In patients with idiopathic intracranial hypertension and mild vision loss, adding oral acetazolamide to a low-sodium weight loss diet improved visual field function more than diet alone, researchers reported. The study was published online April 22 in JAMA.
Perimetric mean deviation (PMD) – the primary outcome measure – differed by less than 1 dB between the two groups, reported Dr. Michael Wall of the University of Iowa Hospitals and Clinics in Iowa City and his associates with the Neuro-Ophthalmology Research Disease Investigator Consortium (NORDIC). The clinical relevance of the difference "remains to be determined," the investigators said.
The researchers randomized 165 patients with idiopathic intracranial hypertension and mild vision loss (PMD, –2 to –7 dB) to oral acetazolamide or placebo. Patients received up to 4 g acetazolamide twice daily. Initial doses were increased until papilledema grade fell below 1 on the Frisén scale and PMD improved to at least –1 dB in both eyes. Both groups also followed a diet and lifestyle modification program, according to the investigators (JAMA 2014;311:1641-51[doi:10.1001/jama.2014.3312]).
Baseline PMD was –3.53 dB in both groups. At 6 months, PMD averaged –2.10 dB in the acetazolamide group and –2.82 dB in the placebo group (treatment difference, 0.71 dB; 95% CI, 0- 1.43 dB; P = .050).
The acetazolamide group also had greater mean improvements in papilledema grade (treatment effect, –0.70; 95% CI, –0.99 to –0.41; P less than .001) and vision-related quality of life on the VFQ-25 (Visual Functioning Questionnaire–25) survey tool (treatment effect, 6.35; 95% CI, 2.22-10.47; P = .003). And the treatment group lost 4.05 kg more weight than the exercise-only group (95% CI, –6.27 to –1.83 kg; P less than .001), the researchers said. A statistical mediation analysis showed that most of the effect of acetazolamide on PMD was not due to weight loss, they reported.
However, the functional importance of specific decibel improvements in PMD are poorly understood, Dr. Wall and his associates noted. "Our chosen minimal clinically important difference for PMD was 1.3 dB and was based on a small pilot study designed to estimate the level of decibels at which a clinician makes a decision to change therapy," they said. "Our estimated treatment effect was only approximately half of this value."
The acetazolamide group was significantly more likely to develop paresthesia, dysgeusia, fatigue, decreased carbon dioxide level, nausea, vomiting, diarrhea, and tinnitus than the exercise-only group, the investigators reported. "No participant, to our knowledge, experienced permanent morbidity from receiving acetazolamide," they added.
The National Eye Institute funded the study. Two coauthors reported receiving personal fees from Teva Pharmaceutical Industries, which produces generic acetazolamide.