Penetrating Keratoplasty in Infants With Peters Anomaly: Visual and Graft Outcomes

Congenital anterior segment ocular disorders: Genotype-phenotype correlations and emerging novel mechanisms

Development of the anterior segment of the eye requires reciprocal sequential interactions between the arising tissues, facilitated by numerous genetic factors. Disruption of any of these processes results in congenital anomalies in the affected tissue(s) leading to anterior segment disorders (ASD) including aniridia, Axenfeld-Rieger anomaly, congenital corneal opacities (Peters anomaly, cornea plana, congenital primary aphakia), and primary congenital glaucoma. Current understanding of the genetic factors involved in ASD remains incomplete, with approximately 50% overall receiving a genetic diagnosis. While some genes are strongly associated with a specific clinical diagnosis, the majority of known factors are linked with highly variable phenotypic presentations, with pathogenic variants in FOXC1, CYP1B1, and PITX2 associated with the broadest spectrum of ASD conditions. This review discusses typical clinical presentations including associated systemic features of various forms of ASD; the latest functional data and genotype-phenotype correlations related to 25 ASD factors including newly identified genes; promising novel candidates; and current and emerging treatments for these complex conditions. Recent developments of interest in the genetics of ASD include identification of phenotypic expansions for several factors, discovery of multiple modes of inheritance for some genes, and novel mechanisms including a growing number of non-coding variants and alleles affecting specific domains/residues and requiring further studies.

Peters anomaly: An overview

Peters anomaly (PA) is a rare, often bilateral, congenital corneal opacity, usually with a sporadic inheritance pattern, characterized by corneal opacities and irido-corneal or lenticular-corneal adhesions with a defect in the Descemet's membrane, occurring due to anterior segment dysgenesis during fetal development. Due to other ocular and systemic comorbidities, a team comprising pediatric cornea, glaucoma, and strabismus specialists in addition to a pediatrician and geneticist is necessary for the appropriate management of these children. Since the outcome of pediatric penetrating keratoplasty is variable and has a higher chance of failure when accompanied by additional procedures, such as lensectomy and vitrectomy, minimally invasive alternatives are increasingly being offered to these patients. Of note is the recently reported novel procedure: selective endothelialectomy for PA, which avoids the need for a corneal transplant and results in gradual clearing of the corneal opacity over time. In this overview, we aimed to describe the etiology, classification, pathophysiology, histopathology, clinical features, and management of PA.

Peters Anomaly: Novel Non-Invasive Alternatives to Penetrating Keratoplasty

BACKGROUND

Peters' anomaly (PA) is the most commonly encountered congenital corneal opacity (CCO) and displays a wide phenotypical range. The relatively recent adoption of high-quality anterior segment imaging in the form of high-frequency ultrasound biomicroscopy and anterior segment optical coherence tomography has aided in the accurate diagnosis of CCOs, facilitated distinction of PA from "pseudo-Peters' anomaly," and aided in prognostication and surgical risk stratification in PA. While the definitive management of PA, especially the more severe forms, is penetrating keratoplasty (PK), long-term success rates have overall been disappointing. This spurred the development of more non-invasive procedures, such as optical iridectomy and the more recently described selective endothelial removal, which represent viable alternatives to PK, at least in the less severe phenotypes of PA.

METHODS

Literature searches for the components of this review were performed using PubMed, in September 2021. The following keywords and their iterations were employed for the searches: "Peters' anomaly," "anterior segment dysgenesis," "kerato-irido-lenticular dysgenesis," "congenital corneal opacities." These were entered into the PubMed search engine, revealing 2852 related articles. The inclusion criteria included publications in the English language, specific to Peters' anomaly. Fifty-five studies that were published as systematic reviews or as nonrandomized comparative studies (cohort or case series) on the topic of Peters' anomaly were finally selected for this review.

RESULTS

This review provides a summary of Peters' anomaly in the context of advances in diagnosis, classification, and genotype-phenotype correlation of congenital corneal opacities, with a focus on penetrating keratoplasty, its outcomes, and non-invasive surgical options. While conservative therapies such as spontaneous clearing, mydriatic eye drops, and optical iridectomy may have variable success in milder variants of PA, penetrating keratoplasty in these eyes is fraught with several challenges and typically results in poor long-term functional outcomes. The management strategy depends on several variables such as phenotypical severity of PA, laterality, age at presentation, and capacity to adhere to the follow-up schedule. Notwithstanding the choice of treatment, it is essential that early and aggressive amblyopia therapy, a thorough systemic examination, and appropriate referral are undertaken for all patients of PA.

CONCLUSION

Peters' anomaly has seen recent advances in diagnosis, but treatment options remain limited. Focus directed towards less-invasive alternatives to keratoplasty may yield better functional outcomes.

Selective endothelial removal: A case series of a phase I/II surgical trial with long-term follow up

Peters anomaly is a congenital condition which results in a central corneal opacity from birth. Selective Endothelial Removal (SER) is a novel surgical technique and a form of regenerative therapy, which encourages clearance of the central corneal opacity by the patient’s own corneal endothelial cells, and it may potentially be beneficial for the treatment of Peters anomaly. We have performed a phase I/II surgical trial, evaluating the safety of SER in four eyes (three patients) with Peters Anomaly. These patients underwent SER at between 9 and 39 months of age, each demonstrating clearance of central corneal opacities and improvements in vision post-operatively. No complications occurred in any of these eyes, at a minimal post-operative follow-up duration of 48 months. We conclude that SER for Peters anomaly is a safe surgical procedure. While encouraging efficacy outcomes have been observed, these findings should be further evaluated in a larger scale Phase II/III surgical trial.

Peter's anomaly-A homeotic gene disorder

Peter's anomaly is a rare form of congenital anterior segment dysgenesis of the eye. Varying degrees of central corneal opacity and lenticulo-corneal or irido-corneal synechiae are the key hallmarks. The association of Peter's anomaly along with short stature, rhizomelia, broad short hands or brachydactyly, with facial dysmorphism, cleft lip, cleft palate, genitourinary and cardiovascular anomalies is a distinct and is often termed Peter's plus syndrome. Early detection is imperative to prevent sensory deprivation amblyopia. Glaucoma can be present at initial diagnosis or at any stage later, but treatment can be difficult. For the dense leukoma, corneal graft may be needed but visual prognosis is poor. Research focussing on gene editing and regenerative medicine using native corneal endothelial cells is ongoing.

[Optical rehabilitation and pediatric ophthalmological care following keratoplasty for childhood corneal opacities]

BACKGROUND

The younger the children are at the time of corneal transplantation, the worse the survival prognosis of the graft.

PREOPERATIVE CONSIDERATIONS

Preoperative considerations are significant in terms of accurate parental education, ensuring adherence to treatment and choosing the appropriate surgical time frame (amblyopia versus graft failure, compliance of the patient). Parental education must include the reduced visual prognosis in young children, exceptions being later acquired corneal pathologies such as inflammatory corneal scars (herpes) and keratoconus.

POSTOPERATIVE CARE

A distinction must be made between morphological care after transplantation and refractive correction as well as treatment of amblyopia. The younger the children, the less favorable the prognosis for the transplant and the more often multiple examinations with anesthesia are necessary in order to detect complications, such as infiltrates or suture loosening at an early stage. Especially unilateral congenital pathologies often do not lead to a sufficient improvement of amblyopia (refractory amblyopia, poor compliance).

CONCLUSION

The prognosis after keratoplasty in childhood is already partly decided by the careful evaluation of indications (no surgery of a sclerocornea) and the detailed and realistic clarification for the parents (cooperation with long-term ocular and systemic treatment even if the child has poor compliance, frequent check-ups, reduced chances of amblyopia treatment). The younger the child is at the time of transplantation, the more frequent are graft failure and the development of complications. Later manifesting diseases in older children (herpetic corneal scars, keratoconus) have a better prognosis.