Thyroid Associated Ophthalmopathy

Thyroid Associated Ophthalmopathy

Graves' disease is the most common thyroid abnormality associated with thyroid orbitopathy, but other disorders of the thyroid can have similar ocular manifestations. These include Hashimoto's thyroiditis, thyroid carcinoma, primary hyperthyroidism, and neck irradiation.

Of those patients with thyroid orbitopathy, approximately 80% are clinically hyperthyroid and 20% are clinically euthyroid.

Both hyperthyroid and euthyroid patients can develop clinical signs and symptoms of thyroid orbitopathy. In general, patients with euthyroid Graves' disease tend to have less severe orbitopathy

n the large majority (80%) of patients with hyperthyroid Graves' orbitopathy, eye signs develop within 18 months of the detection of the thyroid disease; usually they develop concurrently.

Etiology:

Also, although antibodies can be isolated from most patients with thyroid orbitopathy, they are not present in all patients, and often there is no correlation between the antibody level and the clinical progression or severity of the eye disease.

Fibroblasts also produce collagen and glycosaminoglycans, which cause edema. These inflammatory changes occur in the interstitial connective tissue of the extraocular muscles. The muscle cells themselves are normal.

PATHOLOGY

The predominant orbital pathology is inflammation of the orbital soft tissues and extraocular muscles. eosinophils and germinal centers with follicles, such as may be found in other noninfectious orbital inflammations, are typically absent in thyroid orbitopathy.27 The earliest change in extraocular muscles appears to be inflammation of the endomysial connective tissues, which stimulates endomysial fibroblasts to produce first hyaluronic acid and then collagen. In the acute stage there is inflammation, edema, and deposition of glycosaminoglycans. Eventually there is tethering of orbital tissues due to fibroblast proliferation. The tendinous insertions onto the globe and the optic nerve meninges generally show no inflammation at all.

The increased orbital volume is due to inflammation in the connective tissue surrounding the extraocular muscles, and accumulation of glycosaminoglycans in the connective tissues of the extraocular muscles and the orbital fat compartments

CLINICAL MANIFESTATIONS:

1. soft tissue involvement:

• Periorbital and lid swelling
• Conjunctival hyperaemia
• Chemosis.
• Superior limbic keratoconjunctivitis.

2. Lid retraction.
3. Proptosis.
4. Restrictive myopathy. ( IR then MR then Sup. levator complex then LR)= counter clock wise.
5. Optic neuropathy.(by CT scan, apical crowding is the most sensitive indicator for the presence of optic neuropathy)

Strange Facts

1. Women 4:1 Men
2. Men and >50 yrs worse prognosis
3. 18% of pts with normal vision have optic neuropathy
4. 35% have RAPD
5. Thyroid orbitopathy is the single most common cause of bilateral or unilateral proptosis. Typically, the proptosis in thyroid orbitopathy is bilateral, but it may be asymmetric.
6. Thyroid orbitopathy results in an axial proptosis; displacement of the globe in any other direction is suggestive of another diagnosis.

Tests (not usually mentioned)

1. FM-100 (Farnsworth-Munsell 100-hue test is a sensitive indicator of optic nerve dysfunction, but pseudoisochromatic screening procedures (e.g.,Ishihara plates) rarely identify an acquired color defect unless optic neuropathy is severe.)
2. VEP (for optic neuropathy) pattern reversal VEP.
3. U/S better than CT to determine if tendon affected
4. visual fields (Characteristically, a central scotoma or an inferior altitudinal defect is seen in cases of compressive optic neuropathy. Other visual field defects include an enlarged blind spot, paracentral scotoma, nerve fiber bundle defect, or generalized constriction.).

Signs:

1. Von Graefe's sign is the lag of the downward movement of the upper eyelid on slow downgaze.
2. Griffith's lower lid lag on up gaze.
3. Stellwag's incomplete and infrequent blinking.
4. Kocher's spasmodic retraction of the upper lid during fixation.
5. Rosenbach's tremor of the gently closed lids.
6. Gifford's difficult eversion of the upper lid.
7. Grove's resistance to downward pull of the upper eyelid. Grove's sign is positive when a significant amount of resistance is felt and indicates that the levator muscle is probably involved.

Treatment

Congestive Orbitopathy

1. Mild

1. Lubricants
2. Elevate bed
3. Stop smoking

7. Moderate/Severe
   1. Oral prednisone 60-120mg/day
      1. Effective in 60%
      2. Does not treat fibrosis
      3. Aim protect cornea, shrink orbital tissue and reduce periorbital edema.
      4. Frequently difficult to taper off
      5. Long term use with little benefit not advocated

2. Orbital irradiation
   1. Effective in 60-70%
   2. Relapse 25%
   3. 2000 cGy in 10 doses over 2 weeks
   4. Takes 2-3 weeks for response
   5. SE: cataracts, radiation retinopathy

3. Immunosuppressive therapy:

Compressive Optic Neuropathy

1. High dose steroids (prednisone)

4. Dose 60-120mg per day
5. Wait 2 to 3 weeks for effect
6. 50% relapse when withdrawn

Radiation

Problem of timing

Probably more effective than steroids

Never use when progressive neuropathy in evolution

Role probably is in cases with repeated steroid taper results in slow return of neuropathy or contraindication to steroids develop

Decompression

Indicated when steroids failed or contraindicated

2 or 3 wall decompression? 3 probably better