Dr. Kanwar Mohan MS., received his postgraduate degree in Ophthalmology from the Postgraduate
Institute of Medical Education and Research, Chandigarh, India in the year 1980, and subsequently did
senior residency, held various faculty positions and headed the Squint Clinic for nearly 10 years there.
Thereafter, he shifted to private sector and started an exclusive strabismus practice in the year 2000 and
is continuing to do so. Dr. Mohan has published 75 research papers in peer-reviewed journals with 53 of
them in international journals. In addition to research presentations in national and regional
conferences, he has presented his research work in ‘International Strabismological Association’
conference at Sydney, Australia, in 2002 and ‘International Neuro Ophthalmology Society’ meeting at
Geneva, Switzerland, in 2004, and was invited as ‘Guest Speaker’ at ‘Indonesian Ophthalmologists
Association’ conference at Yogyakarta, Indonesia, in 2003. He has been a reviewer for the J AAPOS,

Saudi Arabia Journal of Ophthalmology and Middle East Journal of Ophthalmology, and has also held
positions as General Secretary, Vice President and Chairman, Scientific Committee of the
Strabismological Society of India.

1) Do you feel recommending MRI image study prior to the surgical procedure is:
a) Indispensable
b) Useful but not indispensable
c) I would not recommend prior MRI image due the anesthesia damage
My answer is ‘b’. Due to a very large esotropia, absence of abduction and no narrowing of palpebral fissure in adduction, I would consider the diagnosis of 6th nerve palsy. No history of trauma, and the absence of signs and symptoms of raised intracranial pressure make me strongly think ‘Congenital’ as the etiology of 6th nerve palsy in this child. Though MRI image study will not help in the management of this case, it will help in finding out any congenital etiology such as the absence of 6th nerve, and any associated intracranial congenital anomaly. Thus MRI image study will be useful but not indispensable, and I would feel recommending it prior to surgical procedure in this child.

2) What is your preferred surgical technique for VI Nerve palsy?
a) Carlson Jampolsky
b) Superior rectus transposition combined with Medial Rectus recession
c) Vertical muscle transposition augmented with lateral fixation (Foster)
d) Nishida Muscle Transposition
My answer is ‘d’. My preferred surgical technique for 6th nerve palsy is Nishida muscle transposition without tenotomy and muscle splitting. There is less interference with the anterior segment circulation with this procedure because there is no tenotomy, no muscle splitting, only one third of the muscle width is ligated, and the muscle sutures are placed apart from the anterior ciliary vessels. Thus there is a less risk of anterior segment ischemia and this procedure is safe. In addition, the chances of development of a vertical imbalance are much less because the vertical action of the superior and inferior rectus muscles is not affected. Therefore, I prefer this procedure for treating 6th nerve palsy.

3) What is the occlusive treatment option proposed for this case?
a) 2 hours / day
b) 4 hours / day
c) 6 hours / day
d) 8 or more hours /day
My answer is ‘d’. I believe and follow that a full-time occlusion gives a faster and better improvement in vision as compared to some hours of occlusion. Hence I would advise at least 8 or more hours of occlusion per day in this child.

4) Do you think that VI Nerve palsy is a benign entity?
I do not think that 6th nerve palsy is a benign entity in all situations. Patients with 6th nerve palsy due to medical conditions such as diabetes, hypertension etc. do not require neurological investigations, and I would consider it a benign entity in these patients. However, patients with 6th nerve palsy due to head trauma require a neurological work up and neuro imaging studies to assess the extent of craniocerebral injury, and I would not consider it a benign entity in this situation. In the absence of medical conditions mentioned above, a 6th nerve palsy may be a sign of serious intracranial pathology, and I would not consider it a benign entity in such patients, and would order neurological investigations.

5) What is your approach to diagnose and treat a patient with VI Nerve palsy pattern?
My approach to diagnose a 6th nerve palsy is as follows :
I would make a diagnosis of 6th nerve palsy if a patient has the following cardinal signs :
i. Esotropia in primary position and increasing in the gaze of the involved lateral rectus muscle
ii. Limitation of abduction
iii. Head turn to the side of the involved lateral rectus muscle
iv. Presence of uncrossed diplopia with more separation of images in the gaze of the involved lateral rectus muscle
v. Absence of narrowing of palpebral fissure in adduction, and esotropia proportionate to the extent of abduction limitation would differentiate it from the Duane’s Syndrome.
My approach to treat a 6th nerve palsy
i. I would assess visual acuity to detect amblyopia in younger children and if present, would treat it with occlusion therapy.
ii. I would advise occlusion of the normal eye to give relief from diplopia and to avoid development of contracture of the medial rectus muscle, and would wait for at least 6 months for a natural recovery. In the waiting period, I would do measurement of esotropia, assessment of abduction improvement, and diplopia charting to assess the extent of separation of diplopic images every 2 months. If there is no improvement at all after 6 months or no further improvement for consecutive 6 months, I would consider surgical intervention as follows:
a. Partially recovered 6th nerve palsy – I would do forced duction test (FDT) to assess the stiffness of the medial rectus muscle, and perform conventional medial rectus recession and lateral rectus resection depending upon the amount of esotropia. If the medial rectus muscle is tight, I would reduce the amount of recession by 1-2 mm.
b. Unrecovered 6th nerve palsy – I would do FDT to assess medial rectus muscle stiffness. Then I would do Nishida procedure without tenotomy and splitting, and would add medial rectus muscle recession if this muscle is tight or esotropia is more than 40 prism diopters.