Molecular genetic heterogeneity in autosomal dominant drusen

OBJECTIVE

Autosomal dominant drusen is of particular interest because of its phenotypic similarity to age related macular degeneration. Currently, mutation R345W of EFEMP1 and, in a single pedigree, linkage to chromosome 6q14 have been causally related to the disease. We proposed to investigate and quantify the roles of EFEMP1 and the 6q14 locus in dominant drusen patients from the UK and USA.

DESIGN

Molecular genetic analysis.

PARTICIPANTS

Ten unrelated families and 17 young drusen patients.

MAIN OUTCOME MEASURES

Exons 1 and 2 of EFEMP1 were characterised by 5' rapid amplification of cDNA ends and direct sequencing. Exons 1-12 of EFEMP1 were then investigated for mutation by direct sequencing. A HpaII restriction digest test was constructed to detect the EFEMP1 R345W mutation. Marker loci spanning the two dominant drusen linked loci were used to generate haplotype data.

RESULTS

Only seven of the 10 families (70%) and one of the 17 sporadic patients (6%) had the R345W mutation. The HpaII restriction digest test was found to be a reliable and quick method for detecting this. No other exonic or splice site mutation was identified. Of the three families without EFEMP1 mutation, two were linked to the 2p16 region.

CONCLUSIONS

EFEMP1 R345W accounts for only a proportion of the dominant drusen phenotype. Importantly, other families linked to chromosome 2p16 raise the possibility of EFEMP1 promoter sequence mutation or a second dominant drusen gene at this locus. Preliminary haplotype data suggest that the disease gene at the 6q14 locus is responsible for only a minority of dominant drusen cases.

Spectrum of mutations in USH2A in British patients with Usher syndrome type II

Usher syndrome (USH) is a combination of a progressive pigmentary retinopathy, indistinguishable from retinitis pigmentosa, and some degree of sensorineural hearing loss. USH can be subdivided in Usher type I (USHI), type II (USHII) and type III (USHIII), all of which are inherited as autosomal recessive traits. The three subtypes are genetically heterogeneous, with six loci so far identified for USHI, three for USHII and only one for USHIII. Mutations in a novel gene, USH2A, encoding the protein usherin, have recently been shown to be associated with USHII. The gene encodes a protein with partial sequence homology to both laminin epidermal growth factor and fibronectin motifs. We analysed 35 British and one Pakistani Usher type II families with at least one affected member, for sequence changes in the 20 translated exons of the USH2A gene, using heteroduplex analysis and sequencing. Probable disease-causing mutations in USH2A were identified in 15 of 36 (41.7%) Usher II families. The most frequently encountered mutation (11/15 families or 11/18 mutated alleles) was del2299G in exon 13, resulting in a frameshift and premature stop codon. Other mutations include insertions and point mutations, of which two are previously unreported. Five different polymorphisms were also detected. Our results indicate that mutations in this gene are responsible for disease in a large proportion of British Usher type II patients. Moreover, if screening for mutations in USH2A is considered, it is sensible to screen for the del2299G mutation first.

Phenotypic subtypes of Stargardt macular dystrophy-fundus flavimaculatus

OBJECTIVE

To determine if phenotypic subtypes exist in Stargardt macular dystrophy-fundus flavimaculatus (SMD-FFM).

METHODS

A cross-sectional study of 63 patients with autosomal recessive SMD-FFM was undertaken. The age of onset, duration of symptoms, visual acuity, and clinical features on fundus examination, color fundus photographs, and fundus autofluorescence images were recorded. Electrophysiological tests, including pattern, focal, and full-field electroretinogram (ERG), electro-oculogram, and color-contrast sensitivity measurement, were also performed.

RESULTS

Based on electrophysiological attributes (ERG), patients with SMD-FFM could be classified into 3 groups. In group 1, there was severe pattern ERG abnormality with normal scotopic and full-field ERGs. In group 2, there was additional loss of photopic function, and in group 3, there was loss of both photopic and scotopic function. Differences in scotopic or photopic function among groups were not explained on the basis of differences in age of onset or duration of disease.

CONCLUSIONS

Patients with SMD-FFM can be classified into 3 groups based on the absence or presence of generalized loss of either photopic or photopic and scotopic function. It appears that these 3 groups may represent distinct phenotypic subtypes in SMD-FFM.

Ophthalmologists' perspective

Molecular biology has significantly contributed to our understanding of inherited retinal disease, in particular to that of monogenic disorders. The discovery of the responsible gene, the elucidation of its function, and the increasing understanding of the pathogenesis of inherited retinal disorders is both exciting and important. From the clinician's point of view, this new information is helpful in diagnosis and prognosis, and may ultimately yield benefits in the form of therapy. This chapter deals with the advances made in the field of molecular biology as it pertains to inherited retinal disorders from the perspective of the clinician. Identification of specific loci, genes, and causative mutations have led to reclassification and reordering of the preexisting nosological classification. Progression in the understanding of the function of the relevant protein, and putative metabolic disturbance caused by the mutation at the cellular level, is continuing and therapies developed to address these abnormalities are currently undergoing evaluation.

Autosomal dominant cone and cone-rod dystrophy with mutations in the guanylate cyclase activator 1A gene-encoding guanylate cyclase activating protein-1

OBJECTIVE

To describe the phenotype in 3 families with dominantly inherited cone and cone-rod dystrophy with mutations in guanylate cyclase activator 1A (GUCA1A), the gene-encoding guanylate cyclase activator protein-1 (GCAP-1).

METHODS

Phenotypic characterization with psychophysical and electrophysiological evaluation and confocal laser scanning ophthalmoscopy was performed in 2 families with a Tyr99Cys mutation and 1 family with a Pro50Leu mutation. Haplotype analysis was performed in the families with Tyr99Cys mutation.

RESULTS

The families with a Y99C mutation were shown to be ancestrally related. Decreased visual acuity and loss of color vision occurred after the age of 20 years, followed by progressive atrophy of the central 5 degrees to 10 degrees. Electrophysiological testing revealed generalized loss of cone function, with preservation of rod function. Abnormal rod and cone sensitivities were confined to the central 5 degrees to 10 degrees. Confocal laser scanning ophthalmoscopy imaging showed abnormalities of autofluorescence in early disease. Subjects with a Pro50Leu mutation demonstrated marked variability in expressivity from minimal abnormalities of macular function to cone-rod dystrophy.

CONCLUSIONS

The phenotype associated with the Y99C mutation in GUCA1A is distinctive, with little variation in expression. By contrast, that associated with the P50L mutation demonstrates variable expressivity.

CLINICAL RELEVANCE

Phenotype-genotype correlation in these 2 mutations demonstrates 2 different phenotypes.

Influence of laser photocoagulation on choroidal capillary cytoarchitecture

AIM

To identify if laser photocoagulation induces morphological changes specifically related to the choroidal capillary endothelial processes that protrude into Bruch's membrane.

METHODS

Two human eyes and one adult macaque monkey eye received retinal laser photocoagulation that was just suprathreshold, before enucleation or exenteration. They were examined by electron microscopy to determine the length of the endothelial processes emanating from the choroidal capillaries in the region around the laser burn. One human and two monkey untreated eyes were used for comparison.

RESULTS

In human eyes, there was no increase in the number of processes 15 hours after laser treatment but at 5 days the processes were more numerous and longer within 400-500 microm of the burn than in the untreated half of the same eye. The processes were longer 9 days after photocoagulation in the monkey, when compared with untreated monkeys, and some breached the elastic lamina, a phenomenon not seen in the untreated eyes. Qualitative differences were also noted in the endothelial cell processes following photocoagulation. Neovascularisation was not observed.

CONCLUSIONS

Protrusion of choroidal endothelial cell processes into Bruch's membrane is a normal anatomical feature but the number, length, and morphology of the processes change following mild photocoagulation. It is plausible that these processes may play a part in the clearance of debris from Bruch's membrane, and represent an early stage of angiogenesis. If the latter is true prophylactic laser photocoagulation at just suprathreshold levels may carry a risk of inducing choroidal neovascularisation.

Ultrastructural changes associated with accumulation of inclusion bodies in rat retinal pigment epithelium

PURPOSE

To determine the structural changes in the retinal pigment epithelium (RPE) and neighboring structures induced by intravitreal injection of a lysosomal protease inhibitor.

METHODS

Eleven-week-old Sprague-Dawley rats were injected with 5 microliter of a lysosomal protease inhibitor, E-64 (2.22 microM), intravitreally once and killed at 24 hours, 48 hours, or 7 days later. Others received two or three injections at 48-hour intervals or three daily injections, and killed at 1, 4, and 7 days after the last injection. Eyes were enucleated and retinal tissues were processed for light and electron microscopy.

RESULTS

A single injection of E-64 caused only a transient accumulation of phagosome-like and phagolysosome-like inclusion bodies in the RPE. By contrast, repeated injection caused progressive accumulation of these inclusions followed by altered RPE cell conformation, and changes in organelles such as loss of smooth endoplasmic reticulum (SER). This was accompanied by shortening and loss of photoreceptor outer segments without prior dysmorphic changes, alteration of choroidal capillaries, and invasion of Bruch's membrane by fibroblasts and pericytes. Intravitreal injection of vehicle as control induced no structural changes.

CONCLUSIONS

E-64 treatment induced structural changes in the outer retina. The causal relationship between accumulation of inclusions in RPE and changes in other subcellular organelles and neighboring cells systems is not clear. However, there are possible explanations: physical disturbance of organelles, particularly SER by inclusions; cellular damage by consequent upon accumulation of A2-E; or, shortage of recycled material due to reduced degradation of phagosomes.

RP1 protein truncating mutations predominate at the RP1 adRP locus

PURPOSE

Recent reports have shown that the autosomal dominant retinitis pigmentosa (adRP) phenotype linked to the pericentric region of chromosome 8 is associated with mutations in a gene designated RP1. Screening of the whole gene in a large cohort of patients has not been undertaken to date. To assess the involvement and character of RP1 mutations in adRP, the gene was screened in a panel of 266 unrelated patients of British origin and a Pakistani family linked to this locus.

METHODS

Patients exhibiting the adRP phenotype were screened for mutations in the four exons of the RP1 gene by heteroduplex analysis and direct sequencing. Linkage of the Pakistani family was achieved using microsatellite markers. Polymerase chain reaction (PCR) products were separated by nondenaturing polyacrylamide gel electrophoresis. Alleles were assigned to individuals, which allowed calculation of LOD scores. Microsatellite marker haplotyping was used to determine ancestry of patients carrying the same mutation.

RESULTS

In the 266 British patients and 1 Pakistani family analyzed, 21 loss-of-function mutations and 7 amino acid substitutions were identified, some of which may also be disease-causing. The mutations, many of which were deletion or insertion events, were clustered in the 5' end of exon 4. Most mutations resulted in a premature termination codon in the mRNA. Haplotype analysis of nine patients carrying an R677X mutation suggested that these patients are not ancestrally related.

CONCLUSIONS

RP1 mutations account for 8% to 10% of the mutations in our cohort of British patients. The most common disease-causing mechanism is deduced to be one involving the presence of a truncated protein. Mutations in RP1 have now been described in adRP patients of four ethnically diverse populations. The different disease haplotype seen in the nine patients carrying the same mutation suggests that this mutation has arisen independently many times, possibly due to a mutation hot spot in this part of the gene.

NRL S50T mutation and the importance of 'founder effects' in inherited retinal dystrophies

The aim of this work was to identify NRL mutations in a panel of 200 autosomal dominant retinitis pigmentosa (adRP) families. All samples were subjected to heteroduplex analysis of the three exons of the NRL gene, and HphI restriction digest analysis of exon 2 (to identify the S50T mutation). Families found to have the S50T mutation, and six additional larger pedigrees (which had previously been excluded from the other nine adRP loci) underwent linkage analysis using polymorphic markers located in the region of 14q11. HphI restriction analysis followed by direct sequencing of the amplified NRL exon 2 product demonstrated the presence of the NRL S50T sequence change in three adRP families. Comparison of marker haplotypes in affected individuals from these families with those of affected members of the original 14q11 linked family revealed a common disease haplotype for markers within the adRP locus. Recombination events observed in these families define an adRP critical interval of 14.9 cM between D13S72 and D14S1041. Linkage analysis enabled all six of the larger adRP pedigrees to be excluded from the 14q11 locus. The NRL S50T mutation represents another example of a 'founder effect' in a dominantly inherited retinal dystrophy. Identification of such 'founder effects' may greatly simplify diagnostic genetic screening and lead to better prognostic counselling. The exclusion of several adRP families from all ten adRP loci indicates that at least one further adRP locus remains to be found.

Mutational hot spot within a new RPGR exon in X-linked retinitis pigmentosa

The gene RPGR was previously identified in the RP3 region of Xp21.1 and shown to be mutated in 10-20% of patients with the progressive retinal degeneration X-linked retinitis pigmentosa (XLRP). The mutations predominantly affected a domain homologous to RCC1, a guanine nucleotide exchange factor for the small GTPase Ran, although they were present in fewer than the 70-75% of XLRP patients predicted from linkage studies. Mutations in the RP2 locus at Xp11.3 were found in a further 10-20% of XLRP patients, as predicted from linkage studies. Because the mutations in the remainder of the XLRP patients may reside in undiscovered exons of RPGR, we sequenced a 172-kb region containing the entire gene. Analysis of the sequence disclosed a new 3' terminal exon that was mutated in 60% of XLRP patients examined. This exon encodes 567 amino acids, with a repetitive domain rich in glutamic acid residues. The sequence is conserved in the mouse, bovine and Fugu rubripes genes. It is preferentially expressed in mouse and bovine retina, further supporting its importance for retinal function. Our results suggest that mutations in RPGR are the only cause of RP3 type XLRP and account for the disease in over 70% of XLRP patients and an estimated 11% of all retinitis pigmentosa patients.

Familial cavernous hemangioma: An expanding ocular spectrum

OBJECTIVE

To describe the clinical and genetic findings in a family with multiple cases of cavernous hemangiomas.

DESIGN

Investigational clinical and genetic study in which 3 generations of a family consisting of 12 members were screened with magnetic resonance brain imaging, dilated ophthalmoscopic examination, and cutaneous survey coupled with linkage analysis to determine affected individuals and to better define manifestations of this neuro-oculo-cutaneous syndrome.

RESULTS

The proband had multiple cerebral cavernous hemangiomas and a choroidal hemangioma. Her son was found to harbor a retinal cavernous hemangioma. The proband's sister manifested a cerebral cavernous hemangioma, cutaneous hemangiomas, and a presumed choroidal hemangioma; her daughter demonstrated radiological findings suggestive of a cerebral cavernous hemangioma. The father of the proband demonstrated multiple, cutaneous hemangiomas. The remaining family members were free of lesions. The 7q locus could not be excluded as harboring the causative gene.

CONCLUSIONS

This family may have a dominantly inherited neuro-oculo-cutaneous condition of cavernous hemangiomas with variable expressivity. The presence of choroidal hemangiomas in this phacomatosis has not been described previously to our knowledge.

CLINICAL RELEVANCE

The presence of either retinal cavernous or choroidal hemangioma should alert the physician to search for features suggestive of systemic and familial involvement; either lesion may constitute the ocular component of the neuro-oculo-cutaneous phacomatosis, sometimes referred to as cavernoma multiplex. Arch Ophthalmol. 2000;118:969-973

Quantitative evaluation of fundus autofluorescence imaged "in vivo" in eyes with retinal disease

AIM

To describe a new method of evaluating the topographic distribution of fundus autofluorescence in eyes with retinal disease.

METHODS

Images of fundus autofluorescence were obtained in five patients and 34 normal volunteers using a confocal scanning laser ophthalmoscope (cSLO). To evaluate the topographic distribution of fundus autofluorescence throughout the posterior pole a rectangular box, 10 x 750 pixels, was used as the area of analysis. The box was placed, horizontally, across the macular region. The intensity of fundus autofluorescence of each pixel within the rectangular box was plotted against its degree of eccentricity. Profiles of fundus autofluorescence from patients were compared with those obtained from the age matched control group and with cSLO images.

RESULTS

Profiles of fundus autofluorescence appeared to represent the topographic distribution of fundus autofluorescence throughout the posterior pole appreciated in the cSLO images, and allowed rapid identification and quantification of areas of increased or decreased fundus autofluorescence.

CONCLUSIONS

Fundus autofluorescence profiles appear to be useful to study the spatial distribution of fundus autofluorescence in eyes with retinal disease.

Novel frameshift mutations in the RP2 gene and polymorphic variants

Mutations in the RP2 gene located on Xp11.23 are associated with X-linked retinitis pigmentosa (XLRP), a severe form of progressive retinal degeneration which leads to complete loss of vision in affected males. To date, 14 different mutations in the RP2 gene have been reported to cause XLRP, the majority of which lead to a coding frameshift within the gene and predicted truncation of the protein product. We here report two novel frameshift mutations in RP2 identified in XLRP families by PCR-SSCP and direct sequencing, namely 723delT and 796-799del. Four single nucleotide polymorphisms (SNPs) within the coding region of RP2 are also described (105A>T, 597T>C, 844C>T, 1012G>T), the first polymorphisms to be reported within this gene of unknown function, two of which alter the amino acid sequence. The current study extends the XLRP mutation profile of RP2 and highlights non-pathogenic coding sequence variations which may facilitate both functional studies of the gene and analysis of intragenic allelic contribution to the phenotype.

[Antiretinal antibodies associated with cystoid macular edema]

AIM

Recently, anti-Enolase and anti-carbonic anhydrase antibodies have been observed in over 60% of patients with retinitis pigmentosa (RP) and cystoid macular oedema (CME). We investigated the presence of these antibodies in a series of patients with CME due to different pathologies.

METHODS

In 10 patients with CME serum antibodies against Carbonic anhydrase (CA) II (30 kD) and Enolase (46 kD) were sought using Western Blots, Dot Blots as well as ELISA.

RESULTS

Western and dot blotting showed anti-CA II antibodies in all and anti-Enolase antibodies in six of the 10 patients. The average titer measured with ELISA was 0.9 +/- 0.08 OD Units (0.35-1.4) with a dilution of 1:400.

CONCLUSION

The presence of anti-retinal antibodies in the serum of all patients confirms the high prevalence of these antibodies in patients with CME. This may suggest that a dysfunction of CA and enolase activity in the retinal pigment epithelium may lie at the root of oedema formation, whereas other mechanisms may be responsible in the absence of these antibodies.

[Retinal vasculopathy associated with Berger's IgA nephropathy]

AIM

Ophthalmological complications associated with Berger's IgA nephropathy comprise scleritis, episcleritis, keratoconjunctivitis as well as anterior uveitis. We present a new association of IgA nephropathy with a retinal vasculopathy.

METHODS

Presentation of two clinical cases.

RESULTS

Two patients presented with hematuria and epistaxis associated with a retinal vasculopathy characterised by teleangiectasies, capillary occlusion with retinal hemorrhages, neovascularisations and macular edema with decreased visual acuity. Fluorescein angiography showed zones of non-perfusion as well as vasculitic changes. A general medical exam revealed a normal arterial pressure but a slightly elevated creatinine. Immunological investigations for the presence of antibodies showed no positive results. Renal biopsy demonstrated mesangial proliferations with diffuse deposits of IgA. Over the course of a 2 year follow-up some of the retinal changes regressed under treatment with cortisone and visual acuity returned to normal. The teleangiectasies showed no progression.

CONCLUSION

Berger's IgA nephropathy can be associated with a retinal vasculopathy which may be due to local deposition of IgA immune complexes in the retinal vessels.

Polypoidal choroidal vasculopathy in exudative and haemorrhagic pigment epithelial detachments

AIMS

To determine the prevalence of polypoidal choroidopathy in consecutive patients presenting with large haemorrhagic and exudative neurosensory retinal and retinal pigment epithelial detachments (PEDs) of over 2 mm in diameter in the absence of drusen.

METHODS

40 patients were identified over a 5 month period of which 29 had haemorrhagic detachments, and 11 had purely exudative detachments. All had indocyanine green (ICG) angiography, and the presence was sought of large blood vessels in the choroid associated with localised dilated terminals that filled slowly and leaked ICG.

RESULTS

In 34 cases (85%) there was an appearance consistent with previous descriptions of idiopathic polypoidal choroidal vasculopathy. Of the six without polypoidal lesions the disorder was attributed to choroidal neovascularisation in four, chorioretinitis in one, and a fibrovascular PED in one. Of those with polypoidal lesions 20 (65%) were female, the mean age was 65.4 years (range 44-88), and 25 (74%) were white, seven (20%) black, and two (6%) east Asian. Eight had a history of hypertension. Visual acuity varied from 6/6 to counting fingers in the involved eye (mean 6/24). Bilateral polypoidal choroidal lesions were demonstrated in 16 patients (47%). The predominant location for these lesions was the macular region in 23 patients (68%). Polypoidal vasculopathy was found in 16 patients (47%) who had a previous diagnosis of age related macular disease (AMD). No patients had evidence of intraocular inflammation.

CONCLUSIONS

In a largely white patient population a high proportion of patients with haemorrhagic and exudative PEDs has evidence of polypoidal lesions on ICG angiography.

Novel mutations of the RPGR gene in RP3 families

X-linked retinitis pigmentosa is a severe retinal degeneration characterized by night blindness and visual field constriction, leading to complete blindness within the third decade of life. Mutations in the RPGR gene (retinitis pigmentosa GTPase regulator), located on Xp21.1 in the RP3 region, have been associated with an RP phenotype. Further to our previous mutation screening of RPGR in families segregating with the RP3 locus, we have expanded this study to include other 8 RP3 pedigrees. Here we report the results of this expanded study and the identification of five mutations in RPGR, four of which are novel (IVS6+5 G>A, 950-951delAA, 963 T>C, EX8del) and one of which occurs in the donor splice site of intron 1 (IVS1+1 G>A). These findings bring the proportion of "RP3 genotypes" with a mutation in this gene to 27% (10/37). Hum Mutat 15:386, 2000.

TIMP-3, collagen, and elastin immunohistochemistry and histopathology of Sorsby's fundus dystrophy

PURPOSE

Mutations in the tissue inhibitor of metalloproteinases-3 (TIMP-3) gene have previously been identified in patients with Sorsby's fundus dystrophy (SFD). We evaluated the ocular distribution of TIMP-3 and other extracellular constituents in SFD.

METHODS

The eyes of an SFD donor with a confirmed TIMP-3 mutation were examined using histologic techniques demonstrating connective tissue, calcium, and lipid. Immunohistochemical analyses were performed using antibodies against TIMP-3, collagen type IV, V, and VI, laminin, fibronectin, elastin, and fibrillin. Electron microscopy also was used.

RESULTS

A subretinal pigment epithelium (sub-RPE) deposit similar to that previously described was seen. A morphologically similar but different deposit was present internal to the nonpigmented ciliary epithelium (NPCE). Both deposits contained collagens, elastin, glycosaminoglycans, lipids, and calcium. Immunolabeling of TIMP-3 was found in the basement membrane of the NPCE, Bruch's membrane, and choroidal vessels in normal control subjects. In SFD, immunolabeling of TIMP-3 also was present in the sub-RPE deposit and in the inner portion of the ciliary body deposit. TIMP-3 immunoreactivity was more extensive in the SFD eye. The pattern of elastin immunoreactivity was remarkably similar to that of TIMP-3. Electron microscopy revealed a morphologically altered elastic layer of the Bruch's membrane.

CONCLUSIONS

Sub-RPE TIMP-3 immunoreactivity appears more extensive in SFD than in control subjects. There is also a correspondence between TIMP-3 and elastin immunoreactivies, which invites speculation as to a link between the SFD TIMP-3 mutation and altered elastin processing. The accumulation of abnormal material in SFD is more widespread than previously reported. In view of this, SFD might be better termed Sorsby's ocular epitheliopathy.

Autosomal dominant cone-rod retinal dystrophy (CORD6) from heterozygous mutation of GUCY2D, which encodes retinal guanylate cyclase

OBJECTIVE

To describe the clinical features of autosomal dominant cone-rod retinal dystrophy (CRD) in a British family mapping to chromosome 17p12-p13 (CORD6), with a heterozygous mutation (Glu837Asp/ Arg838Ser) of GUCY2D.

DESIGN

A prospective, clinical family survey.

PATIENTS

Ten affected members of a family with autosomal dominant CRD.

METHODS

Full clinical examinations were undertaken. Selected affected family members underwent electrophysiologic evaluation, scotopic static perimetry, dark adaptometry, and color vision assessment.

MAIN OUTCOME MEASURES

Clinical appearance and electroretinographic responses.

RESULTS

Typical clinical and electroretinographic features of childhood-onset CRD were recorded. In addition, moderate myopia and pendular nystagmus were seen in affected individuals. Color vision assessment in the youngest affected individual showed no color discrimination on a tritan axis, but retention of significant red-green discrimination. Electronegative electroretinogram responses were seen on electrophysiology in the only young family member examined.

CONCLUSIONS

The phenotype associated with GUCY2D CRD is clinically distinct from that associated with other dominant CRD loci. Unusual electroretinographic responses may indicate that this mutation of GUCY2D is associated with early defects in photoreceptor synaptic transmission to second-order neurons.

Long-term drusen study

PURPOSE

To determine the yearly incidence of visual loss in the fellow eyes of patients with unilateral neovascular age-related macular degeneration (ARMD) and to assess the drusen characteristics portending the greatest risk for this outcome.

METHODS

A total of 101 patients with unilateral exudative ARMD and drusen only in the fellow eye were entered into the study and prospectively followed up to 9 years. Visual acuity, color fundus photography, fluorescein angiography, and grading of drusen characteristics were obtained for each patient on entry into the study. Patients were followed at annual intervals with color fundus photography. The study endpoint was the development of choroidal neovascularization (CNV) or geographic atrophy (GA) in the fellow eye.

RESULTS

Yearly incidence rates for the development of an endpoint lesion were between 5 and 14%. The risk of CNV peaked at 4 years and dissipated thereafter. Longer follow-up was associated with a slightly increased incidence of GA. Greater drusen number was most highly associated with the development of an endpoint lesion. Drusen size and confluence were also significant.

CONCLUSIONS

The risk of CNV in patients with ARMD is heralded by an increase in the number, size, and confluence of drusen. This risk eventually declines and is followed by later increased risk of GA.

A fluorescein and indocyanine green angiographic study of choriocapillaris in age-related macular disease

OBJECTIVE

To examine the phenomenon of a prolonged choroidal filling phase (PCFP) as seen on fluorescein and indocyanine green (ICG) angiography in patients with early age-related macular disease (AMD).

METHODS

One hundred eyes of consecutive patients with early AMD were studied. Patchy and slow choroidal filling in early fluorescein and distinct areas of reduced choroidal fluorescence in ICG angiography were interpreted as PCFP. In addition, associated drusen characteristics and the AMD status of the fellow eye were recorded.

RESULTS

A PCFP was observed in 26% of eyes using fluorescein and 32% of eyes using ICG angiography, with good concordance between findings using both techniques (K = 0.9). A PCFP was associated with confluent drusen (P = .01), the presence of focal retinal pigment epithelial-atrophic patches in the study eye (P=.005), and geographic atrophy in the fellow eye (P=.03). Other drusen characteristics and the distribution of visual acuity (P = .90) were not different between eyes with and without PCFP.

CONCLUSIONS

A PCFP on fluorescein and ICG angiography is a common feature in early AMD. This sign has been interpreted as indicating reduced choroidal perfusion caused by change in diffusional characteristics of Bruch membrane. A PCFP is a clinical marker for diffuse deposits in Bruch membrane and a risk factor for the development of geographic atrophy.