic disc: area: 1.69 mm2, horizontal diameter: 1.38 mm, vertical diameter mm. No optic cup. Cup/ disc ratio: Neuroretinal rim: area: 1.69 mm2. Zone Alpha (arrowheads) of parapapillary chorioretinal atrophy: 0.30 mm2, no zone Beta of parapapillary chorioretinal atrophy. Retinal vessel diameter (measured at the optic disc border): superior temporal artery: 0.12 mm, inferior temporal artery: 0.13 mm, superior temporal vein: 0.16 mm, inferior temporal vein: 0.19 mm. Note: parapapillary retinal nerve fiber bundles very distinct. poral disc sector than in the superior temporal sector6; (2) the higher correlatio of the inferior temporal neuroretinal rim area with glaucomatous perimetric defects than the superior temporal rim area17; and (3) the enlargement of parapapillary chorioretinal atrophy, which is more marked in the inferior temporal sector than in the superior temporal sector." It indicates a spatial correlation between the location of the more distinct glaucomatous damage and the diameter decrease of the locally corresponding retinal vessel. The vein diameters were generally less well correlated with the glaucomatous changes than the artery diameters. The inferior temporal vein decreased from ± mm in the normal eyes to ± mm in the glaucoma group.1 Presuming a tube-like form, this represents a decrease of the vessel cross-section area of 16.7% compared with 28.8% for

7 1610 INVESTIGATIVE OPHTHALMOLOGY 6 VISUAL SCIENCE / July 1989 Vol. 30 the cross-section reduction of the inferior temporal artery (diameter in normal eyes: ± mm; glaucomatous eyes: ± mm). The discrepancy between the decrease of artery and vein crosssection might be caused by a clinically asymptomatic engorgement of the venous blood flow in glaucoma. The impediment might be respoible for the higher frequency of central retinal vein occlusion in eyes with chronic primary open-angle glaucoma. 18 Concerning the tested parameters, the correlation coefficients were highest for the neuroretinal rim area (Fig. 2, Tables 1,2). When the rim area was measured in four different disc sectors separately (Fig. 1) or if its width was determined every 30 in a clockwise fashion, the coefficients were relatively higher if the vessel diameter was compared with the rim area and width of the corresponding disc sector (Table 1). This might also be taken as evidence for the spatial relatiohip between the glaucoma damage and the local vessel diameter. The correlation coefficients were second highest for the cup/disc ratios in spite of their dependence on the optic disc size. 219 The vertical cup/disc ratio (Fig. 3) was generally better correlated than the horizontal cup/disc ratio. This corresponds with the higher clinical value of the vertical ratio, and with its better correlation to intra- and parapapillary morphometric and perimetric data ' 20 The quotient of the horizontal to vertical cup/disc ratio also was significantly correlated with the vessel diameter. This parameter is larger than 1.0 in normal eyes because normally the horizontal cup/disc ratio is higher than the vertical one. 2 In the course of glaucomatous optic nerve damage the neuroretinal rim loss takes place predominantly at the vertical disc poles so that the vertical cup/disc ratio enlarges more than the horizontal one. The quotient of the horizontal to vertical cup/disc ratio then becomes less than l.o. 617 Similar to the neuroretinal rim size and the cup/ disc ratios, the retinal nerve fiber layer score (Fig. 5) was best correlated with the inferior temporal artery diameter followed by the superior temporal artery caliber and the vein width (Table 2). Again, the coefficients were relatively higher if the regional nerve fiber layer score was compared with the corresponding vessel diameter. Lowest correlation coefficients were calculated for zone Beta (Fig. 4) and for total parapapillary chorioretinal atrophy. The significance of this relatiohip, however, shows the importance of evaluating the parapapillary region in glaucoma." 15 If the glaucoma group was divided up into eyes with neuroretinal rim notches, rim area loss and decreased retinal nerve fiber layer score predominantly in the superior temporal or in the inferior temporal sector, respectively, the retinal arteries were significantly wider in that sector in which the rim area was larger, in which the rim notch was more distinct, and in which the retinal nervefiberlayer score was higher. This also indicates a spatial correlation between reduction of the vessel diameter and glaucomatous damage in the corresponding region. This is similar to the spatial relatiohip between the glaucomatous neuroretinal rim loss iide of the optic disc and the increase of parapapillary chorioretinal atrophy outside of the optic nerve head." 15 If both eyes of the same patient were compared, the vessels were significantly smaller in that globe in which the neuroretinal rim area was smaller and the retinal nerve fiber layer score was lower (Figs. 6, 7). The retinal vessel diameter has been evaluated already in recent studies 21 " 26 in which, however, mostly only relative size units were used. The reduction of the vessel caliber in glaucoma observed in this study and its correlation in time and location with the morphologic and perimetric data show the importance of measuring the retinal vessel diameter in absolute size units for glaucoma diagnosis and possibly also for follow-up. Key words: neuretinal rim, optic disc morphometry, parapapillary chorioretinal atrophy, retinal nerve fiber layer, retinal vessel diameter References 1. Jonas JB, Nguyen N, and Naumann GOH: Parapapillary retinal vessel diameter in normal and glaucomatous eyes. I: Morphometric data. Invest Ophthalmol Vis Sci 30:1599, Jonas JB, Gusek GC, and Naumann GOH: Optic disc, cup, and neuroretinal rim size, configuration and correlatio in normal eyes. Invest Ophthalmol Vis Sci 29:1151, Jonas JB, Gusek GC, and Naumann GOH: Sectorial features of the neuroretinal rim (NRR) in normal and glaucomatous eyes. Ophthalmology 94(Suppl): 130, Jonas JB, Nguyen N, and Naumann GOH: The retinal nerve fiber layer in normal eyes. Ophthalmology 96: in press, Jonas JB, Gusek GC, and Naumann GOH: Optic disc morphometry in high myopia: A clinical study of 51 eyes. Graefes Arch Clin Exp Ophthalmol 226:587, Jonas JB, Gusek GC, and Naumann GOH: Optic disc morphometry in chronic primary open-angle glaucoma: I. Morphometric intrapapillary characteristics. Graefes Arch Clin Exp Ophthalmol 226:522, Littmann H: Zur Bestimmung der wahren GroCe eines Objektes auf dem Hintergrund des lebenden Auges. Klin Mbl Augenheilkd 180:286, Littmann H: Zur Bestimmung der wahren GroCe eines Objektes auf dem Hintergrund des lebenden Auges. KJin Mbl Augenheilkd 192:66, Jaeger W: Ermittlung der wahren PapillengroBe an Patienten: Beitrag zur Diagnose der Mikropapille. Fortschr Ophthalmol 80:527, Jonas JB, Gusek GC, Guggenmoos-Holzmann I, and Naumann GOH: Size of the optic nerve scleral canal and compari-

8 No. 7 PARAPAPILLARY RETINAL VESSEL DIAMETER II / Jonas ond Noumonn 1611 son to intravital determination of optic disk dimeio. Graefes Arch Clin Exp Ophthalmol 226:213, Jonas JB, Gusek GC, and Naumann GOH: Die parapapillare Region in Normal- und Glaukomaugen: I. Planimetrische Werte von 312 Glaukom- und 125 Normalaugen. Klin Mbl Augenheilkd 193:52, Jonas JB, Airaksinen PJ, and Robert Y: Definitioentwurf der intra- und parapapillaren Parameter flir die Biomorphometrie des Nervus opticus. Klin Mbl Augenheilkd 192:621, Elschnig A: Das Colobom am Sehnerveneintritt und der Conus nach unten. Arch Augenheilkd 51:391, 1900., 14. Elschnig A: Der normale Sehnerveneintritt des mechlichen Auges. Denkschrift der kaiserlichen Akademie der Wissechafte, mathematisch-naturwissechaftliche Classe, Band L:219, Jonas JB, Gusek GC, and Naumann GOH: Die parapapillare Region in Normal- und Glaukomaugen: II. Korrelation der planimetrischen Befunde zu intrapapillaren, perimetrischen undallgemeinen Daten. Klin Mbl Augenheilkd 193:182, Airaksinen PJ and Nieminen H: Retinal nerve fiber layer photography in glaucoma. Ophthalmology 92:877, Jonas JB, Gusek GC, and Naumann GOH: Optic disc morphometry in chronic primary open-angle glaucoma: II. Correlatio of the intrapapillary morphometric data with visual field indices. Graefes Arch Clin Exp Ophthalmol 226:531, Vannas S and Tarkkanen A: Retinal vein occlusion and glaucoma: Tonographic study of the incidence of glaucoma and of its prognostic value. Br J Ophthalmol 44:583, Bengtsson B: The variation and covariation of cup and disc diameters. Acta Ophthalmol 54:804, Jonas JB, Gusek GC, and Naumann GOH: Qualitative morphologische Charakteristika von Normal- und Glaukomapapillen. Klin Mbl Augenheilkd 193:481, Hodge J V, Parr JC, and Spears GFS: Comparison of methods of measuring vessel width on retinal photographs and the effect of fluorescein injection on apparent retinal vessel calibers. Am J Ophthalmol 68:1060, Parr JC and Spears GFS: General caliber of the retinal arteries expressed as the equivalent width of the central retinal artery. Am J Ophthalmol 77:472, Parr JC and Spears GFS: Mathematic relatiohips between the width of a retinal artery and the width of its branches. Am J Ophthalmol 77:478, Majewska K, Czechowicz-Janicka K, Przadka L, Piotrowicz M, and Chrebalowski Z: Computer data processing in the examination of retinal vessels in essential hyperteion and artherosclerosis. Ophthalmologica 172:445, Bracher D, Dozzi M, and Lotmar W: Measurement of vessel width on fundus photographs. Graefes Arch Clin Exp Ophthalmol 211:35, Robert Y, Hendrickson P, Blass J, and Gerber H: Respiratory and circulatory influence on photopapillometry. Graefes Arch Clin Exp Ophthalmol 224:96, 1986.