Secondary bony decompression rescued proptosis and vision after fat decompression alone

Design

retrospective interventional case series over 12 years at a tertiary university hospital

Population

27 eyes of 17 patients having secondary inferomedial orbital wall decompression after primary fat decompression for Graves' orbitopathy

Primary outcome

change in Hertel exophthalmometry and best corrected visual acuity

Effect

proptosis reduced 4.5 ± 2.1 mm (21.7 to 17.3 mm, P<0.001) over mean 40.6 months; acuity in dysthyroid optic neuropathy 0.43 to 0.12 logMAR (P=0.005); diplopia in 12 of 17 patients (70%)

Orbital fat decompression avoids the bone work and its diplopia, but it does not always deliver enough. This 12-year series from a tertiary centre reports 27 eyes in 17 patients who needed secondary inferomedial orbital wall decompression after a primary fat decompression - 15 eyes in nine patients for recurrent proptosis, and 12 eyes in eight for dysthyroid optic neuropathy.

The primary fat decompression had achieved 3.4 mm of proptosis reduction. The secondary bony procedure achieved a further 4.5 ± 2.1 mm, taking Hertel measurements from 21.7 to 17.3 mm (P<0.001) over a mean follow-up of 40.6 months. In the patients with dysthyroid optic neuropathy, best corrected visual acuity improved from 0.43 to 0.12 logMAR (P=0.005) - roughly from 6/18 to 6/7.5 equivalent.

The cost is in the abstract's least prominent sentence: diplopia occurred in 12 of 17 patients, 70%, including five with new-onset diplopia, and preoperative diplopia predicted postoperative diplopia. Twenty-seven eyes from a single centre is a small series with no comparison group, so this cannot say whether a staged fat-then-bone approach is better than primary bony decompression. What it does establish is that the second operation works when the first was not enough - and that the consent conversation for it has to lead with a seven in ten chance of double vision.

• Offer secondary inferomedial wall decompression where fat decompression has left residual proptosis or optic neuropathy - it delivered a further 4.5 mm
• Lead the consent conversation with diplopia: it affected 70%, and new-onset diplopia occurred in about a third of patients
• Ask specifically about pre-existing diplopia - it predicted postoperative diplopia
• Plan for strabismus assessment and possible squint surgery as part of the pathway, not as a rescue
• Note that vision improved substantially in dysthyroid optic neuropathy, which is the indication where the trade-off is clearest

Why it matters

It quantifies the second operation for the patients in whom the deliberately conservative first one did not do enough.

Don't overread it

A retrospective single-centre series of 27 eyes with no comparison group - it does not establish that staged fat-then-bone decompression is preferable to primary bony decompression.

The statistics, in plain English

With 27 eyes from 17 patients, eyes from the same person are not independent observations, which makes the P values less informative than they look. The proptosis reduction of 4.5 ± 2.1 mm has a wide standard deviation, so individual results ranged considerably. The acuity improvement from 0.43 to 0.12 logMAR in dysthyroid optic neuropathy is large and clinically obvious, but with no control arm there is no way to separate it from the natural course of treated thyroid eye disease.

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