Our study aimed to quantify the thickness of RNFL and its correlation with the clinical characteristics of migraine. A statistically significant decrease of RNFL thickness of all quadrants bilaterally was detected in the patients of migraine compared to healthy control, these findings were consistent with different previous studies, Abdelatif and his colleague documented a decrease at all quadrants of retinal nerve fiber layer of the eye of migrainous patients .
Other studies demonstrated that the nasal peripapillary RNFL (pRNFL) diameter of positive aura patients was less than control group, as thinner nasal pRNFL quadrant was more prone to neurodegeneration [23, 24].
In addition, Yurtoğullari and colleagues found that the thickness of temporal, inferotemporal pRNFL quadrants of the positive aura group, and both of the supero and inferotemporal pRNFL thickness of the negative aura group was thinner than the control group . Similarly, Aksoy and his colleagues reported a remarkable difference in the thickness of temporal pRNFL quadrant compared to healthy control .
Although OCT-based measurements of RNFL thickness showed different results, most of the data revealed that there is affection of multiple quadrants based on heterogeneous pathophysiologic mechanism of migraine attributed mainly to the neurovascular theory with the activation of trigeminovascular system release of inflammatory and vasoactive neuropeptides from peripheral nerve endings extracranially at the eye causing inflammatory compromise and vasospasm of ophthalmic, retinal and posterior ciliary arteries with hypoperfusion and axon loss resulting in decreased RNFL diameter [24, 25].
On the contrary, a few studies in the literature did not observe any changes in the diameter of RNFL of migrainous patients when compared to control group. These notifications was explained by using different methodology and the possibility of higher-normal RNFL values of the examined migraine patients, that affect the final data of comparative results [27, 28].
In our presented study there was no significant difference in RNFL thickness in migraine patients with aura compared to patients without aura in all retinal quadrants similarly Simsek et al. found no difference between the two categories of migrainous patients .
On the other hand, a study reported a significant decrease in the inferior and nasal quadrants thickness of migraine patients with aura than migraine patients without aura .
There is a multifactorial part in migraine patients that can be studied, so we studied (headache intensity, frequency, duration of the attacks and the disease duration) and its correlation to RNFL thickness. We found that thinning of RNFL at left inferior and nasal retinal part was associated with intense headache. Also, thinning of RNFL at right superior quadrant was associated with more nausea and less tolerability through patient assessment with MIGSEV scale.
Similarly, other studies found that thinning of RNFL at inferior, nasal, and temporal retinal quadrants was associated with intense headache [22, 30].
The present study replicates the previous results that found no significant correlation between the RNFL thicknesses of all quadrants bilaterally and any of the disability, frequency and duration of attacks or the disease duration [17, 31, 32].
On contrary, Reggio et al. mentioned that more frequent migrainous attacks were associated with thinning of the RNFL . Another author reported central macular thinning in migraine patient with aura who had frequent attacks .
A study led by Martinez et al. found that the thickness of the RNFL at temporal quadrant had a negative correlation with the migraine disability assessment score (MIDAS), frequency of attacks, and the duration of migraine . Also, Feng and colleagues clarified that the finding of marked decrease in the mean value of RNFL thickness was attributed to longer duration of migraine that can exceed 15 years .
The discrepancy between the previous studies and our data can be explained by using different scale to assess migraine, small sample size, less frequent attacks and shorter disease duration less than 15 years reported by our patients.
The main limitations of this work were the small sample size, and the lack of vascular assessment of the retina using OCT angiography, and the lack electrophysiological assessment of the retina using electroretinography.