What is the difference between glaucoma and cataract?

What is the difference between glaucoma and cataract?

In the article below, we will try to clarify common misconceptions of the two eye diseases that are frequently mixed up. what is the difference and what are differences between them? And can a cataract cause glaucoma and vice versa?


Cataracts are opacities forming within the eye’s clear crystalline lens. These opacities usually occur due to changes in the lens proteins where they become less soluble and clump together. This in turn leads to decreased light entering the eye and changes in the refraction of light onto the retina. This causes distortion of vision, and decreased clarity and acuity. The retina turns the light impulses into electrical signals that go through the optic nerve and to the brain. Cataracts usually develop over a long period of time and it may take years for a person to become symptomatic.  It usually affects both eyes although unequally, and affects elderly persons.


This is a blinding disease in which the pressure inside the eye is higher than the normal range. Eye pressure is meticulously controlled through various mechanisms. When these become diseased this leads to an increase in pressure, a grave condition, which ultimately causes atrophy of the retina and the optic nerve, resulting in gradual loss of visual field and finally permanent blindness.

The most common form of glaucoma unfortunately has no warning signs or symptoms and is usually diagnosed during a visit to your eye doctor or ophthalmologist, this is why regular routine  eye exams are very important. If this form of glaucoma is not diagnosed and treated at an early stage  can silently affect the patient’s peripheral vision, gradually encroaching onto the central vision and ultimately blindness. 

What are the signs and symptoms for both illnesses ?

What are the symptoms for glaucoma ?

Signs for  common or open angle glaucoma are usually scarce and the disease silently progresses.  

For the second and less common form of glaucoma called closed angle glaucoma  signs are severe and include:

  1. Severe eye pain
  2. Severe headache
  3. Nausea and vomiting
  4. Sudden severe decrease of visual acuity and clarity
  5. Redness of the eyes

What are the symptoms for cataract?

These differ from person to person, and depend on the density and location of the cataract itself within the lens. It may start as a mild blurring of vision, but with the increased lens protein opacity symptoms worsen. The main symptoms are :

  • Frequent change in reading glasses or poor reading vision.
  • Blurred distant vision or double vision
  • Haloes around lights especially at night  
  • A feeling that the person is looking through ground glass or steam.
  • Increase short sightedness especially in the elderly population. 

Is there a relationship between the two diseases?

Cataracts can rarely cause glaucoma especially when completely ignored and severely progressed. The altered proteins pull in water from the surrounding structures into the lens leading to its swelling and closure of the angle of the eye where the normal flow of fluids occurs leading to a severe increase in eye pressure and severe glaucoma. 

Which disease is more serious?

Glaucoma is definitely more serious because the elevated eye pressure leads to permanent damage and atrophy of the optic nerve and retina, both of which are yet irreplaceable. 

What are the proper treatment options  and management lines ?

Glaucoma: there are many forma of glaucoma treatment options including eyedrops, laser eye surgery, and open eye surgeries. It is important to know that glaucoma treatment options can delay the loss of vision, but cannot restore already lost vision because optic nerve damage is irreversible. Treatment is case variable, meaning that some patients may need one form of treatment, while others may need more than one eye drop or more than one type of intervention. 

What is the treatment option for cataract?

The treatment method for cataract is surgical removal of the cataract and implanting an artificial lens in the eye. This can be done by microsurgical blades or by laser. 

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أستاذ طب و جراحة العيون م. طب عين شمس أستشاري جراحات تصحيح عيوب الابصار و المياه البيضاء و القرنية عضو الجمعية الامريكية لعلاج العيون و تصحيح العيون بالليزر زميل المجلس العالمي لجراحة و طب العيون زميل الكلية الملكية لطب و جراحات العيون بأنجلترا

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About the doctor

A consultant specializing in corneal, cataract and Glaucoma Surgery and Refractive surgery in Egypt, Assistant Professor of Ophthalmology – Ain Shams University, Consultant cornea, cataract, and Glaucoma Surgery and Refractive Surgery, Fellow of the Royal College of Physicians and Surgeons of Glasgow, UK.

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