A recent study published in BMC Ophthalmology evaluated ganglion cell complex (GCC) thickness in patients taking oral hydroxychloroquine (HCQ).
Give me some background.
HCQ is a widely prescribed drug for treating several rheumatologic and dermatologic disorders, including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).
The ocular connection: Retinal toxicity is a notable side effect of HCQ use, with potentially irreversible sequelae such as:
- Bull’s eye maculopathy
- Irreversible loss of visual acuity (VA)
- Color vision defects
- Central scotoma
The overall prevalence of hydroxychloroquine retinopathy is 7.5%, which can vary with daily consumption and duration of use.
Bring in the GCC.
As the drug accumulates in the cytoplasm in retinal ganglion cells (RGCs), it can cause cell shrinkage and irregular cell body formation, eventually leading to RGC degeneration.
Because the structural and functional damage at later stages is irreversible, early screening for HCQ retinopathy and baseline screening for pre-existing maculopathy are crucial.
- Moreover: Spectral-domain optical coherence tomography (SD-OCT) shows localized thinning of retinal layers in the parafoveal zone and may reveal retinal toxicity at an earlier stage before VF loss or any retinal signs appear.
Now talk about the study.
In this hospital-based, cross-sectional, non-interventional, comparative study, the research team recruited 87 eyes of 87 patients (88.5% female, mean duration of use: 3.4 years) taking HCQ.
- The predominant diagnosis among patients receiving HCQ was SLE (47.2%), RA (40.2%), and Sjögren’s syndrome (3.4%).
All patients underwent complete ophthalmological evaluation along with dilated fundus examination and were divided into two groups based on the duration of HCQ use:
- Group 1: 62 patients taking HCQ < 5 years
- Mean HCQ dosage: 216.12±45.06 mg/day
- Group 2: 25 patients taking HCQ ≥ 5 years
- Mean HCQ dosage: 228±61.37 mg/day
Plus: Age- and gender-matched healthy volunteers (n = 87) with normal ocular findings were utilized as controls.
How was GCC thickness measured?
Using the RTvue XR Avanti SD-OCT, the research team collected the following GCC parameters:
- Average GCC thickness
- Superior GCC thickness
- Inferior GCC thickness
- Focal loss volume (FLV)
- Global loss volume (GLV)
Findings?
The average, superior, and inferior GCC thicknesses were significantly reduced in both Group 1 ( < 5 years) and Group 2 ( ≥ 5 years) compared to controls (p < 0.001).
In Group 1 the mean GCC values were lower compared to controls as follows:
- Group 1 average GCC thickness: 94.70±6.34μm
- Control average GCC thickness: 99.79±4.61μm
- Group 1 superior GCC thickness: 94.43±6.28μm
- Control superior GCC thickness: 99.38±4.63μm
- Group 1 inferior GCC thickness: 94.74±6.81μm
- Control inferior GCC thickness: 99.97±4.61μm
Likewise: In Group 2, mean GCC thicknesses were 92.70±6.39μm (average), 92.44±5.92μm (superior), and 93.32±7.25μm (inferior)—all of which were significantly lower than in controls (listed above, p < 0.001).
What about focal and global loss volume?
FLV and GLV in Group 1 were 1.76±2.5% and 4.07±3.27%, respectively, which were significantly higher than in controls (0.72±0.45% and 1.39±1.1%, respectively, p = 0.002 for FLV and p = 0.001 for GLV).
While there was significantly elevated GLV in Group 2 (4.46±4.42%, p = 0.003), the difference in FLV (1.23±1.12%) was not statistically significant compared to controls (p = 0.077).
Expert opinion?
The study authors highlighted the “potential value of GCC measurements as a sensitive indicator of retinal changes linked to HCQ use and emphasized the significance of tracking GCC thickness in patients undergoing HCQ therapy.”
Limitations?
These included:
- The inability to conduct a longitudinal follow-up in the study, which limited the ability to assess changes in GCC thickness over time or establish a causal relationship between HCQ and retinal thinning
- GCC thickness was measured only superiorly and inferiorly; measuring GCC thickness in all four quadrants would have provided more detailed information.
Take home.
These findings demonstrate that GCC thickness was significantly thinner in patients taking HCQ.
Further: Elevated FLV and GLV percentages were observed in these patients, suggesting potential retinal structural alterations associated with HCQ use.
- However: No statistically significant correlation was observed between GCC thickness and duration of HCQ use.