Glaucoma vs cataracts: What’s the difference?

Glaucoma and cataracts are both common degenerative eye conditions and potential causes of blindness. Both conditions can be age related and eventually lead to reduction in sight, which is why they often get confused. While both conditions do share some similarities, they are not the same. This article will outline the main differences between glaucoma and cataracts, define the two conditions and explain their symptoms and causes as well as treatment options.

What is glaucoma?

Glaucoma is a common eye condition which involves damage to the optic nerve that connects the eye to the brain. It typically affects older adults aged 70 and over, but you can get glaucoma at any age. Glaucoma is usually caused by fluid build-up at the front of your eye. It can be hereditary and more likely to develop in people who have a parent or sibling with the condition.

Cross-section diagram of the eye with labelled components

“With early diagnosis and effective management, the vast majority of glaucoma blindness can be prevented.” explains Mr Saurabh Goyal, consultant ophthalmologist and cataract and glaucoma specialist.

There are various types of glaucoma, including:

• primary open angle glaucoma: the most common type, which develops gradually and is caused by blockage of your eye’s drainage channels
• acute angle closure glaucoma: a less common type that is caused by a sudden blockage in the angle or the door of the eye blocking the drainage channels, causing pressure in the eye to rise rapidly
• secondary glaucoma: which is caused by an underlying condition like uveitis (eye inflammation), diabetes, surgery, steroids etc
• congenital glaucoma: also known as childhood glaucoma, which is a rare type that occurs in young children due to an abnormality.

What is a cataract?

Cataracts are a common condition which impairs vision. They are cloudy patches which develop on the lens of your eye. Cataracts cause blurred or fuzzy vision, and typically affect older people. They develop when clumps of protein form on the lens, becoming bigger over time.

The condition can develop in one or both eyes, but a person can’t have more than one cataract per eye.

Symptoms of cataracts and glaucoma

Glaucoma in early stages can be totally without any symptoms. However, both cataracts and glaucoma can exhibit several similar symptoms – such as blurred vision, halos around lights and reduced night vision – but, there are a few differences.

With open angle glaucoma, you may notice blind spots or patches, as the condition affects your peripheral vision. This develops slowly, and one may lose up to 80-90% of vision before the patient notices any significant problem. This vision loss is irreversible, but it can be prevented by early diagnosis and effective management. While with cataracts, people tend to experience blurry or cloudy vision and there may be glare at night.

In closed angle glaucoma the eye may be painful. It can cause intense eye pain, headache, nausea/vomiting, and your eye may appear red and feel firm. One of the common symptoms of early stage closed angle glaucoma is halos around light at night. In most cases however there are no symptoms and the condition is picked up at routine screening at the optometrists.

Glaucoma vs cataracts: What’s the difference?

One of the key differences between glaucoma and cataracts is how they affect the eye. The two conditions affect two different areas of the eye. Glaucoma involves eye pressure due to a fluid build-up in the eye, causing damage to the optic nerve at the back of the eye. Cataracts involve protein clumps forming on the lens, located at the front of the eye.

Another significant difference is that vision loss due to cataracts can be reversed with surgery but cannot be reversed in glaucoma patients. Glaucoma is typically treated with medicated eye drops, laser surgery or microsurgical techniques such as a trabeculectomy, whereas cataracts can be treated with cataract surgery.

Are cataracts and glaucoma related?

Cataracts and glaucoma are not usually directly related, but it is possible that one condition can lead to the other. A cataract may become large enough to block the eye’s drainage channels, leading to fluid build-up and increased pressure that causes glaucoma. There is also the chance that cataracts could form after you have glaucoma surgery.

Can you have glaucoma and cataracts at the same time?

You could have glaucoma and cataracts at the same time, and one may lead to another. This can be treated with surgery, and removal of the cataract can unblock the drainage channel, easing the pressure on your eye’s optic nerve.

There is also the possibility that glaucoma surgery accelerates the growth of a cataract. In these cases, research suggests that it may be beneficial to wait one or two years following glaucoma surgery to have cataract removal surgery, giving your eye time to stabilise before the cataract removal. Another approach is to do cataract surgery first on its own or combined with glaucoma surgery eg endoscopic cyclophotocoagulation (ECP), laser or microstent. There are many newer, minimally invasive surgery techniques that are now available for treatment of glaucoma as well.

Treatment for glaucoma and cataracts

The best treatment for each condition will depend on the severity of the condition. Cataract treatment is usually surgery. A change in your glasses or contact prescription may help to clear your vision, but if this has proven unsuccessful and cataracts are affecting your quality of life, then eventually surgery will be required.

Cataract treatment

Cataract surgery involves removing the clouded lens and replacing it with an artificial lens.

Typically, this is done by phacoemulsification surgery, using ultrasound energy to emulsify the nucleus of the lens before it is replaced by an intraocular lens implant. Cataract surgery is normally performed as day surgery under local anaesthetic.

“Cataract surgery is a life changing operation that can help improve the quality of vision and life.” adds Mr Goyal. There are several choices for lens implants including:

• monofocal lenses: also known as standard lenses, they only focus for distance, near or intermediate vision
• extended depth of focus lenses: these are more modern lenses that can give distance, intermediate and some near vision without compromising on the contrast sensitivity
• multifocal lenses: divide the light to focus on distance, intermediate and near vision. These are only suitable if there are no other eye problems eg dry eye, glaucoma, retinal disease etc
• toric lenses: this lens corrects the shape of the eye by customising the power of the new lens in the two different meridians to further improve the quality of vision.

Your ophthalmologist will review your medical history and perform a full examination, taking measurements of the eye to determine the suitability of the various types of lenses for you.

Glaucoma treatment

Glaucoma treatment can stop your vision from getting worse, and may include:

• prescription eye drops: to reduce the pressure in your eyes
• oral medicines: eg carbonic anhydrase inhibitors (acetazolamide)
• laser treatment: called selective laser trabeculoplasty (SLT), this treatment allows drainage channels to work better or peripheral iridotomy (PI) to unblock drainage channels in angle closure or cyclophotocoagulation to reduce fluid production in the eyes
• glaucoma surgery: to open up a new drainage channel or allow the existing channel to work better. These include trabeculectomy, aqueous shunt tube, preserflo microhunt, hydrus, ECP laser, suprachoroidal shunts etc.

St Thomas’ Hospital is a world-renowned centre of excellence for glaucoma care, with more than 20 types of glaucoma surgeries available to help treat our patients.

Get in touch with an ophthalmologist

Our private ophthalmology service is home to team of internationally renowned consultant ophthalmologists offering exceptional eye care for visual impairments, eye conditions and diseases.

To correct any vision problems, it is important to have your eyes checked regularly by specialists such as the world-renowned consultant ophthalmologists at Guy’s and St Thomas’. Rely on us for a highly professional level of care and unparalleled service. Book a consultation today on 020 7188 5197 or use the contact form.