Lens and cataracts

Question 1

Lens capsule antioxdiants

Answer 1

contains glutathione and ascorbic acid

Question 2

Lens capsule posterior

Answer 2

Thinnest
Doesnt thicken with age

Question 3

Lens capsule anterior

Answer 3

Thickens with age

Question 4

Lens capsule content

Answer 4

Collagen 4

Question 5

Lens epithelium

Answer 5

single cuboidal cell layer
only found below anterior capsule
periphery - mitotic
central - non-mitotic

Question 6

Lens sutures

Answer 6

Anteriro Y
Posterior inverted Y

Question 7

Lens ultrastructure

Answer 7

Nucleus (old fibres)
Cortex (new fibres)

Question 8

Cataract grades

Answer 8

Immature - partially opaque
Mature - completely opague
Hypermature - cataract material leaking, shrunk and winkly anterior capsule
Morgagnian cataract - cortex had liquified and nucleus has sunk in it

Question 9

Age related Cataract types

Answer 9

Nuclear - centre yellow, myopic shift! near vision improves

Cortical - wedge shaped opacity, glare at night with bright lights

Subcapsular - anterior (blunt trauma), posterior (diabetes, chloroquine, steroids, retinitis pigmentosa, NF)

Polychromatic (christmas tree) - needle like opacities in nucleus and deep cortex

Question 10

Cataract associations:

Anterior subcapsular
Blue dot
Pearly nuclear
Sunflower
Shield like
Christmas tree

Answer 10

Anterior subcapsular - blunt trauma
Blue dot - down syndrome
Pearly nuclear - Rubella
Sunflower - Wilson’s disease
Shield like - Atopic dermatitis
Christmas tree - myotonic dystrophy

Question 11

Congenital cataracts

Answer 11

Autosomal dominant, also due to homocystinuria and Down syndrome

Unilateral - remove at 6 weeks
Bilateral - remove at 10 weeks

Weigh risk between glaucoma and amblyopia

Question 12

Biometry

Answer 12

Calculating IOL power - IOLmaster

Parameters:
Axial length of the eye, corneal curvature, anterior chamber depth

Question 13

Types of IOL

Answer 13

Rigid - PMMA, not widely used

Soft -
1. Silicon - not used
2. Acrylic hydrophobic - less risk of PCO but glare
3. Acrlylic hydrophilic - high biocompatibility but risk of PCO

Question 14

Techniques of cataract surgery

Answer 14

1. Phacoemulsification (gold standard) - US needle
2. extracapsular cataract extraction (ECCE) - wide incision, good for rigid cataracts

Question 15

Phacoemulsification procedure

Answer 15

Question 16

Intraoperative complications of cataract surgery

Answer 16

1. Posterior capsule rupture
2. Floppy iris syndrome (when pt on tamsulosin)
3. Choroidal haemorrhage!!
4. Dropped nucleus (nucleus fragments escape the capsule)

Question 17

Post operative complications of cataract surgery

Answer 17

Early : corneal oedema, elevated IOP, endophthalmitis (1 week)

Late : PCO (most common), Irvine-Gass syndrome (cystoid macula oedema), retinal detachment, delayed endophthalmitis

Question 18

Endophthalmitis prevention

Answer 18

Providone iodine before operation

Question 19

Endophthalmitis features

Answer 19

vitritis (floaters and blurred vision), hypopyon, pain, corneal haze

Question 20

Endophthalmitis mx

Answer 20

Intravitreal abx
vitrectomy

Question 21

Endophthalmitis types

Answer 21

Acute - 1 week, staph epidermidis
Delayed - upto 6 weeks, propionibacterium acne
Post trauma - staph or bacillus cereus
fungal - candida

Question 22

Posterior capsule opacification

Answer 22

Most common delayed complication
Blurred vision, as if cataract has returned
Mx: Nd:YAG capsulotomy

Question 23

Secondary causes of congenital cataracts

Answer 23

Galactosaemia (AR)
Fabry disease (XLR)
Lowe syndrome (XLR)
Down syndrome
Congenital Rubella

Question 24

Lenticonus

Answer 24

Cone like protrusion of lens
Anterior lenticonus - Alport syndrome
Posterior lenticonus - Lowe syndrome

Question 25

Lentiglobus

Answer 25

Hemispherical protrusion of the lens

Question 26

Ectopia lentis

Answer 26

lens displacement

Question 27

What is the direction of displacement in these:

Familial ectopia lentis
Marfan’s syndrome
Homocystinuria
Weill-Marchesani syndrome

Answer 27

Familial - superotemporal (f)
Marfan - superotemporal (f)
Homocystinuria - inferonasal (y)
Weill Marchesani - anterior inferior

Question 28

Congenital aphakia

Answer 28

born without lens, FOX3 mutation

Question 29

U+D=V

Answer 29

U → vergence of light entering the lens (object rays)
D → vergence added to light by the lens (lens power)
V → vergence of light leaving the lens (image rays)

Question 30

Image by minus (biconcave) lens is …..

Answer 30

always virtual, erect and diminished

Question 31

Image by plus (biconvex) lens is

Answer 31

Question 32

Snellen chart

Answer 32

6 stays on top!

Question 33

LogMAR chart

Answer 33

0-1
0 normal vision
1 6/60 vision

each letter 0.02, subtrated from 1

Question 34

Duochrome test

Answer 34

Red - longer wavelength, image forms behind retina
Green - shorter wavelength, image forms in front of retina

Question 35

Retinoscopy

Answer 35

Objective measure of visual acuity
myopia - red reflex moves against direction of light
Hypermetropia - red reflex moves with the direction of light