Introduction

Blindness is a common and serious problem all around the world. Any major damage or disease that affects your eyes can result in vision impairment or total blindness, if not given timely medical attention.

Do you know another hard and often forgotten fact about vision? “It deteriorates with age”! However, life does not stop there. 

An otherwise healthy individual will lead a long life but of course dependent partially or totally on others. There comes the longstanding battle against blindness to live a full and fulfilling life.

Glaucoma and macular degeneration are among the top four leading causes of blindness in the world.¹ If you are over 60, you may be at risk of these eye problems. Glaucoma and macular degeneration can cause irreversible blindness at advanced stages.² Nevertheless, thanks to advances in technologies and next generation treatment options, you have very many options nowadays. 

Let’s dive into the article to explore more about glaucoma and macular degeneration one by one and the currently available treatment options for them.

What is glaucoma?

Glaucoma is an eye condition that damages the optic nerve because of elevated intraocular pressure (IOP). Your optic nerve plays a critical role in transmitting visual signals from eyes to brain and helps you see clearly. An injury to your optic nerve can lead to permanent vision loss if not treated promptly.³ 

What are the types of glaucoma?

Your eye constantly produces a fluid called aqueous humour in the anterior chamber of the eye (clear fluid in between lens and cornea) and also an equal amount flows out of your eye through a structure made of tiny channels called trabecular meshwork. Too much production or improper drainage of aqueous humour can cause high IOP within your eye. The rise in IOP poses a high risk for glaucoma causing tunnel vision (blurry on sides and narrowing down to the central visual field) The major types of glaucoma are:

Open-angle glaucoma

Open-angle glaucoma is the most common type and it occurs when the drainage angle of aqueous humour within the eye becomes blocked and the draining becomes less efficient over time. This causes a chronic elevation of IOP. Open-angle glaucoma can be a silent condition which progresses slowly without any symptoms in the early stages.³ 

You may not realise you have it until you experience a significant change/loss in vision and it gets worse as you age. You may notice patchy black spots in your peripheral vision first and then gradual worsening of your central vision.

Angle-closure glaucoma

Angle closure is a less common form of glaucoma but often worsens fast. This occurs when the iris (coloured part at the front of your eye) structure physically blocks the drainage angle of aqueous humour.  If you have a rapid change in vision following a sharp rise in IOP, you should get immediate medical attention. Your blurry vision can be accompanied by nausea, rainbow-coloured rings around lights, and a throbbing headache and/or eye pain.³ 

Normal-tension glaucoma

If you have normal-tension glaucoma, you will not see any differences in the IOP, but there will be progressive damage in the optic nerve.⁴ The actual cause of this type of glaucoma is still unknown.

Congenital glaucoma

Some babies are born with a malformed drainage angle which obstructs proper draining of aqueous humour.⁵ Your child’s healthcare provider may notice symptoms such as increased blinking, tears without crying or dull/cloudy eyes in newborns during regular monitoring checkups which may develop into glaucoma later on.

Risk factors 

There are no definitive causes for glaucoma. Anyone can get affected but of course, the risk increases with age. People with the following issues are at high risk of glaucoma:

• Age over 60
• Family history of glaucoma
• Diabetes 
• High blood pressure
• Previous injuries or surgery in the eye
• Prolonged use of steroids

Diagnosis

If you have symptoms that relate to glaucoma, your healthcare provider will perform the following:

• Measure and monitor intraocular pressure
• Examine the inside of your eye after dilation to check for optic nerve damage 
• Perform visual field test to identify areas of vision loss
• Measure central and peripheral corneal thickness 
• Evaluate the drainage angle in the anterior chamber of your eye

Treatment options for glaucoma

Regular eye exams are crucial to detect glaucoma early, especially if your age is over 50. Although vision loss during glaucoma is irreversible, you can have numerous treatment options, if detected early to keep the IOP under control and prevent further worsening of vision.⁶

Eye drops 

The first and foremost option to treat glaucoma is eye drops. These drops can help to reduce IOP by either improving fluid drainage or decreasing the fluid production in your eye depending on the need. 

Oral medications 

Sometimes, you need oral medications in addition to eye drops to bring down IOP to a normal range quickly and slow down the progression.

Laser therapy 

If eye drops/ oral medications did not effectively reduce IOP, your ophthalmologists may suggest laser-based procedures. Laser trabeculoplasty, if you have open-angle glaucoma, during which a laser light is used to stimulate the trabecular meshwork to improve draining⁷ and laser peripheral iridotomy for closed-angle glaucoma, where a laser light is used to create a hole in your iris to facilitate draining.⁸

Surgical interventions 

If the laser fails to work, you may get recommended for surgical options:

• Trabeculectomy is a surgical procedure by removing part of the trabecular meshwork along the drainage angle to create an alternative opening in the sclera (white of your eye) to drain fluid out of the eye.⁹
• Drainage implants - A small drainage tube is inserted into the anterior chamber of your eye and a plate attached to this tube is placed outside on the sclera. This creates an alternative channel bypassing the non-functional (blocked) trabecular meshwork to drain excess fluid.¹⁰  
• Minimally invasive glaucoma surgery is a novel approach which includes a range of diverse techniques and devices aiming to reduce IOP by targeting trabecular meshwork, drainage angle and fluid outflow. The postoperative complications are less riskier than the above two and this procedure can easily be combined with other surgeries such as cataract.¹¹

Furthermore, researchers are currently exploring gene therapy (treat diseases through long-term expression or suppression of a particular gene) options to inhibit optic nerve degeneration and offer neuroprotection for glaucoma.¹²

Now, let’s look into another blinding condition known as macular degeneration in detail.

What is macular degeneration? 

Age-related macular degeneration (AMD) is an eye condition that primarily affects people over 50s as the name suggests. It affects the central part of your retina called the macula which is responsible for sharp vision. AMD progressively affects your central vision which is critical for essential activities that require detailed vision such as driving, reading, and recognising faces.¹³

What are the types of macular degeneration?

Dry macular degeneration 

The dry form of macular degeneration or dry AMD is the most common among the two types. In dry AMD, tiny yellow spots (made of protein and fat) called drusen get accumulated under the retina causing thinning of the macula and dark spots in your central vision.¹³ Thinning actually causes degeneration of photoreceptors (light-sensitive cells that convert light into neuronal signals) in the macula which makes your central vision blurry or distorted.

Wet macular degeneration 

Wet AMD is less common but can be severe and may lead to significant vision loss rapidly. In wet AMD, abnormal blood vessels grow beneath the retina which may become leaky, causing damage to the macula and the surrounding tissues.¹³ This eventually results in a sudden loss of central vision loss. 

Risk factors 

You may fall into the risky category for macular degeneration if you have the following conditions:

• age over 50s
• family history 
• smoking
• obesity
• high blood pressure
• prolonged exposure to UV light

Diagnosis 

If you have the above-mentioned symptoms in central vision, the following tests will be performed to confirm AMD:

• Monitor distortion in central vision using Amsler grid¹⁴ (a grid of straight lines with a large dot in the centre) 
• Perform a dilated eye exam to identify the drusens inside your eyes.
• Track leakage of blood vessels under your retina (for wet AMD) by injecting a dye (fluorescein angiography)¹⁵ into the vein in your arm. 
• Perform the imaging of the inside of your eye (retina and macula) using optical coherence tomography (OCT).¹⁵
• Perform imaging of blood flow inside your eye using laser light reflection and OCT scanning. 

Treatment options for macular degeneration

Currently, there is no cure for macular degeneration. Therefore, it is important not to neglect any changes in your central vision and consult with an ophthalmologist right away. The current treatment options for AMD will help to effectively delay the progression of the disease. However, the recent advancements made in the field target the molecular basis of the problem to have a long-lasting effect.

Anti-VEGF therapy 

Intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) drugs for wet AMD to control leakage of the abnormally grown blood vessels and inhibit the formation of new vessels.¹⁶

Furthermore, to prevent frequent injections, surgically implanted devices that can release the right dosage of drugs have been researched and found safe and durable. 

Photodynamic therapy (PDT)

PDT is effectively used for wet AMD, where abnormally grown blood vessels in the retina are selectively destroyed with the help of a light-sensitive drug activated by a laser.¹⁷

Gene therapy

In wet AMD, the excessive VEGF causes abnormal, leaky blood vessel formation in the retina.  Genetic modification can help to achieve a stable anti-VEGF antibody production to neutralise the excess VEGF in the retina.¹⁸

Reprogramming retinal cells

The loss of retinal pigment epithelium (RPE) is typical in dry AMD. Reprogramming RPEs has been found to reset ageing and restore youthful visual function when transplanted into patients with AMD to prevent photoreceptor loss.¹⁹

Retinal implants

Retinal implants help to reestablish the anatomical organisation of your degenerated retina. The implants can be light-responsive semiconductor materials replacing the damaged photoreceptors which will then pass on the signals to the brain through the optic nerve for processing vision.²⁰

In addition to the treatment options, regular intake of nutrient-rich food and supplements containing diverse vitamins and antioxidants may help you to slow the progression of AMD.

Summary

Both glaucoma and macular degeneration can cause irreversible blindness. If you are above 50, you require regular, detailed eye examinations as these conditions are prone among older people. Early detection is the key to effective management of the disease as both conditions have a significant impact on vision and quality of life. The available treatment options can help to preserve the remaining vision and prevent further damage.