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February, 1989
AMERICAN JOURNAL OF OPHTHALMOLOGY
148
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disc area (mm 2 }
disc diameter (mm)
Fig. 3 (Maisel and associates). Cup diameter plotted against disk diameter showing that large disks
tend to have large cups.
disks. These two patients had differences in
their cup/disk ratios equal to 0.2, with no other
stigmata of glaucoma. Disk asymmetry, that is,
disks whose cup/disk ratios differ by more than
0.2, was found by Armaly to represent only
0.5% of the normal population.’
Vertical disk cupping wherethevertical cup
diameter exceeds that of the horizontal was
found in 17 of 54 eyes. In each case, the vertical
measurement did not exceed that of the horizontal by more than 0.01 mm, a difference
which would probably go unnoticed when observed through an ophthalmoscope.
The average + 5.D. intraocular pressure was
calculated after grouping the eyes into four
categories. Eyes with large disks and large cups
had an intraocular pressure of 11.8 + 1.8 mm
Hg; those with small disks and smail cups, 11.4
+ 1.6 mm Hg; those with small disks and large
cups, 11.5 + 2.3 mm Hg; and those with large
disks and small cups, 12.5 + 2.5 mm Hg. There
was no significant difference between the
groups.
Visual acutty—Of the 36 patients, 31 (86%)
Fig. 4 (Maisel and associates). Rim area plotted
against disk area showing that large disks tend to
have greater rim area.
and 23 (64%) saw 20/20 or better. Of the five
patients with visual acuities less than 20/30,
three had reduced vision attributed to cataract.
As a result of congenital nystagmus plus bilateral pigment mottling in the macula from previous toxoplasmosis, the fourth patient had a
visual acuity of 20/50. Thefifth patient had an
uncorrected visual acuity of 20/200, which improved with pinhole to 20/40, in both eyes.
However, no visual acuity was recorded on the
chart following refraction with a —2.50 sphere.
Long-term follow-up—Optic disk photographs
taken in 1967, 18 years before this study, were
available for three patients (Table 2). There was
essentially no change in either disk or cup
diameters over the 18-year period.
Discussion
In this genetically isolated population in the
Marshall Islands, 15 patients were found to
had visual acuities better than or equal to 20/30
TABLE2
COMPARISON OF OPTIC DISKS AFTER 18 YEARS OF
FOLLOW-UP
TABLE 1
RADIATION EXPOSURE AND OPTIC DISK SIZE
1967
DISK
DIAMETER
(mm)
CUP/DISK
RATIO
DISK
DIAMETER
(MM)
—CUP/DISK
RATIO
1
22
0.90
2.1
0.75
2
2.2
0.70
2.2
0.70
17
0.70
1.8
0.70
EXPOSED
(N=12)
NONEXPOSED
(N=5)
Bilateral >2.1
6
2
Bilateral <2.1
5
2
Unilateral >2.1
1
1
3
DISK SIZE (mm)
SUL Zaz
1985
PATIENT NO.