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Richard W Hertle, Cecily Kelleher, David Bruckman, Neil McNinch, Isabel Alvim Ricker, Rachida Bouhenni; Non-Visual Components of Anomalous Head Posturing (AHP) In Patients with Infantile Nystagmus Syndrome (INS). Invest. Ophthalmol. Vis. Sci. 2020;61(7):5093.
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To investigate the visual and non-visual etiologies of anomalous head posturing in patients with INS.
This is a prospective, cohort analysis of clinical and AHP data in 34 patients with INS. Data collected included routine demography and surgical procedure. Main outcome measures included: 1) binocular, best-corrected, LogMAR visual acuity in the null position (BVA), 2) AHP in degrees while measuring best-corrected binocular acuity, 3) AHP in degrees while being prompted to position their head in “the most comfortable position.” 4) response to question regarding their subjective sense of straight in their AHP and 5) with their head straight. Paired t-test was used to determine significance in objective vs. subjective AHP.
Age ranged from 10-51 yrs (mean 16.5 yrs). 56% were male. 53% had BVA > 20/40. Associated systemic or ocular system deficits were present in 88%, including; developmental delay (12%), neuropsychiatric disease (29%), albinism (50%), strabismus (32%), amblyopia (24%), optic nerve and/or retinal disease (44%) and refractive error (94%), 74% (25 pts) had eye movement recording confirmed eccentric null position and a > 10 degree AHP, 15% (5 pts) had a periodic or aperiodic component. Mean AHP of all patients during BVA testing was (-0.88 roll, -3.35 pitch, -4.18 yaw). Mean AHP for patients with a > +/-10 degree AHP was (-10.50 roll, -13.15 pitch, -27.30 yaw). There was a significant non-congruous response during subjective response to head posturing with most sensing their head as straight when physically not and vice-versa (p=0.00011,table).
Clinical AHP in patients with INS exists in all 3 dimensions of roll (lateral flexion), pitch (chin lift), and yaw (cervical rotation). Although the visual system may be causally related to the onset of an AHP in patients with INS due to an eccentric null zone, its persistence over time or after surgical intervention is likely due to a combination of visual (e.g. nystagmus, strabismus) and non-visual( e.g. abnormal egocentric localization and/or musculo-skeletal symmetry) factors.
This is a 2020 ARVO Annual Meeting abstract.
2 X 2 table showing subjective responses to head posturing
Figure of cosolidated patient AHP in 3-dimensional space
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