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Short-wavelength automated perimetry in low-, medium-, and high-risk ocular hypertensive eyes. Initial baseline
C A Johnson1, J D Brandt, A M Khong
1Optics and Visual Assessment Laboratory, Department of Ophthalmology, School of Medicine, University of California, Davis.
Objective:
To examine the relationship between the prevalence of short-wavelength sensitivity losses in the central 30 degrees visual field and risk factors for development of glaucomatous visual field loss in ocular hypertension.
Design:
A modified Humphrey Field Analyzer was used to perform standard automated perimetry and short-wavelength automated perimetry (SWAP), which is a technique that isolates the activity of short-wavelength-sensitive ("blue") mechanisms. In addition, an assessment of the risk of developing glaucomatous visual field loss was determined, based on a validated model that utilized intraocular pressure, a family history of glaucoma, age, and the vertical cup-to-disc ratio.
Patients:
Both eyes of 232 ocular hypertensive patients were examined and compared with results from an age-matched control group of normal subjects. Both ocular hypertensive patients and normal subjects had to have normal visual fields on standard automated perimetry, good visual acuity, and no evidence of other ocular or neurologic disease or surgery. Intraocular pressure in the ocular hypertensive patients was 21 mm Hg or greater OU (without medication), and it was less than 20 mm Hg OU in normal control subjects.
Results:
Less than 10% of the low-risk ocular hypertensive eyes had a SWAP deficit, as compared with 20% of the moderate-risk and 33% of the high-risk ocular hypertensive eyes. Intraocular pressure and a family history of glaucoma showed no meaningful relationship with the prevalence of SWAP deficits, but both age and the vertical cup-to-disc ratio demonstrated a strong association with the SWAP abnormalities.
Conclusions:
The SWAP results that were found in the ocular hypertensive eyes were associated with other risk factors that have been reported to be predictive of the development of glaucomatous visual field loss, especially the vertical cup-to-disc ratio and age. These findings support the notion that the SWAP deficits represent early glaucomatous damage and may be related to early changes that occur at the optic nerve head.