Ocular Hypotony in Children Under 18 Years
In pediatric patients under 18 years of age, intraocular pressure (IOP) below 5 mmHg is generally considered ocular hypotony, though this value should be interpreted in the context of the child's age and clinical presentation.
Definition and Age Considerations
The definition of ocular hypotony in pediatric patients requires careful consideration of several factors:
- Normal IOP in children tends to be lower than in adults
- IOP gradually increases with age throughout childhood
- Age-specific considerations affect the threshold for hypotony
Age-Related IOP Patterns
While the American Academy of Ophthalmology's Pediatric Eye Evaluations Preferred Practice Pattern 1 does not explicitly define hypotony in children, we can derive understanding from normal IOP patterns:
- In infants and very young children: IOP tends to be lower
- In older children and adolescents: IOP gradually approaches adult values
- By late adolescence: Normal IOP range becomes similar to adults (generally 10-21 mmHg)
Clinical Significance and Evaluation
When evaluating potential ocular hypotony in children, consider:
- Measurement technique: IOP measurement in children can be challenging and may require specialized equipment such as the Tono-Pen, Perkins tonometer, or iCare rebound tonometer 1
- Clinical context: Hypotony rarely exists in isolation and is typically associated with other ocular findings
- Associated conditions: Conditions like uveitis, retinal detachment, or post-surgical states may cause hypotony 2, 3
Risk Factors and Complications
Low IOP in children may be associated with:
- Ocular trauma
- Recent intraocular surgery
- Uveitis or inflammatory conditions 2
- Retinal detachment 3
- Cyclodialysis cleft
- Ciliary body dysfunction
Monitoring and Management
For children with suspected hypotony:
- Serial IOP measurements to track trends
- Comprehensive examination to identify underlying causes
- Treatment directed at the underlying condition
- Close follow-up to monitor for complications such as hypotony maculopathy
Important Considerations
- IOP fluctuates throughout the day, with potential nocturnal elevations 4
- Corneal thickness and biomechanical properties can affect IOP readings but remain relatively stable throughout the day 4
- Systemic factors like blood glucose, triglycerides, blood pressure, and pulse rate can influence IOP 5
Clinical Pitfalls to Avoid
- Relying on a single IOP measurement
- Failing to consider age-appropriate normal values
- Not investigating underlying causes of hypotony
- Overlooking associated ocular pathology
- Disregarding the influence of corneal thickness on tonometry readings
While specific pediatric guidelines for hypotony are limited, clinical practice generally considers IOP below 5 mmHg as hypotony in children, with careful consideration of age, clinical context, and associated findings.