Change in Intraocular Pressure in the Fellow Eye After Glaucoma Surgery in 1 Eye Sushmita Kaushik, MD, Aniruddha Agarwal, MD, Savleen Kaur, MD, Neiwete Lomi, MD, Srishti Raj, MD, and Surinder S. Pandav, MD Purpose: To measure the change in intraocular pressure (IOP) of the fellow eye after glaucoma surgery in 1 eye. Patients and Methods: In this prospective interventional study, 71 patients with primary and secondary glaucoma, undergoing glau- coma surgery in 1 eye were included. The IOP in the fellow eye following glaucoma surgery in 1 eye from the first postoperative week till 6 months following surgery was studied. Both normal and glaucomatous fellow eyes were included. IOP change from pre- operative IOP levels in the fellow eye was analyzed. Patients treated with acetazolamide preoperatively were analyzed separately. Results: The mean baseline IOP of the operated and fellow eyes was 28.14 ± 9.4 and 16.5 ± 6.1 mm Hg, respectively. IOP of fellow eyes significantly increased compared with baseline at all timepoints (P < 0.001), with a maximum rise 6 weeks postoperatively (4.8 ± 3.3 mm Hg). There was no significant difference in the consensual rise between glaucomatous and nonglaucomatous fel- low eyes, or between patients treated with or without acetazola- mide before surgery. Regression analysis showed no baseline factor associated with the rise in IOP. By the sixth postoperative month, 24 patients required surgery or needed an increase in medications in the fellow eye for IOP control. Conclusions: Glaucoma surgery in eye is associated with a rise in IOP of the fellow eye, regardless of whether the fellow eye is normal or glaucomatous, or had been previously treated with acetazola- mide. Fellow eyes of all patients scheduled for glaucoma surgery require careful monitoring of the IOP. Key Words: contralateral intraocular pressure, glaucoma surgery, trabeculectomy, ophthalmic consensual reaction, other eye IOP (J Glaucoma 2015;00:000–000) I n 1924 Weekers 1 sscoined the term “consensual oph- thalmotonic reaction” to describe the corresponding pressure change in the contralateral eye after alteration of the intraocular pressure (IOP) in 1 eye. Postulated mecha- nisms suggest involvement of neuronal, hormonal, and cytokine regulation of aqueous flow dynamics, but the exact mechanism is yet to be elucidated. 2,3 A consensual response to antiglaucoma therapy has been shown in normal and glaucomatous subjects, 4–9 fol- lowing uniocular tomography 10 and a small decrease has also been reported in the untreated fellow eye after laser trabeculoplasty. 11–13 Gibbens 14 reported that the con- sensual ophthalmotonic reaction appears to occur in man regardless of the drug used to lower IOP in the treated eye. This was, however, later refuted by Newman et al 15 who reported reduction in contralateral untreated eyes only with timolol and not prostaglandins or carbonic anhydrase inhibitors. The response of the fellow eye IOP to trabeculectomy in 1 eye is even more uncertain. Reports in literature are conflicting, 16–18 and it is difficult to draw concrete con- clusions chiefly because of the variability and inconsistent methodology of the studies. The fellow eyes reported were normal and glaucomatous, unoperated and operated, and on treatment and without treatment. The aim of the present study was to see the behavior of the IOP in the unoperated normal and glaucomatous fellow eye when 1 eye underwent glaucoma surgery, to see if the presence of glaucoma in the fellow eye altered the response in anyway. METHODS This study was undertaken at a tertiary care referral institute. Patients who required surgical reduction of IOP and presented between August 2012 and January 2013were prospectively enrolled. The Institute Ethics Committee approval was obtained (NK/562/Res/2327) and the study adhered to the tenets of the declaration of Helsinki. Informed consent was obtained from all recruited patients. Patients scheduled for trabeculectomy or glaucoma drainage device implantation [Ahmed Glaucoma Valve, Model FP7; New World Medical Inc., CA or Aurolab Aqueous Drainage Implant (AADI); Aurolab, Madurai, India] in 1 eye, were included. They all had inadequate IOP control on maximally tolerated medical therapy. Patients with both primary and secondary glaucoma were included, where the other eye was glaucomatous or normal, respec- tively. Fellow eyes with a history of laser treatment for glaucoma such as laser iridotomy or trabeculoplasty or any intraocular surgery were excluded. Only glaucomatous fel- low eyes on medical treatment were included in the study. Patients with concurrent ocular or systemic disease (apart from glaucoma) in either eye such as uveitis and/or pre- vious surgery requiring steroids; diabetes, hypertension (those receiving systemic b-blockers); or vascular occlusions were excluded. Details of topical and systemic anti- glaucoma medications prescribed were recorded. All eligible patients underwent a comprehensive oph- thalmologic examination of both eyes including best-cor- rected visual acuity in LogMAR units, IOP measured by Goldmann Applanation Tonometry, slit-lamp biomicro- scopy, gonioscopy, and stereoscopic fundus evaluation on the slit-lamp using a 90.0 D lens. An average of 3 IOP Received for publication April 22, 2014; accepted November 27, 2014. From the Advanced Eye Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India. Disclosure: The authors declare no conflict of interest. Reprints: Sushmita Kaushik, MD, Advanced Eye Centre, Post Grad- uate Institute of Medical Education and Research, Chandigarh 160012, India (e-mail: sushmita_kaushik@yahoo.com). Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/IJG.0000000000000217 ORIGINAL STUDY J Glaucoma  Volume 00, Number 00, ’’ 2015 www.glaucomajournal.com | 1 Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of the article is prohibited.