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Age Impairs Corneal Sensitivity and Reflex Tearing in Congenital Aniridia
María Carmen Acosta1, Annamária Náray2,3, Mária Csidey3
1Instituto de Neurociencias, Universidad Miguel Hernández-CSIC, San Juan de Alicante, Spain.
Insights
Corneal sensory nerve function is impaired in congenital aniridia, affecting mechanical and cold sensitivity, with deficits worsening with age and aniridia-associated keratopathy severity. PAX6 gene mutations play a critical role in maintaining corneal sensory integrity.
Area of Science:
- Ophthalmology
- Neuroscience
- Genetics
Background:
- Congenital aniridia is a rare genetic disorder affecting eye development.
- Corneal sensory innervation is crucial for ocular surface health and protection.
- The role of PAX6 gene mutations in corneal sensory function is not fully understood.
Purpose of the Study:
- To comprehensively assess corneal sensory nerve functionality in patients with congenital aniridia.
- To evaluate mechanical sensitivity, cold sensitivity, reflex tearing, and basal blinking and tearing.
- To investigate the influence of age, aniridia-associated keratopathy (AAK), and PAX6 mutation type on corneal sensory deficits.
Main Methods:
- A cohort of 14 patients with PAX6-related aniridia and 9 healthy controls were studied.
- Mechanical and cold corneal sensitivity were quantified using a verbal numerical scale (VNS).
- Spontaneous blinking, basal, and CO2-induced reflex tearing were measured; data were stratified by age, AAK, and PAX6 mutation type.
Main Results:
- Reduced mechanical sensitivity was observed in aniridia patients, particularly adults, those with severe AAK, and patients with loss-of-function (LOF) PAX6 mutations.
- Cold sensitivity was also reduced in adult patients and those with severe AAK.
- Tearing reserve was significantly reduced in aniridia patients, while basal blinking and tearing remained unchanged.
Conclusions:
- Congenital aniridia is associated with impaired corneal mechano-nociceptors, polymodal nociceptors, and cold thermoreceptors.
- Sensory deficits in aniridia correlate with increasing age and AAK severity.
- PAX6 gene variants, especially LOF, are critical for maintaining corneal sensory integrity.
Purpose:
To characterize, for the first time, corneal sensory nerve functionality in congenital aniridia by assessing mechanical and cold corneal sensitivity, reflex tearing, and basal blinking and tearing.
Methods:
A cohort of fourteen pediatric and adult patients with PAX6-related aniridia was enrolled in the study. Mechanical sensitivity (noncontact gas esthesiometer) and cold sensitivity (4°C drops) were quantified using a 0 to 10 verbal numerical scale (VNS). Spontaneous blinking, basal, and CO2-induced reflex tearing were also measured. Data were stratified by age, aniridia-associated keratopathy (AAK), and PAX6 mutation type-reduced expression or loss-of-function (LOF) genetic variants-and compared with healthy controls (n = 9).
Results:
Mechanical sensitivity to high-intensity stimuli was reduced in patients with aniridia, particularly in adults (2.2 ± 0.3 VNS, P = 0.02), those with severe AAK (2.4 ± 0.4 VNS, P = 0.09), and patients with LOF mutations (2.4 ± 0.2 VNS, P = 0.05) compared with controls (3.9 ± 0.5 VNS). Cold sensitivity was also reduced in adult patients (5.5 ± 0.5 vs. 3.8 ± 0.6 VNS, P = 0.05) and severe AAK (3.2 ± 0.8 VNS, P = 0.01). Reflex tearing values exhibited variability but trended lower in patients than controls, and tearing reserve (reflex minus basal tearing) was significantly reduced (12.7 ± 3.8 vs. 1.9 ± 1.9 mm, P = 0.02). Basal blinking and tearing were not significantly different.
Conclusions:
These findings suggest impaired mechano-nociceptors, polymodal nociceptors, and cold thermoreceptors function in congenital aniridia, with severity increasing with age and AAK grade. LOF mutation results show a trend with greater deficits than reduced expression variants, highlighting a critical role of PAX6 in corneal sensory integrity.
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