Evaluation of Retinal Nerve Fiber Layer Thickness in Acromegalic Patients Using Spectral-Domain Optical Coherence Tomography

Purpose: To evaluate retinal nerve fiber layer (RNFL) thickness in acromegalic patients. Methods: A study group of 29 patients with acromegaly and a control group of 38 age-matched healthy individuals were enrolled in a cross-sectional study. The study group was further divided by tumor size into two subgroups, a macroadenoma group and a microadenoma group. Serum growth hormone (GH) and insulin-like growth factor-1 (IGF-I) levels were detected at the time of ophthalmological examination in the study group. In both the study and control group, the RNFL thickness in the four quadrants was measured by optical coherence tomography. The relationship between GH and IGF-I levels and RNLF thickness was also evaluated. Results: The difference in mean RNLF thickness in all quadrants between the study and control groups was not statistically significant. In acromegalic patients with macroadenoma, the mean RNLF thickness of the inferior quadrant decreased significantly compared to both patients with microadenoma and healthy individuals (p?=?0,032 and p?=?0,046). GH and IGF-1 levels were not significantly correlated with the RNLF thickness in the study group. Conclusions: Excessive GH and IGF-1 levels do not affect the optic nerve or RNLF thickness, whereas the RNLF becomes thinner in the inferior quadrant in acromegalic patients with macroadenoma as a result of the chiasmal compression.     

Variability in Spectral-Domain Optical Coherence Tomography over 4 Weeks by Age

Purpose: To quantify variation in spectral-domain optical coherence tomography (SD-OCT) measures of total retinal thickness (top of inner limiting membrane to top of retinal pigment epithelium, RPE) and RPE thickness measures over a 4-week period and by age.

Methods: A total of 76 volunteers aged 40–85 years were seen at three visits over 4 weeks. Two Topcon SD-OCT scans were taken at each visit. Following grid re-centration, total retinal and RPE thickness were determined in nine subfields. Multilevel modeling was used to quantify variance between scans and by age.

Results: In the central circle, mean total retinal thickness was 237.9 µm (standard deviation, SD, 23.5 µm) and RPE thickness was 46.0 µm (SD 5.3 µm). Intraclass correlation coefficient in the central circle was 0.988 for total retinal thickness and 0.714 for RPE thickness. Pairwise measures taken within 4 weeks were strongly correlated (p > 0.95). Within-subject variation of total retinal thickness increased significantly with age. Subjects in the oldest age group had significantly increased among- and within-subject variability in measures of RPE thickness.

Conclusions: Correlation between retinal thickness measures was very high (>0.95) over a period of 4 weeks with small changes likely due to variation in measurement. Increasing variability in total retinal and RPE thickness measures with age suggest that the use of more and/or higher quality images to calculate mean thickness to reduce variability may benefit the study of these measures in older persons. This may also impact sample size calculations for future studies of SD-OCT measures in older adults.