Clinical Profile and Demographic Distribution of Corneal Dystrophies in India: A Study of 4198 Patients

PURPOSE

To describe the clinical profile and demographic distribution of corneal dystrophy in patients presenting to a multitier ophthalmology hospital network in India.

METHODS

This cross-sectional hospital-based study included 2,151,584 new patients presenting between March 2012 and December 2019 (∼8 year period). Patients with a clinical diagnosis of corneal dystrophy in at least 1 eye were included as cases. The data were collected by using an electronic medical record system.

RESULTS

Overall, 4198 new patients (0.20%) were diagnosed with corneal dystrophy. The prevalence rates were 0.19% in children (age < 16 years) and 0.20% in adults. Most patients were women (51.86%). The mean age of the patients was 43.61 ± 21.39 years. Most patients (18.79%) were between 61 and 70 years of age. The most common anatomical location of the dystrophy was endothelium (51.71%), followed by stroma (43.55%) and Bowman membrane/epithelium (4.73%). The most common corneal dystrophy was Fuch endothelial corneal dystrophy (41.89%). Most eyes had mild or no visual impairment (43.43%). Of the 8193 eyes, 998 eyes (12.18%) underwent a corneal surgery. Among those who underwent surgical intervention, endothelial keratoplasty was the most commonly performed surgical procedure (52%), followed by penetrating keratoplasty (22%).

CONCLUSIONS

Corneal dystrophy is a rare disease, affecting patients seeking eye care in India. Endothelial dystrophies were the most common, followed by stromal dystrophies. Among the stromal dystrophies, macular dystrophy was the most common. At initial presentation, visual impairment was mild to moderate in most patients, and surgical intervention was needed in 12.18% of the eyes during the study period.

Diagnostic Criteria for Terrien Marginal Degeneration: Nordic Terrien Degeneration Study

PURPOSE

To refine the diagnostic criteria for Terrien marginal degeneration (TMD) based on experience in 3 Nordic countries.

METHODS

This is a retrospective, multicenter, hospital-based cross-sectional study of 49 eyes of 29 white patients in tertiary referral centers in Finland, Sweden, and Denmark from 1998 to January 2018. The median follow-up was 3 years. Symptoms, best corrected visual acuity, astigmatism, corneal thickness, curvature and cavities, stage, and progression were analyzed.

RESULTS

TMD was diagnosed equally likely between 15 and 86 years of age (median, 47 years). Twenty patients (69%) had bilateral disease, and 62% were men. Seventeen patients (59%) had symptoms including blurred vision and ocular surface disease symptoms without inflammatory signs. Eight patients (28%) had slightly reduced corneal sensitivity. Median best corrected visual acuity was 20/25 (range, 20/16-20/200) and astigmatism was 2.6 diopters (D) (range, 0-10) with a mean progression of 0.41 D per year (range, 0-5.4). Age and astigmatism were not correlated. All eyes had peripheral vascularization, lipid deposits, and hyperreflectivity throughout thinned peripheral stroma and its anterior edge. The thinning progressed in 15 patients (52%). Of 26 patients, 8 (31%) had single or confluent paralimbal intrastromal cavities, most commonly superiorly. By Süveges classification, the stage was 2 (92%) or 3 (8%). Minimum corneal thickness and corneal curvature were loosely associated, leading to different stages in Wang classification in 34 eyes (69%).

CONCLUSIONS

TMD is defined by peripheral corneal thinning, superficial neovascularization, lipid deposition at the leading edge, absence of ulceration and inflammation, and frequently cavitation. The most sensitive way to follow its progression is anterior segment optical coherence tomography.

DIFFUSE CHORIORETINAL ATROPHY IN CHINESE HIGH MYOPIA: The ZOC-BHVI High Myopia Cohort Study

PURPOSE

To explore the associations between diffuse chorioretinal atrophy (DCA) and age, sex, axial length, spherical equivalent, and best-corrected visual acuity (BCVA) among highly myopic eyes.

METHODS

This study included right eyes of 857 bilaterally highly myopic individuals from the ZOC-BHVI Cohort Study. Participants underwent examinations, including BCVA, ocular biometry, autorefraction, and color fundus photography. An Early Treatment Diabetic Retinopathy Study grid was applied on the fundus photographs to evaluate the location of DCA, which was graded into four categories (D0-D3). The characteristics and ocular biometry were compared between participants' eyes with and without DCA.

RESULTS

Diffuse chorioretinal atrophy was found in 177 (20.6%) eyes. The proportion of participants with DCA in age groups of 7 to 11, 12 to 18, 19 to 39, and ≥ 40 years old was 20.9%, 9.2%, 23.1%, and 52.9%, respectively. The proportion of DCA significantly increased with longer axial length and worse myopic spherical equivalent. Eyes with DCA had poorer BCVA (Snellen visual acuity 20/36, logarithm of minimal angle of resolution 0.26 ± 0.25) than those without DCA (Snellen visual acuity 20/23, logarithm of minimal angle of resolution 0.06 ± 0.14) (P < 0.001). The BCVA gradually declined as the lesion got closer to the fovea (P for trend < 0.001).

CONCLUSION

The proportion of DCA increased with older age, longer axial length, and more myopic spherical equivalent. Diffuse chorioretinal atrophy is a vision-threatening complication of high myopia where BCVA gradually worsens with foveal involvement.

Prevalence of stromal corneal dystrophies in Lahore

To determine the prevalence of Stromal Corneal Dystrophies (SCDs) in patient from Lahore hospitals. The study was performed between November, 2014 to July 2015 at the Layton Rahmatullah Benevolent Trust Hospital, Mughal Hospital, Mayo Hospital and General Hospital, Lahore. For the clinical evaluation of SCD by ophthalmologists examination of cornea was done by biomicroscopy, specular microscopy, topography, keratometry, orbscan and far visual acuity. Fifty cases of SCDs were recognized from Lahore, matching to hospital prevalence of 0.4%. The variables examined were age, gender, main complaint, corneal thickness, intraocular pressure and far visual acuity. SCDs are predominant in age group of 40-50 years. SCDs are more in male (n=30) as compared to females (n=20). Careful clinical evaluation, genotyping, governmental approval and subsequent development of human clinical trials of possible therapies and treatments should be taken to continue making improvement and effective control of SCDs.

TGFBI, CHST6, and GSN gene analysis in Mexican patients with stromal corneal dystrophies

OBJECTIVES

The purpose of our study was to describe the results of molecular screening of TGFBI, CHST6, and GSN genes in a group of Mexican patients with different stromal corneal dystrophies (CD).

MATERIAL AND METHODS

A total of 16 CD Mexican patients pertaining to nine different pedigrees were subjected to a complete ophthalmological investigation. A clinical diagnosis of lattice CD was performed in 10 patients from five pedigrees. Three patients from two pedigrees were diagnosed with granular CD type 2, two patients with unrelated probands had Finnish-type corneal amyloidosis, and one patient had macular CD. Genetic analysis included DNA isolation from blood leukocytes and polymerase chain reaction (PCR) amplification and direct nucleotide sequencing of TGFBI, CHST6, and GSN genes.

RESULTS

Seven lattice CD patients from four unrelated families had an identical p.H626R mutation in TGFBI, three patients from a single lattice CD family carried a p.R124C substitution in TGFBI, and a granular type 2 CD pedigree was demonstrated to carry a heterozygous TGFBI p.M619K substitution. A patient having Finnish-type corneal amyloidosis had a p.D187N mutation in GSN. Finally, molecular analysis of CHST6 in a patient with macular CD disclosed the presence of a homozygous p.Y110C change.

CONCLUSIONS

This study improves the knowledge of the genetic features of Mexican patients with corneal stromal dystrophies by identifying mutations in the TGFBI, CHST6, and GSN genes. Genetic screening of larger samples of patients from distinct ethnic groups would be of great importance for a better understanding of the mutational spectrum of stromal CD.

Clinical and basic aspects of gelatinous drop-like corneal dystrophy

Gelatinous drop-like corneal dystrophy (GDLD) was first reported in 1914 as a peculiar corneal dystrophy with an autosomal recessive inheritance mode. GDLD is rare in many countries, but relatively prevalent in Japan. The typical finding of GDLD is grayish, mulberry-like, protruding subepithelial depositions with a prominent hyperfluorescence of the cornea. Histologically, GDLD corneas are characterized by subepithelial amyloid depositions that were identified as lactoferrin by amino acid sequencing analysis. In 1998, the TACSTD2 gene was identified as a causative gene for this disease through a linkage analysis and a candidate gene approach. To date, 14 reports have demonstrated 21 mutations comprised of 9 missense, 6 nonsense, and 6 frameshift mutations from 9 ethnic back grounds. Currently, it is hypothesized that the loss of TACSTD2 gene function causes decreased epithelial barrier function, thereby facilitating tear fluid permeation into corneal tissue, the permeated lactoferrin then transforming into amyloid depositions via an unknown mechanism. For the visual rehabilitation of patients with GDLD, ophthalmologists currently employ various types of keratoplasties; however, almost all patients will experience a recurrence of the disease within a few years after such interventions. Wearing of a soft contact lens is sometimes considered as an alternative treatment for GDLD.

Spheroid degeneration of cornea and conjunctiva. Prevalence among Eskimos in Greenland and Caucasians in Copenhagen

The incidence of spheroid degeneration has been studied in a series of 659 Eskimos from Arctic South-West Greenland and one of 810 Caucasians in Copenhagen with its temperate climate. The over-all prevalence was highest among the Eskimos (12.3% against 4.1% among the Copenhageners, P less than 0.001). The prevalence was found to be independent of sex, but to rise with increasing age (however, with a fall again after the age of 70 years in Copenhagen). The spheroid deposits were present on the conjunctiva in 74%, on the cornea in 18%, and at both sites in 8%. 71% of the subjects displayed autofluorescent globular deposits. These constituted 10% of the total number of globules. The number of globules per subject averaged 30. Spheroid degeneration was rarely found temporally in Eskimos. Spheroid degenerative processes are most frequently seen in pingueculae, but are not considered bear any relation to pterygium.

Replication and refinement of linkage of posterior polymorphous corneal dystrophy to the posterior polymorphous corneal dystrophy 1 locus on chromosome 20

PURPOSE

The study purpose was to identify the genetic basis of posterior polymorphous corneal dystrophy, an autosomal dominant disorder of the corneal endothelium that is associated with the development of corneal edema, necessitating corneal transplantation for visual rehabilitation. Glaucoma also develops in up to 40% of patients with posterior polymorphous corneal dystrophy.

METHODS

Linkage analysis, using microsatellite markers previously used to demonstrate linkage of posterior polymorphous corneal dystrophy to the chromosome 20 candidate region known as posterior polymorphous corneal dystrophy 1, was performed in 29 members of a family with posterior polymorphous corneal dystrophy. Thirty-four microsatellite markers were used to refine the posterior polymorphous corneal dystrophy 1 interval. TCF8, located on chromosome 10, was screened in an affected family member to exclude posterior polymorphous corneal dystrophy 3.

RESULTS

Significant evidence of linkage to the posterior polymorphous corneal dystrophy 1 interval was obtained with both single-point and multipoint analyses. The largest single-point log odds ratio score obtained was 4.38 (theta=0) at marker D20S471; within 4.7 Mbp (7.2 cM) of D20S471 eight markers provided single-point log odds ratio scores of greater than 3.00 and three markers provided single-point log odds ratio scores greater than 4.00. The largest multipoint log odds ratio score obtained was 4.83, found across the adjacent markers D20S844, D20S191, D20S484, and D20S111. The support interval for posterior polymorphous corneal dystrophy 1 in the family we report is approximately 13.5 Mbp (10 cM) long and lies between the markers D20S182 and D20S195. Eleven markers have multipoint log odds ratio scores greater than 4.0 within this region. No coding region mutations were identified in TCF8 in an affected member of the family, effectively excluding posterior polymorphous corneal dystrophy 3.

CONCLUSIONS

The originally described 19.8 cM posterior polymorphous corneal dystrophy 1 candidate disease interval has been refined to a 10 cM interval between markers D20S182 and D20S195. A portion of this refined interval overlaps a more recently reported posterior polymorphous corneal dystrophy 1 interval, with only 20 known and predicted genes mapped to the 2.4 cM common interval.

Visual morbidity in thirty-four families with Schnyder crystalline corneal dystrophy (an American Ophthalmological Society thesis)

PURPOSE

To assess the findings, visual morbidity, and surgical intervention in Schnyder crystalline corneal dystrophy (SCCD).

METHODS

Retrospective case series of 115 affected individuals from 34 SCCD families identified since 1989. Age, uncorrected visual acuity, best-corrected visual acuity (BCVA), corneal findings, and ocular surgery were recorded. Prospective phone, e-mail, or written contact provided updated information. Patients were divided into 3 age categories for statistical analysis: less than 26 years of age, 26 to 39 years of age, and 40 years of age and older.

RESULTS

Mean age on initial examination was 38.8 +/- 20.4 (range, 2-81) with follow-up of 55 of 79 (70%) of American patients. While there were no statistical significant correlations between logMAR visual acuity and age (logMAR BCVA =.033 + .002 x age; R =.21), the linear regression showed the trend of worse visual acuity with age. BCVA at > or =40 years was decreased compared to <40 (P < .0001), although mean BCVA was > 20/30 in both groups. Twenty-nine of 115 patients had corneal surgery with 5 phototherapeutic keratectomy (3 patients), and 39 penetrating keratoplasty (PKP) (27 patients). PKP was reported in 20 of 37 (54%) patients > or =50 years and 10 of 13 (77%) of patients > or =70. BCVA 1 year prior to PKP in 15 eyes (9 patients) ranged from 20/25 to 20/400 including 7 eyes with other ocular pathology. BCVA in the remaining 8 eyes was 20/25 to 20/70 with 3 of these 4 patients reporting preoperative glare. Chart and phone survey suggested increasing difficulty with photopic vision with aging.

CONCLUSION

Although excellent scotopic vision continues until middle age in SCCD, most patients had PKP by the 7th decade. SCCD causes progressive corneal opacification, which may result in glare and disproportionate loss of photopic vision.

A novel H572R mutation in the transforming growth factor-beta-induced gene in a Thai family with lattice corneal dystrophy type I

PURPOSE

To describe a large Thai family with lattice corneal dystrophy (LCD) type I and to determine whether this LCD is associated with mutations within the transforming growth factor-beta-induced (TGFBI) gene.

METHODS

A six-generation family with LCD type I was identified and diagnosed on the basis of clinical and/or histopathologic evaluation. Visual acuity testing and slit-lamp biomicroscopic evaluation were carried out and corneal photography was documented. All 17 exons and flanking intron sequences of the TGFBI gene were sequenced.

RESULTS

Thirty-three participants demonstrated LCD in both eyes, most of which was symmetrical. Age at onset of decreased vision was the mid- to late twenties. Visual acuity varied from 6/6 to no light perception. Two patients, 74 and 42 years of age, demonstrated a thick yellowish plaque covering the corneal surfaces. DNA sequencing revealed a heterozygous mutation in exon 13 (A1762G), changing histidine to arginine at codon 572 (H572R). Ten of 42 clinically unaffected family members, all under 25 years of age, exhibited the same mutation.

CONCLUSIONS

This is the first report of a molecular analysis of LCD type I in Thai patients. The novel mutation identified is associated with distinct phenotypes and later onset of the disease compared with the more common R124C mutation.

Recessive cornea plana in the Kingdom of Saudi Arabia

OBJECTIVE

To characterize the molecular genetics of clinically diagnosed recessive cornea plana in the Kingdom of Saudi Arabia and establish the presence of common or limited founders (ancestors who originally harbored the disease-causing mutation) in the country's historically isolated population.

DESIGN

Prospective interventional case series.

PARTICIPANTS

Twelve affected patients from apparently unrelated Saudi Arabian nuclear families with clinically diagnosed recessive cornea plana.

METHODS

Clinical ophthalmic examination and venous blood sampling for DNA sequencing.

MAIN OUTCOME MEASURES

Age, gender, keratometry, best-corrected visual acuity, ocular alignment, cycloplegic refraction, significant findings of a complete ophthalmic examination, and keratocan gene (KERA) haplotype analysis.

RESULTS

All 12 individuals had classic phenotypic features of recessive cornea plana and were homozygous for 1 of 2 KERA mutations--a novel frameshift mutation (1634delC) or a previously reported nonsense mutation (R313X). Haplotype analysis was consistent with a separate distinct common founder effect for each instance. An additional Saudi KERA mutation (R279X) has been reported previously in one family.

CONCLUSION

Specific for mutation in KERA, the ophthalmic phenotype of recessive cornea plana does not significantly vary with different KERA mutations. The occurrence of a rare inherited disease in a historically isolated population is not always due to a single common founder effect; it may be explained by cultural preferences such as consanguinity (intrafamilial marriage) and endogamy (intratribal marriage), which enhance expression of recessively inherited diseases.

Posterior polymorphous corneal dystrophy in Czech families maps to chromosome 20 and excludes the VSX1 gene

PURPOSE

Posterior polymorphous corneal dystrophy (PPCD) is an autosomal dominant disorder, affecting both the corneal endothelium and Descemet's membrane. In the Czech Republic, PPCD is one of the most prevalent corneal dystrophies. The purpose of this study was to determine the chromosomal locus of PPCD in two large Czech families, by using linkage analysis.

METHODS

Linkage analysis was performed on 52 members of two Czech families with PPCD and polymorphic microsatellite markers and lod scores were calculated. The candidate gene VSX1 was also screened for mutations.

RESULTS

Significant lod scores were obtained with microsatellite markers on chromosome 20. Linkage analysis delineated the Czech PPCD locus to a 2.7-cM locus on chromosome 20, region p11.2, between flanking markers D20S48 and D20S139, which excluded VSX1 as the disease-causing gene in both families. In addition, the exclusion of VSX1 was confirmed by sequence analysis.

CONCLUSIONS

This study reports the localization of PPCD in patients of Czech origin to chromosome 20 at p11.2. Linkage data and sequence analysis exclude VSX1 as causative of PPCD in two Czech families. This refined locus for PPCD overlaps the congenital hereditary endothelial dystrophy (CHED1) disease interval, and it is possible that these corneal dystrophies are allelic.

Frequency, distribution, and outcome of keratoplasty for corneal dystrophies at a tertiary eye care center in South India

PURPOSE

To report the frequency, outcome, and atypical histology in corneal dystrophies.

METHODS

Corneal buttons of patients diagnosed with corneal dystrophy as noted in the records of the ophthalmic pathology register over a period of 6 years were included in this study. The sections from formalin-fixed, paraffin-embedded tissues were reviewed specifically for the type of deposits, associated degenerations such as amyloid and spheroidal deposits, inflammation, and vascularization. Special stains including Masson trichrome, Congo red, and Alcian blue staining were used whenever required. The medical records were evaluated for demographics, clinical presentation, history of consanguinity, family medical history, and clinical outcome of keratoplasty, which was recorded as clear, recurrence of dystrophy, or graft failure. A clinicopathologic correlation was attempted.

RESULTS

A total of 144 patients contributed 181 buttons, accounting for 8.1% of keratoplasties performed during the study period. The mean age of the patients was 34 +/- 19 years (range 3-72 years) with a male:female ratio of 1.6 (89):1 (55). Consanguineous parentage was noted in 26% of cases. History of a similar problem in siblings and other family members was elicited in 33 (22%) and 14 (9.7%), respectively. Dystrophies included macular (29.3%), congenital hereditary endothelial dystrophy (34.8%), Fuchs (16.6%), and lattice (15%); the remaining 11% included granular, gelatinous drop-like, Reis-Bucklers, and posterior polymorphous dystrophy. Associated histologic changes were degenerations (15%), vascularization (4%), and inflammation (2%). At a mean follow-up of 42 months, the graft remained clear in 148 eyes (81.7%), failed in 33 eyes (18.2%), and recurred in 5 eyes (2.8%). Graft survival for all dystrophies at the end of 1 year was 94.3 +/- 1.7%, and at the end of 5 years was 74.4 +/- 4.5%. Atypical histologic features did not affect graft survival.

CONCLUSION

Consanguineous marriages possibly contributed to the increase in macular dystrophy and CHED in South India. The degenerative changes seen could possibly be related to late presentation or unknown environmental factors and do not have an effect on the ultimate graft outcome.

BIETTI’S CRYSTALLINE CORNEORETINAL DYSTROPHY: A CROSS-SECTIONAL STUDY

OBJECTIVE

To evaluate the prevalence of Bietti's corneoretinal dystrophy (BCD) in a reference population of retinitis pigmentosa (RP), and to document the disease course clinically and angiographically by a cross-sectional approach.

METHODS

Two hundred seven consecutive RP patients were ascertained within a 3-year period. All patients had a complete eye examination, including fluorescein and indocyanine green angiography (FA, ICG). Blood samples were collected for electron microscopy evaluation of circulating lymphocytes of BCD patients.

RESULTS

Six patients were diagnosed with BCD. Prevalence was 3% of nonsyndromic RP cases. Limbal corneal and intraretinal crystals were found in all cases. In the early phase of BCD, ICG revealed focal lobular areas of choriocapillary atrophy at the equator, with concomitant retinal pigment epithelium (RPE) changes at the posterior pole on FA. These lesions gradually progressed both anteriorly and posteriorly, sparing an incomplete peripapillary ring and macular island until late in the disease. Progressive sclerosis of ciliary and choroidal arteries was noted upon ICG. The presence of lysosomal crystals was documented in a subpopulation of circulating lymphocytes that seemed to increase with age.

CONCLUSION

The present study is the first to assess BCD prevalence in a population of retinitis pigmentosa patients, to describe clinically and angiographically its evolution from first symptom to legal blindness, and to localize the first fundus alterations not only at the posterior pole but also at the equator.

Novel mutations of the carbohydrate sulfotransferase-6 (CHST6) gene causing macular corneal dystrophy in India

PURPOSE

Macular corneal dystrophy (MCD) is an autosomal recessive disorder characterized by progressive central haze, confluent punctate opacities and abnormal deposits in the cornea. It is caused by mutations in the carbohydrate sulfotransferase-6 (CHST6) gene, encoding corneal N-acetyl glucosamine-6-O-sulfotransferase (C-GlcNAc-6-ST). We screened the CHST6 gene for mutations in Indian families with MCD, in order to determine the range of pathogenic mutations.

METHODS

Genomic DNA was isolated from peripheral blood leukocytes of patients with MCD and normal controls. The coding regions of the CHST6 gene were amplified using three pairs of primers and amplified products were directly sequenced.

RESULTS

We identified 22 (5 nonsense, 5 frameshift, 2 insertion, and 10 missense) mutations in 36 patients from 31 families with MCD, supporting the conclusion that loss of function of this gene is responsible for this corneal disease. Seventeen of these mutations are novel.

CONCLUSIONS

These data highlight the allelic heterogeneity of macular corneal dystrophy in Indian patients.

[Geographical feature of lattice corneal dystrophy patients in Aichi Prefecture: an analysis of the TGFBI gene]

PURPOSE

To investigate the genetics of patients with lattice corneal dystrophy (LCD) in Aichi Prefecture, the majority of whom originated from the same area of Hazu-gun.

METHODS

We studied twenty patients who visited Nagoya University Hospital from April 1997 to March 2000 and were diagnosed as having LCD. A complete history including a detailed family history was obtained from each of the patients. DNA analysis was performed on each patient with an informed consent.

RESULTS

Fourteen patients had an obvious family history, and 7 pedigrees were detected. Four of the 7 families were from Hazu-gun, and Arg 124 Cys mutation in the TGF-beta indused gene human 3(TGFBI) gene was detected in the families. A family from Nishikasugai-gun had a Leu 518 Pro mutation in the same gene. Six patients were considered sporadic without any family history. However, a heterozygous single base-pair transition (leucine to arginine) was detected in codon 527 of the TGFBI gene in 4 out of these 6 patients.

CONCLUSION

Genetic analysis confirmed that LCD observed in patients from Hazu-gun is a type I LCD caused by an Arg 124 Cys mutation in the TGFBI gene. TGFBI gene mutations, other than the Arg 124 Cys, were detected in a family with LCD type I in Aichi Prefecture. Among the autosomal dominant inherited LCDs, there is at times a sporadic pattern because of its late-onset form.

Mutations in corneal carbohydrate sulfotransferase 6 gene (CHST6) cause macular corneal dystrophy in Iceland

PURPOSE

Macular corneal dystrophy (MCD) is subdivided into three immunophenotypes (MCD types I, IA and II). Recently, mutations in the carbohydrate sulfotransferase 6 gene (CHST6) were identified to cause MCD. The purpose of this study was to examine CHST6 for mutations in Icelandic patients with MCD type I.

METHODS

Genomic DNA was extracted from leukocytes in the peripheral blood and the coding region of CHST6 was examined for mutations by polymerase chain reaction (PCR) and direct sequencing.

RESULTS

Mutation analysis of the CHST6 coding region identified three different mutations in sixteen Icelandic patients with MCD type I. Eleven patients with MCD type I were homozygous for a C1075T mutation. One patient with MCD type I was found to be a compound heterozygous for C1075T and G1189C mutations. One family with MCD type I contained a 10 base pair insertion (ATGCTGTGCG) between nucleotides 707 and 708. In this family, two affected siblings had a homozygous insertion while both their affected mother and their affected maternal aunt had a heterozygous insertion and a heterozygous C1075T mutation.

CONCLUSIONS

Three different nucleotide changes were identified in the coding region of CHST6 in sixteen Icelandic patients with MCD type I. All three of these alterations are predicted to affect the translated protein and each of them corresponded to a particular disease haplotype that we had previously reported in this population.

Association of autosomal dominantly inherited corneal dystrophies with BIGH3 gene mutations in Japan

PURPOSE

To evaluate the incidence of BIGH3 gene mutations in 164 unrelated Japanese patients with corneal stromal dystrophies with an autosomal dominant trait.

METHODS

Data were collected at two major institutions in the eastern and western parts of Japan, where molecular genetic analysis was performed for diagnostic purpose.

RESULTS

The incidence of mutations was ranked as follows: 118 patients (72%), the R124H mutation associated with Avellino corneal dystrophy; 23 patients (14%), the R124C mutation associated with lattice corneal dystrophy type 1; and 10 patients (6%), the P501T mutation associated with lattice corneal dystrophy type 3A.

CONCLUSION

Avellino corneal dystrophy associated with the R124H mutation is the most common form of corneal stromal dystrophy in Japan. This dystrophy, which is diagnosed histopathologically, has also been called granular corneal dystrophy in Japan. The classification of these diseases according to genetic pathogenesis may be more appropriate than is the use of clinical or histological findings.

The 2588G-->C mutation in the ABCR gene is a mild frequent founder mutation in the Western European population and allows the classification of ABCR mutations in patients with Stargardt disease

In 40 western European patients with Stargardt disease (STGD), we found 19 novel mutations in the retina-specific ATP-binding cassette transporter (ABCR) gene, illustrating STGD's high allelic heterogeneity. One mutation, 2588G-->C, identified in 15 (37.5%) patients, shows linkage disequilibrium with a rare polymorphism (2828G-->A) in exon 19, suggesting a founder effect. The guanine at position 2588 is part of the 3' splice site of exon 17. Analysis of the lymphoblastoid cell mRNA of two STGD patients with the 2588G-->C mutation shows that the resulting mutant ABCR proteins either lack Gly863 or contain the missense mutation Gly863Ala. We hypothesize that the 2588G-->C alteration is a mild mutation that causes STGD only in combination with a severe ABCR mutation. This is supported in that the accompanying ABCR mutations in at least five of eight STGD patients are null (severe) and that a combination of two mild mutations has not been observed among 68 STGD patients. The 2588G-->C mutation is present in 1 of every 35 western Europeans, a rate higher than that of the most frequent severe autosomal recessive mutation, the cystic fibrosis conductance regulator gene mutation DeltaPhe508. Given an STGD incidence of 1/10,000, homozygosity for the 2588G-->C mutation or compound heterozygosity for this and other mild ABCR mutations probably does not result in an STGD phenotype.

[Honeycomb-shaped corneal dystrophy of Thiel and Behnke. Reclassification and distinction from reis-Bücklers' corneal dystrophy]

BACKGROUND

The honeycomb-shaped dystrophy of Thiel and Behnke has been misunderstood for a long time and has erroneously been classified as Reis-Bücklers' dystrophy. The mistake originates in historical misunderstandings concerning the interpretation of the original Reis-Bücklers' dystrophy which results in a nonuniform nomenclature and a permanent confusion in the evaluation of the superficial stroma dystrophies. This paper intends to clarify the original identity of the honeycomb corneal dystrophy and to distinguish it from the Reis-Bücklers' dystrophy.

PATIENTS AND METHODS

We examined seven patients of the original family of Thiel and Behnke. Five of them were newly detected, two of them were reexamined. The histological findings were reevaluated, and the diagnosis was proved by electron microscopic study of corneal specimens.

RESULTS

The honeycomb dystrophy is characterized by: (1) dominant inheritance, (2) early manifestation, (3) slow progression, (4) painful erosions during childhood, (5) subepithelial corneal opacities with a clear limbal zone, (6) honeycomb-shaped opacity pattern, (7) recurrence in the graft following keratoplasty, (8) subepithelial fibrous tissue in wave-like accumulation in histologic sections, (9) curly filaments observed by electron microscopy. The clinical symptoms hardly differ from those of Reis-Bücklers' dystrophy. The histological appearance, however, is clearly distinct and curly filaments are the pathognomonic ultrastructural features.

CONCLUSIONS

The honeycomb dystrophy represents a definite corneal disease. The terms "Reis-Bücklers' dystrophy" and "ring dystrophy" used for it up to now are wrong and should be eliminated in this context. The only correct term of the disease is honeycomb-shaped dystrophy (Thiel-Behnke) according to its first description and major clinical features. The eponym Reis-Bücklers' dystrophy should only be used for the corneal dystrophy described by Reis and Bücklers.

[Sorsby's fundus dystrophy: a literature review]

BACKGROUND

Sorsby's fundus dystrophy (SFD) is an autosomal dominant macular dystrophy first described in a 1949 study of five British families, and it has received attention because of its clinical similarity to age-related macular degeneration and recent identification of the pathogenic gene.

CLINICAL FEATURES

To date, about twenty families with SFD have been reported from Europe, North America, South Africa, Australia, and Japan. A review of the literature found that the age of onset is usually during the fourth or fifth decade of life, the prominent ophthalmoscopic finding is hemorrhagic or atrophic lesion in the macula, and functional prognosis is usually unfavorable due to additional peripheral chorioretinal dystrophy, ultimately leading to poor ambulatory vision in the late decades of life.

MOLECULAR GENETICS

Recent molecular studies have identified mutations in the tissue inhibitor of metalloproteinases-3 (TIMP 3) gene as the pathogenic gene defect.

CONCLUSIONS

TIMP 3 gene examinations not only allow accurate diagnosis but also lay the groundwork for future studies of potential therapeutic protocols.

Macular corneal dystrophy in Saudi Arabia: a study of 56 cases and recognition of a new immunophenotype

PURPOSE

To determine the immunophenotype or immunophenotypes of macular corneal dystrophy in Saudi Arabia.

METHODS

We studied 56 cases of macular corneal dystrophy. Tissue from 60 corneal transplant buttons was stained by the avidin-biotin complex method using an anti-keratan sulfate monoclonal antibody. The serum antigenic keratan sulfate was measured in 23 of the 56 patients, four unaffected relatives, and 13 individuals with chronic actinic keratopathy. Serum and corneal tissue were studied in 17 of the 50 affected individuals with corneal transplant material.

RESULTS

Thirty-five corneas (58.3%) of 29 of 50 patients did not react with anti-keratan sulfate monoclonal antibody. The stroma and abnormal intracellular and extracellular corneal accumulations reacted with anti-keratan sulfate monoclonal antibody in seven corneas (11.7%). The stroma in the other 18 corneas (30.0%) from 15 patients did not react with the anti-keratan sulfate monoclonal antibody, but corneal fibroblasts did. Twenty-one of the 23 patients with macular corneal dystrophy had no detectable serum antigenic keratan sulfate (< 9 ng/ml); two had values of 12 and 51 ng/ml, respectively, and their corneal stroma and abnormal accumulations reacted with anti-keratan sulfate monoclonal antibody.

CONCLUSIONS

We detected macular corneal dystrophy type IA, a new immunophenotype characterized by the lack of detectable antigenic keratan sulfate in the serum (< 9 ng/ml), and a corneal stroma that did not react with the keratan sulfate monoclonal antibody but in which corneal fibroblasts did react with keratan sulfate monoclonal antibody (in 15 of 50 patients).

Macular corneal dystrophy in Iceland. A clinical, genealogic, and immunohistochemical study of 28 patients

BACKGROUND

The frequency of different types of macular corneal dystrophy (MCD) was determined in Iceland where MCD accounts for one third of every penetrating keratoplasty.

METHODS

The authors determined the serum levels of antigenic keratan sulfate (aKS) in 27 patients with MCD and 53 unaffected family members by an enzyme-linked immunosorbent assay that uses an anti-KS monoclonal antibody (5-D-4). The authors also stained sections from 37 corneal buttons (including 2 regrafts) from 23 patients with MCD by the avidin-biotin complex method using the same anti-KS monoclonal antibody.

RESULTS

Based on the serum analyses, 22 patients had MCD type I and 5 had MCD type II. The corneas from patients without detectable KS in the serum lacked immunohistochemical reactivity to the anti-KS antibody. Every MCD cornea examined from individuals with normal serum KS levels showed KS reactivity. All 53 unaffected siblings and parents carrying the recessive gene had normal serum KS levels.

CONCLUSIONS

Macular corneal dystrophy types I (78.6%) and II (21.4%) both occur in Iceland. Members of affected sibships had only one of these types, not both. Nine patients with MCD type I and four persons with MCD type II belonged to a large pedigree in which individuals have been traced as far back as the beginning of the 16th century. The linking of patients with MCD types I and II in an inbred pedigree suggests that both types may be manifestations of the same abnormal gene rather than independent entities. The serum KS levels were not helpful in detecting heterozygous MCD carriers.

Clinical and histopathologic features of corneal dystrophies in Japan

PURPOSE

To examine retrospectively the frequency of various corneal dystrophies among Japanese patients who underwent keratoplasty or keratectomy at the authors' institution over a 34-year period, and to compare the histopathologic features of these disorders in the Japanese population with those reported in the Western literature.

METHODS

Corneal specimens obtained during keratectomy or keratoplasty (lamellar and penetrating) performed at the authors' institution from 1959 through 1992 were reviewed. Immunohistochemical studies were performed using monoclonal antibodies to keratan sulfate and gelsolin, as well as two lectins (concanavalin A and wheat germ agglutinin).

RESULTS

Of 1259 corneal specimens, 159 (12.6%) specimens from a total of 80 patients showed corneal dystrophy. Virtually all were non-Fuchs dystrophies; only one case of primary Fuchs dystrophy was identified histologically. Granular dystrophy and gelatinous drop-like dystrophy were the most common dystrophies identified in the specimens, largely because of multiple specimens from individual patients with recurrent disease. These two disorders accounted for 86 of the 159 specimens. In terms of numbers of patients, lattice dystrophy was the most common (26 patients, 32.5%), followed by macular dystrophy (16 patients, 20%), gelatinous drop-like dystrophy (15 patients, 18.8%), granular dystrophy (14 patients, 17.5%), and Avellino dystrophy (3 patients, 3.75%). Dystrophies represented by only one or two patients included congenital hereditary endothelial dystrophy, primary spheroidal keratopathy, posterior polymorphous dystrophy, Schnyder crystalline dystrophy, and Fuchs dystrophy.

CONCLUSIONS

This histopathologic study showed a very low incidence of Fuchs dystrophy in the authors' Japanese patient population, compared with the incidences seen in studies of populations in Western countries. Of the non-Fuchs dystrophies, lattice dystrophy was the most common among the patients, although there were large numbers of specimens with granular dystrophy and gelatinous drop-like dystrophy due to their recurrent character. The causes of clinical and histopathologic differences and similarities among the Japanese patients and the patients described in the Western literature are likely related to genetic factors, but a complete understanding of their specific mechanisms awaits future molecular biologic and genetic elucidation.

Cornea plana congenita gene assigned to the long arm of chromosome 12 by linkage analysis

We report the mapping of the locus for autosomal recessive cornea plana congenita (CNA2; MIM 217300) by linkage analysis to the approximately 10-cM interval between markers D12S82 and D12S327. The recessively inherited disorder studied here is more severe than dominant forms. Its main manifestations are reduced curvature and hazy limbus of the cornea, opacities in the corneal stroma, and marked corneal arcus at early age. Our results provide a starting point for the positional cloning of CNA2 and the elucidation of the pathogenesis of the disease.

Phenotypic variation in combined granular-lattice (Avellino) corneal dystrophy

OBJECTIVE

To describe the phenotypic variation exhibited by members of families with combined granular-lattice (Avellino) corneal dystrophy.

SETTING

We examined 40 patients (age range, 12 to 85 years) from six unrelated families with Avellino corneal dystrophy. This included the first individuals to ever be examined near the presumed site of origin in Italy. In addition, one family was the first to trace its origins to Germany rather than to Italy. We studied the phenotypic expression of the disease in the cornea, visual acuities, subjective complaints, complications, treatment, and histologic condition of these individuals.

RESULTS

The granular stromal lesions reach their mature quantity and size early in life, and appear as either gray and crumb-shaped deposits or superficial with an annular and planar distribution. The lattice component appears gradually, beginning and maturing later in life. The phenotypic variation within families was found to be substantial. Widely variable proportions of lattice and granular changes were found within single sibships. Visual acuities ranged from 20/20 to 20/400. Recurrent corneal erosions were present but infrequent. Subjective complaints included glare and decreased night vision. Penetrating keratoplasty was required in one individual to restore vision. Histopathologic examination revealed typical amyloid and granular deposits. Granular deposits were found replacing Bowman's membrane and extending to the corneal surface. These deposits probably represent the cause of recurrent erosions.

CONCLUSIONS

Combined granular and lattice corneal dystrophy may present with substantial phenotypic variation. The disease can be found in individuals who trace their ancestry to both Italy and Germany, a wider geographic distribution than previously proposed.

Schnyder's dystrophy of the cornea. A Swede-Finn connection

Schnyder's crystalline dystrophy is an uncommon hereditary disease in which there is abnormal deposition of cholesterol and/or lipid usually in the anterior stroma of the central and peripheral cornea. Four families with Schnyder's dystrophy have been identified in central Massachusetts. Of the 173 living members of these pedigrees, 60 patients were examined by the author. Eighteen patients had Schnyder's dystrophy. Affected individuals less than 23 years of age had bilateral, central disc-like corneal opacification. Those greater than 23 years of age also demonstrated prominent arcus lipoides. By age 40, all affected individuals developed a diffuse stromal haze. Only 50% of affected individuals had corneal crystalline deposits. Abnormal cholesterol deposition affected the entire stromal thickness in the majority of patients. Although the four families said that they were not related to each other, all had ancestry from towns within a 100-k area on the southwest coast of Finland. Patients in this area of Finland were examined by the author and demonstrated signs of Schnyder's dystrophy. This may represent the largest cohort of Schynder's dystrophy described to date.

Corneal dystrophies among patients undergoing keratoplasty in Saudi Arabia

Diseases leading to corneal opacities are inflammations, infections, metabolic causes, trauma, or genetically determined diseases. Corneal dystrophies may lead to corneal blindness. A clinical and pathological review of 2,108 corneal specimens received from December 1983 to January 1988 revealed 86 (4%) corneal specimens with corneal dystrophies. Fifty-three (62%) patients had macular dystrophy, 11 (13%) had congenital hereditary endothelial dystrophy (CHED), 12 (14%) had Fuchs' corneal dystrophy, 5 (6%) had lattice corneal dystrophy, and 3 (4%) had granular dystrophy. Macular dystrophy appears to be the most common cause of corneal dystrophy in Saudi Arabia. Twenty-two (42%) patients with macular dystrophy and 10 (91%) patients with CHED were the result of consanguineous marriages. Genetic counseling is advisable among families who carry the trait of CHED or macular corneal dystrophy.

Pseudoinflammatory fundus dystrophy: a follow-up study

We have performed a reinvestigation of a family with a presumably autosomal recessive form of pseudoinflammatory dystrophy, which we have followed for 25 years. The symptoms in this family are subretinal haemorrhages appearing at age 13-40 years in the central fundus, resulting in glial cicatrication in the outer retinal layers, progressive myopia and profound choroidal atrophy in the advanced stages of the disease. During the follow-up study, a new affected subject was found in the younger generation, and two collateral cases, who had earlier been considered as probably affected subjects, were now considered to have other fundus affections. The new case is the daughter of an affected female. The possibilities of an autosomal dominant mode of inheritance or pseudodominance are discussed. Extended genealogical studies showed that the parents of all the affected subjects, with the exception of the new case, have their origin in an area which was isolated until recently and have several common ancestors within the last 8-10 generations. Recessive inheritance also logically explains the appearance of the disease in so few other members in the vertical line of the family. To this fundus dystrophy, the rule of Lenz seems to apply: If more or less the same phenotype can be caused by both a recessive and a dominant gene, the phenotype caused by the recessive gene is generally manifested earlier and by more severe symptoms.

Granular corneal dystrophy Groenouw type I. 115 Danish patients. An epidemiological and genetic population study

An epidemiological and genetic study in Denmark of granular corneal dystrophy Groenouw type I is described. Ninety-one living patients were found. The disease is inherited as an autosomal dominant trait with a 100% penetrance of the gene. The 91 cases could be traced back to 6 different mutations. The mutation rate was estimated to be about 0.3/1,000,000; the possible sources of error of this estimate are discussed. The age distribution of the patients is shown to be similar to that of the Danish population in general.

The frequency of corneal dystrophies requiring keratoplasty in Europe and the U.S.A

A clinical and pathologic review of 1,335 corneal buttons received from 1964 to 1985 revealed 185 (13.9%) corneal dystrophies treated with keratoplasty. Fuch's endothelial dystrophy accounted for 132 (9.9%), occurring in females 80% of the time. Corneal dystrophies other than Fuchs' accounted for 53 cases (4.0%). Among the latter, the frequencies varied; 38% were granular, 30% were macular, and 19% were lattice dystrophies. The overall prevalence in series from Los Angeles and Baltimore is the same. However, there is a striking difference in the distribution of the frequencies of non-Fuchs' dystrophies. In the Erlangen series, granular dystrophy dominates (38%), while it is rare in the Baltimore series (4%); the reverse is true for lattice dystrophy (Erlangen 19%; Baltimore 37%), while macular dystrophy rates are similar.

Droplet degeneration of the cornea in North Cameroon. Prevalence and clinical appearances

The prevalence of droplet degeneration of the cornea in a defined population of 517 persons in north Cameroon was similar in males and females, but severe changes were commoner in elderly men. Most cases showed only mild changes of granularity and droplet formation in Bowman's zone, but they were sometimes widespread. More severe changes were seen in only nine patients. The clinical appearances are compared with those described from other parts of the world. In support of the aetiological role of direct sunlight, droplet degeneration was much more prevalent in the savanna than in the rain-forest in Cameroon. The condition ranges in severity from very mild to very severe, but difficulties in differential diagnosis, particularly in advanced cases, make it doubtful whether the same basic condition is being described in all cases. These doubts will be resolved only by properly conducted epidemiological studies in different parts of the world.

Recurrent erosion of the cornea

Altogether, 80 patients aged between 24 and 73 years with recurrent erosion of the cornea have been studied and compared with a control group of 200. The patients' erosions were divisible into macroform and microform types. The macroform occurred in 10%, the microform in 56%, and both types in the same patients in 31%. The macroform was more commonly related to trauma than the microform. However, many (40%) were spontaneous in origin. The most common cause of the initial trauma was a finger nail. The recurrences occurred at around the time of waking, either just before or just after. Difficulty in opening the eye occurred in 10%. There was little evidence of precipitating factors, but eye rubbing was admitted by 10% and barbiturates were implicated in 3%. The corneae were examined in the healed state, when a high incidence (59%) were found to have superficial corneal dystrophies of the fingerprint lines, bleb, and Bietti's lacunar (map-like) types. These are considered individually, particular attention being paid to the distinction between the various types of line resembling the fingerprint line. Epithelial microcysts were also a common finding (59%) and were sometimes of the Cogan type. In only 11% of patients were there no corneal signs in the healed state. The need for careful examination of the cornea by retroillumination, using both the iris and the fundus, is stressed. The control group, in contrast, showed a very low incidence of dystrophies and cysts. Treatment was given initially with either drops or ointment and no differences in healing were found. Debridement was performed in 12 eyes as an initial treatment and also in four eyes which were not healing on medical treatment. Debridement assisted healing, but did not prevent recurrence. One eye was treated with debridement and scarification and seven with carbolization. These procedures appeared to reduce the recurrence rate. Sodium chloride ointment 5% was found useful as a prophylactic taken at bedtime, and the recurrence rate increased when it was withdrawn.

Clinical findings, course, and progress of Bietti's corneal degeneration in the Dahlak islands

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Nama keratopathy

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Survey of ocular disease among the Nama people of South West Africa

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Posterior polymorphous dystrophy of the cornea

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