Increased levels of ischemia-modified albumin in the aqueous humor (IMA AQH) can predict the progression of retinal nerve fiber layer (RNFL) thinning in the setting of glaucoma, according to results of a study published in Clinical Ophthalmology. The IMA AQH can identify these changes before the damage can be visualized using optical coherence tomography (OCT), researchers explain.
Patients (N=74) were recruited from the Jakarta Eye Center in Indonesia between January and June 2021. Patients with primary open angle glaucoma (POAG; n=20; mean age, 65±4.26 years; 78% men) and primary angle closure glaucoma (PACG; n=21; 64±6.67 years; 41.5% men) were age- and gender-matched with patients who had cataracts (n=33) and levels of IMA from serum and AQH were compared between glaucoma and control cohorts.
The POAG and PACG groups had intraocular pressures (IOP) of 31.90±6.67 and 14.67±2.67 mm Hg (P <.05), and RNFL thicknesses of 63.29±17.19 and 97.48±4.29 μm (P <.05), respectively.
The glaucoma and control cohorts did not differ for serum IMA levels (mean, 13.89 and 14.75 ng/mL) but the glaucoma patients did have elevated IMA AQH levels (mean, 14.89 vs 6.039 ng/mL; P <.05), respectively. Stratified by glaucoma type, the patients with POAG had a much higher IMA AQH level (mean, 17.33 ng/mL) than patients with PACG (mean, 12.69 nm/mL), both of which were significantly higher than controls (both P <.05).
Among patients with POAG, IMA AQH levels were positively correlated with IOP (r, 0.369; P =.049) and negatively correlated with RNFL thickness (r, -0.547; P =.013). Similarly, RNFL thickness was correlated with IMA AQH levels among patients with PACG (r, -0.473; P =.03).
In the univariate analysis, IMA AQH levels were associated with RNFL thinning among all patients with glaucoma (β, 0.388; P =.001) and those with POAG (β, 0.356; P =.013) or PACG (β, -0.473; P =.026).
The investigators observed that IMA AQH levels above 9.5 ng/mL with RNFL thickness below the normal range differentiated between glaucoma and healthy eyes with an area under the curve of 0.888, sensitivity of 81%, specificity of 85%, positive predictive power of 89.2% and negative predictive power of 76.3%.
The limitation of this study was the small sample size.
“IMA aqueous humor levels represent the state of intraocular local oxidative stress in glaucoma patients,” according to the researchers. “IMA AQH levels were found to increase with RNFL thinning in glaucoma. The value for the IMA aqueous humor level reference is 9.5 ng/mL as probable early diagnosis for glaucoma. This figure can be considered as a reference value for screening testing through the anterior chamber paracentesis method, especially in individuals with risk factors.”
Rusmayani E, Artini W, Sasongko MB, Suhardjo, Viona V. A novel biomarker in primary glaucoma: aqueous humor and serum levels of ischemia modified albumin (IMA). Clin Ophthalmol. 2022;16:4075-4087. doi:10.2147/OPTH.S388382