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Strabismus

Strabismus is defined as a misalignment of the eyes. Strabismus also called as squint.
Orthophoria – Implies as perfect ocular alignment without efforts.
Strabismus consists of two subgroups.
1.Hetrotropia – this is a manifest squint.
Esotropia – deviation of eye  towards inside.
Exotropia -- deviation of eye  towardstowards outside.
Hypertropia-- deviation of eye   towards upside.
2.Hetrophoria—this is a latent ocular deviation. Eye alignment is maintained with fusional effort.
Esophoria – inward deviation of eye when fusion is disrupted.
Exophoria-- outward deviation of eye when fusion is disrupted.
Hyperphoria-- upward deviation of eye when fusion is disrupted.
Incyclophoria-- intortional movement of eye when fusion is disrupted.
Excyclophoria-- Extortional movement of eye when fusion is disrupted.

Concomitant Strabismus
Esotropia
Exotropia
Non Comitantant Strabismus ( Paralytic)
Third Nerve Palsy
Forth Nerve Palsy
Sixth Nerve Palsy
Non Comitantant Strabismus ( Restrictive)
Duane’s Retraction Syndrome
Brown Syndrome
Double Elevator Palsy
Infantile Esotropia
A Pattern Deviations
V Pattern Deviations
AV Pattern Management
Dissocited Vertical Deviations(DVD)
Dissocited Horizontal Deviations(DHD)
Restictive Thyroid Myopathy
 
 
How to examine a strabismus patient?
Management Of Eso Deviations
Complications Of Strabismus (Squint) Surgery
 

 

Squint Surgery Video
Lateral Rectus Recession Video

 
Medial Rectus Resection Video

 

 

Classification Of Exotropia (Concomitant)

 

Constant Exotropia

Intermittent Exotropia
1.Congenital Exotropia

2.Sensory Exotropia

3.Consecutive Exotropia

 

 

 

 

1.Basic Intermittent Exotropia.

2.Divergence Excess Type Of Exotropia:

3.Convergence Insufficiency Type Of Exotropia

         
Constant Exotropia
Congenital Exotropia
• Age of onset at birth.
• Large and constant deviation
• Dissociated vertical deviation (DVD) may be present.
• Neurological anomalies my present.

Sensory Exotropia
• Sensory exotropia occurs as a result of unilateral or bilateral serve visual impairment.

Consecutive Exotropia
Exotropia following surgical overcorrection of esotropia called consecutive exotropia.
Treatment
1.Wait atleast for six month if deviation is not much.
2. Surgical treatment according according to deviation if it is significant


Intermittent Exotropia
• Age of onset around 2 years.
• Starts with Exophoria
• Exophoria break down to exotropia under fatigue, bright light or visual in attention or ill health.

Phases of exodeviation and clinical presentation (Calhounz et al )
  1. Exophoria at distance, orthophoria at near. Asymptomatic
  2. Intermittent exotropia for distance, orthophoria/ exophoria at near. Symptomatic for distance.
  3. Exotropia for distance, exophoria or intermittent exotropia at near. Binocular vision for near, suppression scotoma develops for distance.
  4. Exotropia at distance as well as near. Lack of binocularity
Symptoms Intermittent Exotropia
1.Transient Diplopia
2.Asthenopic symptoms like eyestrain, blurring, headache and difficulty with prolonged periods of reading.
3.Micropsia
4.Diplophotophobia :closure of one eye in bright sunlight. Bright sunlight dazzles the retina so that fusion is somehow disrupted, causing the deviation to become manifest. Thus one eye is closed in order to avoid diplopia and confusion
 
Signs of Progression of Intermittent Exotropia
  • Gradual loss of fusional control evidenced by the increasing frequency of the manifest phase of squint
  • Development of Secondary convergence insufficiency
    Increase in size of the basic deviation
  • Development of suppression as indicated by absence of diplopia during manifest phase
  • Decrease of Stereoacuity

 

 

Basic intermittent exotropia: In which angle of deviation is nearly same for distance and near fixation

Divergence excess type of intermittent Exotropia:

The angle of deviation for distance is more than >15 Δ then near. This type of exotropia may be two type.
True Divergence Excess Type of intermittent Exotropia Or Simulated Type of Divergence Excess intermittent.
• When patient is examined after a uniocular patient for more than 60 min. or looking through +3.00D lens, if near deviation is constantly less than distance deviation. Then it is called as true Divergence excess type of exotropia. If near deviation and distance deviation are same then is called as Simulated type of Divergence excess.

Tenacious Proximal Fusion: Distance measurement initially exceeds near, but the near measurement increases after 60min. of occlusion
Proximal Convergence : Distance measurement exceeds near measurement,even after 60min. of occlusion. AC/A ratio is normal

Convergence Insufficiency Type Of Exotropia
The angle of deviation for near is more than >15 Δ then Distance.

 

 
Patch Test - The patch test is used to control the tonic fusional convergence to differentiate pseudo-divergence excess from true divergence excess and to reduce the angle variability. Contrary to the earlier practice of patching one eye for 24 hrs it is now found that patching the eye for 30 min. is sufficient to suspend the tonic fusional convergence and thus reveal the actual amount of deviation (1).
+3.0 D near add test (lens gradient method) - This test has been devised to diagnose the patients of divergence excess type who have true divergence excess due to high AC/A ratio. This test uses the lens gradient method to measure the AC/A ratio. These patients are the ones who will continue to have a distance-near disparity post-operatively, and may require bifocal spectacles after surgery for a consecutive esotropia at near. This test should be resorted to in patients who have a distance deviation greater than near deviation of 10 prism diopters or more after the patch test. After the patch test while still dissociated, re-measure the deviation at near with a +3.0 add. If the exodeviation at near increases by 20 prism diopters or more the diagnosis of high AC/A ratio true divergence excess intermittent exotropia is made.
Far distance measurement - Measuring the deviation by fixating a far object reduces measurement variability and helps uncover the full deviation by reducing near convergence. Combining the patch test and far distance measurement can greatly reduce under-corrections and has improved the overall result. In a prospective randomized trial, 86% of patients who underwent surgery for the largest angle had a satisfactory outcome, compared with 62% who were operated on for the standard 6 meter distance deviation (2).
Management

Non-surgical Treatment

Indication
• In patients with small (<20pd) deviations
• Very young patients in whom surgical overcorrection could lead to amblyopia or loss of bifixation
• In patients who otherwise cannot be taken up for surgery
• Patients with a high AC/A ratio may be responsive to non-surgical methods.
Non-Surgical Management Options Of Intermittent Exotropia

1.Spectacle Correction of Refractive Errors:

Refractive errors myopia, hyperopia. ,anisometropia and astigmatism can impair fusion and promote a manifest deviation. A trial of corrective glasses based on cycloplegic refraction is often warranted (16).
2.Overcorrecting minus lens therapy:
This is particularly useful in patients who have a high AC/A ratio. This therapy is based on the principle that stimulating accommodative convergence can reduce an exodeviation (17).
3.Part time occlusion:
It is a passive anti-suppression technique as opposed to the active techniques involving diplopia awareness This technique has found some use in very young children. Part time patching of the non-deviating eye for four to six hours daily may convert an intermittent exotropia to a phoria. Although the benefit is usually temporary, occlusion can be used to postpone surgical intervention in responsive patients (18). Alternate occlusion may be used in patients with equal fixation preferences. Initially the results are evaluated after 4 months of occlusion. If the angle of deviation is decreased the occlusion should be continued and assessment made every 4 months until no further change occurs. In case there is no improvement for 4 months, it is discontinued.
4.Prismotherapy: can be used to improve fusional control, or as a temporizing measure, either pre or postoperatively Prisms are rarely a long-term solution in patients with intermittent exotropia.

5.Orthoptics: according to Knapp orthoptics should not be used as a substitute for surgery but rather as a supplement. The aim is to make the patient aware of manifest deviation and to improve the patient's control over it (19). Active anti-suppression and diplopia awareness techniques can be used in cases with suppression
 
Timing for Surgery - There is a controversy about the management of children less than 4 years of age because in contrast to infantile esotropia these children have intermittent fusion and excellent stereopsis. Knapp and many other workers advocated early surgical intervention to prevent development of sensory changes that may prove intractable later (3-7). However they do caution that in visually immature children a slight undercorrection should be attempted to prevent occurrence of monofixation syndrome from consecutive esotropia (8). Jampolsky advocates delayed surgery, citing advantages like accurate diagnosis and quantification of the amount of deviation and to avoid consecutive esotropia and development of amblyopia. Although one study reported better outcomes in children who were under the age of 4 years (7), most studies have failed to show that age at time of surgery makes any difference in outcome (9-11). Thus it is now believed that the surgery in this age group is reserved for patients in whom rapid loss of control is documented. In the interim, minus lenses or part time patching may be used as non surgical methods and these patients followed closely for signs of progression (12,13).

 

Type of Surgery

Basic  Types: should be treated with recession lateral rectus- recession lateral rectus in both eyes or unilateral lateral rectus muscle recession/medial rectus muscle resection
Simulated Divergence Excess : should be treated with recession lateral rectus- recession lateral rectus in both eyes or unilateral lateral rectus muscle recession/medial rectus muscle resection
 Divergence excess type should be treated with bilateral lateral rectus muscle recessions.
Convergence  insufficiency type: should be treated with bilateral medial rectus muscle resections
Exo-deviation with one eye is amblyopic: unilateral lateral rectus muscle recession/medial rectus muscle resection
 
Symmetric(Recession lateral rectus- Recession lateral rectus in both eyes) Vs
Asymmetric((Recession lateral rectus – Resection medial rectus in one eye):Symmetric surgery is usually preferred over monocular recession/resection procedures, since a recession/resection procedure may produce lateral incomitance with a significant esotropia to the side of the operated eye. In adults, this incomitance can produce diplopia in side gaze.

 

References

 
1.Kushner BJ: The distance angle to target in surgery for intermittent exotropia. Arch Ophthalmol 1998:116:189-194.
2.Hutchinson AK. Intermittent Exotropia. Ophthalmol Clinics Of North Am. 2001;14:3:399-406.
3.Asbury T. The role of orthoptics in the evaluation and treatment of intermittent exotropia. In: Arruga A. ed.: International strabismus symposium, Basel 1968, S. Karger AG 331.
4.Dunlap EA. Over correction in esotropia surgery. In: Arruga A. ed.: International strabismus symposium, Basel 1968, S. Karger AG 319.
5.Parks MM. Metchell P. Concomitant exodeviation. In: Duane TD ed. Clinical Ophthalmology, Vol. 1.Philadelphia 1988, JB lippin cott Co. p 1.
6.Pratt Johnson JA, Barlow JM & Tilson G. Early surgery for Intermittent exotropia. Am J Ophthalmol. 1977;84:689.
7.Raab EC. Management of Intermittent exotropia : for surgery. Am Orthopt J. 1998;48:25-29.
8.Ing MR, Nishimura J, Okino L: Outcome study of bilateral lateral rectus recession for intermittent exotropia in children. Trans Am Ophthalmol Soc (XCV): 1997:433-452.
9.Richard JM, Parks MM: Intermittent exotropia: Surgical results in different age groups. Ophthalmology. 1983;90:1172-1177.
10.Stoller SH, Simon JW, Liniger LL: Bilateral lateral rectus muscle recession for exotropia: A survival analysis. J Pediatr Ophthalmol Strabismus 1994; 31:89-92.
11.Rosenbaum AL: Exodeviations. In Current Concepts in Pediatric Ophthalmologya and Strabismus, p 41, Ann Arbor MI, University of Michigan 1993.
12.Santiago AR, Ing MR, Kushner BJ, Rosenbaum AL: In Rosenbaum AL, Santiago AP (ed) Clinical Strabismus Management: Principles and Surgical Techniques. W.B. Saunders company, Philadelphia 1999.
14.Wilson ME: Exotropia. Focal Points Clinical Modules for Ophthalmologists XIII:1999:1-14
15Moore S: The prognostic value of lateral gaze measurements in intermittent exotropia. Am Orthop J. 1969;19:69-71.
16.Iacobucci IL, Archer SM, Giles CL: Children with exotropia responsive to spectacle correction of hyperopia. Am J Ophthalmol. 1993;116:79-83.
17.Caltreider M, Jampolsky A: Overcorrecting minus lens therapy for treatment of intermittent exotropia. Ophthalmology 1983;90:1160-1165.
18.Freeman RS, Isenberg SJ: The use of part time occlusion for early onset unilateral exotropia. J Pediatr Ophthalmol Strabismus 1989;26:94-96
19.Knapp P. Divergent deviations. In: Allen JH ed. Strabismic ophthalmic symposium II. St. Louis 1958, Mosby-Year Book 354

 

 

Download Patient Case Sheet Performa In Word Format

 




 

References

 

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Salient Features Of SquintMaster Software

  • Suggests diagnosis and sub type of deviations
  • Important tool for patient counseling
  • Suggests surgical options
  • Creates simulated image of deviations
  • With help of squint simulator and calculator user can calculate surgical dose ( Amount of surgery)
  • AC /A Simulator And Calculator
  • A V Patterns Simulator And Calculator
  • Parks 3 Step Test
  • Knapp's Classification
  • Simulator for ductions,versions and grades of oblique muscles over action
  • Classification and management of Duane's Retraction Syndrome
  • Management of third nerve palsy
  • Management of forth nerve palsy
  • Management of sixth nerve palsy
  • Management of Browns Syndrome
  • Management of double elevator palsy

 

 

 

 

 

 

 

 

 

 

 

 

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