Findings from a recent study published in BMC Ophthalmology evaluated the association between ABO and Rh blood groups with retinal structural indices, including macular thickness and peripapillary retinal nerve fiber layer (RNFL) thickness.
Break this down for me.
Blood type is a genetically determined trait that previous studies have suggested can be a risk factor for vascular diseases.
Some retinal diseases (retinal detachment [RD], age-related macular degeneration [AMD], and diabetic retinopathy [DR]) also have genetic linkages.
Further, retinal structures, such as peripapillary RNFL and macular thickness, have genetic influences.
- What this suggests: A theoretical relationship between blood type, retinal diseases, and retinal structural indices.
Talk about the study.
In this cross-sectional study, investigators conducted convenience sampling at a tertiary referral eye hospital in Tehran, Iran.
Note: Convenience sampling is a non-probability sampling technique where experimental inclusion is determined because patients are the easiest for the researcher to access.
How was the data collected?
The research team:
- Referred study participants to a hospital laboratory to test their blood groups
- Performed ocular examinations including
- Measurement of visual acuity
- Auto-refraction
- Subjective refraction
- Slit-lamp biomicroscopy
- Carried out retinal imaging using spectral-domain optical coherence tomography (SD-OCT) under dilated pupillary conditions
Findings?
In total, 328 patients (219 [60.7%] female, mean age: 63.29 ± 5.57 years) were recruited for the study.
The research team found the following associations between blood type and retinal structural indices:
- Blood type B
- Decreased global peripapillary RNFL thickness
- Decreased sectoral peripapillary RNFL thickness in the superior and inferior quadrants
- Blood type AB
- Decreased peripapillary RNFL thickness in the superior quadrant
Conversely, blood type O was linked with thicker global peripapillary RNFL thickness—and superior and inferior quadrant peripapillary RNFL thickness—compared to other ABO blood groups.
What about macular thickness?
The average and central macular thickness was significantly thicker in the AB group compared to other blood groups.
In addition, the average macular thickness was significantly thinner in the Rh+ group compared to the Rh- group.
Clinical implications?
The study authors noted that the link between ABO blood groups with macular and peripapillary RNFL thicknesses may suggest that:
- Blood type could be considered in the clinical interpretation of macular thickness, particularly for people with blood type AB, to avoid misdiagnosis
- Considering inherent peripapillary RNFL thinning, caution should be taken when interpreting abnormal reports in individuals with blood type B to avoid false positive diagnoses of optic neuropathy
- People with blood type B may be more susceptible to significant peripapillary RNFL loss and advanced glaucomatous damage due to an inherently thin peripapillary RNFL
Limitations?
Limitations of the study included the:
- Hospital-based nature of the study—which potentially reduced the generalizability of the findings
- Sampling method that may have added bias
- Study population, as the analysis was performed on an elderly population, so the conclusions may not be applicable to other groups
Take home.
These findings indicate that retinal structural indices (i.e., peripapillary RNFL and macular thickness) may be related to blood groups—implying a genetic linkage.
However: Due to the lack of consistency between related studies, larger trials are required to elucidate the effect of ABO and Rh grouping on peripapillary RNFL and macular thickness.