Response of filtered eyes to digital ocular pressure

Purpose: To examine the effect of digital ocular pressure (DOP) on the intraocular pressure (IOP) of eyes 3 months or longer after successful glaucoma filtering surgery. Methods: Fifteen patients participated in this study. Each had one eye with a successful filtering operation (IOP ≤ 21 mmHg without medications) and a fellow eye that was not operated on, which served as a control. The authors measured IOP in both eyes before and serially after DOP until return to baseline or for 3 hours to determine the amounts and durations of reductions. The authors monitored changes of bleb morphology and searched for complications. Results: Digital ocular pressure 3 months or more after successful filtering surgery reduced IOP by approximately 50% of baseline. The time after DOP for 50% of eyes to have intraocular pressure return to within 2 mmHg of baseline was 95 minutes; 40% recovered within 20 minutes and 30% had not recovered by 3 hours. Eyes with localized blebs recovered faster than did eyes with diffuse blebs. Transient shallowing of the anterior chamber developed in one eye. Otherwise, there were no adverse effects. Time since surgery and baseline IOP were not correlated with response. Fellow eyes had minimal response to DOP and recovered within 30 minutes. Conclusion: This study shows that a substantial, transient decrease of IOP after DOP occurs in glaucomatous eyes with a well-functioning bleb 3 months to 6 years after filtering surgery. The duration exceeds 90 minutes in more than 50% of the eyes tested and 180 minutes in more than 30% of the eyes tested.