High IOP due to complete gas fill of the anterior chamber following vitrectomy for vitreomacular traction (VMT)

Poster Details

First Author: D.Sahota UK

Co Author(s):    N. Glover                             

Abstract Details


To raise awareness of a rare aetiology of increased IOP following vitrectomy with gas. In this case S2F6 gas completely filled the anterior chamber causing pupil block and resulting in the emergency presentation of the patient. We describe the mechanism of the pathology and the subsequent recommended treatment.


Emergency presentation to eye casualty of a 54 year old lady with extreme right eye pain and vomiting. Patient had bilateral pseudophakia and had undergone vitrectomy with gas for VMT 2 days prior to presentation.


Patient presented out of hours with sudden onset right eye pain and vomiting 2 days post-op. She described a heavy pressure, 10/10 pain with minimal relief from simple analgesia. She was reviewed by the on-call ophthalmologist who noted a right injected eye and IOP 54T19. This raised IOP was treated with latanoprost, dorzolamide/timolol, iopidine all to the right eye STAT and 500mg IV acetazolamide. IOP was rechecked 90 minutes later and measured 55T17. At this point she was noted to have a hyper-deep anterior chamber (AC) and the iris detail appeared to have abnormal appearance. The AC was noted to be devoid of any aqueous and had 100% gas fill. The decision was made to perform AC paracentesis to release the gas and relieve the pressure.


After STAT doses of oxybupricaine and povidone iodine and a speculum placed to the right eye, patient was positioned on the slit lamp. 25G (0.5mm diameter) orange needle was used with bevel facing away from patient, entering at the limbus temporally at the right eye. On entering the eye, there was a gush of aqueous from the posterior chamber into the AC until the AC was filled with aqueous roughly 50%, up to the paracentesis site. The superior 50% of the AC remained filled with gas but the pupil block was relieved (photo available). The patient felt an immediate relief in symptoms and IOP check was 28T15. Patient was continued on topical drops and oral acetazolamide and had no further IOP rises up to point of follow-up after the paracentesis (one month).


IOP increase following vitrectomy is relatively common (incidence reported as up to 67% in some publications). The mechanism is divided between open angle and closed angle. In open angle it is usually due to intraocular gas expansion or inflammatory trabecular meshwork obstruction. Closed angle cases are less common but are usually due to pupillary block; gas bubbles are able to cause iridocorneal apposition. In the case presented here we have the rare phenomenon of pupillary block co-existing with an open angle in a pseudophakic patient. The gas completely filled the AC, possibly via forward migration of the gas via weak zonules although this is only postulated. The pupillary block was relieved by AC paracentesis. Some case series examining post-vitrectomy IOP rise show the incidence of surgery needed to lower IOP in as many as 11% of patients. Prompt pressure-lowering is required to minimise the possibility of secondary glaucoma. It is therefore crucial in emergency presentations of high IOP post-vitrectomy to diagnose the mechanism of the IOP rise. In this case we demonstrate that AC paracentesis is able to relieve pupillary block in a patient with complete gas fill of the AC post-vitrectomy and lower IOP to a safer level.

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