Aspirin Use in Advanced Uncontrolled Glaucoma

Management of Anticoagulation and Antiplatelet Therapy in Glaucoma Surgery

The use of antithrombotic therapy is rising as the population of older adults grows and novel agents with wider indications emerge. Likewise, surgical treatment of glaucoma may become increasingly common as the prevalence of glaucoma increases and innovative treatment options are developed. These trends highlight the need to understand how best to manage antithrombotic therapy in the context of glaucoma surgery. This review article describes current literature on antithrombotic therapy and perioperative thromboembolic risk evaluation based on individual factors. In addition, guidance is offered on the management of antithrombotic therapy in the setting of each type of glaucoma surgery, with an emphasis on a multidisciplinary approach involving the patients' treating physicians.

Anticoagulation therapy in glaucoma surgery

PURPOSE

To identify the practices of ophthalmologists when undertaking glaucoma surgery on patients concurrently using warfarin or acetylsalicylic acid (aspirin).

METHODS

A questionnaire was designed to examine perioperative management of patients being treated with warfarin and aspirin prior to and during glaucoma surgery. The questionnaire was posted with stamped self-addressed envelopes to all glaucoma specialists registered on a glaucoma shared care scheme database.

RESULTS

Of the 93 eligible participants, 64 returned a completed questionnaire, representing a response rate of 68.8%. Twenty-one surgeons (32.8%) routinely stopped warfarin before surgery. Mean time prior to surgery of drug cessation was 4 days (range 2-7). Three surgeons (14.3%) routinely commenced heparin if they stopped warfarin. Ten (47.6%) never used heparin, while the remaining eight (38.1%) would use heparin depending upon the indication for anticoagulation. Forty-two surgeons (81.25%)were happy to operate only at an INR < or =3 at the time of surgery. The remainder (18.75%) were happy to operate at higher INRs, including two surgeons (3.1%) who would operate at any level. Twenty surgeons (31.2%) routinely stopped aspirin before surgery, while the rest did not. Of those who stopped aspirin, the mean time prior to surgery was 7.1 days (range 4-14 days).

CONCLUSIONS

The majority of surgeons do not stop warfarin or aspirin prior to glaucoma surgery. There is a great diversity in current practice with regard to the management of anticoagulant therapy prior to glaucoma surgery amongst glaucoma surgeons in England. Currently there is little information available to offer definitive guidance.

Effect of statin drugs and aspirin on progression in open-angle glaucoma suspects using confocal scanning laser ophthalmoscopy

PURPOSE

To determine the effect of statins and aspirin on the rate of progression of optic nerve parameters in open-angle glaucoma (OAG) suspects, as defined by confocal scanning laser ophthalmoscopy (CSLO).

METHODS

Data of OAG suspects who had undergone at least two CSLO tests at the Beckman Vision Center at UCSF from January 2001 to June 2006 was collected. We conducted a retrospective chart review of 149 eyes from 76 patients considered suspect for glaucoma based on a cup-to-disc ratio >0.5, but with normal intraocular pressures (IOP) and visual fields. Subjects included glaucoma suspects who took statin drugs or aspirin for greater than 23 months. The control group consisted of suspects who never used statins or aspirin. The data were analysed using mixed effects regression.

RESULTS

When comparing controls with the statin group there were significant differences in the progression of multiple CSLO parameters per year, including rim volume (-13.7% controls, +26.7% statin only; P = 0.0156), retinal nerve fibre layer cross-sectional area (-12.2% controls, +24.3% statin only; P = 0.0051), and mean global retinal nerve fibre layer thickness (-10.3% controls, +26.6% statin only; P = 0.0114), with adjustment for age, gender, race, IOP, central corneal thickness, refractive error and multiple systemic comorbidities. No significant differences were found when comparing subjects taking a statin plus aspirin or aspirin alone with the controls.

CONCLUSIONS

Statin drugs may be associated with slowed progression of optic nerve parameters in glaucoma suspects as measured by CSLO.

The effect of aspirin and warfarin therapy in trabeculectomy

AIM

The management of patients on antiplatelet and anticoagulation therapy (APACT) in glaucoma surgery currently has no specific recommendations. We aimed to establish the risk of haemorrhagic complications and surgical outcome in patients on APACT in glaucoma surgery.

METHODS

We retrospectively examined 367 consecutive trabeculectomies performed between 1994 and 1998. Preoperatively 60 (16.4%) patients were on APACT (55 on aspirin and five on warfarin). The incidence of hyphaema and haemorrhagic complications between patients with and without APACT was documented. Surgical success was defined in two categories as an intraocular pressure (IOP) <21 mmHg and an IOP <16 mmHg 2 years following trabeculectomy with and without antiglaucoma medication.

RESULTS

None of the patients on aspirin suffered significant intra or postoperative haemorrhage. Aspirin was associated with a significantly higher risk of hyphaema (P=0.0015) but this was not found to significantly affect IOP control at 2 years. Patients on warfarin suffered haemorrhagic complications and trabeculectomy failure.

CONCLUSIONS

Aspirin appears to be safe to continue with during trabeculectomy. Patients on aspirin have an increased risk of hyphaema following trabeculectomy. This however does not appear to affect surgical outcome. Warfarinised patients are at risk of serious bleeding complications. They require careful monitoring pre- and postoperatively and are at risk of trabeculectomy failure.

Therapeutic potentials of aspirin in glaucomatous optic neuropathy

Glaucoma is a common blinding disease worldwide. Although traditionally considered as a disease of elevated intraocular pressure, it is now clear that glaucoma is primarily a distinctive optic neuropathy with many proposed pathogenic mechanisms. Impaired blood flow resulting in ischemia has been proposed to be involved in the retinal ganglion cell loss seen in glaucoma. Aspirin might improve optic nerve head perfusion by stabilizing microcirculatory flow. Evidence also indicates that apoptosis may be the final common pathway for ganglion cell death in glaucoma. Aspirin has been shown to exhibit neuroprotective properties. Prostaglandins play an important role in the regulation of intraocular pressure. Aspirin is well known to inhibit cyclooxygenase mediated prostaglandin synthesis. The NSAID-inhibition of PGs synthesis up-regulates the concentration prostaglandin receptors in retinovascular tissues. Based on the body of evidence implicating ocular blood flow disturbances, apoptotic cell death, and also the role of prostaglandins in the pathogenesis of glaucoma we hypothesize that aspirin could be potentially useful drugs in the treatment of glaucoma. Hypothetical pathophysiologic mechanisms explaining potential beneficial effects of aspirin on glaucomatous optic neuropathy include: increasing optic nerve blood flow, preventing retinal ganglion cell death through neuroprotective mechanisms, and upregulating prostaglandin receptors.