Exacerbation of Avellino corneal dystrophy after LASIK in North America

Unilateral Granular Type 2 Corneal Dystrophy With Exacerbation After LASIK

PURPOSE

The aim of this study was to report a case of unilateral granular corneal dystrophy type 2 (GCD2) with exacerbation after bilateral laser in situ keratomileusis (LASIK).

METHODS

Clinical evaluation, Scheimpflug imaging, anterior segment optical coherence tomography (AS-OCT), cytology, and genetic testing were used to confirm the diagnosis of unilateral GCD2 with exacerbation after bilateral LASIK. Detailed literature review for possible unilateral GCD2 presentations was performed.

RESULTS

A 54-year-old White woman presented with blurred vision in her left eye and a history of bilateral LASIK performed 8 years before. Examination revealed dense opacities in the left cornea only, which were confirmed to be confined to the LASIK interface and adjacent corneal stromal tissue, as determined by AS-OCT. The patient underwent flap lift, interface debris removal, and stromal bed phototherapeutic keratectomy. Cytological analysis showed eosinophilic corneal stromal deposits that stained with trichrome stain and were congophilic on Congo red stain. Genetic testing was positive for heterozygous GCD2 transforming growth factor β-induced gene ( TGFBI ), c.371G>A, p.R124H mutation. There were no opacities identifiable in the right eye on serial slit-lamp examination, Scheimpflug imaging, or OCT imaging at 4 or 8 years after bilateral LASIK. Literature review failed to identify any previous reports of unilateral GCD2.

CONCLUSIONS

This is the first known reported case of unilateral granular corneal dystrophy type 2. LASIK is contraindicated in eyes with corneal stromal dystrophies related to mutations in TGFBI as both flap creation and laser ablation can exacerbate visually significant opacity formation. Scheimpflug and AS-OCT imaging are useful to identify opacities in GCD2.

Novel Manifestation of Corneal Dystrophy After Keratorefractive Surgery

PURPOSE

This study aimed to report cases of bilateral corneal Bowman layer deposits in 4 patients with a history of keratorefractive surgery. To our knowledge, this condition has not previously been reported and should be distinguished from granular corneal dystrophy type 2 and other corneal dystrophies.

METHODS

We reviewed all available medical records that were collected between January 2010 and December 2021 at a tertiary referral center and performed whole-exome sequencing to provide diagnostic information.

RESULTS

Four patients exhibited similar bilateral corneal deposits that were observed more than 10 years after keratorefractive surgery. The patients' ages ranged from 36 to 53 years; 3 of the 4 patients were female. Three patients received laser in situ keratomileusis surgery, and 1 received radial keratotomy. All 4 patients denied having a family history of ocular diseases and reported an uneventful postoperative course. On examination, the best-corrected visual acuity ranged from 6/10 to 6/6 in all 4 patients. Slit-lamp examination revealed bilateral superficial corneal deposits involving the central cornea, and anterior segment optical coherence tomography revealed hyperreflective deposits located in the Bowman layer. Such unique manifestations suggested corneal dystrophy; thus, whole-exome sequencing was performed on all 4 patients. Only 1 patient exhibited a missense mutation in TGFBI . We further analyzed common de novo mutations to explore possible candidate genes associated with this presentation.

CONCLUSIONS

We report a rare entity of presumed corneal dystrophy with deposits located in the Bowman layer in 4 patients who had received keratorefractive surgery. Clarifying the underlying pathophysiology and genetic predisposition of this disease may aid in diagnosing and preventing potential complications after keratorefractive surgery.

Mini-Review: Clinical Features and Management of Granular Corneal Dystrophy Type 2

Granular corneal dystrophy type 2 (GCD2) is an autosomal dominant corneal stromal dystrophy that is caused by p.Arg124His mutation of transforming growth factor β induced (TGFBI) gene. It is characterized by well demarcated granular shaped opacities in central anterior stroma and as the disease progresses, extrusion of the deposits results in ocular pain due to corneal epithelial erosion. Also, diffuse corneal haze which appears late, causes decrease in visual acuity. The prevalence of GCD2 is high in East Asia including Korea. Homozygous patients show a severe phenotype from an early age, and the heterozygote phenotype varies among patients, depending on several types of compound heterozygous TGFBI mutations. In the initial stage, conservative treatments such as artificial tears, antibiotic eye drops, and bandage contact lenses are used to treat corneal erosion. Different surgical methods are used depending on the depth and extent of the stromal deposits. Phototherapeutic keratectomy removes anterior opacities and is advantageous in terms of its applicability and repeatability. For deeper lesions, deep anterior lamellar keratoplasty can be used as the endothelial layer is not always affected. Recurrence following these treatments are reported within a wide range of rates in different studies due to varying definition of recurrence and follow-up period. In patients who have undergone corneal laser vision-correction surgeries such as photorefractive keratectomy, LASEK, or LASIK including SMILE surgery, corneal opacity exacerbates rapidly with severe deterioration of visual acuity. Further investigations on new treatments of GCD2 are necessary.

Bilateral post-LASIK exacerbation of granular corneal dystrophy with epithelial ingrowth

A male patient in his 30s, with a history of bilateral microkeratome-assisted myopic laser-assisted in situ keratomileusis (LASIK) 8 years ago at another centre, presented to us with gradually progressive diminution of vision and glare in both eyes for the last 4 years. On presentation, uncorrected distance visual acuity (UDVA) was 6/24 and 6/15 in the right eye and left eye, respectively, with normal intraocular pressures. Slit-lamp examination and anterior segment optical coherence tomography revealed well-defined white deposits, limited to an area within the LASIK flap. The deposits were confluent, at the level of the LASIK flap interface, and few discrete opacities were present in the posterior stroma. His father also had a similar clinical picture in both eyes. A diagnosis of both eyes post-LASIK exacerbation of granular corneal dystrophy with epithelial ingrowth was made. He underwent right eye femtosecond laser-assisted sutureless superficial anterior lamellar keratoplasty. At 6-month follow-up, UDVA improved to 6/12 with graft clarity of 4+ and coexistent grade 1 epithelial ingrowth.

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.

Phenotypes of Granular Corneal Dystrophy Type 2 among Koreans in Their Twenties

Purpose: Granular corneal dystrophy type 2 (GCD2) is a hereditary disease that features granular and lattice stromal deposits in the cornea. There are homozygotes and heterozygotes and the opacities are exacerbated by corneal trauma or surgery, such as laser in situ keratomileusis (LASIK). As there is individual variability in GCD2 phenotypes, we investigated various corneal features of GCD2 patients in their twenties, the main age group for refractive surgery.Methods: From genetically confirmed GCD2 patients who had an R124H mutation of the transforming growth factor β induced (<i>TGFBI</i>) gene at age 20 to 29 years, we chose representative patients: one homozygote; one compound heterozygote; one simple heterozygote with a severe phenotype with many granular deposits; one common heterozygote; and four heterozygotes with normal corneas. The corneas of all patients were subject to slit-lamp examination and photographed.Results: The homozygote had confluent granular deposits covering the cornea. The compound heterozygote had granular and lattice deposits covering the center of the cornea. The patient with a severe phenotype had more than 30 granular deposits in one eye, but was a simple GCD2 heterozygote, verified by full-sequencing of the <i>TGFBI</i> gene. In the four patients with normal corneas, a single small lesion was subsequently detected during follow-up in two, at 3 weeks and 6 months, respectively. Both corneas were judged clear at chance examinations.Conclusions: Among Koreans in their twenties, GCD2 patients have various phenotypes, from clear corneas to severe confluent opacities. There are GCD2 heterozygotes with nearly clear corneas, so caution must be taken when choosing patients for refractive surgery.

Deterioration of Avellino corneal dystrophy in a Chinese family after LASIK

AIM

To reveal the importance of TGFBI gene screening for candidates with a family history of corneal disease or granular opacities in corneal stroma before refractive surgery.

METHODS

A 37-year-old male (proband) underwent bilateral laser-assisted in situ keratomileusis (LASIK) in 2002, with right vision decreased significantly in 2006. The proband and other 32 members of the family underwent a detailed ophthalmic examination, including vision acuity, intraocular pressure, slit-lamp photograph, fundus examination, optical coherence tomography (OCT) of cornea, and in vivo confocal microscope (IVCM) and peripheral blood was used for genomic DNA extraction. Seventeen TGFBI gene exons were analyzed via polymerase chain reaction amplification and direct sequencing.

RESULTS

Slit-lamp, IVCM, and OCT images showed that a large amount of dense and confluent granular opaque were seen at the interfaces of the flap and remnant stromal bed in right and light degree in left eye. Sanger sequencing showed that there was a 371G>A mutation (CGC>CAC) in exon 4, which indicated that he harbored a heterozygote R124H mutation, identifying the diagnosis of Avellino corneal dystrophy (ACD). Among the other 32 family members, 6 of them harbored the identical mutation to that in the proband.

CONCLUSION

ACD will worsen and recur after LASIK. Preoperative gene-screening for TGFBI mutations is important in diagnosing ACD.

Laser refractive surgery in corneal dystrophies

Twenty-eight case reports and case series published between 2000 and 2019 concerning laser refractive surgery in patients with corneal dystrophies, resulting in 173 eyes from 94 patients, were included in this systematic review. Best results were achieved in posterior corneal polymorphous and Cogan dystrophy. Unfavorable results were found in Avellino dystrophy and Fuchs endothelial corneal dystrophy (FECD). Photorefractive keratectomy was not indicated in Meesmann and Avellino dystrophy. Laser in situ keratomileusis was indicated in posterior polymorphous corneal dystrophy but not in FECD, Avellino, or Cogan dystrophy. Small-incision lenticule extraction and other dystrophies such as lattice, fleck, Lisch, or François did not achieve enough scientific evidence to report any recommendation.

Exacerbation of Granular Corneal Dystrophy Type 2 After Small Incision Lenticule Extraction

PURPOSE

To report the outcome of unilateral small incision lenticule extraction (SMILE) in a patient with granular corneal dystrophy type 2 (GCD2).

METHODS

Slit-lamp photography and Fourier domain optical coherence tomography were used to document the clinical course and appearance of the corneas in a patient with genetically determined GCD2 who underwent unilateral SMILE in the right eye.

RESULTS

Slit-lamp examination of a 23-year-old woman revealed 2 faint opacities at the surgical interface approximately 2 months after the SMILE procedure had been performed on her right eye. Nine and 3 typical GCD2 deposits located immediately beneath the Bowman layer were observed in the right and left corneas, respectively. Over time, the deposits at the interface increased in size, density, and number in the right eye. Fourier domain optical coherence tomography performed 33 months after the SMILE procedure revealed deposits at the SMILE interface that were distinct from those located immediately beneath the Bowman layer. The severity of disease exacerbation was less in this patient than what is typically observed in others who have undergone laser-assisted in situ keratomileusis or photorefractive keratectomy.

CONCLUSIONS

SMILE is contraindicated in patients with GCD2, as are other corneal refractive surgical procedures. This case highlights the importance of genetic testing before the performance of refractive corneal procedures-especially for patients with corneal opacities on preoperative slit-lamp examination or a family history of corneal disease compatible with that of a corneal dystrophy.

A recognition survey of granular corneal dystrophy type 2 genetic detection in China

AIM

To evaluate the feasibility of promoting genetic detection for granular corneal dystrophy type 2 (GCD₂) by a questionnaire conducted among citizens in five cities in China.

METHODS

The data were collected by questionnaire, and analyzed by Chi-square test and one-tailed t test in IBM SPSS statistics.

RESULTS

Based on the survey data on the awareness of GCD₂ genetic detection in this study and the positive predictive analysis report of the citizens in five cities in China, the vast majority (84.2%) of respondents had never heard of it and did not know that GCD₂ patients have been prohibited from performing excimer surgery that can deteriorate GCD₂ patients' condition even leading to blindness. Though 3.4% of patients understood GCD₂ very much, they have no idea that GCD₂ could not be 100% accuracy diagnosed by the conventional inspection methods.

CONCLUSION

It is feasible and necessary to use GCD₂ genetic detection as an excimer preoperative examination project. In order to promote the development of detection project, a few improvements should be carried out in terms of the promoting efforts, costs, and research progress.

Long-term Clinical Outcomes of Phototherapeutic Keratectomy in Corneas With Granular Corneal Dystrophy Type 2 Exacerbated After LASIK

PURPOSE

To investigate the long-term clinical outcomes and recurrence patterns of phototherapeutic keratectomy (PTK) in patients with granular corneal dystrophy type 2 (GCD2) exacerbated after LASIK.

METHODS

Fifty-one patients (76 eyes) with GCD2 exacerbated after LASIK who underwent PTK between January 2007 and February 2017 were included. Participants underwent ophthalmic examination, including slit-lamp microscopy, corrected distance visual acuity (CDVA), slit-lamp photography, and Fourier domain optical coherence tomography at preoperative and postoperative visits. PTK was performed using VISX S4 IR (VISX, Inc., Santa Clara, CA). Visual acuity, complications, interval, and contributing factors of recurrence were evaluated.

RESULTS

The follow-up period ranged from 1 to 108 months (mean: 35.22 months). The mean logMAR CDVA was 0.55 ± 0.43 (Snellen equivalent 20/80) preoperatively and 0.09 ± 0.43 (Snellen equivalent 20/25) at 3 months postoperatively. Forty-five (61.6%) eyes developed biomicroscopic recurrence at a mean of 18.6 months after PTK; 20 (27.4%) eyes developed significant recurrence at a mean of 31.3 months after PTK. The flap removal group demonstrated better CDVA at 3 years after surgery and lower recurrence and complication rates than the flap conservation group. Multivariate analysis revealed that flap removal remarkably reduced the risk of both any sign of and significant recurrence.

CONCLUSIONS

PTK improved corneal transparency and visual acuity in patients with GCD2 exacerbated after LASIK, although GCD2 eventually recurred. PTK with flap removal was superior to PTK with flap conservation in terms of visual acuity, recurrence, and complications. [J Refract Surg. 2018;34(2):132-139.].

Post-LASIK exacerbation of granular corneal dystrophy type 2 in members of a chinese family

PurposeThe post-LASIK exacerbation of corneal dystrophy, otherwise asymptomatic, is almost exclusively associated with the TGFBI gene mutations at codon 124 in exon 4 and codon 555 in exon 12. It is our intention to demonstrate that the pre-operative genetic screening for TGFBI mutations should be mandatory for refractive surgery candidates.Patients and MethodsIn this study, we reviewed the proband's post-LASIK slit-lamp and in vivo confocal microscopy images and genetic testing results, and performed genetic testing on eleven additional members of the family to investigate the penetrance of corneal dystrophy in asymptomatic members who carry the mutation.ResultsThe proband demonstrated a post-LASIK exacerbation of Granular Corneal Dystrophy type 2 (GCD2), identified as a TGFBI R124H mutation. Three of the 11 family members tested positive for the same R124H mutation as the proband.ConclusionThe lesson learned from this case is that the genetic screening of TGFBI mutations must be incorporated into the pre-operative screening procedures to prevent exacerbation and recurrence, which eventually could lead to the need for a corneal transplant.

Prevalence of transforming growth factor β-induced gene corneal dystrophies in Chinese refractive surgery candidates

PURPOSE

To determine the prevalence of the transforming growth factor (TGF) β-induced gene corneal dystrophies in refractive surgery candidates in China.

SETTING

Five hospitals in China.

DESIGN

Prospective case series.

METHOD

Refractive surgical candidates from 5 preselected eye hospitals/centers in China were recruited after providing informed consent. All patients had slitlamp biomicroscopy and collection of a buccal swab as a source of DNA for screening of the TGF β-induced gene for the 5 most common mutations associated with Reis-Bückler corneal dystrophy, Thiel-Behnke corneal dystrophy, granular corneal dystrophy type 1, granular corneal dystrophy type 2, and lattice corneal dystrophy type 1.

RESULTS

Of the 2068 refractive surgery candidates analyzed, 4 had corneal opacities in both eyes on slitlamp examination. Screening for the TGF β-induced gene found the heterozygous p.R124H mutation associated with granular corneal dystrophy type 2 in each of the 4 individuals with corneal opacities as well as in a fifth individual who did not have any corneal opacities, for a prevalence of 0.24%. Exacerbation of dystrophic corneal deposition developed after laser refractive surgery in 2 individuals who did not have preoperative TGF β-induced gene screening.

CONCLUSIONS

The prevalence of the TGF β-induced gene corneal dystrophies in Chinese refractive surgery candidates was estimated to be approximately 0.24%. Genetic testing is recommended to identify and exclude from candidacy all individuals with a TGF β-induced gene dystrophy before elective keratorefractive surgery to avoid causing accelerated postoperative dystrophic deposition.

TGFBI Gene Mutation Analysis of Clinically Diagnosed Granular Corneal Dystrophy Patients Prior to PTK: A Pilot Study from Eastern China

This study investigated the TGFBI gene mutation types in outpatients clinically diagnosed with granular corneal dystrophy (GCD) prior to phototherapeutic keratectomy (PTK), also calculated the mutation rate of subjects with normal corneas, but positive family history. Clinical GCD outpatients and consanguineous family members were enrolled in this study. Among total 42 subjects: 24 patients from 23 unrelated families had typical signs of GCD on corneas; 5 patients from 5 unrelated families had atypical signs; 13 subjects from 11 unrelated families had no corneal signs but positive family history. Using Avellino gene test kit, the TGFBI mutation detection was performed on DNA samples from all subjects. 36 subjects were detected to carry heterozygous TGFBI gene mutations. Among 24 clinical GCD patients, the proportion of R124H, R555Q, R124L, R555W and R124C were 37.5%, 16.7%, 25.0%, 20.8% and 0%, respectively, and 2 patients had been diagnosed with GCD according to the opacities thriving after LASIK (R124H) and PRK (R555W). The mutation rate of 13 subjects having no signs but positive family history was 69.2%. R124H mutation is the most prominent mutation type among GCD outpatients in Eastern China. It is recommended to conduct gene detection for patients with positive family history prior to refractive surgeries.

Sensitive Surface Enhanced Raman Scattering-Based Detection of a BIGH3 Point Mutation Associated with Avellino Corneal Dystrophy

Surface enhanced Raman scattering (SERS) is highly useful for sensitive analytical sensing; however, its practical availability for detecting a point mutation associated with disease in clinical sample was rarely proved. Herein, we present a toehold-mediated, DNA displacement-based, SERS sensor for detecting point mutations in the BIGH3 gene associated with the most common corneal dystrophies (CDs) in a clinical setting. To diagnose Avellino corneal dystrophy (ACD), selectivity was ensured by exploring optimal DNA displacement conditions such as length of toehold and hybridization temperature. A SERS-efficient Ag@Au bimetallic nanodendrite was employed to ensure sensitivity. Optimization for a clinical setting showed that discrimination was maximized when toehold length was 6-mer (T6), and hybridization temperature was 36 °C. On the basis of tests that used clinical homozygous and heterozygous CD samples, a single-base mismatched DNA sequence was identifiable within 30 min with a limit of detection (LOD) of 400 fM. From the results, we conclude that our toehold-mediated, DNA displacement-based, SERS sensor allows a rapid and sensitive detection of a BIGH3 gene point mutation associated with Avellino corneal dystrophy, indicating the practical ability of the method to diagnose genetic diseases caused by point mutations.

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.

Therapeutic flap amputation for atypical LASIK flap and interface abnormalities

PURPOSE

To describe LASIK flap amputation as a therapeutic option for patients with atypical refractory flap complications.

METHODS

Case series and literature review.

RESULTS

Seven eyes of 6 patients underwent flap amputation for various atypical indications, including non-infectious flap/interface opacity (3 patients), irregular astigmatism on the flap surface (3 patients), and chronic pain (concurrent in 2 patients with irregular astigmatism). In each case, conservative measures were ineffective. All patients had symptomatic improvement and improved corrected visual function after amputation; however, uncorrected distance visual acuity worsened in 2 patients, manifest refraction worsened in 3 patients, and irregular astigmatism increased in 2 patients.

CONCLUSIONS

Flap amputation is a reasonable alternative to improve corrected acuity in select cases with significant flap opacities or irregular astigmatism unresponsive to conservative measures, but uncorrected acuity and irregular astigmatism may worsen and should be discussed during the informed consent process.

LASIK and surface ablation in corneal dystrophies

Corneal dystrophies are a rare group of hereditary disorders, that are bilateral, non-inflammatory, and progressive. Clinically, they can be classified based on the anatomic layer of the cornea affected. Refractive surgery and phototherapeutic keratectomy (PTK) can be performed with caution in patients with certain corneal dystrophies, but should be avoided in others. For epithelial basement membrane dystrophy, photorefractive keratectomy (PRK) is the procedure of choice for treatment of refractive error, and PTK may be performed for the treatment of recurrent erosions or irregular astigmatism. PRK and laser-assisted in situ keratomileusis (LASIK) have been associated with exacerbation of combined granular-lattice corneal dystrophy. LASIK and PRK appear to be safe in mild forms of posterior polymorphous corneal dystrophy, whereas LASIK should be avoided in Fuchs dystrophy. The safety of refractive surgery and PTK in the remainder of epithelial, Bowman layer, and stromal dystrophies has yet to be established.

Analysis of deposit depth and morphology in granular corneal dystrophy type 2 using fourier domain optical coherence tomography

PURPOSE

Granular corneal dystrophy type 2 (GCD2) causes the formation of corneal deposits having 3 different morphological types. We used Fourier domain optical coherence tomography to assess the depths of each type according to the morphology.

METHODS

A prospective study was performed in 54 eyes of 54 heterozygous patients with GCD2. Corneal deposits of 54 patients with GCD2 were classified into 3 morphological types: type 1, diffuse haze; type 2, granular shape (2 subgroups: type 2a, round granulated and type 2b, round spiculated); and type 3, linear shape (2 subgroups: type 3a, short side branched and type 3b, long side branched). Using Fourier domain optical coherence tomography, we measured the distances from the Bowman layer to the upper surface of the deposits (USBL), to the lower surface of the deposits (LSBL), and the thickness of the deposits (TD). The deposits formed along the flap interface were also examined among 19 patients who had LASIK.

RESULTS

Types 1 and 2 deposits were always adjacent to the Bowman layer; thus the USBLs for each were 0.0 ± 0.0 μm, whereas that of type 3 deposits was 65.4 ± 48.0 μm (P < 0.0001). The LSBL and TD of linear deposits with long side branches (type 3) (313.3 ± 71.4 and 246.2 ± 71.9 μm) were greater than those of type 1 (47.7 ± 10.2 and 47.7 ± 10.2 μm) and type 2 (91.3 ± 39.5 and 91.3 ± 39.5 μm) (P < 0.0001). There were no differences in the measurements between the subgroups type 2a and type 2b or between types 3a and 3b. USBL of the laser in situ keratomileusis group was 54.5 ± 29.8 μm.

CONCLUSIONS

The depths of corneal deposits in patients with GCD2 were associated with the morphology of the deposits. The linear deposits were located most deeply in the cornea, followed by granular deposits and diffuse haze moving anteriorly. Several deposits have distinct depths according to the morphological types.

TGFB1-induced extracellular expression of TGFBIp and inhibition of TGFBIp expression by RNA interference in a human corneal epithelial cell line

PURPOSE

To report the increased production of extracellular transforming growth factor β-induced protein (TGFBIp) by human corneal epithelial cells (HCECs) after induction by TGFB1 and the inhibition of TGFBIp production in induced and noninduced HCECs by RNA interference (RNAi).

METHODS

HCECs were cultured in serum-free medium and treated with 0 or 10 ng/mL TGFB1 over a period of 72 hours. Commercially available siRNAs targeting TGFBI mRNA were mixed with a transfection reagent and used to reverse transfect TGFB1-induced and noninduced HCECs. Extracellular and intracellular concentrations of TGFBIp were measured by ELISA and Western blot analysis, respectively, and TGFBI RNA was assayed using semiquantitative RT-PCR.

RESULTS

HCECs constitutively express TGFBIp, and treatment with TGFB1 results in up to a fourfold increase in the amount of extracellular TGFBIp. Four commercially available siRNAs targeting TGFBI mRNA produced a >70% decrease in extracellular TGFBIp within 48 hours after transfection of noninduced HCECs but a <25% decrease in extracellular TGFBIp by 48 hours after transfection of TGFB1-induced HCECs. The suppression of extracellular TGFBIp production correlated with a decrease in intracellular TGFBIp production and TGFBI mRNA expression after transfection.

CONCLUSIONS

Extracellular TGFBIp expression by HCECs is increased several fold after exposure to TGFB1. Both HCEC-constitutive and HCEC-induced TGFBIp production can be inhibited with RNA interference, though the effect was greater and lasted longer for constitutive than induced TGFBIp production. Given that the corneal deposits in the TGFBI dystrophies consist of TGFBIp derived from HCECs, RNAi represents a potential means to inhibit primary dystrophic deposit formation and recurrence after surgical intervention.

Clinical findings and treatments of granular corneal dystrophy type 2 (avellino corneal dystrophy): a review of the literature

OBJECTIVES

To review the literature about clinical findings and treatments of granular corneal dystrophy type 2 (GCD2).

METHODS

Various literatures on clinical findings, exacerbations after refractive corneal surgery, and treatment modalities of GCD2 were reviewed.

RESULTS

GCD2 is an autosomal dominant disease. Mutation of transforming growth factor beta-induced gene, TGFBI, or keratoepithelin gene in human chromosome 5 (5q31) is the key pathogenic process in patient with GCD2. Corneal trauma activates TGFBI and then it overproduces transforming growth factor beta-induced gene protein (TGFBIp), which is main component of the corneal opacity. Refractive corneal surgery is a popular procedure to correct refractive error worldwide. However, several cases about exacerbation of GCD2 after corneal refractive surgery such as photorefractive keratectomy, laser in situ keratomileusis, and laser epithelial keratomileusis have been reported. The opacities deteriorate patient's best-corrected visual acuity. Recurrence-free interval varies many factors such as the type of procedure the patient had received and the genotype of the patient. To treat the opacities in GCD2, phototherapeutic keratectomy, lamellar keratoplasty, deep lamellar keratoplasty, and penetrating keratoplasty (PKP) were used. However, the recurrence is still an unsolved problem.

CONCLUSIONS

Perfect treatment of exacerbation after corneal surface ablation does not exist until now. To prevent exacerbation, refractive surgeons must do a careful preoperative examination of candidates in refractive surgeries.

Prevalence of granular corneal dystrophy type 2 (Avellino corneal dystrophy) in the Korean population

PURPOSE

This study investigates the prevalence of granular corneal dystrophy type 2 (GCD2; Avellino corneal dystrophy) in the Korean population.

METHODS

GCD2 homozygotes were identified through a collaboration of Korean referral centers for corneal disease. The genetic status of the patients and their immediate families were verified by DNA analysis. A lower bound for the gene prevalence was calculated using a model based on the Hardy-Weinberg principle. A second population-based model was developed to correct for known underestimation in the primary model. The corrected model used population data from the 2005 Korean census and fertility rates from historical Korean census data.

RESULTS

We identified 21 individuals homozygous for GCD2 (R124H mutation) from 16 Korean families. From this, we estimate that the overall prevalence (combining heterozygotes and homozygotes) is at least 8.25 affected persons/10,000 persons. Our corrected estimate for overall prevalence is 11.5 affected persons/10,000 persons.

CONCLUSION

We present the first estimate of the prevalence of GCD2. Although uncommon, the prevalence of GCD2 in Korea is greater than anticipated. We believe that our approach could potentially be applied to estimating the prevalence of other rare diseases.

Utility and efficacy of TGFBI mutational analysis for disease detection

Current knowledge of the genetic variation associated with TGFBI-associated corneal dystrophies has highlighted the possibility of de novo mutations, and also recurrence after refractive surgery in apparently asymptomatic individuals. This means that genetic testing for the most common variants is considered desirable, particularly in the refractive clinical setting. To be a useful clinical adjunct, however, genetic testing must be time and cost effective. Yoo and coworkers propose a nanoparticle microarray for rapid detection of TGFBI mutations. The advantages and limitations of these nanoparticle microarrays need to be compared with current methods of mutation detection. Clinicians should include genetic testing in the clinical work-up, and must consider the ethical principles of making a genetic diagnosis, as well as the marked variance in clinical presentation in this group of dystrophies.

Avellino corneal dystrophy worsening after laser in situ keratomileusis: further clinicopathologic observations and proposed pathogenesis

PURPOSE

To study the nature of the deposits in Avellino corneal dystrophy (ACD) worsening after laser in situ keratomileusis (LASIK), and suggest a mechanism for histopathogenesis.

DESIGN

Interventional case report.

METHODS

A 28-year-old woman previously diagnosed with bilateral ACD underwent bilateral LASIK. The corneal dystrophy progressively worsened bilaterally, one year later. A penetrating keratoplasty was subsequently performed on the right eye at 31 years of age, and in the left eye a year later. The clinical and histopathologic findings of the corneal graft of the right eye were reported in the literature, with positivity to the Masson trichrome stain, negative staining with Congo red, and heterozygosity for the Arg124His mutation by serum DNA studies. Histopathologic studies of the corneal graft of the left eye were conducted at the University of Texas Southwestern Medical Center.

RESULTS

Histopathologic examination of the excised cornea showed the Masson trichrome positive deposits present from underneath the Bowman layer to the LASIK interface, with absence of deposits posterior to the latter. In contrast to the prior report describing findings in the corneal graft of the left eye, the deposits stained lightly with Congo red, but failed to show birefringence under polarized light, or fluorescence with thioflavin T.

CONCLUSION

Accelerated deposits developing after LASIK in ACD eyes seem to harbor pre-amyloid features. The epithelium is likely to be the culprit, in a pathway independent of with human transforming growth hormone beta (TGF-beta), with deposits developing in the anterior stroma and the stromal interface.

Deep Anterior Lamellar Keratoplasty in Korean Patients With Avellino Dystrophy

PURPOSE

To evaluate the surgical outcome of deep anterior lamellar keratoplasty (DALK) in Korean patients with Avellino dystrophy.

METHODS

A retrospective study was performed in 4 eyes (4 patients) with recurrent Avellino dystrophy after phototherapeutic keratectomy (PTK). Genetic study was performed on 2 patients to confirm the diagnosis. Partial-thickness donor cornea (devoid of endothelium and Descemet membrane) was transplanted onto a recipient bed after deep lamellar dissection and removal of recipient stroma. Visual acuity, refractive error, keratometry values, topographic astigmatism, and complications were evaluated after a follow-up period of at least 14 months.

RESULTS

The mean age of the patients was 52.5 +/- 3.32 years, and the mean follow-up period was 17.5 +/- 3.11 months. Visual acuity was improved to > or = 20/25 in all cases. Postoperative topographic astigmatism ranged from 1.2 to 4.9 D. In 1 case, double anterior chamber developed after the operation, which resolved after gas injection into the anterior chamber. During the follow-up period, there were no signs of graft rejection, and all grafts were transparent except one, in which small opacity recurred in the peripheral corneal stroma 13 months postoperatively.

CONCLUSIONS

DALK is considered a good primary surgical option in patients with recurrent Avellino dystrophy after PTK.

A clinical and histopathologic examination of accelerated TGFBIp deposition after LASIK in combined granular-lattice corneal dystrophy

PURPOSE

To report the clinical and histopathologic features of accelerated TGFBI protein (TGFBIp) deposition after lamellar keratorefractive surgery in a patient with combined granular-lattice corneal dystrophy (CGLCD) who underwent bilateral corneal transplantation.

DESIGN

Interventional case report.

METHODS

A 28-year-old woman with a presumed TGFBI corneal dystrophy, but who retained best corrected visual acuity of 20/20 in each eye, underwent myopic laser-assisted in-situ keratomileusis (LASIK) both eyes (OU). For definitive diagnosis of the corneal dystrophy, buccal epithelial cells were collected as a source of genomic DNA and screening of TGFBI exons 4 and 12 was performed.

RESULTS

Four months after the performance of an uncomplicated LASIK procedure, the patient's uncorrected visual acuity was 20/15 OU. Over the following two years, the appearance of confluent white stromal deposits at the LASIK flap interface resulted in disabling glare and a reduced best-corrected visual acuity of 20/40 OU. Corneal transplantation was performed in each eye, and histopathologic examination of the excised corneal buttons was performed. Eosinophilic material that stained positively with the Masson trichrome stain was present in the LASIK flap interface, as well as in the stroma of the flap and the anterior portion of the stromal bed. No amyloid deposits were identified with the Congo red stain. Screening of TGFBI exons 4 and 12 revealed the Arg124His mutation associated with CGLCD.

CONCLUSIONS

Accelerated deposition of TGFBIp may occur after lamellar corneal surgery in patients with CGLCD. Therefore, LASIK surgery should be avoided in patients with any of the TGFBI dystrophies, and surgeons should be aware of the potential for rapid interface TGFBIp deposition after lamellar corneal surgery.

Outcome of LASIK in fleck corneal dystrophy

PURPOSE

To report the outcome of laser in situ keratomileusis (LASIK) in a patient with Fleck corneal dystrophy.

METHODS

Case report and literature review.

RESULTS

A 48-year-old Taiwanese man presented in November 2005, 6 years after bilateral myopic LASIK. He complained of loss of uncorrected distance visual acuity that was worse in the left eye. The patient did not report glare, halos, or other visual aberrations. Preoperative best spectacle-corrected visual acuity (BSCVA) was 20/25 OU, with a manifest refraction of -14 D OU. In November 2005, uncorrected visual acuity (UCVA) was 20/40 OD and 20/50 OS, and BSCVA was 20/25 in each eye with a manifest refraction of -1.00 sphere OD and -1.75 -1.25 x 115 OS. Slit-lamp examination was remarkable for several subtle, small, gray corneal opacities present throughout the corneal stroma. Confocal microscopy revealed refractile bodies within swollen keratocytes and normal surrounding stromal mileu. The clinical and confocal appearance was consistent with Fleck corneal dystrophy.

CONCLUSION

In this patient with Fleck corneal dystrophy, corneal clarity and BSCVA were maintained 6 years after bilateral myopic LASIK, suggesting that LASIK does not stimulate visually significant exacerbation of Fleck corneal dystrophy.

Excimer laser exacerbation of Avellino corneal dystrophy

We review the clinical, histopathological, and ultrastructural findings and DNA phenotyping of a patient with Avellino corneal dystrophy exacerbated by laser in situ keratomileusis. The findings are reported and interpreted in the context of a literature review. The case highlights the possible difficulty of recognizing subtle dystrophic findings, as well as the importance of avoiding refractive surgical intervention in patients with Avellino corneal dystrophy to avoid exacerbation of dystrophic deposits in the cornea and subsequent reduction in vision.

Identification of an amyloidogenic region on keratoepithelin via synthetic peptides

Mutations of keratoepithelin (KE) gene in human chromosome 5q31 have been linked with corneal epithelial or stromal dystrophies characterized by the abnormal deposits of amyloid fibrils and/or non-amyloid aggregations in corneal tissue. We report herein that synthetic peptide containing amino acid (a.a.) residues of 515-532 of native KE protein can readily form beta-sheet-containing amyloid fibrils in vitro. Amyloid fibrils formed in various conditions from short synthetic peptides (containing a.a. 515-532 and 515-525, respectively) were characterized by thioflavin T (ThT) fluorescence assay, Congo red staining, electron microscopy (EM) and circular dichroism (CD). Triple-N-methylation of the synthetic peptides prevented the beta-sheet polymerization and related amyloid fibril formation. Comparison study with ThT fluorescence further demonstrated that synthetic peptides containing corneal dystrophy-related mutations within this region formed amyloid fibrils to various extents. Our results suggest that each individual dystrophy-related mutation by itself does not necessarily potentiate amyloid fibril formation of KE. Roles of these intrinsically amyloidogenic foci in abnormal KE aggregations and amyloid deposits of stromal corneal dystrophies await further investigation.