Cataracts may skew retinal nerve fiber layer thickness measurements taken with OCT

J Glaucoma. 2011;20(1):37-43.

Significant progressive cataracts may reduce signal strength and retinal nerve fiber layer thickness measurements acquired with optical coherence tomography, a study showed.

"Peripapillary RNFL thickness measurements should be interpreted with caution in glaucomatous eyes with significant cataract, particularly if the [signal strength] is attenuated," the study authors said. "Cataract extraction with IOL implantation improves the [signal strength] and thereby results in a thicker OCT measurement of RNFL."

The prospective study included 45 eyes; 23 eyes had concomitant glaucoma.

Cross-sectional scans of peripapillary RNFL were obtained with the Stratus OCT (Carl Zeiss Meditec).

Results showed that postoperative RNFL thickness was 9.3% higher and signal strength was 24.1% higher than preoperative measurements. Patients with lower preoperative RNFL measurements had a greater postoperative change in thickness measurements and signal strength; the difference was statistically significant (both P < .001).

Preoperative and postoperative RNFL thickness measurements were not significantly different in eyes with preoperative signal strength higher than 6. Conversely, there were significant differences between preoperative and postoperative signal strength and between preoperative and postoperative RNFL thickness in cases in which preoperative signal strength was lower than 6.

Data showed no significant differences in the degree of change in RNFL thickness change or signal strength between eyes with cataract only and those with cataracts and glaucoma.

There was no significant relationship between changes in IOP and RNFL thickness, the authors said.