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46 Cards in this Set
- Front
- Back
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What is the lens? |
an avascular non-innervated tissue |
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What are the 3 histological layers of the lens? |
-Capsule • elastic basement membrane • thicker peripherally than centrally -Epithelium • Bow (central, non mitotic) • Cuboidal (equatorial, mitotic) -Lens Fibres • extending from anterior to posterior surfaces meet in register to form lens sutures |
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What changes occur in the lens to lead to cataract formation? |
•Lens growth is continuous throughout life with an increased amount of protein with age – this leads to compression and cataract formation • Lens capsule thins allowing fluid uptake and cataract formation |
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What is a cataract? |
Any condition that leads to a loss in lens transparency due to light scatter or absorption |
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What visual changes are seen as a result of having a cataract? |
• Light scatter may be visualised as haze or glow and produces glare and focusing errors for the patient • Absorption results in shadow or colour changes in the lens usually milky white, yellow, brown or black • This produces refractive error shifts and an altered colour sense |
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What causes a cataract? |
The lens is made up of soluble and insoluble types of proteins. Soluble types are known as crystalline. • Insoluble proteins increase with age. • Protein structure changes with age. • Exposure to UV • Oxidation • Less regular protein packing as protein changes and lens fibres increase. |
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What are the symptoms of cataract? |
•Gradually developing blurred vision in on or both eyes. - worse at night • Glare - worse in bright light or night time vision • Reduced colour vision • Monocular Diplopia • Frequent shifts in refractive error |
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What are the methods used for cataract detection? |
Red-reflex SLIT LAMP Indirect illumination Specular reflection |
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What are the aetiological classifications of cataracts? |
Age- related Congenital Traumatic Intraocular association Systemic disease association Noxious agent association |
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What is the formal cataract classification/ grading system? |
Lens Opacities Classification System (LOCS) |
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What are the risk factors for cataract? |
• Age • Female Gender (hormones) • Sunlight (linked to increased risk of developing cortical cataract) • Smoking (> 25 per day, x3 the risk) • Diabetes (linked to hyperglycaemia) • Steroids (positively correlated with dose and duration) • Alcohol (>4 units per day, x4 the risk) • Severe Dehydration / Diarrhoea |
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What are the three cataract types? |
Congenital • Sight threatening or non-sight threatening Acquired • Induced/toxic • Secondary/metabolic • Traumatic/radiation Age related • Cortical/Nuclear/Posterior Subcapsular • Age related cataracts are the most common |
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What action is taken for congenital sight threatening cataract? |
• Not common (in young children) • Require urgent attention • Surgery to prevent amblyopia |
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What is the action for non-sight threatening congenital cataracts? |
• Conservative management • Usually non- progressive |
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What are the systemic associations with congenital cataracts? |
Associated with systemic disorders, e.g. rubella (sight threatening) |
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What are the origins of congenital cataracts? |
• Most are of idiopathic origin although a large minority have a hereditary trait • Maternal infection • Drug ingestion • Malnutrition • Inborn errors of metabolism • chromosomal abnormalities • prematurity |
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Give three specific examples of sight threatening congenital cataracts |
Posterior polar • small to large opacity close to nodal point Zonular/ lamellar • Dense opacities with clear zones (variable) Rubella • Dense opacity |
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Give specific examples of non- sight threatening congenital cataracts |
• Axial or sutural - Chalky white clusters on or near the sutures • Cerulean - Small blue dots in outer nucleus/ cortex • Coronary - Club like coalescence of dots • Pulverulent - In embryonic nucleus |
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What is a mittendorf dot? |
• Mittendorf dot is a remnant of the anterior end of hyaloid artery. • It is attached to the posterior lens capsule. • It is associated with posterior polar cataract. |
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What may cause an induced/ toxic acquired cataract? |
Associated pathology (e.g.) diabetes |
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What may cause a traumatic/ radiation acquired cataract? |
Blunt injury, penetrating injury, glass blowers cataract (infra-red) (PSC) |
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How is age associated with cataracts? |
Prevalence increases with age • Most patients 75 yrs and above will have some type of cataract |
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What are the three main types of age related cataracts in order of prevalence? |
• Nuclear • Cortical • Posterior Sub-capsular |
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What is the appearance of a nuclear sclerosis cataract? |
Appears as a haze in the nucleus |
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What are the visual effects of a nuclear sclerosis cataract? |
• Causes glare, light loss • Colour change with age (White-Yellow-Brown-Black) • Myopic shift • Can be difficult to refract |
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What is the appearance of a cortical cataract (cuneiform)? |
• Wedges or spokes in cortex • Water accumulation between lens fibres Fine feathery appearanceVacuoles |
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What are the visual effects of a cortical cataract? |
• Starts peripherally with minor effect on vision • Glare • Progresses by expansion and coalescing of spokes |
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What is the significance in the location of a posterior sub capsular cataract? |
Location makes it most debilitating. Impedes ophthalmoscopy |
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What action is taken for a posterior sub capsular cataract? |
Usually requires surgery earlier. |
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What is the appearance of a posterior sub-capsular cataract? |
• Represents a migration and thickening of the lens epithelial cells in the posterior sub-capsular area • Appears as a white ground glass or Swiss cheese like opacity which is often associated with lots of vacuoles |
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Cataracts (typically present as PSC but not always) can also occur secondary to a large number of intraocular diseases, give some examples. |
• Retinitis pigmentosa • Aniridia (congenital absence of iris) • Glaucoma • Anterior Uveitis (inflammation) • Diabetes |
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Describe a Morgagnian cataract |
• A mature (advanced) cataract that appears white and swollen with a liquefied cortex. • A free floating nucleus can usually be seen. • For these types of cataract surgery is more difficult as the lens capsule may break easily |
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What is a Christmas tree cataract? |
- crystalline appearance in lens nucleus |
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How do we assess a patient with a cataract? |
•Preferred and suggested method is slit-lamp assessment, through a dilated pupil •Use standardized clinical grading and photographic systems (comparing a patient's cataract with standard photographs) e. g. Lens Opacities Classification System (LOCS)Accurate VA assessment • Snellen / LogMAR charts or projectors • Pinhole Aperture (limited by cataract density) • Macular Function Test (e.g.) Potential Acuity Measure (PAM) • Entoptic Phenomenon (variable responses) •Contrast Sensitivity and Glare tests •Functional Questionnaires •Mobility Tests |
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What is the management for a patient with a cataract? |
•Wait and watch approach • Do not forget the benefits of a good refraction! •Consider complications with or without surgery Surgical complications Vision loss Social withdrawal •Surgery with psuedophakia is the norm •Optometrist should guide patient’s decision • Give positive BUT guarded prognosis (98% success) •Routine referral via GP or Direct Referral Scheme |
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What are the NHS referral guidelines for a cataract? |
1. Visual acuity 6/12 or worse in worst eye OR 2. The patient has bilateral cataracts, neither of which fulfils the threshold for surgery, but which together reduce binocular vision below the DVLA standard for driving OR 3. A significant optical imbalance (anisometropia or anisekonia) affecting activities of daily living that can only be corrected with cataract surgery AND WHO ARE WILLING TO UNDERGO CATARACT SURGERY |
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What areas are investigated by the NHS referral guidelines for a cataract? |
-Slit lamp examination of cataract is mandatory (dilated pupils?) -Reason for referral must be indicated – which threshold met? -Dilated fundus assessment -Pupillary response assessment -IOP (NCT) -Slit assessment of anterior segment – cornea, AC, Blepharitis (lids) at the very least -Ocular co-morbidity – ARMD, DBR, Amblyopia etc. -Medical History – DB, Hypertension, Shortness of breath, mobility, MI, Stroke, able to lie flat -Medications – warfarin, insulin, alpha blocker, other -Social History – driver, carer, working etc -Only refer patients that WANT surgery -Surgery takes place within 18 weeks of referral (majority) |
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Describe a lens coloboma |
•Congenital •Zonules absent also lens rim relaxation •Affects lower quadrants •Associated with iris, choroidal, & optic nerve colobomata •Associated with giant retinal tears |
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Describe lenticonus of the lens |
•Anterior or posterior coning of lens surface •‘Oil drop sign’ against red reflex •Irregular myopic lenticular astigmatism •Anterior & posterior lenticonus are associated with cataract |
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Describe lentiglobus |
•Generalised hemispherical deformity • Extremely rare • Associated with posterior polar cataract |
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Describe microphakia |
•Small lens due to arrested lens development •Disc-like shape (Lowe syndrome) |
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Describe microspherophakia |
•Small spherical lens, usually bilateral •Zonule visible on pupil dilatation •Iridodonesis & sometimes pupil block glaucoma •Zonular rupture common •Isolated/familial or associated with Marfan’s syndrome |
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What is ectopia lentis? |
• Subluxation or dislocation of the lens due to zonular rupture |
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What are the causes of ectopia lentis? |
• Can be hereditary (eg) Marfan’s Syndrome • Can be acquired (eg) trauma, buphthalmos, anterior uveal tumours, spontaneous - hypermature cataract, high myopia, glaucoma, chronic anterior uveitis |
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What does ectopia lentis result in? |
• Loss of accommodation • Induced Refractive error: Myopia or astigmatism if subluxation (tilt) Hypermetropia if dislocated |
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Give two lens-induced disorders |
Glaucoma Uveitis |
