Neural rim area declines with increased intraocular pressure in urban Americans
R. Varma, S. C. Hilton, J. M. Tielsch, J. Katz, H. A. Quigley and A. Sommer
Doheny Eye Institute, University of Southern California, Los Angeles, USA.
OBJECTIVE: To determine intraocular pressure (IOP)-related differences in
the neural rim area among urban Americans without known optic nerve
disease. DESIGN: Population-based prevalence study conducted in 16 cluster
areas in East Baltimore, Md. PARTICIPANTS: A population-based sample of
1521 black and 1851 white individuals aged 40 years and older without
evidence of optic nerve disease. MAIN OUTCOME MEASURE: Intraocular
pressure-related differences in neural rim area, neural rim area-to-disc
area ratio, and cup-to-disc ratio. RESULTS: We analyzed optic disc
photographs using the Imagenet system (Topcon Instrument Corp of America,
Paramus, NJ). After adjusting for age and disc area, white Americans had a
6% decrease in neural rim area for every 10-mm Hg increase in IOP (P =
.0001). In black Americans, there was a quadratic relationship between
neural rim area and IOP, with little decline with IOP up to approximately
17 mm Hg, after which neural rim area declined significantly with higher
IOP (P = .001). Similarly, the neural rim area-to-disc area ratio decreased
and the vertical cup-to-disc ratio increased with increasing IOP in both
black and white Americans. CONCLUSIONS: The higher the level of IOP, the
smaller was the amount of neural rim tissue in the optic disc for both
black and white Americans. However, the relationship between IOP and neural
rim area was different in whites and blacks.
