lens and cataracts

Question 1

define lens

Answer 1

lens is a biconvex crystalline structure located between the iris and vitreous. It has a power of 15–20D in adults and 43–47D in infancy. Its high-protein (crystalline) content gives the lens a high refractive index of about 1.4.

Question 2

what happens at near accomodation

Answer 2

The eye brings near objects into focus by contracting the ciliary muscle. This results in the relaxation of the zonules making the lens more spherical and increasing its diopter power.

Question 3

what happens at far accomodation

Answer 3

The eye brings far objects into focus by relaxing the ciliary muscle. This increases zonular tension, making the lens flat.

Question 4

histology of capsule cataract

Answer 4

● An outer transparent basement membrane.
● Thinnest posteriorly and thickest near the equators.
● Made of type IV collagen and glycosaminoglycan.
● Anterior capsule thickens with age, but the posterior capsule maintains the
same thickness.

Question 5

histology of epithelium cataracts

Answer 5

● Simple cuboidal cells located beneath the capsule.
● Central zone: Present on the anterior surface of the lens.
● Pre-equatorial zone: Cells undergo mitotic division throughout life and form
the lens fibres.
● No epithelium on the posterior surface of the lens.

Question 6

histology of lens fibres cataracts

Answer 6

● Lens fibres elongate, pushing the older fibres deeper into the lens.
● The nucleus is the innermost part, which is present at birth, and the cortex is
the outer part, which contains the youngest fibres.
● The junction of lens fibres forms sutures:
Anterior suture: Has an upright Y-shaped suture. Posterior suture: Has an inverted Y-shaped suture.

Question 7

histology of zonules cataracts

Answer 7

Suspensory ligaments, made of fibrillin, attached to the lens equator.

Question 8

what is cataract maturity

Answer 8

progressive cloudiness of the lens causing gradual vision loss and blindness if untreated. It is the leading cause of blindness worldwide.

Question 9

grading of cataracts

Answer 9

● Immature cataract: Partially opaque.
● Mature cataract: Completely opaque.
● Hypermature cataract: Shrunken anterior capsule due to leakage of material/water outside the lens.
● Morgagnian cataract: A form of hypermature cataract with cortex
liquefaction causing the nucleus to sink. Complications include phacoanaphylactic uveitis and phacolytic glaucoma.

Question 10

classification of age-related cataracts

Answer 10

nuclear, cortical, subcapsular and polychromatic cataracts.

Question 11

what is nuclear sclerotic
signs
patho

Answer 11

EARLY - yellowing of the crystalline lens due to the deposition of the urochrome pigment.

LATE - brown

increase in refractive index of the nucleus and increased spherical abberation- myopic shift leading to ‘second sight’ phenomenon

lens becoming harder, the refractive index increases, allowing for some elderly patients to read without glasses.

Question 12

what is cortical cataracts

Answer 12

opacities start as clefts and vacuoles between lens fibres due to hydration of the cortex.

Subsequently opacification results in typical cuneiform (wedge-shaped) or radial spoke-like opacities
opacification of the lens cortex.

wedge-shaped opacities

Question 13

predominant Sx of cortical cataracts

Answer 13

glare - especially from headlights while driving at night.

this is due to light scattering

Question 14

anterior subcapsular cataract

Answer 14

opacities under the anterior capsule

under the lens capsule and ass w fibrous metaplasia of the lens epithelium

Question 15

posterior subcapsular cataract

Answer 15

Opacities just in front of the posterior capsule. Glare is acommon symptom.

vacuolated , granular or plaque-like appearance on oblique slit lamp biomicroscopy

black on reteroillumination

Patients may complain of difficulty seeing in bright light and near vision.

Question 16

description of polychromatic ‘xmas tree’ cataract

Answer 16

Characterized by needle-like opacities in the deep cortex and nucleus

Question 17

acquired anterior subcapsular cataracts examples and their ass

● Blunt trauma 
● Atopic dermatitis
 ● Wilson disease 
● Post-congestive angle closure glaucoma 
● Gold 
● Infrared radiation

Answer 17

● Blunt trauma (flower-shaped cataract)
● Atopic dermatitis (shield-like cataract)
● Wilson disease (sunflower cataract)
● Post-congestive angle closure glaucoma (glaukomflecken)
● Gold (drug induced)
● Infrared radiation (glass-blower cataract)

Question 18

posterior subcapsular cataracts examples and their ass

Answer 18

● Corticosteroids
● Diabetes (snowflake shaped)
● Retinitis pigmentos
● NF2
● Chloroquine
- myotonic dystrophy - stellate

Question 19

other cataracts
myotonic dystrophy
rubella
down syndrome
hypoparathyroidism

Answer 19

● Christmas tree-like cataract appearance: Myotonic dystrophy
● Pearly nuclear sclerotic cataract: Rubella
● Blue dot cataract: Down syndrome
● Polychromatic cataract: Hypoparathyroidism

Question 20

Gold standard Mx for cataracts

Answer 20

phacoemulsification

This technique uses an ultrasonically driven needle (phaco tip) to chop the nucleus and then aspirate the lens material.

Question 21

other type of Mx for cataracts

Answer 21

Extracapsular cataract extraction (ECCE): May be used for very hard cataracts.

Question 22

advantages of phacoemulsification

Answer 22

● Smaller incision
● Less astigmatism
● Faster recovery
● Reduced complications
● No sutures needed

Question 23

what is intraocular lens power

Answer 23

IOL power is determined by measuring the curvature of the cornea and eye length. Power (P) is calculated using the following equation:
P = A − 2.5L − 0.9K

where:
● A is a constant supplied by the manufacturer.
● L is the axial length of the eye, measured using A-scan ultrasonography.
● K is the average corneal power reading in diopters.

Question 24

what is rigid IOL

Answer 24

● Made of polymethylmethacrylate (PMMA).
● Requires a larger incision. more than 5mm
● Higher rates of posterior capsular opacification (PCO) than flexible IOL.

Question 25

what is flexible IOL types

Answer 25

● Used in modern cataract surgery. - smaller incision ● Three types Acrylic hydrophobic IOL: Has a higher refractive index and lower rates of PCO than its hydrophilic counterparts. However, can cause dysphotopsia (troublesome glare). greater reaction in uveitic eyes Acrylic hydrophilic IOL: Has higher biocompatibility. However, calcification of the lens (causing lens opacities) may occur. better with uveitic eyes Silicone IOL: Less commonly used in modern phacoemulsification.

Question 26

complications of intraoperative surgery

Answer 26

- Posterior lens capsule rupture. - Floppy iris syndrome: A flaccid iris that can complicate surgery. It usually occurs with some patients on alpha blockers (e.g. tamsulosin). Intracameral phenylephrine can be used to dilate pupils in high risk patients

Question 27

complications of postoperative surgery

Answer 27

Early: Corneal oedema, elevated IOP and acute endophthalmitis. Late: PCO (most common complication), Irvine-Gass syndrome (CMO post cataract surgery), retinal detachment (especially in patients with high myopia) and delayed endophthalmitis.

Question 28

what is endopthalmitis

Answer 28

inflammation of the vitreous and aqueous humour, usually caused by infection. It is characterized by progressive vitritis. staph epidermidis is common

Question 29

main prevention of endopthalmitis

Answer 29

povidone-iodine 5% antiseptic prophylatic ABx

Question 30

features of endopthalmitis

Answer 30

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

Question 31

Mx of infective endophthalmitis

Answer 31

Intravitreal antibiotics ie ceftazidime - gram negative and vancomycin - coagulase negative or pars plana vitrectomy. In acute endophthalmitis, the Early Vitrectomy Study Group found that early vitrectomy is only beneficial in patients with light perception-only vision

Question 32

what is acute endophthalmitis

Answer 32

● Usually occurs within the first week of surgery. ● This is due to the patient’s own periocular flora. The main causative organism is Staphylococcus epidermidis. Most common source: bacteria from patient’s lids/conjunctiva

Question 33

what is delayed endopthalmitis | features

Answer 33

● Onset varies from 6 weeks to several months. ● Main causative organism is Propionibacterium acnes. • Indolent uveitis/vitritis • White capsular plaque, painless

Question 34

other causes of endophthalmitis

Answer 34

● Post-trauma: Staphylococcus or Bacillus cereus (has the worst prognosis). ● Fungal (Candida): Occurs in immunocompromised patients. Most common cause of endogenous endophthalmitis.

Question 35

most common complication of late cataract surgery

Answer 35

posterior capsular opacification

Question 36

what is posterior capsular opacification

Answer 36

The posterior capsule opacifies due to posterior migration of lens epithelial cells.

Question 37

features of posterior capsular opacification

Answer 37

● Gradual loss of vision and glare; patients often think their cataracts have recurred. - capsular fibrosis ● Elschnig pearls: Grape-like collection of swollen lens epithelial cells - proliferation of epithelial cells in the posterior capsule which usually has none ● Sommering rings: White annular proliferation of residual cells.

Question 38

Mx of posterior capsular opacification

Answer 38

Capsulotomy with Nd:YAG laser.

Question 39

secondary causes of congenital cataracts

Answer 39

galactosaemia lowe syndrome fabry disease mannosidosis down TORCH

Question 40

what is galactosaemia features Ix Mx

Answer 40

- AR condition due to absence of galactose-1-phosphate uridyltransferase. - Features: Infant presenting with liver dysfunction, failure to thrive and oil-droplet cataract. Investigation: Stool for reducing substances. Management: Dietary restriction of lactose and galactose.

Question 41

what is lowe syndrome

Answer 41

XLR condition due to an abnormality in amino acid metabolism. Features: Seizures, cataracts, posterior lenticonus and congenital glaucoma.

Question 42

what is fabry disease

Answer 42

XL lysosomal storage disorder periodic burning pain in extremities, telangectasias Spoke-shaped posterior cataracts and corneal verticillata.

Question 43

what is mannosidosis inheritance feature

Answer 43

AR condition due to deficiency in alpha mannosidase. Spoke-shaped posterior cataracts.

Question 44

features of down syndrome

Answer 44

Single palmar crease, low set ears, large tongue, epicanthal folds and blue dot cataract.

Question 45

what is TORCH

Answer 45

Toxoplasmosis, other (VZV, syphilis, parvovirus B19), rubella, CMV, HSV.

Question 46

Mx of congenital cataracts

Answer 46

● Observation, for small, <3 mm diameter, partial dense cataracts. ● In unilateral cases, part-time occlusion or pharmacological mydriasis of the good eye can be helpful to avoid amblyopia. These interventions are useful in delaying the need for cataract surgery until the eye growth becomes stable. ● Surgery: Involves pars plana lensectomy, posterior capsule capsulorhexis and anterior vitrectomy where appropriate. In addition to correction of refractive errors. ● A bilateral dense cataract requires surgical treatment within 8–10 weeks. ● A unilateral dense cataract requires surgical treatment within 6 weeks due to a higher risk of amblyopia.

Question 47

postop complications of congential cataracts

Answer 47

1. Posterior Capsular Opacification: A dangerous complication, as it can lead to amblyopia. 2. Secondary glaucoma: Open-angle glaucoma can occur years after surgery. Angle closure may occur immediately postop. Incidence is higher if surgical treatment was performed within the first month of life. 3. Endophthalmitis. 4. Retinal detachment.

Question 48

what is anterior lenticonus

Answer 48

Bilateral thinning of the anterior capsule with anterior lens protrusion into the anterior chamber. - Alport syndrome (type IV collagen mutation disorder). - AD - sensorineural deafness and renal disease

Question 49

what is posterior lenticonus

Answer 49

Deformity in the posterior surface of the lens that is usually unilateral. Associated with congenital cataract. Associated with Lowe syndrome.

Question 50

what is ectopia lentis

Answer 50

dislocation/displacement of the lens from its normal position. The most common cause is trauma

Question 51

ocular causes of ectopia lentia

Answer 51

``` ● Simple (familial) ectopia lentis Occurs congenitally or later in life Inheritance: AD or AR Bilateral symmetric lens dislocation superotemporally ● Pseudoexfoliation syndrome ● Hypermature cataracts ● High myopia ```

Question 52

systemic causes of ectopia lentis

Answer 52

marfan homocystinuria

Question 53

marfan syndrome causing ectopia lentis

Answer 53

● Most common inherited cause of ectopia lentis. ● Inheritance: AD due to mutations of fibrillin-1 gene on chromosome 15 (FBN1 gene). ● Bilateral superotemporal lens dislocation is typical. Accommodation is not affected because ZONULES ARE NOT BROKEN ● Systemic features - Tall stature, typically with dolichostenomelia (unusually long limbs) - Mitral prolapse, aortic aneurysm, regurgitation and dissection - Kyphoscoliosis

Question 54

homocystinuria causing ectopia lentis

Answer 54

● The second most common inherited cause of ectopia lentis. ● Inheritance: AR due to cystathionine beta-synthase deficiency. ● Bilateral inferonasal lens dislocation is typical. - ZONULES BROKEN Skeletal abnormalities, mental disability, risk of thrombotic complications (especially with anaesthesia) ● Systemic features - Coarse blond hair - Malar flush - Blue irides - Intellectual disability • Treatment of homocystinuria: low methionine, high cysteine diet

Question 55

nuclear sclerotic cataract is assessed by

Answer 55

oblique slit-lamp biomicroscopy and not by retroillumination

Question 56

secondary cataracts - cataracts that develope as a result of some other primary ocular disease

Answer 56

anterior uveiits acute agnle closure glaucoma hereditary fundus dystrophies

Question 57

drugs associated with cataracts

Answer 57

* Steroids * Chropromazine • Gold * Amiodarone * Busulphan * Allopurinol

Question 58

anaesthetic options

Answer 58

sub-tenon block - 5mm from limbus into subtenon space - akinesia is variable peribulbar block - akinesia and anaesthesia good but perforation of eyeball is risky topical anaesthesia - absent akinesia

Question 59

signs of ruptured posterior lens capsule

Answer 59

sudden shallowing of AC

Question 60

presentation of delayed onset postop endophthalmitis

Answer 60

painless visiual deterioration ass w floaters | mutton fat keratic precipitates

Question 61

anterior stellate cataract

Answer 61

phenothiazine, amiodarone

Question 62

RFs of cataracts

Answer 62

UV exposure, smoking, sugar level, steroid use

Question 63

Mx of delayed endophthalmitis

Answer 63

• Difficult eradication (intracameral vancomycin),may require Intraocular lens explant & Capsulectomy (to get rid of the plaque)

Question 64

metabolic causes of ectopia lentis

Answer 64

• Abnormal elastin (Marfan’s) • Metabolism: Homocysteinuria, Sulfite oxidase, hyperlysinaemia)

Question 65

genetic causes of ectopia lentis

Answer 65

• Weil-Marchesani Syndrome - converse of marfan short stature, bradyactlyy, stubby fingers, ectopia lentis inferior microsphelakia - subluxation anteriorly • Pierre Robin syndrome

Question 66

``` wilson mytonic dystrophy trisomy 21 outdoor exposure posterior subcapsular cataract nuclear sclerotic anterio stellate cataract ```

Answer 66

* Wilson's disease = sunflower cataract, which is anterior sub capsular. * Myotonic dystrophy = Christmas cataract * Trisomy 21 = Cerulean Blue dot cataract * Outdoor exposure = cortical cataract * Posterior subcapsular cataract = most likely to produce symptoms of glare in bright light * Nuclerar sclerotic = myopic shift “able to read the newspaper without wearing glasses again” * Anterior stellate cataract: phenothiazine, amiodarone