Lens pdf - د. عزام

) ﻋﺪد اﻻوراق

(

ﻋﯿﻮن

2019

.د

ﻋﺰام

Lec: 7

Lens

Objectives:

1 To describe anatomy and physiology of the crystalline lens.

2 To discuss age-related cataract and illustrate its management

lines.

3 To compose management plans of congenital cataract.

4 To sketch a diagram of leucokoria.

5 To demonstrate cases of ectopia lentis. 6- To review a video of

cataract surgery.

Anatomy and physiology:

Anterior and posterior capsule

Lens fibres

physiology

Embryology

Age-related cataract

Definition:

Cataract is an opacity of the natural
crystalline lens. It is an extremely
common cause of visual impairment in
older patients.

Presentation and symptom:

Gradual painless decline in visual acuity.

Terminology:

• Phakia= presence of natural lens

• Pseudophakia= presence of artificial lens (IOL implantation)

 Aphakia= absence of natural and artificial lens

Classification:

Acquired cataract:

• Classification

1 According to location

2 According to maturity

Immature:

In which the lens is partially opaque.

Mature:

In which the lens is completely opaque.

Hypermature:

• Which is characterized by

shrunken and wrinkled
anterior capsule.

Morgagnian:

Is a Hypermature cataract in which the

nucleus has sunk inferiorly.

Causes and management:

Causes of presenile cataract:

1 systemic diseases.

2 systemic drugs.

3 Secondary (complicated) cataract.

Systemic diseases:

1-Diabetes mellitus

• Classic diabetic cataract is

characterized by snowflake

cortical opacities in young
diabetic.

2- Myotonic dystrophy

• Stellate posterior

subcapsular cataract.

Steroids: initially posterior
subcapsular and later the anterior
subcapsular opacities.

Chlorpromazine and amidarone:
stellate, yellowish brown granules on
anterior lens capsule within the pupillary
area.

3- Atopic dermatitis

• Dense, shield-like anterior

subcapsular plaque with
capsular wrinkling.

Systemic drugs:

Secondary (complicated) cataract:

1 Chronic anterior uveitis.

2 Acute congestive angle-closure glaucoma.

3 High (pathological) myopia.

4 Trauma.

5 Hereditary fundus dystrophies.

Complications which occur during maturation of cortical
cataract:

1 phacomorphic glaucoma: occur due to intumescences ( swollen)

lens causing blockage of anterior chamber angle.

2 phacolytic glaucoma: (secondary open angle glaucoma) it

occurs due to blockage of trabecular meshwork by
macrophages laden with protein leak through Morgagnian
hypermature cataract.

3 phacoanaphylctic (phaco-antigenic) glaucoma. 4- lens

sublaxation.

Preoperative evaluation:

1 general physical examination to rule out D.M, HTN, COPD and

any potential source of infection e.g. septic gum and UTI.

2 visual acuity and pupillary reactions.

3 Intraocular pressure (IOP).

4 retinal examination after pupillary dilatation.

5 search for local source of infection, e.g.

conjunctivitis, blepharitis, and dacryocystitis.

Biometry:

• Measurement of IOL power:

• Axial length of eye globe.

• K- readings.

• Special formulas.

Advantages of IOL implantation over spectacles:

1 No object magnification.

2 Elimination of aberration of prismatic effect.

3 Wider and better field of vision.

4 No problem in uniocular aphakia.

5 Cosmetically more acceptable.

Indications of lens extraction:

1 Grossly diminished vision hampering easy living.

2 Medical conditions:

A. diabetic retinopathy.

B. lens induced glaucoma. C- phacoanaphylaxis.

3 Cosmetic indication: to obtain black pupil.

Complications of cataract surgery:

1 Intraoperative complications.

2 Early post operative complications.

3 Late post-operative complications.

 Operative complications:

1 Vitreous loss.

2 Posterior loss of lens fragments.

3 Suprachoroidal (expulsive) haemorrhage.

 Early postoperative complications:

1 Iris prolapse.

2 Striate keratopathy.

3 Acute bacterial endophthalmitis.

 Late postoperative complications:

1  Capsular opacification.
2  Implant displacement.
3  Corneal decompensation.
4  Retinal detachment.
5  Chronic bacterial endophthalmitis.

Acute bacterial endophthalmitis:

Incidence - about 1:1,000

Common causative Organisms:

•  Staph. epidermidis
•  Staph. aureus
•  Pseudomonas sp.

Source of infection:

• Patient’s own external bacterial flora is most frequent culprit.

• Contaminated solutions and instruments.

• Environmental flora including that of surgeon and operating

room personnel.

Preoperative prophylaxis

Meticulous prepping and draping

Instillation of povidone-iodine

Postoperative injection of Antibiotics.

Sampling and injections:

Striate keratopathy:

Corneal edema and folds in
Descemets membrane.

Cause

• Damage to endothelium during

surgery.

 Make partial-thickness

sclerotomy 3 mm behind
limbus

 Insert mini vitrector.

Treatment

• Most cases resolve within a few days.

• Occasionally persistent cases may

require penetrating keratoplasty.

Corneal decompensation:

Implant displacement

Cystoid macular edema (CME):

• Fluid accumulation in outer Plexiform and inner nuclear layers

of retina with formation of cyst like changes.

Signs:

• Loss of foveal depression, thickening of the retina and multiple

Cystoid areas in the sensory retina.

• Amsler chart testing demonstrates central blurring and

distortion.

• Fluorescein angiography shows early hyperfluorescent spots due

to leakage that progress to a characteristic petaloid pattern

• OCT shows cyst like hyporeflective spaces within the retina.

Causes:

• 1- Ocular surgery and laser

• 2- Retinal vascular disease (diabetic retinopathy, retinal vein

occlusion and hypertensive retinopathy).

• 3- Inflammation: intermediate uveitis, scleritis and

toxoplasmosis.

• 4-choroidal neovascular membrane (CNV).

• 5- Systemic disease (multiple myeloma and leukemia).

Retinal detachment (RD)

Leucokoria:

Leucokoria white pupillary light reflex

Leucokoria:

Adult age group:

• Mature cataract

Paediatric age group:

1 Congenital cataract.

2 Retinoblastoma.

3 Retinopathy of prematurity

(ROP).

Causes:

1- Congenital cataract (most common)

2- Retinoblastoma (most dangerous)

3- Retinopathy of prematurity (most tragedic)

4- Toxocariasis

5-Coats disease.

6- Incontinenta pigmenta.

7- Extensive myelinated nerve fibre layer of retina.

8- Chorioretinal coloboma.

9- Persistent primary hypoplastic vitreous (PHPV).

Congenital cataract:

Congenital cataract occur in about 3 in 10 000 live births. Two third
of cases are bilateral. The most common cause is genetic mutation,
other causes include:

Chromosomal abnormalities (Down syndrome, Edward syndrome, Cri
du chat syndrome).

Metabolic disorders (Galactosaemia, Lowe syndrome, Fabry disease,
hypo- and hyperglycaemia).

Intrauterine infections (congenital rubella, toxoplasmosis,
cytomegalovirus, varicella).

Unilateral cataracts are usually sporadic, without a family history or
systemic disease and affected infants are usually full-term and
healthy.

1-Management:

• 1- ocular exam(density,

morphology, associated ocular
pathology).

Indicators of sever visual
impairment:

 Absence of central fixation.

 Nystagmus.

 Strabismus.

2- Systemic investigations:

1 Serology for intrauterine infection.

2 Urinalysis for reducing substances

after drinking milk (galactosemia

) and chromatography for amino acids
(Lowe syndrome)

3 Other investigations.

Fasting blood glucose, serum

calcium and galactokinase level.

4 Referral to paediatrician for

dysmorphic features or suspicion
of systemic
disease(chromosomal analysis).

3- Treatment:

• Unilateral dense cataract merits

urgent surgery followed by
aggressive anti-amblyopia
therapy.

• Bilateral dense cataract require

early surgery to prevent
deprivation amblyopia.

4- Visual rehabilitation:

A. spectacles.

B. contact lenses.

C. IOL implantation.

D. occlusion to treat or prevent amblyopia.

Ectopia lentis:

Acquired causes:

• 1- Trauma.

• 2-large eye.

 high myopia.

 Buphthalmos.

• 3- Anterior uveal tumour.

• 4- Hypermature cataract.

Hereditary causes:

1 familial ectopia lentis.

2 Ectopia lentis et pupillae.

3 Marfans syndrome.

4 Homocystinuria.

5 Aniridia.

Complications:

1 refractive errors (myopia and hypermetropia).

2 optical distortion due to astigmatism and/or lens edge effect.

3 lens induced glaucoma.

4 cataract.

5 endothelial damage.

Management:

• Spectacle correction for

astigmatism or aphakic correction.

• Surgical removal for cataract,

lens induced glaucoma or
endothelial touch.

Causes of cataract in unwell neonate:

Intrauterine infections:

•  Rubella.
•  Toxoplasmosis.
•  Cytomegalovirus.
•  Varicella.

Metabolic disorders:

•  Galactosaemia.
•  Hypoglycaemia.
•  Hypocalcaemia.
•  Lowe syndrome.

Post test:

Diagnosis: leucokoria

Video: cataract surgery