Abstract:
BACKGROUND : The study was undertaken in order to determine
in patients with large optic discs and large optic cups, the
proportion with physiologic cupping (normal eyes) misdiagnosed
as glaucomatous; and further, to evaluate the possible relationship
between optic disc size and central corneal thickness.
METHOD AND DESIGN : A case series of 69 Black African patients
with large discs (vertical disc height measuring >1.8 mm) and
large cups (vertical cup to disc ratio ≥0.6) was evaluated to
determine what proportion had glaucoma. Patients categorised
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’s Eye Hospital,
Soweto, South Africa.
Outcome measures included corrected vertical disc height
(VDH), vertical cup to disc ratio (CDR), intraocular pressure (IOP),
central corneal thickness (CCT), retinal nerve fibre layer (RNFL)
analysis and visual fields.
RESULTS : Sixty-nine Black African patients (138 eyes) with
large discs and large cups were evaluated. Forty-one patients
(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 nine
patients who were previously misdiagnosed with glaucoma and
who had received treatment.
VDH ranged between 1.9 and 3.2 mm (mean±SD, 2.3±0.26 mm).
The distribution analysis of VDH measurements noted the
largest cluster around 2.3 mm. CCT ranged between 454 μm and
618 μm (mean±SD, 516±37μm). Of the 138 eyes, 107 (77.5%) had
CCT<544 μm.
CONCLUSION : Large CDR in relation to large disc size may
be normal physiological cupping. It can be misdiagnosed as
glaucomatous if objective RNFL analysis is not carried out. In
this study, nine (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 of eyes
(77.5%) had thin corneas (CCT<544 μm).
