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Morphometric analysis of pars plana development in humans
R J Hairston1, A M Maguire, S Vitale
1Eye Pathology Laboratory, Wilmer Ophthalmological Institute, Johns Hopkins Hospital Medical Institutions, Baltimore, Maryland, USA.
Insights
Pars plana growth is rapid between 26-35 weeks gestation, correlating with infant eye axial length. Surgical readiness via pars plana approach is estimated at 62 weeks postconception.
Area of Science:
- Ophthalmology
- Pediatric Ophthalmology
- Ophthalmic Anatomy
Background:
- Quantitative data on human pars plana development is limited.
- Understanding pars plana dimensions is crucial for infant eye surgery.
- This study characterizes pars plana growth in relation to age and eye size.
Purpose of the Study:
- To provide a morphometric description of pars plana growth.
- To analyze pars plana development relative to postconceptional age.
- To examine the relationship between pars plana width and axial length.
Main Methods:
- Histologic specimens from 204 human eyes (10 weeks to 5 years) were analyzed.
- Axial length and temporal pars plana width were measured using a reticule system.
- Statistical analysis examined correlations between pars plana width, axial length, and postconceptional age.
Main Results:
- Rapid pars plana growth occurred between 26-35 weeks gestation.
- A linear relationship between pars plana width and axial length was observed after axial length reached 12 mm (r=0.918, P=0.0001).
- At 38-42 weeks postconception, mean pars plana width was 1.87 mm and mean axial length was 17.7 mm. By 62 weeks postconception, pars plana width was consistently >= 3 mm and axial length >= 19 mm.
Conclusions:
- Pars plana develops in the second trimester, with accelerated growth from 26-35 weeks gestation.
- Pars plana dimensions correlate strongly with axial length and postconceptional age.
- Pars plana vitreous surgery is feasible by 62 weeks postconception (approximately 6 months), assuming a 3 mm pars plana width is required.
Background:
Quantitative features of pars plana development in humans are not well characterized. Knowledge of the dimensions of this region is important for our understanding of the anatomy of infant eyes for the purposes of surgery. The purpose of this study was to provide a morphometric description of pars plana growth in relation to 1) postconceptional age and 2) axial length.
Methods:
We reviewed histologic specimens from 204 human eyes of postconceptional ages ranging from 10 weeks to 5 years. Axial length and temporal pars plana width were measured directly with a reticule system. The relationships among pars plana width, axial length, and postconceptional age were examined.
Results:
The most rapid phase of pars plana growth occurred between 26 weeks and 35 weeks gestation. A linear relationship between pars plana width and axial length existed once the axial length reached 12 mm (correlation coefficient = 0.918; P = 0.0001). In infants of 38-42 weeks postconceptional age, mean pars plana width was 1.87 mm (range, 0.9-2.8 mm; standard direction = 0.48 mm), and mean axial length was 17.7 mm (range, 15-23 mm; standard direction = 1.9 mm). After the age of 62 weeks postconception, all eyes had a temporal pars plana width > or = 3 mm and an axial length > or = 19 mm. The estimated age at which there was a 95% chance of the pars plana width being > or = 3 mm was 64.4 weeks (95% fiducial confidence limits, 60.8-86.2 weeks).
Conclusions:
The pars plana first develops during the second trimester of gestation. A rapid growth phase occurs between 26 weeks and 35 weeks postconception. The dimensions of the pars plana are correlated closely with axial length and postconceptional age. Assuming that a pars plana width of 3 mm is required for surgery to be performed via a pars plana approach, we estimate that pars plana vitreous surgery can be performed when the patient is at least 62 weeks old (postconception), which is a 6-month-old full-term infant.