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Y. Alster, Y. Manor, O. Rafaeli; Hyperacuity Hill of Vision in Central Visual Field Testing Among Patients With Intermediate AMD. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5523.
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© ARVO (1962-2015); The Authors (2016-present)
While hyperacuity sensitivity is known to decrease with eccentricity, differences between upper and lower or temporal and nasal visual field (VF) have not been described. The home version of the Preferential Hyperacuity Perimeter (PHP) is intended to be used as a monitoring tool quantifying the VF of intermediate AMD patient at risk for developing CNV and assess if significant VF deterioration has occurred. The aim of the present study was to assess the hill of vision of patients with intermediate AMD as measured by the Home-PHP
Patients with intermediate AMD were tested repeatedly twice a week for a month with the Home-PHP. The hyperacuity pattern is collinear pattern consisting of 25 units. Up to 3 units are deviate offset at different magnitude and the examinee task is to locate the deviation and mark its location, using a standard PC mouse. The threshold level of a signal is defined by the smallest degree of misalignment that can be seen and ranged from 0.34 to 0.04 degrees. The signals, present horizontally or vertically, are flashed for 160 ms and are presented at a 0.75 degrees resolution to the central 14 degrees of the VF. The sensitivity level (degree of misalignment) of the test is adjusted constantly by the examinee performance to the lowest supra-threshold level. For analysis purposes, normal responses were defined when the deviation was marked correctly by the subject while abnormal responses were defined as such when either the deviation was marked incorrectly or was if no marking was performed
Thirty-eight intermediate AMD patients (41 eyes) participated in the study after signing an informed consent. To the entire cohort a total of 55,357 signals were projected evenly divided between all 4 quadrants. In the upper VF the ratio normal to abnormal ration was 1:5.3 and 1:4 in the lower VF (p< 0.001). The same differences in ratio were found along all sensitivity layers. No difference was found between nasal and temporal fields
To the best of our knowledge, this is the first time where altitudinal hemifield differences in hyperacuity have been recorded. Possible explanation is that intermediate AMD patients or aged matched patients have a greater functional damage in the lower VF. Testing of normal and younger subjects will challenge this later assumption such differences should be taken into account when analyzing the hyperacuity visual fields. The exact population in which such consideration should be considered requires further investigation.
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