Paradoxical pupillary responses in congenital stationary night blindness

Phenotypes and genotypes underlying paradoxical pupillary reaction in children

Paradoxical pupillary reaction (initial pupillary constriction to darkness) has been most associated with the inherited retinal disorders congenital stationary night blindness and achromatopsia. However, underlying genotypes and associations with other pediatric retinal phenotypes are not well documented. A retrospective review for paradoxical pupillary reaction was performed at the Ocular Genetics Clinic of Cleveland Clinic Abu Dhabi (2016-2020). Four children from 4 different families were identified, all of whom had had genetic confirmation of the clinical diagnosis. Associated pathogenic variants were in TRPM1 (biallelic; two boys; congenital stationary night blindness), CABP4 (biallelic; one boy, congenital cone-rod synaptic disorder) and PAX2 (monoallelic; one girl, papillorenal syndrome). Genetically confirmed affected relatives of the 2 probands with TRPM1-related congenital stationary night blindness did not show the phenomenon. This study documents novel genotypes and phenotypes that can be associated with paradoxical pupillary reaction in children and confirms potential intrafamilial variable expressivity for the phenomenon.

Congenital Nystagmus and Its Congeners

In recent years, we have made enormous strides in elucidating the phenomenology of congenital nystagmus. The purpose of this review is to briefly summarize our current understanding of congenital nystagmus in terms of its clinical symptomatology, pathophysiology, differential diagnosis, and ancillary testing, and clinical management. Finally, this discussion provides the reader with an armamentarium of clinical pearls to facilitate diagnosis of the numerous sensory visual disorders that can underlie congenital nystagmus.

Transient pupillary light reflex in CEP290- or NPHP5-associated Leber congenital amaurosis: Latency as a potential outcome measure of cone function

Mutations in photoreceptor cilium genes CEP290 and NPHP5 cause a form of Leber congenital amaurosis (LCA) which typically lacks rods but retains central cones. The current study evaluated the transient pupillary light reflex (TPLR) as an objective outcome measure to assess efficacy of ongoing and future therapies. Eleven eyes of six patients selected for retained cone function were tested with TPLR using full-field stimuli in the dark-adapted state. Stimuli were red or blue with 1 s duration and spanned a 6-log unit dynamic range. TPLR response amplitude was quantified at fixed times of 0.9 and 2 s after stimulus onset and TPLR latency was defined as the time to reach 0.3 mm constriction. Full-field stimulus testing (FST) and static perimetry were used to correlate subjective perception with objective TPLR parameters. TPLR and FST thresholds with both red and blue stimuli were abnormally elevated in patients to near -1.25 log phot-cd·m-2 consistent with the lack of rods. TPLR latencies were delayed on average but showed some differences among patients. Remnant extrafoveal vision was correlated with faster TPLR latencies. Our results support the use of a short TPLR protocol with full-field red stimuli of 0.7 log phot-cd·m-2 or brighter as an objective and convenient outcome measure of cone function in CEP290- and NPHP5-LCA. The latency parameter of the TPLR would be expected to show a detectable change when an intervention modifies cone sensitivity in the extrafoveal region.

Don't Miss This! Red Flags in the Pediatric Eye Exam: Pupils

The pupillary exam in the pediatric population is a vital part of any clinician's workup. In the right clinical setting, pupillary abnormalities such as anisocoria, light-near dissociation, an afferent pupillary defect, and paradoxic pupillary constriction in the dark can be red flags that trigger further examination and workup. Through both careful physical examination and detailed history-taking and observation, potentially vision- and life-threatening conditions can be detected.

Disinhibition of intrinsic photosensitive retinal ganglion cells in patients with X-linked congenital stationary night blindness

PURPOSE

To assess the pupil light response (PLR) to chromatic stimulation in patients with different types of X-linked congenital stationary night blindness (CSNB).

METHODS

Eight patients with CSNB due to CACNA1F and NYX mutations were exposed to blue and red light stimuli, and PLR was evaluated using infrared video pupillography. Pupil responses were compared between CSNB patients and healthy subjects (n = 34) at baseline, at maximum of constriction, for post-illumination pupil responses (PIPR) and the slope of redilation using Cohen's d. A subgroup comparison was performed descriptively between CACNA1F and NYX associated CSNB patients using the same parameters.

RESULTS

In CSNB, smaller baseline pupil diameters compared to healthy subjects were measured both before blue and red light stimulation (d = 1.44-1.625). The maximum constriction to blue light stimuli was smaller for the CSNB group compared to healthy subjects (d = 1.251) but not for red light stimuli (d = 0.449). Pupil response latencies were prolonged in CSNB for both light stimuli (d = -1.53 for blue and d = -1.011 for red stimulation). No relevant differences were found between the CSNB group and healthy subjects for PIPR (d = 0.01), but the slope of redilation was smaller for CSNB patients (d = 2.12). Paradoxical pupil constriction at light offset was not seen in our patients.

CONCLUSION

A reduced redilation and smaller baseline pupil diameters for patients with CSNB indicate a disinhibition of intrinsically photosensitive retinal ganglion cells due to affected post-photoreceptor transduction via bipolar cells and can explain the pupillary behavior in our patient group.

Marshall M. Parks Memorial Lecture: Ocular Motor Misbehavior in Children: Where Neuro-Ophthalmology Meets Strabismus

Clinical diagnosis has been supplemented by neuroimaging advances, genetic discoveries, and molecular research to generate new neurobiological discoveries pertaining to early maldevelopment of ocular motor control systems. In this focused review, I examine recent paradigm shifts that have transformed our understanding of pediatric ocular motor disease at the prenuclear and infranuclear levels. The pathogenesis of complex ocular motor disorders, such as paradoxical pupillary constriction to darkness, benign tonic upgaze of infancy, congenital fibrosis syndrome, and the constellation of unique eye movements that accompany Joubert syndrome, are elucidated.

Disorders of the pupil

Pupil size is determined by the interaction of the parasympathetic and the sympathetic nervous system. The parasympathetic system conducts the light reaction with its major center in the dorsal midbrain. The sympathetic nervous system acts either directly on the dilator muscle (peripherally) or centrally by inhibiting the Edinger-Westphal nucleus. Psychosensory reactions are transmitted via the sympathetic system. The afferent input of the light reflex system in humans is characteristically wired, allowing a detailed analysis of a lesion of the afferent input. Even in humans a subgroup of ganglion cells containing melansopsin plays an important role as a light sensor for the pupillary system. To diagnose normal pupillary function, pupils need to be isocoric and react bilaterally equally to light. Anisocoria indicates a problem of the efferent pupillary pathway. Pupillary disorders may involve the afferent pathways (relative afferent pupillary defect) or the efferent pathways. Physiological anisocoria is a harmless condition that has to be distinguished from Horner's syndrome. In this case pharmacological testing with cocaine eye-drops is helpful. Disorders of the parasympathetic system will impair the light response. They include dorsal midbrain syndrome, third-nerve palsy, and tonic pupil. Tonic pupils are mainly idiopathic and do not need imaging. Disorders of the iris, including application of cholinergic agents, need also to be considered in impaired pupillary light reaction.

Pingelapese achromatopsia: correlation between paradoxical pupillary response and clinical features

AIM

To evaluate the paradoxical pupillary constriction in darkness in patients with Pingelapese achromatopsia (PA), and to describe a connection between this phenomenon and the clinical features.

METHODS

27 patients with PA were examined. All underwent a full ophthalmic examination which included Snellen visual acuity and ophthalmoscopy. Colour vision examination was performed with Ishihara pseudoisochromatic plates and also with a colour plate consisting of five basic colours (red, green, purple, yellow, and orange). Paradoxical pupillary response was examined and documented with a special infrared video camera. Pupils' images were analysed using the Scion Image program and the ratio of pupil size in darkness to its size in light was calculated and recorded.

RESULTS

Mean visual acuity was 20/400 (range 20/80-20/800). Colour vision examination showed a mean of 3.2 (SD 1.5) (range 1-5) of Ishihara colour plates, and 0.5 (0.75) (0-3) of basic colour plates. 23 patients (85%) had paradoxical pupillary constriction in darkness. Mean dark/light ratio of pupillary area was 0.86 (range 0.5-1.6). In patients with marked paradoxical pupillary constriction there was a significant correlation of visual acuity and Ishihara score.

CONCLUSIONS

Clinical manifestations of achromatopsia include total colour blindness, low visual acuity (mean of 20/400), horizontal pendular or rotatory nystagmus, and photophobia. Most patients have paradoxical pupillary constriction in darkness. When this response is brisk it seems to correlate with lower visual acuity and lower Ishihara score.

The infant with nystagmus, normal appearing fundi, but an abnormal ERG

Many retinal disorders present during infancy with nystagmus, decreased vision, and normal-appearing fundi, but an abnormal ERG. The most common of these disorders are Leber's congenital amaurosis, achromatopsia, and congenital stationary night-blindness. Other disorders with similar ocular manifestations may be associated with a variety of life-threatening systemic abnormalities. This review describes the clinical, electrophysiological, and laboratory findings that can be used to distinguish among these conditions.

Visual sensory disorders in congenital nystagmus

Congenital nystagmus (CN) is a common disorder indicative of a primary disturbance of the ocular motor or visual sensory systems. The authors prospectively evaluated 81 patients with CN, structurally normal eyes, and minimal or no abnormalities of the optic nerve, macula, and retinal pigment epithelium (RPE). Seventy-four (91%) patients were found to have a disorder of the visual sensory system. Thirty-four patients had albinism, 37 had a congenital or early onset disorder of the retinal photoreceptors, and 3 had abnormalities of the optic nerve. The remaining seven (9%) patients had motor CN. Most patients presenting with CN have visual loss and should be evaluated for an underlying disorder of the visual sensory system.

X-linked congenital stationary night blindness with myopia and nystagmus without clinical complaints of nyctalopia

Seven of eight patients presented initially or were followed for decreased acuity and nystagmus without complaints of night blindness. The diagnosis of congenital stationary night blindness was established with electroretinogram and dark adaptation testing. Careful electrodiagnostic testing is needed to provide accurate genetic counseling. Two patients showed pupillary constriction to darkness which is a sign of retinal disease in young patients.

Photoreceptor responses of patients with congenital stationary night blindness

The present study examines the hypothesis that the electroretinogram (ERG) a-wave of patients with congenital stationary night blindness with myopia (CSNB) is solely cone mediated. The subjects include four patients with x-linked recessive inheritance, two patients with no family history, and thirteen age-matched normal subjects. Because normal subjects have relatively large b-waves (which can influence the measurement of the PIII component of the a-wave), the main response parameter studied was the slope of the a-wave. The results for the CSNB patients show that in the light adapted condition, the ratio of the responses to photopically balanced blue and red flashes was nearly unity; whereas, in the dark-adapted condition, the ratio was ~3 times greater. The ratios for the normal subjects were similar to those of the CSNB patients. These results lead to the conclusion that, in patients with CSNB, the ERG a-wave is not solely mediated by cones.

Pupillary constriction to darkness

Patients with congenital achromatopsia and congenital stationary night blindness have been known to show a transient pupillary constriction to darkness. We examined 50 normal subjects and 108 patients with retinal and optic nerve dysfunction to see if any had an initial pupillary constriction to darkness. We used a new infrared television apparatus. Four patients with congenital stationary night blindness, four with achromatopsia, two with bilateral optic neuritis, and one with dominant optic atrophy showed the phenomenon. In the patients who showed this unusual pupillary response to darkness it was the first observable event every time the lights were turned off. The constriction could usually be seen with a handlight, and it was similar in latency to the normal pupillary dilatation to darkness. Pupillary constriction to darkness is a clinically valuable sign that can be used in the detection of congenital retinal disease in children with poor vision.

Paradoxical pupil in congenital achromatopsia

Children with congenital achromatopsia possess an interesting paradoxical pupillary constriction to darkness that has not been previously described. This paper describes three children in whom this paradoxical pupillary reaction was documented with infrared pupillometry. The literature on the pupil in achromatopsia is reviewed and a tentative testable model of the reaction is hypothesized.