Recurrence of lattice corneal dystrophy caused by incomplete removal of stroma after deep lamellar 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.

New histopathologic and ultrastructural findings in Reis-Bücklers corneal dystrophy caused by the Arg124Leu mutation of TGFBI gene

Background

Reis-Bücklers corneal dystrophy (RBCD) was consistently reported as a corneal dystrophy only affected Bowman’s layer and superficial corneal stroma, and superficial keratectomy was a recommendation surgery for treatment in literatures. The study reported new histopathological and ultrastructural findings in RBCD caused by the Arg124Leu mutation of transforming growth factor induced (TGFBI) gene in a four-generation Chinese pedigree.

Methods

Subjects including eight patients and seven unaffected family members received slit-lamp biomicroscopy and photography. DNA was obtained from all subjects, and exons 4 and 11 to 14 of TGFBI gene were analyzed by polymerase chain reaction and the products were sequenced. Anterior segment optical coherence tomography (AS OCT) and in vivo confocal microscopy were conducted for ten eyes of five patients. Based on the results of AS OCT and in vivo confocal microscopy, deep anterior lamellar keratoplasty (DLKP) using cryopreserved donor cornea was applied for four eyes of four patients. Four lamellar dystrophic corneal buttons were studied by light and transmission electron microscopy, and TGFBI immunohistochemistry.

Results

Eight patients had typical clinical manifestations of RBCD presenting recurrent painful corneal erosion starting in their early first decades, along with age-dependent progressive geographic corneal opacities. TGFBI sequencing revealed a heterozygous mutation, Arg124Leu in all eight patients. Anterior segment optical coherence tomography and in vivo confocal microscopy showed the dystrophic deposits involved not only in subepithelial and superficial stroma, but also in mid- or posterior stroma in four examined advanced eyes. Light microscopy showed Bowman’s layer was absent, replaced by abnormal deposits stain bright red with Masson’s trichrome. In superficial cornea, the deposits stacked and produced three to five continuous bands parallel to the corneal collagen lamellae. In mid- to posterior stroma, numerous granular or dot- like aggregates were heavily scattered, and most of them presented around the nuclei of stromal keratocytes. Transmission electron microscopy revealed the multiple electron-dense rod-shaped deposits aggregated and formed a characteristic pattern of three to five continuous bands in superficial cornea, which were similar to those seen under light microscopy. In mid- to posterior stroma, clusters of rod-shaped bodies were scattered extracellular or intracellular of the stromal keratocytes between the stromal lamellae suggesting the close relationship between mutated proteins and keratocyte.

Conclusions

The study offer evidences indicating DLKP is a viable treatment option for advanced RBCD to avoid recurrence, and the mutated TGFBIp in dystrophic corneas are of keratocytes origin.

Fibril Core of Transforming Growth Factor Beta-Induced Protein (TGFBIp) Facilitates Aggregation of Corneal TGFBIp

Mutations in the transforming growth factor beta-induced (TGFBI) gene result in a group of hereditary diseases of the cornea that are collectively known as TGFBI corneal dystrophies. These mutations translate into amino acid substitutions mainly within the fourth fasciclin 1 domain (FAS1-4) of the transforming growth factor beta-induced protein (TGFBIp) and cause either amyloid or nonamyloid protein aggregates in the anterior and central parts of the cornea, depending on the mutation. The A546T substitution in TGFBIp causes lattice corneal dystrophy (LCD), which manifests as amyloid-type aggregates in the corneal stroma. We previously showed that the A546T substitution renders TGFBIp and the FAS1-4 domain thermodynamically less stable compared with the wild-type (WT) protein, and the mutant FAS1-4 is prone to amyloid formation in vitro. In the present study, we identified the core of A546T FAS1-4 amyloid fibrils. Significantly, we identified the Y571-R588 region of TGFBIp, which we previously found to be enriched in amyloid deposits in LCD patients. We further found that the Y571-R588 peptide seeded fibrillation of A546T FAS1-4, and, more importantly, we demonstrated that native TGFBIp aggregates in the presence of fibrils formed by the core peptide. Collectively, these data suggest an involvement of the Y571-R588 peptide in LCD pathophysiology.

Peripheral deep anterior lamellar keratoplasty using a cryopreserved donor cornea for Terrien's marginal degeneration

OBJECTIVE

To evaluate the clinical efficacy of peripheral deep anterior lamellar keratoplasty (DALK) using a cryopreserved donor cornea for Terrien's marginal degeneration (TMD).

METHODS

Thirty-one eyes of 27 patients with TMD underwent peripheral DALK using cryopreserved donor corneas. According to the distance between the inner edge of the lesion and the limbus, a ring-shaped or D-shaped DALK was performed. All grafts were stored at -20 °C. Cryopreserved corneoscleral rims were prepared for ring-shaped grafts and cryopreserved whole eyeballs were prepared for D-shaped grafts. The general conditions, intraoperative performance, postoperative corneal reconstruction, astigmatism, best corrected visual acuity (BCVA), and various complications were analyzed.

RESULTS

Ring-shaped DALK was performed in 28 eyes and D-shaped DALK was performed in 3 eyes. Postoperative follow-up time was (28.4±24.8) months. There was evidence of inflammation before surgery in 12 eyes (38.7%) and intraoperative perforation occurred in 13 eyes (41.9%). The corneal structures of all eyes were reconstructed. Postoperative astigmatism and BCVA showed improvement (both P=0.00) except for cases that underwent D-shaped DALK. Ten eyes (32.2%) developed transient ocular hypertension and one eye (3.2%) developed secondary glaucoma. No primary disease recurrence or corneal allograft rejection was observed.

CONCLUSIONS

Peripheral DALK for TMD using cryopreserved donor tissue is an effective technique that eliminates rejection and extends the use of donor eyes. Inflammatory history or intraoperative perforation has no adverse effect on graft recovery. However, D-shaped DALK did not achieve good visual outcomes.

Long-term comparison of full-bed deep anterior lamellar keratoplasty and penetrating keratoplasty in treating keratoconus

OBJECTIVE

To compare postoperative outcomes of full-bed deep anterior lamellar keratoplasty (DALK) with penetrating keratoplasty (PK) in treating keratoconus.

METHODS

Seventy-five eyes of 64 patients who received full-bed DALK and 52 eyes of 51 patients who received PK between June 2000 and August 2010 were included in this retrospective study. Full-bed DALK was performed using Yao's hooking-detaching technique. PK was performed using a standard technique. Intraoperative and postoperative complications, visual acuity, rejection, graft survival, endothelial cell density, corneal sensation recovery, and re-innervation were compared between the two groups.

RESULTS

A best correct visual acuity of 0.5 or better was achieved in 90.7% of eyes after full-bed DALK and in 92.3% of eyes after PK (P=0.75). By the fifth postoperative year, graft endothelial cell loss reached 34.6% in the PK group vs. 13.9% in the full-bed DALK group (P<0.001). There were no statistical differences in corneal sensitivity recovery or corneal re-innervation between the groups (P>0.05). Intraoperative microperforation occurred in seven out of 75 (9.3%) eyes with a temporally postoperative double anterior chamber in two eyes in the full-bed DALK group. Postoperative complications in the PK vs. the full-bed DALK groups respectively were: rejection (7.7% vs. 0%, P=0.015), high intraocular pressure (IOP) (46.2% vs. 1.3%, P<0.001), secondary glaucoma (9.6% vs. 0%, P=0.006), complicated cataract (19.2% vs. 0%, P<0.001), and wound dehiscence (9.6% vs. 0%, P=0.006).

CONCLUSIONS

Both full-bed DALK and PK can offer long-term satisfactory visual outcomes for keratoconus. Graft rejection, secondary glaucoma, complicated cataracts, and constant endothelial cell loss were observed in eyes only after PK.

Long-term comparison of full-bed deep lamellar keratoplasty with penetrating keratoplasty in treating corneal leucoma caused by herpes simplex keratitis

PURPOSE

To compare long-term outcomes of full-bed deep lamellar keratoplasty (DLK) with penetrating keratoplasty (PK) for treating corneal leucoma caused by herpes simplex keratitis (HSK).

DESIGN

Retrospective, comparative, interventional case series.

METHODS

setting: Institutional. patients: Inclusion criteria were patients with corneal scarring induced exclusively by HSK who underwent primary graft of full-bed DLK or PK and completed a minimum of 12 months postoperative follow-up. There was no significant difference of corneal scarring and vascularization between the 2 groups before surgery. Choosing PK or full-bed DLK depended on the patient's own willingness, except those patients with a preoperative endothelial cell count of less than 700 cells/mm(2) or whose endothelial cell count was undetectable were encouraged to undergo only PK. Exclusion criteria were patients with a past history of corneal perforation, nonprimary graft, non-HSK-related corneal scars, and failure to complete a minimum of 12 months of postoperative follow-up. Fifty-eight eyes of 58 patients in the full-bed DLK group and 63 eyes of 63 patients in the PK group met the inclusion criteria. main outcome measures: Postoperative managements, recurrence of HSK, graft rejection, graft survival rate, visual acuity, and corneal endothelial density.

RESULTS

The mean postoperative follow-up duration was 45.8 ± 30.9 months in the full-bed DLK group and 47.9 ± 27.2 months in the PK group (P = .70). As compared with the PK group, the full-bed DLK group experienced earlier suture removal (P = .01), needed fewer postoperative visits (P < .001), and had a higher proportion of eyes with full withdrawal of oral acyclovir (P < .001) and topical corticosteroid (P < .001). There were a total of 21 episodes of recurrent HSK in the PK group, more frequent than the 7 episodes in the full-bed DLK group, among which recurrent epithelial keratitis amounted to 13 episodes in the PK group, remarkably more frequent than the 1 episode in the full-bed DLK group. Twenty-six eyes (41.3%) encountered rejection episodes in the PK group, but no rejection episode was found in the full-bed DLK group (P < .001). In 14 eyes in the PK group, graft failure developed because of graft rejection, recurrence of HSK, or both, whereas only in 1 eye in the full-bed DLK group did graft failure develop because of recurrence of HSK (P = .001). The clear graft survival rate in the full-bed DLK group was significantly higher than that in the PK group (P = .01). Corneal endothelial cell density was stable from 1 month through 5 years in the full-bed DLK group, but 51.3% cell loss was found in the PK group at 5 years after surgery. At the last visit, 66.1% of eyes with full-bed DLK grafts and 50.9% of eyes with PK grafts achieved a best-correct visual acuity of 0.5 or better (P = .10).

CONCLUSIONS

Advantages of full-bed DLK over PK are no allograft rejection, longer graft survival, earlier drug withdrawal of topical steroid and oral acyclovir, less recurrence of HSK, and fewer follow-up visits. Full-bed DLK is preferable for treating HSK-induced corneal scarring with relatively healthy endothelium and with no history of perforation.

Pathogenic mutations of TGFBI and CHST6 genes in Chinese patients with Avellino, lattice, and macular corneal dystrophies

OBJECTIVE

To investigate gene mutations associated with three different types of corneal dystrophies (CDs), and to establish a phenotype-genotype correlation.

METHODS

Two patients with Avellino corneal dystrophy (ACD), four patients with lattice corneal dystrophy type I (LCD I) from one family, and three patients with macular corneal dystrophy type I (MCD I) were subjected to both clinical and genetic examinations. Slit lamp examination was performed for all the subjects to assess their corneal phenotypes. Genomic DNA was extracted from peripheral blood leukocytes. The coding regions of the human transforming growth factor β-induced (TGFBI) gene and carbohydrate sulfotransferase 6 (CHST6) gene were amplified by polymerase chain reaction (PCR) and subjected to direct sequencing. DNA samples from 50 healthy volunteers were used as controls.

RESULTS

Clinical examination showed three different phenotypes of CDs. Genetic examination identified that two ACD subjects were associated with homozygous R124H mutation of TGFBI, and four LCD I subjects were all associated with R124C heterozygous mutation. One MCD I subject was associated with a novel S51X homozygous mutation in CHST6, while the other two MCD I subjects harbored a previously reported W232X homozygous mutation.

CONCLUSIONS

Our study highlights the prevalence of codon 124 mutations in the TGFBI gene among the Chinese ACD and LCD I patients. Moreover, we found a novel mutation among MCD I patients.

A novel technique for performing full-bed deep lamellar keratoplasty

In recent years, deep lamellar keratoplasty (DLKP) has become an alternative surgical approach successfully applied to the treatment of opaque cornea with normal endothelial function. However, techniques for performing DLKP are not standardized and have not been perfected compared with penetrating keratoplasty. We developed a technique of stromal hooking and viscoelastic detaching to create a full-bed exposure of Descemet membrane (DM) for DLKP grafting. The surgical procedures include trephining the recipient stroma, exposure of DM by stromal hooking process using a forceps tooth as hook, detaching stroma from DM by injecting viscoelastic between the 2 layers, removing whole stroma around the trephined margin to obtain full-bed exposure of DM, and grafting cryopreserved donor button. Unlike previously reported techniques, our technique does not attempt directly to dissect stroma but to detach the stromal layer from DM by injecting viscoelastic. Using this technique, among 172 eyes we achieved full-bed DLKP in 1 attempt of the procedure in 42 (24.4%) eyes, in 2 attempts in 65 (37.8%) eyes, and in 3 attempts in 45 (26.2%) eyes. Eighteen of 172 (10.5%) eyes had microperforation of DM, but DLKP surgery was nonetheless completed. Two (1.2%) eyes needed conversion to penetrating keratoplasty because of large perforation of DM. We present a detailed illustration of our surgical procedures for performing full-bed DLKP in the hope that it may be of help to ophthalmologists.