1. UNIVERSITY OF NIGERIA NSUKKA
DEPARTMENT OF BIOCHEMISTRY
BCH 522: MEDICAL BIOCHEMISTRY I
TOPIC: CATARACT: CAUSES AND MANAGEMENT
BY
ARAZU, AMARACHUKWU VIVIAN
PG/MSc/13/65115
SUPERVISOR: DR S.O.O. EZE AND PROFESSOR B.C. NWANGUMA
2. OUTLINE
• Introduction/Definition
• Types of Cataract
• Classification of Cataract
• Symptoms of Different Types of Cataract
• Causes of Senile Cataract
• Causes of Metabolic Cataract
• Causes of Congenital Cataract
• Management of Cataract
3. INTRODUCTION/DEFINITION
Cataract is an ocular disease, characterised by an
increasing opacity in the lens resulting in visual impairment
(Kang et al., 2008).
Types of Cataract
• Nuclear sclerotic cataracts
• Cortical cataracts
• Posterior subcapsular cataracts
5. THE STRUCTUREOF THE LENS& EYE
STRUCTURE OF THE LENS AND EYE (Source: Smith,
2004).
6. Comparing a Normal to Cataract Lens
Figure 1: Normal lens versus Cataract lens.
(Source: ADAM, 2008).
7. SYMPTOMSOF CATARACT
Gradual diminution of visual clarity
Sensitivity to bright and dim light.
Double vision
Glare at night time
Constant change of glasses prescription (Krucik, 2013).
8. TYPE1: SENILECATARACT
• Commonest form of cataract; occurs mainly after the
age of 40
• Senile cataract develops over a period of years or
decades, it may result from very subtle changes in
the intraocular composition. (Antwi, 2013)
• CAUSES OF SENILE CATARACT
oAging
oElectrolyte Imbalance
oU.V Irradiation
9. AGING AS A CAUSE OF SENILE CATARCT
Increase in lens weight and volume (Delamere, 2003).
Elasticity accommodation
After the middle age (40 years), there is a decrease in the
production of ocular antioxidants and antioxidant
enzymes.
Increase in insoluble proteins at the expense of soluble
proteins.
In many cases, however, the aging process seems to be
accelerated or metabolism is deranged to the extent that there
is a widespread reduction in transparency and vision is
impaired.
10. ELECTROLYTEIMBALANCE
• The epithelial cells contain Na-K-
ATPase that maintain the osmotic
balance of the lens by regulating
the intracellular water volume
through the transportation of Na+
out of and K+ into the cell (3Na+
leaves for every 2K+ pumped in).
• With aging, there’s a loss of
Na+K+ATPase function which will
eventually result in swelling and the
distortion of the native
conformation of the crystalline form
to the aggregated form of the
proteins (Delamere and Tamiya,
2008).
FOR CATARACT FORMATION:
Failure of the Na+K+ATPase
pumps
Increased osmolarity in the
inside than the outside leading
to an influx of water to the cell
via osmosis
Cell swelling and lysing
Disruption of the crystalline
conformation
Aggregation and loss of
transparency
11. U.V. IRRADIATION
• In age= in U.V filter activity therefore without these
filters, light easily penetrates and damages cellular
components
• At the same time, the protective pigments are
chemically modified by radiation. This damages the
lens and retina on exposure to the ambient radiation
(Linetsky et al., 2014).
12. U.V. LIGHT
PROTEINS
DNA
Other cellular components
Oxidized form
of protein
ROS
Protein
aggregation
DNA Damage and
mutation
Strand Breakage
Distortion of base
pair structure
Loss of transparency
Opacity
Figure 3: U.V Action on Cataract Formation
13. Figure 4; Pathway of Cataract Formation.
(Source: Fujii et al., 2014).
Aging, U.V
Irradiation
14. TYPE2: METABOLICCATARACT
• Metabolic Cataract could be of two major types - diabetic
cataract and galactosemic cataract.
• The sorbitol pathway enzyme aldose reductase plays an
important role in the development of metabolic cataract.
• At higher concentrations of glucose, the enzyme aldose
reductase is activated. This enzyme converts glucose to
sorbitol, which accumulates within the fibres.
15. • Similarly, in galactosemia, galactose enters the lens
and is converted to dulcitol (galactitol) by aldose
reductase.
• Dulcitol also accumulates within the lens fibres,
causing an influx of water and swelling of the lens
cells and eventually opacification (Pollreisz and
Schmidt, 2010).
16. Increase in glucose concentration in the lens
Accumulation of sorbitol in the lens
Osmotic Imbalance and change in refractive index
disruption of fibre cells and loss of protein
solubility
Cell damage, protein aggregation
Loss of transparency
Cataract formation
Fig 5: Diabetic Cataract Pathway
17. Fig 6: Glucose Metabolic Pathways in the Lens.
(Source: Delamere, 2003).
18. TYPE: CONGENITAL CATARACT
• CAUSES
Genetic factors
Mutations in distinct genes, which encode the main cytoplasmic proteins
of human lens crystalline are often a cause of congenital cataracts, that
are the leading cause of reversible blindness in childhood (Santana,
2011).
Galactosemia
Cataract is frequent in galactokinase deficient children, and prevented
by a galactose-free diet.
Infection During Pregnancy
• Congenital cataracts also can occur when, during pregnancy, the
mother develops infections such as measles, rubella, etc.
• the virus may cross the placental barrier and cause birth defects in
the developing baby.
19. MANAGEMENT OF CATARACT
The diagnosis of cataract is performed by an optometrist using slit-lamp
biomicroscopy after dilation of the eye.
The major treatment option is surgery which is usually performed after the
lens has opacified.
SURGICAL MANAGEMENT:
The Bladeless Laser Cataract Surgery-: Involves the treatment with the lens
femtosecond laser which uses a beam of laser light to create incisions on
the lens and allows for laser precision and accuracy therefore improved
surgical outcomes and the removal of the opacified lens.
Next, a refractive lens implant (Intra-ocular lens) is placed inside the eye to
improve the patient’s vision.
.
22. Precipitating Factors:
• Smoking
• Long term U.V and radioactive
exposure
• Poor nutrition
Clumping of protein in the lens Trauma to the eye
Cloudy lens obstructs light from passing the retina Lens capsule affected
Reduce light transmission
Opacity of lens and scattering of light
Visual acuity test
Slit lamp test
Blurred vision
Cloudy lens
Photophobia
Double vision
Management- vitamins,
Surgery is required when
the lens is almost
completely opaque.
FIG 8: A SUMMARY OF EVENTS IN CATARACT
symptoms
