Lecture 21 - Diseases associated with LVL Flashcards
Albinisim: Describe and cause
Congenital condition characterised by lack of pigment
• Oculocutaneous albinisim
- Tyrosinase negative - reduced pigment (melanin) in the skin and eyes due to lack of enzyme tyrosinase
- Tyrosinase positive - reduced pigment (melanin) in skin and eyes, where the enzyme tyrosinase is present, but other factors reduce the production of melanin.
• Ocular albinisim (reduced pigment in eyes only)
Inheritance of oculocutaneous albinism
• autosomal recessive /autosomal dominant
• Patients with recessive form can be tyrosinase positive or tyrosinase negative
• Reduction in the amount of pigment (melanin) in each of the pigment organelles (melanosomes)
• Incidence = 1 in 20,000 general population
Albinisim: Visual acuity, visual field and ocular signs + symptoms
Visual Acuity
• Tyrosinase negative:
- Most severe effect on VA
- 6/60 - 6/120
• Tyrosinase positive: Better acuity - improve over time (=6/24)
• Ocular: 6/7.5-6/30
Visual field
• Appears full
Ocular signs & symptoms
• Blue irises - transillumination
• photophobia
• nystagmus
• hypoplasia of the macula
• high incidence of strabismus
• poor stereopsis
• high refractive error (with the rule Ast)
Albinisim: Systemic signs/symptoms and associated syndromes
Systemic signs & symptoms
• White or yellowish hair, eyebrows, eyelashes
• Pink skin, sensitive to sun damage
• Albinoidism
Associated syndromes
• Hermansky-pudlak: ( genetic metabolic disorder which causes albinism, visual impairment, a platelet dysfunction with prolonged bleeding, and - progressive symptoms including pulmonary fibrosis, inflammatory bowel disease and kidney disease)
• Chediak - Higashi: generalized cellular disorder which affects all granule-containing cells resulting in recurrent infections and ocular, neurological, and skin manifestations
Albinisim: Low vision management
• Correct Refractive error
• Aperture control contact lenses
• Tints, UV protection (skin protection)
• Magnification for distance & near
Cataract: Describe and Cause
• Opacification of crystalline lens
• Classification according to area affected
- Ant & post subcapsular
- Ant & post cortical
- Equatorial
- Nuclear
Inheritance/Etiology
• Trauma, metabolic, toxic, secondary to inflammation, pharmacologic, hereditary, age-related
• Approximately 95% over the age of 65 have some form of lens opacification
Cataract: Visual acuity and visual field
Visual acuity
• will vary with the degree and location of the opacity most often bilateral but asymmetric
• nuclear sclerotic generally not associated with acuity loss - more myopic
• posterior subcapsular tends to have profound effect on VA -location - especially with papillary constriction
Visual field
• Generally not affected
Cataract: Ocular signs and symptoms
Ocular signs & Symptoms
• Dull or abnormal Ret reflex
• Refraction more myopic
• Reduced acuity
• Increased glare
• Distortion, monocular diplopia
• Altered colour perception
Cataract: Diagnostic testing, Medical treatment and low vision management
Diagnostic testing
• Interferometry
• Potential acuity meter (vernier acuity)
• Ultrasonography
Medical treatment
• Surgical removal
• Mydriatics
Low vision management
• Lighting critical
• Filters & antireflective coating for glare
• Magnification
Diabetic retinopathy: Describe
• Around 2% of the UK population have diabetes, 200,000 - Type 1 and > 1 million
- type 2
• biggest single cause of registered blindness in the UK amongst working age people
• smoking & obesity increase risk type I will tend to show retinopathy within 10 to 12 years
• type I (after 20 years) - 60% will show some degree of retinopathy
Diabetic retinopathy: Types and Signs & Symptoms
2 Types
• type l- juvenile onset: insulin dependent
• type lI - adult onset: non-insulin dependent
Signs & Symptoms
• Excessive thirst
• Excessive urination
• Excessive hunger
• Excessive fatigue
• Weight loss
• Recurrent infections
Diabetic retinopathy: Visual acuity + Visual field
Visual acuity
• From 6/6 to total blindness
- Fluctuations due to blood sugar level if poorly controlled
- Lens changes (myopic)
- CMO (hyperopic)
Visual field
• Secondary complications can cause field loss
- laser burns
- retinal detachment
- glaucoma
- CMO - macular degeneration (MD)
Diabetic retinopathy: Other ocular visual complications
** Other ocular/visual complications**
• Accommodative insufficiency
• Diplopia
• Cataracts
• Glaucoma (rubeosis irides)
• RD
• MD/CMO
• Decreased corneal sensitivity (CL wear)
• Neovascularization
• Hemorrhages
Diabetic retinopathy: Low vision management
Low Vision Management
• Refraction
• Sunlenses & filters
• Increased illumination
• Magnification/minification
• Flashlight/torch
• Non-optical
• Mobility services support groups
Glaucoma: Describe
Group of diseases in which damage to the optic nerve head (ONHoccurs due to increased intracular pressure, poor blood supply of the ONH, a weakness in the optic nerve structure or a combination of the three
• open angle
• angle closure
• developmental
Glaucoma: Ocular symptoms
• open angle - asymptomatic
• angle closure
- pain
- blurred vision
- photophobia
- halos
- nausea & vomiting
Glaucoma: Visual acuity + Visual field and diagnostic testing
Visual acuity
• Generally unaffected until end stage
Visual field
• Typically respects the horizontal midline
- Arcuate defects
- Nasal steps
• Gradually spreads to periphery and centrally
Diagnostic testing
• Optic nerve appearance
• Visual field
• IOP
• Anterior chamber angle
Glaucoma: Low vision management
Low Vision Management
• Magnification
• Lighting (indoors & outdoors) e.g torch @ night
• Glare control, contrast enhancement
• minification
• peripheral awareness systems (prisms, mirrors)
• other professional services
Macular holes: Describe, Visual acuity + field
• appearance: round, red spots in centre of macula
• 1/3 to 2/3 DD in size, may have grey halo around it (RD)
• may be caused by trauma, myopia, CMO, inflammation but most are idiopathic
• Visual acuity: depending on size and location generally 6/9 to 6/120
• Visual field: Full thickness holes generally result in dense central scotomas
Macular holes: Signs+symptoms and low vision management
Ocular signs and symptoms
• Metamorphopsia
• Redudced acuity
Low Vision Management
• Magnification
• Eccentric viewing
• Lighting
• Filters to increase contrast
Macular disease: Describe
• Any degenerative, inflammatory, toxic, vascular or dystrophic condition that affects foveomacular area
• Great variation in form, appearance, onset and involvement
• Majority of low vision patients suffer from some form of macular disease
• Some common macular diseases:
- ARMD (dry [atrophic [& wet[hemorrhaguc] type)
- Stargart’s disease (fundus flavimaculatus)
- Central aerolar choroidal dystrophy (CACD) (circumscribed area of RPE and choriocapillary atrophy in macula - hearing loss)
- Best’s disease
Macular disease: Signs and symptoms
Signs & Symptoms
• Reduced acuity (distance and near)
• Metamorphopsia
• Central field loss
• Reduced colour vision
• Increased glare and photophobia
Macular disease: Diagnostic tests and Low vision management
Diagnostic tests
• Field testing (Amsler grid)
• Colour testing (D 15 - usually red/green loss)
• Fluorescein angiography & electrodiagnostic testing
Low Vision Management
• Refraction
• Magnification (some do not respond favourably e.g CACD)
• Lighting
• Glare control, contrast enhancement, sunlenses & filters
• Non optical, support groups, auditometry etc.
Myopic degeneration: describe
• Excessive stretching and expansion of the posterior segment
• Scleral & choroidal thinning
• Genetic but mechanism of transmission poorly understood
- Rapid increase in incidence and severity in some parts of the world (myopic degeneration is 2d highest cause of low vision in Hong Kong)
Myopic degeneration: Visual acuity+ fields
and ocular signs/symptoms
Visual acuity
• Decreases as condition progresses
• May lead to “no light perception” (NLP) from secondary complications
Visual field
• Degree of field loss will vary with structures involved
Ocular signs and symptoms
• Blurred distance vision
• Flashes & floaters
• Thinning of RPE
• Posterior staphyloma
• Fuch’s spot
• Retinal detachment
