What is a retina?
The retina is one of the most important structures of our visual system. It is a multi-layered light-sensitive tissue that lines the back of the eye and connects the visual images that you see to the brain via the optic nerve.
Retinas serve a similar function to the film in a camera. The optics of the eye create an image of the visual world on the retina. Light striking the retina initiates a cascade of chemical and electrical events that trigger nerve impulses. The photoreceptor cells, the rods and cones, are involved in this complex process. The retinal impulses are then carried through the optic nerve to the brain.
The retina has millions of photoreceptors that capture light rays and convert them into electrical impulses. These impulses actually travel along the optic nerve to the brain where they are turned into images. Any type of disruption in the traveling of these images to the brain results in vision loss or distorted vision.
The central part of the retina called the “macula” is the most sensitive aspect. If this macula is affected by disease, seeing can become very difficult. The macula is responsible for your accuracy vision, allowing you to read or recognize a person.
There are many diseases of the retina which can affect eyesight. Some common diseases such as diabetes and hypertension can directly affect the retina and cause poor functioning of the retinal cells. Other common retinal disease processes include macular degeneration and retinal detachments. All of these retinal diseases can result in a significant loss of vision.
Why are Retina Eye Exams Important?
The retina is an extension of the brain. Much like the brain tissue, the retina cannot regenerate. Diseases of the vitreous and retina can cause permanent blindness, therefore getting regular eye exams is critical for long term eye care. Our Tennessee retina eye specialists will spend a lot of time looking through your pupil at the vitreous, retina, and other structures located inside the back portion of the eye. In order to adequately see the retina, we will need to dilate eyes prior to a retinal examination. First, the pupils are dilated using eye drops (this allows a complete retinal examination). The retina is examined using various instruments that throw a strong light into the eye. Most patients do not experience any discomfort except for some glare. Early and adequate treatment can stop further damage to the retina and result in a better outcome. Retinal eye exams allow early detection and treatment of retinal disorders.
Understanding Different Retina Conditions
What Is Macular Degeneration?
Age-related macular degeneration (AMD) is a common cause of blurry vision and blindness in older adults. It is a significant cause of blindness in older people. The macula in the eye is responsible for straight vision in front of you, also known as central vision.
A study found that more than 20% of old individuals (across the globe) suffer from macular degeneration. The degeneration is of two types, i.e., dry and wet.
Dry AMD (aka atrophic AMD) is present in 90% of cases and is caused by the gradual thinning of the macula and loss of photoreceptors. Unfortunately, there is no definitive treatment for dry AMD; however, recent advances target new therapies for restoring the damage to photoreceptors.
Wet AMD accounts for only 10% of AMD cases but leads to a speedy loss of vision. Also known as advanced neovascular AMD, it is characterized by the growth of new blood vessels in the macular region. Choroidal neovascularization (new blood vessel production) is the major cause of severe vision loss in wet AMD.
What Causes Macular Degeneration?
The exact cause of macular degeneration is unknown. Certain risk factors can increase your chances of acquiring macular degeneration. The common risk factors include:
- Heart diseases
- Having a family history of AMD
How Common Is Macular Degeneration?
As per a systematic review, the global prevalence of macular degeneration is around 8%. The review also concluded that age-related macular degeneration is more common in Europeans. As of 2020, the number of macular degeneration patients was approximately 196 million, which is expected to increase to 288 million by 2040.
What Is Retinal Detachment?
The thin tissue layer present at the back of the eye can get detached from the underlying retinal epithelium leading to a severe eye condition, i.e., retinal detachment. This act can lead to permanent loss of vision.
Studies show that excessive forces separate the neurosensory retina (NSR) from the underlying retinal pigment epithelium. This eye emergency leads to the accumulation of subretinal fluid. Based on the cause of detachment, it is classified into four different types:
- Rhegmatogenous (RRD)
- Traction (TRD)
- Combined traction-rhegmatogenous
Research indicates that rhegmatogenous RD results from trauma and mainly presents a loss of field vision or vision. As it is characterized by filling fluid in the subretinal space, permanent vision loss ensures if the condition goes untreated. Patients usually see flashes of lights initially which then convert into blurry vision. Floaters and a shadow in the eye may also indicate detachment.
How Common Is Retinal Detachment?
Retinal detachment is not very common. The incidence of RRD was found to be 6.3-17.9 per 100,000 people. The mean annual incidence of bilateral RRD was 7.26%.
What Causes Retinal Detachment?
Aging makes a person prone to detachment of the retina. Pulling scar tissue following an ocular surgery may also lead to detachment of this light-sensing layer. Swollen eyes have a greater chance of retinal detachment.
What Is a Macular Hole?
The formation of holes in the inner layer of the eye (on the back) can seriously impair vision and reduce the quality of life. A macular hole is a retinal condition that goes unnoticed in the early stages. However, patients notice distorted (bent central images) and foggy images with disease progression.
The disease is similar to macular degeneration as it has symptoms and develops in the elderly.
What Causes a Macular Hole?
In most cases, the cause of a macular hole is unknown. Idiopathic macular hole (bilateral) accounts for 20.9% of the cases. Excessive stretching of the retina can end up in hole formation in the retina’s center.
Eye surgery, iatrogenic causes (injury induced by the doctor), and trauma may lead to a macular hole. It may be associated with retinal detachment. Short-sighted people are more prone to developing it, while very long-sighted individuals can also acquire it.
How Common Is a Macular Hole?
As per a study, macular holes’ incidence was between 7.8 to 8.7 per 100,000 individuals. Females are more prone to getting the disease as compared to men.
What Is Retinitis Pigmentosa?
It is a group of rare blinding diseases affecting the retina’s light receptor cells. Attack on the photoreceptors decreases their efficiency in detecting light accurately. The rate of progression of the disease is slow. The ultimate result of retinal cell breakdown is blindness.
Rods are first in line to be affected by the progressing disease. The onslaught on rods results in night blindness. Thus, patients usually are sensitive to bright light. Studies show that the initial symptom of rod-cone dystrophy (due to retinitis pigmentosa) is night blindness. Night blindness is followed by peripheral field loss and, ultimately, blindness.
How Common Is Retinitis Pigmentosa?
The prevalence of retinitis pigmentosa (non-syndromic) is approximately 1 in 40,000. It is a rare eye condition that is predominantly more common in men than women.
What Causes Retinitis Pigmentosa?
It is believed that retinitis pigmentosa has a genetic link to it. Gene mutation might be the cause of the multi-disease. Another reason for RP is ocular trauma. Eye infection can rarely lead to retinitis pigmentosa.
It may also be linked to underlying conditions, such as Usher syndrome and Bardet-Biedl syndrome.
Retinal Vein and Artery Occlusion
What Is Retinal Vein and Artery Occlusion?
Occlusions in vessels are a common disorder. Blood clots can block the flow of blood in arteries and veins of the retina. Retinal vein occlusion due to a clot can quickly damage the eyes. Blockage of the central artery is termed central retinal artery occlusion (CRAO). Temporary loss of eyesight is seen.
Research suggests that retinal vein occlusion is a common eye complication. Similarly, central retinal artery occlusion is also seen.
What Causes Retinal Vein and Artery Occlusion?
High cholesterol in the blood can lead to thrombi/emboli (clot) formation in the vessels. These blood clots can travel to the retinal vessels and cause hindrance in blood flow. Specific risk groups identified as high-risk groups include smokers, heart patients, and individuals with thick blood.
How Common Is Retinal Vein and Artery Occlusion?
Branch retinal vein occlusion was found to have an incidence of 0.5-1.2%. It is the 2nd most disorder of retinal vessels after diabetic retinopathy. According to a study, the prevalence of retinal vein occlusion has increased since 2015. As of 2008, the condition affected around 16.4 million people across the globe.
What are Ocular Malignancies?
Ocular tumors can be benign or malignant. The malignancies can develop in the retina or be transported from another organ. Choroidal melanoma is the most common ocular malignancy. The most common ocular malignancy in childhood is retinoblastoma (cancer of the retina. Patients initially complain of sensitivity to bright lights. Some individuals complain of flashes of light and floaters in their eyes.
What Causes Ocular Malignancies?
The exact causes of eye cancers (ocular malignancies) are unknown. Genetic mutations are suspected to be the primary cause. Exposure to sunlight and UV radiation can significantly risk the risk of eye cancer.
How Common are Ocular Malignancies?
Ocular malignancies or ocular melanoma is a rare type of cancer. The average annual incidence of new eye cancer patients is about five adults per million. However, it is the most widespread primary cancer of the eye, which means cancer developed in the eye instead of spreading there from any other organ.
What is Diabetic Retinopathy?
Diabetic Retinopathy refers to the most common eye condition associated with diabetes.
What causes diabetic retinopathy?
high blood glucose and consistent high blood pressure over long periods of time can weaken the blood vessels of the retina, causing them to leak and be damaged.
How common is diabetic retinopathy?
Almost 1 out of 3 people with diabetes have retinopathy. Diabetes-related retinopathy was diagnosed in 8.6% of adults aged 45 and older with diagnosed diabetes, and in 4.1% of those with diabetic retinopathy, vision loss was reported.
Keratoconus is a condition of the eye, which causes the cornea to thin out, resulting in a protrusion of the cornea. Due to the protrusion, the front of the eye appears cone-shaped, causing the light passing through to be distorted. If the cornea is not smooth, the images passing through to the retina will not appear properly. These distorted images can cause halos, starburst surrounding lights, blurred vision, multiple images, and ghosting. Keratoconus is a progressive condition that often develops in the teens and into early adulthood, gradually worsening over time.
Corneal dystrophy is a rare genetic eye condition in which one or more parts of the clear outer layer of the eye (the cornea) lose their normal clarity as a result of a buildup of cloudy material. The general term corneal dystrophy refers to a group of corneal diseases. There are many types of corneal dystrophies, and they are distinguished by the specific part or parts of the cornea affected.
Fuchs’ dystrophy is one of the more common corneal dystrophies. Fuchs’ dystrophy is an inherited condition that affects the delicate inner layer (endothelium) of the cornea. The endothelium functions as a pump mechanism, constantly removing fluids from the cornea to maintain its clarity. Tennessee Fuchs Dystrophy patients gradually lose these endothelial cells as the dystrophy progresses. Once lost, the endothelial cells do not grow back, but instead spread out to the fill empty spaces. The pump system becomes less efficient, causing corneal clouding, swelling and eventually, reduced vision.
Meet your Tennessee Retina Specialist
Donny Reeves, MD
Donny Reeves, MD is a board-certified ophthalmologist working in Johnson City and Kingsport, with experience in diagnosing and treating eye diseases of the retina. Paramount to his retina eye work is the emphasis on regular eye exams if you are suffering from retina problems or are diabetic. Retina eye exams can save vision and prevent blindness.
At The Reeves Eye Institute, we are committed to preventing blindness from retinal disease and to providing you with the best retinal care in Tennessee.
To learn more about the retina, the diagnosis of diseases, medical treatments, and injections for retinal diseases, please contact us for your exam at 423-722-1311.