Vision is one of our most cherished senses, and maintaining eye health is undeniably crucial. Amongst the myriad of eye conditions that can threaten our vision, glaucoma and cataracts stand out as two of the most common and potentially debilitating.
Glaucoma and cataracts are significant public health concerns in Singapore, each affecting a substantial portion of the population, especially the elderly. Approximately 3% of people over the age of 50 in Singapore have glaucoma, with this percentage rising to nearly 10% for those over 70 [1]. More concerning is that most glaucoma sufferers are often unaware of their condition, as early glaucoma usually does not have symptoms, earning it the moniker “the silent thief of sight.” Cataracts are even more prevalent, with data showing that nearly 95% of people over the age of 70 are affected [2].
Glaucoma is associated with damage to the eye nerve and is often (but not always) associated with increased eye pressure. It progresses slowly and is usually asymptomatic until significant vision loss occurs. On the other hand, cataracts involve clouding of the eye’s natural lens, which results in a gradual decline in vision that can make everyday activities increasingly challenging.
Understanding the differences between glaucoma and cataracts is crucial for patients and healthcare providers alike. In the following sections, we will delve deeper into the causes, symptoms, diagnosis, and treatment options for both glaucoma and cataracts and provide a comprehensive guide to managing these vision-threatening conditions.
Glaucoma is a group of eye diseases characterised by damage to the eye nerve, which is crucial for transmitting visual information from the eye to the brain. The primary cause of this damage is usually elevated eye pressure, although glaucoma can occur even with normal eye pressure levels. The most common form of glaucoma is primary open-angle glaucoma, where the drainage canals in the eye become clogged over time, which causes increased eye pressure. Another form of glaucoma, angle-closure glaucoma, occurs when the iris blocks the drainage angle completely and causes an increase in eye pressure. The increase in eye pressure is usually gradual, but rarely, the eye pressure in angle-closure glaucoma can increase rapidly and suddenly.
The symptoms of glaucoma can vary significantly depending on the type and stage of the disease. In its early stages, primary open-angle glaucoma and primary angle-closure glaucoma typically have no symptoms, hence regular eye exams are essential for early detection. As the disease progresses, patients may notice peripheral vision loss, which can deteriorate to tunnel vision and, eventually, total irreversible blindness if untreated. Rarely, when the eye pressure in angle-closure glaucoma increases suddenly and rapidly, patients can present with symptoms such as severe eye pain, nausea, vomiting, blurred vision, and halos around lights. This is a medical emergency that requires immediate attention.
The exact causes of glaucoma are not entirely understood, but several risk factors have been identified, including age (people over 60 are at higher risk) [3], family history [4], ethnicity (higher prevalence amongst African Americans, Asians, and Hispanics) [5], and certain medical conditions such as diabetes [6] and hypertension [7]. Other risk factors include prolonged use of corticosteroid medications [8], severe eye injuries, and thinner corneas (the transparent structure located at the front of the eye).
Cataracts are a common eye condition characterised by the clouding of the eye’s natural lens, which lies behind the iris and the pupil. This clouding can result in a decrease in vision, as the lens becomes less transparent, scattering and blocking light as it enters the eye. Cataracts develop gradually and can affect one or both eyes. They are the leading cause of blindness [9] worldwide and are primarily associated with ageing. In Singapore, 80% of people have cataracts by the age of 60 years[10].
The primary symptoms of cataracts include blurry vision, difficulty seeing at night, sensitivity to light and glare, seeing halos around lights, fading or yellowing of colours, and double vision in a single eye. These symptoms can significantly impact daily activities such as reading, driving, and recognising faces, reducing the overall quality of life. Initially, stronger lighting and eyeglasses can help deal with the vision problems caused by cataracts, but as the condition progresses, surgical intervention becomes necessary.
Cataracts are primarily caused by ageing [11], as proteins in the lens break down and clump together, forming cloudy areas. Other factors contributing to the development of cataracts include diabetes [12], smoking [13], excessive alcohol consumption [14], prolonged exposure to ultraviolet sunlight [15], and the use of certain medications like corticosteroids [16]. Eye injuries, radiation therapy, and genetic predisposition can also increase the risk of developing cataracts.
We have highlighted some differences between glaucoma and cataracts in the table below:
| Symptom/Sign | Glaucoma | Cataracts |
| Vision Changes | Gradual loss of peripheral vision, which may not be noticeable in the early stages | Cloudy or blurry vision |
| Noticeable Symptoms | Often asymptomatic until the glaucoma is advanced | Blurry vision, difficulty seeing at nightsensitivity to light and glare, seeing halos around lights, fading or yellowing of colours, and double vision in a single eye |
| Advanced Stages | Loss of central vision | Loss of central vision |
A comprehensive examination by an ophthalmologist is crucial for a definitive diagnosis, allowing timely intervention to prevent severe vision loss.
Most of the time, cataracts do not directly cause glaucoma, but there are instances where they can be associated with each other. It is not uncommon for elderly persons to have both cataracts and glaucoma. In certain situations, cataracts can exacerbate glaucoma. For example, very advanced cataracts can block the eye’s drainage system, resulting in increased eye pressure [17] and angle closure glaucoma. In addition, some types of glaucoma, such as secondary glaucoma, can result from conditions that might also cause cataracts, such as eye inflammation or trauma [18].
Moreover, the treatment of one condition can sometimes impact the other. For instance, cataract surgery can sometimes help lower eye pressure in glaucoma patients [19], which potentially reduces their need for glaucoma medications. Conversely, glaucoma surgery might exacerbate the development of a cataract [20].
While cataracts are usually a reversible cause of poor vision, glaucoma is generally considered more serious as damage to the eye nerve is irreversible, and this results in irreversible vision loss if left untreated. The vision loss from glaucoma is typically gradual and asymptomatic in the early stages, which makes regular eye examinations crucial for early detection and management. Once vision is lost due to glaucoma, it cannot be restored.
In contrast, while cataracts significantly impact one’s quality of life, they are typically treatable with surgery. Cataract surgery, which involves removing the cloudy lens and replacing it with an artificial one, is highly successful in restoring vision. Unlike glaucoma, the vision impairment caused by cataracts can be effectively reversed through surgical intervention.
Yes, it is possible to develop glaucoma after cataract surgery. Cataract surgery can lower eye pressure and benefit glaucoma patients, but there are also instances where it can contribute to the development or exacerbation of glaucoma.
Yes, glaucoma can cause sudden blindness, particularly in the case of acute angle-closure glaucoma [24]. This type of glaucoma occurs when the drainage angle of the eye becomes suddenly blocked, which results in a rapid increase in eye pressure. This condition is a medical emergency and can result in total blindness within a matter of days if not treated immediately. Symptoms of an acute angle-closure glaucoma attack include severe eye pain, headache, nausea, vomiting, blurred vision, and seeing halos around lights.
Open-angle glaucoma, the more common form of glaucoma worldwide, usually progresses more slowly and does not typically cause sudden blindness. However, without treatment, it can still lead to significant and irreversible vision loss over time.
Early detection is crucial for managing both glaucoma and cataracts effectively. Regular eye examinations can help identify these conditions in their initial stages, which can help ensure timely intervention and prevent severe vision loss. For glaucoma, early detection is vital as the disease often progresses without noticeable symptoms. Regular screening, especially for those at higher risk—such as individuals over 60, those with a family history of glaucoma, and certain ethnic groups—can help catch the disease before significant damage occurs.
Similarly, cataracts develop gradually, and early detection through comprehensive eye examinations can help manage symptoms and determine the appropriate time for surgery. Identifying cataracts early allows patients to make lifestyle adjustments and consider surgical options before their vision significantly impacts daily activities. Here are the treatment options for both conditions:
For patients with both glaucoma and cataracts, managing these conditions requires careful consideration. When a glaucoma patient requires cataract surgery, there are typically two options: performing cataract surgery alone or combining it with glaucoma surgery.
Glaucoma and cataracts are both common causes of vision loss. Glaucoma, often called the “silent thief of sight,” can lead to irreversible vision loss if not detected and managed early. Cataracts, while also detrimental to vision, are easily treated with vision-restoring cataract surgery. The solution to these eye health issues lies in proactive and early detection.
For patients dealing with both conditions, integrated treatment plans are essential. Options include standalone cataract surgery or combined procedures that address both glaucoma and cataracts simultaneously, tailored to the patient's specific needs.
Prioritising eye health through regular check-ups and being aware of the symptoms of these conditions can prevent severe vision loss and help maintain a good quality of life. By taking proactive steps and seeking timely medical advice, individuals can effectively manage and treat glaucoma and cataract.
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