By Sarah Guy
When congenital cataract surgery is performed at an early age, central corneal thickness (CCT) increases, show study results published in the British Journal of Ophthalmology.
The increase in CCT could be clinically significant and could "artificially" increase intraocular pressure (IOP) readings taken in this patient population, say the researchers.
"Functional and anatomical evaluations may be difficult to perform in children with congenital cataract or aphakia due to nystagmus, amblyopia and cooperation," say Graziela Massa Resende and colleagues from the University of Campinas in Brazil.
"Hence, IOP measurement is an important diagnostic variable for glaucoma," they add.
The team took CCT and IOP measurements before phacoaspiration, and 6, 12, 18, 24, and 36 months afterwards in 37 eyes of 26 children with congenital cataracts aged a mean of 44 months. The condition is an important cause of visual impairment in children, and its management can often lead to postoperative complications, remark Resende et al.
After a mean 30-month follow-up, 15 (40.5%) eyes became aphakic, of which 13.3% belonged to patients older than 2 years at the time of surgery, and 22 (59.5%) eyes became pseudophakic, of which 18.2% belonged to patients younger than 2 years at the time of surgery. This difference was significant.
Only one child developed glaucoma in one eye, reflecting either the study's short follow-up period or recent improvements in surgical technique, suggest the authors.
Age at the time of surgery was inversely related to CCT change, whereas there was no correlation between age and IOP, nor between CCT and IOP change. Indeed, when surgery was performed between the ages of 0 and 12 months, the researchers found a mean CCT change at 3 months postsurgery of 70 µm, compared with 6 µm, -17 µm, and 48 µm when surgery was performed in children at ages 1-5 years, 5-10 years, and more than 10 years.
Overall, the mean CCT change in aphakic eyes was significantly higher than that observed in pseudophakic eyes, at 56 µm versus 12 µm. Mean IOP increased significantly during the study follow-up period, from 12.05 mm/Hg to 13.89 mm/Hg, but no differences were observed between aphakic and pseudophakic eyes.
"In normal children, the cornea thins during the early months of life and stabilises over the following years," write Resende and co-workers.
The finding that earlier surgery for congenital cataracts increases CCT measurements could indicate more significant corneal changes in the young patient, and/or that absence of a lens could be harmful for development.
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