Overview of Fundus Camera
Fundus photography is a technique used to take a picture of the back part of the eye, or the retina. This is done using a special camera called a fundus camera. This method is particularly important because it helps in diagnosing and treating different diseases that can affect the back part of the eye. The process is facilitated by the pupil, which is the black part of the eye that allows light to reach the retina.
The first retinal photographs were published by Jackman and Webster in 1886. Later, in 1926, Carl Zeiss introduced the first fundus camera that could be purchased by anyone. In order to make the process more efficient, Hansell and Beeson attached an electronic flash tube to the camera to direct light through the pupil.
As technology evolved, there were various improvements made to retinal imaging. The images became sharper, cameras could work without dilating the pupil, and even had pupil tracking features. More recently, smart-phone imaging has been introduced, along with ultra-wide field imaging, which shows more of the retina at once. Additionally, Artificial Intelligence (AI) has been integrated into both online and offline photography to help improve the process.
Anatomy and Physiology of Fundus Camera
The retina is the part of the eye that acts like a camera, converting light signals from an object into electrical signals which are sent to the brain. This allows us to see and recognize the object. However, getting clear pictures of the retina is challenging because light must be shone on the retina and images must be taken at the same time through the tiny hole of the pupil.
The retina only reflects a small amount of light, actually less than the combined reflections from the tools used to light it up and take its picture. To overcome this, a device called a fundus camera is used, which works on a principle similar to a special type of eye examination called indirect ophthalmoscopy. Traditional fundus cameras light up the outer edge of the pupil and take pictures from the center of the pupil. By doing this, they can avoid overlapping reflections and get a clear picture of the retina.
Why do People Need Fundus Camera
A special device called a fundus camera can be used to detect any problems located at the back of the eye. Here are some issues that the fundus camera can identify and their related specialties:
1. Vitreo-Retinal diseases: These conditions are related to the vitreous humor (a clear jelly-like substance in the eye) and retina (the light-sensitive layer at the back of the eye). The problems include:
– Diabetic Retinopathy: An eye disease that diabetic patients can develop.
– Age-related macular degeneration: An eye condition that primarily affects the central part of your field of vision.
– Retinal vascular occlusions: A condition where the blood vessels in the retina are blocked.
– Retinal dystrophies: A group of inherited eye disorders affecting the retina.
– Retinopathy of prematurity: Eye problems affecting premature babies.
– Tumors of the eye, vascular lesions: This includes abnormal growths and blood vessel issues in the eye.
– Complications of surgeries involving the front part of the eye.
– Macular pathologies: Issues affecting the macula, which might include a macular hole, an epiretinal membrane (a thin sheet growing on the surface of the retina), and macular edema (swelling in the macula).
– Retinal detachment and choroidal detachment: Conditions where the retina or choroid (layer of blood vessels) pulls away from the layers of the eye.
– Vitreous abnormalities: Problems with the vitreous humor, such as bleeding, cysts, or asteroid hyalosis (tiny white spots in the vitreous humor).
2. Glaucoma: A condition that can damage the optic nerve (the bundle of nerve fibers that sends visual information from your eye to your brain), often related to high eye pressure. It can lead to optic disc damage and damage to the retinal nerve fiber layer.
3. Uvea diseases: The uvea is the middle layer of the eye. Problems can include posterior uveitis (inflammation at the back of the eye), choroidal granuloma (small, inflammatory growths in the eye), and secondary deposits from cancer elsewhere in the body. Another condition, known as intermediate uveitis, can cause symptoms such as white spots and an accumulation of white deposits in the eye.
4. Neuro-ophthalmology: This involves conditions that relate to the optic nerve, such as anterior ischemic optic neuropathy (a condition caused by reduced blood flow to the optic nerve), optic atrophy (damage to the optic nerve), and morning glory syndrome (a birth defect of the optic nerve).
5. Conditions affecting the anterior segment (front part of the eye) and surrounding structures: This includes conditions affecting the eye’s surface and inner structures closer to the front of the eye.
When a Person Should Avoid Fundus Camera
There are no firm or absolute reasons why fundus imaging, which is a picture of the back of your eye, cannot be done.
However, there are a few situations that might make fundus photography, which is a tool doctors use to take pictures of the inside of your eye, difficult:
If you have any musculoskeletal diseases – conditions that affect your muscles, bones, and joints – you might find it hard to keep your chin in the chin rest during the procedure.
If you have severe sensitivity to light (known as photophobia), especially in case of an eye injury, it can cause your eyes to close tightly (a condition called blepharospasm) and produce more tears. This can make it challenging to get a clear image.
Equipment used for Fundus Camera
A fundus camera is a sophisticated piece of equipment with a specialized camera that uses the principle of an indirect ophthalmoscope (an instrument that allows doctors to inspect the back of your eye). This camera is composed of several intricate parts.
In the fundus camera, light from a viewing lamp is projected onto a round mirror and then through a set of filters to another round mirror. Light is then reflected from the second mirror through a series of lenses. A mask within the topmost lens helps focus the light into a donut-shaped beam. This beam then hits another mirror with a hole in the center before exiting the camera, passing through the objective lens and entering the patient’s eye to take a picture. The process requires careful alignment of light rays through the border of your pupil and the image in the center of your pupil.
There are many different types of fundus cameras, which are used in clinics and hospitals around the world. As with other technologies, the fundus camera has experienced significant advancements over time. One example is the development of wide-field and ultra-widefield fundus cameras. These cameras capture images of a larger area of the retina (the light-sensitive layer at the back of the eye) — more than 50 degrees or 100 degrees of the retina’s area, respectively.
There are also a variety of systems that can capture wide-field and ultra-widefield images. These have varied capabilities, degrees of field coverage, imaging methods, and advantages and downsides.
The Optos non-contact (meaning it doesn’t need to touch your eye) ultra-widefield fundus camera uses a scanning laser ophthalmoscope (a device to visualize the eye) and can capture retinal images up to 200 degrees. Some benefits of these types of images include better resolution, suitability for use with patients with special circumstances (like children and people with hazy eye media due to cataracts), simultaneous imaging of the central and peripheral retina, and educational utility for patients.
There are also confocal scanning laser ophthalmoscope (cSLO) based fundus cameras, which utilize laser light for better quality images. Some examples of these cameras include Optos, Heidelberg Spectralis, Mirante, and Eidon. Other types of imaging include red-free fundus photography (which provides a good view of retinal blood vessels and nerve fiber layers), fundus autofluorescence (which uses the fluorescent properties of certain eye components), and multi-color imaging (which simultaneously captures several different types of reflectance images).
Fundus cameras can now even be linked with smartphones for lower-cost convenience and portability, making screening and diagnosis more accessible for certain eye diseases. Recently, artificial intelligence has started to be incorporated with fundus imaging – particularly useful for screening for diabetic retinopathy (a diabetes complication that affects the eyes). Some examples of FDA-approved smartphone-based fundus imaging systems include Welch Allyn iExaminer and Remidio Fundus on Phone device.
Who is needed to perform Fundus Camera?
Fundus photography, a process that takes pictures of the back of your eye using a special camera, can be carried out by various healthcare professionals. These can include eye doctors (ophthalmologists), optometrists (eye care professionals who can test your vision), paramedical staff, mid-level eye care practitioners or even individuals who have received training in eye photography. These professionals are all equipped with the necessary skills to successfully perform this procedure.
Preparing for Fundus Camera
Before capturing images of the back of the eye (known as the “fundus”), the doctor will explain the process and why it’s necessary. To keep everything clean, the parts of the camera that you’ll come into contact with — like the chin rest, forehead rest, and handle — will be wiped down with an alcohol swab. If you wear glasses, you’ll need to take them off for this test. You’ll be asked to sit and position your chin and forehead on the rests of the machine in a way that’s comfortable for you. Most of the time, for the best quality image without any flaws, your pupils will need to be made larger, or dilated.
How is Fundus Camera performed
This process involves taking a photo of each of your eyes, one at a time. The first step requires aligning a circle that appears on the screen with your iris and pupil. This involves adjusting the height so that three white dots appear in a symmetrical position. Next, the focus is adjusted onto your retina, the layer at the back of the eye that senses light. You will be asked to concentrate on a green light that you can see.
The equipped joystick is then moved in all directions to get a clearer view of two specific points located at what would be 3 o’clock and 9 o’clock positions on a clock face, this guarantees the camera is at the best distance from the eye. In some cameras, the good focus of the retina is indicated by two vertical lines that need to align.
For manual capture, the eyepiece must be adjusted correctly. The photographer capturing the image will wear any necessary glasses to correct their vision if required. It is important that the photographer’s eyes are at rest, meaning they aren’t straining or focusing too hard. Once the points on the screen (referred to as reticules) and the retina appear clear, a button is pressed to take the image.
This kind of exam, also known as a fundoscopy, has been taught to medical students using virtual platforms. This teaching method has been particularly useful during times like the COVID-19 pandemic when remote learning is necessary.
Stereophotography, a different process, involves taking two images, one from the right and one from the left, which are then looked at with a special viewer. To focus on objects in the front portion of your eye, additional lenses are needed. Conversely, a type of lens known as a minus lens is used to focus on the back of the eye or the retina, especially in people with a significant amount of myopia (nearsightedness).
In special cases with people who have extreme refractive errors (meaning their eyes are either far too nearsighted or farsighted); the automatic focus function of the camera might not work. In these particular cases, manual focusing is used to adequately capture an image of the retina.
Possible Complications of Fundus Camera
Using a fundus camera, a device designed to take photos of the back of your eye, is generally safe and doesn’t have complications. But, there’s a small risk that an infection could be passed from one patient to another if the camera isn’t properly cleaned. This is especially important if a patient has an active eye infection, like pink eye. Also, the bright flash from the camera might be uncomfortable for some people who are sensitive to light.
There can be some mishaps while taking pictures with the fundus camera. For example, an orange or bright patch might appear at the edge of the photo if the camera’s light shines on the colorful portion of your eye (the iris), especially if your pupil isn’t fully enlarged. To fix this, the camera should be angled so that the light goes through your pupil without hitting the iris.
Other issues might include blurry spots caused by eyelashes blocking the light. The eyes would need to be carefully held open to avoid this. If the picture is too fuzzy or lacks detail, it might be because the camera is too close or too far from the eye. The camera should be positioned at the right distance to get the most detailed and colorful image of the back of your eye.
Lastly, if there’s a consistent spot in the photos taken at different times, it could be because something has made the camera dirty. This could happen if the lens touches a patient’s face, noes or eyelashes. This issue can be resolved by cleaning the dirt or smudge from the system.
What Else Should I Know About Fundus Camera?
Fundus cameras are tools that doctors use to take pictures of the back part of your eye, which is known as the “fundus”. These images can help them diagnose and monitor a variety of eye conditions like diabetic retinopathy (DR), age-related macular degeneration (ARMD), retinal vascular disorders, and glaucoma.
Traditional fundus cameras can capture images of the center part of the back of the eye. However, there are also “wide field” and “ultra-widefield” cameras that can take pictures of the outer parts of the eye. This is important because, in cases like diabetic retinopathy, these harder-to-see areas can have changes that increase the risk of the disease getting worse.
There are also special, portable cameras that are used for newborn babies who might have a condition called retinopathy of prematurity (ROP). These cameras can be used almost anywhere, and they are really important for monitoring babies who are at risk. It’s important to note that ROP is a potentially severe eye disorder that can lead to vision loss in premature babies.
Another exciting development is the integration of artificial intelligence (AI) into these eye-examining technologies. Machine learning, a type of AI, can be used to predict whether a person’s eyes are at risk of changing after surgery due to factors such as a depth of the front part of the eye and the person’s age. Some other AI tools have been specifically designed to detect diabetic retinopathy with a high degree of accuracy.
Intriguingly, a technology called AI deep learning, which allows AI to learn from experience, can work with the pictures from fundus cameras to predict certain brain conditions. Additionally, combining fundus photography with a type of eye imaging known as OCT can heighten the ability to screen for glaucoma and diagnose cases of high myopia (an extreme degree of short-sightedness) with retinopathy.
Scientists are also studying the use of handheld fundus cameras, as well as ways to use smartphones for fundus imaging—especially for telehealth visits. However, in the case of Retinopathy of Prematurity, while smartphones can give some useful information, they may not identify all aspects of the disease.