CHAPTER 17 Pediatric cataract surgery
Clinical features, diagnosis, and differential diagnosis
Five components are needed to define a cataract: when they appear, the degree to which the opacity occupies the capsular bag, anatomically where in the lens the opacity lies, its etiology, and morphology. Cataracts may present at birth (congenital) or develop through the first few years of life (developmental); they may be total or partial; they may be nuclear (fetal or embryonal), sutural, lamellar, capsular (usually anterior) or subcapsular (usually posterior), or polar (posterior or anterior); they may be inherited or sporadic with the latter including the acquired variety such as infectious (in utero TORCH infections), metabolic (e.g. galactosemia, Lowe syndrome, galactokinase deficiency) or secondary to other ocular conditions (e.g. persistent fetal vasculature, PFV). Morphology of cataracts includes descriptions such as anterior pyramidal, membranous, pulverulent, blue dot, and other specific entities such as anterior or posterior lenticonus. Such specifications sometimes help with systemic diagnoses (e.g. anterior lenticonus should alert the surgeon to the possibility of Alport syndrome) while pyramidal cataracts are often associated with corneal astigmatism1.
Anatomical considerations
The average axial length of an infant is 16.5 mm at birth. There is a rapid growth of the eye in the first 18 months of life with an average growth of 3.75 mm. By 13 years of age the average axial length is 23 mm2. Parents often ask if an intraocular implant would have to be removed as the child’s eye grows; this is not so if the implant is placed in the bag. This is because once the lens fibres are removed the bag stops growing. It is therefore important to know that the capsular bag diameter also changes with age. (The capsular bag diameter for the purposes of understanding the dimension available for an implant to be placed is the diameter of the crystalline lens + 1 mm). On average, the capsular bag diameter is 7 mm at birth, 9 mm at 2 years, 9–10 mm at 5 years, 10–10.5 mm at 16 years, and 10.5 mm > 21 years of age2.
Fundamental principles and goals of surgery
There are three important fundamental principles for successful pediatric cataract surgery:
