We observed changes in tear film function, meibomian gland function and meibomian gland morphology after congenital cataract surgery. Our data suggested that cataract surgery in children may influence tear film function and meibomian gland function transitorily without causing morphological changes in the meibomian glands.
Dry eye is one of the most frequent complications following adult cataract surgery. It causes ocular discomfort, fluctuating vision, and influences vision-related quality of life postoperatively owing to tear film dysfunction and MGD.17,18 Whether cataract surgery will influence tear film function or meibomian gland function in children is still unknown.
This study found that lid margin score increased significantly at 1 week postoperatively and began to recover at 1 month postoperatively. Vascular engorgement and anterior or posterior displacement of the mucocutaneous junction were the most common lid margin abnormalities in this study. More than 50% of eyes in this study showed vascular engorgement and anterior or posterior displacement of the mucocutaneous junction at 1 week postoperatively. Previous studies have suggested that vascular engorgement may accompany the narrowing of the meibomian gland orifices, which is a feature of early MGD.19 Lid margin changes are also signs of inflammation, which is one of the most important mechanisms of dry eye and MGD. It is widely acknowledged that cataract surgery can induce inflammatory responses with the arrival of neutrophils and macrophages and the production of inflammatory mediators.20,21 The expression of the cyclooxygenase 2 (COX-2) enzyme, which catalyzes a key step in the synthesis of prostaglandin, increased at 24 hours and 4 days postoperatively and reached a peak at 5 days postoperatively in lens epithelial cells.20 Upregulated inflammatory responses may increase lid margin scores and ocular symptoms postoperatively.
This study also found that the tear film stability parameters, including the first NIBUT and average NIBUT, decreased significantly at 1 month postoperatively and recovered to baseline levels at 3 months postoperatively. And CFS increased significantly at 1 week and 1 month postoperatively and also recovered at 3 months postoperatively. It was widely agreed that an unstable tear film has a pivotal role in the mechanism of dry eye, leading to symptoms and visual impairments.18 Of the participants, 40% (6/15) had their first NIBUT lower than 5 seconds at 1 month postoperatively. In adults, TBUT decreased significantly at 1 month and 3 months after cataract surgery, which was in accordance with this study.17 Inflammation and topical medications may contribute to the unstable tear film and CFS postoperatively. Topical medications were used for all patients until 1 month postoperatively, which may have further affected tear film stability. On the other hand, topical antibiotics and steroid use may also help to treat the inflammation and improve clinical parameters.
In our study, detailed changes in the meibomian glands were assessed, including the tortuosity, width, area and length. Of the participants, 47.06% had meibomian gland atrophy, and 21.43% had meibomian gland tortuosity. Previous studies have observed that meibomian gland morphology changes, including atrophy, start early in life.22 Moreover, meibomian gland morphologic changes can be an early and sensitive indicator of MGD.23,24 A study by Shirakawa R et al. found that no significant meibomian gland shortening or dropout was observed in children under 3 years of age,25 while in children aged 4 to 17 years, 42% had some evidence of meibomian gland atrophy.22 Another study found that 45.5% of asymptomatic children between 7 and 14 years old had an MG deficiency between 20% and 30%.8 However, our study did not find significant meibomian gland morphological changes within 6 months after cataract surgery compared to baseline levels and normal controls. This result was in accordance with the study in adults after cataract surgery.17
The TMH did not change significantly after cataract, which indicated a minor change in tear volume. A previous study also found that lower tear meniscus height, depth and area did not change significantly within 3 months after cataract surgery in adults.17
The first limitation of this study was that the sample size was not large enough for further analysis. Second, a longer follow-up may be needed to observe long-term changes in the meibomian glands and tear films.