Abstract Purpose. To evaluate the effect of an intraocular gas bubble on ocular wall pulsation. Methods. Eight patients that underwent vitrectomy with intraocular gas injection for various reasons were studied. Ocular pulsation was evaluated in a semi-quantitative way by means of Goldman applanation tonometry in both eyes before and after the operation. Vitreous cavity gas fill in the operated eye was estimated by means of indirect ophthal- moscopy and was correlated with ocular pulsation. The follow up lasted until the gas totally disappeared. Results. Ocular pulsation disappeared postoperatively in the operated eye and gradually reappeared when the gas fill diminished. Pulsation returned to preoperative level when the gas disappeared from the vitreous cavity. A negative statisti- cal correlation between ocular pulsation and gas fill could be documented. Conclusion. The compressible nature of the intraocular gas bubble results in absorption of the vascular pulsation and prevents its transfer to the ocular wall. This leads to attenu- ation or even cancellation of ocular wall pulsation when a gas bubble exists within the eye. Keywords: vitreoretinal surgery; ocular pulsation; gas; blood flow; hemodynamics Introduction Ocular wall pulsation is the result of the pulsatile blood inflow to the eye. The incoming bolus of blood results in a slight expansion of the eye that is detected as ocular pulsa- tion, synchronous with the heart rate. 1,2 Ocular pulsation becomes possible because the eyeball behaves as an elastic system. In normal conditions the structure that determines the elasticity of the eyeball is the eye wall (choroid, cornea and mainly sclera); most of the structures that comprise the interior of the eye such as vitreous, aqueous and lens are incompressible and not elastic. 3 In many vitreoretinal proce- dures, however, air or other gases are injected into the vitre- ous cavity and remain there postoperatively for various amounts of time. In these situations, the elastic characteris- tics of the eye change dramatically, as gases are highly com- pressible. In the current study, we evaluated the effect that the presence of intraocular gas has on the pulsatility of eyes after vitrectomy. Methods Patients in this study were operated upon in the University Eye Clinic of Heraklion between September and December 2000. Corneal pulsation was evaluated by means of Goldman applanation tonometry on eyes which received an intraocu- lar gas injection as part of a vitreoretinal procedure. During classic applanation tonometry the movement of the semi- circles was evaluated and graded as absent (0), slight (1), obvious (2) and prominent (3). In total, 8 patients were included in the study. All of them exhibited preoperative pulsation grade 3 in both eyes. Preoperative diagnosis, oper- ation performed, and gas used in the study individuals are listed in Table 1. Two patients received air and the rest C3F8. Received: July 13, 2001 Accepted: April 16, 2002 Correspondence: Miltiadis K. Tsilimbaris, MD, Assist. Prof. of Ophthalmology, Univ. of Crete Medical School, PO Box 1352, Heraklion, Crete, GR 711 10, Greece. Tel: 30-81-392352, Fax: 30-81-392730, E-mail: tsilimb@med.uoc.gr Attenuation of ocular wall pulsation in eyes containing a gas bubble after vitrectomy Miltiadis K. Tsilimbaris, Harilaos Ghinis, George Kounis, George Kimionis and Ioannis G. Pallikaris VEIC, Dept. of Ophthalmology, Univ. of Crete Medical School, Heraklion, Crete, Greece Current Eye Research 0271-3683/02/2403-202$16.00 2002, Vol. 24, No. 3, pp. 202–205 © Swets & Zeitlinger Part of this work was presented at the ARVO Annual Meeting, Fort Lauderdale, FL, USA, 2001.