This randomized, double-masked, placebo-controlled study concluded that taking acetazolamide in combination with a low-sodium weight-reduction diet yielded a modest improvement in visual function in patients with idiopathic intracranial hypertension (IIH) and mild visual loss.
The authors note that the clinical importance of this improvement remains to be determined and that while acetazolamide is commonly used to treat IIH, there is an insufficient evidence base for its use.
An accompanying editorial by Dr. Jonathan Horton, MD, PhD, discusses the importance of the study and poses additional questions regarding the management of these patients that will need to be addressed by future studies.
He notes that while the improvement measured in the study, in perimetric mean deviation (PMD), was statistically significant (P = 0.05), it was subtle, less than the 1.3 dB treatment effect predicted. However, only patients with mild vision loss could be enrolled, because treatment with a placebo could not be justified in individuals with more serious vision loss, and patients with mild vision loss have little room to improve and therefore any treatment effect will be modest.
He concludes that having enrolled only patients with mild disease, it was impressive that the investigators still managed to uncover evidence for a statistically significant benefit from acetazolamide and that the clinical importance of the study will be greatest for patients with severe papilledema.
Participants included 165 subjects with IIH and mild visual loss enrolled at 38 locations who were on a low-sodium weight-reduction diet. They had PMD between −2 dB and −7 dB. They were randomized to the maximally tolerated dosage of acetazolamide (up to 4 g/d) or matching placebo for six months.
The mean improvement in PMD was greater with acetazolamide at six months than with placebo, as was the mean improvement in papilledema grade (P < 0.001). The treatment effect on PMD was greater in participants with a papilledema grade of 3 or more at baseline, which may be due to more affected eyes having more capacity for improvement. Additionally, patients taking acetazolamide experienced a significantly greater reduction in weight and showed greater improvement in quality of life.