The Relationship Between Optic Disc Volume, Area, and Frisén Score in Patients With Idiopathic Intracranial Hypertension

Abstract

Purpose: To compare measurements of papilledema using fundus photography, optical coherence tomography (OCT), and Frisén score in patients with idiopathic intracranial hypertension (IIH).

Design: Retrospective, noncomparative analysis of randomized controlled trial data.

Methods: The Idiopathic Intracranial Hypertension Treatment Trial (IIHTT) evaluated weight management and treatment with acetazolamide compared with placebo in patients with IIH and mild visual loss. Among the 126 subjects in the IIHTT OCT substudy, fundus photographs and OCT scans of the optic disc were taken at baseline and at 6 and 12 months after enrollment. Trained readers scored each eye using a modified Frisén scale and measured the area of disc elevation. OCT scans assessed optic nerve head (ONH) volume. Correlations between volume and area were computed for both study and nonstudy eyes.

Results: Disc area and ONH volume were positively correlated at baseline (R² = 0.77 in study eyes, P < .001). Correlations between area and volume were similar in the treatment groups at baseline, but were weaker in the acetazolamide group compared with the placebo group at 6 months (R² = 0.25 vs R² = 0.76 in study eyes) and 12 months (R² = 0.19 vs R² = 0.65 in study eyes). At 6 and 12 months after enrollment, there was no consistent relationship between Frisén score, disc area, and ONH volumes in the acetazolamide group.

Conclusion: Frisén score fails to reflect the photographic area and OCT volume of papilledema after treatment with acetazolamide. Clinicians should use caution when using the Frisén scale to monitor the effect of treatment on papilledema over time.

Figure 1.

Disc Area and Volume Correlations in Subjects with Idiopathic Intracranial Hypertension. Correlation between disc area and ONH volume at baseline, 6 months, and 12 months in both study eyes and non-study eyes, independent of treatment group assignment. The correlation between area and volume was strongest at baseline, but remained positive and significant throughout the follow-up period (p<0.001 for all Pearson correlation coefficients).

Figure 2.

Disc Area and Volume Correlations in Subjects Receiving Acetazolamide Versus Placebo with Idiopathic Intracranial Hypertension. Among the placebo group at 6 months, there remained a strong positive correlation between disc area and ONH volume (R²=0.76, 0.77 in study and non-study eyes, respectively), and Frisén score appeared to correlate with these morphometric features. However, in the acetazolamide group, there was poor correlation between disc area and ONH volume (R²=0.25, 0.21 in study and non-study eyes, respectively), and Frisén score appeared to correlate weakly with these morphometric features. At 12 months, there was again a stronger correlation between ONH volume, disc areas, and Frisén score in the post-placebo group (R²= 0.65, 0.63) when compared to the acetazolamide group (R²= 0.19, 0.32).

Figure 3.

Relationship Between Frisén Score, Disc Area and Volume in Subjects Receiving Acetazolamide Versus Placebo with Idiopathic Intracranial Hypertension. Both study eyes and non-study eyes are included in each graph. In the placebo group at 6 months, eyes graded with higher Frisén scores had greater disc areas and ONH volumes. However, this relationship is weaker in the acetazolamide group at 6 months. At 12-months, there appears to be no clear association between Frisén score, ONH volume, and disc area in both the post-placebo and acetazolamide groups.