Thyroid Eye Disease (TED) is an autoimmune condition affecting the tissues around the eyes. It often develops in individuals with an overactive thyroid, particularly Graves’ disease, but can also occur with normal or low thyroid hormone levels. Assessing disease activity and inflammation is important for guiding treatment. The Clinical Activity Score (CAS) is a standardized tool used by healthcare professionals to measure this inflammatory activity.
What is Thyroid Eye Disease
Thyroid Eye Disease (TED), also known as Graves’ ophthalmopathy, is an autoimmune disorder. The body’s immune system mistakenly attacks healthy tissues around the eyes, primarily targeting muscles and fat within the eye socket. This leads to inflammation and enlargement of these tissues. While frequently associated with Graves’ disease, it is a distinct condition, and treating the thyroid disorder alone may not resolve the eye symptoms.
Symptoms include redness of the eyes and eyelids, swelling around the eyes, and a gritty or dry sensation. Individuals may also notice bulging of the eyeballs or retraction of the eyelids. These symptoms can vary in intensity and may affect one or both eyes.
Purpose of the Clinical Activity Score
The Clinical Activity Score (CAS) is a standardized method used by clinicians to quantify active inflammation in Thyroid Eye Disease. Its primary purpose is to distinguish between the active, inflammatory phase and a more stable, inactive phase. This distinction is important because active TED is more likely to respond to anti-inflammatory treatments.
The CAS provides a numerical value that guides healthcare professionals in making informed decisions about treatment strategies. A higher score indicates a greater degree of active inflammation, suggesting interventions like corticosteroids or other immunosuppressants may be beneficial. Clinicians use the score to monitor disease progression or its response to treatment over time.
The CAS is also used in clinical trials to evaluate the effectiveness of new therapies for TED. It helps researchers objectively measure changes in inflammatory signs and symptoms, contributing to the development of more targeted treatments.
How the Score is Calculated
The Clinical Activity Score (CAS) is determined by assessing inflammatory signs and patient-reported symptoms. Each present sign or symptom contributes one point to the total score. The most common version of the CAS involves seven criteria, leading to a maximum possible score of 7.
These criteria include:
- Spontaneous orbital pain (pain behind the eye not caused by movement)
- Pain with eye movement
- Redness of the eyelids (eyelid erythema)
- Redness of the conjunctiva (the thin membrane covering the white part of the eye)
- Swelling of the eyelids
- Swelling of the conjunctiva (chemosis)
- Inflammation of the plica or caruncle (small structures in the inner corner of the eye)
For follow-up assessments, a 10-point CAS may sometimes be used, incorporating additional measures. These can include an increase of 2 millimeters or more in proptosis (eye bulging), a decrease of 8 degrees or more in eye movement, or a reduction of visual acuity by at least one line on an eye chart. The assessment focuses on changes observed over the past four weeks.
Meaning of Your Score
A higher Clinical Activity Score (CAS) indicates a more active and inflammatory phase of Thyroid Eye Disease, often prompting medical intervention. A score of 3 or more on the 7-point scale is considered indicative of active disease.
When a patient has a CAS of 3 or higher, it suggests ongoing inflammation that may benefit from active medical management. This often includes therapies like corticosteroids, which reduce inflammation, or other immunosuppressive medications. The goal is to control the inflammatory process and prevent further damage to eye tissues.
Conversely, lower CAS values, such as 0, 1, or 2, suggest the disease is less active or has entered a quiescent phase. Management may then focus on addressing residual symptoms or structural changes rather than active inflammation. This might involve watchful waiting or considering surgical interventions once inflammation has subsided. The CAS is one piece of information healthcare providers use, combined with other clinical findings and the patient’s overall symptoms, to create a comprehensive treatment plan.
Other Considerations for Thyroid Eye Disease
Managing Thyroid Eye Disease involves a comprehensive approach beyond the Clinical Activity Score. Other factors determining disease severity include eye bulging (proptosis), double vision (diplopia), and vision impairment, such as optic neuropathy.
A multidisciplinary team approach is employed, involving specialists like endocrinologists, ophthalmologists, and oculoplastic surgeons. This collaboration ensures all aspects of the disease are addressed. Lifestyle factors are also important; smoking cessation is strongly advised as it can worsen the course of TED.