Lens

Question 1

Lens definition

Answer 1

Transparent biconvex structure with iris and pupil anterior and vitreous body posterior

Question 2

Functions (3)

Answer 2

Second refracting unit of the eye
- converging power 15 - 20D 
- refractive index 1.38 - 1.4
Accommodation
Barrier (infection, aqueous, vitreous)

Question 3

General structure

Answer 3

10mm diameter, 4mm thick
Capsule (collagen IV and glycoprotein matrix to maintain shape + accomodation)
Epithelium (cuboidal anterior capsule and highly mitotic at equator; energy production, metabolism, transport and secretion of capsular material)
Nucleus and cortex (lens fibres from epithelium and proteins alpha, beta and gamma crystallins)
Suspended by suspensory ligaments and zonules

Question 4

Accommodation

Answer 4

Cilliary muscle contracts

1. Lens becomes more globular/convex
2. Miosis via PNS to limit light
3. Convergence via medial rectus to prevent diplopia

Question 5

Cataract definition

Answer 5

Lens becomes opaque

Question 6

Cataract causes

Answer 6

Senile
Congenital (i/3 AD, 1/3 trauma, galactosemia)
Infectious (rubella, toxo)
Metabolic (DM, galactosemia)
Trauma
Steroids (predforte, FML, dexamethasone)
Atopy
Hypocalcemia

Question 7

Cataract morphology

Answer 7

Nuclear (deepening, diffuse brunescence)
Subcapsular (opacification beneath capsule, commonly post. causes included steroid tx, antidepressants, amiodarone CVS medication)
Cortical (discrete, spoke-like opacities)

Question 8

Cataract presentation

Answer 8

Visual disturbances ie gradual loss of clarity
Progressive myopia due to increased nuclear density
Glare esp at night while driving
Bilateral/unilateral
Children don’t complain - incidental finding

Question 9

Cataract examination

Answer 9

VA for level of impairment
Fundoscopy for retinal health (do visual fields if no fundoscope)
U/S for mass or retinal detachment
EUA in infants with leukocoria

Question 10

Leukocoria differential

Answer 10

Retinoblastoma
Cataract
Corneal opacification
ROP
Retinal dysplasia

Question 11

Cataract surgery complication

Answer 11

Posterior capsulorrhexis

Question 12

Cataract surgery types

Answer 12

ICCE
ECCA
Phacoemulsification

Question 13

Cataract surgery indications

Answer 13

Improve visual fx
Diabetic retinopathy
Lens-induced glaucoma
Uveitis

Question 14

Cataract surgery considerations

Answer 14

Choice of anesthesia
Incision type
Technique
Aphakia correction

Question 15

Cataract surgery prognosis

Answer 15

80% get 6/12 vision
Failure is due to preexisting disease
If subsequent posterior capsular opacification, tx is laser capsulotomy (YAG)

Question 16

Ectopia lentis definition

Answer 16

Partial/complete dislocation of lens from physiological position
Associated with glaucoma
Acquired causes - trauma + syphilis
Hereditary causes - Marfan’s syndrome

Question 17

Myopia

Answer 17

Near/shortsightedness
Eyeball AP is too long or lens is too strong -> image focused in front of retina
Correct with biconcave lens

Question 18

Hypermetropia

Answer 18

Farsightedness
Eyeball AP is too short or lens is too weak -> image is focused behind the retina
Correct with biconvex lens

Question 19

Biconcave lens makes eyes look…?

Answer 19

Smaller

Question 20

Biconvex lens makes eyes look…?

Answer 20

Bigger

Question 21

Presbyopia

Answer 21

Loss of accommodation
Lens loses elasticity
Correct with bifocal/reading glasses

Question 22

Meaning of anisometropia?

Answer 22

Unequal refractive errors between two eyes

Question 23

Monocular diplopia

Answer 23

Diplopia persists when one eye is closed

Question 24

Binocular diplopia

Answer 24

Diplopia only seen when both eyes are open

Question 25

What must you be careful of when treating a child born with discharge in the eye?

Answer 25

Ointment causes blurry vision which can induce amblyopia so always use in both eyes!

Question 26

Meaning of binocular single vision?

Answer 26

Slightly dissimilar images from both retinas are fused centrally to be interpreted by the brain as a single image

Question 27

Causes of isolated nerve palsies

Answer 27

Vascular disease (diabetes mellitus, hypertension, aneurysm, cavernous sinus thrombosis)
Trauma
Orbital disease
Neoplasia
Raised ICP (false localising, 3rd, 6th)
Inflammation (sarcoidosis, vasculitis, infections, GBS)

Question 28

Extra-ocular muscle diseases

Answer 28

Dysthyroid eye disease
Myasthenia gravis
Ocular myositis
Ocular myopathy
Brown's syndrome
Duane's syndrome

Question 29

Pseudoesotropia

Answer 29

Diagnosis of exclusion

Small interpupillary distance (IPD)
Epicanthal folds
Flat nasal bridge
Pinch nasal skin and then check light reflex

Question 30

Infantile esotropia

Assessment and treatment

Answer 30

Fixation reflex
Cover uncover test
Refraction by cycloplegic drugs
Fundoscopy to evaluate any organic disease eg retinoblastoma

Treatment = surgical recession of both medial recti

Question 31

Accommodative esotropia

Answer 31

Often seen in pt with moderate hypermetropia

Attempt to focus eyes -> converge at same time

Question 32

Causes of intermittent exodeviations

Answer 32

Divergence excess

Convergence weakness

Question 33

Causes of constant exodeviations

Answer 33

Congenital
Sensory
Consecutive

Question 34

Right hypertropia may clinically appear as…?

Answer 34

Right pseudo-ptosis

Question 35

Types of amblyopia?

Answer 35

Strabismic
Anisometropic
Deprivation (cataracts, corneal scarring)

Question 36

What typically is the cause of corneal scarring in children?

Answer 36

Forceps injury during birth

Question 37

Which patient are you most suspicious of retinoblastoma in?

Answer 37

Child born with straight eyes that develops a squint by age 2