Comparison of foveal morphology and clinical findings in patients with infantile nystagmus

Purpose: To compare the foveal morphology and the examination findings between the idiopathic infantile nystagmus group and the albinism-associated nystagmus group. Materials and Methods: Fifty two eyes of 26 patients with idiopathic infantile nystagmus and albinism-related nystagmus, and 28 eyes of 14 healthy individuals without nystagmus were prospectively evaluated between April 2022 and September 2022 at Ondokuz Mayıs University, Faculty of Medicine, Department of Ophthalmology. The patients were divided into three groups as idiopathic infantile nystagmus (IIN), albinism, and the control group. All patients were scanned with Optical Coherence Tomography (OCT). The best corrected visual acuity (BCVA) with a logMar chart, spherical and cylindrical refraction values, OCT findings, near and distant fusion, as well as the type, direction, waveform, and frequency of the nystagmus, and the amount of the deviation accompanying nystagmus were recorded. We examined the fovea morphology using the OCT scan findings to determine whether hypoplasia is present and correlated the degree of hypoplasia with clinical examination findings. Results: Of the patients in our study, 21 (52.5%) were male, and 19 (47.5%) were female. The mean age of the patients was 14.80 ± 9.18 years. We found a statistically significant difference of the nystagmus waveform distributions between the groups (p=0.002). The nystagmus waveform was pendular in 100% of the IIN group and 45.5% of the albinism group. A statistically significant difference in the distributions of the amplitude and frequency of nystagmus between the groups was observed (p=0.001, p=0.007, respectively). The nystagmus amplitude was high in 13.3% of the IIN group and 81.8% of the albinism group, and the nystagmus frequency was high in 46.7% of the IIN group and 100% of the albinism group. A statistically significant difference between the distributions of foveal hypoplasia according to the groups was found (p<0.001). Foveal hypoplasia was present in 33.3% of the IIN group and in 100% of the albinism group. While there was no significant difference in the distribution of strabismus between the control and IIN groups and between IIN and the albinism groups, there was a higher rate of strabismus in the albinism group compared to the control group (p=0.012). While the control group had the best stereopsis, half of the patients in the IIN group and none in the albinism group showed stereopsis. The difference between these three groups was statistically significant (p<0.001). According to the groups, median BCVA values of right and left eyes (p<0.001), right and left eye spherical mean values (p<0.001), right and left cylindrical median values (p=0.001; p<0.001, respectively), distribution of deviation (p=0.018) were statistically significant. According to these distributions, BCVA was highest in the control group and lowest in the albinism group, on the contrary, the number of refractive errors and the amount of deviation were the lowest in the control group and highest in the albinism group. When we compared the fusion status and stereopsis values between the groups, we found the best fusion and stereopsis in the control group and the worst fusion and stereopsis in the albinism group (p<0.001). There was a statistically significant positive high correlation between foveal hypoplasia and right and left eye logMAR visual acuity (VA) and spherical values (r=0.842; r=0.837; r=0.728; r=0.730 respectively; p<0.001). There was a statistically significant negative correlation between right and left eye cylindrical values (r=-0.517; p=0.001, r=-0.624; p<0.001, respectively). Conclusion: Patients with albinism-related nystagmus were associated with lower visual acuity, higher refractive errors, absence of stereopsis, and more severe foveal hypoplasia compared to patients with IIN. Keywords: Nystagmus, Albinism, Idiopathic infantile nystagmus, Foveal hypoplasia