Assorted Concepts Flashcards
Collagen type in various ocular structures
Driving Criteria
(In order to be eligible for a car/motorcycle license)
- Read a post-September 2001 number plate at 20m
- Visual acuity ≥ 6/12
- Horizontal visual field of 120° with 50° of extension in either direction
- No visual field defects within 20° of the horizontal meridian
If diagnosis which is unlikely to satisfy these conditions, the DVLA must be notified.
Revise occular structures and their germ tissue of origin
How are visual impairments classified
The department of health in the UK classifies patients with visual impairments as severe (blind) or partial.
Severe Sight Impairment (blind)
One of:
- VA < 3/60
- VA 3/60-6/60 AND a severe VFD such as tunnel vision
- VA ≥ 6/60 with significant VFD, particularly affecting the lower fields
Sight Impaired (partial impairment)
One of:
- VA 3/60-6/60 with full VF
- VA 6/18-6/24 with moderate VFD or loss of central vision
- VA ≥ 6/18 with a significant VFD such as hemianopia
Most common cause of blindness in the world
Cataract
Most common cause infective blindness in the world
- Trachoma (1st)
- Onchocerciasis (2nd)
Most common cause of visual impairment in the world
Refractive error
Most common type of colour blindness
Red-green
Most common cause of nutritional blindness
Vitamin A deficiency → nyctalopia
Most common cause of irreversible blindness in the world
Glaucoma
Mitochondrial Inheritance
Mitochondria are inherited on the X chromosome, meaning a father with mitochondrial disease cannot pass it to his son.
- Kearns-Sayre syndrome
- Leber Hereditary optic neuropathy
Kearns-Sayre syndrome
- Increased concentration of mitochondria in muscles
- Causes to myopathy, ophthalmoplegia, ptosis, salt and pepper retinopathy and cardiac conduction defects
Leber Hereditary optic neuropathy
- Ganglion cell degeneration leads to optic atrophy.
- Presents in young men with progressive painless vision loss and a fundoscopic triad of pseudo-oedema, telangiectasia and tortuous vessels.
List 4 X-linked Recessive conditions
A son can only be affected if the mother is also affected.
- Congenital Retinoschisis
- Ocular Albinism
- Fabry Disease
- Lowe Syndrome
List 2 Autosomal Recessive conditions
- Oculocutaneous albinism
- Stargardt’s disease
List 4 Autosomal Dominant conditions
- Congenital Cataracts
- Corneal Dystrophies
- Marfan Syndrome
- Stickler Syndrome: defective collagen 2 syntheses leading to an empty vitreous, RD, deafness and systemic marfanoid and facial abnormalities.
- Neurocutaneous disorders: tuberous sclerosis, Von-Hippel Lindau and neurofibromatosis
Revise diseases associated with specific chromosomes
Coloboma
A coloboma is a hole in the structure of the eye, most commonly the iris. It is uncommon but high-yield in exams.
Revise 3 types of colobomas
Revise organisms and culture mediums
Classsification of Fungi
- Yeast (unicellular)
- Filamentous (grow in branches)
- Dimorphic (features of both yeast and filamentous types)
Candida infection
The yeast Candida albicans infects the retina of immunocompromised people and it is also the commonest endogenous cause of endophthalmitis.
It typically presents with fluffy white retinal lesions.
Aspergillus and Fusarium
Both filamentous fungi associated with keratitis following trauma involving soil or bark.
Histoplasma
A dimorphic soil fungus, endemic to the Mississippi and Ohio river valleys and causes presumed ocular histoplasmosis syndrome (POHS).
Protozoa
Protozoa are single-celled eukaryotic parasites.
Eg. Acanthamoeba
Acanthamoeba
Acanthamoeba is found in water and soil. It causes acanthamoeba keratitis (an orphan disease), typically in contact lens wearers who do not remove lenses whilst swimming or are storing lenses incorrectly.
Toxoplasma gondii
Toxoplasma gondii is transmitted to humans via cats (definitive host). It can also be transmitted vertically by humans and cause congenital toxoplasmosis
Helminth
Helminths are infection-causing parasitic worms.
Eg. Onchocerca volvulus, Toxocara canii
Onchocerca volvulus
Onchocerca volvulus causes onchocerciasis (African river blindness) and is the commonest helminth related ocular infection.
It is transmitted by Simulium blackflies and is endemic to Africa
Ophthalmic excimer laser for refractive surgery
The laser hazard classification (VDE 0837) categorises these therapeutic lasers as class 4, on a scale of 1-4 where 1 is relatively harmless.
Explain the application and effect of various lasers
Medications which raise IOP
- Topiramate (can result in bilateral acute angle-closure secondary to ciliary body swelling
- Steroids
Medications which lower IOP
Cannabinoids and alcohol can transiently lower IOP
Medications which can cause cataracts
- Steroids
- Amiodarone
- Allopurinol
- Busulphan
- Chlorpromazine (a thiazide): fine yellow-brown granules on anterior lens capsule
- Gold: innocuous, anterior capsular deposits in 50% of patients
Medications which cause Vortex Keratopathy
- Fabry’s disease.
- Amiodarone
- Chloroquine
- Tamoxifen
- Chlorpromazine
What is vortex keratopathy
Also known as corneal verticillata
Corneal deposition that has characteristic associations
Corneal verticillata (whorl-like pattern of cream coloured lines in the cornea) in a patient with Fabry’s disease.
Medications Causing Cystoid Macular Oedema
(Retina-related)
- Latanoprost
- Adrenaline
- Glitazones
- Nicotine
Medications Causing Bull’s-eye Maculopathy
(Retina-related)
Chloroquine (also causes renal toxicity and corneal verticillata)
Medications Causing Crystalline Maculopathy
(Retina-related)
Tamoxifen
Medications which affect the optic nerve
- Ethambutol
- Chloramphenicol
- Amiodarone
- Vigabatrin (also associated with binasal visual field defects)
- Isoniazid
Describe the various sutures used for various ocular structures
