Contrast Sensitivity Function May Enable Dysthyroid Optic Neuropathy Detection

In early dysthyroid optic neuropathy (DON), a change in contrast sensitivity function (CSF) may indicate visual impairment, according to a study published in Eye and Vision.

Researchers enrolled patients with thyroid-associated ophthalmopathy (TAO; n=81), including individuals with and without DON (n=31; mean age, 48.1 years; 22 women and n=50; mean age, 45.7; 32 women, respectively), and 24 control group participants (mean age, 45.2 years; 17 women) in the investigation, which occurred between February and September of 2021. The study participants underwent best corrected visual acuity, biomicroscopic, and exophthalmometry assessment. The research team performed optical coherence tomography-angiography (OCT-A) and obtained ganglion cell complex layer (GCCL), and superficial and deep retinal capillary plexus (SRCP and DRCP, respectively) imaging and compared outcomes among the 3 groups. 

The CSF did not differ between control group participants and patients with TAO who did not have DON at 1.0 and 1.5 cpd (both P >.05). However, individuals without DON had significantly lower CSF than control group individuals at 3.0, 6.0, 12.0, and 18.0 cpd (all P <.001). The DON cohort had significantly lower CSF than the control group at all spatial frequencies (all P <.001).

OCT-A assessment revealed varying SRCP densities among the 3 groups (P <.001), in which control group participants had a higher density (mean, 46.59%) compared with individuals without DON (mean, 45.01%; P <.05) and participants with DON (mean, 41.90%; P <.05). No difference in GCCL thickness was noted between individuals without DON and control group participants, but individuals with DON had a thinner GCCL thickness compared with both control group participants (P =.008) and patients without DON (P =.001).

Participants’ GCCL thicknesses and SRCP densities were significantly associated (r, 0.334; P =.002), according to the report. Univariate analysis revealed that the area under the log contrast sensitivity function (AULCSF) among patients with TAO was associated with spherical equivalent, muscle index, SRCP, and CGGL (all P ≤.045). 

Among individuals with TAO, AULCSF had the greatest ability to differentiate between patients with and without DON (DON: area under the curve [AUC], 0.831; P <.001; no DON: AUC, 0.987; P <.001), the report shows.

“The CSF was significantly reduced even in TAO patients without other clinical signs of DON and could be a sensitive and effective endpoint for assessing visual impairments of TAO patients at risk for DON,” according to the study authors. “In addition, we found that reduced CSF was significantly correlated with decreased SRCP density in the early stage of DON, suggesting that reduced microvascular density around the macula may be one of the most important factors related to early visual impairments before the appearance of obvious orbital apex crowding in TAO.”

Study limitations include failure to include individuals with advanced DON. 

Disclosure: One study author declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.