Age-related cataract, also known as “senile cataract”, is the most common type of cataract. It is a degenerative disease in which the lens ages and changes from clear to cloudy due to a combination of factors. The prevalence of cataracts in middle-aged and elderly people increases with age, usually starting at the age of 50. In China, the prevalence of cataracts is almost 100% in people over 80 years old. Epidemiological surveys have found that age, occupation, gender, ultraviolet light, diabetes, hypertension and nutritional status are all risk factors for age-related cataracts. Patients with this type of cataract usually develop it in both eyes, and it can be sequential and inconsistent in degree. The diagnosis of age-related cataract becomes clinically significant when some cases do affect visual function due to lens clouding.
Age-related cataracts are often classified by the earliest site of lens clouding, including cortical, nuclear, and posterior subcapsular cataracts. The symptoms also vary according to the site of clouding, among which painless progressive vision loss is the most common clinical symptom.
I. Main clinical symptoms: 1. Vision loss: This is the most common symptom of cataract. It can cause blurred vision due to the decrease of lens transparency, and when the lens clouding occurs in the pupillary area, it can cause vision loss.
2. Decreased contrast sensitivity: It refers to the decreased ability to distinguish objects under different light and dark back shadows. Contrast sensitivity loss can occur at an early stage, which is common in posterior subcapsular cataract.
3. Monocular diplopia or hyperopia: It refers to the phenomenon of “double vision” when viewing objects with one eye. It is mostly seen due to uneven clouding of the lens cortex, which is caused by the change of refractive index and inconsistent focusing of light rays when passing through.
4. Glare: The phenomenon of light scattering when looking at lights due to clouding of the lens cortex.
5. Altered color vision: The clouded lens has enhanced absorption of light located at the blue end of the spectrum, causing the patient to have decreased color sensitivity to these lights, mostly seen in nuclear cataracts.
6. Visual field defects: Cataracts with peripheral cortical spoke clouding can form wedge-shaped shadows in the retina, resulting in peripheral visual field defects.
7.Myopic drift: also called lens myopia, usually occurs after middle age or aggravated after middle age, caused by nuclear sclerosis, mostly seen in cataracts with predominantly nuclear opacities.
8. Astigmatism: Astigmatism is caused by unbalanced refractive index due to lens clouding.
When cortical cataract develops to a certain degree, the lens may increase in size, causing the anterior chamber to become shallow, and those with closed-angle glaucoma physique (i.e. patients with small eyes or shallow anterior chamber) may induce acute glaucoma attack. Sudden and obvious loss of vision, red and painful eyes, ipsilateral headache and even nausea and vomiting may occur.
When the cataract is mature and cannot be removed surgically, it can develop to the overripe stage, causing uveitis, glaucoma and even lens dislocation, and patients can have red eyes and eye pain and extreme vision loss. However, a small number of patients with lens dislocation can have sudden vision improvement.
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