Surgical Removal of Subretinal Neovascular Membranes

Since 1991 we have been gaining experience in the surgical removal of submacular subretinal membranes in patients with presumed ocular histoplasmosis syndrome (POHS), idiopathic subretinal neovascularisation, myopia and age-related macular degeneration (AMD). Seventeen patients were operated between 1991 and 1993. Significant improvement of vision was achieved in 4 out of 5 patients with POHS, 3 out of 5 with idiopathic neovascularisation, 2 out of 4 with myopia but none of 3 patients with AMD. The results suggest that subretinal neovascularisation can be successfully removed in POHS and in some forms of idiopathic neovascularisation and myopia but probably not in AMD.

Visual impairment in Finnish Usher syndrome type III

PURPOSE

To evaluate visual impairment in Finnish Usher syndrome type 3 (USH3) and compare this with visual impairment in Usher syndrome types 1b (USH1b) and 2a (USH2a).

METHODS

We carried out a retrospective study of 28 Finnish USH3 patients, 24 Dutch USH2a patients and 17 Dutch USH1b patients. Cross-sectional regression analyses of the functional acuity score (FAS), functional field score (FFS*) and functional vision score (FVS*) related to age were performed for all patients. The FFS* and FVS* were calculated using the isoptre V-4 test target instead of the usual III-4 target. Statistical tests relating to regression lines and Student's t-test were used to compare between USH3 patients and the other genetic subtypes of Usher syndrome.

RESULTS

Cross-sectional analyses revealed significant deterioration in the FAS (1.3% per year), FFS* (1.4% per year) and FVS* (1.8% per year) with advancing age in the USH3 patient group. At a given age the USH3 patients showed significantly poorer visual field function than the USH2a patients.

CONCLUSIONS

The rate of deterioration in visual function in Finnish USH3 patients was fairly similar to that in Dutch USH1b or USH2a patients. At a given age, visual field impairment in USH3 patients was similar to that in USH1b patients but poorer than in USH2a patients.

Impact factors on intraocular pressure measurements in healthy subjects

AIM

To evaluate whether intraocular pressure (IOP) calculation by applanation tonometry is determined more essentially by the subject's neck position or by neck constriction.

METHODS

23 right eyes of 23 healthy subjects (12 male, 11 female) were included. IOP was measured by applanation tonometry with the TonoPen on sitting participants under four different conditions: with open collar upright (A) or with the head in the headrest of a slit lamp (B), with a tight necktie upright (C) or in slit lamp position (D). All measurements with neck constriction were performed 3 minutes after placing the necktie.

RESULTS

Mean IOP was 16.9 (SD 2.3) mm Hg (range 11-21 mm Hg) (A), 18.1 (SD 2.2) mm Hg (range 14-22 mm Hg) (B), 17.9 (SD 2.9) mm Hg (range 12-25 mm Hg) (C) and 18.7 (SD 2.7) mm Hg (range 13-24 mm Hg) (D). Mean IOP increased by 1.3 (SD 2.6) mm Hg (p = 0.028, paired t test, range +0.2 to +2.4 mm Hg) if subjects changed position from A to B. There was no statistically significant difference between measurements with or without neck constriction.

CONCLUSION

Applanation tonometry may be inaccurate if performed in slit lamp position. In contrast, tight neckties do not significantly affect IOP evaluation in healthy subjects.

The spectrum of retinal phenotypes caused by mutations in the ABCA4 gene

BACKGROUND

The majority of studies on the retina-specific ATP-binding cassette transporter (ABCA4) gene have focussed on molecular genetic analysis; comparatively few studies have described the clinical aspects of ABCA4-associated retinal disorders. In this study, we demonstrate the spectrum of retinal dystrophies associated with ABCA4 gene mutations.

METHODS

Nine well-documented patients representing distinct phenotypes in the continuum of ABCA4-related disorders were selected. All patients received an extensive ophthalmologic evaluation, including kinetic perimetry, fluorescein angiography, and electroretinography (ERG). Mutation analysis had been performed previously with the genotyping microarray (ABCR400 chip) and/or single-strand conformation polymorphism analysis in combination with direct DNA sequencing.

RESULTS

In all patients, at least one pathologic ABCA4 mutation was identified. Patient 10034 represented the mild end of the phenotypic spectrum, demonstrating exudative age-related macular degeneration (AMD). Patient 24481 received the diagnosis of late-onset fundus flavimaculatus (FFM), patient 15168 demonstrated the typical FFM phenotype, and patient 19504 had autosomal recessive Stargardt disease (STGD1). Patients 11302 and 7608 exhibited progression from FFM/STGD1 to cone-rod dystrophy (CRD). A more typical CRD phenotype was found in patients 15680 and 12608. Finally, the most severe ABCA4-associated phenotype was retinitis pigmentosa (RP) in patient 11366. This phenotype was characterised by extensive atrophy with almost complete loss of peripheral and central retinal functions.

CONCLUSION

We describe nine patients during different stages of disease progression; together, these patients form a continuum of ABCA4-associated phenotypes. Besides characteristic disorders such as FFM/STGD1, CRD and RP, intermediate phenotypes may be encountered. Moreover, as the disease progresses, marked differences may be observed between initially comparable phenotypes. In contrast, distinctly different phenotypes may converge to a similar final stage, characterised by extensive chorioretinal atrophy and very low visual functions. The identified ABCA4 mutations in most, but not all, patients were compatible with the resulting phenotypes, as predicted by the genotype-phenotype model for ABCA4-associated disorders. With the advent of therapeutic options, recognition by the general ophthalmologist of the various retinal phenotypes associated with ABCA4 mutations is becoming increasingly important.

Variable clinical features in patients with CDH23 mutations (USH1D-DFNB12)

OBJECTIVE

To describe the findings of audiovestibular and ophthalmologic examinations in four families with mutations in the CDH23 gene.

STUDY DESIGN

Family study.

SETTING

Tertiary referral center.

PATIENTS

Four DFNB12 patients from a large consanguineous Dutch family and six patients from three different Usher syndrome Type ID families were examined. All were identified by at least one pathogenic mutation in the CDH23 gene.

METHODS

Audiovestibular examinations consisted of standard pure-tone audiometry, vestibulo-ocular reflex, optokinetic nystagmus, and in some cases the cervico-ocular reflex. Linear regression analysis was used to evaluate progression of hearing impairment, and the degree of hearing impairment of DFNB12 was compared with that found for USH1D. Ophthalmologic examinations consisted of best-corrected visual acuity, Goldmann perimetry, slit-lamp examinations, color vision testing, dark adaptation, electroretinography, electro-oculography, funduscopy and photography of the retina, and sometimes fluorescein angiography.

RESULTS

The USH1D patients had significantly worse hearing impairment than the DFNB12 patients. The DFNB12 patients, identified by missense mutations in CDH23, had normal retinal and vestibular function. All USH1D patients had splice-site mutations in CDH23 and a typical Usher syndrome Type I phenotype. One DFNB12 patient had slightly abnormal yellowish flecks in the posterior poles of both eyes.

CONCLUSION

Recessive missense mutations in CDH23 lead to a milder phenotype (DFNB12) than splice-site mutations (USH1D); however, abnormal bilateral flecks, suggestive for lipofuscin accumulation, can be observed in DFNB12 patients.

USH2A mutation analysis in 70 Dutch families with Usher syndrome type II

Usher syndrome type II (USH2) is characterised by moderate to severe high-frequency hearing impairment, progressive visual loss due to retinitis pigmentosa and intact vestibular responses. Three loci are known for USH2, however, only the gene for USH2a (USH2A) has been identified. Mutation analysis of USH2A was performed in 70 Dutch USH2 families. Ten mutations in USH2A were detected, of which three are novel, c.949C>A, c.2242C>T (p.Gln748X) and c.4405C>T (p.Gln1468X). Including 9 previously published Dutch USH2a families, estimates of the prevalence of USH2a in the Dutch USH2 population were made. Mutations were identified in 62% of the families. In 28% both mutated alleles were identified, whereas in 34% the mutation in only one allele was found. It is estimated that about 28% of the Dutch USH2 families have a different causative gene. Analysis of deduced haplotypes suggests that c.1256G>T (p.Cys419Phe) is a Dutch ancestral mutation, occurring in 16% of the alleles.

Autosomal dominant rhegmatogenous retinal detachment--clinical appearance and surgical outcome

PURPOSE

To study the clinical appearance and surgical results of autosomal dominantly inherited rhegmatogenous retinal detachments (RRDs).

METHODS

After prospective examination of all but two family members, the medical records of 16 affected patients (21 eyes) of two families from the Netherlands with autosomal dominantly inherited RRD were retrospectively evaluated. Special attention was paid to the age at onset, the ocular morphology and the clinical appearance of the RRD. The type and number of the various surgical procedures were analyzed with respect to preoperative appearance of the RRD, postoperative results and final visual acuity.

RESULTS

The mean age at onset of RRD of affected individuals in families A and B was 37 +/- 18 years and 19 +/- 10 years, respectively. The mean ocular axial length in the two families was 24.7 mm and 26.7 mm. The mean number of retinal defects preoperatively found was 2.2 in family A and 7.1 in family B. Round, atrophic retinal holes predominated. Two of 21 affected eyes showed significant preoperative proliferative vitreoretinopathy. Pars plana vitrectomy was the primary procedure in 4 cases; extra ocular buckling was the initial procedure in 15 cases. One eye received scleral folding with diathermy as primary surgery. Redetachment following surgery occurred in 5 of 10 cases in family A and 4 of 10 eyes in family B. Anatomical success could be achieved in 9 of 10 and 8 of 10 eyes in families A and B, respectively.

CONCLUSIONS

In these families the prevalence of RRD is high. Most patients were affected at a relatively young age compared with non-genetically linked forms of RRD. Because of the low success rate of surgical intervention and, subsequently, the high number of operations necessary to achieve reattachment of the retina, the use of diagnostic genetic techniques to identify individuals at risk would be advisable. In these subjects measures to prevent RRD are an option, even when anatomical substrates of precursors of RRD are absent.

Evaluation of visual impairment in Usher syndrome 1b and Usher syndrome 2a

PURPOSE

To evaluate visual impairment in Usher syndrome 1b (USH1b) and Usher syndrome 2a (USH2a).

METHODS

We carried out a retrospective study of 19 USH1b patients and 40 USH2a patients. Cross-sectional regression analyses of the functional acuity score (FAS), functional field score (FFS) and functional vision score (FVS) related to age were performed. Statistical tests relating to regression lines and Student's t-test were used to compare between (sub)groups of patients. Parts of the available individual longitudinal data were used to obtain individual estimates of progressive deterioration and compare these to those obtained with cross-sectional analysis. Results were compared between subgroups of USH2a patients pertaining to combinations of different types of mutations.

RESULTS

Cross-sectional analyses revealed significant deterioration of the FAS (0.7% per year), FFS (1.0% per year) and FVS (1.5% per year) with advancing age in both patient groups, without a significant difference between the USH1b and USH2a patients. Individual estimates of the deterioration rates were substantially and significantly higher than the cross-sectional estimates in some USH2a cases, including values of about 5% per year (or even higher) for the FAS (age 35-50 years), 3-4% per year for the FFS and 4-5% per year for the FVS (age > 20 years). There was no difference in functional vision score behaviour detected between subgroups of patients pertaining to different biallelic combinations of specific types of mutations.

CONCLUSIONS

The FAS, FFS and FVS deteriorated significantly by 0.7-1.5% per year according to cross-sectional linear regression analysis in both USH1b and USH2a patients. Higher deterioration rates (3-5% per year) in any of these scores were attained, according to longitudinal data collected from individual USH2a patients. Score behaviour was similar across the patient groups and across different biallelic combinations of various types of mutations. However, more elaborate studies, preferably covering longitudinal data, are needed to obtain conclusive evidence.

The benign concentric annular macular dystrophy locus maps to 6p12.3-q16

PURPOSE

To describe the clinical findings and to identify the genetic locus in a Dutch family with autosomal dominant benign concentric annular macular dystrophy (BCAMD).

METHODS

All family members underwent ophthalmic examination. Linkage analysis of candidate retinal dystrophy loci and a whole genome scan were performed. Five candidate genes from the linked locus were analyzed for mutations by direct sequencing.

RESULTS

The BCAMD phenotype is initially characterized by parafoveal hypopigmentation and good visual acuity, but progresses to a retinitis pigmentosa-like phenotype. Linkage analysis established complete segregation of the BCAMD phenotype (maximum multipoint LOD score, 3.8) with DNA markers at chromosome 6, region p12.3-q16. Recombination events defined a critical interval spanning 30.7 cM at the long arm of chromosome 6 between markers D6S269 and D6S300. This interval encompasses several retinal dystrophy loci, including the ELOVL4 gene, mutated in autosomal dominant Stargardt disease, and the RIM1 gene, mutated in autosomal dominant cone-rod dystrophy, as well as the retinally expressed GABRR1 and -2 genes. Mutation screening of these four genes revealed no mutations. Sequence analysis of the interphotoreceptor matrix proteoglycan 1 gene IMPG1, also residing in the BCAMD locus, revealed a single base-pair change (T-->C) of nucleotide 1866 in exon 13, resulting in a Leu579Pro amino acid substitution. This mutation was absent in 190 control individuals.

CONCLUSIONS

Significant linkage was found for the BCAMD defect with chromosomal 6, region p12.3-q16. A Leu579Pro mutation in the IMPG1 gene may play a causal role.

Endogenous endophthalmitis after otitis media

PURPOSE

To report a case of bacterial endophthalmitis after otitis media in a healthy adult.

DESIGN

Interventional case report.

METHODS

A healthy 49-year-old Caucasian woman developed acute otitis media of the right ear. Three weeks after the first onset there was a recurrence of the otitis media, with perforation of the tympanic membrane. Two days after this, the woman presented at our clinic with endophthalmitis of the right eye.

RESULTS

A culture of vitreous material grew Streptococcus pyogenes (Streptococcus Lancefield group A). The same strain was found in a smear from the perforated ear. Despite aggressive treatment, the affected eye had to be eviscerated.

CONCLUSIONS

Otitis media can result in a bacteremia. This may, even in a healthy adult, lead to a devastating endogenous bacterial endophthalmitis.

A Peculiar Autosomal Dominant Macular Dystrophy Caused by an Asparagine Deletion at Codon 169 in the Peripherin/RDS Gene

OBJECTIVE

To describe the clinical and genetic findings in a family with a peculiar autosomal dominant macular dystrophy with peripheral deposits.

METHODS

All family members underwent an ophthalmic examination, and their genomic DNA was screened for mutations in the human retinal degeneration slow (peripherin/RDS) and rhodopsin genes. In selected cases, fluorescein angiography and electrophysiologic testing were performed.

RESULTS

The age at onset of the disease was between the third and fourth decades of life, starting with mild visual acuity loss and periods of metamorphopsia. Clinical signs included subretinal yellowish macular deposits evolving into geographic atrophy and retinal hypopigmentation and hyperpigmentation. Electroretinography demonstrated rod dysfunction, and electro-oculograms were mildly to severely disturbed. All affected members were found to carry a 3-base pair deletion affecting codon 169 of the peripherin/RDS gene. This mutation resulted in an asparagine (Asn) deletion in the peripherin/RDS protein and was not found in 155 control individuals.

CONCLUSION

A deletion of Asn169 in the peripherin/RDS protein causes a peculiar form of autosomal dominant macular dystrophy in a large family from the Netherlands.

CLINICAL RELEVANCE

Characterizing the phenotype and genotype in this family may, in the long term, result in a better understanding of the precise mechanism underlying this retinal degeneration.

Bilateral detachment of the macular neuroepithelium in a patient with Klinefelter syndrome

PURPOSE

To describe the occurrence of atypical, bilateral detachment of the macular neuroepithelium and Klinefelter syndrome in a young patient.

METHODS

Case report.

RESULTS

A 20-year-old male of Chinese origin with karyotype 47,XXY presented with bilateral central neurosensory retinal detachment. There was spontaneous improvement.

CONCLUSIONS

An atypical form of detachment of the macular neuroepithelium was seen in a young patient with Klinefelter syndrome. The pathophysiological mechanism is not clear. The possibility of a hormonal imbalance is discussed. A differential diagnostic consideration is central serous chorioretinopathy and a mild form of Vogt-Koyanagi-Harada syndrome. This case is of interest because of the rarity of association between Klinefelter syndrome and chorioretinal abnormalities.

Usher syndrome type III can mimic other types of Usher syndrome

Clinical and genetic characteristics are presented of 2 patients from a Dutch Usher syndrome type III family who have a new homozygous USH3 gene mutation: 149-152delCAGG + insTGTCCAAT. One individual (IV:1) is profoundly hearing impaired and has normal vestibular function and retinitis punctata albescens (RPA). The other individual is also profoundly hearing impaired, but has well-developed speech, vestibular areflexia, and retinitis pigmentosa sine pigmento (RPSP). These findings suggest that Usher syndrome type III can be clinically misdiagnosed as either Usher type I or II; that Usher syndrome patients who are profoundly hearing impaired and have normal vestibular function should be tested for USH3 mutations; and that RPA and RPSP can occur as fundoscopic manifestations of pigmentary retinopathy in Usher syndrome.

Genetic heterogeneity of butterfly-shaped pigment dystrophy of the fovea

PURPOSE

Butterfly-shaped macular dystrophy (BSMD) has so far only been associated with mutations in the peripherin/RDS gene. The initial aim of our study was to investigate the peripherin/RDS gene as the causative gene in a family with BSMD. Subsequently the putative involvement of the ROM-1 gene, 4 genes expressed in cone photoreceptors, all known non-syndromic macular, retinal pigment epithelium and choroidal dystrophy loci, all known Leber congenital amaurosis loci and all known non-syndromic congenital and stationary retinal disease loci was examined.

METHODS

Thirteen members from the original family with autosomal dominant BSMD were examined. The protein coding exons of the peripherin/RDS gene were screened for mutations by sequence analysis. Linkage analysis was performed using markers flanking the peripherin/RDS gene to rule out the presence of a heterozygous deletion. Likewise, involvement of the ROM-1 gene, four cone genes, 41 non-syndromic retinal disease loci and one syndromic retinal disease locus was investigated.

RESULTS

Sequence analysis of the peripherin/RDS gene revealed no mutations. In addition, the BSMD phenotype could not be genetically linked to the peripherin/RDS gene, the ROM-1 gene and the four cone genes nor to any of the 42 retinal disease loci.

CONCLUSIONS

This study reveals genetic heterogeneity for BSMD by the identification of a BSMD family, which is not associated with a mutation in the peripherin/RDS gene nor with any other known non-syndromic retinal disease gene.

Peripheral retinal nonperfusion associated with chronic myeloid leukemia

PURPOSE

To report a case of peripheral retinal nonperfusion and chronic myeloid leukemia in a 23-year-old woman.

DESIGN

Observational case report.

METHODS

A complete ophthalmic and systemic evaluation was performed.

RESULTS

Ophthalmic examination revealed peripheral retinal nonperfusion with retinal neovascularization in both eyes. Fluorescein angiography of both eyes showed a marked midperipheral and peripheral avascular retina temporally with arteriovenous anastomosis and seafan neovascularizations. Blood work showed no abnormalities, although marked leucocytosis (up to 750 x 10(9)/l) and thrombocytosis (646 x 10(9)/l) were present in 1998 when the patient was diagnosed with leukemia. Following treatment, the patient has been in remission.

CONCLUSIONS

Peripheral retinal nonperfusion with retinal neovascularization may occur as a complication of chronic myeloid leukemia. In contrast to other studies describing this association, our patient had a bilateral peripheral retinal nonperfusion with seafan neovascularizations without relapse of the myeloid leukemia and without any of the other retinal signs associated with chronic myeloid leukemia, such as tortuosity of veins, intraretinal or preretinal hemorrhages, and cotton-wool exudates.

Mutations in the calcium-binding motifs of CDH23 and the 35delG mutation in GJB2 cause hearing loss in one family

We have ascertained a multi-generation family with apparent autosomal recessive non-syndromic childhood hearing loss (DFNB). Failure to demonstrate linkage in a genome-wide scan with 300 polymorphic markers has suggested genetic heterogeneity for the hearing loss in this family. This heterogeneity could be demonstrated by analysis of candidate loci and genes for DFNB. Patients in one branch of the family (branch C) are homozygous for the 35delG mutation in the GJB2 gene (DFNB1). Patients in two other branches (A and B) carry two new mutations in the cadherin 23 ( CDH23) gene (DFNB12). A homozygous CDH23 c.6442G-->A (D2148N) mutation is present in branch A. Patients in branch B are compound heterozygous for this mutation and the c.4021G-->A (D1341N) mutation. The substituted aspartic acid residues are highly conserved and are part of the calcium-binding sites of the extracellular cadherin (EC) domains. Molecular modeling of the mutated EC domains of CDH23 based on the structure of E-cadherin indicates that calcium-binding is impaired. In addition, other aspartic and glutamic acid residue substitutions in the highly conserved calcium-binding sites reported to cause DFNB12 are also likely to result in a decreased affinity for calcium. Since calcium provides rigidity to the elongated structure of cadherin molecules enabling homophilic lateral interaction, these mutations are likely to impair interactions of CDH23 molecules either with CDH23 or with other proteins. DFNB12 is the first human disorder that can be attributed to inherited missense mutations in the highly conserved residues of the extracellular calcium-binding domain of a cadherin.

[From gene to disease; genetic causes of hearing loss and visual impairment sometimes accompanied by vestibular problems (Usher syndrome)]

Usher syndrome is an autosomal recessively inherited disease, characterised by sensorineural hearing loss, tapetoretinal degeneration and in some cases vestibular problems. Based on the clinical heterogeneity, the disease can be classified into three clinical types (I, II and III), which have their own genetic subtypes (Usher 1A-Usher IG, Usher 2A-Usher 2C and Usher 3). The majority of the Usher type I cases are caused by mutations in the MYO7A gene (Usher 1B) while mutations in the USH2A gene (Usher 2A) are the cause of most cases of type II. Usher syndrome type III, caused by mutations in the USH3 gene, is frequently seen only in Finland.

Side effects after radiotherapy of age-related macular degeneration with the Nijmegen technique

BACKGROUND

In a randomized trial concerning radiotherapy for age-related macular degeneration, fluorescein angiograms were taken of controls and patients. In this study the frequency of side effects in eyes receiving radiotherapy with the Nijmegen technique is compared with the findings in the eyes of controls.

METHODS

Patients receiving treatment were irradiated by two isocentric photon beams in four fractions of 6 Gy that were directed to the macular area at 30 degrees and -30 degrees with regard to the optical axis. The most recent fluorescein angiograms of the randomized eyes (32 treated and 31 control eyes) were scored by two independent researchers, using a scoring form with nine features of radiation retinopathy: nonperfusion, macular edema, microaneurysms, retinal hemorrhages, cotton-wool spots, perifoveal telangiectasis, vascular sheathing, retinal neovascularization, and radiation-associated choroidal neovasculopathy. The results were graded as: no retinopathy (grade 0), mild retinopathy (grade 1), moderate retinopathy (grade 2), and severe retinopathy (grade 3).

RESULTS

In the treated group 6 patients (18.8%) were grade 1, 10 patients (31.2%) were grade 2 and 7 patients (21.9%) were grade 3. In the control group 9 patients (29.0%) were grade 1, 11 patients (35.5%)were grade 2 and 2 patients (6.5%) were grade 3. There were no patients with retinal neovascularization.

CONCLUSION

With the Nijmegen technique a relatively high dose of radiation can be applied to a small retinal area. In only a minority of cases does some evidence of radiation retinopathy occur.

Autosomal recessive cerebellar ataxia with bull's-eye macular dystrophy

PURPOSE

In 1980, we published in the American Journal of Ophthalmology two siblings with hereditary ataxia and atrophic maculopathy. The report is cited in the literature as autosomal dominant cerebellar ataxia with retinal degeneration. The purpose of the present study is to document the progression of the neurodegenerative disorder and to review the diagnosis.

DESIGN

Observational case report.

METHODS

Twenty years after the original publication, the 52-year-old male patient had new ocular and neurologic examinations, fluorescein angiography, molecular genetic analysis, and biochemical testing.

RESULTS

Fluorescein angiography showed marked progression of the macular dystrophy to a bull's-eye configuration. Genetic analysis of the patient did not show CAG trinucleotide repeat expansion in the various spinocerebellar ataxia genes. This excludes the diagnosis of autosomal dominant cerebellar ataxia with macular degeneration (ADCA type II) with mutation of the spinocerebellar ataxia 7 gene. Major causes of autosomal recessive cerebellar ataxia with retinal degeneration, including Friedreich ataxia and congenital disorders of glycosylation, were also excluded.

CONCLUSION

The two patients, previously published in the American Journal of Ophthalmology by Eerola and coworkers, did not suffer from presently recognized disorders with cerebellar ataxia and retinal degeneration. The Eerola syndrome probably represents a separate neurodegenerative entity characterized by autosomal recessive cerebellar ataxia and progressive macular dystrophy with a bull's-eye pattern.

Clinical characterization, linkage analysis, and PRPC8 mutation analysis of a family with autosomal dominant retinitis pigmentosa type 13 (RP13)

A Dutch family with autosomal dominant retinitis pigmentosa (adRP) displayed a phenotype characterized by an early age of onset, a diffuse loss of rod and cone sensitivity, and constricted visual fields (type I). One male showed a mild progression of the disease. Linkage analysis showed cosegregation of the genetic defect with markers from chromosome 17p13.1-p13.3, a region overlapping the RP13 locus. The critical interval of the RP locus as defined in this family was flanked by D17S926 and D17S786, with a maximal lod score of 4.2 (theta = 0.00) for marker D17S1529. Soon after the mapping of the underlying defect to the 17p13 region, a missense mutation (6970G>A; R2310K) was identified in exon 42 of the splicing factor gene PRPC8 in one patient of this family. Diagnostic restriction enzyme digestion of exon 42 amplified from genomic DNA of all family members revealed that the R2310K mutation segregated fully with the disease. The type I phenotype observed in this family is similar to that described for three other RP13 families with mutations in PRPC8.

Central areolar choroidal dystrophy associated with dominantly inherited drusen

AIM

To describe the clinical and genetic aspects of a retinal dystrophy that combines central areolar choroidal dystrophy (CACD) and autosomal dominantly inherited drusen.

METHODS

The members of three unrelated families who demonstrated the rare combination of CACD and dominant drusen were clinically and angiographically investigated. In addition, DNA samples from the members of these families were screened for the Arg142Trp mutation in the peripherin/retinal degeneration slow (RDS) gene.

RESULTS

The severity of the CACD/dominant drusen maculopathy was age related and the expression of the phenotype varied. All affected individuals carried the Arg142Trp mutation in the peripherin/RDS gene. The clinical spectrum ranged from CACD without noticeable drusen in four individuals to the fully expressed phenotype of CACD with drusen in 14 individuals.

CONCLUSION

CACD macular dystrophy is associated with dominant drusen in most individuals carrying the Arg142Trp mutation in the peripherin/RDS gene in the three families described. There are no individuals with dominant drusen in the absence of the Arg142Trp mutation, suggesting that the Arg142Trp mutation is one of the factors predisposing to drusen development.

Null mutation in the human 11-cis retinol dehydrogenase gene associated with fundus albipunctatus

PURPOSE

Recent studies show that mutations in the gene encoding 11-cis retinol dehydrogenase are associated with fundus albipunctatus. The authors wanted to investigate whether additional, more severe, mutations in the 11-cis retinol dehydrogenase gene might be responsible for more severe forms of hereditary retinal diseases.

DESIGN

Case-control molecular genetics study.

PARTICIPANTS AND CONTROLS

Two index patients, 7 relatives, and 50 control individuals.

METHODS

The authors screened two index patients diagnosed with fundus albipunctatus for mutations in exons 2 to 5 and exon/intron boundaries of the 11-cis retinol dehydrogenase gene by direct sequencing. Control individuals were screened for the presence of the mutations using allele-specific oligonucleotide hybridization.

MAIN OUTCOME MEASURES

Mutations in exons 2 to 5 and exon/intron boundaries of the 11-cis retinol dehydrogenase gene.

RESULTS

In a compound heterozygote, two novel mutations were found: a 4 bp insertion in exon 2 and a missense mutation Cys267Trp in exon 5. In a second pedigree, a homozygous frameshift mutation in codon 43 (Arg42ct[1-bpdel]) was detected. In both families, the mutations segregate with the disease. The mutations were not found in 50 control individuals.

CONCLUSIONS

On the basis of our observations, it is unlikely that mutations in the 11-cis retinol dehydrogenase gene are associated with other, possibly more severe, retinal pathologic conditions/dystrophies or syndromic diseases in which the retina is also affected.

Leber congenital amaurosis and retinitis pigmentosa with Coats-like exudative vasculopathy are associated with mutations in the crumbs homologue 1 (CRB1) gene

Mutations in the crumbs homologue 1 (CRB1) gene cause a specific form of retinitis pigmentosa (RP) that is designated "RP12" and is characterized by a preserved para-arteriolar retinal pigment epithelium (PPRPE) and by severe loss of vision at age <20 years. Because of the early onset of disease in patients who have RP with PPRPE, we considered CRB1 to be a good candidate gene for Leber congenital amaurosis (LCA). Mutations were detected in 7 (13%) of 52 patients with LCA from the Netherlands, Germany, and the United States. In addition, CRB1 mutations were detected in five of nine patients who had RP with Coats-like exudative vasculopathy, a relatively rare complication of RP that may progress to partial or total retinal detachment. Given that four of five patients had developed the complication in one eye and that not all siblings with RP have the complication, CRB1 mutations should be considered an important risk factor for the Coats-like reaction, although its development may require additional genetic or environmental factors. Although no clear-cut genotype-phenotype correlation could be established, patients with LCA, which is the most severe retinal dystrophy, carry null alleles more frequently than do patients with RP. Our findings suggest that CRB1 mutations are a frequent cause of LCA and are strongly associated with the development of Coats-like exudative vasculopathy in patients with RP.

Juvenile macular dystrophy associated with deficient activity of fatty aldehyde dehydrogenase in Sjögren-Larsson syndrome

PURPOSE

To report the ocular manifestations associated with the Sjögren-Larsson syndrome in a series of patients with proven fatty aldehyde dehydrogenase deficiency. To emphasize the clinical importance of the ophthalmological features of the Sjögren-Larsson syndrome. To discuss the metabolic disturbances that might give rise to the ophthalmological picture.

METHODS

Fifteen patients with Sjögren-Larsson syndrome underwent a standardized ophthalmological examination. In patients of appropriate age, and who were able to cooperate, additional investigations were performed.

RESULTS

All patients exhibited bilateral, glistening yellow-white crystalline deposits that were located in the innermost retinal layers and appeared during the first 2 years of life. Repeated fundus photography in individual patients showed that the dots became more numerous as the patients got older. Photophobia, subnormal visual acuity, myopia, and astigmatism were found in most of the patients. Fluorescein angiography was performed in three patients and showed a mottled hyperfluorescence of the retinal pigment epithelium, without leakage. Color vision, electroretinography, and electro-oculography could be performed in only a small number of patients and showed no abnormalities. Visual evoked potentials were found to be abnormal in six of eight patients.

CONCLUSIONS

In Sjögren-Larsson syndrome, patients exhibit highly characteristic bilateral, glistening yellow-white retinal dots from the age of 1 to 2 years onward. The number of dots increases with age. The extent of the macular abnormality does not correlate with the severity of the ichthyosis or with the severity of the neurological abnormalities. A high percentage of patients shows additional ocular signs and symptoms, notably marked photophobia.

Mutations in the ABCA4 (ABCR) gene are the major cause of autosomal recessive cone-rod dystrophy

The photoreceptor cell-specific ATP-binding cassette transporter gene (ABCA4; previously denoted "ABCR") is mutated, in most patients, with autosomal recessive (AR) Stargardt disease (STGD1) or fundus flavimaculatus (FFM). In addition, a few cases with AR retinitis pigmentosa (RP) and AR cone-rod dystrophy (CRD) have been found to have ABCA4 mutations. To evaluate the importance of the ABCA4 gene as a cause of AR CRD, we selected 5 patients with AR CRD and 15 patients from Germany and The Netherlands with isolated CRD. Single-strand conformation-polymorphism analysis and sequencing revealed 19 ABCA4 mutations in 13 (65%) of 20 patients. In six patients, mutations were identified in both ABCA4 alleles; in seven patients, mutations were detected in one allele. One complex ABCA4 allele (L541P;A1038V) was found exclusively in German patients with CRD; one patient carried this complex allele homozygously, and five others were compound heterozygous. These findings suggest that mutations in the ABCA4 gene are the major cause of AR CRD. A primary role of the ABCA4 gene in STGD1/FFM and AR CRD, together with the gene's involvement in an as-yet-unknown proportion of cases with AR RP, strengthens the idea that mutations in the ABCA4 gene could be the most frequent cause of inherited retinal dystrophy in humans.

Hereditary retinal dystrophies and choroidal neovascularization

BACKGROUND

Choroidal neovascularization infrequently occurs in patients affected by hereditary retinal dystrophies.

METHODS

We studied eight patients suffering from different hereditary retinal dystrophies (Best's disease, reticular dystrophy, butterfly-shaped dystrophy, gyrate atrophy, and retinitis pigmentosa) who developed choroidal neovascularization. All patients underwent complete ophthalmic evaluation, electrophysiology, colour vision testing, and fluorescein angiography. In some patients, ICG video-angiography was also performed. Laser treatment was carried out in only one patient.

RESULTS

The mean duration of follow-up was 41.7 months (range 6-148 months). At CNV diagnosis, the mean VA was 0.23 (range 0.02-0.6). At the last follow-up, mean VA was 0.34 (range HM to 0.9). At the last follow-up, fluorescein angiography showed a focal, atrophic scar in seven eyes, a fibrotic membrane in two eyes and a still active membrane in two cases.

CONCLUSION

We emphasize the relatively favourable visual prognosis in patients suffering from inherited retinal dystrophies complicated with choroidal neovascularization. Therapeutic approaches other than laser treatment could be attempted in these patients.

Disruption of the 11-cis-retinol dehydrogenase gene leads to accumulation of cis-retinols and cis-retinyl esters

To elucidate the possible role of 11-cis-retinol dehydrogenase in the visual cycle and/or 9-cis-retinoic acid biosynthesis, we generated mice carrying a targeted disruption of the 11-cis-retinol dehydrogenase gene. Homozygous 11-cis-retinol dehydrogenase mutants developed normally, including their retinas. There was no appreciable loss of photoreceptors. Recently, mutations in the 11-cis-retinol dehydrogenase gene in humans have been associated with fundus albipunctatus. In 11-cis-retinol dehydrogenase knockout mice, the appearance of the fundus was normal and punctata typical of this human hereditary ocular disease were not present. A second typical symptom associated with this disease is delayed dark adaptation. Homozygous 11-cis-retinol dehydrogenase mutants showed normal rod and cone responses. 11-cis-Retinol dehydrogenase knockout mice were capable of dark adaptation. At bleaching levels under which patients suffering from fundus albipunctatus could be detected unequivocally, 11-cis-retinol dehydrogenase knockout animals displayed normal dark adaptation kinetics. However, at high bleaching levels, delayed dark adaptation in 11-cis-retinol dehydrogenase knockout mice was noticed. Reduced 11-cis-retinol oxidation capacity resulted in 11-cis-retinol/13-cis-retinol and 11-cis-retinyl/13-cis-retinyl ester accumulation. Compared with wild-type mice, a large increase in the 11-cis-retinyl ester concentration was noticed in 11-cis-retinol dehydrogenase knockout mice. In the murine retinal pigment epithelium, there has to be an additional mechanism for the biosynthesis of 11-cis-retinal which partially compensates for the loss of the 11-cis-retinol dehydrogenase activity. 11-cis-Retinyl ester formation is an important part of this adaptation process. Functional consequences of the loss of 11-cis-retinol dehydrogenase activity illustrate important differences in the compensation mechanisms between mice and humans. We furthermore demonstrate that upon 11-cis-retinol accumulation, the 13-cis-retinol concentration also increases. This retinoid is inapplicable to the visual processes, and we therefore speculate that it could be an important catabolic metabolite and its biosynthesis could be part of a process involved in regulating 11-cis-retinol concentrations within the retinal pigment epithelium of 11-cis-retinol dehydrogenase knockout mice.

Retinoic acid delays transcription of human retinal pigment neuroepithelium marker genes in ARPE-19 cells

The effect of retinoic acid on the differentiation of a human retinal pigment epithelium-derived cell line ARPE-19 was studied. Differentiation of ARPE-19 cells is delayed by retinoic acid. The minimum all-trans-retinoic acid concentration needed for delay of ARPE-19 differentiation is 1 microM. A delay of differentiation was also observed using 1 microM 9-cis or 13-cis-retinoic acid. Differentiation at the molecular level was studied by analyzing transcription of two RPE-marker genes, RPE65 and peropsin. In the presence of 1 microM retinoic acid the onset of transcription of both genes was delayed by 2-3 weeks. We conclude that all-trans-, 9-cis-, and 13-cis-retinoic acid delay differentiation of ARPE-19 cells into cells that phenotypically resemble cells from the human retinal pigment epithelium.

Holmium Laser Thermal Keratoplasty for Hyperopia and Astigmatism After Photorefractive Keratectomy

PURPOSE

To report results of holmium laser thermal keratoplasty used to treat induced hyperopia and induced, as well as pre-existing astigmatism after photorefractive keratectomy.

METHODS

Sixteen eyes of 16 patients were included in this study. Contact holmium laser (Technomed Holmium 25) was used in 7 patients to correct hyperopia (8 spots at 8 or 9 mm) and in 9 patients to correct astigmatism (4 spots at 7, 8, or 9 mm). Follow-up evaluation was done after at least 6 months. The effectiveness, stability, and safety of the procedure were investigated.

RESULTS

Spherical correction was ineffective (1.00 D or less) when applied at the 9-mm diameter treatment zone. Spherical correction applied at the 8-mm diameter treatment zone was ineffective in 1 eye. Three eyes achieved 1.00 to 2.00 D change, but 2 of these eyes showed an induced astigmatic change as well. Correction of astigmatism at the 7-mm diameter treatment zone resulted in a 0 to 4.00 D cylinder component change. Treatment at the 8-mm diameter treatment zone showed a 0 to 1.50 D effect and at the 9-mm treatment zone, 0.25 to 1.50 D. All eyes that achieved significant improvement (1.00 D or more change in cylinder component) showed significant overcorrection in the first postoperative phase. There were no sight threatening complications.

CONCLUSION

Holmium laser thermal keratoplasty can be useful for the treatment of overcorrection and induced as well as pre-existing astigmatism after photorefractive keratectomy. However, predictability is low and astigmatism can be induced with the attempted spherical correction.

Retinoic acid receptors and retinoid X receptors in the mature retina: subtype determination and cellular distribution

PURPOSE

In the mature retina retinoic acid (RA) biosynthesis was reported to be regulated by light. RA is of vital importance for proper function of the retina. RA activity is mediated by interaction with nuclear retinoic acid receptors (RARs) and retinoid X receptors (RXRs). The purpose of this study was to determine if and which RARs and RXRs are present in the mature retina, and to determine their location within the retina.

METHODS

The reverse transcriptase polymerase chain reaction (RT-PCR) was used to amplify cDNA fragments encoding RARalpha, RARbeta, RARgamma, RXRalpha, RXRbeta, and RXRgamma from human retinal RNA. RT-PCR products were cloned, sequenced, and used in Northern blot experiments. Antibodies directed against each receptor subtype were used for immunocytochemical analysis.

RESULTS

RT-PCR and Northern blot analysis indicated that all RAR and RXR subtypes are present in the mature retina. Western blot analysis, using a cytoplasmic protein fraction isolated from the bovine and human neural retina, showed the presence of RXRalpha. Immunocytochemical analysis of the human, bovine, and rat retina showed that RARalpha is highly expressed in the outer segments of cone photoreceptor cells. RXRalpha expression was observed in the rod inner segment layer. RXRgamma was detected in the nuclei and outer segments of cone photoreceptor cells.

CONCLUSIONS

The retinal expression pattern of RARs and RXRs is heterogeneous. The observation that RXRalpha is present in rods whereas RARalpha is present in cones, suggests a mechanism by which RA that is produced upon bleaching, could generate different responses in the two photoreceptor cell subtypes.

Mutations in a human homologue of Drosophila crumbs cause retinitis pigmentosa (RP12)

Retinitis pigmentosa (RP) comprises a clinically and genetically heterogeneous group of diseases that afflicts approximately 1.5 million people worldwide. Affected individuals suffer from a progressive degeneration of the photoreceptors, eventually resulting in severe visual impairment. To isolate candidate genes for chorioretinal diseases, we cloned cDNAs specifically or preferentially expressed in the human retina and the retinal pigment epithelium (RPE) through a novel suppression subtractive hybridization (SSH) method. One of these cDNAs (RET3C11) mapped to chromosome 1q31-q32.1, a region harbouring a gene involved in a severe form of autosomal recessive RP characterized by a typical preservation of the para-arteriolar RPE (RP12; ref. 3). The full-length cDNA encodes an extracellular protein with 19 EGF-like domains, 3 laminin A G-like domains and a C-type lectin domain. This protein is homologous to the Drosophila melanogaster protein crumbs (CRB), and denoted CRB1 (crumbs homologue 1). In ten unrelated RP patients with preserved para-arteriolar RPE, we identified a homozygous AluY insertion disrupting the ORF, five homozygous missense mutations and four compound heterozygous mutations in CRB1. The similarity to CRB suggests a role for CRB1 in cell-cell interaction and possibly in the maintenance of cell polarity in the retina. The distinct RPE abnormalities observed in RP12 patients suggest that CRB1 mutations trigger a novel mechanism of photoreceptor degeneration.

Photorefractive keratectomy with an ablatable mask for myopic astigmatism

PURPOSE

To evaluate efficacy, safety, and stability of photoastigmatic keratectomy (PARK) carried out with a Summit Apex Plus laser using an ablatable mask.

METHODS

Forty-one eyes of 41 patients with myopic astigmatism with follow-up of 12 months were evaluated. Treatment efficacy was compared in groups with high (>6.00 D) versus low (< or =6.00 D) preoperative spherical equivalent subjective manifest refraction, in groups with high (>2.00 D) versus low (< or =2.00 D) preoperative cylindrical component and in groups divided according to preoperative axis of cylinder.

RESULTS

At 12 months after surgery, mean spherical equivalent manifest refraction in all 41 eyes was -0.30 +/- 0.90 D. Mean cylinder component was 0.60 +/- 0.70 D. Mean reduction in astigmatic component was 67 +/- 47%. Uncorrected visual acuity of 0.5 or more was achieved in 79% of eyes; 71% of eyes achieved 0.8 or more. At 1 month after surgery, 49% of eyes had a loss of 2 or more lines of spectacle-corrected visual acuity. This loss was restored at 12 months. No statistically significant differences were found between the different subgroups.

CONCLUSION

Photoastigmatic keratectomy with ablatable mask gives satisfactory results. No relation in efficacy was found when taking into account the amount of preoperative spherical component, the cylindrical component, or the cylinder axis direction.

Predictive value of pattern VEP, pattern ERG and hole size in macular hole surgery

OBJECTIVE

To describe pattern-reversal visual evoked response (PRVEP) and pattern electroretinogram (PERG) parameters in eyes with macular hole and their value for predicting postoperative visual outcome.

METHODS

Prospectively we studied 27 eyes (27 patients) with a full-thickness macular hole. Preoperatively the hole and rim were measured and the PRVEP and PERG were recorded. The preoperative parameters were correlated with postoperative visual outcome.

RESULTS

The macular hole was closed in 26 of 27 eyes. Sixteen eyes (59%) had an increase in visual acuity (VA) of two lines or more, 10 eyes (37%) remained within one line of preoperative VA and 1 eye (4%) had a decrease in VA of two lines. Duration of symptoms was negatively correlated with preoperative VA (R=-0.547, P=0.0038) and postoperative VA (R=-0.519, P=0.0065) and positively correlated with hole area (R=0.533, P=0.0061) and rim area R=0.633, P=0.0009). Only the PRVEP P100 latency of the 10' check size and the PERG N35 latency were significantly associated with visual outcome (P=0.022 and P=0.042 respectively).

CONCLUSIONS

There was no association of either hole or rim size with postoperative visual outcome. Preoperative electrophysiology, however, is useful as a prognostic tool. Utilization is limited to the use of latency parameters of the response and is dependent on the check size of the stimulus.

Isolation and mapping of novel candidate genes for retinal disorders using suppression subtractive hybridization

We have constructed human cDNA libraries enriched for retina- and retinal pigment epithelium (RPE)/choroid-specific cDNAs through suppression subtractive hybridization. The sequence of 314 cDNAs from the retina enriched library and 126 cDNAs from the RPE/choroid enriched library was analyzed. Based on the absence of a database match, 25% of the retina cDNA clones and 16% of the RPE/choroid cDNA clones are novel cDNAs. The expression profiles of 86 retina and 21 RPE/choroid cDNAs were determined by a semiquantitative reverse transcription polymerase chain reaction technique. Thirty-three cDNAs were expressed exclusively or most prominently in retina or RPE/choroid. These cDNAs were mapped in the human genome by radiation hybrid mapping. Eleven cDNAs colocalized with loci involved in retinal disorders. One cDNA mapped in a 1.5-megabase critical region for autosomal recessive retinitis pigmentosa (RP12). Another cDNA was assigned to the 7.7-cM RP17 linkage interval. Seven cDNAs colocalized with four loci involved in Bardet-Biedl syndrome.

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.

Peripheral retinal nonperfusion associated with essential thrombocytosis

PURPOSE

To describe a patient with retinal complications of essential thrombocytosis.

METHOD

Case report. A 24-year-old man with acute vitreous hemorrhage of the right eye underwent ocular and systemic examinations to elucidate the origin of this condition.

RESULTS

Fluorescein angiography of the right eye showed an avascular peripheral retina with marked capillary nonperfusion, arteriovenous anastomosis, and sea fan neovascularization. Blood studies showed thrombocytosis without other associated systemic diseases. The peripheral retinal capillary nonperfusion and sea fan neovascularization were treated with dye-laser photocoagulation, and aspirin, 80 mg daily, was given for systemic treatment.

CONCLUSIONS

In our patient, the avascular retina was associated with essential thrombocytosis, which may cause an avascular peripheral retina with neovascularization and vitreous hemorrhage in otherwise healthy persons.

Treatment of hyperopia with contact Ho:YAG laser thermal keratoplasty

PURPOSE

To evaluate the effectiveness, safety, and stability of contact Ho:YAG laser thermal keratoplasty for low to moderate hyperopia.

METHODS

Fifty-five hyperopic eyes of 39 patients were treated with a Technomed contact Ho:YAG laser; 23 eyes were treated a second time. Treatment parameters were 1 octagonal ring of 8 spots with a treatment diameter of 6 mm, 7 mm, or 8 mm. Efficacy of the Ho:YAG laser treatment was evaluated after 6 months, comparing 3 treatment zone diameters. Stability and efficacy after 12 months was evaluated comparing 7-mm and 8-mm treatment zone diameters.

RESULTS

Mean reduction of spherical equivalent refraction after 6 months was not statistically significantly different between the 6-mm or 7-mm diameter zones: 1.42 (+/- 1.30) D versus 2.22 (+/- 0.44) D. An 8-mm diameter treatment zone was significantly less effective, 1.12 (+/- 0.47) D. Longer follow-up did not show stability: mean reduction of spherical equivalent manifest refraction was 1.58 (+/- 0.45) D for the 7-mm diameter treatment zone and 0.82 (+/- 0.61) D for the 8-mm diameter treatment zone after approximately 12 months. Retreatment had a limited additive effect. No clinically significant loss of spectacle-corrected visual acuity was reported. No eyes lost more than 1 line of visual acuity.

CONCLUSION

Contact Ho:YAG laser thermal keratoplasty corrected hyperopia up to 2.50 D, but predictability was poor and a regression of initial effect occurred. Instability of refraction persisted to 1 year after surgery.

The visual cycle retinol dehydrogenase: possible involvement in the 9-cis retinoic acid biosynthetic pathway

The 11-cis-retinol dehydrogenase (11-cis-RoDH) gene encodes the short-chain alcohol dehydrogenase responsible for 11-cis-retinol oxidation in the visual cycle. The structure of the murine 11-cis-RoDH gene was used to reinvestigate its transcription pattern. An 11-cis-RoDH gene transcript was detected in several non-ocular tissues. The question regarding the substrate specificity of the enzyme was therefore addressed. Recombinant 11-cis-RoDH was found capable of oxidizing and reducing 9-cis-, 11-cis- and 13-cis-isomers of retinol and retinaldehyde, respectively. Dodecyl-beta-1-maltoside used to solubilize the enzyme was found to affect the substrate specificity. This is the first report on a visual cycle enzyme also present in non-retinal ocular and non-ocular tissues. A possible role in addition to its role in the visual cycle is being discussed.

A randomized controlled clinical trial on the efficacy of radiation therapy in the control of subfoveal choroidal neovascularization in age-related macular degeneration: radiation versus observation

BACKGROUND

The results of several pilot studies concerning radiation therapy for age-related subfoveal choroidal neovascularization (CNV) have been published recently. Although positive treatment results have been described, it is not known whether this therapy alters the natural course of eyes with neovascular age-related macular degeneration (AMD). A randomized controlled clinical trial was conducted in which radiation therapy was compared with observation in patients with subfoveal neovascular AMD.

METHODS

Seventy-four patients with a recent drop in central vision due to subfoveal age-related CNV were randomized to either radiation treatment or observation. Patients with either classic, occult or mixed type CNV were included. Eyes in the treatment group received a radiation dose of 24 Gy in four fractions of 6 Gy. Evaluation of data concerning visual acuity (VA) and fluorescein angiography occurred at 3, 6 and 12 months after inclusion.

RESULTS

At 12 months of follow-up 52.2% of the observation group versus 32.0% of the irradiation group had lost 3 or more lines of VA (P = 0.03, log rank test). More severe visual decline, 6 lines or more, was observed in 40.9% of the observation versus 8.8% in the irradiation group (P = 0.002 using log rank test). At 12 months 39.6% of the observation group and 20.0% of the treatment group had VA of less than 0.1 (P = 0.08, log rank test). The size of the CNV membrane doubled in 25.2% of eyes in the observation group versus 20.0% in the treatment group at least 12 months (P = 0.5, log rank test). No side effects were observed.

CONCLUSION

Preservation of VA was significantly better in the treatment group compared with the control group at 12 months. Nevertheless we noted a drop in central vision of 3 or more lines in a substantial proportion of the treatment group. Radiation therapy does not prevent visual loss in all patients with age-related subfoveal CNV, and whether the treatment benefit at 12 months will persist has to be awaited.

Autosomal recessive retinitis pigmentosa and cone-rod dystrophy caused by splice site mutations in the Stargardt's disease gene ABCR

Ophthalmological and molecular genetic studies were performed in a consanguineous family with individuals showing either retinitis pigmentosa (RP) or cone-rod dystrophy (CRD). Assuming pseudodominant (recessive) inheritance of allelic defects, linkage analysis positioned the causal gene at 1p21-p13 (lod score 4.22), a genomic segment known to harbor the ABCR gene involved in Stargardt's disease (STGD) and age-related macular degeneration (AMD). We completed the exon-intron structure of the ABCR gene and detected a severe homozygous 5[prime] splice site mutation, IVS30+1G->T, in the four RP patients. The five CRD patients in this family are compound heterozygotes for the IVS30+1G->T mutation and a 5[prime] splice site mutation in intron 40 (IVS40+5G->A). Both splice site mutations were found heterozygously in two unrelated STGD patients, but not in 100 control individuals. In these patients the second mutation was either a missense mutation or unknown. Since thus far no STGD patients have been reported to carry two ABCR null alleles and taking into account that the RP phenotype is more severe than the STGD phenotype, we hypothesize that the intron 30 splice site mutation represents a true null allele. Since the intron 30 mutation is found heterozygously in the CRD patients, the IVS40+5G->A mutation probably renders the exon 40 5[prime] splice site partially functional. These results show that mutations in the ABCR gene not only result in STGD and AMD, but can also cause autosomal recessive RP and CRD. Since the heterozygote frequency for ABCR mutations is estimated at 0.02, mutations in ABCR might be an important cause of autosomal recessive and sporadic forms of RP and CRD.

Cloning and structural analysis of the murine GCN5L1 gene

We recently cloned the murine 11-cis retinol dehydrogenase gene. A second gene, the murine GCN5L1 gene, was found to be situated upstream of the murine 11-cis retinol dehydrogenase gene. We have isolated and sequenced the complete coding sequence of the murine GCN5L1 gene. The distance between the 3'-end of the murine GCN5L1 gene and the 5'-end of the 11-cis retinol dehydrogenase gene is only 776 nt. The murine GCNSL1 gene consists of four exons encompassing approximately 3.5 kb of genomic DNA. Intron/exon splice sites conform to the GT/AG rule. The open reading frame consists of 375 nucleotides encoding a 14 kDa protein. The murine GCN5L1, like the human GCN5L1 protein, displays weak homology (27%) to yeast GCN5. The distance between the murine, human and bovine GCN5L1 and 11-cis retinol dehydrogenase genes appeared to be conserved.

Reticular dystrophy of the retinal pigment epithelium and choroidal neovascularization. A fluorescein and ICGV study

We report the clinical history of 2 patients affected with reticular dystrophy of the retinal pigment epithelium and central choroidal neovascularization. With time, spontaneous reduction of the subretinal fluid associated with consequent improvement of the visual acuity has been noted in our first case. The second patient showed a stable fibrotic subfoveal choroidal neovascularization. Conventional fluorescein angiography and indocyanine green videoangiography findings are illustrated. The differential diagnosis between other reticular pigmented lesions often associated with choroidal neovascularization is discussed.

Central areolar choroidal dystrophy and slowly progressive sensorineural hearing loss

Central areolar choroidal dystrophy (CACD) is a rare hereditary disorder leading to a central scotoma in middle-aged patients. Two cases of CACD in association with perceptive hearing loss are discussed. A 62-year-old male and a 51-year-old female patient complained of visual deterioration and subsequent hearing loss over several years. In addition to routine ophthalmic and otorhinolaryngological examination both patients underwent fluorescein angiography, (electro)physiological examination and audiometry examination. A demarcated area of atrophy of pigment epithelium and choriocapillaris was found in both patients. A slowly progressive sensorineural hearing loss after adolescence was found in both patients. The hearing deteriorated to such a level at middle age that hearing aids were necessary. These two cases show that CACD may be associated with perceptive hearing loss.

Delay in diagnosis of homocystinuria: retrospective study of consecutive patients

OBJECTIVE

To assess the causes for delay in the diagnosis of homocystinuria.

DESIGN

Clinical and laboratory data were collected from patients diagnosed as having homocystinuria due to cystathionine synthase deficiency, with special reference to the ages at which the patients had their first major signs of the disease, ectopia lentis was established, and homocystinuria was diagnosed.

SETTING

University hospital in the Netherlands.

SUBJECTS

34 patients (18 males) in whom homocystinuria due to cystathionine synthase deficiency was diagnosed in the period 1970-94.

RESULTS

Among 34 consecutively detected homocystinuria patients the mean age at diagnosis of homocystinuria was 24 (range 1-61) years. Despite frequent ocular manifestations, serious complications in the vascular, skeletal, and central nervous systems, and repeated examinations performed in these patients by clinicians of various disciplines, there was a mean delay of 11 (0-43) years between the first major signs of the disease (at mean age 13 (1-40) years) and the ultimate diagnosis of homocystinuria. Even when ectopia lentis was diagnosed (in 26 (76%) patients, mean age 18 (1-50) years), this did not lead to adequate biochemical analysis for homocystinuria at the time of detection, causing a mean diagnostic delay of 8 (0-24) years in these patients.

CONCLUSIONS

Three factors should have precipitated the diagnosis of homocystinuria: early recognition that unusual myopia (high, very high, abnormal progressive, or at young age) was caused by subluxation of the ocular lenses; awareness that the occurrence of myopia combined with systemic complications ("myopia plus") might be due to homocystinuria; and appropriate biochemical investigations carried out in patients with ectopia lentis and in their siblings.

Genetic fine mapping of the gene for recessive Stargardt disease

Stargardt disease (STGD) is one of the most frequent causes of macular degeneration in childhood. Linkage analysis in families with recessive STGD has recently shown genetic homogeneity and a location of the underlying gene at 1p22-p21 in a 4-cM interval. Haplotype analysis in seven Dutch STGD families with 11 highly polymorphic markers spanning the critical region has enabled us to refine the location of the underlying gene to a 2-cM region flanked by the loci D1S406 and D1S236. We have identified one 45-year-old nonpenetrant individual who carries two disease alleles. In another family, an affected individual inherited the paternal but not the maternal disease chromosome, suggesting genetic heterogeneity or a different mechanism leading to the disease in this family.