Cataract Formation in Children After a Primary Vitrectomy

Cataracts after pars plana vitrectomy are common in adults, but they pose a particular challenge in pediatric patients because of their ongoing visual development. The rate of cataract formation in adults after vitrectomy ranges between 45% and 80% within 6 months to 2 years of a primary vitrectomy.^1,2 Researchers have described mechanisms for cataract formation, including light toxicity, oxidation of lens proteins, increased oxygen tension, use of intraocular gas, and the length of operative time.¹ However, the rates and timing of cataract extraction after pediatric vitrectomy (< 18 years of age) are less established. Only a few studies report a low prevalence with specific retinal diseases, such as retinopathy of prematurity.³ The scant literature is, in part, due to the rarity of pediatric retinal diseases and the paucity of pediatric retina surgeons.

Understanding the risk of cataract formation is important for counseling families and providing a multidisciplinary approach across comprehensive, pediatric ophthalmology, glaucoma, and pediatric retina specialties. To that end, our team took advantage of the unique opportunity the AAO IRIS Registry provides to study these rare rates on a larger scale. Through a grant sponsored by the Research to Prevent Blindness and the AAO IRIS Registry, we evaluated the rate and timing of cataract extraction after a primary pediatric vitrectomy in a cohort of patients included in the IRIS Registry between 2013 and 2019—a much larger cohort than we could have found otherwise. In this article, we describe the nuts, bolts, and ultimate results of the study.

THE NUTS AND BOLTS

The study had three main objectives:

• Primary objective: determine the rate of cataract extraction after any vitrectomy in patients younger than 18 years of age between 2013 and 2019.
• Secondary objective: determine the timing of cataract extraction after pediatric vitrectomy.
• Tertiary objective: determine the common etiologies and demographics associated with cataract extraction.

Between January 2013 and December 2019, a total of 821,152 eyes underwent a vitrectomy, of which 5,037 (0.6%) were pediatric. We further excluded eyes that had undergone previous cataract surgery or lensectomy before or at the time of their primary vitrectomy, leading to a final cohort of 4,127 eyes (3,579 patients).

Limitations of this study include the small sample size and the lack of current procedural terminology (CPT) codes and international classification of diseases codes specific to pediatric retinal disease and surgery. Additionally, this study may be underreporting the rates of cataract extraction because lensectomy is often bundled into retinal detachment (RD) repair codes (67108, 67113). Furthermore, pediatric RDs are challenging, and the severity of some RDs after primary repair may not warrant further surgery due to a poor prognosis.

WHAT WE FOUND

The average age at the time of the first vitrectomy was 10.35 years of age, with vitrectomy occurring more frequently in males (64.95%). There was also a significant number occurring predominantly in the southern United States (44.88%). The most common CPT vitrectomy code was 67113 for a complex RD repair, which accounted for 35% of all primary vitrectomies. On average, the eyes underwent 1.69 (range 1 to 6) vitrectomies before cataract extraction.

The overall rate of cataract extraction was 5.82% after a primary vitrectomy over the entire 6-year period. The 1- and 2-year incidences of cataract extraction after a primary vitrectomy were 3.94% and 4.18%, respectively. The average time to cataract surgery after a primary vitrectomy was 426.5 days (median 374.5 days).

Cataract extraction after a pediatric vitrectomy was a rare event. However, in those that developed cataracts, nearly 85% occurred within 2 years of the primary vitrectomy.

In a subset analysis, the rate of cataract extraction increased by age at the time of initial vitrectomy. The older a child was at the time of their initial vitrectomy, the higher the risk of undergoing cataract surgery. Less than 1% of pediatric eyes under the age of 2 required cataract surgery within 6 years of their vitrectomy, while nearly 10% of children ages 15 to 17 underwent cataract surgery. The most common etiology for a vitrectomy was a rhegmatogenous RD (28.8%).

WHAT MAY BE HAPPENING

The exact reason for the low rates is unknown, but it may be a function of the degree of vitreous removal and the goals of the surgery. In pediatric vitrectomy, the anterior hyaloid face is often left intact, and a “full” vitrectomy is minimized. The goals of surgery are often to relieve just enough tractional forces to allow the retina to settle; thus, the younger the patient, the more likely a greater amount of vitreous is left behind. For example, in RDs associated with stage 4A/B retinopathy of prematurity, the goal of the surgery is to relieve specific tractional forces (ridge to ridge, ridge to eyewall, ridge to optic nerve, or ridge to lens) rather than remove the entire anterior or posterior hyaloid. Children with persistent fetal vasculature also require vitrectomy, but a minimal vitrectomy is emphasized with the goal of cutting the stalk. In contrast, in older children undergoing vitrectomy secondary to rhegmatogenous RD or proliferative vitreoretinopathy, removing the posterior hyaloid and vitreous is key.

Age may also have a protective effect in and of itself. It may be that younger children have a higher metabolic capacity to counteract the presumed damage from oxygen-induced radicals compared with older children.

The type of tamponade may also be a factor. Our study did not specifically evaluate different tamponade agents, but macular holes and primary and complex RD codes (67042, 67108, and 67113) often require a tamponade agent, such as gas or silicone oil. Our study demonstrated higher cataract extraction rates in these specific codes (3% to 10%) and lowest with primary vitrectomy-only codes (CPT 67036, approximately 1.84%).

WHERE WE ENDED UP

The rate of cataract extraction after a primary pediatric vitrectomy is low, regardless of etiology. However, if cataracts develop, nearly 85% of extractions occur within 2 years of a primary vitrectomy. The low rates of cataract extraction in the pediatric population are consistent with prior studies in children who underwent a lens-sparing vitrectomy for retinopathy of prematurity (5.9%) and in younger adults (< 50 years of age).^3-4 These rates aid in patient and parent counseling, as well as care coordination and planning across the retina, pediatric retina, and comprehensive specialties.