Key Points 7 Flashcards
What type of secretions come from Meibomian glands?
Holocrine
What percentage of optic nerve axons cross in the chiasm vs ipsilateral axons?
Approximately 52% of the optic nerve axons cross in the chiasm, whereas 48% remain ipsilateral.
When should tapering steroid doses be considered?
40mg daily in the morning for more than 1 week
repeated evening doses
received more than 3 weeks of treatment
taken a short course but within a year of stopping longterm treatment
What is Sherrington Law
states that when one extraocular muscle is stimulated, the ipsilateral antagonist is inhibited
What is acute retinal pigment epitheliitis
a rare self-limiting inflammatory condition of the macular RPE. It typically affects young adults and is unilateral in 75% of cases.
What conditions are associated with angioid streaks?
Pseudoxanthoma elasticum
Ehler’s Danlos
Paget’s disease
Sickle cell disease
Idiopathic
PEPSI
Efficacy vs Effectiveness?
Efficacy = the effect of something under ideal or laboratory conditions.
Effectiveness = the effect of something in the real world.
What are the features of Pigment Dispersion syndrome?
more common in males and is associated with myopia. The rate of pigment deposition often reduces after the age of 40, perhaps because of the enlarging lens and the changing shape of the iris-lens diaphragm preventing chaffing of the iris pigment against the zonules. Pigment dispersion syndrome responds better to ALT than standard POAG because of the increased pigment in the trabecular meshwork allowing better absorption of laser.
which IOL material is most likely to develop glistenings?
Hydrophobic acrylic IOLs have been associated with glistenings in the optic. These glistenings are water (from the aqueous) that becomes trapped as droplets in a hydrophobic environment.
What are features of congenital (infantile) esotropia?
large angle esotropia, usually greater than 30 PD
onset usually during the first few months, by definition by 6 months of age
cross-fixation may be present
latent nystagmus
dissociated vertical deviation (in up to 60%-70%)
inferior oblique overaction with V-pattern esotropia (in up to 60%-70%)
mild hyperopia, + 1.00 to + 2.00 D
Risk factors for developing ROP?
hyperoxia, low gestational age, and low birth weight
Which conditions show Intermediate uveitis?
sarcoidosis, multiple sclerosis (MS), Lyme disease, tuberculosis (TB), and syphilis. Idiopathic intermediate uveitis, or pars planitis, accounts for >80% of cases. Eighty percent of pars planitis cases are bilateral.
What is the commonest cause for reduced vision in pars planitis?
Macular oedema, followed by cataract, is the most consistent cause of decreased vision in pars planitis. Cystoid macular oedema (CMO) may complicate anterior or posterior uveitis, but much less frequently.
What is phacoanaphylactic anaphylaxis?
occurs as a result of an immune response to lens proteins released following the rupture of the lens capsule which may occur following trauma or incomplete cataract extraction.
What are the features of superior division CN3 palsy?
superior rectus and levator palpebrae affected
Which study from the 1980s recommended grid pattern macular photocoagulation for persistent macular oedema if visual acuity was 20/40 or less and in the absence of non-perfusion:
BVOS
In Possner-Schlossman syndrome raised IOP is believed to be the result of:
involves an acutely raised IOP secondary to trabeculitiis with open angles. It is believed to be precipitated in many cases by Herpes simpex virus.
A patient has a homonymous visual field defect respecting the midline and complains of experiencing formed visual hallucinations.
These features are MOST in keeping with a lesion of the:
A temporal lobe lesion causes an incongruous, contralateral upper homonymous quadrantanopia. It may also give rise to formed visual hallucinations. This is in contrast to the occipital lobe, where visual hallucinations are unformed.
A 45-year-old man presents with rapid onset non-axial proptosis and pain. Incisional biopsy of the mass shows a ‘Swiss cheese’ appearance.
What is the most likely diagnosis?
Adenoid cystic carcinoma can present with pain due to perineural spread. It has a classic ‘swiss-cheese’ appearance on histology.
What proportion of congenital NLD is bilateral?
Less than 10%
What is the most likely outcome following inadvertent suturing of the orbital septum into subcutaneous tissues when repairing a partial-thickness upper eyelid laceration?
upper lid retraction in downgaze.
At what wavelength does he Nd:YAG emits infrared radiation
1064nm
Which conditions are ALT likely to be effective?
ALT is successful in:
primary open angle glaucoma
pigmentary glaucoma
pseudoexfoliation glaucoma
normal tension glaucoma
Which conditions are ALT not likely to be effective?
paediatric glaucomas
secondary glaucomas
Causes of pseudo-RP on fundus exam?
drugs: chloroquine, quinine, phenothiazine
syphilitic neuroretinitis
rubella retinopathy
measles retinopathy
laser scars
chronic uveitis
cancer-associated retinopathy
old retinal detachment
old central retinal artery occlusion
old trauma
Most rigid gas permeable contact lens wearers should discontinue use of their lenses at least how many days before a refractive surgery evaluation?
Stability of refraction and topography are important when deciding on a surgical plan. Most surgeons require at least 2 to 3 weeks off contact lenses to verify stability.
What are the Systemic associations of scleritis
RA
polyarteritis nodosa
relapsing polychondritis
Wegener’s
inflammatory bowel disease
Reiter’s syndrome
Behcet’s disease
ankylosing spondylitis (rare)
Drugs to avoid in myasthenia gravis:
aminoglycosides (e.g. gentamicin, streptomycin)
fluoroquinolones (e.g. ciprofloxacin, levofloxacin)
macrolides (erythromycin, azithromycin)
neuromuscular junction blockers (e.g. suxamethonium, botox)
beta blockers
chlorpromazine
respiratory suppressants (e.g. morphine)
procainamide
penicillamine
What are the causes of microspherophakia
Weill-Marchesani syndrome
Alport’s syndrome
Marfan’s syndrome
Peter’s anomaly
Congenital rubella
Hyperlysinaemia
What visual field test results are unacceptable for UK drivers?
a cluster of 4 or more adjoining points that is either wholly or partly within the central 20 degree area
loss of both a single cluster of 3 adjoining missed points up to and including 20 degrees of fixation and any additional separate missed points within 20 degrees of fixation
any central loss that is an extension of a hemianopia or quadrantanopia of size greater than 3 missed points
What is the Parks Bielchowsky test?
- Determine which eye is hypertropic. This tells you that the involved muscle is one of the two depressors in the hypertropic eye, or one of the two elevators in the hypotropic eye. With this first step complete, choices are narrowed from eight muscles down to four muscles.
- Decide in which gaze the hypertropia is worse. By using the field of action of the four vertically acting muscles, the choices can always be narrowed down to two. In this example, the right hypertropia, which is worse on left gaze, indicates either the right superior oblique (the depressor of the right eye in left gaze) or the left superior rectus (the elevator of the left eye in left gaze)
3.Determine if right or left head tilt worsens the hypertropia. If the deviation is worse when the head is tilted towards the hyper-tropic eye, then the defect is in an oblique muscle; if the deviation is worse when the head is tilted towards the hypo-tropic eye, then the defect is in a rectus muscle.
What are Vogt’s limbal girdle.
bilateral inter-palpebral narrow, crescentic chalky flecks at the nasal and temporal limbus.
A 6-year-old presents with a painless, bluish mass on the nasal quadrant of the upper lid. The lesion enlarges whenever she coughs.
What is the most likely diagnosis?
Lymphangioma usually presents in childhood and can be:
Anterior: bluish lesion (venous blood); size may increase with Valsalva
Posterior: slowly progressive proptosis which may increase suddenly if there is a spontaneous bleed.
Note that primary orbital varices usually have no external signs unless accentuated by a Valsalva manoeuvre.
When can GAT be falsely low?
corneal oedema
low central corneal thickness
post laser refractive surgery
too little fluorescein dye
with-the-rule astigmatism over 3D
high myopia (due to decreased scleral rigidity)
When can GAT be falsely high?
increased central corneal thickness
digital pressure on the globe
applanation over a corneal scar
too much flurorescein drops
against-the-rule astigmatism over 3D
When is tube surgery done in glaucoma?
Tubes are usually reserved for those glaucoma cases in which there is salvageable vision and standard filtration surgery would fail or has already failed.
What are the indications for tube surgery in glaucoma?
failed trabeculectomy
active uveitis
neovascular glaucoma
inadequate conjunctiva
impending need for PK
synechieal angle closure (e.g. ICE syndrome)
A 1-week-old baby is noted by paediatricians to have an abnormal red reflex in both eyes. On examination, you discover dense, bilateral lamellar cataracts, but no other ocular abnormalities.
Which of the following is the most appropriate therapy for this infant?
perform surgery on one eye with immediate aphakic correction and perform surgery on the other eye before 3 months of age
What % of patients with active ROP develop cicatricial complications?
Only 20%
According to the CNTGS study, what proportion of untreated patients with normal tension glaucoma show no evidence of glaucoma progression over 5 years?
35% of control (untreated) eyes with normal tension glaucoma showed evidence of disease progression over 5 years; in other words 65% did not progress. By comparison, in the treated group of eyes with NTG, 12% showed evidence of progression (88% did not progress).
A patient has synchysis scintillans. Which history is most consistent with this diagnosis?
prior blunt ocular trauma with vitreous haemorrhage
Synchysis scintillans can occur after resolution of vitreous haemorrhage. Refractile, yellow, cholesterol crystals float freely in the liquefied vitreous and tend to settle inferiorly with time.
Where do the a and b waves in ERG correspond to?
a- wave originates from photoreceptors while the b- wave originates from bipolar cells.
What are the causes of a negative ERG?
congenital stationary night blindness
X-linked retinoshisis
central retinal artery occlusion
