Corneal electrolysis for recurrence of corneal stromal dystrophy after keratoplasty

Management of Stromal Corneal Dystrophies; Review of the Literature with a Focus on Phototherapeutic Keratectomy and Keratoplasty

Corneal dystrophies are a group of non-inflammatory inherited disorders of the cornea. This review considers treatment options for epithelial-stromal and stromal corneal dystrophies: namely Reis–Bücklers, Thiel–Behnke, lattice, Avellino, granular, macular and Schnyder corneal dystrophies. Where there is visual reduction, treatment options may include either phototherapeutic keratectomy (PTK) or corneal transplantation. Due to the anterior location of the deposits in Reis-Bücklers and Thiel–Behnke dystrophies, PTK is considered the treatment of choice. For lattice, Avellino, granular and macular corneal dystrophies, PTK provides temporary visual improvement; however, with recurrences, repeat PTK or a corneal transplant would be needed. For Schnyder dystrophy, should treatment be required, PTK may be the preferred option due to the potential for recurrence of the disease in corneal transplantation. This review discusses the literature and evidence base for the treatment of corneal dystrophies in terms of visual outcomes and recurrence rate.

Corneal Electrolysis for Granular Corneal Dystrophy Type 2 (Avellino Corneal Dystrophy) Exacerbation After LASIK

PURPOSE

To report two cases in which exacerbation of granular corneal dystrophy type 2 (GCD2; Avellino corneal dystrophy) after laser in situ keratomileusis (LASIK) was successfully removed by corneal electrolysis.

METHODS

This study involved a 66-year-old man and a 43-year-old man with GCD2 who had undergone bilateral LASIK for myopia 10 or more years prior to presentation. In both patients, GCD2 corneal opacity gradually developed postoperatively at the LASIK flap interface, thus resulting in a decrease of visual acuity. For treatment, the LASIK flaps in both patients were surgically lifted to directly remove the opacity. Corneal electrolysis was then applied to the back of each LASIK flap and stromal bed.

RESULTS

Postoperatively, the ocular symptoms and corneal opacities related to GCD exacerbation disappeared, with improvement of corrected and uncorrected distance visual acuity and almost no change of refractive error.

CONCLUSIONS

The findings reveal that corneal electrolysis is safe and effective for treating exacerbations of GCD2 following LASIK when applied to a surgically lifted flap, and that it successfully removes GCD2-related LASIK flap interface opacities with almost no change of refractive error postoperatively. [J Refract Surg. 2023;39(1):61-65.].

Potential-Driven Electrochemical Clearing of Ex Vivo Alkaline Corneal Injuries

Purpose

Corneal chemical injuries (CCI) obscure vision by opacifying the cornea; however, current treatments may not fully restore clarity. Here, we investigated potential-driven electrochemical treatment (P-ECT) to restore clarity after alkaline-based CCI in ex vivo rabbit corneas and examined collagen fiber orientation changes using second harmonic generation (SHG).

Methods

NaOH was applied to the corneas of intact New Zealand white rabbit globes. P-ECT was performed on the opacified cornea while optical coherence tomography (OCT) imaging (∼35 frames per second) was simultaneously performed. SHG imaging evaluated collagen fiber structure before NaOH application and after P-ECT. Irrigation with water served as a control.

Results

P-ECT restored local optical clarity after NaOH exposure. OCT imaging shows both progression of NaOH injury and the restoration of clarity in real time. Analysis of SHG z-stack images show that collagen fibril orientation is similar between control, NaOH-damaged, and post-P-ECT corneas. NaOH-injured corneas flushed with water (15 minutes) show no restoration of clarity.

Conclusions

P-ECT may be a means to correct alkaline CCI. Collagen fibril orientation does not change after NaOH exposure or P-ECT, suggesting that no irreversible matrix level fiber changes occur. Further studies are required to determine the mechanism for corneal clearing and to ascertain the optimal electrical dosimetry parameters and electrode designs.

Translational Relevance

Our findings suggest that P-ECT is a potentially effective, low-cost treatment for alkaline CCI.

Clinical Evaluation of Electrolysis for Reis-Bücklers Corneal Dystrophies and In Vivo Histological Analysis Using Anterior Segment Optical Coherence Tomography

PURPOSE

To report the effectiveness and clinical outcomes of corneal electrolysis for Reis-Bücklers corneal dystrophies (RBCDs) and provide in vivo histological analysis using anterior segment optical coherence tomography (AS-OCT).

METHODS

A total of 7 patients with RBCD (2 male patients, 5 female patients; mean age, 50.0 years) from 3 pedigrees were enrolled in this prospective study. All patients underwent corneal electrolysis for decreased visual acuity or blurred vision. Changes in visual acuity, refraction, and corneal thickness were evaluated 1 month after electrolysis and statistically analyzed. Changes observed in AS-OCT images before and after electrolysis were qualitatively and quantitatively assessed.

RESULTS

A total of 22 electrolysis procedures were performed on 7 patients during the median follow-up period of 10.7 years. Mean visual acuity significantly improved postoperatively, from 0.59 to 0.31 logarithm of the minimum angle of resolution (P = 0.013). Changes in refraction (from -2.42 to -2.12 D) and corneal thickness (from 570.8 to 577.6 μm) were not significant (P = 0.77 and P = 0.80, respectively). In all cases, assessment of AS-OCT images showed that the band lesion in Bowman's layer became less reflective after electrolysis. The mean thickness of the band lesion decreased from 101.5 to 88.3 μm (P = 0.002).

CONCLUSIONS

Corneal electrolysis is an excellent treatment option for corneal opacities caused by RBCD. Corneal electrolysis improves visual acuity without changing corneal thickness or refraction. Therefore, repeat corneal electrolysis over the years might be a preferred long-term treatment strategy for RBCD. Moreover, AS-OCT is suitable for evaluating the effectiveness of this treatment and might be useful during postoperative follow-up.

In vivo Imaging of Reis-Bücklers and Thiel-Behnke Corneal Dystrophies Using Anterior Segment Optical Coherence Tomography

Purpose

To investigate in vivo corneal changes of genetically confirmed Reis–Bücklers corneal dystrophy (RBCD) and Thiel–Behnke corneal dystrophy (TBCD) using anterior segment optical coherence tomography (AS-OCT).

Design

A single-center, prospective, comparative case series.

Methods

Seven patients from 3 pedigrees (3 males, 4 females) with RBCD [Arg124Leu (R124L) heterozygous missense mutation of human transforming growth factor beta-induced (TGFBI) gene] and 4 patients from 3 pedigrees (3 males, 1 female) with TBCD [Arg555Gln (R555Q) heterozygous missense mutation of TGFBI gene] were examined. Six patients with RBCD and three patients with TBCD exhibited recurrence after corneal surgery including penetrating keratoplasty, phototherapeutic keratectomy, and electrolysis. All patients were examined by slit-lamp biomicroscopy followed by AS-OCT. Selected AS-OCT images of the cornea were evaluated qualitatively for changes in shape and degree of light reflection of corneal deposits.

Results

Slit-lamp biomicroscopy showed characteristic irregular gray opacities in Bowman’s layer in each dystrophy: a geographic pattern in RBCD and a honeycomb pattern in TBCD. In each dystrophy, distinct characteristic deposits were observed by AS-OCT as a banding lesion in Bowman’s layer and its adjacent epithelium/stroma. In RBCD, the banding lesion was highly reflective and sharply margined at the stroma. In contrast, deposits in TBCD in the same layer showed a saw-tooth pattern toward the epithelium and poorly margined at the stroma.

Conclusion

AS-OCT is able to clearly identify characteristic in vivo corneal microstructural changes associated with RBCD and TBCD. As a result, in vivo differentiation of RBCD and TBCD can be achieved.

Pathogenesis and treatments of TGFBI corneal dystrophies

Transforming growth factor beta-induced (TGFBI) corneal dystrophies are a group of inherited progressive corneal diseases. Accumulation of transforming growth factor beta-induced protein (TGFBIp) is involved in the pathogenesis of TGFBI corneal dystrophies; however, the exact molecular mechanisms are not fully elucidated. In this review article, we summarize the current knowledge of TGFBI corneal dystrophies including clinical manifestations, epidemiology, most common and recently reported associated mutations for each disease, and treatment modalities. We review our current understanding of the molecular mechanisms of granular corneal dystrophy type 2 (GCD2) and studies of other TGFBI corneal dystrophies. In GCD2 corneal fibroblasts, alterations of morphological characteristics of corneal fibroblasts, increased susceptibility to intracellular oxidative stress, dysfunctional and fragmented mitochondria, defective autophagy, and alterations of cell cycle were observed. Other studies of mutated TGFBIp show changes in conformational structure, stability and proteolytic properties in lattice and granular corneal dystrophies. Future research should be directed toward elucidation of the biochemical mechanism of deposit formation, the relationship between the mutated TGFBIp and the other materials in the extracellular matrix, and the development of gene therapy and pharmaceutical agents.

Clinical and genetic aspects of the TGFBI-associated corneal dystrophies

Corneal dystrophies are a group of inherited disorders localized to various layers of the cornea that affect corneal transparency and visual acuity. The deposition of insoluble protein materials in the form of extracellular deposits or intracellular cysts is pathognomic. Mutations in TGFBI are responsible for superficial and stromal corneal dystrophies. The gene product, transforming growth factor β induced protein (TGFBIp) accumulates as insoluble deposits in various forms. The severity, clinicopathogenic variations, age of the onset, and location of the deposits depend on the type of amino acid alterations in the protein. Until 2006, 38 different pathogenic mutants were reported for the TGFBI-associated corneal dystrophies. This number has increased to 63 mutants, reported in more than 30 countries. There is no effective treatment to prevent, halt, or reverse the deposition of TGFBIp. This review presents a complete mutation update, classification of phenotypes, comprehensive reported incidents of various mutations, and current treatment options and their shortcomings. Future research directions and possible approaches to inhibiting disease progression are discussed.

Granular corneal dystrophy type 2 is associated with morphological abnormalities of meibomian glands

AIMS

To investigate morphological changes in meibomian glands in patients with granular corneal dystrophy type 2 (GCD2) using non-invasive meibography.

METHODS

Eleven patients (3 men and 8 women) with GCD2, and sex-matched and age-matched healthy volunteers as a controls were enrolled in this study. The diagnosis of GCD2 was confirmed by transforming growth factor β-induced (TGFBI) gene analysis using direct sequencing in exon 4 of TGFBI gene. Meibography was performed in the right eye of the studied cases. Meiboscore was determined according to the morphology of meibomian gland and classified into four grades; grade 0 (no meibomian gland loss), grade 1 (loss less than one-third the total area of meibomian glands), grade 2 (area loss between one-third and two-thirds of the total area), and grade 3 (area loss greater than two-thirds of the total).

RESULTS

R124H mutation was detected in all patients with GCD2. Extinguishing or shortening of the meibomian glands was observed in patients with GCD2. The meiboscore was 3.8±1.3 in patients with GCD2 and 1.3±1.1 in the control group, showing significant difference between two groups (Mann-Whitney U-test, p=0.042).

CONCLUSIONS

In GCD2, corneal deposits, and also morphological abnormalities of meibomian glands, such as obstruction or shortening, were found. Since abnormal phospholipid deposition is noted in GCD2, these results are interesting because phospholipid is possibly secreted from the meibomian gland.

Electrolysis for corneal opacities in a young patient with superficial variant of granular corneal dystrophy (Reis-Bücklers corneal dystrophy)

PURPOSE

To report the efficacy of electrolysis as a treatment of corneal opacities in a young patient with the superficial variant of granular corneal dystrophy.

DESIGN

Interventional case report.

METHODS

An 11-year-old boy presented with subepithelial opacities in both eyes. His visual acuity was 0.2 in the left eye; he received corneal electrolysis under topical anesthesia.

RESULTS

The electrolysis, which required only 5 minutes, resulted in the disappearance of the subepithelial opacities. His visual acuity improved to 0.4 on the next day and was 1.0 eight months later. The corneal curvature and thickness were not altered by the electrolysis.

CONCLUSIONS

Corneal electrolysis proved to be an effective treatment for subepithelial opacities, and we recommend electrolysis as an effective and simple treatment for young patients with SGCD.

Electrolytic removal of recurrence of granular corneal dystrophy

AIMS

To report the efficacy of corneal electrolysis for the treatment of recurrent corneal opacities at the subepithelial region or at the host-graft interface of the stroma in granular corneal dystrophy (GCD).

METHODS

In patients with recurrences of opacities at the host-graft interface of the stroma after lamellar keratoplasty, the deep aspect of the graft was partially separated from host tissue to expose the deposits. The graft was everted, and electrolysis was applied directly to remove the deposits attached to both surfaces of the host and the graft. Then the graft was returned to its place and sutured. In patients with diffuse subepithelial opacities following penetrating keratoplasty, electrolysis was applied directly to the corneal surface.

RESULTS

Deposits in the subepithelial region or at the host-graft interface of the stroma disappeared following treatment, and vision recovered. However, GCD recurred 2-3 years after the treatment.

CONCLUSIONS

Corneal electrolysis is a simple, easy, and inexpensive way to remove deposits that recur after lamellar or penetrating keratoplasty for GCD.

Surgical do's and don'ts of corneal dystrophies

PURPOSE OF REVIEW

Characteristics of corneal dystrophies have been described with regards to such as location in the cornea, morphology, material composition, and recurrence after penetrating keratoplasty. The main goal of this review is to describe the surgical methods in treating corneal dystrophies.

RECENT FINDINGS

Laser in situ keratomileusis (LASIK) has been shown to aggravate corneal deposits in Avellino dystrophy exacerbation LASIK and hence should be avoided. Phototherapeutic keratectomy (PTK) has shown its usefulness in clearing opacities with visual improvement and prevents painful erosion, resulting in delay or postponement of corneal grafting in some corneal dystrophies. Mitomycin-C may be used topically in conjunction with PTK to reduce the recurrence of the opacities. Topical use of antibody to TGF-beta can also be considered to suppress recurrence of corneal opacities after PTK or lamellar keratectomy.

SUMMARY

Clinicians must become more adept at choosing a treatment depending on different genotypes and future studies on treatment of corneal dystrophies should be focused on establishing treatment of categorized corneal dystrophies based on their chromosomal mutation.