Direct orbital manometry in patients with thyroid-associated orbitopathy.
OBJECTIVE
To determine orbital tissue tension and orbital compartment compliance in patients with and without thyroid-associated orbitopathy (TAO).


METHODS
Prospective case series.


METHODS
Orbits of patients with TAO (18 orbits) and control patients without TAO (35 orbits) were studied.


METHODS
An orbital manometer was designed to directly measure orbital tissue tension in patients undergoing ocular or orbital surgery.


METHODS
Tissue tension was recorded before, during, and for 5 minutes after a 5-ml retrobulbar injection of anesthetic. Orbital compliance was calculated as change in volume divided by change in tissue tension.


RESULTS
Resting orbital tissue tension was 4.4 +/- 2.2 mmHg (mean +/- SD) in normal orbits and 9.7 +/- 4.8 mmHg in orbits of TAO patients (P = 0.0005) Following retrobulbar injection, orbital tissue tension rose to 12.0 +/- 3.6 mmHg (P = 0.0000000000000006 compared with baseline) in the control group and to 36.3 +/- 15.2 mmHg in the TAO group (P = 0.0000007 compared with baseline, and P = 0.000008 TAO group versus control group). Orbital compartment compliance was 0.80 +/- 0.50 ml/mmHg in the control group and 0.27 +/- 0.21 ml/mmHg in the TAO group (P = 0.00001). Resting orbital tissue tension in 8 TAO orbits with compressive optic neuropathy was 12.4 +/- 4.9 mmHg, and was 7.8 +/- 3.5 mmHg in 10 orbits of TAO patients without compressive optic neuropathy (P < 0.05). No adverse events occurred.


CONCLUSIONS
Retrobulbar injection causes consistent measurable changes in orbital tissue tension. Orbital manometry safely demonstrated higher orbital tissue tension and lower orbital compartment compliance in the orbits of TAO patients versus those of normal subjects. Resting orbital tissue tension was higher in the orbits of TAO patients with compressive optic neuropathy than in those orbits without. Compressive optic neuropathy may partially result from an orbital compartment syndrome in some patients with TAO. Directly assessing orbital dynamics in vivo may prove useful as an adjunct in the clinical evaluation of patients with TAO and other orbital disorders.
Division of Ophthalmology, Cleveland Clinic Foundation, Ohio 44195, USA.
C D
CD
Riemann
J A
JA
Foster
G S
GS
Kosmorsky
D000368:Aged; D000772:Anesthesia, Local; D005260:Female; D006111:Graves Disease / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D008297:Male; D008365:Manometry / Q000379:methods*; D008875:Middle Aged; D009884:Ophthalmodynamometry; D009915:Orbit / Q000503:physiopathology*; D011312:Pressure; D011446:Prospective Studies