Encyclopedia of Ayurvedic Medicinal Plants

NON- INFECTIOUS SYSTEMIC EYE  DISEASE

Thyroid associated disease                                 

Orbital inflammatory conditions

Orbital cellulitis presents as redness, swelling and tenderness in the periocular tissues In preseptal cellulitis the infection is confined to the eyelids, and is usually a complication of a localised infective focus such

as a chalazion. In true orbital cellulitis the structures behind the orbital septum are involved, producing the 'orbital apex syndrome' of proptosis, visual loss, external and internal ophthalmoplegia, ptosis and sensory loss in the distribution of the 1st and 2nd divisions of the 5th cranial nerve . The infection is often derived from the paranasal sinuses, but may be from haematogenous spread or from an infected globe (endophthalmitis). Once established, orbital cellulitis may be complicated by subperiosteal abscess formation or spread via the orbital veins to produce cavernous sinus thrombosis or brain abscess. The causative organisms are generally staphylococci, streptococci or haemophilus. Treatment is with high dose parenteral antibiotics while closely monitoring the patient for complications.

Orbital pseudotumour  is an idiopathic, non-granulomatous inflammation of

the orbital soft tissues. It presents acutely, mimicking orbital cellulitis, or more slowly, mimicking thyroid - associated disease. It may be unilateral or bilateral. Middle - aged females are most commonly affected. Pain is a prominent symptom; other features are lid swelling, chemosis, proptosis and

restrictive ocular myopathy. Histologically it consists of a mixed inflammatory cell infiltrate consisting of neutrophil and eosinophil polymorphs, plasma cells and lymphocytes. With disease progression there is a prominent fibroblastic reaction involving orbital fat and extraocular muscle. A similar process may affect the orbital apex (Tolosa - Hunt syndrome) causing early visual loss. Treatment involves steroids, immunosuppressives and radiotherapy. Palliative orbital decompression may have a role in selected cases.

Ocular manifestations of thyroid disease

Hyperthyroidism (Thyrotoxicosis)

Thyrotoxicosis is the clinical syndrome caused by excess secretion of thyroid hormones. Thyrotoxicosis is a feature of two quite distinct disease entities: toxic nodular goitre and Graves' disease.

Toxic nodular goitre

In this condition, thyroid hormones are secreted by a thyroid adenoma independently of the normal pituitary controlling mechanism . Multinodular disease occurs in females over 60 years old, and the less common singular nodule is seen in younger patients. Unless the tumour is sufficiently large to cause symptoms by local compression the clinical features of the disease are the consequence solely of this excess secretion. The only ocular abnormality to be found is over activity of the sympathetically innervated fibres of the levator palpebrae superioris muscle. Normally the upper eyelid covers some of the iris, but in this condition a rim of white sclera is exposed above the upper margin of the iris, causing a staring appearance with widening of the palpebral fissure and lid retraction when the patient looks ahead. If lid retraction is not observed, lid lag may be

demonstrated by asking the patient to follow the examiner's finger held at

arms length from him through an arc from 45° above to 45° below the horizontal.

Graves' disease

Graves' disease is an autoimmune, systemic disease affecting many tissues

which may include the thyroid gland and the eye. Unlike the toxic nodular

goitre whose clinical manifestations are only those of excess thyroid hormone secretion, in Graves' disease thyrotoxicosis is usually, but not always, present and is only part of the disorder, and the ocular changes, except for lid retraction are due to other still unknown causes. Graves' disease is due to the presence of IgG antibodies to the TSH receptor of the thyroid follicular cell. The features of Graves' disease are: Hyperthyroidism, when present, is due to excess thyroid hormone secretions, the production of which is stimulated by ill understood factors whose effect is superimposed on the normal pituitary and hypothalamic controlling mechanisms. It is the nature of the control which has changed and the patient may be either hyperthyroid or euthyroid

Pre-tibial myxoedema is characterised by bluish brown plaques of

mucopolysaccharide infiltration which are found on the feet and lower legs. It can occur in association with finger clubbing, phalangeal periosteal new bone formation and overlying oedema, a triad known as thyroid acropachy.

Diagnosis and differential diagnosis of endocrine exophthalmos

The presence of bilateral exophthalmos if associated with a goitre and the

other manifestations of Graves' disease should present little difficulty in diagnosis.

    Where necessary the diagnosis may be confirmed by immunological

tests for thyroid peroxidase or microsomal antibodies. The main differential

diagnostic problem is from an orbital tumour, and CT and MRI scanning is

very useful in determining the involvement of extraocular muscles. Thickenedmuscle bellies, particularly of the inferior rectus and medial rectus are characteristic of this disease. In addition to these tests there are some helpful clinical pointers, such as the presence of both upper and lower lid retraction and asymmetry of exophthalmos which is rarely greater than 6mm in endocrine exophthalmos, whereas it can be more than this in many orbital tumours.

Management of endocrine exophthalmos

It is important to follow the progress of any type of proptosis by serial exophthalmometer measurements. This is a simple instrument which measures the distance forward from the lateral bony margin of the orbit to the anterior convexity of the cornea. It can be done simply by a millimetre scale but more accurate measurements are possible with one of the special instruments of which Hertel's exophthalmometer, in which an inclined mirror superimposes the corneal image on a millimetre scale, is one of the most useful  The endocrine exophthalmos may threaten vision by exposure keratitis, retinal oedema, papilloedema and optic nerve compression. Exposure of the cornea in mild cases is prevented by methyl cellulose drops or eye ointments and vaseline gauze dressings. Tarsorrhaphy is necessary if the condition is progressive and should not be long delayed as it may become difficult to accomplish when the orbital pressure is tending to separate the lids.

    When optic nerve function is threatened, treatment is urgent and is aimed at shrinkage or escape of the orbital soft tissue. This may be done medically

using high dose oral corticosteroids, or with orbital radiotherapy, or both.

Diabetes mellitus and the eyes

The size of the problem

Many features of diabetes mellitus are those of a systemic immune disease.

Although renal and arterial disease are the main causes of death in diabetics,

the ocular complications of the disease are a major determinant of disability.

Diabetics are about 15 times more likely to go blind than non-diabetics and this disease accounts for about 7% of the newly registered blind. Diabetes is now the commonest single cause of blindness in patients under 65 years in Great Britain and Diabetes UK estimate the prevalence of registerable blindness caused by diabetes to be 100 per million of the population.

Diabetic eye disease

The main causes of blindness in diabetic patients are retinal disease, accounting for about 80%, and cataract formation which accounts for the majority of the remaining 20%. Other ophthalmic conditions to which diabetics are liable include optic neuritis and extraocular muscle palsy, both of which usually have a favourable prognosis. Diabetes causes widespread changes in the tissues of the eye including degenerative changes in the epithelium of the iris and ciliary body. Although the lens and retina may be affected together they will be considered separately here for convenience.

The retina in diabetes

General retinal vascular changes, including those occurring in diabetics, have been considered on p290. The most important factors affecting the incidence of diabetic retinopathy are age and the duration of the disease. More than 90% of insulin-dependent diabetics have some form of retinopathy after 20 years. Established retinopathy is adversely affected by co-cxistent hypertension. The visual symptoms may be gradual when there is slow encroachment on the macula of a ring of exudates surrounding an area of oedema or microaneurysms or rapid when a vitreous haemorrhage occurs. It is important to classify the grades of diabetic retinopathy

pre-proiiferative diabetic retinopathy. Fundal changes of this stage in the

disease process are characterised by the presence of cotton-wool spots

deep and superficial haemorrhages, intra-retinai microvascular anomalies,

venous dilatation, looping and irregularities. By definition, no new vessels

are present.     

Behget's syndrome

This is more common in Mediterranean countries and in Japan and is

believed to be higher in populations around the ancient Silk Road. It is linked with HLA B5 (found in 80% of cases in Turkey) and occasionally C4 antigens.The disease is characterised by recurrent uveitis with hypopyon  and buccal and genital ulceration. The basis of these manifestations is an obliterative vasculitis . Retinal vessels may be affected and can be reduced to thread-like proportions associated with optic atrophy. Thrombo-phlebitis of the legs and aneurysms of large arteries may occur. Antibodies to mucosa from several sites including the mouth have been demonstrated but tests for rheumatoid and antinuclear factor are usually negative. There is also evidence of cell mediated delayed hypersensitivity. Treatment is with immuno-suppressants such as corticosteroids, colchicine, thalidomide and cyclosporin.

Systemic lupus erythematosus

Systemic Lupus Erythematosus (SLE) is a multisystem, inflammatory disease characterised by the presence of autoantibodies leading to the deposition of immune complexes in the small blood vessels with resulting local fibrinoid necrosis due to complement activation. Its prevalence is 4-250/100,000 and is more common and severe in Asians and black Americans, affecting women predominantly (female to male ratio 10:1). Diagnostic features include a macular and discoid skin rash, photosensitivity, oral ulcers, arthritis, serositis, CNS disease such as diplopia, nystagmus and psychosis, haemolytic anaemia, leucopenia, thrombocytopenia, and immunological disorders involving the LE cell, anti-dsDNA, anti-Sm and antinuclear antibodies. Renal involvement makes the prognosis poor. The tissue damage mainly results from activation of complement .Antinuclear factors can be demonstrated by immunofluorescence in almost all patients. The ESR is raised and serological tests for syphilis may be falsely positive.

Sarcoidosis

This systemic disease of unknown aetiology with widespread granulomatous

lesions shows a uniform histological picture of epitheloid cell non-caseating

follicles which undergo resolution by hyalinisation followed by fibrosis.

Sarcoidosis is believed to be a malformation of T-lymphocytes and patients

with sarcoidosis have long been known to give a negative Mantoux reaction.

It is more common in females over the age of 15 years who may present with lung disease due to pulmonary infiltrates, bilateral hilar lymphadenopathy and skin or eye lesions.

The eyes may also be affected in sarcoidosis in respect of:

-conjunctival follicles of characteristic appearance especially in the lower

fornix fold which may be a useful source of tissue for biopsy.

-calcifications of the cornea and conjunctiva due to a raised serum calcium

associated with calciferol sensitivity .

-kerato-conjunctivitis sicca from tear deficiency resulting from lacrimal gland infiltration.

-vasculitis retinae mainly affecting veins, causing irregularity in calibre and

peri vascular cuffing and pigment epithelial defects, both of which may be

revealed by fluorescein angiography even when not clinically obvious.

-orbital masses which may cause proptosis, and paralytic squint.

-meningeal sarcoidosis where granulomas may also cause extraocular muscle palsies, diabetes insipidus, and affect the optic nerves. There may be raised intracranial pressure and papilloedema.

Treatment of ocular sarcoidosis

Posterior uveitis and anterior uveitis of marked degree and those with vasculitis

require systemic steroids. Topical steroids and mydriatics are used in

mild anterior uveitis cases. Steroid therapy will have to be continued in the

absence of resolution, although the side effects of steroids have to be weighed carefully against the degree of ocular inflammation and decisions can be dif ficult. Azathioprine is then sometimes used as an alternative medication. Fortunately in most patients the condition gradually resolves allowing treatment to be reduced progressively so that most patients emerge with minimal impairment of ocular function; very rarely the inflammation may be severe and fail to respond to treatment leading to secondary glaucoma, cataract, optic nerve involvement and loss of vision.

Phakomatoses

The phakomatoses are a group of conditions in which a variety of structures

derived from neuroectoderm are affected by hamartomas (congenital overgrowths of tissue which is normally found in that location). They are frequently inherited and ocular involvement is common