(S. A. Patney: Strabismology Desk Reference, chapter 42, JKA Publications)

NONPARALYTIC INCOMITANT RESTRICTIVE STRABISMUS:
ADHERENCE SYNDROME & GRAVES OPHTHALMOPATHY

The term adherence syndrome has been used in two different contexts as explained below under the heading of definition.

History

1. Johnson¹ described adherence syndrome with pseudoparalysis of the lateral rectus or superior rectus muscle in 1950.
2. Parks² termed this postoperative condition as adherence syndrome in 1972.

Definition

1. Johnson¹ used the term adherence syndrome to describe a condition in which there are adhesions between either of the two pairs of extraocular muscles detailed below:

1. The lateral rectus and inferior oblique muscles, leading to a clinical picture of pseudopalsy of the lateral rectus.
2. The superior rectus and the superior oblique muscles, giving rise to pseudopalsy of superior rectus.

2. Parks² used the term the term adherence syndrome for a condition that occurs after inferior oblique myectomy. There is proliferation of fibrofatty tissue and adhesion of the proximal stump of the myectomized inferior oblique to the tenon’s membrane or some other structure. There is hypotropia as a result with limitation of elevation.

Prevalence

1. The condition described by Johnson is quite rare³ although he described several variations of adherence syndrome¹.
2. Adherence syndrome reported by Parks² was seen relatively commonly in the past (according my personal experience during more than 4 decades). However, it is seen infrequently now and this is more than likely due to improved surgical techniques and skills.

Etiology

1. Johnson’s adherence syndrome could be due to one of the following two conditions:

1. Congenital anomalies of the muscle fasciae
2. Surgery involving either of the muscles named can cause severe scarring and adhesions. Noorden describes a case³ in which surgery on lateral rectus resulted in severe scar formation and adhesions between the lateral rectus and the IO muscles.

2. Parks’s adherence syndrome is always due to surgery on inferior oblique. There is a possibility that the orbital septum may be injured during the inferior oblique (IO) myectomy leading to the proliferation of fibrofatty tissue and adhesions.

Symptomatology and clinical picture

1. Patients suffering from Johnson’s adherence syndrome present a clinical picture of :

1. Lateral rectus palsy and have esotropia and a restriction of abduction of the affected eye. When the lateral rectus is detached from the sclera and the eye is forced into abduction there is resistance because of the adhesions.
2. Superior rectus palsy and have hypotropia of the affected eye with a limitation of elevation especially in abduction. When the superior rectus is detached from the sclera, there is resistance to elevation of the eye on forced duction (elevation) test.

The treatment of these conditions is surgical.

1. For the adherence syndrome described by Johnson he advises lysis of the adhesions as follows:

1. For the lateral rectus adherence syndrome, the muscle is detached from its insertion and the globe is forcibly rotated medially to break the anomalous attachments. The lateral rectus is then reattached and forced duction test repeated to make sure of free abduction.
2. For the superior rectus adherence syndrome it is detached from its insertion on the sclera and the eyeball rotated inferiorly with force to break the unwanted attachments. The forced duction test is repeated and if the elevation is now free the superior rectus is reattached to its insertion.

2. For the Parks’s adherence syndrome also surgery is required to remove the excess fibrofatty tissue and severe the adhesions.

Graves’ disease is also known as Parry’s or Basedow’s disease. It consists of a triad of symptom complexes: Hyperthyroidism with diffuse goiter, ophthalmopathy and dermopathy. The three components of the triad are liable to run their independent courses.

During the last several years the condition of Graves’ ophthalmopathy has gained a lot of importance because of certain special features. If these features are not recognized and correct diagnosis made the management is not likely to succeed.

Graves’ ophthalmopathy is a component of the multiorgan autoimmune disease that may give rise to the following:

1. Lid retraction
2. Proptosis
3. Lid and periorbital edema
4. Swelling and enlargement of extraocular muscles leading to limitation of ocular motility, especially elevation
5. Optic neuropathy
6. Sometimes a rise of intraocular pressure (secondary)

History

1. Quoting Rolleston from his book Gorman⁴ states that the association of eye disease with goiter was known in the 12^th century.
2. Parry described the triad of hyperthyroidism, diffuse nodular goiter and ophthalmopathy⁵ in his treatise published in 1825, after his death.
3. Graves in 1835 and von Basedow in 1840 noted the same association.
4. Shortly afterwards Graves name was given to the symptom complex.

Graves’ ophthalmopathy has been described by various names because of our lack of understanding of the nature of relationship between the dysfunction of thyroid gland and the associated oculomyopathy.

1. Exophthalmic ophthalmoplegia
2. Endocrine ophthalmopathy
3. Exophthalmic goiter
4. Dysthyroid eye disease
5. Endocrine orbitopathy
6. Endocrine myopathy
7. Infilterative ophthalmopathy
8. Dysthyroid oculomyositis

Prevalence

• Graves’ oculopathy is more common in females⁶.
• It is rare in children. The incidence of thyrotoxicosis in children is hardly 5% and the most common age of diagnosis is 10-15 years
• It occurs most commonly in middle age⁶.
• A retrospective study from 1976 to 1990 by Batley et al⁷ recorded an incidence of 86% in females in cases of Graves’ disease and oculomotor anomalies. In females the incidence was 16 per 100000 and in males 3 per 100000. 90% of these cases had hyperthyroidism.

Hollingsworth et al described 6 families with Graves’ disease¹¹. I all these families the mode of transmission seemed to be autosomal dominant with a predilection for females. There was a mother to daughter linkage in several generations.

Some specific subtypes of human leukocytic antigen (HLA) from chromosome 6 are increased in the patients with Graves’ disease. For the sequence of events in these changes see the etiology below.

The exact cause is not known but it is an autoimmune thyroid disease. Like myasthenia gravis, Graves’ disease is also mediated by autoimmune bodies to membrane receptors. Both the diseases have certain immunogenic features in common.

As already mentioned under the heading of genetic transmission, some specific subtypes of human leukocytic antigen (HLA) from chromosome 6 are increased in the patients suffering from Graves’ disease. The suppressor T lymphocytes become genetically abnormal.

The sequence of events leading to a full fledged picture of Graves’ ophthalmopathy as described^{11, 12} is as follows:

Genetically abnormal suppressor T lymphocytes fail to abort the formation and proliferation of abnormal plasma cells è production of autoantibodies è coating of target somatic cell, in this case extraocular muscle fibers, with autoimmune complexes plasma cell mediated release of muchopolysaccharides ç inflammation & damage ç (sequence of events continued) è collagen formation è hypertrophy of the extraocular muscles è congestion of orbital tissues & strabismus è restriction of ocular motility (typical of Graves’ oculomyopathy) and other complications of Graves’ disease.

Symptomatology

• Patients with Graves’ disease often give history of previous undiagnosed and untreated episodes of hyperthyroidism⁸.
• A family history of myasthenia gravis may be present in cases of Graves’ disease and vice versa⁹.
• Thyroid oculopathy may be associated with hyperthyroidism, euthyroidism or even hypothyroidism⁶.
• It is also common in the patients who have undergone thyroidectomy⁸.
• It is important to look for signs of myasthenia gravis in all cases of Graves’ disease, as there is general agreement about an association between the two conditions. Both disorders are immunogenic in nature. About 5% cases of patients having Graves’ disease have been reported to develop hyperthyroidism¹⁰. However, only about 0.2% of patients with thyrotoxicosis develop myasthenia gravis¹⁰. This is supposed to be due to the common immunogenic features shared by both these diseases (see etiology).
• Symptoms:    

1. Pain and a pulling sensation during the period of inflammation and swelling of muscles.
2. As the swelling subsides the pain disappears.
3. Diplopia is a more common symptom. It is a result of incomitant-restrictive strabismus caused by muscle fibrosis.
4. In longstanding cases the diplopia can be replaced by suppression and even amblyopia.

• Patients suffering from Graves’ disease may or may not complain of symptoms like diplopia due to
• Typical appearance of a case of Graves’ disease during the first 1-2 years is due to the inflammation and congestion of the extraocular muscles and the other orbital contents. They are enumerated below:

1. Edema of the eye lids may be present
2. Periorbital edema is often seen, especially in older patients.
3. Exophthalmos with upper lid retraction leading to a staring look may be present. The lid retraction may be due to an increased effort at elevation of the eye against the passive resistance of the fibrotic inferior rectus.
4. Proptosis is there in some cases. It is due to the increase in the volume of the orbital contents due to congestion, inflammation and swelling
5. Conjunctival congestion, generalized or else local at the insertion-sites of the extraocular muscles
6. Conjunctival chemosis
7. Sometimes there is a lid lag present (von Graefe’s sign).
8. Other signs sometimes seen are convergence weakness, decreased frequency of the blink reflex, a staring look, inability to hold fixation in lateral gaze.
9. Sometimes there is fine tremor on gentle eyelid closure.

• After a period of 1-2 years the inflammation is replaced by fibrosis. The result is a restriction of ocular motility due to fibrotic changes in the extraocular muscles and infiltration of orbital tissues with mucopolysaccharide ground substance.
• Occasionally the stage of inflammation is either bypassed or is very short lived and the patient presents with a restrictive strabismus. In such cases the diagnosis may be missed especially if there are no obvious signs or positive tests of thyroid disease.
• Sometimes the main presenting symptom is exophthalmos with or without diplopia.
• The diplopia is usually gradual in onset. It is a result of varying degree of fibrosis and swelling of various muscles leading to incomitant strabismus. It is usually horizontal as well as vertical because of the involvement of both groups of muscles.
• The first signs may be a periorbital edema and restriction of elevation.
• The strabismus is not uncommonly of mixed type with horizontal and vertical deviations present simultaneously. Sometimes cyclodeviation is added to the others because of the fibrosis and tightness of the vertical muscles.

• As mentioned above the inferior rectus is the most commonly involved muscle and often the most severely affected one also. I wonder if it may be due to its close proximity to the inferior orbital septum. The resulting deviation is a hypotropia with a limitation of elevation with a positive forced duction test for inferior rectus.

• Ocular Motility: The various anomalies of ocular movements in order of the frequency of their occurrence are:

1. Restriction of elevation due to involvement of inferior rectus
2. Restriction of abduction due to the effect on medial rectus
3. Limited depression and abduction due to fibrosis of superior rectus and medial rectus.
4. The least often involved muscle is the lateral rectus, leading to an adduction defect.

• Forced duction test is positive for muscles showing dysfunction (restriction of their action). It must be performed in every case, as it is diagnostic of presence of fibrosis in the muscles.
• There is a resistance in the orbit to retropulsion of the globe. That is to say when the eyeball is pushed backwards into the orbit there is an increased passive resistance.
• The extraocular muscles are the most commonly affected tissue in Graves’ oculopathy (orbitopathy). The range and degree of the extraocular muscle involvement varies from case to case. It can be mild swelling of a few muscles to severe swelling and enlargement leading to fibrosis of multiple or all the muscles.

• Course: Usually the onset of diplopia is gradual. It is frequently related to the onset of exophthalmos. Occasionally mild periorbital edema with limited elevation may be the first sign. The deviation can reverse^{33, 34} usually postoperatively but spontaneously also. The latter may be due to the involvement of the yoke muscle or improvement of the originally affected muscle³².
• The signs and symptoms of Graves’ oculopathy/orbitopathy are of many types and various combinations of them present a formidable range. Several efforts have been made to classify them^{13, 14, 15} but only one of these¹⁴ is widely in use. It is given below:

Note: Every case does not pass through all these stages and then not in that order. In some cases strabismus and motility problem come earlier and others get the soft tissue changes, proptosis and the typical lid signs of Graves’ ophthalmopathy before they get the extraocular muscle problems. However, the optic nerve damage and the corneal complications are not usual before ocular motility problems.

• Atypical and difficult to diagnose cases

1. Defects of ocular motility may be the only features in some cases. All other diagnostic features may be lacking.
2. Thyroid functions may be shown to be normal on blood chemistry tests.
3. This basically bilateral condition may present as unilateral.
4. Paresis of a muscle, e.g., lateral rectus and restricted ocular motility may be present simultaneously. The former is supposed to be due to pressure on the nerve supplying the muscle. This is because of an increase in the volume of orbital contents in the posterior part of the cone. The restricted motility is due to infiltration and fibrosis of the extraocular muscles (EOM).

1. There may be limitation of elevation in one eye and the other eye may appear to be normal, but on careful examination a mild restriction may be present in another direction.
2. Graves disease should always be suspected in every case having the triad of signs as detailed below:

• Acquired incomitant strabismus with restricted elevation, unilateral or bilateral with or without restriction of other movements
• Positive forced duction test
• Signs of ocular palsy absent

1. Resistance, even mild to retropulsion of the globe

1. Examination of a case of Graves’ oculo-orbitopathy

1. Ophthalmological examination:

1. Visual acuity is affected if there is a corneal haze due to exposure of the cornea consequent upon the presence of exophthalmos/proptosis and /or pathology in the optic nerve due to a pressure on it.
2. Other findings, like those of the eyelids and conjunctiva etc. have already been described.
3. Proptosis/exophthalmos
4. Exposure keratitis
5. Nonparalytic-incomitant-restrictive Strabismus
6. Increase in the intraocular pressure on attempted elevation because of the pressure exerted by the fibrotic inferior rectus
7. Optic atrophy because of the pressure on the nerve itself and its blood supply.

2. Orthoptic (ocular motility) examination:

1. Cover test reveals a nonparalytic-incomitant-restrictive strabismus
2. Ocular movements are restricted in various directions depending upon the muscles involved in fibrosis, most common being a limited elevation leading to hypotropia.
3. Measurement of angle of deviation in all the cardinal directions of gaze should be carried out, fixing each eye. It will confirm the incomitant nature of the deviation and the diagnosis made on cover test and ocular motility examination.

The measurement of angle can be conducted on a major amblyoscope or with prisms (prism bars).

It will also be useful for judging the future progress of the disorder.

4. Hess chart will do the same as the measurement of the deviation in cardinal directions of gaze.
5. Diplopia test is done for near and distance and a chart is made in the 9 directions of gaze.
6. Field of binocular single vision (BSV) is recorded for future reference to judge the progress and/or the effect of treatment.
7. Moorits and associates have suggested a method of charting the eye movements¹⁶ whereby a modified perimeter is used to measure them in the various cardinal directions of gaze.

3. Laboratory tests:

1. Forced duction test (FDT, qualitative) and quantitative forced duction test (QFDT): The simple qualitative FDT (see page 663) can be done in the clinic but for the QFDT it is better to use the operation room. The former can be done under local anesthesia except in young children and the later under general anesthesia in children and local/general anesthesia in adults and older children.

2. Blood chemistry: Positive results for the presence of thyroid disease are not necessary for making a diagnosis of Graves oculomyopathy. However, if they are positive that helps. As mentioned already this disorder may be present with normal, hypo or hyperthyroid function.

If several of the typical clinical signs of thyroid oculopathy, as enumerated earlier and some of them repeated below, are present, a clinical diagnosis of Graves’ ophthalmopathy can be made even in the absence of definite thyroid disease as indicated by the presence of normal blood chemistry:

Proptosis, exposure keratitis, lid retraction, lid lag on depression, periorbital edema, restricted ocular motility particularly in elevation, adult onset-nonparalytic-incomitant-restrictive strabismus, positive forced duction test for all or most movements, especially elevation, optic nerve ischemia-atrophy and swollen/enlarged muscle bellies with sparing of the tendons on CT scan/MRI.

3. CT scan (computed tomography) of the orbits shows the swollen and enlarged extraocular muscles. CT scan shows the muscles better (sensitivity >85%) than does the MRI (sensitivity 61%)¹⁷. However, it should be a high resolution CT scan. The swollen muscles stand out clearly against the translucent orbital fat.

There is an increase in the total and individual muscle volume¹⁸ and the degree of severity of the disease is directly proportional to the degree of increase in the mass of the orbital contents.

4. MRI (magnetic resonance imaging) also shows the enlarged muscles.
5. Ultrasonography of the orbit: The positive findings on standard echography are mainly due to the presence of edema and therefore of highly reflective edema fluid and inflammatory cells in the swollen muscles¹⁹.

1. Hypertrophied extraocular muscles (B-scan)
2. Accentuated orbital walls (B-scan)
3. High acoustic reflectivity of the extraocular muscles (EOMs) on A-scan
4. Increased reflectivity and heterogeneity of the EOMs
5. Solid thickening of the nerve sheath of the optic nerve
6. Swelling of the lacrymal glands

6. Electromyography (EMG) of EOM indicates the presence of a myopathic lesion rather than a neurogenic etiology^{21, 22} as is the case with skeletal muscles in cases of thyrotoxic myopathy.

The main feature is a decrease in the amplitude of action potential. There is no effect on the number of motor units.

As has already been mentioned myasthenia gravis is more frequently found in cases of Graves’ disease than otherwise. If it is present in a certain patient suffering from Graves’ myopathy the EMG recordings will show a fatigue of motor units. After an injection of tensilon (edrophonium) or even after simple rest a recovery of the activity in motor units is observed. This result should make one suspect coexistence of myasthenia gravis.

7. Recordings of the saccadic velocity do not show evidence of muscle paresis except in cases with congestive type of Graves’ ophthalmopathy. This finding also points to the restrictive nature of the muscle dysfunction²². If however, a paretic element is added to the restrictive, the peak velocity of the horizontal saccades will decrease. The paresis in the cases of Graves’ oculopathy is primarily due to severe congestion and therefore is more likely to be found in the congestive phase of the disease. When congestion is relieved as by orbital decompression, the peak velocity increases.
8. Infrared coulography^{13, 25} also shows reduced peak velocity on horizontal saccades in more severe cases with increasing congestion in the orbits. It improves after orbital decompression.
9. Assessment of active force generation (see page 661) in the EOMs also shows no evidence of palsy²².

Pathology

• The bellies of the extraocular muscles are the primary sites of the disease.
• The sheaths of the tendons at the insertion are not usually affected.
• The inflammation of the muscle leads to the following as indicated in the etiology earlier:

1. Proliferation of fibroblasts
2. Secretion of mucopolysaccharide
3. Production of collagen
4. Striated cells of the extraocular muscles (EOM) degenerate with the collection of collagen
5. Fibrosis of EOM takes place.
6. Swollen and fibrosed muscles make the main mass of the increased soft tissue contents of the orbit.
7. The fibrosis of EOM leads to the defective ocular motility.
8. The increase in the volume of the soft tissue contents of the orbits leads to proptosis.

Differential diagnosis of graves’ ophthalmopathy (see table 42-1, below)

Management

1. Conservative (non-surgical)
2. Surgical

1. Conservative (non-surgical) management:

1. Medical treatment
2. Radiation therapy
3. Prismotherapy
4. Denervation
5. Plasmapheresis

1. Treatment of thyrotoxicosis if indicated. The endocrine imbalance must be corrected before considering surgery. However, the former does not affect the strabismus or the restricted motility^{32, 33, 35}.
2. Artificial tears and decongestant drops for exposure keratitis and conjunctival congestion and chemosis
3. Corticosteroids for acute congestive stage of the disease. Although they can not improve the fibrosis and the effects thereof, they do reduce orbital congestion and proptosis. The visual acuity may improve thereby as the pressure on the optic nerves is also reduced. They do not affect the ophthalmopathy.

A word of caution is in order here. The corticosteroids should not be used except as a short-term therapy in the acute congestive phase. Long-term use may lead to the well-known side effects.

4. Immunosuppressive drugs have been tried for the treatment of Graves’ disease, namely Cyclophosphamide, Azathioprine²⁸ and Cyclosporine²⁹. The first two alone or together have been found effective in most patients during the congestive stage, in about 50% they improved the muscles and in a few patients the proptosis was reduced. Cyclosporine in combination with corticosteroids was effective in reducing extraocular muscles’ abnormally large size and proptosis along with the improvement of visual acuity.

1. If the surgery for strabismus is contraindicated and there is bothersome diplopia.
2. If there is diplopia and the surgery is delayed due to some reason prisms can be used during the waiting period.

• The main indication of prisms in the patients of Graves’ ophthalmopathy is bothersome diplopia.
• Conventional prisms allow clearer vision. Fresnel prisms though lighter and thinner, usually become yellowish after some time. The visual acuity is not so good through Fresnel prisms³¹.
• Bifocal prisms can be prescribed for primary position and depression. Because of the inferior rectus being the most common muscle to be severely fibrosed and tight, the superior rectus action is defective and usually asymmetrical. There is hypotropia of the worse affected eye. The deviation is maximum in elevation, lesser in primary position and least in depression, hence the need for bifocal prisms.
• For smaller angles the deviation present in primary position is corrected. If there is a refractive error needing correction the prism power can be ground into the lenses.
• For moderate degree of strabismus Fresnel prisms can be given to get rid of diplopia in primary position.
• Prisms do not work for large angles.
• The strabismus found in Graves’ disease is incomitant (varying in various directions of gaze and fixing either eye). Its degree can also change from time to time. Power of the prisms may therefore have to be changed repeatedly.
• Even after surgery the deviation is not corrected in all directions because of the incomitant nature of the strabismus. In such cases surgery can be carried out and postoperative residual angle can be corrected in primary position and depression (for reading). The advantage of surgery is that only a small prism will be needed in the postoperative period.
• Even after readjustable surgery the prisms may be required.

3. Denervation: Botulinum toxin has been used with success in acute stages of Graves’ disease. Fusion can be restored and if the basic condition is controlled the benefit may be permanent. However, once the fibrosis of EOM has set in, any improvement is usually temporary and the eyes go back to the pre-Botulinum injection stage after its effect wears off.
4. Occlusion has to be resorted to when the diplopia is bothersome, it can not be corrected with prisms and surgery can not be carried out due to some reason. Usually it is temporary and is used during the waiting period.
5. Plasmapheresis is another mode of therapy being tried in acute stages. It acts by getting rid of autoantibodies and immune complexes.

2. Surgical treatment

When to operate

1. When the basic condition is well controlled with medicines and inflammation has subsided.
2. The angle of strabismus and ocular motility status is stationary for at least 6 months³⁵
3. Patient does not want to wear prisms, especially high powered ones
4. There is bothersome diplopia not relieved by prisms (either too big or too incomitant)

What to do

• If orbital decompression is contemplated it should be done before strabismus surgery^{*, 38}.
• If there is a large esotropia along with a small vertical deviation, only the horizontal deviation may be corrected to avoid an overcorrection of the vertical tropia. The latter can be managed, if necessary with small prism or if the fusion is present even that may not be required³².

• The reverse of the above also holds true. If there is a large vertical deviation and a small horizontal one, the vertical is better corrected by surgery and the horizontal, if not controlled by the force of fusion, can be corrected by prisms to achieve fusion and get rid of diplopia.

• If elevation is restricted and there is a hypotropia in primary position a recession of the fibrosed (diagnosed by forced duction test) inferior rectus is the usual preference. Special care should be taken during the dissection of the muscle to free it from the Longwood’s ligament to prevent a lower lid retraction. However, it is not easy in these cases because of the tightness of the inferior rectus. After recessing the inferior rectus the conjunctiva has to be recessed too for a good result.

• If there is esotropia due to fibrosis of medial rectus and restriction of the action of lateral rectus, a large recession of medial rectus is usually effective. This procedure is also more effective if combined with recession of conjunctiva in longstanding cases where conjunctiva and tenon’s membrane have become shrunken and nonelastic.

• For the fibrosis of other extraocular muscles similar procedures are quite effective.

• If there is significant hypotropia as well as esotropia, medial rectus may well be involved in fibrosis but there is a possibility that the convergent deviation is due to the fibrosis of the inferior rectus and not due to that of medial rectus. To decide if such is the case, forced duction test should be performed after disinserting the inferior rectus for recession/tenotomy. If the test is now negative and abduction (as well as elevation) is free, there is no need to tackle the medial rectus.

• If the muscle (inferior rectus, medial rectus or any other) is severely fibrosed along with the tenon’s membrane and the conjunctiva due to the severity of the disease and the long duration, a large recession may not be sufficient. In such cases the recession is combined with a conjunctival recession. Alternatively a free tenotomy has to be done occasionally along with a conjunctival recession. However, this may be followed by a consecutive strabismus, e.g., exotropia and convergence deficiency after medial rectus tenotomy.

• Sometimes there is fibrosis of the vertical recti, i.e., the superior rectus and the inferior rectus. However, this is mostly discovered after the inferior rectus surgery, even after the tying of adjustable sutures if they have been used. There is postoperative hypertropia (overcorrection). It is important to rule out overcorrection due to excessive weakening of the inferior rectus. CT scan, which shows the affected muscles, can do this.

Complications

1. Postoperative severe inflammation
2. Lower lid retraction
3. Late slippage of the tendon of inferior rectus
4. A pattern exotropia after large bilateral recessions of inferior recti
5. Undercorrections and overcorrections

1. Reduced visual acuity
2. Severe conjunctival congestion, chemosis and echymoses,
3. Corneal opacification, vascularization and thinning (almost melting)
4. Marked proptosis
5. Gross overcorrection leading to large hypertropia
6. Gross limitation of downgaze: the eye could not be moved beyond midline

2. Lower lid retraction may occur after inferior rectus recession of more than 3 mm despite a thorough dissection, separation of all check ligaments and severance of attachments of the muscle to the lower lid retractors. It is more liable to occur because the amount of recession in these cases is really large.

To treat a lower lid retraction lateral tarsorrhaphy⁴¹ or stored (eye bank) sclera is used as a spacer at the lower end of the tarsal plate^{40, 41}.

3. Late slippage of the inferior rectus muscle from its recessed position has been reported after adjustable suture surgery using absorbable sutures. The eye shows progressively increasing hypertropia in the weeks following the recession. To prevent it either adjustable suture technique is not used or nonabsorbable suture material is used⁴².
4. A pattern exotropia (XT)⁴¹ has been reported after bilateral inferior rectus recession. The inferior rectus, besides being a depressor, is an adductor also and when it is recessed on both sides the adduction becomes weak causing an A pattern XT. The treatment consists of a simple medial displacement or transposition of the insertions of both inferior recti by about ½ tendon breadth. Alternatively, if the horizontal recti are to be operated on, the medial recti can be transposed upwards or lateral recti downwards.
5. Undercorrections and overcorrections are not really complications but they do cause postoperative problems to be dealt with. These problems have to be corrected if there is diplopia in primary position and downgaze. The underacting muscles may have to be advanced (if not already tight) and the overacting ones recessed.

As regards as the relief of symptoms is concerned the results of surgery are fairly gratifying, both for the patient and the surgeon³⁵, provided the disease has first been adequately treated medically and condition stabilized. However, the picture is liable to change and repeated surgery may be required in future even though the condition has been satisfactorily treated by one or more operations.

Special points

• The patient must be warned about the nature of the condition and the possibility of recurrences and repeated surgery.
• Forced duction test is a useful tool to assess the degree of fibrosis. It should be done preoperatively, intraoperatively (both before and immediately after the operation) and postoperatively if indicated.

• Before deciding on surgery one must make sure that the endocrine balance has been restored, the inflammation has subsided and the angle of deviation and ocular motility are stable and that there is no further change in signs and symptoms for at least 6 months. If this precaution is not taken the treatment may fail or give rise to unforeseen complications.
• The inferior rectus may be so tight and fibrosed that during dissection it is difficult to get a hook under its tendon. Utmost care should be exercised to avoid a perforation of the sclera.
• The surgeon should be content with achieving alignment in primary position and depression (walking, going up or down the stairs, reading, writing or working position). One should not try to restore full motility in all the directions, as it is not possible without causing complications like restricted motility in other directions.

1. Noorden³⁷ has aptly summed up the main points in the definition of Graves’ ophthalmopathy as " It is a part of a multiorgan autoimmune inflammatory disease that may cause periorbital edema, enlargement (and later fibrosis) of the EOM, proptosis, lid retraction, optic neuropathy and (sometimes) secondary rise of intraocular pressure".
2. A case with the following features should be diagnosed as thyroid ophthalmopathy unless proved otherwise³⁶:

• An isolated acquired hypotropia with
• Positive forced duction test on the inferior rectus of the affected eye
• The eye can not be elevated from its hypotropic position

1. Symptoms are many and varied. They present a wide spectrum with various degrees and combinations of signs and symptoms. There is inflammation, swelling and enlargement of affected ECM followed by fibrosis and contracture.
2. The most common muscles to be affected by fibrosis (after swelling, inflammation and enlargement) are inferior rectus, medial rectus, superior rectus and lateral rectus in that order.
3. Status of thyroid may be anything from hyperthyroid, euthyroid to even hypothyroid.
4. The basic nature of the condition is not well understood but it seems to be an autoimmune disease.
5. CT scan and MRI show up the enlarged affected extraocular muscles.
6. Management mainly consists of controlling the basic thyroid problem, taking care of exposure keratitis and restoring binocular single vision at least in primary position and depression, the two directions most used in daily life. Prisms and/or surgery on the fibrosed EOMs to align the visual axes can control the diplopia.

References

1. Johnson, L.V.: Adherence syndrome: pseudoparalysis of the lateral rectus or superior rectus muscle, Arch. Ophthalmol. 44:870, 1950.
2. Parks, M.M.: The weakening surgical procedures for eliminating overaction of the inferior oblique muscle, Am. J. Ophthalmol. 73:107, 1972.
3. Noorden, G.K. von: Binocular Vision and Ocular motility- Theory and Management of Strabismus, 5^th edition, St. Louis, 1996, Mosby-Year Book, p. 442-443.
4. Gorman, C.A.: Graves’ disease: An overview. In Gorman, C.A., Walter, R.R. and Dyer, J.A., editors: The Eye and Orbit in Thyroid Eye Disease, 1984, New York, Raven Press, p. 1.
5. Metz, H.S.: Clinical Strabismus Management: Principles and Surgical Techniques, editors: Rosenbaum, A.L. and Santiago, A.P., 1998, Philadelphia, PA, W.B. Saunders Company, p.285.
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