A detailed view of any cataract can be obtained with the slit-lamp. By adjusting the angle and size of the slit beam, various optical sections of the lens can be examined, revealing the exact morphology of the cataract. The presence of small vesicles under the anterior lens capsule can be seen as an early sign of senile cataract. Cataracts secondary to uveitis or to drugs might first appear as an opacity in the posterior subcapsular region. For optical reasons, an opacity in this region tends to interfere with reading vision at an early stage. Opacities in the lens can appear in a wide range of curious shapes and sizes, and earlier in the last century there was a vogue for classifying them with Latin names, which are now largely forgotten. Such a classification is of some help in deciding the cause of the cataract, although it can sometimes be misleading. Congenital cataracts are usually quite easily identified by their morphology, as are some traumatic cataracts. When a unilateral cataract appears many years after a mild contusion injury, it can be difficult to distinguish this from an age-related one.
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