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PubMed This is a summary of 16 peer-reviewed journal articles Updated
Ophthalmology

Staging and Scoring Your Progress: CAS and EUGOGO

At a Glance

Doctors stage Thyroid Eye Disease using two systems: the Clinical Activity Score (CAS) to measure active inflammation and the EUGOGO scale to assess disease severity. A CAS of 3 or higher indicates active disease that typically responds best to medical treatments like steroids or biologics.

To give you the best care, your medical team needs to answer two fundamental questions: Is your disease currently “on fire” (activity), and how much change or damage has it caused (severity) [1]? To do this, they use two primary scoring systems: the Clinical Activity Score (CAS) and the EUGOGO severity classification [2].

Measuring the “Fire”: The Clinical Activity Score (CAS)

The CAS is a checklist used to determine if your immune system is actively attacking the tissues behind your eyes.

At your initial diagnosis, your doctor uses a 7-point scale, giving you 1 point for each of the following symptoms [2][3]:

  1. Spontaneous pain: A dull ache behind the eye socket while resting.
  2. Gaze-evoked pain: Pain when looking up, down, or to the sides.
  3. Eyelid redness: Redness on the skin of the eyelids.
  4. Conjunctival redness: Redness on the white part of the eyeball.
  5. Eyelid swelling: Visible puffiness or “bags” around the eyes.
  6. Chemosis: Swelling of the clear lining over the white of the eye (it may look like a gel-like bubble).
  7. Inflammation of the caruncle: Redness or swelling of the small pink bump in the inner corner of your eye.

(Note: During follow-up visits, doctors often use an expanded 10-point scale that also tracks new increases in bulging, worsened eye movement, or worsened vision to closely monitor your progress [2].)

What Your Score Means

  • Active Disease (Score of 3 or higher): If your initial score is 3/7 or higher, your disease is considered active [4][5]. This is the “critical window” where anti-inflammatory treatments like IV steroids or biologics are most effective [6][7].
  • Inactive Disease (Score below 3): This suggests the inflammation has calmed down. At this stage, medical treatments are less effective, and doctors usually focus on rehabilitative surgery to correct structural changes [8][9].

Measuring the “Damage”: EUGOGO Severity

While CAS measures the “fire,” the EUGOGO system (developed by the European Group on Graves’ Orbitopathy) measures the “damage.” It groups patients into three tiers based on how much the disease affects their eyes and daily life [10][1].

Tier Description Typical Features
Mild Minor impact on life Slight lid retraction, minor bulging, and dry eye symptoms [11].
Moderate-to-Severe Significant impact Constant double vision, significant bulging (proptosis), or eyelid retraction that interferes with closing the eyes [6].
Sight-Threatening Medical Emergency Evidence of optic nerve compression or severe breakdown of the cornea (the clear front of the eye) [12][13].

Putting It All Together

Your doctor uses both scores to build your treatment plan. For example:

  • Active + Moderate-to-Severe: High-intensity medical treatments to put out the fire and reduce swelling [14][7].
  • Inactive + Moderate-to-Severe: Surgery (like orbital decompression) to fix the structural changes [14].
  • Sight-Threatening: Immediate, emergency intervention regardless of the CAS score to save your vision [15][16].

Common questions in this guide

What is a Clinical Activity Score (CAS) for Thyroid Eye Disease?
The Clinical Activity Score (CAS) is a checklist your doctor uses to determine if your eye inflammation is active. It assigns points based on symptoms like eye pain, redness, and swelling, usually on a 7-point scale during your initial diagnosis.
What does a CAS score of 3 or higher mean?
An initial score of 3 or higher means your Thyroid Eye Disease is considered active. During this active inflammation phase, medical treatments like IV steroids or biologics are typically the most effective at putting out the 'fire'.
How does the EUGOGO system measure eye damage?
While CAS measures inflammation, the EUGOGO system measures the physical damage and severity of the disease. It categorizes your condition as mild, moderate-to-severe, or sight-threatening based on issues like constant double vision, eye bulging, and optic nerve compression.
What happens if my Thyroid Eye Disease is in the inactive phase?
When your disease becomes inactive, the inflammation has calmed down and your CAS drops below 3. At this stage, medications are less effective, so doctors usually focus on rehabilitative surgeries like orbital decompression to correct structural changes.
When is Thyroid Eye Disease considered a medical emergency?
The condition is a medical emergency if you develop sight-threatening symptoms, such as optic nerve compression or severe breakdown of the cornea. This requires immediate intervention to save your vision, regardless of your Clinical Activity Score.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What is my current Clinical Activity Score (CAS), and which specific symptoms contributed to it?
  2. 2.Based on my EUGOGO classification, am I in the 'moderate-to-severe' or 'sight-threatening' category?
  3. 3.Is my double vision considered 'intermittent' or 'constant,' and how does that change my severity ranking?
  4. 4.Since CAS can be subjective, are you using any other tools, like an MRI or ultrasound, to confirm if my disease is still active?
  5. 5.If my CAS is currently below 3 but I have significant bulging, should we focus on medical treatment or start planning for rehabilitative surgery?

Questions For You

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References

References (16)
  1. 1

    Updates on Treatment in Thyroid Eye Disease for the Neurologist.

    Alryalat SA, Alasheh A, Salim QA, Yaaqba N

    Neurologic clinics 2026; (44(2)):321-335 doi:10.1016/j.ncl.2025.12.002.

    PMID: 41922040
  2. 2

    The Role of Thermal Camera in the Assessment of Thyroid Eye Disease Activity.

    Prpic A, Kasumovic A, Guarro IG, et al.

    Acta informatica medica : AIM : journal of the Society for Medical Informatics of Bosnia & Herzegovina : casopis Drustva za medicinsku informatiku BiH 2023; (31(4)):260-264 doi:10.5455/aim.2023.31.260-264.

    PMID: 38379681
  3. 3

    Machine learning-assisted system using digital facial images to predict the clinical activity score in thyroid-associated orbitopathy.

    Moon JH, Shin K, Lee GM, et al.

    Scientific reports 2022; (12(1)):22085 doi:10.1038/s41598-022-25887-8.

    PMID: 36543834
  4. 4

    Gender differences in clinical presentation and prognosis of thyroid eye disease.

    Zloto O, Sagiv O, Priel A, et al.

    European journal of ophthalmology 2021; (31(5)):2717-2723 doi:10.1177/1120672120964112.

    PMID: 33158379
  5. 5

    Assessment of disease activity in Graves' orbitopathy.

    Potvin ARGG, Lacraru IC, Bisschop PH, et al.

    Frontiers in ophthalmology 2025; (5()):1697892 doi:10.3389/fopht.2025.1697892.

    PMID: 41384130
  6. 6

    Efficacy and safety of various Intravenous Methylprednisolone regimens in Moderate to Severe Thyroid Eye Disease: A systematic review.

    Aishwarya A, Shrivastava D, Singh AK, Agrawal R

    Indian journal of ophthalmology 2025; (73(8)):1100-1107 doi:10.4103/IJO.IJO_1808_24.

    PMID: 40719710
  7. 7

    Teprotumumab for the Treatment of Active Thyroid Eye Disease.

    Douglas RS, Kahaly GJ, Patel A, et al.

    The New England journal of medicine 2020; (382(4)):341-352 doi:10.1056/NEJMoa1910434.

    PMID: 31971679
  8. 8

    Teprotumumab and Orbital Decompression for the Management of Proptosis in Patients With Thyroid Eye Disease.

    Hubschman S, Sojitra B, Ghiam S, et al.

    Ophthalmic plastic and reconstructive surgery 2024; (40(3)):270-275 doi:10.1097/IOP.0000000000002563.

    PMID: 37972968
  9. 9

    Natural history of graves' orbitopathy after treatment.

    Menconi F, Leo M, Sabini E, et al.

    Endocrine 2017; (57(2)):226-233 doi:10.1007/s12020-016-1136-x.

    PMID: 27709471
  10. 10

    Thyroid eye disease: a review.

    Weiler DL

    Clinical & experimental optometry 2017; (100(1)):20-25 doi:10.1111/cxo.12472.

    PMID: 27701774
  11. 11

    Search for relevant indications for selenium supplementation in thyroid diseases.

    Wojciechowska-Durczynska K, Lewinski A

    Neuro endocrinology letters 2017; (38(4)):237-241.

    PMID: 28871707
  12. 12

    Insights into Current Management Strategies for Dysthyroid Optic Neuropathy: A Review.

    Tagami M, Honda S, Azumi A

    Clinical ophthalmology (Auckland, N.Z.) 2022; (16()):841-850 doi:10.2147/OPTH.S284609.

    PMID: 35330749
  13. 13

    Graves' Eye Disease: Clinical and Radiological Diagnosis.

    Hutchings KR, Fritzhand SJ, Esmaeli B, et al.

    Biomedicines 2023; (11(2)) doi:10.3390/biomedicines11020312.

    PMID: 36830848
  14. 14

    Tocilizumab use for optic nerve compression in thyroid eye disease: a prospective longitudinal cohort.

    Habroosh FA, Albrashdi SS, Alsaadi AH, Eatamadi H

    International ophthalmology 2024; (44(1)):222 doi:10.1007/s10792-024-03143-4.

    PMID: 38717530
  15. 15

    The 2021 European Group on Graves' orbitopathy (EUGOGO) clinical practice guidelines for the medical management of Graves' orbitopathy.

    Bartalena L, Kahaly GJ, Baldeschi L, et al.

    European journal of endocrinology 2021; (185(4)):G43-G67.

    PMID: 34297684
  16. 16

    Surgical Outcomes of Standardized Endoscopical Deep Medial Orbital Decompression in Dysthyroid Optic Neuropathy.

    Li C, Gao Y, Zhang Z, et al.

    Ophthalmic research 2024; (67(1)):39-50 doi:10.1159/000535330.

    PMID: 38109861

This page explains Thyroid Eye Disease scoring systems for educational purposes only. Always consult your ophthalmologist or endocrinologist to interpret your specific CAS and EUGOGO classifications.

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