Cortical Cataract Flashcards
In a cortical cataract what happens to the number of cortical fibres?
They increase
What happens as new lens fibres grow in cortical cataracts that cause opacities?
The lens fibres become iverhydrated which cause protein denaturing which causes the proteins to become opaque reducing their transparency
What is the shape of the cortical cataract opacity? And where do they arise?
They can form c shape opacities or become spoke shaped which spread from the lens periphery to the nucleus
Describe shade type opacities:
They’re at the same cortical depth as spoke opacities and they coalesce to form regions of diffuse opacities. Due to this, larger regions of the lens become opaque rather than spokes
What is the prevalence of cortical cataracts?
30% of over 45s
Will px’s that have cortical cataract be symptomatic or asymptomatic?
They are usually asymptomatic because if it’s extreme peripheral location and because they’re quite small they tend to remain hidden behind the iris
When will cortical cataracts become symptomatic?
Once there’s pupillary involvement
What are sx that px’s that have cortical cataract may get?
- blurred vision (astigmatism blur which is due to changes to the cortex fibre refractive index, irregular astigmatism can’t be amended by correction
- monocular diplopia (uncorrected astigmatism)
- glare
The severity of cortical cataract symptoms depend on what?
Depends on:
- degree to which the spoke opacities invade the pupil which depend on the shape and the size of the opacity and how much the pupil is dilated (night-more lens exposed=more issues/sx)
- pupil dilation causes a decrease of depth of focus which causes an increase of abberations and scatter
- angle between the light source and the visual axis
Which part of the eye are cortical opacities more prevalent? And why?
It’s more commonly the inferior half and the most common is the inferior nasal quadrant because there’s an increase of uv exposure to that area
How do uv rays get passed the eyes protection to cause cortical opacities?
It affects the lens by bypassing the iris and this is done if the sunlight comes from above
Describe the shading effect:
Light from above is less able to strike the lower temporal or nasal quadrants so the lower nasal will receive the most uv radiation
Where do cortical opacities begin?
In the equatorial area
Describe the relationship between uv radiation and cortical opacity in regards to differences in upper and lower asymmetry:
In counties that are closer to the equator where the sun and earth are at 90 deg, the sun is higher therefore penetrates the lower lens more.
In counties that are furthest from the equator and the sun is closer to the horizon it affects upper and lower quadrants evenly
Other than uv radiation, what else effects cortical fibres causing opacities?
Lifelong mechanical stress associated with accommodation where lens power is increased and the thickness is increased too. All the thickness occurs within the nucleus so as the nucleus hardens with age, the frictional stress between the nuclear fibres and cortical fibres causes damage to the cortical fibres which is associated with cortical opacity development
