Ophthalmology Flashcards
Refractive errors and correction
- nearsightedness (myopia): corrected with a concave lens, which causes the divergence of light rays before they reach the cornea
- longsightedness (hyperopia/metropia): corrected with convex lenses, which cause light rays to converge prior to hitting the cornea
- astigmatism: pt sees lines of a particular orientation less clearly than lines at right angles to them. This defect can be corrected by refracting light more in one meridian than the other. Cylindrical lenses serve this purpose.
- presbyopia: flexibility of the lens declines, typically due to age - difficulty in near vision, often relieved by reading glasses, bifocal, or progressive lenses.
What is the 1 - 2 - 3 - 4 rule?
Systematic way to assess visual problems:
1 - refractive errors
2 - Onset: slow or rapid
3 - age group: children, adults, elderly
4 - causes
Slow onset - children (causes)
- Refractive error
- Strabismus
- Leucocoria
- Rare retina
Strabismus (squint)
Squint (strabismus) is characterised by misalignment of the visual axes. Causes:
- refractive errors: myopia, hyperopia, astigmatism
- congenital, Down’s
- cerebral palsy, developmental delay
- rarely can be associated with retinoblastoma
Strabismus is classified by the direction the eye turns:
Inward turning is called esotropia (convergent)
Outward turning is called exotropia (divergent)
Upward turning is called hypertropia
Downward turning is called hypotropia.
Can also be classified as constant or intermittent
Strabismus - assessment and treatment
- pen torch and examine the light reflex from the two eyes. Is it symmetrical?
Cover test - used to identify the nature of the squint
ask the child to focus on a object:
cover one eye observe movement of uncovered eye - if the eye moves to fix then there is a squint
cover other eye and repeat test - Ophthalmoscope - check red reflex in both eyes (absence would warrant checking for retinoblastoma)
Treatment: - referral to secondary care - eye patches \+/-glasses to correct refractive error - eye muscle surgery
What does untreated strabismus lead to?
Amblyopia (lazy eye) - to avoid double vision caused by poorly aligned eyes, the brain ignores the visual input from the misaligned eye, leading to amblyopia in that eye (the “lazy eye”)
Treatment of strabismic amblyopia often involves strabismus surgery to straighten the eyes, followed by eye patching and often some form of vision therapy (also called orthoptics) to help both eyes work together
What is leukocoria?
Leukocoria (also white pupillary reflex) is an abnormal white reflection from the retina of the eye.
Leukocoria is a medical sign for a number of conditions, including congenital cataract, corneal scarring, melanoma of the ciliary body, retinoblastoma, and retrolental fibroplasia.
Because of the potentially life-threatening nature of retinoblastoma, a cancer, that condition is usually considered in the evaluation of leukocoria. In some rare cases (1%) the leukocoria is caused by Coats’ disease (leaking retinal vessels).
Slow onset - adults (causes)
- Refractive error
- Keratoconus
- Familial
- Childhood eye disorder
Slow onset - elderly (causes)
- Cataract
- Macular degeneration
- Diabetic retinopathy
- Glaucoma
Cataract - assessment
(also look at CCT notes)
- Ophthalmoscopy: done after pupil dilation. Findings: normal fundus and optic nerve
- Slit-lamp examination. Findings: visible cataract
Management
- conservative: prescribing stronger glasses/contact lens, or by encouraging the use of brighter lighting.
- surgical: NICE suggests that referral for surgery should be dependent upon whether a visual impairment is present, impact on quality of life, and patient choice.
Cataract Surgery
Phacoemulsification (cut in sclera and US liquefies lens for removal) + intra-ocular lens implant
- Post operatively: consider steroid eye drops, Abx post op, eyewear
Cataract surgery has a high success rate with 85-90% of patients achieving 6/12 corrected vision (on a Snellen chart) postoperatively.
Complications following surgery:
- Posterior capsule opacification: thickening of the lens capsule
- Retinal detachment
- Posterior capsule rupture
- Endophthalmitis: inflammation of aqueous and/or vitreous humour
Rapid onset conditions (all groups) - the 4 R’s
The 4 Rs 1. Red eye Is the eye red? Is there corneal involvement? Is there pain? (eye or head?)
- Retina - vascular
Retinal artery or vein occlusion - Retina - retina
retinal detachment
“wet” ARMD - Retina - optic nerve
Optic neuritis
ischaemia including arteritis
Retinal Detachment
Risk factors: Age, Previous surgery for cataracts (accelerates posterior vitreous detachment), Myopia, Eye trauma (consider boxing),
In diabetics, retinal detachment occurs in about 60% of patients above 80 years old.
- New onset floaters or flashes - indicate pigment cells entering the vitreous space or traction on the retina
- Sudden onset, painless and progressive visual field loss, described as a curtain or shadow progressing to the centre of the visual field from the periphery
- If the macula is involved, central visual acuity and visual outcomes become much worse.
Retinal Detachement - assessment
Any patients with new onset flashes and floaters should be referred urgently (<24 hours) to an ophthalmologist for assessment with a slit lamp and indirect ophthalmoscopy for pigment cells and vitreous haemorrhage.
On examination, peripheral visual fields may be reduced, and central acuity may be reduced to hand movements if the macula is detached. The swinging light test may highlight a relative afferent pupillary defect if the optic nerve is involved. On fundoscopy, the red reflex is lost and retinal folds may appear as pale, opaque or wrinkled forms.
Optic Neuritis
Causes: MS, diabetes, syphilis
Features
- unilateral decrease in visual acuity over hours or days
- poor discrimination of colours, ‘red desaturation’
- pain worse on eye movement
- relative afferent pupillary defect
- central scotoma
Management
- high-dose steroids
- recovery usually takes 4-6 weeks
Prognosis
MRI: if > 3 white-matter lesions, 5-year risk of developing multiple sclerosis is c. 50%
