Keratoconus progression after intrastromal corneal ring segment implantation according to age: 5-year follow-up cohort study

Intrastromal Corneal Ring Segments and Keratoconus Progression: A Case Series Study

OBJECTIVE

To assess keratoconus (KC) progression following the implant of intrastromal corneal ring segments (ICRSs) in young patients.

MATERIALS AND METHODS

Retrospective, longitudinal, observational, controlled nonrandomized case series study. Keratoconus patients aged 25 years or younger who underwent uneventful ICRS surgery and completed at least 3 years of follow-up were enrolled. Controls were of similar age and treatment-naive patients with KC. The following Pentacam imaging (Oculus, Wetzlar, Germany) data were analyzed: keratometric (maximum, in-flattest meridian, in-steepest meridian, and mean), aberrometric (higher-order aberrations and coma), pachymetric (thinnest corneal thickness), and elevation (maximum posterior elevation). The main outcome measure was KC progression.

RESULTS

The study sample comprised 20 eyes of 18 cases (age 20.20 ± 3.70 years, nine right eyes, 14 male patients) and 30 eyes of 24 controls (age 20.80 ± 3.20 years, 15 right eyes, 21 male patients). The mean follow-up duration was 4.90 ± 1.70 years (range 3-8 years) for cases and 4.50 ± 1.40 years (range 3-8 years) for controls. Four cases and two controls met criteria for KC progression.

CONCLUSIONS

Intrastromal corneal ring segments did not have significant impact on KC progression in the cohort.

Keratoconus

Keratoconus is a progressive eye disorder primarily affecting individuals in adolescence and early adulthood. The ectatic changes in the cornea cause thinning and cone-like steepening leading to irregular astigmatism and reduced vision. Keratoconus is a complex disorder with a multifaceted aetiology and pathogenesis, including genetic, environmental, biomechanical and cellular factors. Environmental factors, such as eye rubbing, UV light exposure and contact lens wearing, are associated with disease progression. On the cellular level, a complex interplay of hormonal changes, alterations in enzymatic activity that modify extracellular membrane stiffness, and changes in biochemical and biomechanical signalling pathways disrupt collagen cross-linking within the stroma, contributing to structural integrity loss and distortion of normal corneal anatomy. Clinically, keratoconus is diagnosed through clinical examination and corneal imaging. Advanced imaging platforms have improved the detection of keratoconus, facilitating early diagnosis and monitoring of disease progression. Treatment strategies for keratoconus are tailored to disease severity and progression. In early stages, vision correction with glasses or soft contact lenses may suffice. As the condition advances, rigid gas-permeable contact lenses or scleral lenses are prescribed. Corneal cross-linking has emerged as a pivotal treatment aimed at halting the progression of corneal ectasia. In patients with keratoconus with scarring or contact lens intolerance, surgical interventions are performed.

[Aberrometry in the diagnosis and treatment of keratoconus]

Keratoconus (KC) is a bilateral progressive disease that often begins in young adulthood. Advanced KC significantly impairs patients' quality of life, making early detection of the condition a critical goal for specialists. Early identification of KC greatly influences both the treatment strategy and the outcomes. This review focuses on the ocular wavefront in KC, which is of interest from the perspective of early diagnosis. The article outlines the nature of optical aberrations in the eye, particularly in KC, and the principles of wavefront aberration analysis. An increase in higher-order aberrations is one of the earliest signs of incipient KC and a key contributor to reduced visual quality. Some of the widely used KC treatment methods, such as corneal cross-linking and the implantation of intracorneal segments, has been established to positively impact many aspects of KC pathogenesis, including reduction in higher-order aberrations, which in turn improves visual quality. Monitoring of the outcomes of treatment or optical correction in KC using higher-order aberrations is a delicate approach, as vision improvements following treatment are often unexplained by routine eye examination methods. However, the choice of the optimal method of visual rehabilitation for KC patients remains unresolved. Efforts to find new treatment methods, primarily through combinations and modifications of existing techniques, are ongoing. The article discusses this promising approach of using wavefront as an additional criterion for assessing the performance of the optical system in the diagnosis, treatment, and optical correction of KC.

Management of keratoconus: an updated review

Keratoconus is the most common corneal ectatic disorder. It is characterized by progressive corneal thinning with resultant irregular astigmatism and myopia. Its prevalence has been estimated at 1:375 to 1:2,000 people globally, with a considerably higher rate in the younger populations. Over the past two decades, there was a paradigm shift in the management of keratoconus. The treatment has expanded significantly from conservative management (e.g., spectacles and contact lenses wear) and penetrating keratoplasty to many other therapeutic and refractive modalities, including corneal cross-linking (with various protocols/techniques), combined CXL-keratorefractive surgeries, intracorneal ring segments, anterior lamellar keratoplasty, and more recently, Bowman's layer transplantation, stromal keratophakia, and stromal regeneration. Several recent large genome-wide association studies (GWAS) have identified important genetic mutations relevant to keratoconus, facilitating the development of potential gene therapy targeting keratoconus and halting the disease progression. In addition, attempts have been made to leverage the power of artificial intelligence-assisted algorithms in enabling earlier detection and progression prediction in keratoconus. In this review, we provide a comprehensive overview of the current and emerging treatment of keratoconus and propose a treatment algorithm for systematically guiding the management of this common clinical entity.

Keratoconus: An updated review

Keratoconus is a bilateral and asymmetric disease which results in progressive thinning and steeping of the cornea leading to irregular astigmatism and decreased visual acuity. Traditionally, the condition has been described as a noninflammatory disease; however, more recently it has been associated with ocular inflammation. Keratoconus normally develops in the second and third decades of life and progresses until the fourth decade. The condition affects all ethnicities and both sexes. The prevalence and incidence rates of keratoconus have been estimated to be between 0.2 and 4,790 per 100,000 persons and 1.5 and 25 cases per 100,000 persons/year, respectively, with highest rates typically occurring in 20- to 30-year-olds and Middle Eastern and Asian ethnicities. Progressive stromal thinning, rupture of the anterior limiting membrane, and subsequent ectasia of the central/paracentral cornea are the most commonly observed histopathological findings. A family history of keratoconus, eye rubbing, eczema, asthma, and allergy are risk factors for developing keratoconus. Detecting keratoconus in its earliest stages remains a challenge. Corneal topography is the primary diagnostic tool for keratoconus detection. In incipient cases, however, the use of a single parameter to diagnose keratoconus is insufficient, and in addition to corneal topography, corneal pachymetry and higher order aberration data are now commonly used. Keratoconus severity and progression may be classified based on morphological features and disease evolution, ocular signs, and index-based systems. Keratoconus treatment varies depending on disease severity and progression. Mild cases are typically treated with spectacles, moderate cases with contact lenses, while severe cases that cannot be managed with scleral contact lenses may require corneal surgery. Mild to moderate cases of progressive keratoconus may also be treated surgically, most commonly with corneal cross-linking. This article provides an updated review on the definition, epidemiology, histopathology, aetiology and pathogenesis, clinical features, detection, classification, and management and treatment strategies for keratoconus.

Evaluation of keratoconus progression and visual improvement after intrastromal corneal ring segments implantation: A retrospective study

OBJECTIVE

To investigate the role of ICRS in halting keratoconus progression in a large sample of patients.

METHODS

A retrospective, non-comparative, interventional study based on the review of medical records of patients diagnosed with keratoconus who underwent Ferrara corneal ring segment implantation. A retrospective chart analysis study of 123 operated eyes with follow-up ranging from 3 to 16 years (mean 5.3 ± 3.6 years) was performed. This study was carried out at Ocular Surgery Unit, São Paulo, Brazil. All topographic data were obtained from Pentacam (Oculus, Arlington, USA). The same surgeon performed all surgeries, and the Ferrara ICRS nomogram was used for ICRS selection in all cases.

RESULTS

Corrected distance visual acuity, keratometry, and topographic astigmatism improved in most cases, with statistical significance. In 42 eyes (53.8%), there was an increase in K1 or K2, and in 36 (46.2%), there was a reduction or maintenance in K1. Considering a difference higher than 1 D, between 3-month post-surgery and final visit (group 3), 32 eyes (41%) showed an increase, and 46 eyes (59%) ended equal or below this value.

CONCLUSION

The implantation of ICRS showed improvement in visual and keratometric indexes. The majority of patients did not increase more than one diopter in keratometric values after ICRS implantation. ICRS may be effective for slowing disease progression, especially in older patients.