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Mary Lou Jackson, Alexandra Selivanova, William Seiple; Do patients with Stargardt maculopathy fixate eccentrically or with their fovea when asked to look straight ahead?. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):546.
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© ARVO (1962-2015); The Authors (2016-present)
To assess if patients with Stargardt maculopathy change fixation location when asked to look straight ahead during fixation testing.
Patients diagnosed to have Stargardt maculopathy had two 5-second fixation tests using SLO-based macular perimeter. During one test the patient was asked to,“Look at the cross” (LC). During the second the patient was asked to, “Look straight ahead even if you do not see the cross” (LS). Thirteen control subjects were tested under the same conditions. Foveal location was determined with OCT topographies scans in control subjects. The mean position of anatomic fovea relative to the disk in controls was used to localize the position of the fovea in Stargardt subjects. The mean vector length, mean angle, and angular dispersion from anatomic fovea to fixation for each subject under each condition were calculated. Data about visual acuity, contrast sensitivity and time since diagnosis was taken from the medical record.
Records of 38 patients with Stargardt maculopathy were reviewed. Fixation was most frequently in the superior retina (74% LC condition and 67% LS condition). The average PRL eccentricity was 11.02 degrees for the LC condition (median = 9.52 degrees) and 7.84 degrees for the LS condition (median = 5.9 degrees). This difference was statistically significant (P < 0.001). Sixty-nine percent of subjects had inter-ocular PRLs that were < 10 degrees apart. Approximately 43% of eyes did not statistically change fixation when asked to look straight ahead. When fixation did shift, the magnitude of the shift was correlated with the PRL eccentricity determined when asked to look at the cross (OD, r = -0.69, P < 0.001; OS, r = -0.76, P < 0.001; OU, r = -0.66, P < 0.001). The distance moved under the different conditions (LC and LS) was not correlated with age, disease duration, age of disease onset, visual acuity, contrast sensitivity or BCEA.
Even after longstanding disease and established ability to use eccentric fixation, some patients will move their fixation from their preferred retinal locus (PRL) when asked to look in the direction that they believe is straight ahead. Verbal directions can change fixation in patients with Stargardt maculopathy and, therefore, may impact measured visual function, such as visual acuity assessments or PRL assessment.
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