The expanded range of choroidal thickness and retinal sensitivity asymmetry found in high myopia in the absence of disease is of relevance when exploring these patients for early signs of ocular pathology.

Inter-ocular asymmetry in anterior corneal high-order aberrations has previously not been investigated. This study aims to investigate the normal range of inter-ocular asymmetry in corneal high-order aberrations (HOAs) using a Placido disk-based corneal topographer to explore the relationship between the HOA parameters of the anterior corneal for each eye individually and the refractive error. Patients and Methods: A total of 257 subjects (98 males and 159 females) were participated, with an age range of 6 to 81 years (average of 40.2 ±17.53). Participants were divided into three groups: myopia (spherical equivalent (SEQ) of refraction ≥−0.50 D), hypermetropia (SEQ ≥+0.50 D), and emmetropia. For all patients, high-order aberrations were measured using a corneal topographer (CA.200TM; Topcon). Inter-ocular asymmetry was represented by RMS (root mean square) for three, five, and seven mm as pupil entry; aberrations for five mm pupil (vertical and oblique trefoil, vertical and horizontal comma, and primary spherical aberration) were recorded using the instrument's built-in software. Results: Hypermetropes exhibit the highest inter-ocular asymmetry of all RMS values, mostly in spherical aberrations, and higher-order trefoil values. Oblique trefoil aberrations had the highest interocular asymmetry in the myopic groups. The interocular asymmetry in horizontal coma values was the highest in emmetropes and the lowest in hypermetropes. Conclusion: To our knowledge, this is the first observational study of inter-ocular differences in high-order aberrations of the anterior corneal surface of the human eye. This study's results could be used to establish normal values of inter-ocular asymmetry of HOAs of the anterior cornea. The use of such normal values should be investigated further to serve as a guideline for clinicians when establishing the best management route for the patient's refractive error.

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AIM: To evaluate retinal parameters in a sample of healthy young Caucasian adults to define the normal or physiological range of inter-ocular asymmetry in this particular age and ethnic group. METHODS: Study sample consisted of 37 Caucasian children and young adults aged between 12 and 23y (spherical equivalent from -3.00 D to +4.00 D, anisometropia <0.5 D and axial length differences <0.3 mm). Normal inter-ocular asymmetry values were determined and 95% inter-ocular difference tolerance values were obtained. RESULTS: Statistically significant inter-ocular differences were found in mean (P=0.003) and superior (P=0.008) retinal nerve fiber layer (RNFL) thickness, as well as in central macular thickness (P=0.039), with larger values in the left eye in all instances, and with tolerance limits of inter-ocular asymmetry of -9.00 µm to 6.00 µm, -28.00 µm to 9 µm and -39.00 µm to 29.00 µm, respectively. In addition, statistically significant differences were found between males and females in mean thickness of the RNFL in the right eye (P=0.020). CONCLUSION: The exploration of the normal asymmetries of the retina may be an effective approach to further understand myopia onset and progression, which is particularly relevant in this age group. Differences in instrumentation and sample characteristics compromise direct comparison with published research and warrant the need for further studies.

Objective: To assess the normal range of interocular asymmetry in retinal and choroidal thickness in healthy emmetropic (as a control group) and ametropic subjects and to describe its relationship with anthropometric attributes. Methods: A Spectral-Domain Optical Coherence Tomography (SD-OCT) was performed on 586 patients to measure the thickness of the retina and choroid at the fovea as well as at 1, 2 and 3 mm nasally, temporally, superiorly, and inferiorly. In 95% confidence intervals, absolute interocular differences were calculated to determine the normal range of asymmetry and its relationship to Body Mass Index (BMI). Results: There was a statistically significant interocular difference in the choroidal thickness at 3 mm distance from the center inferiorly (Standardized Mean Difference (SMD): -17.33, 95% Confidence Interval (CI): -29.60 to -5.07 µm, P < 0.001) in the control group, and in the macular thickness at 2 mm distance from the center superiorly (SMD: -9.76, CI: -17.40 to 2.13 µm, P = 0.01) in the myopic group between underweight and overweight individuals. Conclusion: The expanded range of retinal and choroidal thickness asymmetry found in subjects with different BMI grades in the absence of disease is of relevance when exploring these patients for early signs of ocular pathology.