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General Medicine for the Optometrist (3)
Dr Russell Watkins
GENETIC DISORDERS
Genetic disorders are not rare In a population of 100,000
10 children will be born with a genetic disorder
10 individuals will develop a genetic disorder in later life
10,000 adults will develop diseases with strong genetic components
GENETIC DISORDERS
Genetic disorders may be classified as Cytogenetic (chromosomal) Mendelian Mutlifactorial
GENETIC DISORDERS
Cytogenetic disorders may be due to Alterations in the number of chromosomes
• Monosomy (2n-1)• Trisomy (2n+1)• Mosaicism
Alterations in the structure of chromosomes• Translocation• Deletion etc
GENETIC DISORDERS
Examples Trisomy 21 (Down Syndrome) Other trisomies e.g. 18 (Edward’s syndrome)
& 13 (Patau’s syndrome) are rare Cri du chat syndrome (deletion of short arm of
chromosome 5 [5p-]) Klinefelter’s & Turner’s syndromes (sex
chromosomes)
GENETIC DISORDERS
Trisomy 21 (Down Syndrome) 95% have a complete extra ch21 (47, XY,
+21) Translocations make up ~4% (usually 21q to
22 or 14) Mosaicism ~1%
GENETIC DISORDERS
General features Short stature, flattened bridge of nose Enlarged tongue, short fingers Simian crease, cardiac problems (septal) Recurrent infections, leukaemia Alzheimer’s
GENETIC DISORDERS
Ocular features of trisomy 21 Hypertelorism Epicanthus & mongoloid slant Ectropion Blepharoconjunctivitis Strabismus & nystagmus
GENETIC DISORDERS
Ocular features of trisomy 21 Keratoconus Cataract Brushfield’s spots Hypoplastic disc Refractive errors (esp. myopia)
GENETIC DISORDERS
Types of Mendelian disorders Autosomal dominant Autosomal recessive X-linked dominant X-linked recessive
BASIC GENETICS Autosomal dominant examples are
Neurofibromatosis Myotonic dystrophy Retinitis pigmentosa Marfan’s syndrome
X-linked dominant examples are rare Y-linked diseases are as yet unknown
GENETIC DISORDERS
Autosomal recessive examples are Cystic fibrosis Retinitis pigmentosa
X-linked recessive examples are Retinitis pigmentosa Choroideraemia
GENETIC DISORDERS
Multifactorial inheritance The major contribution by genetic factors to
disease Do not follow simple Mendelian patterns Determined by the summation of effects of
multiple alleles at different loci together with environmental factors
GENETIC DISORDERS
Mitochondrial inheritance Maternal transmission only Mitochondria found in cytoplasm -
sperm have no cytoplasm Important example
• Leber’s optic neuropathy
ENDOCRINE DISEASE Acromegaly
Rare Caused by a benign pituitary adenoma in
almost all cases Males & females affected equally Incidence is highest in middle age One-third present with change in appearance
& one-quarter present with visual field defects or headaches
Thyroid Eye Disease
Thyroid disease Thyroid gland may be under- or overactive A goitre may be present Thyroid function may be normal in the
presence of a goitre Hypothyroidism may be
• Autoimmune (commonest cause)• Iatrogenic (e.G. Surgery)• Nutritional ( iodine)
Thyroid Eye Disease
Patient may be euthyroid, hypothyroid or hyperthyroid
HLA association varies with different populations
Associated with other AI diseases F:M = 4:1; average age of onset 50yrs TED is worse in smokers
Thyroid Eye Disease
Untreated hypothyroidism results in Mental slowness Hypertension Slow movement Deafness Anaemia Et al
Thyroid Eye Disease Hyperthyroidism
Fairly common; F>M; affects 2-5% of all women at some time Most common causes are Graves’ disease (IgG
antibodies bind to the TSH receptor stimulating thyroid hormone production)
Toxic solitary nodule Toxic multinodular goitre
Patients lose weight, are irritable, get diarrhoea & have many other symptoms
Graves’ Disease
Uncertain aetiology - the following are theories T-cells active against antigen common to orbit
& thyroid gland TSH-receptor Ig may activate T- & B-cells T- & B-cells may activate orbital fibroblasts
self-perpetuating inflammation with consequent fibrosis & tethering
Thyroid Eye Disease
The Werner Classification is useful to assess severity of TED - “NO SPECS”
No symptoms or signs Only signs, e.g. lid retraction, lid lag, SLK Soft tissue swelling e.g. lid oedema Proptosis - unilateral or bilateral EOM involvement - usually IR & MR Corneal ulceration Sight loss - corneal ulceration, optic
neuropathy, OHT
Thyroid Eye Disease Lymphocytic infiltrate 8x increase in EOM size Later, there is necrosis & scarring Ophthalmologists may
Consult with colleagues about thyroid disease control Give lubricants for corneal protection Perform tarsorrhaphy Reduce IOP Use steroids, RT or orbital decompression to relieve
pressure on optic nerve
HYPERLIPIDAEMIA
Triglycerides & cholesterol are transported around the bloodstream in lipoprotein particles Chylomicrons VLDLs IDLs LDLs HDLs
HYPERLIPIDAEMIA
Hyperlipidaemia is a major risk factor for atherogenesis
Synergistic with other risk factors (smoking, DM, hypertension)
Most hyperlipidaemic patients are asymptomatic