What is the Difference Between Glaucoma and Cataracts?
Glaucoma & cataracts are both degenerative eye diseases that are a natural part of the aging process and can cause permanent vision loss.
Glaucoma is a group of eye diseases that damage the optic nerve (a bundle of nerve fibers connecting the retina to the brain). This damage is caused by increased intraocular pressure (IOP), or pressure inside the eye, resulting in permanent loss of peripheral vision.
A cataract is a clouding or opacity of the lens of the eye that leads to gradual painless blurring and eventual loss of vision.
Glaucoma – eye disease that damages the optic nerve, caused by increased intraocular pressure (IOP), resulting in permanent loss of peripheral vision.
First, we’ll take a look at glaucoma.
In a normally healthy eye, the clear fluid that fills the anterior chamber flows in and out to continuously nourish the nearby tissues. This fluid leaves the chamber through the trabecular meshwork, which is like a drain where the iris & cornea meet.
In open-angle glaucoma, there is a wide & open angle between the iris & cornea. The fluid passes too slowly through the drain & there is a slow clogging of the drainage canal, resulting in increased eye pressure. It is the most common type of glaucoma & may also be called chronic or primary glaucoma.
Open-angle glaucoma (chronic / primary)
It has a wide & open angle between the iris & cornea. It is caused by a slow clogging of the drainage canal, resulting in increased eye pressure.
Angle-closure glaucoma (a less common form) has a narrow or closed angle between the iris & cornea. It is caused by the quickly developing blockage of drainage canals, resulting in a sudden rise in intraocular pressure. This leads to severe pain, nausea, redness, & blurred vision. The symptoms & damage of this type are usually very noticeable, demanding immediate medical attention.
Angle-closure glaucoma (acute/narrow-angle)
- It has a narrow or closed angle between the iris & cornea
- Caused by the quick blockage of drainage canals, resulting in a sudden rise in intraocular pressure
- Symptoms are severe pain, nausea, redness, & blurred vision
- Demands immediate medical attention
Other less common forms of glaucoma include secondary glaucoma (which can be open-angle or angle-closure) and congenital glaucoma.
Secondary glaucoma refers to glaucoma in which there is an identifiable cause of increased eye pressure, such as eye injury, inflammation, certain drugs (steroids), & advanced cases of cataracts or diabetes. Treatment usually includes medications, laser surgery, or conventional surgery.
Congenital glaucoma occurs in babies when there is an abnormal development of the eye’s drainage canals during the prenatal period. It is rare, may be inherited, and can often be corrected with microsurgery or treated with medication & surgery.
General signs & symptoms of glaucoma include the following.
Open-angle glaucoma:
-No S/S in the early stages
-Slow, progressive loss of peripheral vision
-Tunnel vision
-Persistent, dull brow pain
-Difficulty adjusting to darkness
-Failure to detect color changes
S/S of closed-angle glaucoma:
-Severe eye pain causing N/V
-Decreased/blurred vision
-Halos around lights
-Conjunctiva red & cornea hazy
-Permanent blindness if IOP too high for 24-48 hrs
S/S of congenital glaucoma:
Enlarged eyes
Cloudy cornea
Light sensitivity
Excessive tearing
Glaucoma is diagnosed using several painless tests in a comprehensive dilated eye exam.
Tonometry: measures the pressure in the eye.
Ophthalmoscopy: illuminates & magnifies the back of the eye.
Gonioscopy: uses a special mirrored magnifying lens to examine the drainage channels for proper fluid outflow.
Visual field test: used to measure any loss of peripheral vision.
With early detection & treatment, glaucoma can almost always be controlled & vision preserved. However, once vision has been lost it cannot be restored.
Treatment is concentrated on lowering the pressure inside the eye to prevent damage to the optic nerve. This is most commonly accomplished with the use of eye drops or oral medications – some working to reduce the production of fluid in the eye & others allowing for faster drainage of fluid from the eye.
Another treatment option is laser trabeculoplasty, in which a laser is used to create holes in the meshwork of the drainage canal to allow the fluid to drain easier.
If these methods fail to decrease fluid pressure, conventional surgery (trabeculectomy) is required to create a new drainage area so the fluid can accumulate & drain into the vascular system.
Treatment of glaucoma is usually a lifelong process, requiring frequent monitoring & constant treatment.
Nursing tips for the patient with glaucoma:
Eye drops must be used regularly & consistently – if stopped, pressure in eyes will increase to damaging levels.
Someone with glaucoma should generally be examined every 3-4 months for the rest of their lives, since there is no way to determine if the glaucoma is under control based on how they feel or their vision.
With glaucoma as the second leading cause of blindness in the US, cataracts are the number one leading cause of preventable blindness.
A cataract is a clouding of the lens that leads to gradual painless blurring & eventual loss of vision.
Cataracts are generally classified as:
senile - associated with aging
congenital - present at birth
traumatic - associated with injury
secondary - occur after other eye or systemic diseases
Cataract – clouding of the lens that leads to gradual painless blurring & eventual loss of vision.
Risk factors for cataracts include:
Age (increases dramatically after age 65)
Prolonged exposure to sunlight
High-dose radiation exposure
Poorly controlled diabetes
Smoking
Trauma to the eye
Drug effects from corticosteroids, phenothiazines, & some chemo drugs
Signs & symptoms of cataracts:
Gradual blurring & decrease of vision
Glare at night when driving
Faded colors
Halos around light
Cloudy, white opacity behind pupil
Sometimes vision improves when the pupil dilates at night
Cataracts are diagnosed by direct inspection of the lens with an ophthalmoscope after pupil dilation.
Surgery is the definitive treatment for cataracts, with a success rate of 90-95%. Cataracts are removed when the visual impairment interferes with daily activities, and is done as an outpatient surgery with the use of local anesthetic. 90% of patients achieve a corrected vision near 20/20 after surgery.
Phacoemulsification is the most widely used cataract surgery in the developed world, in which ultrasonic energy is used to emulsify the cataract lens. Then a new plastic lens is inserted.
Another method of cataract removal is extracapsular cataract extraction in which the lens & anterior capsule are removed and an intraocular lens is implanted behind the pupil & iris.
Cataract surgery using phacoemulsification – the most widely used in the developed world – ultrasonic energy is used to emulsify the cataract lens
Nursing tips for a patient with cataracts:
Prevent cataracts by wearing sunglasses & not smoking.
Prior to cataract surgery, give structured preoperative teaching & ensure the patient has someone to transport the patient home.
The patient will wear a protective dressing home, then an eye shield will be worn for 2-3 weeks at night to avoid accidental bumping or pressure during sleep.
In most cases, the patient’s life has been changed for the better because of improved vision.
REVIEW
Let’s go over a review of glaucoma & cataracts side by side.
Glaucoma is caused by a blockage of the drainage canals in the eye, which leads to increased intraocular pressure causing damage to the optic nerve.
There is a permanent loss of peripheral vision, as well as pain & halos around lights with closed angle glaucoma.
It is treated with eye drops, oral meds, laser surgery, or conventional surgery to reduce pressure in the eye.
A cataract, on the other hand, is a clouding of the lens, in which vision gradually gets blurry & leads to a loss of vision. There is usually a glare or halo seen around lights.
It is treated with surgical removal of the cataract lens & a new lens is inserted into the eye.
Ultimately, the progression of glaucoma can be slowed or stopped if treated early; and cataracts can easily be removed with surgery.