Congenital Microcoria: Clinical Features and Molecular Genetics

ITPR1: The missing gene in miosis-ataxia syndrome?

The association of early-onset non-progressive ataxia and miosis is an extremely rare phenotypic entity occasionally reported in the literature. To date, only one family (two siblings and their mother) has benefited from a genetic diagnosis by the identification of a missense heterozygous variant (p.Arg36Cys) in the ITPR1 gene. This gene encodes the inositol 1,4,5-trisphosphate receptor type 1, an intracellular channel that mediates calcium release from the endoplasmic reticulum. Deleterious variants in this gene are known to be associated with two types of spinocerebellar ataxia, SCA15 and SCA29, and with Gillespie syndrome that is associated with ataxia, partial iris hypoplasia, and intellectual disability. In this work, we describe a novel individual carrying a heterozygous missense variant (p.Arg36Pro) at the same position in the N-terminal suppressor domain of ITPR1 as the family previously reported, with the same phenotype associating early-onset non-progressive ataxia and miosis. This second report confirms the implication of ITPR1 in the miosis-ataxia syndrome and therefore broadens the clinical spectrum of the gene. Moreover, the high specificity of the phenotype makes it a recognizable syndrome of genetic origin.

Rare micropupil secondary to congenital cataract surgery favoring the development of the affected eye: a case report

BACKGROUND

Congenital microcoria has been extensively reported and usually leads to visual dysfunction or blindness. However, micropupil development secondary to cataract surgery has never been reported. Here, we describe a rare case of micropupil development in infancy that occurred secondary to combined cataract extraction and intraocular lens implantation for treatment of congenital cataract. When the patient reached adulthood, the affected eye not only gained good vision but also showed better ocular development and refractive status than the fellow eye.

CASE PRESENTATION

A 17-year-old boy presented to our outpatient clinic with decreased vision in his left eye related to congenital cataract surgery at 6 months of age. The affected eye had exhibited a pinhole pupil since the third month postoperatively. The condition had been managed with observation and regular monocular occlusion treatment. Upon presentation to our clinic, the best-corrected visual acuity (BCVA) in his fellow eye was 0.0 logMAR(20/20) with a refraction of - 5.75 diopters cylinder/-2.25 diopters sphere, and the BCVA in his affected eye was 0.5 logMAR(20/40) with a refraction of 0.00 diopters. Ophthalmic examination of the affected eye revealed a pinhole pupil (approximately 0.5 mm) with high light reflex sensitivity but no response to pupil-dilating drugs. The patient underwent pupilloplasty of the affected eye under corneal surface anesthesia. Postoperative examination revealed better ocular development in the affected eye than in the fellow eye (axial length: 24.21 vs. 27.02 mm, respectively) as well as better refractive status in the affected eye (BCVA of 0.0 logMAR(20/20) with a refraction of - 2.23 diopters cylinder/-3.00 diopters sphere vs. 0logMAR(20/20) with a refraction of -5.75 diopters cylinder/-2.25 diopters sphere).

CONCLUSIONS

We have reported a rare case of micropupil development secondary to congenital cataract surgery, which is an uncommon complication, especially in children. However, unlike congenital microcoria, the secondary pinhole pupil may have reduced imaging haze and halos, possibly favoring the development of the affected eye. This case provides further insight into the treatment of congenital cataract.

Different rules for binocular combination of luminance flicker in cortical and subcortical pathways

How does the human brain combine information across the eyes? It has been known for many years that cortical normalization mechanisms implement 'ocularity invariance': equalizing neural responses to spatial patterns presented either monocularly or binocularly. Here, we used a novel combination of electrophysiology, psychophysics, pupillometry, and computational modeling to ask whether this invariance also holds for flickering luminance stimuli with no spatial contrast. We find dramatic violations of ocularity invariance for these stimuli, both in the cortex and also in the subcortical pathways that govern pupil diameter. Specifically, we find substantial binocular facilitation in both pathways with the effect being strongest in the cortex. Near-linear binocular additivity (instead of ocularity invariance) was also found using a perceptual luminance matching task. Ocularity invariance is, therefore, not a ubiquitous feature of visual processing, and the brain appears to repurpose a generic normalization algorithm for different visual functions by adjusting the amount of interocular suppression.

A rare case of congenital pupillary abnormality: a case report

BACKGROUND

Congenital anomalies of the pupil are quite varied, including abnormal size, shape, color, response to stimulus, and function. We are here reporting an unusual case presented with the absence of pupillary opening with folds of iris tissue at the center. Only an extremely small pupil (diameter < 0.5 mm) could be observed during the operation.

CASE PRESENTATION

A 15-year-old male patient visited our outpatient clinic due to vision difficulty in his right eye for more than ten years. The best-corrected visual acuity was 2.0 logMAR and 0 logMAR for the right and left eye, respectively. There were amblyopia, astigmatism and constant exotropia in his right eye. Ophthalmic examination of the right eye showed flat iris root, minimal iris pigmentation, and the pupil area was entirely covered by iris tissue. Lens status and fundus evaluation could not be commented. The left eye was found to be within normal limit. Based on ophthalmic examination, the admission diagnosis was given as acorea. Pupilloplasty was performed on the right eye due to the situation that the iris tissue blocked the visual axis, which led to visual impairment and stimulus deprivation amblyopia. However, an extremely small pupil at the center of his pupillary area was observed during the operation. The postoperative course was favorable, and a normal pupil was secured. Hospital discharge diagnosis was given as microcoria, and amblyopia treatment was followed.

CONCLUSIONS

We report a rare case of congenital pupillary abnormality. The further diagnosis was given as microcoria, which should be differentiated from acorea. For this kind of pupil disorder which blocks the visual axis, early diagnosis and treatment can help prevent the development of stimulus deprivation amblyopia.