الفهرس 
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Abstract
Nystagmus is a condition of involuntary eye movement, acquired in infancy or later in life, that may result in reduced or limited vision. Due to the involuntary movement of the eye, it is often called ”Dancing Eyes”.
The amplitude and the frequency may decrease or the nystagmus may disappear completely in one position of gaze. This may cause the patient to assume an anomalous head posture to improve visual acuity with the eyes in the position of least nystagmus (null point) .
Displacement surgery aims to reduce the amplitude of nystagmus with either improvement of visual acuity or reduction of bothersome head posture.
This is a small prospective clinical interventional series study carried out from September 2014 to September 2015 on fifteen patients with congenital nystagmus, null point and anomalous head posture. We studied the effectiveness of displacement surgery in damping of ocular oscillation and management of compensatory head posture in patients of congenital nystagmus and null zones.
All cases in this study were subjected to the following steps:
Pre-surgical assessment: including;
History : age of the patient, age at onset of the complaint, family history of nystagmus and maternal history of prematurity.
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Examination: refraction, assessment of visual acuity and best corrected visual acuity in the primary position and position of minimal nystagmus if possible,type of Nystagmus whether pendular or jerky, presence of null point, assessment of abnormal head posture if present,complete ocular motility examination, cover test and prism cover test for heterophorias.
Surgical procedure: Extra ocular muscles recession was used as a weakening technique and extra ocular muscles tucking was used as a strengthening technique.
Post-surgical Follow up: The patients were seen postoperatively one day ,one week and one months following surgery. In the follow up the patients were examined for visual acuity and best corrected visual acuity whenever possible, presence of nystagmus and if the amplitude is deceased, abnormal head position, cover test and ocular motility.
In our study the average of age is 8 ± 2 ranging (4-10) years. Most of cases (73.30%) start at birth, the remaining cases (26.70%) start within 6 months of life.
As regard the visual acuity the average of pre-operative BCVA in primary position is 0.3±0.15 ranging (0.1-0.6) and BCVA in null zone position is 0.6±0.1 ranging (0.4-0.8). the average of post-operative BCVA in primary position is 0.6±0.1 ranging (0.4-0.8) . we found that there is a statistically significant difference between the Pre-operative
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BCVA in Primary Position and Post-operative BCVA in primary position (P-value = 0.001) with average vision gain in primary position 0.3±0.1 ranging (0.1- 0.4).
As regard the null zone position, 53.30% of our patients have it on levoversion, 33.30% of our patients have it on dextrovoversion, 6.70% of our patients have it on deorsumversion and 6.70% of our patients have it on convergnce.
As regard the pre-operative AHP , 6.7% of our patients has no AHP ( nystagmus intensity decrease on convergence ), 26.7% of our patients has Face turn to the left 30°, 6.7% of our patients has Face turn to the left 45, 33.3% of our patients has Face turn to the right 30°, 20.0% of our patients has Face turn to the right 45°and 6.7% of our patients has chin elevation 20°.
In the post-operative follow up period 80.0% of our patients has no AHP, 6.7% of our patients has Face turn to the left 15°, 13.3% of our patients has Face turn to the right 15° we found that there is a statistically significant difference between pre-operative and post-operative Abnormal Head positions (P-value = 0.044). 80.0% of our patients has no residual AHP and 20.0% has residual AHP.
We also found that there is areduction in the nystagmus intensity in 80.0% of our cases and in 20.0% there was no reduction.
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We concluded from this study that the displacement surgeries (e.g. Kestanbaum procedure) is an effective procedure for correction of abnormal head posture, improving the visual acuity in the primary position and damping of nystagmus in cases of congenital nystagmus with null point and abnormal head position .