Botulinum A toxin injection for restrictive myopathy of thyroid-related orbitopathy: effects on intraocular pressure

Intraocular Pressure and Glaucoma in Thyroid Eye Disease

PURPOSE

Current literature lacks a summary of knowledge on intraocular pressure (IOP) elevation and glaucoma in thyroid eye disease (TED). This review aims to augment existing literature by providing such a summary. It qualitatively evaluates current knowledge on the pathogenesis, prevalence, and management of concomitant ocular hypertension or glaucoma in TED patients.

METHODS

In this narrative review, relevant publications were identified through a computerized database search. Search results were screened for relevance. Correspondence, Editorials, and Letters to the Editors were excluded. References cited within the identified articles were used to further augment the search. Information extracted for qualitative analysis included epidemiologic data, methods of IOP assessment, management protocols, and response to treatment.

RESULTS

Studies in current literature are relatively heterogenous, differing in country of origin, TED cohort sizes, and IOP measurement techniques. Further studies are required to elucidate the true epidemiologic relationship between TED and ocular hypertension or glaucoma. Proposed models of IOP elevation include elevation of episcleral venous pressure, mucopolysaccharide deposition within the trabecular meshwork, restrictive myopathy, steroid-induced glaucoma, and secondary glaucoma. IOP-reducing effects of TED treatment options are discussed.

CONCLUSIONS

While raised IOP in TED is a common phenomenon, the diagnosis of glaucoma in TED requires a high index of suspicion before any intervention.

Management of Thyroid Eye Disease-Related Strabismus

Purpose:

To review various treatment methods in thyroid eye disease (TED) related strabismus.

Methods:

We searched in PubMed and Google Scholar and Ovid MEDLINE for keywords including TED-related strabismus, strabismus in thyroid-associated ophthalmopathy, Graves^' ophthalmopathy related strabismus or squint, and restrictive strabismus. Two expert strabismus specialists selected and evaluated the English articles that were related to our paper and had been published since 2000. Some articles were added based upon the references of the initial articles.

Results:

One hundred fifteen articles were found, 98 of which were mostly related to the topic of this review. Management of TED-related strabismus was reviewed and categorized in non-surgical and surgical. Botulinum toxin A (BTA) is a useful non-surgical management of strabismus in an active TED and residual deviation after strabismus surgery. Postoperative under-correction is relatively more common in TED-related esotropia. Lateral rectus resection and BTA are the options to manage the problem. Muscle rectus muscle resection should be performed after maximum recession of restricted muscles. It should be avoided on a restricted or enlarged muscle. Management of TED-related vertical deviation is challenging. In these cases, the surgical treatment selected depends on forced duction test (FDT) (pre and intraoperative), orbital imaging (which muscle is enlarged), and the amount of vertical deviation (in both down-gaze and primary position).

Conclusions:

TED-related strabismus needs careful evaluation and management to achieve optimal outcome. Different surgical and non-surgical options are available for intervention in TED-related strabismus.

Botulinum toxin for treatment of restrictive strabismus

PURPOSE

To study the types of acquired restrictive strabismus treated in a tertiary hospital and the outcome of treatment with botulinum toxin.

METHODS

We performed a 10-year retrospective study of patients with restrictive strabismus aged ≥18 years who were treated with botulinum toxin. Treatment was considered successful if the final vertical deviation was ≤5 PD, horizontal deviation ≤10 PD, with no head turn or diplopia.

RESULTS

We included 27 cases (mean age, 61.9 years). Horizontal strabismus was diagnosed in 11.1%, vertical in 51.9%, and mixed in 37%. Strabismus was secondary to cataract surgery in 6 cases, high myopia in 6, orbital fractures in 5, retinal surgery in 5, Graves ophthalmopathy in 4, and repair of conjunctival injury in 1 case. Diplopia was diagnosed in all patients, head turn in 33.3%. The initial deviation was 14 PD (range, 2-40), the mean number of injections per patient was 1.6 (range, 1-3), and the mean dose was 9.5 IU (range, 2.5-22.5). At the end of follow-up, diplopia was recorded in 59.3%, head turn in 18.5%, surgical treatment in 51.9%, and need for prism glasses in 14.8%. Outcome was successful in 37% of patients (4 high myopia, 3 orbital fractures, 2 post-surgical retinal detachment, and 1 post-cataract surgery). Mean follow-up was 3±1.8 years.

CONCLUSION

Vertical deviation was observed in half of the sample. The most frequent deviation was secondary to cataract surgery and high myopia. Treatment with botulinum toxin was successful in one-third of the patients at the end of follow-up.

Thyroid-associated Ophthalmopathy

Thyroid-associated ophthalmopathy is the most frequent extrathyroidal involvement of Graves’ disease but it sometimes occurs in euthyroid or hypothyroid patients. Thyroid-associated ophthalmopathy is an autoimmune disorder, but its pathogenesis is not completely understood. Autoimmunity against putative antigens shared by the thyroid and the orbit plays a role in the pathogenesis of disease. There is an increased volume of extraocular muscles, orbital connective and adipose tissues. Clinical findings of thyroid-associated ophthalmopathy are soft tissue involvement, eyelid retraction, proptosis, compressive optic neuropathy, and restrictive myopathy. To assess the activity of the ophthalmopathy and response to treatment, clinical activity score, which includes manifestations reflecting inflammatory changes, can be used. Supportive approaches can control symptoms and signs in mild cases. In severe active disease, systemic steroid and/or orbital radiotherapy are the main treatments. In inactive disease with proptosis, orbital decompression can be preferred. Miscellaneous treatments such as immunosuppressive drugs, somatostatin analogs, plasmapheresis, intravenous immunoglobulins and anticytokine therapies have been used in patients who are resistant to conventional treatments. Rehabilitative surgeries are often needed after treatment.

Botulinum toxin injection for restrictive myopathy of thyroid-associated orbitopathy: success rate and predictive factors

PURPOSE

To evaluate the rate of and predictive factors for successful treatment of restrictive myopathy in thyroid-associated orbitopathy (TAO) using botulinum toxin injection.

METHODS

Twenty patients with restrictive myopathy of TAO were enrolled in the study. Abnormal thyroid function test results were not a prerequisite for inclusion. In each extraocular muscle 25 units of botulinum toxinA were injected. The success rate, calculated at 2 years or last follow-up before surgery, was defined as proportion of the cases with esotropia of <10(Δ), vertical deviation of <5(Δ), and no diplopia in primary position and downgaze for at least 1 year. Both univariate analysis and multivariate logistic regressions were performed to identify the factors associated with success.

RESULTS

The procedure was successful in 11 cases (55%): in 8 patients with predominantly esotropia, 1 patient with predominantly hypotropia, and 2 patients of mixed type. Four factors were significantly associated with the success: type of deviation (P = 0.007), lower amounts of hypotropia (P = 0.001) and esotropia (P = 0.05), and lower degree of extorsion (P = 0.01). In the multivariate logistic regression, only lower amount of hypotropia was significantly associated with the success (P = 0.09, OR = 1.36).

CONCLUSIONS

Botulinum toxin injection can be an effective alternative for the treatment of the restrictive myopathy in TAO. The best candidates for injection of the toxin are patients with esotropia, smaller angle of horizontal and vertical deviations, and lower degree of extorsion.

Management plan and delivery of care in Graves' ophthalmopathy patients

Most patients with Graves' orbitopathy have mild disease that requires no or minimal intervention. For the minority of patients with moderate or severe disease, multiple medical and surgical treatments may be required at different stages. It is crucial that such patients are monitored closely and treatments applied with care in the right sequence. Medical treatments should be used as early as possible and only during the active phase of the disease. Rehabilitative surgery is indicated in the inactive phase of the disease and should follow the sequence: surgical decompression followed by eye muscle surgery, followed by lid surgery. Delivery of care in a coordinated fashion that makes use of best available expertise is important and best implemented through a Combined Thyroid Eye clinic.

Thyroid-associated orbitopathy: who and how to treat

Thyroid-associated orbitopathy is the most frequent and troublesome nonthyroidal complication of Graves' disease. It is mandatory to determine whether sight-threatening orbitopathy is present, as this requires prompt and aggressive treatment. Therapies for non-sight-threatening disease range from supportive measures only to medical therapies for active eye disease and surgical rehabilitation for burnt-out disease. Intravenous steroids and orbital radiotherapy are the mainstays of medical therapy. Rehabilitative surgery is frequently a staged process that may involve sequentially: orbital decompression, strabismus surgery, and eyelid procedures. Smoking cessation is recommended at all disease stages. Treatment within a multidisciplinary team consisting of both endocrinologists and ophthalmologists may lead to optimal patient outcomes.

Role of botulinum toxin A in diplopia following orbital decompression

Diplopia following orbital decompression is a common complication in Graves' ophthalmopathy. Strabismus surgery is often required to treat the persistent diplopia. The author presents a successful treatment with botulinum toxin A injection in a case of diplopia following orbital decompression. Treatment with botulinum toxin A in the management of new-onset diplopia following orbital decompression has been suggested in a case that is not amenable to prism treatment and may eliminate strabismus surgery in some cases.

Is gaze-dependent tonometry a useful tool in the differential diagnosis of Graves' ophthalmopathy?

BACKGROUND

A rise in intraocular pressure (IOP) in upgaze is regarded as a diagnostic sign in Graves' ophthalmopathy (GO). However, the question of erroneous IOP measurement due to applanation carried out on the peripheral cornea has never been addressed.

METHODS

In 22 healthy volunteers, as well as in 51 GO patients, applanation tonometry was performed in the primary position of gaze and at 20 degrees of upgaze. In addition, applanation tonometry was repeated using a flexible chin rest to incline the head and produce 20 degrees upgaze. This enabled applanation on the central cornea.

RESULTS

In healthy controls, mean IOP in conventional upgaze showed a significant rise compared to primary position (p < 0.0001). IOP measurements in 20 degrees upgaze/head inclination were significantly lower compared to conventional upgaze tonometry (p < 0.0001) and comparable to mean IOP in primary position (p = 0.7930). Mean IOP in GO patients was also significantly higher in conventional upgaze compared to primary position (p < 0.0001). The upgaze measurements obtained by head inclination were significantly lower than those from conventional upgaze tonometry (p < 0.0001), but showed a statistically significant rise compared to mean IOP in primary position (p < 0.0001). The overlap of IOP readings in upgaze between normal individuals and GO patients was considerable, even in patients with severely impaired ocular motility.

CONCLUSION

In both normal volunteers and patients suffering from GO, a rise in IOP was observed in conventional upgaze tonometry. However, this increase in IOP was partially due to applanation on the peripheral cornea. Measurements in upgaze by head inclination on the central cornea led to a significant lowering of the gaze-dependent IOP change. The discriminating power of the IOP difference between upgaze and primary position to diagnose GO was found to be limited. The broad overlap of IOP between normal individuals and GO patients as detected by conventionally performed upgaze tonometry leads us to conclude that this sign may not be of relevant differential diagnostic value in patients with a clinically undetermined diagnosis.

Increased retinal blood flow in patients with active Graves' ophthalmopathy

PURPOSE

To investigate retinal blood flow by Heidelberg retina flowmeter in patients with active Graves' ophthalmopathy.

MATERIALS AND METHODS

Thirty patients with active Graves' ophthalmopathy in euthyroid state and thirty normal controls were enrolled in this study. All subjects underwent heart rate, systolic and diastolic blood pressure detection, complete ophthalmological examination, Hertel's exophthalmometry, and retinal blood flow analysis by Heidelberg retina flowmeter. Patients additionally underwent automated threshold perimetry and extraocular muscle thickness measurement by A-scan ecography.

RESULTS

A significant statistical difference was found in exophthalmometry (P<0.001), intraocular pressure (P<0.001) and retinal blood flow (P<0.05) between patients and controls. In patients, muscle enlargement was significantly correlated with retinal blood flow (r=0.49, P=0.005) and proptosis (r=0.37, P=0.04). A significant positive correlation (r=0.52, P=0.002) was also found between intraocular pressure and proptosis.

CONCLUSIONS

Active Graves' ophthalmopathy patients present an increased retinal blood flow.

Effect on intraocular pressure of extraocular muscle surgery for thyroid-associated ophthalmopathy

PURPOSE

To study the effect of extraocular muscle surgery on intraocular pressure (IOP) in patients with thyroid-associated ophthalmopathy.

DESIGN

Retrospective, observational case series.

METHODS

The medical records of patients with restrictive myopathy secondary to thyroid-associated ophthalmopathy who underwent strabismus surgery from July 1, 1997 through July 31, 2003 were reviewed and analyzed retrospectively. Seventeen patients met the criteria and were included in this study. All patients were seen at the Thyroid Eye Center at the University of California, San Diego, a university-based tertiary referral center. The main outcome measure was IOP readings obtained before and after surgery in both primary gaze and upgaze.

RESULTS

A statistically significant decrease in IOP in upgaze was noted after extraocular muscle recession. The mean IOP before surgery was 16.6 +/- 3.78 mm Hg in primary gaze and 23.2 +/- 7.27 mm Hg in upgaze. After strabismus surgery, the mean IOP after one month was 15.7 +/- 2.36 mm Hg (P = .215) in primary gaze and 18.9 +/- 2.96 mm Hg in upgaze (P = .001).

CONCLUSIONS

Strabismus surgery resulted in a significant reduction in IOP in the early postoperative period in patients with restrictive myopathy secondary to thyroid-associated ophthalmopathy.

Optic Neuropathy Associated With Botulinum A Toxin in Thyroid-related Orbitopathy

PURPOSE

To report the development of optic neuropathy after botulinum A toxin injection for restrictive myopathy from thyroid-related orbitopathy (TRO).

METHODS

We retrospectively reviewed the records of three patients with TRO who underwent botulinum A toxin injection for restrictive myopathy and subsequently developed optic neuropathy. Development of optic neuropathy was measured by visual acuity, color vision testing, visual field testing, and relative afferent pupillary testing.

RESULTS

At 3 week follow-up after botulinum A toxin injection, three patients were noted to have clinical signs and symptoms of optic neuropathy in the ipsilateral eye following injection of botulinum A toxin for restrictive myopathy. Treatment with oral steroids followed by orbital wall decompression reversed the optic neuropathy.

CONCLUSIONS

To our knowledge, this is the first report of optic neuropathy associated with botulinum A toxin injection in TRO. Clinicians should be aware of this potential vision threatening complication.

Botulinum Toxin in Ophthalmology

Since its introduction into clinical medicine in 1980, botulinum toxin has become a major therapeutic drug with applications valuable to many medical sub-specialties. Its use was spearheaded in ophthalmology where its potential applications have expanded to cover a broad range of visually related disorders. These include dystonic movement disorders, strabismus, nystagmus, headache syndromes such as migraine, lacrimal hypersecretion syndromes, eyelid retraction, spastic entropion, compressive optic neuropathy, and, more recently, periorbital aesthetic uses. Botulinum toxin is a potent neurotoxin that blocks the release of acetylcholine at the neuromuscular junction of cholinergic nerves. When used appropriately it will weaken the force of muscular contraction, or inhibit glandular secretion. Recovery occurs over 3 to 4 months from nerve terminal sprouting and regeneration of inactivated proteins necessary for degranualtion of acetylcholine vesicles. Complications are related to chemodenervation of adjacent muscle groups, injection technique, and immunological mechanisms.

Botulinum toxin: Clinical use

Since its development for the use of blepharospasm and strabismus more than 2.5 decades ago, botulinum neurotoxin (BoNT) has become a versatile drug in various fields of medicine. It is the standard of care in different disorders such as cervical dystonia, hemifacial spasm, focal spasticity, hyperhidrosis, ophthalmological and otolaryngeal disorders. It has also found widespread use in cosmetic applications. Many other indications are currently under investigation, including gastroenterologic and urologic indications, analgesic management and migraine. This paper is an extensive review of the spectrum of BoNT clinical applications.

Thyroid-associated orbitopathy: a clinicopathologic and therapeutic review

PURPOSE OF REVIEW

To review the literature related to thyroid-associated orbitopathy and to emphasize recent developments in its pathophysiology, diagnosis, and therapy. Current therapeutic trends and controversies are discussed.

RECENT FINDINGS

Expression of thyroid stimulating hormone receptor is highest in the fat and connective tissue of patients with thyroid-associated orbitopathy, where fibroblasts have the potential for adipogenesis. Electrophysiology can now detect subclinical optic neuropathy, and somatostatin-receptor scintigraphy can help justify immunomodulation. Other than steroids, radiotherapy can control inflammation, but its use is controversial. Current trends in orbital decompression are to camouflage incisions and to limit strabismus with balanced decompression, deep lateral wall techniques, fat removal, and onlay implants. Proptosis reductions of 0.9 to 12.5mm are possible by the use of various algorithms. Before or after decompression, botulinum toxin can correct strabismus, intraocular pressure elevation, and retraction. The latter is now also treated with full-thickness blepharotomy.

SUMMARY

As knowledge of the pathophysiology of thyroid-associated orbitopathy grows, there is a slow movement from nonspecific and invasive measures to more directed treatments causing less morbidity.