Laboratory exam
Diagnosis
Basic metabolic panel, or blood glucose
Hypoglycemia, diabetes mellitus
Peroxisomal panel (VLCFA, phytanic acid)
Perixozomal disorders (chondrodysplasia, zellweger syndrome, refsum disease, neonatal adrenoleukodystrophy)
Plasma amino acids, acylacarnitine profile
Urine aminoacids
Lowe’s syndrome
Red blood cell Galactose-1-phosphate
Urine for reducing substances
Galactosemia
TORCH titres, varicella
Infectious causes
Karyotype
Trisomy
DNA microarray, exome sequencinga
Hereditary causes
4.5 Unilateral Congenital Cataract Morphology
The Infant Aphakia Treatment Study added much to what is known about the morphology of unilateral congenital cataract [24]. The specific morphology of unilateral cataract was reported after expert video review from the 83 treated infants. Results are summarized in Table 4.2. Total cataract and posterior lentiglobus were present in less than 10 % of infants. Fetal nuclear cataracts were the most common form of unilateral cataract, presenting in 54 % of eyes. There was extension of nuclear opacity into posterior cortex in over 90 % of nuclear cataracts. Additionally 100 % of nuclear opacities had a posterior capsular plaque present after lens removal was complete (Fig. 4.1). Cortical cataract was present in 25 % of cases; 76 % of these also had posterior capsular plaque present. Six percent of eye had isolated findings of persistent fetal vasculature, and an additional 16 % had evidence of persistent hyaloid artery in the presence of another cataract form (either nuclear or posterior cortical opacity type).
Table 4.2
Definition and occurrence of individual cataract diagnosis categories among 83 patients from the Infant Aphakia Treatment Study
Diagnostic categories | Definition | N (% of 83 patients) | |
|---|---|---|---|
1 | Entire lens is white | A uniform total white color lens with no red reflex visible even in the periphery of the lens | 3 (3.6 %) |
2 | Lens partially reabsorbed | An appearance of reduced central lens thickness leaving little if any cortex between the central anterior and posterior capsule | 7 (8.4 %) |
3 | Anterior capsular fibrosis | Presence of a dense, white fibrous-appearing opacity adherent to the anterior capsule | 5 (6.0 %) |
4 | Anterior and/or posterior cortical opacity not involving nucleus | Opacity located within any of the cortex peripheral to the “Y” sutures with clear nuclear sparing | 21 (25.3 %) |
5 | Opacity between Y-sutures (fetal nucleus) | Opaque lens material located between the anterior and posterior “Y” sutures | 45 (54.2 %) |
6 | Nuclear opacity extending into surrounding cortex | An opacity appeared to be mostly nuclear but with “riders” spreading into the adjacent cortex or if a predominantly nuclear opacity demonstrated evidence of posterior cortical opacification behind the nucleus that extended towards the posterior capsule without intervening clear cortex | 41 (49.4 %) |
7 | Posterior bowing of posterior lens capsule | Clear video evidence of bowing, such as posterior capsular defects associated with a lentiglobus lens. | 4 (4.8 %) |
8 | Opacity of posterior lens capsule | Presence of opacity of the posterior capsule after the entire cortex had been surgically aspirated | 73 (88.0 %) |
9 | Retrolental membrane with or without visible vessels | An opacity or vascular network on the posterior aspect of the lens that was associated with a fetal remnant and appeared to be distinct from a standard posterior capsular plaque | 12 (14.5 %) |
10 | Patent persistent hyaloid vessel | Appearance of blood within the persistent hyaloid vessel | 9 (10.8 %) |
11 | Non patent persistent hyaloid vessel | Absence of visible blood within the persistent hyaloid vessel | 2 (2.4 %) |
12 | Ciliary processes stretched | Visible stretched ciliary process | 2 (2.4 %) |
Fig. 4.1
Fetal nuclear cataract prior to surgery (a) and posterior capsule plaque visible after lens removal (b). Posterior capsular plaque may represent a fetal remnant and common origin of unilateral congenital cataract
4.5.1 Minimal Fetal Remnants
The concept of minimal fetal remnants was first introduced by Müllner-Eidenböck [25]. It was hypothesized that all unilateral cataracts resulted from a form of persistent fetal vasculature. In this study, 31 children with unilateral cataract were evaluated for persistent fetal remnants defined as perfused or non-perfused hyaloid remnants, but also including more subtle changes of the posterior lens such as posterior capsular plaque, retrolental membrane, and posterior bowing of lens capsule. All children with unilateral congenital cataract were reported to have changes consistent with classic PFV or minimal fetal remnants. This, in conjunction with IATS data, has led to the concept that PFV may present with a spectrum of severity. Severe cases may include a patent hyaloid remnant, ciliary body stretching, microphthalmia and retinal detachment. In milder forms, a unilateral congenital cataract with a posterior capsular plaque may be the only evidence of delayed hyaloid dissolution. The theory that many unilateral cataracts may result from a mild form of PFV has not been proven with basic clinical science. However, posterior capsular plaque has been studied in children with bilateral cataracts. As expected, the rate of posterior capsular plaque was much lower at 21 % in bilateral cataract cases [26].
4.6 Bilateral Congenital Cataract Morphology
Total cataract (Fig. 4.2) is the state of having a white lens, and no features of lens architecture beyond capsule able to be differentiated. Several genetic causes of total cataract have been identified. If left untreated, many forms of congenital cataract can progress to total lens opacity. As vision is completely obscured by this type of lens opacity, aggressive surgical intervention is warranted to clear the visual axis.
Fig. 4.2
Total cataract in two patients
4.6.1 Anterior Cataracts
Anterior polar cataracts (Fig. 4.3) are lens opacities found on the anterior capsule of the lens. They are generally less than 1 mm in size. They are often hereditary if bilateral, but can occur sporadically in unilateral cases. Pyramidal cataracts are a more severe form of anterior polar cataract where the lens opacity extends forward into the anterior chamber towards the cornea. Pathological study of these specimens reveals these lesions to be composed of fibrous metaplasia of lens epithelium (Figs. 4.4 and 4.5) [27]. It is likely that this type of opacity develops as a result of incomplete lens vesicle dislocation during emryogenesis. Due to their location, anterior polar cataracts are visible to the naked eye, and are often first noted by the parents. Anterior polar cataracts are not commonly visually significant, but can be associated with refractive error and amblyopia. If surgery is necessary, capsulorrhexis is quite challenging, as the capsule is pulled taught into the lesion. Thus, there is an even greater tendency for the capsule to tear peripherally than in other forms of infantile cataract [1].
Fig. 4.3
Anterior polar cataract
Fig. 4.4
Pyramidal cataract
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