Choroideremia Patients Research Articles

Chronically shortened rod outer segments accompany photoreceptor cell death in Choroideremia.

X-linked choroideremia (CHM) is a disease characterized by gradual retinal degeneration caused by loss of the Rab Escort Protein, REP1. Despite partial compensation by REP2 the disease is characterized by prenylation defects in multiple members of the Rab protein family that are master regulators of membrane traffic. Remarkably, the eye is the only organ affected in CHM patients, possibly because of the huge membrane traffic burden of the post mitotic photoreceptors, which synthesise outer segments, and the adjacent retinal pigment epithelium that degrades the spent portions each day. In this study, we aimed to identify defects in membrane traffic that might lead to photoreceptor cell death in CHM. In a heterozygous null female mouse model of CHM (Chmnull/WT), degeneration of the photoreceptor layer was clearly evident from increased numbers of TUNEL positive cells compared to age matched controls, small numbers of cells exhibiting signs of mitochondrial stress and greatly increased microglial infiltration. However, most rod photoreceptors exhibited remarkably normal morphology with well-formed outer segments and no discernible accumulation of transport vesicles in the inner segment. The major evidence of membrane trafficking defects was a shortening of rod outer segments that was evident at 2 months of age but remained constant over the period during which the cells die. A decrease in rhodopsin density found in the outer segment may underlie the outer segment shortening but does not lead to rhodopsin accumulation in the inner segment. Our data argue against defects in rhodopsin transport or outer segment renewal as triggers of cell death in CHM.

Genetic defects of CHM and visual acuity outcome in 24 choroideremia patients from 16 Japanese families

Choroideremia (CHM) is an incurable progressive chorioretinal dystrophy. Little is known about the natural disease course of visual acuity in the Japanese population. We aimed to investigate the genetic spectrum of the CHM gene and visual acuity outcomes in 24 CHM patients from 16 Japanese families. We measured decimal best-corrected visual acuity (BCVA) at presentation and follow-up, converted to logMAR units for statistical analysis. Sanger and/or whole-exome sequencing were performed to identify pathogenic CHM variants/deletions. The median age at presentation was 37.0 years (range, 5–76 years). The mean follow-up interval was 8.2 years. BCVA of the better-seeing eye at presentation was significantly worsened with increasing age (r = 0.515, p < 0.01), with a high rate of BCVA decline in patients > 40 years old. A Kaplan–Meier survival curve suggested that a BCVA of Snellen equivalent 20/40 at follow-up remains until the fifties. Fourteen pathogenic variants, 6 of which were novel [c.49 + 5G > A, c.116 + 5G > A, p.(Gly176Glu, Glu177Ter), p.Tyr531Ter, an exon 2 deletion, and a 5.0-Mb deletion], were identified in 15 families. No variant was found in one family only. Our BCVA outcome data are useful for predicting visual prognosis and determining the timing of intervention in Japanese patients with CHM variants.

CHOROIDAL VASCULARITY INDEX IN YOUNG CHOROIDEREMIA PATIENTS.

To evaluate choroidal features in young patients affected by choroideremia (CHM). Young CHM patients and control subjects were recruited at the Eye Clinic in Florence. High-resolution choroidal imaging was obtained using swept-source optical coherence tomography with long optical coherence tomography scans (12 × 9 mm optical coherence tomography scans). We considered the subfoveal choroidal area within 9 mm of the optic disk in the horizontal plane and the subfoveal choroidal area within a 3-mm diameter centered over the fovea. The subfoveal choroidal thickness, total choroidal area, luminal area, stromal area, and choroidal vascularity index were assessed using the "ImageJ" software in both groups. Eight patients (16 eyes; mean age, 19.3 ± 5.2 years) and seven control subjects (14 eyes; mean age, 19.0 ± 5.0 years) were included in this study. Best-corrected visual acuity was 20/20 in both eyes of seven CHM patients and in all control subjects and 20/25 in both eyes in one CHM patient. Mean subfoveal choroidal thickness did not differ between CHM patients and control subjects. Luminal area9mm, stromal area9mm, and total choroidal area9mm were reduced in patients compared with the control group. Luminal area3mm, stromal area3mm, and total choroidal area3mm did not differ between patients and control subjects. Choroidal vascularity index9mm and choroidal vascularity index3mm were not different between patients and control subjects. There are no differences in the choroidal vascularity index between young CHM patients and control subjects; this result suggests a simultaneous, proportional impairment of both the stromal and vascular components of the choroid in the early stages of the disease.

Quantification of RPE Changes in Choroideremia Using a Photoshop-Based Method.

PurposeTo develop a reliable and efficient method for quantifying the area of preserved retinal pigment epithelium (RPE), facilitating the evaluation of disease progression or response to therapy in choroideremia (CHM).MethodsThe fundus autofluorescence images of CHM patients were captured at baseline and 1 year. A Photoshop-based method was developed to allow the reliable measurement of the RPE area. The results were compared with measurements generated by the Heidelberg Eye Explorer 2 (HEYEX2). The areas measured by two independent graders were compared to assess the test–retest reliability.ResultsBy using the Photoshop-based method, the area of the RPE measured from 64 eyes was seen to decrease significantly (P < 0.001) at a rate of 2.57 ± 3.22 mm2 annually, and a percentage of 8.39% ± 5.24%. The average standard deviations for Photoshop were less than that for HEYEX2 (0.5–1.1 in grader 1; 0.4–1.6 in grader 2), indicating less intragrader variability. The RPE decrease as determined by the Photoshop-based method showed excellent reliability with an intraclass correlation coefficient of 0.944 (95% confidence interval, 0.907–0.966). In Bland-Altman plots, the Photoshop method also exhibited better intergrader agreement.ConclusionsPhotoshop-based quantification of preserved RPE area in patients with CHM is feasible and has better test–retest reliability compared with the HEYEX2 method.Translational RelevanceAn accurate quantification method for longitudinal RPE change in CHM patients is an important tool for the evaluation of efficacy in any therapeutic trials.

Prospective deep phenotyping of choroideremia patients using multimodal structure-function approaches

ObjectiveTo investigate the retinal changes in choroideremia (CHM) patients to determine correlations between age, structure and function.Subjects/MethodsTwenty-six eyes from 13 male CHM patients were included in this prospective longitudinal study. Participants were divided into <50-year (n = 8) and ≥50-year (n = 5) old groups. Patients were seen at baseline, 6-month, and 1-year visits. Optical coherence tomography (OCT), OCT angiography, and fundus autofluorescence were performed to measure central foveal (CFT) and subfoveal choroidal thickness (SCT), as well as areas of preserved choriocapillaris (CC), ellipsoid zone (EZ), and autofluorescence (PAF). Patients also underwent functional investigations including visual acuity (VA), contrast sensitivity (CS), colour testing, microperimetry, dark adaptometry, and handheld electroretinogram (ERG). Vision-related quality-of-life was assessed by using the NEI-VFQ-25 questionnaire.ResultsOver the 1-year follow-up period, progressive loss was detected in SCT, EZ, CC, PAF, and CFT. Those ≥50-years exhibited more structural and functional defects with SCT, EZ, CC, and PAF showing strong correlation with patient age (rho ≤ −0.47, p ≤ 0.02). CS and VA did not change over the year, but CS was significantly correlated with age (rho = −0.63, p = 0.001). Delayed to unmeasurable dark adaptation, decreased colour discrimination and no detectable ERG activity were observed in all patients. Minimal functional deterioration was observed over one year with a general trend of slower progression in the ≥50-years group.ConclusionsQuantitative structural parameters including SCT, CC, EZ, and PAF are most useful for disease monitoring in CHM. Extended follow-up studies are required to determine longitudinal functional changes.

HYPERREFLECTIVE FOCI AS A PATHOGENETIC BIOMARKER IN CHOROIDEREMIA.

To assess hyperreflective foci (HF) number and distribution in choroideremia (CHM) using spectral domain optical coherence tomography. Observational, cross-sectional case series. Consecutive patients and matched controls (20 eyes each) underwent best-corrected visual acuity measurement, fundoscopy, blue-light autofluorescence (BL-FAF) and spectral domain optical coherence tomography. Hyperreflective foci were assessed on a horizontal spectral domain optical coherence tomography scan, in the 500-µm area centered on the umbo, and in the 500-μm-wide areas internal (preserved border) and external (pathologic border) to the chorioretinal atrophy of CHM patients, and in the parafovea of controls. Hyperreflective foci were subclassified as retinal or choroidal. The spared central islet was measured on BL-FAF. Primary outcome was HF quantification in CHM. Secondary outcomes included their relationships with atrophy extent. Choroideremia eyes disclosed a significantly higher HF number across the pathologic border and in the fovea when compared with controls; in particular, these HF were primarily located in the choroid (59-87%). Moreover, choroidal HF in the pathologic border inversely correlated with the area of the preserved central islet. Hyperreflective foci might turn out to be a potential biomarker of CHM activity or severity. In this regard, we hypothesize that HF may be related to macrophages activation or progressive retinal pigment epithelium degeneration.

Cone Structure Persists Beyond Margins of Short-Wavelength Autofluorescence in Choroideremia.

PurposeWe studied the relationship between structure and function of the choriocapillaris (CC), retinal pigment epithelium (RPE), and photoreceptors in patients with choroideremia (CHM).MethodsSix CHM patients (12 eyes) and four normal subjects (six eyes) were studied with fundus-guided microperimetry, confocal and nonconfocal adaptive optics scanning laser ophthalmoscopy (AOSLO), near-infrared and color fundus photos, short wavelength fundus autofluorescence (SW-AF), and swept-source optical coherence tomography (SS-OCT) and angiography (SS-OCTA) images. Cone spacing was represented using Z-scores (standard deviations from the mean at that eccentricity). CC flow voids were defined using a threshold of 1 SD below the normal mean.ResultsCone spacing Z-scores were not significantly correlated with distance from the borders of preserved RPE, determined using either the SS-OCT or SW-AF scans. Cone spacing Z-scores were significantly correlated with CC flow voids and retinal sensitivity. Flow voids were abnormal in regions of preserved RPE and increased progressively from within −2° of the preserved area to +2° beyond the border. Visual sensitivity decreased as CC flow voids increased approaching and beyond the border of preserved structure.ConclusionsIn CHM, cone spacing Z-scores correlated with CC flow voids, and were negatively correlated with retinal sensitivity, suggesting cone degeneration accompanied reduced CC perfusion. Functional cones were found outside the presumed borders of preserved outer-retina/RPE as defined by SW-AF, but not outside the borders determined by SS-OCT. The use of SW-AF to identify the border of preserved structures may underestimate regions with cells that may be amenable to treatment.

Optical coherence tomography (OCT) features of cystoid spaces in choroideremia (CHM).

To investigate the prevalence and features of cystoid spaces (CS) in patients with confirmed genetic diagnosis of choroideremia (CHM) using swept source optical coherence tomography (OCT). We retrospectively reviewed CHM patients examined at the Regional Reference Center for Hereditary Retinal Degenerations at the Eye Clinic in Florence. We took into consideration genetically confirmed CHM patients with ophthalmological and swept source optical coherence tomography (OCT) examinations. The presence/absence and location of cystoid spaces in the retina of each eye were reported. A total of 42 eyes of 21 CHM patients were included in our series. The average age of the patients was 36.5 ± 20.1 (range, 13-73 years). The average best-corrected visual acuity (BCVA) for all patients was 0.63 ± 1.00 logMar (range, 0-2,80). CS were present in 15 eyes of eight patients (8/21, 38%). In all cases, CS were located in inner nuclear layer (INL); in five eyes of three patients, CS were detected also in ganglion cell layer (GCL). CS appeared as microcistoyd abnormalities and were detected in retinal areas characterized by retinal pigment epithelium (RPE) and outer retinal layers atrophy at the transition zone. Cystoid spaces in choroideremia showed peculiar features; they are clusters of small-size extrafoveal degenerative cysts mainly located in inner nuclear layer at the transition zone where outer retinal layers and RPE are severely damaged.

Peculiar Clinical Findings in Young Choroideremia Patients: A Retrospective Case Review

Purpose: To report peculiar clinical findings in young choroideremia (CHM) patients. Methods: We retrospectively reviewed young (age <20 years at the first evaluation) CHM patients examined at the Regional Reference Center for Hereditary Retinal Degenerations at the Eye Clinic in Florence between 2012 and 2018. We took into consideration patients with ophthalmological examinations, fundus color photographs, fundus autofluorescence (FAF) images, optical coherence tomography (OCT) scans, full-field electroretinograms, and Goldmann visual fields. Results: In our series, we studied 8 young CHM patients (average age 13.8 years, median age 12.5, range 10–20) for a total of 16 eyes. Visual acuity (VA) was 20/20 in 7 patients and 20/25 in both eyes of 1 patient. We identified a peculiar central FAF pattern (detectable in 3 patients), characterized by reduced central hypo-autofluorescence. Long OCT scans showed different forms of parapapillary retinal involvement from the mildest to the most severe form when the macula is still preserved. In 3 patients, at the time of atrophic changes at the posterior pole, it was possible to detect a progressive reduction of foveal pigmentation during follow-up. We found mutations of the CHM gene in all 6 patients who had been screened. Conclusions: CHM is a progressive retinal disorder which involves both the peripheral and the central retina. Using a multimodal imaging approach, we described peculiar central abnormalities underlying the early involvement of the central retina in young CHM patients with a good VA.

Spectrum of Disease Severity and Phenotype in Choroideremia Carriers

To characterize and bring awareness to the disease spectrum of female choroideremia patients, as severity can vary from mild to severe disease, comparable to that observed in male patients. Retrospective cohort study. Twelve female carriers of disease-causing variants in the CHM gene confirmed by molecular genetic sequencing were characterized clinically and imaged with short-wave fundus autofluorescence (SW-FAF), spectral-domain optical coherence tomography (OCT), and color fundus imaging. Twelve unrelated female patients with a clinical and genetic diagnosis of choroideremia carriers were included in this study. Disease severity among these phenotypes ranged from mild to severe, resembling the typical presentation of choroideremia in male patients. Mild disease presented with retinal pigment epithelium mottling, a patchy pattern of hypoautofluorescent speckles on SW-FAF, and intact retinal layers on spectral-domain OCT. Severe disease presented with widespread chorioretinal atrophy as shown by SW-FAF and spectral-domain OCT. Each of the identified genetic variants in CHM was predicted to be disease-causing according to insilico prediction software. Disease progression analysis of 4 patients with follow-up showed a decline in visual acuity for 2 patients, with progression observed on spectral-domain OCT in 1 of the patients. No significant disease progression on SW-FAF was observed for any of the patients. Female carriers of choroideremia can present with a wide range of clinical phenotypes and disease severity, from mild to severe disease, similar to male subjects. Symptomatic female subjects should be considered for current and upcoming gene replacement therapy clinical trials.

Visual Function at the Atrophic Border in Choroideremia Assessed with Adaptive Optics Microperimetry

Recent advances in retinal imaging allow visualization of structural abnormalities in retinal disease at the cellular level. This study used adaptive optics (AO) microperimetry to assess visual sensitivity with high spatial precision and to examine how function varies across 2 phenotypic features observed in choroideremia: atrophic lesion borders and outer retinal tubulations (ORTs). Cross-sectional study. Twelve choroideremia patients. A custom AO scanning light ophthalmoscope (AOSLO) equipped with both confocal and nonconfocalsplit-detection imaging methods was used to image the photoreceptor inner and outer segment mosaics. For AO microperimetry, circular 550-nm stimuli were presented through the AOSLO system; stimuli were either 9.6 or 38.3 arcmin2 (approximately 60 or 15 times smaller than a Goldman III stimulus). Test locations were identified in structural images and stimuli were targeted to these locations using real-time retinal tracking combined with measurements of transverse chromatic aberration. Psychophysical detection thresholds were measured at the atrophic border in 12 patients. Additionally, visual sensitivity was probed along ORTs in 4patients. Visual sensitivity thresholds measured with AO microperimetry at retinal locations corresponding to structural phenotypes observed on AOSLO retinal images. In choroideremia, sharp borders between intact central islands of the photoreceptor mosaic and complete atrophy of the outer retina and retinal pigment epithelium were observed in both split-detection and confocal structural images. Adaptive optics microperimetry at locations spanning these borders showed a commensurately sharp decrease in function, with readily measurable visual sensitivity on one side and dense scotoma on the other. These functional transitions often occurred over a distance smaller than the diameter of the Goldman III stimulus. Thresholds measured along ORTs showed dense scotoma over the tubule in all 4 participants, despite the visibility of remnant cone inner segments on the AO images. Choroideremia patients exhibited sharp functional transitions that collocated with structural transitions from intact to severely degenerated retina. We found no evidence of visual sensitivity over ORTs. Measuring cone function with high resolution offered insight into disease mechanisms and may enable precise assessment of whether experimental therapies, such as gene therapy, provide a functional benefit.

CHM/REP1 Transcript Expression and Loss of Visual Function in Patients Affected by Choroideremia.

To evaluate the disease progression in patients with clinical and genetic diagnoses of choroideremia during a long-term follow-up and to investigate the relationship between pathogenic variants in the CHM/REP1 gene and disease phenotypes. We performed a retrospective longitudinal study on 51 affected men by reviewing medical charts at baseline and follow-up visits to extract the following ocular findings: best-corrected visual acuity, Goldmann visual field, optical coherence tomography, microperimetry. Data obtained from the analysis of DNA and mRNA were reevaluated for genetic classification of patients. The longitudinal analysis showed a significant (P < 0.001) worsening of best-corrected visual acuity with a mean rate of 0.011 logMar per year before 50 years and 0.025 logMar per year after 50 years. Similarly, V4e Goldmann visual field area significantly (P ≤ 0.01) decreased at a mean rate of 2.7% per year before 40 years and 5.7% after 40 years. Moreover, we observed a significant (P < 0.05) decrease of macular sensitivity with a mean rate of 5.0% per year and a decrease of mean macular thickness with a mean rate of 0.8% per year. We classified our patients into two groups according to the expression of the CHM/REP1 gene transcript and observed that mutations leading to mRNA absence are associated with an earlier best-corrected visual acuity and Goldmann visual field loss. Our analysis of morphological and functional parameters in choroideremia patients showed a slow disease progression, particularly in the first decades of life. Overall, reevaluation of clinical and molecular data suggests exploring the genotype-phenotype relationship based on CHM/REP1 transcript expression.

A detailed invivo analysis of the retinal nerve fibre layer in choroideremia.

Choroideremia is a currently incurable X-linked recessive retinal degeneration that leads to blindness. Gene therapy approaches to date target the outer retinal layers. However, the choroideremia (CHM) gene is expressed in all retinal layers, and a previous study on a small cohort of choroideremia patients suggested possible thinning of the retinal nerve fibre layer (RNFL). The purpose of the study was to examine the RNFL in detail using advanced imaging techniques in a larger cohort of choroideremia patients. Spectral domain optical coherence tomography of the peripapillary RNFL acquired with the Heidelberg Spectralis HRA circular scan mode were analysed retrospectively in 41 eyes of 21 choroideremia patients aged 39.6years (±3.7 SEM). As age-matched controls, 20 eyes from 10 patients with retinitis pigmentosa and 56 eyes from 28 healthy individuals were also assessed. Automated RNFL segmentation was adjusted manually to precisely delineate the RNFL. The data were also compared against an external normative database. Mean peripapillary RNFL thickness in choroideremia was 130±3μm in the right eye (OD) and 133±3μm in the left eye (OS). This was 24% and 27% thicker than RNFL thickness in the controls (p<0.001 for both). Patients with retinitis pigmentosa also showed an increase in RNFL thickness, which was no different to the choroideremia cohort (p>0.05). Compared with manual analysis, the automated function of the inbuilt software was consistently inaccurate in segmenting the RNFL in choroideremia. The RNFL is significantly thicker in choroideremia compared with age-matched normal controls, which was similar to what was seen in retinitis pigmentosa.

Near-Infrared Autofluorescence in Choroideremia: Anatomic and Functional Correlations

To investigate near-infrared fundus autofluorescence (NIR-AF) characteristics in patients with choroideremia and to correlate these with anatomic and functional parameters. Retrospective, observational case series. In this multicenter study, 43 consecutive choroideremia patients (79 eyes) underwent multimodal retinal imaging, including near-infrared fundus autofluorescence (NIR-AF), blue autofluorescence (B-AF), optical coherence tomography (OCT), fundus photography, and functional testing including fundus-controlled microperimetry. All eyes could be categorized into 3 groups based on patterns of NIR-AF over the island of surviving retinal pigment epithelium: Group 1 (preserved NIR-AF centrally), Group 2 (only disrupted NIR-AF), or Group 3 (absence of NIR-AF). Group 1 eyes showed areas of NIR-AF that matched the areas of B-AF islands (R2= 0.94, slope 0.84 ± 0.04) while Group 2 eyes showed significantly smaller areas of NIR-AF compared with B-AF (R2= 0.08; slope 0.02 ± 0.01). The 3 groups differed significantly in terms of residual B-AF island size (P < .0001), length of foveal ellipsoid zone (P= .03), foveal thickness (P=.04), and foveal sensitivity (P= .01). Visual acuity (P= .07) and central retinal thickness (P= .06) did not differ statistically. The length of the ellipsoid zone line was similar to the horizontal diameter of NIR-AF in Group 1 (R2= 0.97, slope 0.96 ± 0.04), while Group 2 eyes showedbroader ellipsoid zone than NIR-AF (R2= 0.60, slope 0.19 ± 0.03). Choroideremia patients can be stratified into 3 groups based on NIR-AF imaging, which showed morphologic and functional changes correlating with different stages of retinal pigment epithelium degeneration. NIR-AF could be a marker for disease staging in choroideremia, and could be used for patient selection or as an outcome parameter in interventional trials.

Beneficial effects on vision in patients undergoing retinal gene therapy for choroideremia.

Retinal gene therapy is increasingly recognized as a novel molecular intervention that has huge potential in treating common causes of blindness, the majority of which have a genetic aetiology1-5. Choroideremia is a chronic X-linked retinal degeneration that was first described in 18726. It leads to progressive blindness due to deficiency of Rab-escort protein 1 (REP1). We designed an adeno-associated viral vector to express REP1 and assessed it in a gene therapy clinical trial by subretinal injection in 14 patients with choroideremia. The primary endpoint was vision change in treated eyes 2 years after surgery compared to unoperated fellow eyes. Despite complications in two patients, visual acuity improved in the 14 treated eyes over controls (median 4.5 letter gain, versus 1.5 letter loss, P = 0.04), with 6 treated eyes gaining more than one line of vision (>5 letters). The results suggest that retinal gene therapy can sustain and improve visual acuity in a cohort of predominantly late-stage choroideremia patients in whom rapid visual acuity loss would ordinarily be predicted.

Crystals and Fatty Acid Abnormalities Are Not Present in Circulating Cells From Choroideremia Patients.

To confirm whether choroideremia (CHM) is a systemic disease characterized by blood lipid abnormalities and crystals found in, or associated with, circulating peripheral blood cells of patients. Peripheral blood samples obtained from three subjects with confirmed mutations in the CHM gene and three age-matched normal controls were processed for transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Fatty acids from plasma of nine male CHM subjects were analyzed and compared to reference values for a sample from a Canadian population. Intracellular crystals were not observed in the cells from choroideremia-affected males. No crystals were found adherent to the external plasma membrane of red blood cells. Fatty acid profiles of patients were similar to reference values, with the exception of lower levels of nervonic acid. This investigation failed to observe crystals previously reported in peripheral circulating blood cells derived from CHM subjects, and showed no significant fatty acid abnormalities, not supporting the view of CHM as a systemic disease.

Study of natural history of Chinese patients with choroideremia

Objective To provide detailed clinical and molecular genetic findings and describe the characteristics of natural history in Chinese choroideremia (CHM) patients. Methods The patients with CHM who met the inclusion criteria of at least two visits over a minimum period of 5 years were recruited on a voluntary basis at the Ophthalmic Genetics Clinic in Peking Union Medical College Hospital from April 2009 to August 2017.Molecular genetic analysis results, best-corrected visual acuity (BCVA), color fundus photograph, optical coherence tomography (OCT), visual field (VF), full-field electroretinography (fERG) were obtained.This study protocol was approved by the Institutional Review Board of Peking Union Medical College Hospital (S-K125). Written informed consent was obtained from each participant. Results Ten Chinese Han patients from seven CHM families were included.The mutations were confirmed by molecular genetic analysis, and two novel mutations were found.The median age of 10 patients at first visit was 44 years (range 8-52 years). The mean first-last visit period was 6.08 years (range 5.03-7.24 years). The mean BCVA at first visit in logMAR equivalents was 0.56 (range 0.0-2.0) or approximately 0.28 decimal acuity.The correlation between BCVA at first visit and age showed that relative good vision remained until 35 years old and BCVA subsequently reduced rapidly.OCT showed a thickening of the central retinal thickness at early stage, followed by a thinning over decades.Outer retinal tabulation (ORT) was shown in some patients.There was a strong negative correlation (r=-0.861, P<0.001) between residual VF and age.Five patients did not need to record fERG because of serious fundus lesions.Two patients exhibited decreased amplitudes for both rod and cone-driven responses, and three patients exhibited no fERG amplitudes. Conclusions The progression of CHM may be severer and faster in Chinese patients than that in Western patients.ORT is an important manifestation of OCT in CHM patients.VF and fERG are applicable to evaluate the condition of very-early phase of CHM. Key words: Choroideremia; Gene; Visual acuity; Optical coherence tomography; Visual field; Electroretinography

Colour discrimination ellipses in choroideremia.

The purpose of this study was to characterise alterations in colour discrimination in a cohort of patients with choroideremia prior to gene therapy, using a test previously validated for use in patients with retinal dystrophies. We tested 20 eyes of 10 patients with a diagnosis of choroideremia and an age-matched cohort of 10 eyes of 10 normal controls using the "Cambridge Colour Test" (CCT), in which subjects are required to distinguish the gap in a C presented in one of 4 orientations in a Stilling-type array. Colour discrimination was probed along eight axes in the CIE L*u*v* colour space, and the resulting data were plotted in the CIE 1976 chromaticity diagram and fitted with least-squares ellipses. Subsequently, we estimated the achromatic area for each subject by calculating the area of the resultant discrimination ellipse and calculated sensitivity thresholds along relevant colour confusion axes. Colour discrimination-as quantified by log10 of the ellipse area expressed in square 1/1000th2 units in CIE 1976-was 2.26 (range 1.82 to 2.67) for normal subjects and 3.85 (range 2.35 to 5.41) for choroideremia patients. There was a statistically significant correlation between both achromatic area and red-green colour discrimination at the CCT and BCVA, and to a lesser degree between blue colour discrimination at the CCT and BCVA. The majority of ellipses in choroideremia were aligned close to the tritan axis, and loss of sensitivity was significantly larger in the tritan direction than in the red-green. The majority of our patients demonstrated greater loss in tritan discrimination than in red-green colour discrimination using the CCT. There was a significant correlation between achromatic area and BCVA. In keeping with our current understanding of the machinery of colour vision, there was a significant correlation between BCVA and colour discrimination thresholds, which was stronger for red-green colour discrimination, than for tritan colour discrimination. We propose that this and similar tests of colour discrimination may prove to be suitable tools for assessing functional outcomes in gene therapy trials for choroideremia.

High resolution imaging analysis of female carriers and patients of Choroideremia with CHM gene mutation

PurposeTo report the high resolution imaging features of Japanese patient and female carriers of choroideremia using adaptive optics(AO) and other imaging modalities.MethodsThree carriers and one patient underwent comprehensive examinations including AO fundus camera (rtx1™ Imagine eyes, France), spectral domain optical coherence topography (SD‐OCT)and fundus autofluoresence (FAF). Cone density was measured by peak density method and compared with the data of 34 normal controls. The mutation analysis of the CHM gene was performed by Sanger sequencing. The protocol conformed to the tenets of the Declaration of Helsinki and was approved by the IRB of The Jikei University and Nippon Medical School.ResultsThree female carriers 1, 2, 3 (sister 9 y.o, mother 37 y.o and grandmother 65 y.o) and one patient (6 y.o, male). They had same CHM mutation, c.646delA, p.T216LfsX16. All carriers did not complain any symptoms, the BCVA of all were over 20/20. Fundus examination of carrier 2 showed mild generation in only periphery, the other carriers showed diffuse degeneration. AF showed mottled hypo‐autofluoresence in degeneration area. SD‐OCT of the carriers showed nearly normal,although peripheral SD‐OCT and patient showed diffuse disruptions of interdigitation and ellipsoid zones.Cone density was measured at 2 to 8 degree temporal from the fovea in every 1 degree, using 50 x 50 micron images. Cone counting was performed by AO detect (Imagine eyes) with manual correction. Patient showed lower cone density more than 2 SD of normal control. The carriers showed lower cone density only at 7 and 8 degrees.ConclusionsAO cone counting showed reduction of photoreceptors in carriers mainly at peripheral region. To elucidate the mechanism of peripheral degeneration and foveal sparing of female carriers may help preventing the disease progression of choroideremia patients.

Rep1 copy number variation is an important genetic cause of choroideremia in Chinese patients

Choroidermia (CHM) is an X-linked chorioretinal disorder caused by mutations in the Rab Escort Protein 1 (Rep-1) gene. Its diagnosis depends on clinical findings and genetic confirmation; however, mutations in Rep-1 gene are not always detected by standard Sanger sequencing. We therefore conducted multiplex ligation-dependent probe amplification (MLPA) and real-time quantitative PCR (QPCR) in cases of Chinese CHM families in which sequencing all the exons and flanking intronic regions of the CHM gene had not identified a mutation or exons could not be amplified. We hypothesized that copy number variation (CNV) within the Rep-1 gene would explain the etiology of choroideremia in these patients. In the eight unrelated families, exon deletions or duplications were detected by MLPA and QPCR in five. Our results showed CNV within the Rep-1 gene could be an important contributor in Chinese CHM patients. Sequencing of the Rep-1 gene supplemented with MLPA is therefore an important diagnostic strategy in choroideremia patients.