Glaucoma is essentially a group of diseases characterized by optic neuropathy with corresponding visual field defects, and elevated intraocular pressure is one of the primary risk factors. Many patients with this type of glaucoma have no obvious symptoms, which is why glaucoma is also known as the “invisible vision killer”. So how do we detect this hidden killer early? Glaucoma is characterized by irreversible damage to the retinal nerve fiber layer and ganglion cells, which is the primary site of glaucoma damage, therefore, evaluation of the retinal nerve fiber layer is critical. Evaluation of the retinal nerve fiber layer is even more relevant for the early diagnosis of glaucoma because some clinical studies have shown that changes in the retinal nerve fiber layer can precede the appearance of visual impairment. For example, one investigator found through pathological studies that more than 50% of the retinal nerve fiber layer was already damaged by the time visual field damage was detected, while another study showed that a review of fundus photographs of patients presenting with visual field defects revealed that 60% of patients had a nerve fiber layer defect 6 years before the onset of visual field defects. This shows that one of the key points in the early diagnosis of glaucoma is the assessment of nerve fiber layer thickness. There are four common clinical methods of assessment: fundus stereophotography, GDx, HRT, and OCT, and it is not necessary to get too hung up on what these obscure letter combinations mean, just know that they are methods of measuring retinal nerve fiber layer thickness using different optical techniques. Fundus stereophotography is the traditional method, but it requires an experienced glaucoma surgeon for evaluation, has subjective influences, and has a lot of optic disc variability, which can sometimes be difficult to assess. The other three are objective assessments, but each method has the problem of measurement error due to technical limitations. One of the new generation of frequency-domain OCT techniques is currently considered to be the most accurate technique for measurement. The observation and evaluation of the anterior segment structure is also particularly important in the early diagnosis of closed-angle glaucoma. How is the early diagnosis of glaucoma achieved? You may find what is described above, strange and difficult to understand. It’s okay, the tests and diagnosis are done by your doctor. All you need to do is attend your regular physical exam (including eye exams) and if you find any suspicious problems, your examiner will recommend a specialized eye exam; or you can go directly to the ophthalmology department and have a routine eye exam. This will allow you to detect glaucoma at an early stage, as we have powerful screening tools and knowledgeable skills to help you. If you are now older than 40 years old, have a family history of glaucoma, are highly myopic or farsighted, or have diabetes, you should be especially careful and need annual eye exams.