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A Journal on Ophthalmology
Minerva Oftalmologica 2003 March-June;45(1-2):33-8
Peripheral low vision quantification: comparison between two binocular programs in Humphrey perimetry
Morescalchi F., Gandolfo E., Gandolfo F., Zinzini E.
Aim. The Italian Government recently passed a bill that recognised the peripheral visual impairment. This new article gave legal value to the disability caused by the visual field constriction and classified the peripheral visual damage into 6 categories: 1) no peripheral low vision (PLV): binocular visual field residual (BVFR) >60%; 2) slight PLV: BVFR < 60%; 3) moderate PLV: BVFR <50%; 4) severe PLV: BVFR <30%; 5) relative peripheral blindness (with residuum): BVFR <10%; 6) absolute peripheral blindness: BVFR <3%. Several investigations have used the Esterman binocular visual field test, as configured for the HFA II, in trying to correlate its score with other measures of visual function. Many of these studies didn't find strong correlations between the Esterman binocular score and real visual disability reported by patients with severe visual field defects. The purpose of this work was to develop an automated program best correlated with visual impairment, specific for functional percentage scoring of the binocular visual field, suitable for the Humphrey field analyser II. The new test, called Visual Field per cent (VF%), can be easily created as a custom program in the Humph-rey HFA II.
Methods. Thirty-six patients with bilateral abnormal visual field due to advanced glaucoma, retinitis pigmentosa or optic neuritis were examined. Monocular and binocular visual field tests were obtained using a Humphrey HFA II. The proposed binocular scoring strategy (VF%) and an Esterman binocular test was performed during the same visit. A monocular visual field test, performing a 24-2 test procedure was conducted within 3 months by the binocular test.
Results. The Esterman program used the single stimulus intensity of 10 dB; the high intensity of this stimulus was correlated to a higher number of false negative visual fields. In the custom program VF% the screening 3-zone strategy was more sensitive and the relative weight of the central area (64% of test location) seemed to be more adequate. The sensitivity of this test has been confirmed by the comparison with monocular VF and by the direct correlation of the ''global score'' with the mean deviation of the better eye. This parameter correlated well to the reported visual impairment of low vision patients. The same correlation has not been found with the Esterman ''global score'' in our group of patients.
Conclusion. The custom binocular program VF% appeared to be enough accurate and sensitive in quantifying peripheral visual impairment for legal purposes of the recent bill.