Glaucoma Grand Rounds

A 64-year-old white male presented with poorly controlled IOP and a five-year history of glaucoma. He had a 10-year history of bronchitis and a 40-year history of heavy cigarette usage. Current medications included Betimol (timolol hemihydrate) t.i.d. in each eye, 80mg aspirin every day, and an inhaler as needed. He is allergic to penicillin and sulfa.

Exam Findings
Corrected visual acuity was 20/20 O.U. External evaluation was negative with pupils at 4/4/2+/-MG. Extraocular motility movements were full, with confrontations intact to finger counting. The slit-lamp exam was positive for trace nuclear scleroses O.U. and pseudoexfoliation O.D. Gonioscopy showed ciliary body with mild pigmentation of the trabecular meshwork 360° O.U. Applanation tensions were 22mm Hg O.D., 16mm Hg O.S. at 11:30 a.m.

Visual fields showed no loss of sensitivity in either eye. A dilated fundus exam demonstrated cup-to-disc ratios of 0.6 O.D. and 0.4 O.S., with minimal thinning of the neuro-retinal rim in the right eye superiorly. The pulse rate was 64, and blood pressure 125/82 in the right arm. Respiration was labored and slightly accelerated.

Management
This patient presented with several issues that affect the clinical decision-making process. Foremost is the status of his respiratory system and the concurrent use of a beta-blocker (Betimol). While the patient doesn’t have a frank diagnosis of asthma or emphysema, his chronic bronchitis and prolonged use of cigarettes make him a prime candidate for respiratory distress. The labored breathing could be associated with the beta-blocker, and whether or not to continue it should be considered. Further, the patient’s sulfa allergy is significant because of possible reactions to oral and topical carbonic anhydrase inhibitors (CAIs).

Initially, I discontinued the Betimol and scheduled an IOP and respiratory function assessment in two weeks. At that time, the IOP had increased to 28mm Hg O.D., 19mm Hg O.S. at 12:45 p.m., but the patient reported significant improvement in respiration. I switched the patient to Xalatan (latanoprost) every evening O.D. and asked him to return in one month. It should be noted that even though the IOP was elevated in the right eye only, treatment must also be considered for the left. Due to the normal findings in the left eye and the considerable cost of Xalatan, however, I elected to monitor that eye for the time being.


After long-term Xalatan therapy, this patient showed decreased sensitivity in the inferior hemi-field (right) over his initial field test (left), suggesting that the therapy had become ineffective over time.

At the one-month visit, the IOP had dropped to 13mm Hg O.D., 18mm Hg O.S. at 1 p.m., and the patient was asymptomatic with the Xalatan. For the next 18 months, he was successfully managed with Xalatan.

Prostaglandin Loses Effectiveness
He missed his next visit and returned in six months, when his IOP was 25mm Hg O.D., and 18mm Hg O.S. at 10 a.m. Further, the visual fields showed an area of decreased sensitivity in the inferior hemi-field. The patient said he was regularly compliant. While it’s uncommon for a prostaglandin analog to become ineffective, it can. I discontinued the Xalatan for one week to test the drug’s efficacy.

At that visit, the patient’s IOP was relatively un-changed: 27mm Hg O.D., 17mm Hg O.S. at 2:15 p.m. I concluded that the Xalatan had decreased in effectiveness, resulting in an IOP increase sufficient enough to produce visual field changes. I then prescribed Alphagan (brimonidine tartrate) twice a day O.D., and scheduled a return visit in two weeks, when the patient’s IOP dropped to 15mm Hg O.D., 16mm Hg O.S. at 9 a.m. His pulse rate and blood pressure were unchanged. At follow-up visits, his visual fields were stable, and the IOP unchanged. His medical regimens stayed the same. This patient has shown progressive visual field loss at a relatively modest IOP elevation. Therefore, the goal IOP should be in the mid-teens.

This case is an excellent example of the pulmonary effects of beta-blockers and the long-term effectiveness of prostaglandins. While Xalatan has an excellent initial track record, it can lose its efficacy just like any other glaucoma agent and must be monitored.