FP1172 : Antero-Nasal Transposition of Inferior Oblique (Antio) in Dissociated Vertical Deviation

Dr. Pramod Kumar Pandey P04428, Dr. Ranjith PC, Dr. Vishaal Bhambhwani, Dr. C. Aparnaa

INTRODUCTION:

DVD has been know by various names like double vertical strabismus, dissociated vertical divergence. DVD is characterized by elevation, abduction and excyclotorsion of the nonfixing eye without corresponding hypotropia in the other eye. It may be phoric or tropic, symmetric or asymmetric, unilateral or bilateral, comitant or incomitant.Upward drifting and outward movement of the occluded eye on cover testing demonstrate it. DVD is usually, but not always, bilateral but asymmetrical.

Prevalence and incidence of DVD is variable in different studies. DVD is known to be strongly associated with infantile strabismus and with manifest latent and latent nystagmus, especially latent nystagmus with a torsional component.DVD is more commonly associated with infantile esotropia than exotropia.

Many patients with DVD have anomalous head posture. Both ipsilateral and contralateral head tilt have been observed, which may mimic superior oblique palsy and congeal Park’s three-step test.DVD is also associated with sensory deviation as acquired entity after prolonged occlusion or after cataract extraction.DVD generally presents before 12 months of age.

Dissociated strabismus complex includes horizontal, vertical and torsional component of dissociated deviation.

DVD is diagnosed by Prism Under Cover Test (PUCT). The reversed fixation test was developed to measure dissociated vertical deviations and later adapted for dissociated horizontal deviations. This test makes it possible to rule out simulating conditions. DVD measured within ± 7 PD in abduction, the primary position and horizontal gaze is termed Comitant DVD. Incomitant DVD refers to a measurable disparity in magnitude of DVD in adduction, abduction and primary gaze.

Various non-surgical treatment options have been proposed to alleviate DVD. Observation is preferable in DVD that is controlled as phoria and for smaller deviations occurring infrequently. Steps to encourage fusion or bifixation by providing clear images by optimal spectacles.

Switching fixation by occluding the fixing or dominant eye, to encourage fixation to improve DVD in the non-preferred eye.

Surgery is often indicated when DVD is increasing in frequency, a phoric deviation is gradually converting to a manifest form and for anomalous head posture.Surgical treatment of co-existing deviation has limited role in DVD. Surgery on cyclovertical muscles remains main stay of treatment.

Surgical procedures mentioned in literature over the years to control DVD include, recession of superior rectus, combined recession of superior rectus with resection of inferior rectus muscle, posterior fixation of superior rectus with or without the recession of these muscles, superior oblique surgeries, anterior displacement of inferior oblique insertion which may or may not be combined with superior rectus muscle recession.

There is no single best procedure for treatment of DVD because the pathology of DVD is supra nuclear and we are trying to overcome it at infra nuclear level.

Initial surgical procedures were based on superior rectus recession up to 4mm, resulted in undercorrections.Moderate recession of superior rectus (3-5mm) combined with a posterior fixation of superior rectus muscle had better results.Large superior rectus recessions (4-9 mm) performed depending on the amount of DVD had good results. Complications noted were of under and over corrections.

Surgeries performed unilaterally had the risk of DVD developing in the other eye.

Posterior fixation of superior rectus done alone or in combination with SR recession alone is not recommended for DVD due to high failure rate.

Resection of inferior rectus in DVD had good results. But complications like lid retraction, postoperative hypotropia, fat pad migration and re-surgeries were common.

Inferior oblique weakening procedures (recession, myectomy or anterior transposition) were formerly believed to be less effective in DVD management.

Inferior oblique muscle’s neurovascular bundle as a new functional origin after anterior transposition of inferior oblique (ATIO) was studied by Stager et al and found to be effective in controlling DVD. ATIO had complications like up gaze deficit, divergence in upgaze and false appearance of inferior oblique overaction.

ATIO in incomitant DVD, inferior oblique overaction and V pattern appears to give predictable and stable results, but with low incidence of postoperative A pattern and upgaze deficits.

Anterior and nasal transposition of inferior oblique in DVD had excellent postoperative correction of DVD, inferior oblique overaction and V pattern.

Few patients developed postoperative hypotropia at 6 months.

So we have a host of surgical procedures for DVD, yet there is no best surgical procedure.

AIMS AND OBJECTIVES:

  1. To evaluate the outcomes following anterior and nasal transposition of inferior oblique muscle on vertical deviation, in DVD.
  2. To study the possible outcomes of the above-mentioned procedure for dissociated vertical deviation.

MATERIAL AND METHODS:

Study was conducted in the Department of Ophthalmology, Maulana Azad Medical College and Guru Nanak Eye Centre, New Delhi.

Study population:

Study will comprise of 14 patients aged 5 years or more, diagnosed as DVD by prism under cover test, attending the outpatient department and squint clinic of Guru Nanak Eye Centre(GNEC), Maulana Azad Medical College, New Delhi.

Informed consent:

Informed consent for the study was obtained after the nature and possible consequences of the study were explained.

INCLUSION CRITERIA:

  • Age more than 5 years
  • Dissociated vertical deviation of more than 10 Prism Diopter (PD) in one or both eyes by using prism under cover test.
  • Incomitant DVD.

EXCLUSION CRITERIA:

  • Associated mechanical strabismus.
  • Previous strabismus surgery for DVD.
  • “A” pattern strabismus.
  • Concurrent neurological involvement
  • Associated cyclovertical muscle palsy.

STUDY METHODOLOGY:

Patients with DVD attending GNEC strabismus services will be included in the study ANTIO will be done on the eye manifesting larger DVD.

Concurrent horizontal deviations will be treated by surgery as appropriate in the same sitting.

Detailed clinical history was taken which included:

  1. The age of onset of deviation, deviation if constant or intermittent/variable angle, course, treatment taken and response to treatment.
  2. History of prematurity, low birth weight, birth asphyxia was specifically asked for.
  3. History suggestive of neurological involvement or cerebral visual impairment was elicited.
  4. History of decrease of vision and its correction with glasses, if any, or any amblyopia therapy if undertaken in past.
  5. History of previous strabismus surgery.
  6. Family history of strabismus or craniofacial anomalies.
  7. History suggestive of any abnormal head posture, double vision or nystagmus
  8. History of previous ocular/head trauma and other concurrent illness and treatment taken.

Examination included:

  1. Facial features to rule out craniofacial disorders or any pseudo strabismus.
  2. Any neurological involvement in the form of seizures / ataxia / mental retardation or signs of cerebral visual impairment likehydrocephalus and periventricular leukomalacia.
  3. Unaided uniocular and binocular visual acuity with Snellen’s chart as well as logmar acuity was documented.
  4. Refraction was done under cycloplegia (using atropine in < 10 years and cyclopentolate in > 10 years) as per age. Glasses were prescribed as appropriate and aided visual acuity recorded (uniocular and binocular). Subjects were assessed after 4 weeks. Amblyopia therapy was undertaken as appropriate.
  5. Anterior segment and fundus was evaluated for any pathology.
  6. Ocular motility was evaluated for saccadic, smooth pursuit, vestibulo-ocular, version and vergence movements.Smooth pursuit asymmetry tested clinically.
  7. Features of infantile deviations were noted i.e. smooth pursuit asymmetry, latent nystagmus, primary inferior oblique over-action, superior oblique overaction.
  8. Deviationswere assessed by cover-uncover test, simultaneous prism cover test, prism alternate cover test and horizontal/vertical reversed fixation test performed at 6 meters with BCVA.
  9. Binocularity
  10. Fusion and suppression were assessed by worth’s 4 dot test and synaptophore.
  11. Stereopsis was analyzed by Titmus fly test
  12. Torsion was evaluated subjectively by double Maddox rod test and objectively by fundus photography as indicated.
  13. Pattern strabismus was noted if any. A pattern and V pattern were described as upgaze and downgaze difference of more than 10 and 15 PD respectively.
  14. DVD was quantified by Prism Under Cover Test and vertical reversed fixation test and latent nystagmus assessed for frequency, amplitude, intensity and other characteristics.
  15. Forced duction test, Guyton’s exaggerated traction test and reverse fixation test will be done as appropriate.

SURGICAL TECHNIQUE:

After taking full informed and written consent, ANTIO on the eye with larger DVD will be done in which inferior oblique is isolated to its insertion through an inferior cul-de-sac approach. 6-0 vicryl sutures will be used to secure the muscle in a bunched fashion. IO muscle’s posterior and temporal fibers will be transposed to 2mm below and 2mm nasal to the medial edge of the insertion of inferior rectus while the anterior fibers will be transported to 2mm medial to the posterior & temporal fibers of IO.Conjunctiva will be sutured with 8-0 vicryl sutures. Patient will be on steroid eye drops 6th hourly & ointment at bedtime post operatively. Postoperative follow up will be done on 1st post-op day, 1 week, 3weeks, 6 weeks and 12 weeks.

Postoperative follow up included assessment of:

  • Ocular motility,
  • Ocular alignment in primary position,
  • DVD,
  • Pattern strabismus,
  • Torsion by fundus photography,
  • Complications, if any.

OUTCOME ASSESMENT:

PRIMARY:

Amelioration of DVD in both groups will be evaluated and residual DVD up to 4 PD will be taken as successful outcome.

SECONDARY:

  1. Evaluationofpreoperative pattern strabismus and torsion and influence of surgery on it.
  2. Assessment of adverse outcomes will also be assessed.

RESULTS

PARAMETERS:

Age distribution:         

Mean age was 15.0 ±  7.4 .

Age of the subjects ranged from 6 to 30 years

Gender distribution:

10 females and 4 males each.

Horizontal deviation:

10 patients had esotropia and 4 had exotropia.

Primary Inferior Oblique overaction:

10 patients had primary inferior oblique overaction.

Pattern:

Preoperatively 10 subjects had significant V pattern.

Rest had no pattern.

The mean pre operative pattern was 15.00 ± 10.0 (range 0 to 25 PD)

All 10 patients with inferior oblique overaction also had significant V pattern

No patient had significant abnormal pattern post operatively.

The postoperative pattern was 3.08 ± 4.87

Fundus Torsion (objective: by fundus photography):

Pre-op torsion (eye with larger DVD): 8 subjects had extorsion.

Rest subjects had normal torsion..

The pre-operative torsion in the eye with larger DVD was 10.21 ± 3.36 degrees (range 5.32 to 14.78)

The pre operative torsion in the eye with smaller DVD was 6.67 ± 1.67

Postoperative fundus torsion (objective):

Post-operatively, none of the subjects developed abnormal torsion

The post-operative extorsion in eye with larger DVD was 5.38±1.34

The postoperative torsion in eye with smaller DVD was 6.93±1.97

The postoperative torsion corrected in degrees was 4.58 ± 4.

The postoperative torsion in the eye with smaller DVD was 6.93 ± 1.

PREOPERATIVE FUNDUS TORSION (LE)


POSTOPERATIVE FUNDUS TORSION (LE)
DVD:
Pre-op DVD in the eye with larger DVD was 26.6 ± 2.8 PD
The pre-op DVD in the eye with smaller DVD was 10 ± 2.72 PD
Post-op DVD in the eye with larger DVD was 3.86 ± 1.46 PD (range 2 to 8 PD)
The amount of post operative DVD corrected was 22.8 ± 3.7 PD

There was a success rate of 92.9 %
COMPLICATIONS: Post operative hypotropia and elevation deficit:
There were no cases of postoperative hypotropia in primary position.

Horizontal muscle surgery and surgery in fellow eye for DVD:
All the subjects had appropriate surgeries to correct their horizontal deviations in both the groups.
Surgery for the fellow eye for DVD was done in 8 subjects
Of these superior rectus recession was carried out in 4 patients
Other patients(4) had recession of the inferior oblique muscle

DISCUSSION

Dissociated vertical deviation (DVD) is a component of dissociated strabismus complex (DSC), which also includes dissociated horizontal deviation (DHD), dissociated torsional deviation (DTD), latent nystagmus (LN) and subnormal binocularity. Although DVD is the most clinically significant component of DSC, DHD may be more prominent in some patients.

• Every DVD is not to be treated.
• There is no algorithmic approach for treating DVD.
• DVD is mostly alleviated, not eliminated.
• Earlier there was mainly nonsurgical attitude for treating DVD in term of glass prescription or amblyopia therapy.
• Indications for treating DVD include abnormal head posture, manifest deviation, and risk of amblyopia, cosmetically unacceptable deviation.
• Surgery of co-existing horizontal deviation has limited role in treatment of DVD. Surgery on cyclovertical muscles remains main stay of surgical treatment

In this prospective study, 14 consecutive subjects over 1 year having DVD of ≥10PD enrolled. The present study is trying to compare success rate and correction of DVD by ANTIO, study important parameters mainly- Pattern, Torsion and document adverse surgical outcomes.

Age and Gender distribution:

• In present study, inclusion criteria of Age was >5 years.
• We included 14 subjects in the study over a period of 1 year. Mean age was 15.0 ± 7.4 years.
• We excluded subjects having previous surgery.
• Higher Age in our study probably reflects that subjects < 5 years were excluded and late presentation of motility disorders in our society.
• In this study, there were 10 females and 4 males.
• We found strong female preponderance for which we have no explanation.
• It could be due to small sample size.

Primary IOOA, Horizontal Deviation:
10 subjects (71%) had primary IOOA.
We excluded subjects with previous surgery and less than 5 years. During correction of vertical component of dissociated deviation, horizontal component should also be taken care of.
DVD:
In our study Pre-Op DVD in Group A was 26.6 ± 2.8 PD
The amount of pre-op DVD included in this study is more than the known studies
Post-Op DVD was 3.86 ± 1.46 PD
In various studies the success rates for ANTIO was 60-80%
The success rate was defined as post-op DVD ≤ 4 PD.
92.9% success rate was noted in our study group
The amount of post operative DVD corrected was 22.8 ± 3.7 PD
Pattern:
Literature is limited on Pattern strabismus and DVD.
Primary IOOA often has been distinguished from DVD in adduction.
However correlation of SOOA and A pattern find frequent mention.
Pre-operatively, in Group A, 10 subjects had V-pattern.
Mean pre-op pattern was 15 ± 10.0 PD.
V pattern was found more than no pattern and A pattern, having been excluded.
Post-operatively none of the subjects developed significant A
Mean post-op pattern was 3.08 ± 4.87 PD
In this present study ANTIO improved V pattern better than ATIO. However it did not reach statistical significance.

Fundus Torsion (Objective):
Literature is scarce regarding torsion findings in DVD subjects both pre-op and post-op in ANTIO.
Pre-op Torsion, 8 subjects had extorsion.
Rest subjects had no abnormal torsion.
Postoperatively none of the subjects developed abnormal torsion.
Change of torsion was from 10.12±3.36 (pre-op) to 5.38 ± 1.34 (post-op)
Correction of torsion was 4.58 ± 4.26
According to the results in this study we found that ANTIO improved extorsion better

Relationship between Pattern and Torsion (Objective):
10 subjects had V pattern and it corresponded to extorsion in 8 subjects preoperatively.
2 subjects had V pattern with no corresponding extorsion.
4 subjects had no pattern.
Post operatively 6 subjects had their V pattern corrected and 4 subjects had residual V pattern post operatively that was not significant (≤15 pd). Subjects with no pattern did not develop any abnormal pattern post operatively.
V pattern and extorsion were corrected with ANTIO better.

  • Adverse surgical outcomes:
    Complications of surgery comprising of any ptosis, upper lid retraction, alteration of palpebral fissure width, limitation of up gaze, oblique dysfunction or overcorrection describe in over studies.
    2 subjects had postoperative elevation deficit.
    Two patients had consecutive esotropia from exotropia after surgery.
    There were no gross lid aperture changes noted. We did not find any other adverse outcome. Since our groups comprise only 14 subjects, no reliable conclusions may be drawn regarding adverse outcomes following surgical procedures employed.
    CONCLUSION
  • This is a prospective randomized controlled study comprising 14 subjects diagnosed as DVD (≥ 10 PD).
  • Mean age was 15.0 ± 7.4 years.
  • There were 10 females and 4 males in our study.
  • Eyes with larger DVD had poor BCVA.
  • DVD was associated with infantile deviation in 10 subjects. DVD was commonin subjects with esotropia (67.85%) than exotropia (32.14%). It was not seenas an isolated anomaly.DVD was associated with: LN (32.14%), primary IOOA (71%)
  • Pre-Op mean DVD was 26.6 ± 2.8 PD (range, 22-32 PD)
  • Pre-Op, in Group A, 10 subjects had V-pattern Rest had no pattern. Pre-op mean pattern was 15 ± 10.0PD
  • Pre-Op Torsion, 8 subjects in each group had extorsion. Rest had no abnormal torsion.
  • Post-Op mean DVD was 3.86 ± 1.46 PD
  • The amount of post operative DVD corrected was 22.8 ± 3.7 PD
  • Success wasdefined as DVD <4 PD at 12 weeks follow up after surgery  92.9% success rate was noted.
  • V pattern in 6 subjects were corrected and 4 subjects had residual V pattern (<15 PD).
  • 8 subjects had correction of extorsion.
  • Extorsion is affected more by ANTIO. It correlates well with pattern strabismus.
  • 2 subjects had postoperative elevation deficit.
  • Surgical results were stable at 12 weeks.
  • Larger DVD(> 20 PD) is better corrected by ANTIO
  • ANTIO is more effective in correction ofV pattern and extorsion, however it did not reach statistical significance.
  • The drawback of our study was smaller number of subjects and shorter follow up period.
  • We recommend prospective study with larger number of subjects with longer follow-up period

 

 

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