The therapy technique known as Photodynamic Therapy for Macular Degeneration (PDT), which was first used in ophthalmology in 2000, combines a low-power, long-duration infrared laser with the photosensitive injectable medication verteporfin (Visudyne, Bausch & Lomb). 

It is used to treat neovascularization (new blood vessel growth) in the retina and choroid of the eye. Large randomized clinical studies revealed an increase in visual acuity compared to placebo when it was originally prescribed for neovascular age-related macular degeneration (AMD). The success of PDT (TAP) and Verteporfin in PDT (VIP) trials for the treatment of AMD prompted the use of photodynamic therapy in ophthalmology.

 The investigations demonstrated the effectiveness of PDT for treating AMD patients with conventional subfoveal choroidal neovascularization. It is currently commonly used as a second-line therapy for neovascular AMD since other medicines have developed. PDT has been shown to be beneficial by several published research studies and is currently most often used to treat patients with Central Serous Retinopathy (CSR).

How is Photodynamic therapy for age-related macular degeneration done?

A medication is injected into a vein in your arm by your eye doctor just before the surgery. This medication is light-sensitive. Under your macula, it accumulates in the irregular blood vessels. An eye drop anesthetic is then administered to you. The eye specialist will next point a laser into your eye while you’re wearing a specific contact lens designed for the procedure. The drug is activated by the laser’s light. Your abnormal blood vessels then develop blood clots as a result of the medication. The irregular vessels are then sealed shut by the clots and will atrophy and go away. This may lessen further eyesight loss.

When is PDT used to treat AMD?

Photodynamic therapy for wet macular degeneration is only one of several treatment types for wet AMD. Older persons who have considerable vision loss often have AMD. It rarely results in complete blindness. If you have AMD, you could still be able to see out to the sides (peripherally) since it affects your macula. Your center vision might be lost suddenly or gradually as a result. 

There are two primary kinds of AMD: dry type and wet type. There is abnormal blood vessel development exclusively in the wet type. Only the wet form of the illness is suggested as a candidate for photodynamic treatment. 

You can’t get lost eyesight back using photodynamic treatment. However, it could lessen the future damage to your center vision. 

Only a select few people with wet-type AMD have the option of photodynamic treatment. If your eyesight loss develops gradually over time as opposed to abruptly, it could be indicated. Now that there are new medications to stop irregular blood vessel formation, the therapy is utilized less often. However, your doctor could suggest treatment in addition to these new medications.

How does it work?

Information about the drug verteporfin 

With a molar mass of 718.794 g and a half-life of 5 to 6 hours, verteporfin (marketed as Visudyne), also known as a benzoporphyrin derivative, is often employed as a photosensitizer in Photodynamic Therapy. In comparison to the first-generation photosensitizer Photofrin, which had a lesser wavelength absorption (630 nm), Verteporfin had an enhanced long-wavelength absorption maximum at around 690 nm, suggesting a 50% greater increase in tissue penetration by light. It was created to treat wet AMD. Verteporfin may also be quickly eliminated from the body, reducing a patient’s photosensitivity to only one or two days. Since 1999, the USFDA has authorized verteporfin as a therapy for wet AMD after it successfully completed Phase III clinical studies. 

The Mechanism of Action of Verteporfin 

When the verteporfin is energized by the laser energy during photodynamic treatment, free radicals are released. Histamines, thromboxane, and TNF-, which are all immune-modulating substances, are locally enhanced as a result of the interaction between free radicals and blood vessel endothelial cell membranes. A range of events, such as vasoconstriction, thrombosis, increased vascular permeability, blood stasis, and hypoxia, might result from the anti-inflammatory response. When there is neovascularization, this process causes the unhealthy blood vessels to shrink. The Visudyne(6 mg/m2 dosage) is injected into the circulation and preferentially collects in the irregular blood vessels in the retina and choroid. In order to activate the phototoxic Visudyne and shut leaky blood vessels by producing these free radicals in the essential treatment locations, a low-power laser is used 15 minutes after intravenous infusion (standard dosage of 50 J/cm2, irradiance of 600 mW/cm2 of 689 nm light over 83 seconds).

PDT Trials for Macular Degeneration

Utilizing photodynamic therapy to treat AMD (TAP) 

This research, carried out in both Europe and the US, offered proof of photodynamic therapy’s potential to lessen visual acuity loss. The 402 patients with classic choroidal neovascularization (CNV) in the treatment arm (PDT) and the 207 patients in the placebo arm were participants in the TAP randomized, multi-center, double-masked, placebo-controlled studies. The proportion of eyes that lost fewer than 15 ETDRS letters from the starting position after a year was the main goal. The proportion of eyes that retained their baseline vision was greater in PDT-treated patients (12 months: 61% treated, 46% placebo; 24 months: 53% treated, 37% placebo). Some of the 2-year TAP trial participants proceeded in the 3-year TAP extension study to look at PDT’s long-term effectiveness and safety over a 5-year period. The extension research proved steady eyesight over a 60-month period and revealed no major systemic safety issues over a 5-year span. 

Verteporfin in a study for photodynamic therapy (VIP) 

339 people (average age: 75) with occult CNV lesions were included in the VIP study. Patients might possibly get 8 treatments over the trial’s two-year observation period. PDT therapy was more effective than the placebo during a 24-month period (46.2% vs 33.3%). (percentage of eyes losing less than 15 ETDRS letters). 

The VIM Trail (Ver­te­por­fin in Mi­ni­mal­ly Classic trial)

This research compared the effects of PDT therapy using full fluence (600 mW/cm2 for 83 seconds at 50 J/cm3) against half fluence (300 mW/cm2 for 83 seconds at 25 J/cm3) on lesions with minimally classic CNV. The standard treatment protocol showed no obvious vision loss over the course of the 12 and 24-month periods; each treatment had a lower risk of losing 15 letters of visual acuity compared to the 18 (47%) of 38 eyes assigned to placebo (reduced fluence group: P=0.002; standard fluence group: P=0.08). However, data from patients treated with half fluence showed better outcomes, with a higher percentage of eyes maintaining vision above the baseline (P = 0.15).

How to Prepare?

Find out what you need to do to be ready for photodynamic treatment from your eye doctor. Before the operation, find out whether you need to stop taking any medications. Additionally, find out how long you need to fast before the surgery. 

Your eye doctor may wish to inspect the back of your eye with a light shining into it using specialized equipment. For this eye test, you may need to have your eyes dilated. For even more insight into your eye, your eye doctor may request more specialized testing. 

You will be given eye drops to enlarge your pupil prior to the surgery. After the surgery, it will remain dilated for many hours.

What happens during photodynamic therapy for AMD? 

It is often carried out at an eye doctor’s office or eye clinic as an outpatient procedure. In a routine procedure: 

• The medication that is light-sensitive will be injected into you. 
• Throughout the process, you will be awake. You could be given medication to calm you down. 
• To ensure that you feel nothing, anesthetic eye drops will be administered. 
• Your eye will be fitted with a unique contact lens. This assists the laser in focusing on the precise location on the back of your eye. 
• The precise area of your eye will get the laser beam from your ophthalmologist. As a result, the light-sensitive medication will become active and start to build blood clots in the irregular blood vessels under your macula. The problematic blood vessels are then sealed up. 
• Your eye may be momentarily obscured.

What to expect after PDT

Inquire with your eye doctor about what to anticipate after your operation. You need to be able to return home that day. After the operation, arrange to have a companion accompany you home. 

Your eyes and skin will be more sensitive to light for a few days after the surgery. This is because the medication is light-sensitive. You must remain indoors and keep out of the sun throughout this period. Use protective clothes and dark sunglasses if you must go outdoors. When it is safe for you to return to the outdoors, ask your eye doctor. 

After the operation, your eye could feel a bit painful. If you plan to use over-the-counter pain medication, discuss it with your eye doctor. Follow your eye doctor’s advice on eye care and medications. 

Your eye doctor will need to closely monitor your progress. They will continue to oversee your therapy for AMD while keeping an eye out for any problems. If your eyesight is becoming worse or your eye redness, swelling, or discomfort is getting worse, call your eye doctor immediately   Following the surgery, your eyesight can be temporarily hazy, although this usually resolves quickly.

Risks of Photodynamic Therapy for Macular Degeneration

Some of the risks involved with PDT

• A blind spot may develop where the treatment is done.
• Pain at the site of injection in your back
• When exposed to direct sunlight immediately after the treatment, photosensitivity responses like sunburn may occur. 
• Reactions after receiving an injection of a light-activated medication 
• Temporary and rarely severe loss of visual clarity 
• Depending on your age, other health issues, and the precise anatomy of your AMD, your risks may change. Inquire about the dangers of the operation from your eye doctor. 

Other PDT side effects may also include:

• Dry eyes
• Irritation of eyelids
• Headache
• Nausea

Post-treatment 

Typically, patients are followed up with every 4 to 12 weeks, depending on the doctor’s discretion. Patients may often undergo fluorescence angiography testing after an initial treatment session to evaluate the effectiveness of the therapy. If required, more PDT or injectable therapy may be given.

The therapeutic benefits may not last long. This is due to the potential for irregular blood vessels to reopen.

Conclusion

Injections of anti-VEGF medications into the eye are the primary therapy for wet AMD. Typically, photodynamic treatment is not advised. Photodynamic treatment is one alternative that could be suggested, however, if anti-VEGF injections are not a possibility or are ineffective. 

Photodynamic treatment may slow the evolution of wet AMD by decreasing the development of irregular blood vessels beneath the macula. Eyes that have previously sustained damage do not have their eyesight restored. However, it could aid in halting more retinal deterioration and visual loss.

FAQ’s

What is the most effective method of treating macular degeneration? 

Early AMD has no known cure, so your ophthalmologist will likely merely do routine eye examinations to monitor your eyes’ health. Healthy eating, consistent exercise, and giving up smoking may all be beneficial. 

How long does it take for the eye to fully recover following photodynamic therapy? 

Patients who get photodynamic treatment have a greater sensitivity to light. After receiving photodynamic treatment, it is advised that patients stay inside for three days and avoid being exposed to bright lights. 

Is photodynamic therapy (PDT) safe for the eyes? 

As just half of the recommended amount of Verteporfin dye is injected, patients with CSR (Central serous retinopathy) who get PDT therapy have a substantially superior safety profile. As a result, this regimen has now become the accepted standard of care for CSR patients. These individuals don’t seem to have any appreciable visual loss as a result of the therapy. 

What drawbacks does the photodynamic treatment have? 

Photodynamic treatment side effects :

• cough
• difficulty swallowing 
• a stomachache 
• difficult to breathe 
• skin conditions including stinging, itching, swelling, or redness.