Evaluation of the association between subconjunctival orbital fat prolapse and thyroid-associated orbitopathy
Sang Beom Han
Department of Ophthalmology, Kangwon National University Hospital, Kangwon National University Graduate School of Medicine, Chuncheon, Korea
I read with interest the article entitled “Subconjunctival orbital fat prolapse and thyroid associated orbitopathy: a clinical association” by Chatzistefanou et al.1 The case-series study was undoubtedly well designed and conducted, in which the authors successfully revealed that subconjunctival orbital fat prolapse may occasionally be a predominant clinical manifestation of thyroid-associated orbitopathy (TAO) and suggested that the presence of subconjunctival orbital fat prolapse can alert the diagnosis of thyroid orbitopathy.
However, I would like to point out that the mechanism underlying the association between the two conditions is still unclear. Subconjunctival fat prolapse is usually caused by forward herniation of intraconal fat tissue due to dehiscence of tenon capsule precipitated by aging process or trauma.2 In TAO, swelling and inflammation of orbital fat can lead to separation of the orbital septum from the capsulopalpebral fascia, which can cause fat prolapse into the orbit.3 Previous studies showed that intraorbital inflammation in TAO can lead to apical crowding in orbit and intracranial fat prolapse.4,5 Therefore, as the authors postulated, it would be plausible that elevated intraorbital pressure and increase in orbital fat in TAO can also allow anterior herniation of intraorbital fat.
Klio I Chatzistefanou,1 Christianna Samara,2 Ioannis Asproudis,3 Dimitrios Brouzas,1 Marilita M Moschos,1 Elisabeth Tsianta,1 George Piaditis4
1First Department of Ophthalmology, National and Kapodistrian University of Athens Medical School, Athens, Greece; 2Department of Radiology and Endocrinology, 3Department of Ophthalmology, University of Ioannina, Ioannina, Greece; 4Athens General Hospital “G. Gennimatas”, Athens, Greece
We appreciate Dr Han’s comments and interest in our article. Intracranial herniation of intraorbital fat through the superior orbital fissure has been reported at an incidence of 19% in patients with thyroid ophthalmopathy in one study,1 and its prevalence may vary between 24% and 82% in different studies1–3 among patients with dysthyroid ophthalmopathy.
We reviewed again data from the patients’ charts for symptoms and signs of compressive optic neuropathy upon presentation with subconjunctival fat prolapse.4 There were no afferent pupillary defects or optic nerve head swelling or atrophy noted on fundoscopy in any of the patients reported in this series. Clinical suspicion for possible compressive optic neuropathy, prompting paraclinical investigation with visual field testing, had been raised for patient #2 who had a slight decrease in visual acuity to 0.9 in the right eye. Visual field testing by automated perimetry was within normal limits. Visual acuity improved to 1.0+ in the involved eye with a change in astigmatic correction.
View original paper by Chatzistefanou et al
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