Effects of corneal neovascularization on the manifestations of Avellino corneal dystrophy (granular corneal dystrophy type II)

PURPOSE

To evaluate the corneal deposits of Avellino corneal dystrophy (ACD) in patients with corneal neovascularization from pterygium or phthisis bulbi as a way of understanding the pathogenesis of ACD.

METHODS

Five patients with ACD with pterygium, 10 patients with ACD (age >50 years) without pterygium, 1 patient with ACD with phthisis bulbi with corneal neovascularization, and 1 patient with ACD with phthisis bulbi without corneal neovascularization were examined. The corneal deposits of all patients were assessed by slit-lamp examination and reviewed with biomicroscopic photographs. The distance between the limbus and the nearest corneal opacities was measured.

RESULTS

In eyes with vascularized nasal pterygia, there was a granule-free zone adjacent to the advancing edge of the pterygium so that the distance between the nasal limbus and the most nasally located granule exceeds that of the distance between the limbus and the closest granule elsewhere on the cornea. In patients with ACD with phthisis bulbi, no granular deposits were observed in the cornea with neovascularization, but there were deposits in the cornea without neovascularization.

CONCLUSION

Corneal neovascularization prevents the deposition of corneal opacities in patients with ACD.

Light and inherited retinal degeneration

Light deprivation has long been considered a potential treatment for patients with inherited retinal degenerative diseases, but no therapeutic benefit has been demonstrated to date. In the few clinical studies that have addressed this issue, the underlying mutations were unknown. Our rapidly expanding knowledge of the genes and mechanisms involved in retinal degeneration have made it possible to reconsider the potential value of light restriction in specific genetic contexts. This review summarises the clinical evidence for a modifying role of light exposure in retinal degeneration and experimental evidence from animal models, focusing on retinitis pigmentosa with regional degeneration, Oguchi disease, and Stargardt macular dystrophy. These cases illustrate distinct pathophysiological roles for light, and suggest that light restriction may benefit carefully defined subsets of patients.

Exacerbation of Avellino corneal dystrophy after LASIK in North America

PURPOSE

To report the first case of Avellino corneal dystrophy exacerbation after LASIK in a white or North American patient.

METHODS

Case report and literature review.

RESULTS

A 25-year-old white female developed progressive corneal opacities after LASIK. Preoperative examination had revealed only subtle white corneal opacities in each eye. The patient's mother had similar corneal opacities. DNA analysis of the patient revealed a heterozygous mutation at the R124H location in the BIGH3 gene.

CONCLUSIONS

LASIK can exacerbate Avellino corneal dystrophy and should be avoided in patients with this condition. A careful history and genetic analysis can identify affected patients and those at risk.

Avellino corneal dystrophy exacerbated after LASIK: scanning electron microscopic findings

PURPOSE

To evaluate the ultrastructure of the cornea of Avellino corneal dystrophy (ACD) exacerbated by LASIK.

METHODS

Three ACD patients with exacerbation of granular corneal deposits after LASIK underwent surgical removal of the corneal flap. The corneal flap was processed for scanning electron microscopy (SEM).

RESULTS

SEM of all patients showed abnormal granular clusters in the fibrils of the corneal flap.

CONCLUSION

Laser in situ keratomileusis induces corneal collagen abnormalities and adhesions of granular material in ACD patients.

[Microkeratome-assisted lamellar keratoplasty for recurrent corneal granular dystrophy after phototherapeutic keratectomy]

OBJECTIVE

To evaluate the safety and efficacy of microkeratome-assisted lamellar keratoplasty (MLK) for the treatment of recurrent granular corneal dystrophy (GCD) after phototherapeutic keratectomy (PTK).

METHODS

We performed a prospective study of nine eyes (seven patients) with recurrent granular dystrophy after PTK. A microkeratome was used to cut partial-thickness sections through the anterior surface of the donor and host corneas. The donor disc was placed on the recipient bed with four or eight interrupted sutures. The stitches were removed between 4 and 6 weeks after surgery. Visual acuity (VA), corneal clarity, corneal thickness, and corneal topography were assessed before and at different time points after surgery.

RESULTS

During a mean follow-up period of (18.9 +/- 4.1) months, all grafts were transparent without visible opacity at the interface, and no serious complications occurred. The VA was improved in all cases. seven eyes had best corrected visual acuity with spectacles of 20/40 or better, two eyes reached 20/25. At the last follow-up visit more than 12 months postoperatively, the mean corneal refractive power increased significantly by (2.34 +/- 0.93) D (P < 0.01), and the corneal astigmatism significantly decreased by (0.91 +/- 0.98) D (P < 0.05). The mean corneal thickness was (477.4 +/- 26.9) microm preoperatively and (507.8 +/- 23.4) microm at the last follow-up visit (P < 0.01).

CONCLUSIONS

Our findings suggest that MLK for the treatment of recurrent GCD is a safe and easy-to-perform method for restoring VA.

Automated Lamellar Keratoplasty for Recurrent Granular Corneal Dystrophy After Phototherapeutic Keratectomy

PURPOSE

To evaluate the safety and efficacy of automated lamellar keratoplasty for the treatment of recurrent granular corneal dystrophy after phototherapeutic keratectomy (PTK).

METHODS

We performed a prospective interventional noncomparative case study of nine eyes (seven patients) with severe recurrent granular corneal dystrophy after PTK. An automated microkeratome was used to cut partial-thickness sections through the anterior surface of the donor and host corneas. The donor disc was placed on the recipient bed with four or eight interrupted sutures. The sutures were removed between 4 and 6 weeks postoperatively. Visual acuity, corneal clarity, corneal thickness, and corneal topography were assessed before and at different time points after surgery.

RESULTS

During a mean follow-up period of 18.9 +/- 4.1 months, all grafts were transparent without visible opacity at the interface, and no serious complications occurred. In all cases, the visual acuity improved: seven eyes had best spectacle-corrected visual acuity of > or = 20/40; two eyes reached 20/25. At last follow-up > 12 months postoperatively, the mean corneal refractive power had significantly increased by 2.34 +/- 0.93 diopters (D) (P<.001), and the corneal astigmatism significantly decreased by 0.91 +/- 0.98 D (P<.05). The mean corneal thickness was 477.4 +/- 26.9 microm preoperatively and 507.8 +/- 23.4 microm at last follow-up (P<.001).

CONCLUSIONS

Our findings suggest that automated lamellar keratoplasty for the treatment of recurrent granular corneal dystrophy is a safe and effective method of improving visual acuity, but recurrence remains a risk.

Recurrence of chromosome 10 Thiel-Behnke corneal dystrophy (CDB2) after excimer laser phototherapeutic keratectomy or penetrating keratoplasty

PURPOSE

To evaluate the recurrence of Thiel-Behnke dystrophy (linked to the 10 q23-q24 locus) after phototherapeutic keratectomy or penetrating keratoplasty.

METHODS

This is a retrospective study of 4 patients (8 eyes) who underwent phototherapeutic keratectomy and 1 patient (2 eyes) who underwent penetrating keratoplasty. Best corrected visual acuity was assessed, and biomicroscopic examinations for evidence of recurrent dystrophy were documented and photographed. The location, lesion distribution, and lesion pattern of any recurrence was noted.

RESULTS

Follow-up ranged from 8 months to 25 years (mean +/- SD 9.7 +/- 7.97 years). All 10 eyes showed biomicroscopic evidence of central recurrence. Six eyes showed an intermediate zone of honeycomb opacities as well as a peripheral zone of focal and geographic lesions. Despite the high incidence of recurrence, functional central visual acuity was maintained. All eyes maintained functional best corrected visual acuity (ranging from 20/25 to 20/80) despite the postoperative recurrence.

CONCLUSION

Recurrence of Thiel-Behnke corneal dystrophy is extremely high after either phototherapeutic keratectomy or penetrating keratoplasty. Despite the high incidence of recurrence, the central cornea is the last to be affected. The peripheral-to-central progression of the lesions points to an epithelial origin for the pathogenesis of the dystrophy. Phototherapeutic keratectomy in the treatment of Thiel-Behnke corneal dystrophy offers a safe and effective treatment modality, providing patients up to 8 years of improved vision ranging from 8 months to 8 years (mean +/- SD 3.7 +/- 2.7 years) and delaying or circumventing the need for more invasive intraocular surgical intervention.

Complications associated with anterior basement membrane dystrophy after laser in situ keratomileusis

PURPOSE

To evaluate the complications associated with anterior basement membrane dystrophy (ABMD) after laser in situ keratomileusis (LASIK).

SETTING

Cornea Service, Wills Eye Hospital, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.

METHODS

In this noncontrolled retrospective case series, the medical records of all patients with LASIK complications seen in the Cornea Service at Wills Eye Hospital from January 1, 1998, to December 31, 2002, were reviewed. All patients who presented with ABMD changes after LASIK were included in the study. Patients with a history of trauma before or after surgery were excluded.

RESULTS

Thirty-five eyes of 18 patients were included. The mean age was 46.2 years. Thirteen eyes (37.1%) had a flap-lift procedure to remove epithelial ingrowth or for an enhancement. The most common reason for the visit was visual complaints, which were seen in 77.8% of patients. Seven patients (38.9%) had visual complaints alone; 27.8% had visual complaints associated with recurrent erosions and 11.1%, with dry eyes. Four patients (22.2%) had recurrent corneal erosions with no visual complaints. On examination, the most common finding was negative staining with fluorescein dye within the LASIK flap, which was seen in all patients. In addition to the ABMD changes, 25.7% had some degree of epithelial ingrowth and 45.7%, irregular astigmatism.

CONCLUSIONS

Anterior basement membrane dystrophy changes post LASIK were associated with visual complaints and/or recurrent erosions. Patients should be carefully screened for ABMD. Those who have ABMD signs or symptoms may not be ideal candidates for LASIK.

Avellino corneal dystrophy after LASIK

OBJECTIVE

To report cases of Avellino corneal dystrophy (ACD) exacerbated by LASIK for myopia.

DESIGN

Retrospective, noncomparative, interventional case series and review of the literature.

PARTICIPANTS

Seven patients.

INTERVENTION

Six patients with exacerbation of granular corneal deposits after LASIK were examined for TGFBI mutations by polymerase chain reaction sequencing of DNA. One previously reported patient who was heterozygous for the ACD gene was followed up for 16 months after mechanical removal of granular deposits from the interface after LASIK.

MAIN OUTCOME MEASURES

Slit-lamp examination, visual acuity, manifest refraction, and DNA sequencing analysis.

RESULTS

All patients were heterozygous for the Avellino dystrophy gene. Corneal opacities appeared 12 months or more after LASIK. Best spectacle-corrected visual acuity decreased as the number and density of the opacities increased. One patient underwent mechanical removal of granules from the interface and had a severe recurrence within 16 months. Another patient had removal of the granules from the interface with PTK, followed by treatment with topical mitomycin C. In this patient, the cornea has remained relatively clear for 6 months.

CONCLUSIONS

Laser in situ keratomileusis increases the deposition of visually significant corneal opacities and is contraindicated in patients with ACD. Mechanical removal of the material from the interface does not prevent further visually significant deposits. Mitomycin C treatment, in conjunction with surgical removal of opacities, may be an effective treatment.

A model of FAS1 domain 4 of the corneal protein beta(ig)-h3 gives a clearer view on corneal dystrophies

PURPOSE

A progressive alteration of the cornea resulting in loss of transparency occurs in a set of hereditary diseases known as corneal dystrophies. A number of these dystrophies have been linked to mutations in the 5q31-linked gene product beta(ig)-h3 (TGFBIP, kerato-epithelin, MP78/70, RGD-CAP) although the mechanism by which the mutations cause disease remains unknown. Here we investigate the structural basis for the different corneal dystrophies caused by mutations of the beta(ig)-h3 protein. The integrin binding properties of beta(ig)-h3, described in several recent studies, have been analysed with respect to the beta(ig)-h3 structure.

METHODS

The recently determined structure of a FAS1 domain pair from fasciclin I, an insect cell adhesion molecule and beta(ig)-h3 homologue, was used to generate a homology model of the beta(ig)-h3 FAS1 domain 4.

RESULTS

The structural analysis of FAS1 domain 4 of beta(ig)-h3 predicts that the common mutations at positions 124 and 555 do not substantially alter the beta(ig)-h3 structure. In contrast, the rare missense mutations appear incompatible with the FAS1 fold. A number of residues implicated in integrin binding by previous mutagenesis are mostly buried and appear to have important structural roles.

CONCLUSIONS

The common mutations of beta(ig)-h3 at positions 124 and 555 are likely to affect protein-protein interactions directly, whereas the rare mutations are likely to cause misfolding of the protein within the cell. Previously identified integrin binding residues are unlikely to be directly involved in receptor binding.

Genetic linkage of Francois-Neetens fleck (mouchetée) corneal dystrophy to chromosome 2q35

Francois-Neetens fleck (mouchetée) corneal dystrophy is an autosomal dominant corneal dystrophy characterized by scattered small white flecks occurring at all levels of the corneal stroma. We report linkage of the CFD locus to D2S2289 (Z(max)=4.46, theta=0), D2S325 (Z(max)=3.28, theta=0), D2S317 (Z(max)=3.1, theta=0), D2S143 (Z(max)=3.8, theta=0.03), and D2S2382 (Z(max)=5.0, theta=0) on chromosome 2q35. Multipoint analysis confirmed linkage to the region between D2S117 and D2S126 with a maximum multipoint lod score of 5.0 located midway between D2S2289 and D2S325. Analysis of CFD in these same families assuming a 90% penetrance increased the maximum lod score to 6.28 at D2S157.

Recurrence of corneal stromal dystrophies after penetrating keratoplasty

PURPOSE

To assess the rates of simple and clinically significant recurrences of stromal dystrophies in corneal grafts.

METHODS

We conducted a retrospective review of Wills Eye Hospital records from 1984 to 2001, identifying all patients with stromal corneal dystrophies who had penetrating keratoplasties. Kaplan-Meier curves and chi analysis were performed.

RESULTS

The study population consisted of 35 eyes (21 patients) with lattice dystrophy, 17 eyes (10 patients) with corneal dystrophy of Bowman's membrane (CDB), 14 eyes (eight patients) with macular dystrophy, seven eyes (five patients) with granular dystrophy, and four eyes (four patients) diagnosed with Schnyder's crystalline dystrophy. There was a simple recurrence in 21 (60%) eyes (14 patients) with lattice and in 15 (88%) eyes (eight patients) with CDB. The median time to simple recurrence for the first eye transplanted of each patient was 8.4 years for lattice and 2.0 years for CDB. After 5 years of follow-up, there was a clinically significant recurrence, manifested by recurrent erosions or associated with decreased visual acuity, in the first eye transplanted of each patient, respectively, in six (17.1%) and seven (20%) eyes with lattice and in two (11.8%) and three (17.6%) eyes with CDB.

CONCLUSION

Corneal dystrophy of Bowman's membrane has the highest rate of simple recurrence followed by granular and lattice dystrophies, respectively. However, the rate of clinically significant recurrence, both recurrent erosions and decreased visual acuity, in the first 5 years is similar in CDB and lattice dystrophies. Recurrence is infrequent in macular and Schnyder's crystalline dystrophy. As expected, in genetic diseases, the potential for recurrence exists and increases with follow-up time.

Pre-Descemet's corneal dystrophy associated with ichthyosis

Pre-Descemet's dystrophy is a symmetrical bilateral comeal dystrophy consisting of multiple small discrete opacities of lipid-like material in the deep stroma just anterior to the pre-Descemet's membrane. We presented a case of a 46-year-old male who visited our hospital on account of acute conjunctivitis. On routine examination, we found multiple fine gray dots in the pre-Descemet's area and large, dark, scaly skin lesions over extensor surfaces of the extremities. After consultation with a dermatologist, X-linked recessive ichthyosis was diagnosed.

Phototherapeutic keratectomy for anterior basement membrane dystrophy after laser in situ keratomileusis

OBJECTIVE

To evaluate the efficacy and safety of phototherapeutic keratectomy (PTK) in the treatment of symptomatic anterior basement membrane dystrophy following laser in situ keratomileusis (LASIK).

METHODS

In a retrospective study, 10 eyes of 10 patients that developed symptomatic anterior basement membrane dystrophy following LASIK for myopia were treated with PTK using the VISX S2 (VISX Inc, Santa Clara, Calif) excimer laser. Primary outcome measurements including corneal clarity, resolution of symptoms, uncorrected visual acuity (UCVA), manifest refraction, best spectacle-corrected visual acuity (BSCVA), and complications were evaluated preoperatively, 1 day postoperatively, and at the last postoperative follow-up visit.

RESULTS

At the last follow-up visit (mean [SD], 8.8 [5.5] months; range, 4-22 months), 100% of the eyes had clear corneas with no evidence of anterior basement membrane dystrophy, and all eyes were asymptomatic. Mean spherical equivalent changed from -0.75 (0.99) diopters (D) (range, -2.75 to +0.25 D) preoperatively to -0.51 (0.80) D (range, -1.63 to +1.00 D) at the last follow-up visit (P =.64). Uncorrected visual acuity improved from 20/20 or better in 1 eye (10%) and 20/40 or better in 5 eyes (50%) preoperatively to 20/20 or better in 5 eyes (50%) and 20/40 or better in 7 eyes (70%) postoperatively. No eyes lost lines of BSCVA, 2 eyes gained 1 line, 2 eyes gained 2 lines, and 1 eye gained 4 lines. There was a statistically significant improvement in mean logMAR BSCVA postoperatively, improving from 0.06 (0.16) (range, -0.1 to +0.3) to -0.08 (0.07) (range, -0.1 to +0.1) (P =.04). Postoperative complications included diffuse lamellar keratitis that resolved after treatment without sequelae (20%) and induced myopia exceeding -1.50 D (10%).

CONCLUSION

Phototherapeutic keratectomy for the treatment of symptomatic anterior basement membrane dystrophy following LASIK treatment is safe and effective.

Exacerbation of Avellino corneal dystrophy after laser in situ keratomileusis

PURPOSE

To report a case of Avellino corneal dystrophy that increased in severity 1 year after uncomplicated laser in situ keratomileusis (LASIK) for myopia.

METHODS

Avellino dystrophy was confirmed by polymerase chain reaction sequencing of DNA from the patient and her parents.

RESULTS

Best spectacle-corrected visual acuity decreased from 20/20 to 20/30 12 to 20 months after LASIK owing to opacities that appeared centrally in the corneal stroma and the LASIK flap and remaining posterior stroma interface.

CONCLUSIONS

LASIK is contraindicated in patients with Avellino corneal dystrophy because vision may be reduced by corneal opacities that appear in the interface of the flap and remaining posterior stroma postoperatively.

Different recurrence patterns after phototherapeutic keratectomy in the corneal dystrophy resulting from homozygous and heterozygous R124H BIG-H3 mutation

PURPOSE

To report the recurrence pattern of corneal deposits after phototherapeutic keratectomy in patients with corneal dystrophies resulting from homozygous and heterozygous Arg124His (R124H) mutation of the BIG-H3 gene.

METHODS

Slit-lamp examination was performed on patients with corneal dystrophy resulting from a genetically confirmed BIG-H3 R124H mutation.

RESULTS

The recurrence of corneal deposits after phototherapeutic keratectomy in patient with heterozygous R124H mutation was mild; the granular opacities occurred as spot lesions in the central cornea. The patient with a homozygous mutation had a more severe pattern, and the recurrent lesions were diffuse and occurred in the periphery between the corneal epithelium and laser-ablated stroma. The recurrence-free interval in homozygous patients was shorter.

CONCLUSION

The mutation genotype of BIG-H3 gene determines the recurrence pattern after phototherapeutic keratectomy.

Corneal morphology and sensitivity in lattice dystrophy type II (familial amyloidosis, Finnish type)

PURPOSE

To describe the corneal abnormalities and to measure different modalities of corneal sensitivity in corneal lattice dystrophy type II (familial amyloidosis, Finnish type, also known as gelsolin-related amyloidosis and originally as Meretoja syndrome).

METHODS

Twenty eyes of 20 patients were examined by in vivo confocal microscopy and noncontact gas esthesiometry.

RESULTS

Pleomorphism of, and dense deposits between or posterior to, the basal epithelial cells were frequently observed, as well as a reduction of long nerve fiber bundles in the subbasal nerve plexus. The anterior stroma was altered in most cases, with fibrosis and abnormal extracellular matrix. In 15 corneas, thick anterior and midstromal filaments, corresponding to lattice lines, and in 11 corneas, thin undulated structures were observed. The average mechanical sensitivity threshold of 12 subjects was increased, and in the remaining 8 subjects there was no response, even to the highest intensity of stimuli used. Three patients did not respond to CO(2), 11 to heat, and 2 to cold, but those patients who responded had normal thresholds. Patients with more long nerve fiber bundles per confocal microscopic image had better mechanical and cold sensitivity than patients with fewer nerve fiber bundles.

CONCLUSIONS

Lattice lines seem to be related to amyloid material and not to corneal nerves. However, the subbasal nerve density appears reduced, which results mainly in a decrease in mechanical and, to a lesser extent, thermal sensitivity. The location of stromal filaments and undulated structures changes with increasing age.

Absence of ocular manifestations in autosomal dominant Alport syndrome associated with haematological abnormalties

Most patients with Alport syndrome have X-linked or autosomal recessive disease that is characterised by renal failure, hearing loss, and, in nearly 75% of the cases, a dot-and-fleck retinopathy and anterior lenticonus. There are only case reports of individuals with the rare autosomal dominant form, who can have haematuria or renal failure, deafness, and, in addition, low platelet counts and neutrophil inclusions. The ocular features of autosomal dominant inheritance have not been described. We have examined the eyes in the members of two families where Alport syndrome was diagnosed on the basis of the clinical features and family history, and where autosomal dominant inheritance was confirmed by father-to-son disease transmission, the associated haematological abnormalities, and haplotypes that segregated with the recently described locus at chromosome 22q. In Family A, the eyes of two individuals with haematuria, hearing loss, and haematological abnormalities and of nine unaffected family members were examined. In Family B, the eyes of two individuals with renal failure, normal hearing, and haematological abnormalities were examined. None of the affected or unaffected members in either family had a dot-and-fleck retinopathy, anterior lenticonus, a history suggesting recurrent corneal erosions, or corneal dystrophy. These results indicate that the protein abnormality in autosomal dominant Alport syndrome does not produce the retinopathy and lenticonus typical of X-linked and autosomal recessive disease. This may be because the abnormal protein is not present or is less important in the ocular basement membranes than elsewhere, or because the presence of a normal allele in autosomal dominant disease compensates for the defective allele.

In vitro creation of amyloid fibrils from native and Arg124Cys mutated betaIGH3((110-131)) peptides, and its relevance for lattice corneal amyloid dystrophy type I

BetaIGH3 protein has been recently involved in the pathogenesis of blinding corneal diseases, some of which have characteristic amyloid corneal deposits. The 124 codon of the betaig-h3 gene seems to be crucial for the amyloidogenicity of the protein product. We presently report an in vitro system that reproducibly forms amyloid fibrils from betaIGH3((110-131)) derived peptides. We also assessed the differences in fibril formation of two 22-amino acid peptides centered on the 124 residue: the native form and the Arg124Cys peptide (mutation linked to lattice corneal amyloid dystrophy type 1). After dialysis of Arg124Cys peptide against PBS 1/15 M pH 7.4 for 72 hours, Congo red staining and electron microscopy demonstrated the presence of abundant material fulfilling the criteria of amyloid. Quantitative analysis with thioflavine T fluorescence studies confirmed the high capacity of Arg124Cys peptide to form amyloid fibrils when compared to the native form.

Advances in the molecular genetics of corneal dystrophies

PURPOSE

To improve our understanding of the role of specific genes on corneal transparency through a review of linkage to specific chromosomal loci and the identification of the mutant genes dealing with the corneal dystrophies.

METHOD

Relevant recent literature on the corneal dystrophies is reviewed.

RESULTS

Molecular genetic studies of the corneal dystrophies suggest that genes on at least 10 human chromosomes are involved in the maintenance of corneal transparency (chromosomes 1, 5, 9, 10, 12, 16, 17, 20, 21, and X). Within the 10 chromosomes to which corneal dystrophies have been mapped, specific genetic mutations in seven genes (GSN, BIGH3, KRT3, See also pp. 687-691. KRT12, MSS1, GLA, and ARSC1) have been identified in 15 corneal dystrophies. Some corneal dystrophies that are considered distinct clinicopathologic entities are actually caused by different mutations in the same gene. For example, lattice dystrophy types I and IIIA, granular corneal dystrophy types I, II (Avellino dystrophy), and III (Reis-Bucklers dystrophy), and Thiel-Behnke corneal dystrophy are the result of mutations in BIGH3. Mutations in three genes (GSN, BIGH3, MSS1) are associated with amyloid deposition in the cornea. A gene for keratoconus has been mapped to chromosome 21, which is noteworthy because of the established association of keratoconus in Down syndrome (trisomy 21).

CONCLUSION

Recent genetic studies on the corneal dystrophies provide insight into some of these disorders at a basic molecular level. Some corneal dystrophies that were previously believed to be distinct clinicopathologic entities are closely related at the molecular level with the different phenotypes resulting from distinct mutations in the same gene. This new knowledge is leading to a revised classification of the corneal dystrophies and to the development of animal models of corneal dystrophies. The latter will lead to a better understanding of the pathogenesis of the disorders and hence to novel therapeutic approaches to those dystrophies that cause significant visual impairment. Research of this nature is only in its infancy.

On the role of kerato-epithelin in the pathogenesis of 5q31-linked corneal dystrophies

PURPOSE

Recently, the authors identified a gene, BIGH3, in which different mutations cause a group of hereditary corneal dystrophies: lattice type I and IIIA (CDLI and CDLIIIA), granular Groenouw type I (CDGGI), Avellino (CDA), and Reis-Bücklers' (CDRB). All these disorders are characterized by the progressive accumulation of corneal deposits with different structural organization. Experiments were conducted to determine the role of kerato-epithelin (KE), the product of BIGH3, in the pathogenesis of the diseases.

METHODS

KE-15 and KE-2, two rabbit antisera raised against peptides from the 69-364 and 426 - 682 amino acid regions of KE respectively, were used for immunohistology of the corneas obtained after keratoplasty in six CDLI patients, three CDGGI patients, and one CDA patient.

RESULTS

The nonamyloid deposits observed in CDGGI stained intensively with KE-15 and KE-2, whereas the amyloid deposits in all analyzed CDLI corneas reacted to KE-2 but not to KE-15. In the CDA cornea, where amyloid and nonamyloid inclusions were present, positive staining with both antisera was observed.

CONCLUSIONS

Pathologic amyloid and nonamyloid deposits observed in CDLI, CDGGI-, and CDA-affected corneas are caused by KE accumulation. Different staining patterns of amyloid and nonamyloid deposits observed with antibodies against the amino and carboxyl termini of KE suggest that two mechanisms of KE misfolding are implicated in the pathogenesis of 5q31-linked corneal dystrophies.

Recurrence of corneal dystrophy after excimer laser phototherapeutic keratectomy

BACKGROUND

Excimer laser phototherapeutic keratectomy (PTK) can be useful to treat anterior corneal dystrophies both before and after penetrating keratoplasty.

OBJECTIVE

To evaluate the recurrence of corneal dystrophies after excimer laser PTK.

DESIGN

Retrospective case series.

PARTICIPANTS

Fifty excimer laser PTK procedures were performed in 43 eyes of 33 patients with corneal dystrophies. Preoperative diagnoses included Reis-Bücklers dystrophy (13 eyes), granular dystrophy (11 eyes), anterior basement membrane (ABM) dystrophy (11 eyes), lattice dystrophy (7 eyes), and Schnyder crystalline dystrophy (1 eye).

INTERVENTION

Two excimer lasers (VISX 20/20 model B and VISX Star) were used to perform all PTKs.

MAIN OUTCOME MEASURES

After PTK, patients were followed on a regular basis with measurement of best-corrected visual acuity and biomicroscopic examination. Evidence of recurrent dystrophy was noted according to specific criteria.

RESULTS

Follow-up range was from 1.1 to 71.2 months (mean, 19.5 months). Clinically significant recurrent dystrophy occurred in 17 eyes. The ABM dystrophy recurred in the form of recurrent corneal erosions in 5 (42%) of the 12 eyes within 6 to 9 months of PTK. Four of these five eyes had mild erosions, which were treated successfully with topical medications while one eye required an additional PTK for an erosion outside the initial treatment area. Eight (47%) of 17 eyes with Reis-Bücklers dystrophy developed clinically significant recurrence an average of 21.6 months after PTK. Three (23%) of 13 eyes with granular dystrophy were found to have a significant recurrence a mean of 40.3 months after PTK. Only one (14%) of seven eyes with lattice dystrophy developed a significant recurrence at 6 months after PTK. Six eyes with significant recurrence after PTK were retreated successfully with additional PTK. Three eyes later developed recurrence of granular and Reis-Bücklers dystrophy after the second PTK. The probability of recurrence of these dystrophies after PTK was calculated using the Kaplan-Meier survival analysis.

CONCLUSION

Phototherapeutic keratectomy can restore and preserve useful visual function for a significant period of time in patients with anterior corneal dystrophies. Even though corneal dystrophies are likely to recur eventually after PTK, successful retreatment with PTK is possible.

Recurrent macular corneal dystrophy type II 49 years after penetrating keratoplasty

Recurrence of macular corneal dystrophy after keratoplasty is rare. We report light microscopic, immunohistochemical, electron microscopic, and serologic findings in a 78-year-old woman who underwent regrafting 49 years following the first penetrating keratoplasty. Examination of the corneal button revealed deposits of glycosaminoglycans in the graft beneath the Bowman layer, throughout the stroma, and in the endothelium with positive staining for antigenic keratan sulfate. By transmission electron microscopy, intracellular and extracellular deposits of a fibrillogranular material were detected in the stroma, Descemet membrane, and endothelium. The serum level of antigenic keratan sulfate was normal. Our findings indicate that macular corneal dystrophy type II may show late recurrence after penetrating keratoplasty with intense deposition of antigenic keratan sulfate in all corneal layers.