Why the macula?

The regional susceptibility of the retina to diseases has been well known by clinicians for many years. It is surprising that the implications of these observations have not spawned major research efforts to characterise the structural and functional attributes of the outer retina in different regions of a foveate retina. Without such an effort, the understanding of the disease mechanisms in retinal dystrophies will remain limited and may hamper therapeutic efforts. That outer retinal disease is responsible for over 50% of blind registration in the western world underlines the importance of these considerations.

Conflict monitoring in early frontotemporal dementia

BACKGROUND

Despite the extensive frontal atrophy and behavioral disinhibition that characterizes behavioral variant frontotemporal dementia (bvFTD), many studies of early bvFTD suggest normal executive functioning (EF). The current study examined cognitive control in patients with bvFTD who otherwise seemed cognitively normal.

METHODS

Subjects included 7 patients with bvFTD with normal neuropsychological test scores, 7 patients with bvFTD matched for Mini-Mental State Examination score but with impaired neuropsychological test scores, and 14 normal controls. A flanker paradigm and other measures of EF were administered to participants. A semiautomated parcellation program was used to analyze structural MRI scans.

RESULTS

On the flanker task, multivariate analysis of variance revealed a significant condition X diagnosis interaction. Both bvFTD groups showed a larger congruency effect than normal controls, i.e., they displayed disproportionately reduced speed and accuracy on incongruent trials relative to congruent trials. Imaging data illustrated significant orbitofrontal atrophy in patients with early bvFTD as compared with controls.

CONCLUSIONS

Patients with behavioral variant frontotemporal dementia (bvFTD) who performed within normal limits on clinical tests of executive functioning demonstrated a select impairment on an experimental test of cognitive control, suggesting a subtle impairment in inhibiting attention or response to the irrelevant stimuli. Measures of neuropsychological functioning sensitive to the ventromedial prefrontal cortex may be useful in early diagnosis of patients with bvFTD. Our understanding of this syndrome may be increased by considering the efficiency of selective inhibition, a fundamental component of executive cognitive control.

Functional aspects of drusen regression in age-related macular degeneration

AIMS

To investigate the functional implications of macular soft drusen regression in AMD eyes.

METHODS

Patients were selected from a large ongoing collection of clinical data at Moorfields Eye Hospital. Phenotyping based on standard colour fundus images was performed according to the system defined by the International Classification for ARM, by certified graders masked to the main aim of the study. Fundus autofluorescence (FA) was recorded using a Heidelberg Retina Angiograph 2. Where drusen regression was confirmed by independent grading, the patient was invited for photopic and scotopic fine matrix mapping (FMM). Phenotype and functional data were analysed for correlations between fundus appearance, autofluorescence and retinal sensitivity.

RESULTS

Fundus and FA images of 960 patients were screened, soft drusen regression was detected in 34 cases, and 14 patients agreed to participate in the study, ranging in age from 52 to 84 years (median 72). The mean follow-up period was 5.9 years (range 2.8-14.4 years). FMM showed generalised threshold elevation relative to normal controls both under photopic and scotopic conditions. Scotopic sensitivity loss exceeded photopic loss in all cases. Sensitivity loss over areas with drusen or regressed drusen did not differ significantly from that over non-drusen areas.

CONCLUSION

Macular soft drusen may fade or disappear without detectable ophthalmoscopic, FA or psychophysical signs of local dysfunction. This phenomenon is a potential source of misclassification. The prognosis for cases with true regression of drusen compared with those without needs to be considered in future studies on AMD.

Characterisation of the macular dystrophy in patients with the A3243G mitochondrial DNA point mutation with fundus autofluorescence

INTRODUCTION

The mitochondrial DNA A3243G point mutation is associated with a wide variety of systemic manifestations including a macular dystrophy. The characteristics of fundus autofluorescence (AF) in these patients are distinctive and have not been previously described.

METHODS

A complete history and ophthalmic examination, including fundus photography and autofluorescence imaging, was performed on twelve probands harbouring the A3243G point mutation.

RESULTS

Four patients had diabetes, 10/12 hearing loss, and 7/12 were visually symptomatic. A positive family history was present in 5/12. Fundus findings consisted of two primary phenotypes: discontinuous circumferentially oriented perifoveal atrophy (9/12) or an appearance consistent with pattern dystrophy (3/12). In both phenotypes pale deposits and pigment clumping were seen at the level of the retinal pigment epithelium, with occasional changes also noted outside the arcades and nasal to the optic nerve. Fundus AF imaging revealed decreased autofluorescence in areas of atrophy and increased AF of the pale subretinal deposits. In areas of the retina that appeared normal clinically, variable sized flecks of increased and decreased AF were present.

CONCLUSIONS

The mitochondrial DNA A3243G point mutation can result in disease with a variable presentation. Fundus autofluorescence reveals a recognisable phenotype in most cases that is different from other macular dystrophies.

ABCA4 mutations and discordant ABCA4 alleles in patients and siblings with bull's-eye maculopathy

AIM

To determine the frequency and nature of mutations in the gene ABCA4 in a cohort of patients with bull's-eye maculopathy (BEM).

METHODS

A panel of 49 subjects (comprising 40 probands/families, 7 sibling pairs and a set of three sibs) with BEM, not attributable to toxic causes, was ascertained. Blood samples from each patient were used to extract genomic DNA, with subsequent mutation screening of the entire coding sequence of ABCA4, using single-strand conformational polymorphism (SSCP) analysis and direct sequencing.

RESULTS

Fourteen probands (35%) were found to have a potentially disease-causing ABCA4 sequence variant on at least one allele. Three patients had a Gly1961Glu missense mutation, the most common variant in Stargardt disease (STGD), with 2 of these subjects having a macular dystrophy (MD) phenotype and a second ABCA4 variant previously associated with STGD. The second most common STGD mutation, Ala1038Val, was seen in one patient with cone-rod dystrophy (CORD). Five novel ABCA4 variants were detected. Two sibships were identified with a similar intra-familial phenotype but discordant ABCA4 variants.

CONCLUSIONS

Variations in the ABCA4 gene are common in BEM. Two sibships showed discordant ABCA4 variants. One of these sibships illustrates that ABCA4 variants can be identified in families that have another molecular cause for their disease, due to the high prevalence of ABCA4 disease alleles in the population. The discordance evident in the second sibship may yet also be a chance finding in families with macular disease of another genetic cause, or it may represent a complex mode of inheritance determined/modified by the combination of ABCA4 alleles.

Functional correlates of fundus autofluorescence abnormalities in patients with RPGR or RIMS1 mutations causing cone or cone rod dystrophy

AIM

The aim of this study was to establish the functional significance of annular macular abnormalities present on fundus autofluorescence imaging (AF) in patients with cone or cone-rod dystrophy.

METHODS

Fundus AF was performed on ten subjects (age range 18-82 years) with cone or cone-rod dystrophy consequent upon RPGR or RIMS1 mutation. International-standard full-field and pattern electroretinograms (ERGs) were performed in all cases. Photopic and scotopic fine matrix mapping (FMM) and multifocal ERG were performed on selected cases.

RESULTS

Subjects had annuli of high density AF that bordered central areas of low density in older RPGR cases and most RIMS1 cases. The size of the AF ring correlated with age and enlarged with time in two subjects. High-density rings were associated with a gradient of scotopic and photopic sensitivity loss. Pattern electroretinogram (PERG) P50 amplitude, when detectable, was inversely related to the size of the AF ring. Multifocal ERGs in two subjects showed widespread reduction with relative sparing over the foveal area, in keeping with FMM data.

CONCLUSIONS

Some patients with cone-rod dystrophy have a parafoveal ring of increased autofluorescence that may enlarge with time. Increased autofluorescence is associated with reduced rod and cone sensitivity, rather than photoreceptor cell death, and AF imaging may help identify viable areas of retina amenable to future therapeutic intervention.

Macular pigment in the human retina: histological evaluation of localization and distribution

PURPOSE

Clinical investigations have demonstrated variation in both the peak optical density and the spatial distribution of macular pigment. To confirm these impressions histologically, the present study examined the distribution of macular pigment in the human retina.

MATERIALS AND METHODS

The macular retina of 11 donor eyes of different ages (28-91 years) were examined histologically on 100 microm vibratome sections directly, without further staining. Measurements were made in two dimensions: (1) adding the number of macular sections with visible macular pigment, and (2) direct measurement of the extension of macular pigment in the foveolar section, which visibly contained the most macular pigment.

RESULTS

The measurements with two methods demonstrated good correlation. The macula demonstrated a variation in the spatial extension of the visible macular pigment between 200 and 900 microm diameter around the centre of the fovea, which was also found when direct measurements were taken. There was no correlation with the donor age. The main location of macular pigment was in the layer of the fibres of Henle in the fovea and in the inner nuclear layer at the parafoveal site.

CONCLUSIONS

Histologically, a wide variation of the spatial distribution of macular pigment was found that confirms clinical observations. The primary localization of human macular pigment is in the inner retinal layers.

Clinical characterisation of a family with retinal dystrophy caused by mutation in the Mertk gene

BACKGROUND/AIM

MERTK, a tyrosine kinase receptor protein expressed by the retinal pigment epithelium (RPE), is mutated in both rodent models and humans affected by retinal disease. This study reports a survey of families for Mertk mutations and describes the phenotype exhibited by one family.

METHODS

96 probands with retinal dystrophy, consistent with autosomal recessive segregation, were screened by direct sequencing. A family homozygous for a likely null allele was investigated clinically.

RESULTS

A novel frame shifting deletion was identified in one of 96 probands. Other polymorphisms were detected. The deletion allele occurred on both chromosomes of four affected family members. Electrophysiology demonstrated early loss of scotopic and macular function with later loss of photopic function. Visual acuities and visual fields were preserved into the second decade. Perception of light vision was present in a patient in the fourth decade. A "bull's eye" appearance and a hyperautofluorescent lesion at the central macula were consistent clinical findings.

CONCLUSIONS

Mutations in Mertk are a rare cause of ARRP in humans. The study extends the phenotypic characteristics of this retinal dystrophy and shows distinctive clinical signs that may improve its clinical identification. The moderate severity and presence of autofluorescence implies that outer segment phagocytosis is not entirely absent.

Functional characterisation and serial imaging of abnormal fundus autofluorescence in patients with retinitis pigmentosa and normal visual acuity

AIM

To characterise and monitor abnormal fundus autofluorescence (AF) in patients with retinitis pigmentosa (RP) who have good visual acuity.

METHODS

21 patients with a clinical diagnosis of RP were examined. All had rod-cone dystrophy (ISCEV standard electroretinograms (ERGs)), visual acuity of 6/9 or better, and manifested a parafoveal ring of high density fundus AF. Repeat AF imaging was performed after periods of between 2 years and 5 years in 12 patients. Pattern ERG (PERG) and multifocal ERG (mfERG) were performed in 20 cases. Visual fields (VF), photopic and scotopic fine matrix mapping and small field PERGs were performed in representative cases.

RESULTS

The rings of high density AF varied in size between patients (from 4 degrees -16 degrees diameter). MfERGs showed relative preservation over the central macular area, correlating with the size of AF ring and with PERG and psychophysical data. Progressive constriction of the AF ring was demonstrated at follow up in three patients. Serial PERG, mfERG, and VFs, performed in one of these cases, showed evidence of deterioration concordant with ring constriction.

CONCLUSIONS

High density rings of AF, seen in some patients with RP with good visual acuity, demarcate areas of preserved central photopic function. MfERGs correlate with the area encircled by high density AF and the PERG data. The size of the ring of AF can show progressive constriction accompanied by increasing macular dysfunction.

Does smoking influence the type of age related macular degeneration causing visual impairment?

AIMS

To assess the influence of smoking on the type of age related macular degeneration (AMD) lesion causing visual impairment in a large cohort of patients with AMD at a tertiary referral UK centre.

METHODS

Prospective, observational, cross sectional study to analyse smoking data on 711 subjects, of western European origin, in relation to the type of AMD lesion present. Colour fundus photographs were graded according to a modified version of the international classification. Multiple logistic regression analysis was performed, adjusting for age and sex using the statistical package SPSS ver 9.0 for Windows. chi(2) tests were also used to assess pack year and ex-smoker data.

RESULTS

578 subjects were graded with neovascular AMD and 133 with non-neovascular AMD. There was no statistically significant association found between smoking status or increasing number of pack years and type of AMD lesion. The odds of "current smokers" compared to "non-smokers" developing neovascular rather than non-neovascular AMD when adjusted for age and sex was 1.88 (95% CI: 0.91 to 3.89; p = 0.09).

CONCLUSIONS

Smoking is known to be a risk factor for AMD and this study suggests that smokers are at no more risk of developing neovascular than atrophic lesions.

Age related macular degeneration and sun exposure, iris colour, and skin sensitivity to sunlight

BACKGROUND/AIM

It has been suggested that sun exposure may be a risk factor for age related macular degeneration (AMD) and that skin sensitivity to sunlight and iris colour could be confounding factors. The aim was to investigate this further in the white population.

METHODS

446 cases with end stage AMD were compared with 283 spouse controls. Data on sun exposure, places of residence, iris colour, subjective assessment of change in iris colour, hair colour at age 20, and skin sensitivity were obtained using a questionnaire. Iris colour was graded clinically by comparison with standard photographs. AMD was graded using stereoscopic colour fundus photographs as well as clinical examination and was defined as the presence of geographic atrophy or choroidal neovascularisation. All variables were included in a multiple logistic regression model including age, sex, and smoking.

RESULTS

There was no association between AMD and sun exposure or related factors except for the suggestion of an association between sunburn prone skin type and geographic atrophy which reached borderline significance.

CONCLUSIONS

No significant association between AMD and sun exposure, iris colour, change in iris colour, or hair colour was demonstrated.

Smoking and age related macular degeneration: the number of pack years of cigarette smoking is a major determinant of risk for both geographic atrophy and choroidal neovascularisation

BACKGROUND/AIMS

There is evidence that smoking is a risk factor for age related macular degeneration (AMD). However, not all studies have demonstrated this association and several key questions about the role of smoking in AMD have still to be determined. The aim of this study was to further investigate this relation for both choroidal neovascularisation (CNV) and geographic atrophy (GA).

METHODS

To investigate the relation between smoking and the risk of developing age related macular degeneration (AMD) in white people, 435 cases with end stage AMD were compared with 280 controls. All subjects had graded stereoscopic colour fundus photography and AMD was defined as the presence of GA or CNV. Smoking history was assessed using multiple parameters in a detailed questionnaire.

RESULTS

Comparison of current and former smokers with non-smokers was consistent with smoking being a risk factor for AMD but did not reach statistical significance. There was a strong association between AMD and pack years of cigarette smoking (p = 0.002), the odds ratio increasing with the amount smoked; for subjects with more than 40 pack years of smoking the odds ratio was 2.75 (95% CI 1.22 to 6.20) compared with non-smokers. Both types of AMD showed a similar relation; smoking more than 40 pack years of cigarettes was associated with an odds ratio of 3.43 (95% CI 1.28 to 9.20) for GA and 2.49 (95% CI 1.06 to 5.82) for CNV. Stopping smoking was associated with reduced odds of AMD and the risk in those who had not smoked for over 20 years was comparable to non-smokers. The risk profile was similar for males and females. Passive smoking exposure was associated with an increased risk of AMD (OR 1.87; 95% CI 1.03 to 3.40) in non-smokers.

CONCLUSIONS

The authors have demonstrated a strong association between the risk of both GA and CNV and pack years of cigarette smoking. This provides support for a causal relation between smoking and AMD. They also show an increased risk for AMD in non-smokers exposed to passive smoking. Stopping smoking appears to reduce the risk of developing AMD.

Functional observations in vitamin A deficiency: diagnosis and time course of recovery

AIMS

To describe the effects of vitamin A deficiency (VAD) on retinal function and the subsequent recovery following treatment in three patients with systemic conditions (two with Crohn disease; one secondary to IgE syndrome).

METHODS

Electrophysiological testing (including pattern electroretinogram, PERG; electroretinogram, ERG; visual-evoked potential) established the diagnosis of VAD. Repeat testing was carried out in two patients to monitor the time course of recovery following intramuscular vitamin A injection. The third patient had repeat recordings following 13 months of oral supplementation.

RESULTS

All three patients initially displayed a characteristic absence of rod function associated with VAD. In addition, delayed and reduced amplitude cone ERGs, loss of short wavelength cone (S-cone) function and subnormal macular function were observed in two patients. Restoration of rod and generalised cone function was rapid in the two patients who received intramuscular injection, with normalisation of some electrophysiological responses after only 3 days. Normal S-cone amplitudes and cone latencies were reached within 12 days of vitamin A injection. Macular function returned to within normal limits by 12 days postinjection in one patient, but remained mildly subnormal in the second patient. Full recovery was present after 13 months oral supplementation in the third patient.

CONCLUSIONS

Novel observations regarding dark-adapted cone function, S-cone function, and PERG are presented. The differences between the effects of VAD on rod and cone function, and their rate of recovery, may reflect differences in the visual cycle between the two photoreceptor classes. The importance of rapidly and accurately diagnosing VAD, a treatable condition, is noted.

Pathogénie des lésions de la dégénérescence maculaire liée à l’âge à un stade avancé

To summarize the evidence that exists concerning the pathogenesis of lesions in late age-related macular disease (AMD), we reviewed both experimental evidence and clinical observations that address these problems. There is good evidence that choroidal neovascularization is due to a change in the balance of growth factors derived from the retinal pigment epithelial basolateral plasma membrane domain (RPE). Retinal angiomatous proliferation may also have a similar pathogenesis involving the apical domain. Detachment of the RPE is likely to be a consequence of increased resistance of Bruch's membrane to water flow due to deposition of lipids. Geographic atrophy is preceded by accumulation of autofluorescent material in the RPE and possible causal relationships between the two have been demonstrated. There is increasing understanding concerning the sequence of events that lead to those lesions causing loss of central vision in AMD. Therapeutic approaches that address the underlying mechanisms are more likely to succeed than current treatment options. Such an approach has already been initiated in the management of choroidal neovascularization.

Visual functioning and quality of life in the SubFoveal Radiotherapy Study (SFRADS): SFRADS report 2

AIMS

To determine whether or not self reported visual functioning and quality of life in patients with choroidal neovascularisation caused by age related macular degeneration (AMD) is better in those treated with 12 Gy external beam radiotherapy in comparison with untreated subjects.

METHODS

A multicentre single masked randomised controlled trial of 12 Gy of external beam radiation therapy (EBRT) delivered as 6 x 2 Gy fractions to the macula of an affected eye versus observation. Patients with AMD, aged 60 years or over, in three UK hospital units, who had subfoveal CNV and a visual acuity equal to or better than 6/60 (logMAR 1.0).

METHODS

Data from 199 eligible participants who were randomly assigned to 12 Gy teletherapy or observation were available for analysis. Visual function assessment, ophthalmic examination, and fundus fluorescein angiography were undertaken at baseline and at 3, 6, 12, and 24 months after study entry. To assess patient centred outcomes, subjects were asked to complete the Daily Living Tasks Dependent on Vision (DLTV) and the SF-36 questionnaires at baseline, 6, 12, and 24 months after enrolment to the study. Cross sectional and longitudinal analyses were conducted using arm of study as grouping variable. Regression analysis was employed to adjust for the effect of baseline co-variates on outcome at 12 months and 24 months.

RESULTS

Both control and treated subjects had significant losses in visual functioning as seen by a progressive decline in mean scores in the four dimensions of the DLTV. There were no statistically significant differences between treatment and control subjects in any of dimensions of the DLTV at 12 months or 24 months after study entry. Regression analysis confirmed that treatment status had no effect on the change in DLTV dimensional scores.

CONCLUSIONS

The small benefits noted in clinical measures of vision in treated eyes did not translate into better self reported visual functioning in patients who received treatment when compared with the control arm. These findings have implications for the design of future clinical trials and studies.

A detailed phenotypic study of "cone dystrophy with supernormal rod ERG"

AIMS

To characterise the detailed phenotype of "cone dystrophy with supernormal rod ERG" in a case series of 10 patients.

METHODS

10 affected patients were examined clinically and underwent colour fundus photography, with nine undergoing detailed electrophysiological testing. Five patients were assessed further with fundus autofluorescence (AF) imaging, automated photopic and dark adapted perimetry, and dark adaptometry. Detailed colour vision assessment was performed in six subjects. Blood samples were taken from four patients for DNA extraction and mutation screening of NR2E3 was undertaken.

RESULTS

The onset of symptoms was in the first and second decades of life. Subjects presented with reduced central vision and marked photophobia. All individuals were myopic and colour vision testing revealed severely reduced colour discrimination predominantly along the red-green axes; tritan colour vision was relatively well preserved. Nyctalopia is a later feature of the disorder. Funduscopy and AF imaging revealed a range of macular appearances. There was electrophysiological evidence of marked macular dysfunction, reduced and delayed cone responses, and supernormal and delayed rod responses. Photopic and dark adapted perimetry revealed central scotomata with widespread peripheral sensitivity loss. No disease causing sequence variants in NR2E3 were identified.

CONCLUSIONS

The largest case series to date has been described of the clinical, psychophysical and electrophysiological characteristics of this unusual cone dystrophy with supernormal rod responses. Electrophysiological data were consistent with a post-phototransduction, but pre-inner nuclear layer, site of dysfunction. While the definitive diagnosis can only be made with electrophysiological testing, several characteristics that may increase suspicion of this diagnosis are presented.

A detailed study of the phenotype of an autosomal dominant cone-rod dystrophy (CORD7) associated with mutation in the gene for RIM1

AIM

To characterise the phenotype of an autosomal dominant cone-rod dystrophy (CORD7) associated with the Arg844His mutation in RIM1.

METHODS

Eight members of a four generation, non-consanguineous British family were examined clinically and underwent electrophysiological testing, automated dark adapted perimetry, dark adaptometry, colour vision assessment, colour fundus photography, fundus fluorescein angiography (FFA), and fundus autofluorescence (AF) imaging.

RESULTS

The majority of affected individuals described a progressive deterioration of central vision, night vision, and peripheral visual field usually between the third and fourth decades. The visual acuity ranged from 6/6 to 3/60. Colour vision testing showed mild to moderate dyschromatopsia in the majority of individuals. Fundus changes comprised a range of macular appearances varying from mild retinal pigment epithelial (RPE) disturbance to extensive atrophy and pigmentation. In some individuals retinal vessels were attenuated and in two subjects peripheral areas of retinal atrophy were present. An absent or severely reduced PERG was detected in all subjects, indicative of marked macular dysfunction. Full field ERG showed abnormal rod and cone responses. AF imaging revealed decreased macular AF centrally surrounded by a ring of increased AF in the majority of individuals. "Bull's eye" lesions were present in two individuals, comprising of a ring of decreased perifoveal AF bordered peripherally and centrally by increased AF. Photopic sensitivity testing demonstrated elevated central visual field thresholds with additional superior greater than inferior peripheral field loss. There were rod and cone sensitivity reductions in the central and peripheral visual fields, with the inferior retina being more affected than the superior.

CONCLUSIONS

The detailed phenotype is described of the autosomal dominant cone-rod dystrophy, CORD7, which is associated with a point mutation in RIM1, a gene encoding a photoreceptor synaptic protein. The pattern of disease progression and long term visual outcome facilitates improved genetic counselling and advice on prognosis. Such phenotypic data will be invaluable in the event of future therapy.

Acute zonal occult outer retinopathy: towards a set of diagnostic criteria

BACKGROUND

Individuals with acute zonal occult outer retinopathy (AZOOR) present with initially progressive scotomata and photopsia. Characteristically, the extent of the visual field defect is unexplained by fundal examination, but there is marked retinal dysfunction evident electrophysiologically. It is the authors' experience that a group of patients exhibit characteristic clinical and electrophysiological abnormalities, which serve as criteria for a working diagnosis.

METHODS

A retrospective observational case series of 28 patients were identified with the clinical diagnosis of AZOOR who shared similar abnormal electrophysiology. Details of the history and ophthalmic findings were obtained from the case notes.

RESULTS

Electrophysiology demonstrated a consistent pattern of dysfunction both at the photoreceptor/retinal pigment epithelial complex but also at inner retinal levels, essentially comprising a delayed 30 Hz flicker ERG and a reduction in the EOG light rise.

CONCLUSION

This study determines diagnostic criteria applicable to a group of patients with AZOOR, typically those with classic symptomatology. Electrophysiological testing can help avoid lengthy, costly, and potentially invasive investigations, and the unnecessary use of immunosuppressive therapy.

Congenital stationary night blindness and a "Schubert-Bornschein" type electrophysiology in a family with dominant inheritance

BACKGROUND/AIMS

To present the clinical, psychophysical, and electrophysiological characteristics of a family with dominantly inherited congenital stationary night blindness (CSNB).

METHODS

Five affected family members from three generations were ascertained. Four affected individuals underwent ophthalmic examination and electrodiagnostic investigations. Three affected individuals also underwent scanning laser ophthalmoscopy and psychophysical testing.

RESULTS

Affected individuals reported night blindness from an early age. Visual acuities were normal. Fundal appearances were normal apart from one older patient showing areas of peripheral chorioretinal atrophy. Autofluorescence images showed no gross abnormality. International Society for Clinical Electrophysiology of Vision (ISCEV) standard electroretinography (ERG) showed undetectable rod specific responses and electronegative maximal responses, but normal ISCEV cone responses. Additional S-cone specific ERG recordings were of reduced amplitude in all patients studied. There was no apparent rod component to the dark adaptation curve. Central 30 degrees thresholds were normal under photopic conditions but showed increased thresholds under scotopic conditions for both red and blue stimuli.

CONCLUSION

Results from investigation of this family are consistent with an impairment of rod photoreceptor signalling. The ERG findings suggest an abnormality occurring after phototransduction with rod and S-cone pathway involvement. These findings differ from those rare families reported previously with dominant CSNB.

Fundus autofluorescence imaging compared with different confocal scanning laser ophthalmoscopes

BACKGROUND

With the advent of confocal scanning laser ophthalmoscopes (cSLO), fundus autofluorescence (FAF) resulting mainly from lipofuscin accumulation on the level of the retinal pigment epithelium can be visualised in vivo. Various cSLOs are available to document FAF. The authors analysed and compared results of FAF using three different instruments.

METHODS

Eight eyes of eight normal volunteers and 18 eyes of 12 patients with different retinal diseases (age related macular degeneration, macular dystrophy, central serous retinopathy) were examined. FAF images were recorded from each subject with the Heidelberg retina angiograph (HRA), the Rodenstock cSLO (RcSLO) and the Zeiss Prototype SM 30-4024 (ZcSLO). For excitation an argon laser (488 nm) was used (barrier filter: HRA 500 nm; RcSLO 515 nm; ZcSLO 521 nm). 32 FAF images were aligned and averaged using the same software for all cSLOs. FAF distribution was measured and grey scale values as well as root mean square (RMS) contrast were compared.

RESULTS

Mean age of all subjects was 55.5 (SD 21.4) years. The maximum grey scale value averaged across all eyes was 76.19 (39.34) for the HRA, 61.44 (22.12) for the ZcSLO and 37.0 (9.97) for the RcSLO. The RMS contrast was 0.46 (0.20) for the ZcSLO, 0.40 (0.12) for the HRA, and 0.13 (0.05) for the RcSLO. The differences between the cSLOs were statistically significant with higher grey scale levels and more contrast for the HRA and ZcSLO than the RcSLO (repeated measures ANOVA; p<0.0001). The differences between the HRA and the ZcSLO were not significant (post hoc comparisons; p<0.05).

CONCLUSIONS

All cSLOs allow clinically useful FAF imaging in retinal diseases. However, grey scale levels and contrast were much lower on the RcSLO. Therefore, RcSLO images appear much darker than HRA or ZcSLO images. Furthermore, not all cSLOs have a fixed photodetector gain and a standardised value for the argon laser amplification, which is mandatory for an absolute comparison of FAF imaging results.

Macular pigment: quantitative analysis on autofluorescence images

BACKGROUND

Macular pigment (MP) reduces oxidative damage in the central retina and can be quantified by flicker-photometric analysis (HFP) of MP optical density. These analyses demonstrate a very good correlation with central absorption by MP on autofluorescence (AF) images. With these techniques different types of MP-distribution have been described. In the present study a quantification analysis of MP in AF images was developed to verify these MP types and to compare MP distribution patterns between healthy individuals and those with age-related macular degeneration (AMD).

METHODS

AF images (HRA) were analysed with respect to the area of central and paracentral absorption in 400 eyes with a computerised analysis program of MP optical density. The patients were between 41 and 90 years old (mean 67.2 years); 168 were male and 232 female, and 253 had early AMD and 147 showed no AMD characteristics. The central MP concentrations (peak) were measured, the amount of MP values within the first 8-pixel radius ("C"), the total amount of MP within a 120-pixel radius ("T") were calculated as the volume of the MP values over the regarded radius and the C/T ratio was registered.

RESULTS

Four types of MP distribution (type 1, intense central and paracentral MP; type 2, less intense central and paracentral MP; type 3, only central MP; type 4, only paracentral MP) were identified. The differences in MP distribution were confirmed and clearly characterised by quantitative analyses of peak, total MP ("T"), central MP ("C") and C/T ratio: mean peak in type 1, 0.65; type 2, 0.42; type 3, 0.42; type 4, 0.29; mean total amount of MP in 120-pixel radius ("T") in type 1, 5829.0; type 2, 4412.5; type 3, 2709; type 4, 4302.8. MP types with lower levels of MP were significantly more often observed in the AMD group (AMD: type 1, 120=47.4%; types 2-4, 133=52.6%; healthy eyes: type 1, 112=76.2%; types 2-4, 35=23.8%) ( P<0.0001)

CONCLUSIONS

Analysis of MP on AF images is a quantitative method for investigation of MP. With this method a wide variation in concentration and distribution of MP could be seen in the population. Four different types of MP distribution could be characterised and quantitatively distinguished. Reduced levels of MP seem to be associated with a higher risk of development of AMD as they were significantly more often observed in the AMD group. This strategy of quantitative MP analysis on AF images is easily practicable and may be used in further studies to investigate the role of MP as a potential risk factor for AMD.

Genotype-phenotype correlation in British families with X linked congenital stationary night blindness

AIM

To correlate the phenotype of X linked congenital stationary night blindness (CSNBX) with genotype.

METHODS

11 CSNB families were diagnosed with the X linked form of the disease by clinical evaluation and mutation detection in either the NYX or CACNA1F gene. Phenotype of the CSNBX patients was defined by clinical examination, psychophysical, and standardised electrophysiological testing.

RESULTS

Comprehensive mutation screening identified NYX gene mutations in eight families and CACNA1F gene mutations in three families. Electrophysiological and psychophysical evidence of a functioning but impaired rod system was present in subjects from each genotype group, although the responses tended to be more severely affected in subjects with NYX gene mutations. Scotopic oscillatory potentials were absent in all subjects with NYX gene mutations while subnormal OFF responses were specific to subjects with CACNA1F gene mutations.

CONCLUSIONS

NYX gene mutations were a more frequent cause of CSNBX than CACNA1F gene mutations in the 11 British families studied. As evidence of a functioning rod system was identified in the majority of subjects tested, the clinical phenotypes "complete" and "incomplete" do not correlate with genotype. Instead, electrophysiological indicators of inner retinal function, specifically the characteristics of scotopic oscillatory potentials, 30 Hz flicker and the OFF response, may prove more discriminatory.

Prophylactic laser treatment appears to promote choroidal neovascularisation in high-risk ARM: results of an interim analysis

PURPOSE

The Drusen Laser Study (DLS) of high-risk age-related maculopathy (ARM) is a randomised, controlled clinical trial designed to answer two questions: (1). Do drusen resolve after macular laser photocoagulation (2). Does macular laser photocoagulation prevent choroidal neovascularisation (CNV) in high-risk eyes? In this report, we present the results of the interim, pooled analysis of CNV prophylaxis for patients in the Unilateral Group of the DLS.

METHODS

The DLS is a randomised controlled clinical trial of prophylactic macular photocoagulation for high-risk ARM. Patients in the Unilateral Group had a neovascular complication in the first eye; their fellow eye (Study Eye) had visual acuity of 6/12 or better and drusen. Following informed consent, patients were randomised to the Treatment Group or the No Treatment Group. Patients randomised to treatment received 12 light spots of argon laser photocoagulation to their Study Eye: four burns were placed 750 microm from the centre of the fovea at 12, 3, 6, and 9 o'clock, and the eight remaining burns were placed 1500 microm from the centre of the fovea at 12, 1:30, 3, 4:30, 6, 7:30, 9, and 10:30 o'clock. Drusen were treated directly only if they were present at the protocol treatment locations. All patients were followed in an identical fashion at regular intervals. Best-corrected visual acuity was measured and recorded by a masked observer. Fluorescein angiography was performed at baseline and yearly review, as well as nonprotocol visits if symptoms suggested CNV. Five clinical centres utilised and conformed to a common DLS protocol. Patient care and data collection methodologies were deemed sufficiently similar to permit a pooled data analysis.

RESULTS

There were 156 patients included in the interim analysis, and timed information was available on 153. CNV occurred in 21 of 81 (26%) patients in the Treatment Group and in 13 of 75 (17%) patients in the No Treatment Group (P=0.19). Kaplan-Meier survival analysis showed earlier onset of CNV in the Treatment Group compared to patients in the No Treatment Group (statistical significance not calculated). Visual acuity loss at 2 years occurred in nine of 54 (17%) patients in the Treatment Group compared to the two of 48 (4%) patients in the No Treatment Group (P=0.056).

CONCLUSIONS

We are only the second group to identify possible laser-induced CNV despite other similar studies in progress. Equipoise of the DLS investigators was lost, and recruitment was halted. We feel ethically bound to notify the ophthalmic community of this finding.

The contribution of USH1C mutations to syndromic and non-syndromic deafness in the UK

Denaturing high-performance liquid chromatography (DHPLC) was used to screen 14 UK patients with Usher syndrome type 1, in order to assess the contribution of mutations in USH1C to type 1 Usher. In addition, 16 Caucasian sib pairs and two small consanguineous families with non-syndromic deafness, who were concordant for haplotypes around DFNB18, were also screened for mutations in the USH1C gene. Two Usher type 1 patients were found to have the 238-239insC mutation reported previously; one of Greek Cypriot origin was homozygous for the mutation and another Caucasian was heterozygous. This indicates that mutations in the USH1C gene make a greater contribution to Usher syndrome type 1 than originally thought, which has implications for the genetic testing of families with Usher syndrome in the UK. Analysis using intragenic single nucleotide polymorphisms (SNPs) revealed that the haplotypic background bearing this common mutation was not consistent across the gene in two families, and that there are either two haplotypes on which the mutation has arisen or that there has been a recombination on a single haplotype. We found no evidence of mutations in USH1C in the patients with non-syndromic deafness, suggesting that the gene is not a major contributor to autosomal-recessive non-syndromic deafness in the UK.

Visual outcomes in the subfoveal radiotherapy study: a randomized controlled trial of teletherapy for age-related macular degeneration

OBJECTIVE

To determine whether teletherapy with 6-mV photons can reduce visual loss in patients with subfoveal choroidal neovascularization in age-related macular degeneration.

DESIGN

A multicenter, single-masked, randomized controlled trial of 12 Gy of external beam radiation therapy delivered to the macula of an affected eye vs observation only.

SETTING

Three United Kingdom-based hospital units.

PARTICIPANTS

Patients with age-related macular degeneration, aged 60 years and older, who had subfoveal choroidal neovascularization and a visual acuity of 20/200 (logMAR 1.0) or better.

METHODS

Two hundred three patients were randomly assigned to radiotherapy or observation. Treatment was undertaken at designated radiotherapy centers, and patients assigned to the treatment group received a total dosage of 12 Gy of 6-mV photons in 6 fractions. Follow-up was scheduled at 3, 6, 12, and 24 months. After excluding protocol violators, the data from 199 patients were analyzed.

MAIN OUTCOME MEASURES

The primary outcome measure was mean loss of distance visual acuity in the study eye at 12 and 24 months. Other outcome variables analyzed were near visual acuity and contrast sensitivity. The proportions of patients losing 3 or more or 6 or more lines of distance and near acuity and 0.3 or more or 0.6 or more log units of contrast sensitivity at each follow-up were also analyzed.

RESULTS

At all time points, mean distance visual acuity was better in the radiotherapy-treated group than in the control group, but the differences did not reach statistical significance. At 24 months, analysis of the proportions of patients with loss of 3 or more (moderate) (P =.08) or 6 or more (severe) (P =.29) lines of distance vision showed that fewer treated patients had severe losses, but there was no statistically significant difference between groups. For near visual acuity, although there was no evidence of treatment benefit at 12 and 24 months, a significant difference in favor of treatment was present at 6 months (P =.048). When analyzed by the proportions of patients losing 3 lines of contrast sensitivity, there was a significant difference in favor of treatment at 24 months (P =.02). No adverse retinal effects were observed during the study, but transient disturbance of the precorneal tear film was noted in treated patients.

CONCLUSION

The results of the present trial do not support the routine clinical use of external beam radiation therapy in subjects with subfoveal choroidal neovascularization in age-related macular degeneration.

Low vision services for vision rehabilitation in the United Kingdom

AIM

Little is known about the distribution and methods of delivery of low vision services across the United Kingdom. The purpose of this study was to determine the type and location of low vision services within the UK.

METHODS

Survey by means of a 29 point postal questionnaire, followed when necessary by a five point telephone questionnaire. All known potential providers of low vision services (n = 2539) including hospitals (n = 277), optician/optometry practices (n = 1683), social services (n = 177), voluntary groups (n = 190), specialist teachers (n = 205), and universities (n = 6) were surveyed. For each service provider, the type, magnitude, and geographical location were determined. The distribution of services across the United Kingdom and the ratio of providers to population density of people with a visual impairment were mapped using the Geographic Information System (GIS).

RESULTS

Data were obtained on 1945 (77%) service providers: 1679 (66%) responded to the postal questionnaire and 266 (11%) to the telephone questionnaire. Of all respondents, 59% (n = 1135) offer some form of help to people with a visual disability, of which 26% (n = 497) only sell magnifiers and 33% (n = 638) provide low vision services. It is estimated that in total just under 155,000 low vision consultations are offered annually, the bulk of which are provided by hospital eye departments. The distribution was geographically uneven and there appears to be scarcity in some areas.

CONCLUSION

When compared to the probable number of people with a visual impairment in the UK there are apparent inadequacies in service provision in terms of distribution, magnitude, and coordination. The results highlight a need to review current services.

Pigment epithelial detachment in the elderly. Clinical differentiation, natural course and pathogenetic implications

BACKGROUND

A prospective analysis was performed to characterize the angiographic appearance, natural course and prognosis of serous pigment epithelial detachments (PEDs) in elderly patients. The aim was to differentiate PEDs according to their angiographic characteristics and to analyze the specific clinical, visual and morphologic course of the different PEDs.

METHODS

Fluorescein and indocyanine green angiography were performed in 101 consecutive patients (53-87 years; 63 female, 38 male) with clinical signs of serous PED and drusen.

RESULTS

Different types of serous PED were identified: polypoidal choroidal vasculopathy (PCV)-associated PED in 14 patients (13.9%), vascular PED in 72 (71.2%), and avascular PED in 15 (14.9%). All PEDs resulted initially in similar visual loss. Avascular PEDs were smaller than vascular PEDs, and the latter were smaller than PCV-PEDs. During follow-up these differences were always present, but all PEDs enlarged initially followed by regression. This course was associated in all PEDs with progressive visual loss, accompanied by the development of RPE atrophy in avascular PEDs or disciform scars or RPE tears in the two other types.

CONCLUSION

Despite different associations, all PEDs have a similar clinical course with respect to visual loss and enlargement or regression. This is compatible with the proposed common pathogenetic background with a hydrophobic barrier in Bruch's membrane causing fluid resulting from RPE pumping activity to accumulate between the pigment epithelium and Bruch's membrane.

Retinal pigment epithelium translocation and central visual function in age related macular degeneration: preliminary results

PURPOSE

To test the feasibility of a new surgical technique, and to assess visual function over the translocated retinal pigment epithelium (RPE) cells in patients operated upon for subfoveal choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD).

MATERIALS AND METHODS

Six patients presenting previously untreated exudative AMD underwent surgical excision of the subfoveal CNV with RPE translocation and were followed from 1 to 10.5 months. The surgery consisted of a standard three port pars plana vitrectomy (TPPPV), excision of the CNV and RPE translocation. Pre and post-operative ocular examination included best-corrected visual acuity measurement, fundus color stereo photography and fundus fluorescein angiography. Optical coherence tomography (OCT) and confocal laser scanning ophthalmoscopy (cLSO) were performed post-operatively. A cross fixation target and a single-point flashing light were projected on different areas of the posterior pole using a cLSO. Photopic 10-2 perimetry, photopic fine matrix mapping, cLSO microperimetry were also performed pre and post-operatively in four patients. OCT cross-sectional scans and cLSO RPE autofluorescence were recorded to detect the presence of viable translocated RPE. Visual acuity, fixation, photopic 10-2 perimetry, photopic fine matrix mapping and cLSO microperimetry were tested for the presence of central visual function.

RESULTS

RPE could be effectively translocated at the time of CNV removal from the edge of the RPE defect to a subfoveal location. OCT showed the translocated RPE as an area of increased optical reflectivity with optical shadowing external to it. cLSO showed autofluorescence of the translocated RPE. The cross fixation target was seen when projected on the translocated RPE. During eccentric fixation, the patients could see a flashing point-target projected on the translocated RPE. Photopic 10-2 perimetry, photopic fine matrix mapping and cLSO microperimetry showed presence of central visual function.

CONCLUSIONS

The authors propose that translocation of RPE at the time of CNV removal, from the edge of the RPE defect to a subfoveal location, may have a role in the surgical management of AMD.

Symptomatic abnormalities of dark adaptation in patients with EFEMP1 retinal dystrophy (Malattia Leventinese/Doyne honeycomb retinal dystrophy)

PURPOSE

To investigate the nature of symptomatic visual disturbance in patients with EFEMP1 retinal dystrophy in the absence of geographic atrophy or choroidal neovascularization.

METHODS

Patients presenting to a tertiary referral centre underwent clinical evaluation, fluorescein angiography, colour contrast sensitivity, focal, pattern, and standard electroretinography, electrooculography, scotopic threshold perimetry and dark adaptometry.

RESULTS

Clinical features included reduced central vision, difficulty passing from light to dark, and diffuse submacular and peripapillary deposits, which were hyperfluorescent by fluorescein angiography. Colour contrast thresholds were abnormal in all six patients studied and both pattern and focal electroretinograms were abnormal in five of six patients. The scotopic and mixed rod-cone single flash ERG was normal but two patients demonstrated reduced oscillatory potentials and one had borderline delayed 30 Hz responses. Scotopic thresholds were elevated and rod-mediated dark adaptation kinetics were markedly prolonged in all six patients when measured over the central visible confluent deposits.

CONCLUSIONS

In patients with EFEMP1 retinal dystrophy with confluent macular deposits, scotopic sensitivity is reduced and dark adaptation kinetics are prolonged over the macular deposits but are normal elsewhere. These results emphasize the localised nature of functional deficits in some patients with EFEMP1 retinal dystrophy and correlate well with the patient's visual symptoms. Symptomatic visual dysfunction may precede the development of clinically evident geographic atrophy or choroidal neovascularization in this disorder.

Autosomal dominant cone-rod dystrophy with mutations in the guanylate cyclase 2D gene encoding retinal guanylate cyclase-1

OBJECTIVE

To describe the phenotype in 4 families with dominantly inherited cone-rod dystrophy, 1 with an R838C mutation and 1 with an R838H mutation in the guanylate cyclase 2D (GUCY2D) gene encoding retinal guanylate cyclase-1.

METHODS

Psychophysical and electrophysiological evaluation and confocal laser scanning ophthalmoscopic imaging was performed on 10 affected members of 4 British families.

RESULTS

Although subjects had lifelong poor vision in bright light, a major reduction in visual acuity did not occur in most of them until after their late teens. Fundus abnormalities were confined to the central macula, and increasing central atrophy was noted with age. Increased background autofluorescence was observed surrounding the central atrophic area. Electrophysiological testing revealed a marked loss of cone function with only minimal rod involvement, even in older subjects. Photopic and scotopic static perimetry demonstrated central and peripheral cone-mediated threshold elevations with midperipheral sparing.

CONCLUSION

The phenotype associated with autosomal dominant cone-rod dystrophy with either an R838C or R838H mutation in GUCY2D is distinctive, with predominantly cone system involvement. There is some variation in severity within the 3 families with the R838C mutation.

CLINICAL RELEVANCE

Families with the R838C or R838H mutation have a much milder phenotype than the family previously described that had 2 sequence changes, E837D and R838S, in GUCY2D.

A human homolog of yeast pre-mRNA splicing gene, PRP31, underlies autosomal dominant retinitis pigmentosa on chromosome 19q13.4 (RP11)

We report mutations in a gene (PRPF31) homologous to Saccharomyces cerevisiae pre-mRNA splicing gene PRP31 in families with autosomal dominant retinitis pigmentosa linked to chromosome 19q13.4 (RP11; MIM 600138). A positional cloning approach supported by bioinformatics identified PRPF31 comprising 14 exons and encoding a protein of 499 amino acids. The level of sequence identity to the yeast PRP31 gene indicates that PRPF31 is also likely to be involved in pre-mRNA splicing. Mutations that include missense substitutions, deletions, and insertions have been identified in four RP11-linked families and three sporadic RP cases. The identification of mutations in a pre-mRNA splicing gene implicates defects in the splicing process as a novel mechanism of photoreceptor degeneration.

Outcome of cataract surgery in patients with retinitis pigmentosa

AIM

To determine the visual benefit of cataract extraction in patients with retinitis pigmentosa and to identify risk factors for poor outcome.

METHODS

A retrospective analysis was undertaken of a continuous series of 142 eyes of 89 patients with retinitis pigmentosa undergoing cataract surgery between 1985 and 1997.

RESULTS

Mean age at surgery was 47.5 years (range 24-81 years). In 100 eyes there was posterior subcapsular lens opacity alone, 37 eyes also had moderate nuclear sclerosis, and five had only nuclear sclerosis. All patients had central visual fields of <10 degrees. Overall, mean visual acuity improved from 1.05 (SD 0.38) preoperatively to 0.63 (SD 0.49) postoperatively on the logMAR scale. Significant postoperative capsular opacification occurred in 88/139 eyes (63%) and 45.1% required capsulotomy. Anterior capsulotomy was undertaken in 5/52 (9.6%) eyes undergoing phacoemulsification. Postoperative macular oedema was noted in 20 (14%) eyes. Visual acuity improved in 109 eyes (77%), was unchanged in 29 eyes (20.5%), and worsened after surgery in four eyes (2.5%). 86/89 patients reported major improvement of visual function.

CONCLUSIONS

Cataract surgery for relatively minor lens opacities is beneficial in patients with retinitis pigmentosa, and most report subjective improvement of visual symptoms. The incidence of capsular opacification is high and anterior capsular contraction may occur. The number of eyes with poor vision due to macular oedema was unexpectedly low.

Mutations in the pre-mRNA splicing factor gene PRPC8 in autosomal dominant retinitis pigmentosa (RP13)

Retinitis pigmentosa (RP) is a genetically heterogeneous disorder characterized by progressive degeneration of the peripheral retina leading to night blindness and loss of visual fields. With an incidence of approximately 1 in 4000, RP can be inherited in X-linked, autosomal dominant or autosomal recessive modes. The RP13 locus for autosomal dominant RP (adRP) was placed on chromosome 17p13.3 by linkage mapping in a large South African adRP family. Using a positional cloning and candidate gene strategy, we have identified seven different missense mutations in the splicing factor gene PRPC8 in adRP families. Three of the mutations cosegregate within three RP13 linked families including the original large South African pedigree, and four additional mutations have been identified in other unrelated adRP families. The seven mutations are clustered within a 14 codon stretch within the last exon of this large 7 kb transcript. The altered amino acid residues at the C-terminus exhibit a high degree of conservation across species as diverse as humans, Arabidopsis and trypanosome, suggesting that some functional significance is associated with this part of the protein. These mutations in this ubiquitous and highly conserved splicing factor offer compelling evidence for a novel pathway to retinal degeneration.

[Macular pigment and age-related macular degeneration]

The present concepts of the pathogenesis of AMD include cumulative light damage by oxidative processes in the macular photoreceptors as environmental co-factor for the development of AMD. The direct causative connection of this hypothesis has still to be established but wide circumstantial evidence from epidemiological and basic scientific investigations are strongly supportive. Macular pigment consisting of lutein and zeaxanthin through there ability to filter light and by direct antioxidative properties, has been proposed as the most effective protective factor in the central retina ("natural sun glasses") and could be important to reduce light induced oxidative retinal damage. The observation, that with age and especially in eyes with AMD lower concentrations of macular pigment could be found, can be interpreted that low macular pigment concentrations may be associated with higher risk for AMD. Through dietary intake and eventually with supplementation the concentration of macular pigment can be increased, and analysis of the correlation between macular pigment and AMD may be important to characterise a possible influenceable AMD risk factor.