Category: EYECARE

CORNEAEYECARE

Corneal Transplants in Ophthalmology

August was Organ Donor Awareness Month. Organ donation holds tremendous value in the field of Ophthalmology, as it offers hope and improved quality of life to many individuals suffering from vision impairment or blindness. The transplantation of corneas, the clear front surface of the eye, is the primary focus of organ donation in Ophthalmology. Corneal transplantation is a sight-saving procedure that can restore vision to those with severe corneal diseases or damage, that would otherwise result in irreversible severe visual deterioration or blindness. Corneal tissue, obtained through organ donation, replaces damaged or diseased corneas, enabling recipients to regain their sight and lead more fulfilling lives after their postoperative recovery. In the Western Cape, organ transplants are undertaken in both government and private hospitals e (e.g. heart, kidney, liver, corneal transplants).

You can hear Amanda, the founder of Eyes2Eyes, speak about her lifechanging experience of receiving a corneal transplant here as part of Cape Talk’s Gift of Life podcast series last month. Becoming an Organ Donor is very quick and you can potentially save 7 lives simultaneously. You can sign-up here in 1 minute to register as an Organ Donor.

The rest of the blog will give a little bit more detail on the types of corneal transplants. For clarity, the structure of the cornea is shown in Figure 1. Much has evolved since Eduard Konrad Zirm performed the first successful full thickness corneal transplant (penetrating keratoplasty) in a human in 1905. Various other corneal transplantation techniques now exist, collectively termed “lamellar surgery” and are also summarised below in writing and in Figure 2.

 Figure 1: Structure of the Cornea

  1. Penetrating Keratoplasty (PK)
  • Replacement of entire cornea thickness (epithelium, stroma, endothelium)
  • Useful when there significant scarring, corneal shape changes (e.g. keratoconus with a history of hydrops), significant involvement of the back of the cornea, and ulcerations or perforations through the cornea
  • Details: Compared to other techniques, it requires a longer recovery time after the operation is finished, higher risk of the body mounting an immune reaction against the transplant, higher risk of the transplant losing integrity over the course of the patient’s lifetime, higher risk of needing rigid gas permeable lenses to correct astigmatism from the transplant.
  1. Deep Anterior Lamellar Keratoplasty (DALK)
  • Selective replacement of the corneal stroma. The native Descemet membrane and endothelium remain in place.
  • Useful when needing to replace corneal stroma in the presence of healthy endothelium, certain types of corneal stromal dystrophies, and corneal ulcers that are not full thickness.
  • Details: The surgery is more complex to perform than PK, but there is less risk of endothelial rejection of the transplant, and the transplant has greater integrity because the wound size is smaller.
  1. Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK)
  • Selective removal of the patient’s Descemet membrane and endothelium, followed by transplantation of donor corneal endothelium and Descemet’s membrane in addition to a thin layer of posterior donor stroma to facilitate handling of the tissue.
  • Useful to treat corneal oedema (in the presence of corneal dystrophies), iridocorneal endothelial syndrome, endothelial failure with prior intraocular surgery
  • Details: relatively rapid healing time and visual rehabilitation (minimal change to corneal curvature); less risk of graft rejection and suture-related complications compared to PK and DALK; there is risk of postoperative graft dislocation (it is a very thin layer of tissue being transplanted … 100 – 200μm thick!).
  1. Descemet’s Membrane Endothelial Keratoplasty (DMEK)
  • Selective removal of the patient’s Descemet membrane and endothelium, followed by transplantation of donor corneal endothelium and Descemet’s membrane without adding stroma. This tissue graft is 10-15μm thick!!! (± x10 thinner than in DSAEK!!!).
  • Useful for similar conditions to DSAEK.
  • Details: offers the most rapid visual rehabilitation of any keratoplasty technique; transplants minimal tissue meaning that there is lower risk of allograft rejection and less long-term reliance on topical steroids.
  1. Keratoprosthesis
  • Full-thickness removal of the cornea and replacement by an artificial cornea
  • Useful in patients with history of multiple failed PKs, severe keratitis and ocular surface disease resulting from limbal stem cell failure (e.g. Steven Johnson’s Syndrome) and chemical injury.

The future of corneal transplantation looks promising with advancements in surgical techniques and regenerative medicine. Laser-assisted procedures and 3D bioprinting are enhancing precision and efficiency, leading to shorter recovery times and better outcomes for patients. Laboratory grown corneas may also reduce donor tissue reliance and customization, reducing risks of rejection.

Figure 2: Schematic portraying the region of corneal tissue transplanted (red) for various modern keratoplasty techniques, including penetrating keratoplasty (PK), deep anterior lamellar keratoplasty (DALK), Descemet stripping automated endothelial keratoplasty (DSAEK), Descemet membrane endothelial keratoplasty (DMEK), and Boston Type I Keratoprosthesis (KPRO). Reproduced from University of Iowa from this link.

EYECARESCIENCE

Piezoelectric eye drops- same medication, different system

In the field of ophthalmology, precision and accuracy are of paramount importance when it comes to delivering medication to the delicate tissues of the eye. Traditional eye drop delivery methods have their limitations, often leading to inconsistent dosages and wastage. Piezoelectric eye drop delivery systems could theoretically offer precise, controlled, and touchless administration of medication. Piezoelectric materials have a unique property where they generate an electric charge when subjected to mechanical stress or pressure.

Advantages:

  1. Precise and controlled dosage administration
  2. Minimize contamination and wastage
  3. Improved patient experience and compliance to eyedrops

One of the potential main advantages of piezoelectric eye drop delivery systems is their ability to provide precise and controlled dosage administration. The mechanical pressure applied to the piezoelectric material causes it to generate an electric charge, triggering the release of eye drops. This mechanism allows for accurate and consistent dosage delivery, reducing the risk of over or under medication. With traditional eye drop methods, variations in hand pressure or technique often lead to imprecise dosage, compromising the effectiveness of treatment. Overflow of the eyedrops to the surrounding structures (e.g. eyelids, eyelashes) can cause local irritation and discomfort for patients. There is also greater risk of the medication unevenly distributing to the nasolacrimal duct, which facilitates the draining of the ocular surface into the nasal passage, potentially leading to systemic absorption of the compounds inside the eyedrops, which may lead to more side-effects.

Another significant advantage of piezoelectric eye drop delivery systems is their potential to minimize contamination and wastage. Conventional eye drop bottles are prone to contamination as they come into contact with the eye’s surface, skin, and eyelashes. Additionally, the imprecise squeeze and dropper mechanisms of traditional methods often result in excessive drops being dispensed, leading to wastage. A major portion of each conventional eyedrop administered is blinked out and drained into the nasolacrimal duct system (a small drainage system connects the eye to the nose). Piezoelectric systems address these issues by offering a touchless delivery method that eliminates contamination risk and ensures efficient drug utilization. This not only enhances patient safety but also reduces overall healthcare costs.

Piezoelectric eye drop delivery systems also offer an improved patient experience compared to traditional methods. When using conventional eye drops, the patient has to incline the face almost 90° to ensure that the eye drops are administered into the eyes under gravity – this is very physically difficult for some people, especially the elderly, and especially when multiple drops are needed per day. Piezoelectric systems allow the patient to be upright during eyedrop administration. Further, the touchless and precise nature of the technology eliminates the need for direct contact with the eye, making it more comfortable for patients, especially those with sensitive or compromised ocular tissues. Moreover, the controlled release mechanism reduces the sensation of an excessive liquid flow, making the process less intrusive and more pleasant.

In summary, piezoelectric eye drop delivery systems have the potential to optimise corneal care in several ways:

  1. Treatment of Ophthalmic Diseases: Conditions such as dry eye syndrome, corneal infections, and glaucoma often require frequent and precise administration of medications. Piezoelectric devices can enhance the efficacy of these treatments by ensuring consistent and accurate dosing, leading to improved outcomes for patients.
  2. Post-Surgical Recovery: Following corneal surgeries, patients often need to self-administer eye drops for an extended period. Piezoelectric delivery systems can simplify this process, reducing the likelihood of mistakes and enhancing the overall recovery experience.
  3. Research and Development: The ability to precisely control the dosage and delivery of medications opens up new possibilities for researchers studying corneal diseases. Piezoelectric systems can facilitate the development of innovative therapies, targeted drug delivery strategies, and improved understanding of drug interactions with the cornea.

Figure 1: An example of a piezo-electric eyedrop delivery device, discussed in further depth by Pasquale et. al (1). Reproduced via Open Access.

Sounds great. What’s the catch? More research is needed … it will take a while until these device systems become mainstream.

References:

  1. Pasquale LR, Lin S, Weinreb RN, et al. Latanoprost with high precision, piezo-print microdose delivery for IOP lowering: clinical results of the PG21 study of 0.4 µg daily microdose. Clin Ophthalmol 2018;12:2451-7.
  2. Yao G, Mo X, Liu S, et al. Snowflake-inspired and blink-driven flexible piezoelectric contact lenses for effective corneal injury repair. Nature Communications 2023;14:3604.
  3. Shaukat H, Ali A, Bibi S, et al. A Review of the Recent Advances in Piezoelectric Materials, Energy Harvester Structures, and Their Applications in Analytical Chemistry. Applied Sciences 2023;13:1300.
CORNEAEYECAREFOOD AND WATERHEALTH PROMOTION

5 tips to keep your eyes healthy

Eyes are rich sensory organs (so practically speaking, they have feelings!). They eyes are happier when they are healthier – they function better and for longer, and there is less need to seek care from optometrists and ophthalmologists. Five general everyday tips are included below that could be used to keep your eyes in good health.

1. Protect your eyes from the sun

UV (ultraviolet) rays, which are given off by direct sunlight, can be harmful to your skin and eyes. If you have consistent sun exposure, without proper eye protection, there is a higher risk of developing cataracts. Certain UV rays of greater intensity are also more aggressive towards the retina. Your thin skin around your eyes can also develop skin cancer and wrinkles. Be sure to wear UV-protective sunglasses even on cloudy days.

2. Have a well-balanced, nutrient rich diet

Eating bright and colourful vegetables can help protect and fortify your eyesight. Orange carrots are full of beta carotene, which is the precursor of Vitamin A. This vitamin is a valuable antioxidant that helps reduce molecular stress and renew cells in the eyes. Oranges and peppers contain Vitamin C, Vitamin E, zeaxanthin, and lutein. These nutrients lower your risk of developing macular degeneration. Green vegetables, like broccoli, kale, lettuce, and peas, also contain valuable nutrients for your cornea and other eye structures. Some light cooking will keep most of their nutrients intact.

3. Don’t smoke

The free-radicals in tobacco smoke make smoking harmful to the eye in two main ways. Firstly, the direct irritation caused by the smoke coming into contact with the eye, which irritates and damages the cornea. The free radicals are responsible for damaging the lipids and proteins in the eyes and causing deposits to form on the surface of the eye’s lens— leading to cataract development. Secondly, there are systemic effects of smoking reduces blood oxygen, damages the blood vessels and causes widespread inflammation. The cumulative effect of this could cause damage to the insulating layer between the retina and the blood vessels that nourish it, potentially leading to degeneration of the macula, which is responsible for receiving light at the centre of the eye.

4. Take regular eye breaks

If you are concentrating on your computer or general work tasks at a desk all day, you can develop eye strain. To rest your eyes, try to concentrate on blinking – it is easy to forget when you are very focused. Try blink for three to four seconds at a time for about two minutes. This will help lubricate your eyes. The tears will cleanse your eyes to improve your focus. It is also valuable to rest your eyes completely from your tasks. For example, every 20 minutes, you could look at something 20 feet away for 20 seconds.

5. Exercise

Exercise improves blood flow throughout the body and removes waste products from all your organs. Exercise is especially good for supplying the retina and optic nerve with important nutrients so that they work optimally. Exercise is also important for corneal nourishment. Additionally, long-term exercise has the effect of reducing the pressure inside your eyes, which prevents permanent damage to your optic nerve. Without a working optic nerve, light signals will not be sent from the eye to the brain, causing vision loss. However, it is important to not be too strenuous with exercise (e.g. with very heavy weights) as this can cause damage! Equally, if you feel pain in your eyes during exercise, it is advisable to take a break and seek medical attention if the problem persists. 

EYECARESCIENCE

Gene Therapy in Ophthalmology

Gene therapy describes the introduction of normal genes into cells in place of missing or defective ones in order to correct genetic disorders. Gene therapy in ophthalmology has made significant advances in recent years, with numerous clinical trials showing promising results. The eye is considered a good candidate for gene therapy; it is small and compartmentalised, requires relatively small numbers of vectors/gene copies, and has special immune response features that can be favourable for gene therapy (1). Some of the key advancements in this field include:

  1. Treatment for corneal dystrophies: Corneal dystrophies are a group of inherited disorders that cause progressive clouding of the cornea, leading to vision loss. Gene therapy approaches aim to replace or repair the defective gene responsible for the disease. 
  2. Treatment for Retinal Diseases: Gene therapy has shown promising results in the treatment of retinal diseases such as age-related macular degeneration, retinitis pigmentosa, and Leber congenital amaurosis. Gene therapy has shown to restore vision and improve visual acuity in patients with these conditions.
  3. CRISPR-Cas9 Technology: CRISPR-Cas9 technology has allowed for precise and efficient editing of specific genes, making it a powerful tool for gene therapy in ophthalmology. This technology has been used to correct mutations that cause retinal diseases, leading to improved visual function.
  4. Viral Vectors: Lentiviral and adeno-associated virus (AAV) vectors have also become a popular tool in gene therapy for ocular diseases due to their ability to efficiently deliver therapeutic genes to the retina. AAV vectors in particular have been used to deliver genes to treat conditions such as retinitis pigmentosa, choroideremia, and Stargardt disease.
  5. Improved Delivery Methods: Advances in delivery methods, such as the use of subretinal injections and intravitreal injections, have improved the delivery of therapeutic genes to the retina, resulting in more effective treatment of retinal diseases.

One type of gene therapy for ophthalmology has already been approved by the United States Food and Drug Administration (FDA) to treat paediatric patients with a retinal condition called Leber congenital amaurosis who have a deficiency in the RPE65 gene (2). The RPE65 gene provides instructions for making a protein called RPE65, which is involved in the production of a molecule called 11-cis-retinal, an essential component of the visual cycle that allows people to process light.

References:

  1. Bennett J. Immune response following intraocular delivery of recombinant viral vectors. Gene Ther. 2003;10(11):977-82.
  2. Russell S, Bennett J, Wellman JA, Chung DC, Yu ZF, Tillman A, et al. Efficacy and safety of voretigene neparvovec (AAV2-hRPE65v2) in patients with RPE65-mediated inherited retinal dystrophy: a randomised, controlled, open-label, phase 3 trial. Lancet. 2017;390(10097):849-60.

CORNEAEYECARE

10 interesting facts about the Cornea

  1. The cornea is the clear outer layer of the eye, covering the iris and pupil. The cornea is so transparent that it’s almost invisible.
  2. The cornea provides about 2/3 of the eye’s total optical power. A healthy cornea is essential for good vision, as even a small amount of damage to the cornea can significantly affect vision.
  3. The cornea is avascular, meaning it contains no blood vessels. The cornea can be thought of as more resistant to infections than other parts of the eye because it has no blood vessels.
  4. The cornea is made up of 5 distinct layers, including the epithelium, Bowman’s layer, the stroma, Descemet’s membrane, and the endothelium.
  5. The cornea has a high number of nerve endings, making it one of the most sensitive tissues in the body.
  6. The cornea is an important part of the eye’s immune defence system.
  7. The cornea can be transplanted from one person to another without extensive use of immunosuppressive drugs.
  8. The cornea has the ability to regenerate itself, but the process can be slow. The cornea is often used for research on wound healing and regenerative medicine.
  9. Contact lenses can be made from materials that mimic the structure and function of the cornea.
  10. The cornea helps to reduce glare and protects the eye from harmful UV rays. A damaged cornea can cause significant vision loss, and corneal transplant surgery may be needed to restore vision.
EYECARE

A quick look at the eyeball

Have you ever wondered about the structures that make up the eyeball and allow us to see? Let’s start at the front of the eye and work our way back.

The Cornea: 

The clear layer covering the front of the eye that lets the light get through. It has 5 layers, which can be susceptible to disease. An example is Keratoconus, when the cornea becomes “cone-shaped”. Contact lenses are placed over the cornea to help with guiding light towards the retina to allow you to see. 

The Iris

The colourful, circular muscle that expands and contracts to control the amount of light that gets in. The iris has two layers – at the front, some fibrous cells collectively called the stroma, and at the back, pigmented cells. The pigment is called “melanin” which makes the iris brown and opaque, allowing it to control the amount of light passing through. This is the same pigment found in our skin, and the amount that each person has varies according to their genetics. 

People with blue eyes have no pigment at all in this front layer – this causes the fibres in the iris to scatter and absorb some of the longer wavelengths of light (i.e. red, yellow, green) that come in. More blue light is reflected back out and the eyes appear to be blue. For people with hazel or green eyes, at least one of the layers of the iris contains light brown pigment. The light brown pigment interacts with the blue light and the eye can look green or speckled. 

The Lens:

The transparent disc that changes its shape to focus on objects at different distances. It can be thought of as a magnifying glass that bends and adjusts the trajectory of light coming into the eye so that it can hit the retina and be converted to an image. Cataracts happen when the lens loses its transparency, preventing light from entering the eye. Cataract surgery involves replacing the cloudy part of the lens with a new, transparent lens. 

The Retina: 

The thin layer of tissue at the back of the eye where the photoreceptors (light-sensitive cells called rods and cones) are. It receives adjusted light from the lens. The retina has lots of blood vessels and connections with the brain through the optic nerve. It is important to keep your blood pressure and blood sugar levels controlled so that the blood vessels inside the retina do not get damaged to make you lose your vision. 

The Optic Nerve: 

This collects visual information from the retina and rapidly transmits it to the brain for processing. Each of your eyes transfers information to your brain at about the same speed as a fast ethernet connection cable. 



EYECARE

The increasing global demand for eye-care services

There are approximately 8 billion people in the world. According to the WHO, globally, at least 2.2 billion people have a near or distance vision impairment. In at least 1 billion of these cases, vision impairment could have been prevented or has yet to be addressed. The demand for eye healthcare is on the rise globally, and it is becoming increasingly important to address the need for stronger eye healthcare services in developing countries. The demand for eye care services is driven by several factors including the increase in non-communicable diseases (e.g. diabetes, high cholesterol, high blood pressure) and an aging population. An aging population is one of the primary drivers of the increasing demand for eye healthcare. As people age, the risk of developing eye diseases such as age-related macular degeneration (AMD), cataracts, and glaucoma increases. These conditions can lead to vision loss and blindness, which can greatly impact an individual’s quality of life.

The growing awareness of eye health among the general public has also contributed to the demand for eye care services. People are becoming more aware of the importance of maintaining good eye health and are taking proactive measures to prevent eye diseases. This includes regular eye exams, healthy lifestyle choices, and the use of protective eyewear.

However, despite the growing demand for eye healthcare, access to eye care services remains limited in many developing countries. This is due to a lack of infrastructure, trained eye care professionals, and financial resources. This creates a significant disparity in eye care access between developed and developing countries, and it is having a major impact on the health and well-being of populations in developing countries. In developing countries, many people lack access to basic eye care services, such as eye exams, treatment for common eye diseases, and corrective vision devices such as eyeglasses. This results in preventable vision loss and blindness, which can have a significant impact on an individual’s quality of life, as well as their ability to work and participate in society. In addition, a lack of access to eye care services can lead to a vicious cycle of poverty and poor health, as people with vision loss or blindness are often unable to work and support themselves and their families.

To address the need for stronger eye healthcare services in developing countries, it is crucial to invest in eye care infrastructure and to train eye care professionals. This includes building eye care clinics and hospitals, and providing training and support to eye care professionals, such as optometrists and ophthalmologists. The Aravind Eye Hospitals in India are a strong example of how high-quality eye healthcare services can established and effectively run in developing countries. It has had a major impact in eradicating cataract related blindness in India. The Aravind Eye System recently expanded to Nigeria in 2018, where it manages the Tulsi Chanrai foundation.

In addition, it is important to provide access to essential eye care services, such as eye exams, treatment for common eye diseases, and corrective vision devices such as eyeglasses. This can be accomplished through initiatives such as outreach programs, mobile eye clinics, and partnerships with local communities. An example of a successful outreach programme is the Eyes2Eyes Scleral Lens programme, which was launched in June 2021.

It is also important to raise awareness about eye health and to promote healthy lifestyle choices. This includes educating the public about the importance of regular eye exams, and promoting healthy habits such as maintaining a healthy diet, avoiding smoking, and wearing protective eyewear. By raising awareness about the importance of eye health, people can take proactive measures to prevent eye diseases and maintain good eye health. As an organisation, Eyes2Eyes is dedicated to raising awareness about eye health and conditions, and improving access to high-quality eye care, especially for problems affecting the cornea in younger people, in the Western Cape.

To summarise, the demand for eye healthcare is increasing globally, driven by ageing, increase in non-communicable diseases and growing awareness of eye health among the general public. It is becoming increasingly important to address the need for stronger eye healthcare services in developing countries through investments into training, providing access to essential eye care services, and raising further awareness about eye health.

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