A cataract can be the reason sharp images become blurred, bright colors become dull, or seeing at night is more difficult. It may also be why the reading glasses or bifocals that used to help you read, or do other simple tasks, no longer seem to help.
Transcript of "4.lens and cataract"
LENS AND CATARACT
ABIYE MULUGETA, MD
Addis Ababa University
Department of Ophthalmology
- Know the normal anatomy and function of the lens.
- Know the risk factors for the development of
- Know the sign and symptom of cataract.
- Identify patients with cataract and be able to refer
patients to a centre where they can undergo
definitive treatment i.e. surgery.
- Know the complications of untreated cataract.
Normal crystalline lens
is transparent, biconvex
It is derived from the surface ectoderm.
It is composed of –capsule
cortex and nucleus
It has no blood supply or nerve supply after fetal
• Lies posterior to iris and anterior to vitreous.
• Suspended in position by the zonular fiber.
• It depends on aqueous humor to meet its
metabolic requirement and carry off its wastes.
• It grows continuously throughout life.
• Measures at birth adulthood
• Equatorially 6.4mm 9mm.
• Ap 3.5mm 5mm.
• Weighs 90mg 255mg
-to maintain its own clarity.
-to refract light, the lens contributes
about 15-20 diopters of the refractive
power of the eye.
• Any congenital or acquired opacity in the lens
or lens capsule is called as cataract
1. Cataracts remain the
leading cause of blindness.
2. Age-related cataract is
responsible for 48% of
world blindness, which
represents about 18
3. Cataracts are also an
important cause of low
vision in both developed
and developing countries.
• Cataract surgery is the most frequently
performed surgical procedure
• 50% of those over 65 develop vision impairing
• 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.
• Lens is completely opaque.
• Vision reduced to just perception of light
Right eye mature cataract, with obvious
white opacity at the centre of pupil
• This may take any of two forms:
• Cortex undergoes auto-lytic liquefaction and turns uniformly
• The nucleus loses support and settles to the bottom.
• The fluid from the cortex gets absorbed
and the lens becomes shrunken.
• There may be deposition of calcific
material on the lens capsule.
• The zonules become weak, increasing
the risk of subluxation / dislocation of
• A cataract usually develops
–Causes no pain.
–Cloudiness may affect only a
small part of the lens
–People may be unaware of any
• Over time, however, as the
cataract grows larger, it:
–Clouds more the lens
–Distorts the light passing
through the lens.
• Reduced visual acuity (near
and distant object)
• Glare in sunshine or with
• Distortion of lines.
• Monocular diplopia.
• Altered colours ( white
objects appear yellowish)
• Not associated with pain,
discharge or redness of the
Symptoms of Cataracts
•Bright Colors Become Dull
•Halos Around Lights
• Reduced vision, minimum LP
• Only severe dense cataracts causing severely impaired vision
cause a white pupil.
• Good pupillary reaction
• Normal IOP
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
Postoperative care after cataract
• Steroid drops (inflammation)
• Antibiotic drops (infection)
• Very strenuous exertion (rise the pressure in the eyeball)
• Ocular trauma.
Complications of cataract surgery
• Infective endophthalmitis( infection)
• Bleeding or haemorrhage
• Uveatis( Inflammation)
• Vitreous loss
• Cystoid macula
• Retinal detachment . . .
• Occur in about 3:10000 live birth.
• 2/3 of case are bilateral
• It can cause ambylopia in infants.
Management in congenital cataract
• Bilateral congenital cataract require urgent surgery
(lensectomy and vitrectomy) and the fitting of the contact lens
to correct the aphakia
• Uniocular congenital cataract treatment remains
• Follow-up for children with congenital cataract should
continue because of the risk for developing
Complications of untreated cataract
- Subluxation and dislocation.
• Duanes clinical ophthalmology
• Albert and Jakcbeic