The eye, an organ exposed to the outside and easy to explore, can show signs of alterations in different parts of the body, making it a key indicator for diagnosing pathologies beyond ocular ones. Its exposure to the outside, high vascularization, and direct connection to the brain are crucial in turning the eye into a powerful diagnostic window.
The close relationship between ocular health and general health makes the identification of diseases through visual examination crucial in the prevention, early detection, and treatment of systemic and even tumoral pathologies. In the case of individuals already diagnosed with certain systemic diseases, eye exams are essential to monitor their progression and detect and anticipate possible complications.
Many diseases or alterations manifest through the visual system. This is because the eye often suffers the consequences of systemic diseases, and visual symptoms are also the first manifestation of pathologies.
According to Lucía González Buendía, a specialist in the diagnosis and medical treatment of retinal and macular pathologies at the Miranza Ophthalmology Group, the retina and macula are excellent indicators of systemic pathologies. "The retina acts as a true 'informant' about the general health status of the body. Being a highly vascularized tissue and sensitive to metabolic, immunological, or infectious alterations, many systemic diseases manifest early in the retina. For example, arterial hypertension and diabetes mellitus can cause easily identifiable retinal alterations in a routine fundus examination. In fact, sometimes the ophthalmologist is the first to detect suggestive signs of a systemic disease."
According to this professional's experience, although it may vary depending on the patients' profile and the setting (hospital, outpatient, or emergency), it could be estimated that "between 10% and 20% of the patients we see present ophthalmological signs that make us suspect an underlying systemic pathology." In hospital centers or medical retina units, that percentage can be even higher, González Buendía points out, explaining that sometimes the reason for consultation is a visual symptom (such as vision loss or seeing floaters, for example). "However, the ophthalmological examination guides the diagnosis of diseases such as diabetes, arterial hypertension, autoimmune diseases, infections, or even tumors."
Vascular diseases stand out among the conditions that can manifest in vision. The retina, responsible for transforming light into electrical impulses that the brain interprets as images, is highly vascularized, meaning it has an extensive network of blood vessels. "These vessels are susceptible to changes in blood circulation that can occur due to systemic diseases. Alterations in these vessels, such as thickening, rupture, or narrowing, can reflect diseases in the cardiovascular or metabolic system."
Diabetic retinopathy, which damages the blood vessels of the retina, can be identified by an ophthalmologist in early stages, "even before the patient knows they have diabetes. Also, arterial hypertension can damage the veins and arteries of the retina, leading to hypertensive retinopathy. Therefore, early detection of these pathologies facilitates more effective control and prevents irreversible vision damage."
Certain neurological disorders, such as increased intracranial pressure (caused by a brain tumor or hemorrhage), papilledema, or optic nerve edema, can be reflected in the eye, specifically in the state of the optic nerve, which is part of the central nervous system and is responsible for transmitting visual signals from the retina to the brain.
In the Eyes and Through the Eyes
Autoimmune diseases, such as sarcoidosis, Behçet's disease, and multiple sclerosis, or infections affecting other parts of the body, can also manifest in the eye. These complications can attack the eyes, causing inflammation in the retina or other ocular structures, providing early warning of underlying pathologies.
Regarding the appearance of the eyes, González Buendía indicates that signs of various pathologies or health problems can be detected visually. "Changes in the color of the white part of the eye, the cornea, the iris, or even in the eye's shape can reflect both ocular and systemic conditions. For example, jaundice is due to an excess of bilirubin in the blood, which is usually related to liver problems, biliary ducts, or hemolysis."
Redness of the eyes can also be visually detected and occurs when blood vessels on the eye's surface dilate. This manifestation can be due to various factors such as conjunctivitis, acute glaucoma, fatigue, or eye irritation.
In the case of eyes that are very prominent or 'bulging,' "the patient may have a thyroid problem such as Graves-Basedow disease. Finally, changes in pupil size can also be indicative of neurological problems or intoxications."
Vascular, neurological, or autoimmune pathologies can be detected through eye examination. Their external appearance also provides important information.
Regarding whether to treat the ophthalmological pathology first or refer to specialists for the detected systemic disease, the ophthalmologist points out that, as a general rule, when a systemic disease affects the retina, "the treatment should be for the underlying disease. This way, we usually see an improvement in the ophthalmological examination by controlling the specific pathology."
However, she emphasizes that in certain situations, it is also necessary to treat the eye - with intravitreal corticosteroids, anti-angiogenics, or even surgery, for example - which, in her opinion, highlights that a multidisciplinary approach is undoubtedly key in these situations. "If we detect a possible systemic disease, the next step is to refer to the corresponding specialist (Endocrinology, Neurology, Internal Medicine, Rheumatology, among others) to complete the study and treat the underlying cause. Ophthalmological treatment can be symptomatic or supportive, but it is essential to address the root of the problem to achieve lasting visual recovery."
Early Indicators of Tumors and Metastasis
The development of many neoplastic processes can go unnoticed until they present symptoms. Vision loss can be an indicator of the presence of a tumor that, on one hand, directly affects ocular structures such as the retina or orbit, and on the other hand, originates in organs such as the brain or lungs. According to José García-Arumí, an expert in ocular oncology at the Miranza Group, the eye can be a frequent site of metastasis derived from other tumors, especially in the choroid, the intermediate layer of the eyeball, which is highly vascularized. "Since the eye is transparent, we can directly see these metastases, which can even help us diagnose tumors in other sites that have not yet been identified."
Essentially, the two tumors that most frequently metastasize to the eye are breast neoplasms and lung cancers, according to the specialist.
"In the case of breast cancer, it is usually diagnosed before ocular metastasis appears, as it is more accessible. However, with lung cancer, the diagnosis is often made after the ophthalmologist detects ocular metastasis. Through the pupil, we can observe these lesions, and this can be the first indication of the previously unknown disease."
Breast and lung cancers are the tumors that most frequently metastasize to the eye. In some cases, they are the first indication of cancer.
García-Arumí also mentions other less common types of tumors, such as those of gastrointestinal, renal, or cutaneous origin. Additionally, there are tumors that directly affect vision-related structures, such as brain tumors, which, depending on their location, can alter the structures that transmit visual stimuli from the retina to the brain, potentially causing blurred vision, double vision, or reduced visual field.
"The importance of early detection of these tumors lies not only in improving the patient's overall prognosis but also in preventing irreversible vision loss, as the nerve fibers of the optic nerve do not regenerate."
Ocular metastases are amenable to systemic therapy, such as chemotherapy, immunotherapy, or immunomodulatory treatments. However, in many cases, specific local treatment is necessary, and therefore, ophthalmologists are the professionals responsible for managing them.
"Since it is a fairly specialized field, we have much more knowledge of ocular metastases. Most treatments are local, meaning that we have to apply radiation locally, either with radioactive plaques placed on the eye's surface to irradiate these tumors or with external radiation using protons or electrons. Proton radiation, which until recently could not be done in Barcelona, now has two proton therapy units being set up that can also treat with this system."
Regarding monitoring, it is emphasized that ophthalmologists also perform it, and even "we are the ones who request tests to monitor the evolution of the tumor in other organs because metastases can affect the eye, but they can also affect other organs. Eye tumors, such as choroidal melanomas, can also metastasize to other parts of the body. These patients should undergo metastasis screening with magnetic resonance imaging, and it is the ophthalmologist who is responsible for this."
However, it is stressed that all treatment is always carried out in close collaboration with oncologists, who "are the ones who really need to guide us on organ involvement. This helps us a lot to understand how the disease will evolve at the ocular level."
The ability to 'see' pathologies beyond visual ones focuses on the advances that ophthalmology has experienced in recent times. Diverse and very precise tests allow the detection of neurological, immunological, or infectious pathologies through eye analysis, as indicated by Lucía González Buendía, who provides clear examples of these examinations: fundoscopy, OCT (optical coherence tomography), fluorescein angiography evaluating ocular circulation, visual field and pupil tests, as well as electrophysiology in more complex cases.
"In summary, advanced tests are indeed performed to detect diseases beyond the eye. Ophthalmology is a highly technological specialty in which we work with a large number of complementary tests. This makes it a specialty with a high level of diagnostic precision, and very important in detecting systemic diseases in early stages."