Controversies in pediatric cataract surgery

Abstract

The field of pediatric cataract surgery is constantly evolving. However, as demonstrated in a large number of studies, the long-term anatomical and functional success is often unpredictable, particularly in the first year of life. Attempts have been made to improve surgical outcomes by employing various techniques including modifications in the intraocular lens power calculation, methods and design, improvisations in the surgical steps, postoperative management and amblyopia therapy, to name just a few. However, few of these techniques have been validated in large, multicenter clinical trials. As a result, there is lack of consensus guidelines in literature for managing children with cataract. This editorial focuses on the current controversies in the field of pediatric cataract surgery and the need for further research.

Keywords:

• axial length
• glaucoma
• infant aphakia
• intraocular lens
• pediatric cataract
• phacoemulsification

There have been significant advances in the field of cataract and refractive surgery in the past decade, greatly improving the visual outcome of the patients. However, the diagnosis of pediatric cataract and its surgical management remain a major challenge worldwide. With an estimated prevalence of 3–6/10,000 live births, pediatric cataract continues to remain one of the major causes of preventable childhood blindness [1]. Often, children with pediatric cataract are identified very late, especially in developing countries, leading to permanent visual disability and legal blindness due to irreversible sensory-deprivation amblyopia. Thus, children who present at a very late age have suboptimal outcomes and they may not benefit much from cataract surgery.

Recent advances in the technique of pediatric cataract surgery have contributed toward decreasing the high rates of complications in these children. In addition, there have been significant contributions in the field of neurophysiology of the visual system and the etiopathogenesis of childhood cataract. Breakthroughs in intraocular lens (IOL) design and surgical techniques have resulted in decreased incidence of postoperative inflammation and posterior capsular opacification (PCO). While the anatomic success of pediatric cataract surgery has improved, functional and long-term outcomes are still unpredictable, particularly in infants. As of 2015, there still exist many unanswered questions in the field of pediatric cataract surgery.

Estimation of the axial growth is one of the major challenges for long-term refractive success in children. Axial growth of the eye may be affected by a number of factors such as physiological growth of the eyeball that may continue in the second decade of life, sensory stimulus, genetic factors and presence of pseudophakia [2]. Due to inherent limitations and errors in the measurement techniques of axial length, the refractive outcomes may vary. Thus, controversies exist in choosing the correct technique of axial length measurement. The contact technique may result in an undesirable postoperative induced myopia due to corneal indentation, for which correction factors cannot be applied [3]. Immersion A-scan is considered superior for the measurement of axial length. In addition, there is a lack of consensus in choosing the appropriate IOL power for implantation during surgery. The available formulae for calculation of IOL power provide highly accurate results for adults. However, younger children (<2 years) and those with smaller eyes (<20 mm) have higher prediction errors ranging up to 14 D, resulting in failure to achieve the desired postoperative refractive target [4]. Several studies have compared the efficacy of the available IOL power calculation formulae in achieving postoperative target refraction. The SRK II, SRK/T, Holladay, Olsen and Hoffer Q may result in unwanted under- or overcorrection. Data from a large prospective study, the Infant Aphakia Treatment Study (IATS), showed that absolute prediction errors were least with the T2 formula (median of 1.1 D using manufacturer’s A constant), since it may correct for the steepness of the cornea [5]. However, further refinement in the IOL calculation formulae is necessary. The IATS showed that prediction errors of >2 D were found in >40% eyes [6]. Certain authors recommend low degree of under-correction (induced postoperative hyperopia) to account for the postoperative myopic shift. However, others believe that initial postoperative emmetropia may be more suitable as it may aid the early amblyopia management [7]. Postoperative refractive surprises may warrant additional procedures such as IOL exchange or keratorefractive procedures such as laser in-situ keratomileusis, once the growth of the eye is complete. Authors have attempted various methods to rehabilitate these patients, but none of these techniques have been shown to be superior over the other. Hence, prevention of postoperative large refractive errors, though challenging, is the preferred strategy.

The technique of cataract surgery in children requires special consideration. While manual continuous curvilinear capsulorhexis is the preferred method of anterior capsulotomy, vitrectorhexis is a preferred technique in infants [8]. Recently, Dick and Schultz have described the use of femtosecond laser for anterior capsulotomy and lens division [9]. Management of the posterior capsule is further complicated as this has a direct bearing on the incidence of postoperative PCO. Most surgeons prefer primary posterior capsulotomy under 7 years of age [8,10]. However, controversy exists in the removal of anterior vitreous face using limbal anterior vitrectomy (AV). Removal of the anterior vitreous scaffold may prevent the proliferation of lens epithelial cells leading to PCO [10]. Some authors advocate that AV may not be required beyond the age of 5 years [8]. The decision to perform primary posterior capsulotomy and AV may be based upon the intraoperative situation, age of the child and the choice of IOL. Recent introduction of minimally invasive transconjunctival vitrectomy systems (23- and 25-gauge) may lead to improved outcomes in children with cataract [11]. Further studies are required to provide long-term results of primary posterior capsulotomy and AV, and thereby establish consensus guidelines in the management of anterior and posterior capsules.

Surgical management of complicated cases such as ectopia lentis associated with Marfan’s syndrome and trauma, among various others, have not been adequately described in literature. Many controversies exist in the surgical techniques for treating children diagnosed with associated persistent fetal vasculature, Marfan’s syndrome and other ocular anomalies. The outcomes of cataract surgery in children with persistent fetal vasculature continue to remain suboptimal due to high incidence of complications such as retinal detachment and glaucoma. With advancing research, the experiences and skills of surgeons are evolving worldwide.

The youngest age of performing cataract surgery is a contentious issue in pediatric cataract. The IATS included patients as young as 28 days old (median age: 1.8 months). However, few surgeons may prefer to wait until the child is at least 2 months of age. The decision to implant and the choice of IOL also remain controversial issues in pediatric cataract surgery. Among children >2 years of age, primary IOL implantation has become the preferred practice [12]. The IATS recommended cautious approach when performing IOL implantation under the age of 6 months. This study showed that children rehabilitated with contact lens postoperatively required fewer additional surgical procedures [13,14]. However, recent studies have shown that both hydrophobic acrylic and polymethyl methacrylate lenses may provide good anatomical and functional success in children <1 year of age [15]. In order to find the influence of IOL design on postoperative visual function, contrast sensitivity and ocular alignment, prospective studies have been performed using multifocal [16] or light-adjustable IOLs [17] in children. This is based on the premise that some children may demonstrate improvement in visual function following cataract surgery, despite lack of objective improvement in Snellen’s visual acuity. However, there is no consensus on the use of these IOLs as long-term safety and functional success is yet to be determined in larger cohorts.

Microcornea and microphthalmos are considered to be an absolute contraindication for IOL implantation and the surgeons may prefer to leave the patients aphakic. This may result in a very high postoperative hyperopia (>20 D, excluding near add) for which spectacle correction may be challenging. However, recently published medium and short-term data suggest that it may be possible to attain favorable outcomes in these children with primary IOL implantation [18]. Another area where controversy exists is the requirement for downsizing of the IOL, especially in smaller eyes and in children <2 years of age. The overall diameter of conventional IOLs may range from 12.5 to 13 mm, resulting in capsular bag ovaling and stretch. This effect may be much higher among IOLs with rigid design [19].

The preferred location of IOL implantation is in the capsular bag. In order to improve and maintain IOL centration, as well as decrease the incidence of PCO, optic capture of the IOL has been recommended in literature [20]. However, optic capture may result in increased postoperative inflammation. Therefore, this maneuver may have its own limitations, especially in pediatric population. On the other hand, alternate techniques such as bag-in-the-lens IOL implantation have been shown to maintain the clarity of the visual axis [21]. Adequate IOL centration and maintenance of clarity of the visual axis remain the major challenges in pediatric cataract surgery.

There is a high incidence of postoperative complications following pediatric cataract surgery. PCO and secondary glaucoma remain the major causes for surgical re-intervention in children with pseudophakia. Among infantile eyes, occurrence of PCO is almost universal. The incidence of PCO is very high among older children as well due to heightened inflammatory response noted in the younger population. Thus far, there are no consensus guidelines or therapeutic protocols to prevent or treat PCO in children. The incidence of glaucoma is very high among children with both pseudophakia and aphakia. Glaucoma may result in significant visual morbidity among children. Among children <6 months of age undergoing cataract surgery with primary IOL implantation, one-fourth may develop glaucoma within 1 year of surgery [22]. The elevated intraocular pressure may not respond to conventional treatment and may require surgical interventions such as drainage tube placement. The postoperative course may also be complicated by significant intraocular inflammation that may lead to formation of synechiae, capsular phimosis, IOL decentration and secondary glaucoma. Children with Marfan’s syndrome are prone to developing postoperative retinal detachment. Thus, children undergoing cataract surgery require comprehensive and long-term follow-up in order to maintain visual function.

The present-day postoperative management protocols, including the amblyopia therapy and examination under anesthesia, are variable among ophthalmologists and further research is needed in order to establish a standardized approach. Postoperative treatment with topical steroids is important to ensure minimal inflammatory sequelae. There is no consensus on the frequency of topical steroids. The IATS protocol specified four-times a day use of topical steroids [23]. However, many authors may prefer more frequent, that is, six- to eight-times/day use of topical steroids, at least in the early postoperative period [8,10]. Few surgeons may also prescribe oral steroids in the postoperative period. It is imperative to maintain a long-term follow-up and initiate amblyopia therapy in the early postoperative period. Technique of visual function assessment and duration of follow-up is also a matter of controversy. Further studies in this regard would ensure optimal visual rehabilitation in children with cataract.

Conclusion

While tremendous advancements have taken place in the field of pediatric cataract surgery in the last few decades, further research is warranted in order to ensure gratifying surgical results. There is a need for larger, collaborative multicenter studies that may provide evidence to replace individual preferred practices. Studies that focus on the current controversies in pediatric cataract surgery are likely to further improve functional vision in a large number of children diagnosed with cataract.

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript