2. The lens
It’s crystalline.
Histology:
1. Capsule
2. Subcapsular epithelium (simple cuboidal).
• Synthesize protein for lens fiber
• Maintains a cation pump to keep the lens clear
1. Lens fibers
Cross section:
1. Capsule
2. Cortex
3. nucleus
3. Ciliary muscle
•Function:
• Constricts ciliary body
• Relaxes tension on lens
• Lens become spherical,
which increase the
refractive power
Ciliary process
•Attaches to the lenses by
suspensory ligament (zonular
fibers)
•Secrete the Aqueous humor
into the post. chamber
6. Epidemiology
1. Cataracts remain the
leading cause of blindness.
2. Age-related cataract is
responsible for 48% of
world blindness, which
represents about 18
million people
3. Cataracts are also an
important cause of low
vision in both developed
and developing countries.
7. Causes of cataract
• Old age (commonest)
• Ocular & systemic diseases
– DM
– Uveitis
– Previous ocular surgery
• Systemic medication
– Steroids
– Phenothiazines
• Trauma & intraocular foreign
bodies
• Ionizing radiation
– X-ray
– UV
• Congenital
– Part of a syndrome
– Abnormal galactose
metabolism
– Hypoglycemia
• Inherited abnormality
– Myotonic dystrophy
– Marfan’s syndrom
– Rubella
– High myopia
7
8. Any physical or chemical cause
↓
Disturbs the intracellular and extracellular equilbrium of water and
electrolytes
↓
Deranges the colloid system in lens fibres
↓
Aberrant fibres are formed from germinal epithelium of lens
↓
Epithelial cell necrosis
↓
Focal opacification of lens epithelium
(glaucomflecken)
↓
Opacification of lens
PATHOMECHANISM
9. Opacification of lens takeplace by 3 biochemical changes.
1. Hydration 2.Denaturation of 3.Slow
lens protein sclerosis
Abnormalities of lens proteins
&
Disorganisation of lens fibres
Loss of transparency of lens
Cataract
10. Cataract
Divided to :
• Acquired cataract
Age - related cataract(Senile Cataract)
Presenile cataract
Traumatic cataract
Drug induced cataract
Secondary cataract
• Congenital Cataract
Systemic association
Non-systemic association
11. Age -related cataract
It is the Most commonly occurred.
Classified according to:
Morphological Classification
• Nuclear
• Cortical
• Subcapsular
• Christmas tree – uncommon
Maturity classification
• Immature Cataract
• Mature Cataract
• Hypermature Cataract
12. Nuclear cataract
• Most common type
• Age-related
• Occur in the center of the lens.
• In its early stages, as the lens changes the
way it focuses light, patient may become
more nearsighted or even experience a
temporary improvement in reading vision.
Some people actually stop needing their
glasses.
• Unfortunately, this so-called 2nd
sight
disappears as the lens gradually turns more
densely yellow & further clouds vision.
• As the cataract progresses, the lens may
even turn brown. Advanced discoloration
can lead to difficulty distinguishing between
shades of blue & purple.
13. Cortical cataract
• Occur on the outer edge of the lens (cortex).
• Begins as whitish, wedge-shaped opacities or streaks.
• It’s slowly progresses, the streaks extend to the center and
interfere with light passing through the center of the lens.
• Problems with glare are common with this type of cataract.
14.
15. Subcapsular cataract
• Occur just under the capsule of the lens.
• Starts as a small, opaque area
• It usually forms near the back of the lens, right in the path of
light on its way to the retina.
• It’s interferes with reading vision
• Reduces vision in bright light
• Causes glare or halos around lights at night.
16. Posterior Subcapsular Cataracts
• Begins at the back of the lens (posterior pole) & spreads to the
periphery or edges of the lens.
• It can be developed when:
– Part of the eye are chronically inflamed.
– Heavy use of some medications (steroids).
• Affects vision more than other types of cataracts because the light
converges at the back of the lens.
• Anything constrict the pupils (bright light) makes it very difficult
for people with this type of cataract to see.
• Dilating drops useful in this type by keeping the pupils large and
thus allow more light into the eye.
18. Immature Cataract
Lens is partially opaque
Two morphological forms are seen:
1.Cuneiform Cataract:
– Wedge shaped opacities in the peripheral cortex and
progress towards the nucleus.
– Vision is worse in low ambient illumination when the
pupil is dilated.
1.Cupuliform Cataract:
– A disc or saucer shaped opacities beneath the posterior
capsule.
– Vision is worse in bright ambient illumination when the
pupil is constricted.
Lens appears grayish white in color.
Iris shadow can be seen on the opacity with oblique illumination.
19. Mature Cataract
• Lens is completely opaque.
• Vision reduced to just perception of light
• Iris shadow is not seen
• Lens appears pearly white
Right eye mature cataract, with obvious white
opacity at the centre of pupil
20. Hypermature Cataract
• Shrunken and wrinkled anterior capsule due to leakage of water
out of the lense.
• This may take any of two forms:
1.Liquefactive/Morgagnian Type
2.Sclerotic Cataract
21. Liquefactive/Morgagnian Type
• Cortex undergoes auto-lytic liquefaction and turns uniformly
milky white.
• The nucleus loses support and settles to the bottom.
22. Sclerotic Cataract
• The fluid from the cortex gets absorbed
and the lens becomes shrunken.
• There may be deposition of calcific
material on the lens capsule.
• Iridodonesis: Anterior chamber
deepens and iris becomes tremulous.
• The zonules become weak, increasing
the risk of subluxation / dislocation of
lens.
23. Symptoms
• A cataract usually develops
slowly, so:
–Causes no pain.
–Cloudiness may affect only a
small part of the lens
–People may be unaware of any
vision loss.
• Over time, however, as the
cataract grows larger, it:
–Clouds more the lens
–Distorts the light passing
through the lens.
–Impairs vision
• Reduced visual acuity (near
and distant object)
• Glare in sunshine or with
street/car lights.
• Distortion of lines.
• Monocular diplopia.
• Altered colours ( white
objects appear yellowish)
• Not associated with pain,
discharge or redness of the
eye
24. Signs
• Reduced acuity.
• An abnormally dim red reflex is seen when the eye is viewed
with an ophthalmoscope.
• Reduced contrast sensitivity can be measured by the
ophthalmologist.
• Only sever dense cataracts causing severely impaired vision
cause a white pupil.
• After pupils have been dilated, slit lamp examination shows
the type of cataract.
26. Treatment
• Glasses: Cataract alters the refractive power of the natural lens
so glasses may allow good vision to be maintained.
• Surgical removal: when visual acuity can't be improved with
glasses.
• Surgical techniques
– Phacoemulsification method.
– Extracapsular method.
– Intracapsular method
27. Pre-op assesments
• General health evaluation including blood pressure check
• Assessment of patients’ ability to co-operate with the
procedure and lie reasonably flat during surgery
• Instruction on eye drop instillation
• The eyes should have a normal pressure, or any pre-existing
glaucoma should be adequately controlled on medications.
• An operating microscope is needed, in order to reach the lens,
a small corneal incision is made close to the limbus for the
phaco-probe.
• It is important to appreciate anterior chamber depth and to
keep all instruments away from the corneal endothelium in the
plane of the iris.
28. Phacoemulsification in cataract surgery
involves insertion of a tiny, hollowed tip that
uses high frequency (ultrasonic) vibrations to
"break up" the eye's cloudy lens (cataract). The
same tip is used to suction out the lens
.
29.
30. Intra-capsular Cataract Extraction
Intracapsular Cataract Extraction. From the late 1800s
until the 1970s, the technique of choice for cataract
extraction was intracapsular cataract extraction
(ICCE). The entire lens (ie, nucleus, cortex, and
capsule) is removed, and fine sutures close the
incision. ICCE is infrequently performed today;
however, it is indicated when there is a need to
remove the entire lens, such as with a subluxated
cataract (ie, partially or completely dislocated lens).
31. Extra-capsular Cataract Extraction
(ECCE)
• Extracapsular Surgery. Extracapsular cataract
extraction (ECCE) achieves the intactness of
smaller incisional wounds (less trauma to the
eye) and maintenance of the posterior capsule
of the lens, reducing postoperative
complications, particularly aphakic retinal
detachment and cystoid macular edema.
32. Postoperative care after cataract
surgery
• Steroid drops (inflammation)
• Antibiotic drops (infection)
• Avoid
• Very strenuous exertion (rise the pressure in the eyeball)
• Ocular trauma.
33. Complications of cataract surgery
• Infective endophthalmitis
– Rare but can cause permanent severe reduction of vision.
– Most cases within two weeks of surgery.
– Typically patients present with a short history of a
reduction in their vision and a red painful eye.
– This is an ophthalmic emergency.
– Low grade infection with pathogen such as
Propionibacterium species can lead patients to present
several weeks after initial surgery with a refractory uveitis
• Suprachoroidal haemorrhage.
– Severe intraoperative bleeding can lead to serious and
permanent reduction in vision.
34. • Uveitis
– Postoperative inflammation is more common in certain types
of eyes for example in patients with diabetes or previous
ocular inflammatory disease.
• Ocular perforation.
• Postoperative refractive error
– Most operations aim to leave the patient emmetropic or
slightly myopic, but in rare cases biometric errors can occur
or an intraocular lens of incorrect power is used.
• Posterior capsular rupture and vitreous loss
– If the very delicate capsular bag is damaged during surgery
or the fine ligaments (zonule) suspending the lens are weak
(for example, in pseudoexfoliation syndrome), then the
vitreous gel may prolapse into the anterior chamber. This
complication may mean that an intraocular lens cannot be
inserted at the time of surgery. Patients are also at increased
risk of postoperative retinal detachment.
35. • Retinal detachment.
– This serious postoperative complication is, fortunately rare,
but is more common in myopic patients after intraoperative
complications.
• Cystoid macular oedema
– Accumulation of fluid at the macula postoperatively can
reduce the vision in the first few weeks after successful
cataract surgery. In most cases this resolves with treatment
of the post-operative inflammation.
• Glaucoma
– Persistently elevated intraocular pressure may need
treatment postoperatively.
• Posterior capsular opacification
– Scarring of the posterior part of the capsular bag, behind
the intraocular lens, occurs in up to 20% of patients. Laser
capsulotomy may be needed.
