Large discs with large cups: a diagnostic challenge in African patients
Date
2010-04-16T09:00:47Z
Authors
Soma, Darshana
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Abstract
Objectives
To determine in a cohort of 69 African patients with large optic discs and large optic
cups, that proportion of patients with physiologic cupping (normal eyes) misdiagnosed as
glaucomatous. To evaluate the possible relationship between optic disc size and central
corneal thickness.
Design and method
A case series of 69 patients with large discs (vertical disc height measuring 1.8mm) and
large cups (vertical cup to disc ratio 0.6) was evaluated to determine what proportion
had glaucoma and what proportion was normal. Patients categorized as normal were
further evaluated to determine what proportion were previously misdiagnosed and treated
for glaucoma. Patients with a suspected diagnosis of glaucoma, normal tension glaucoma
or primary open angle glaucoma were recruited from the glaucoma clinic at St John Eye
Hospital.
Outcome measures included corrected vertical disc height (VDH), vertical cup to disc
ratio (CDR), central corneal thickness (CCT), the relationship between VDH and vertical
cup height, the relationship between VDH and CCT, adjusted intraocular pressure
(A-IOP), retinal nerve fiber layer analysis and visual fields.
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Results
Sixty-nine African patients (138 eyes) with large discs and large cups were evaluated.
41 (59%) were females and 28 (41%) were males. The mean age was 56 years. Of the
69 patients, 51 (74%) had physiologic cupping (normal eyes) and 18 (26%) patients were
glaucomatous. Of the group of 51 patients with physiologic cupping, there were 9
patients who were previously misdiagnosed with glaucoma and who had received
treatment.
VDH ranged between 1.9 and 3.2mm (mean ±SD, 2.3±0.26mm). The distribution
analysis of VDH measurements noted the largest cluster around 2.3mm. CCT ranged
between 454μm and 618μm (mean±SD, 516±37μm). 107 (77.5%) of the 138 eyes had
CCT < 544μm.
Conclusion
Large cup to disc ratio in relation to large disc size can be normal. It can be
misdiagnosed as glaucomatous if objective retinal nerve fiber layer analysis is not carried
out. In this study, 9 (18%) patients from a group of 51 patients with physiologic cupping
were misdiagnosed as glaucomatous. There was no linear correlation between CCT and
VDH in this study. Pearson’s correlation coefficient was 0.13. The majority (77.5%) of
eyes had thin corneas (CCT < 544μm).
Description
MMed, Ophthalmology,Faculty of Health Sciences, University of the Witwatersrand, 2009
Keywords
optic discs, optic cups, optic disc size, glaucoma