Relationship between napping and melatonin in the blind

Daytime sleepiness is a common complaint in blind subjects. Abnormally timed melatonin has been invoked as a possible cause of both daytime sleepiness and nighttime awakening. In free-running blind individuals, there is an opportunity to assess the relationship between endogenous melatonin rhythms and subjective sleepiness and naps. The aim of this study was to characterize melatonin rhythms and simultaneously to evaluate subjective napping. A total of 15 subjects with no conscious light perception (NPL) were studied for 1 month. Prior to the study, sleep disorders were assessed using the Pittsburgh Sleep Quality Index. Cosinor and regression analysis revealed that 9 of the 15 NPL subjects had free-running 6-sulphatoxymelatonin (aMT6s) rhythms (period [tau] range = 24.34 to 24.79 h), 3 were entrained with an abnormal phase, and 3 were normally entrained. Most of the subjects (13 of 15) had daytime naps; the 2 individuals who did not made conscious efforts not to do so. Subjects with abnormal aMT6s rhythms had more naps of a longer duration than did those with normal rhythms. Free-running nap rhythms occurred only in subjects with free-running aMT6s rhythms. The 2 abnormally entrained subjects who napped did so at times that coincided with high levels of aMT6s (mean aMT6s acrophase [phi] +/- SD = 14.30 +/- 1.08 h, 20.30 +/- 0.62 h; mean nap time +/- SD = 14.01 +/- 3.60 h, 18.23 +/- 3.20 h, respectively). Regardless of aMT6s rhythm abnormality, significantly more naps occurred with a 4-h period before and after the estimated aMT6s acrophase. In 4 free-running subjects, aMT6s acrophase (phi) passed through an entire 24-h period. When aMT6s was in a normal phase position (24:00 to 06:00 h), night-sleep duration tended to increase with a significant reduction in the number and duration of naps. Sleep onset and offset times tended to advance and delay as the aMT6s rhythms advanced and delayed. Our results show a striking relationship between the timing of daytime production of melatonin and the timing of daytime naps. This suggests that abnormally timed endogenous melatonin may induce sleepiness in blind subjects.

Ocular ultrasound in Alagille syndrome: a new sign

BACKGROUND

Alagille syndrome (AS) is one of six forms of familial intrahepatic cholestasis, all of which present with neonatal jaundice and paucity of intrahepatic bile ducts. Differentiation of these individual syndromes is crucial as their treatments and prognoses vary. It is the ophthalmic features, posterior embryotoxon on particular, that distinguish AS.

METHODS

The authors performed full ocular examination, including A- and B-scan ultrasound, refraction, and, where possible, fluorescein angiography in 20 unrelated children with AS and 8 with non-AS-related cholestasis.

RESULTS

There was ultrasound evidence of optic disc drusen in at least one eye in 95% and bilateral disc drusen in 80% of patients with AS but in none of the patients who were non-AS at the time of examination. Independent review of hard-copy scans suggested drusen in at least one eye in 90% of the cases and bilateral drusen in 50%, although this latter figure rose to 65% on review of the angiograms. This is markedly higher than the incidence in the normal population (0.3%-2%). Axial lengths were shorter than expected for the older age group (older than 10 years of age), but this was not associated with gross ametropia.

CONCLUSION

This strong association of AS and optic disc drusen has not been reported previously and represents not only the first significant association between a systemic condition and disc drusen but also a possibly useful tool in the diagnosis of AS, especially in young children.

A randomised prospective study of outpatient haemodilution for central retinal vein obstruction

PURPOSE

Central retinal vein obstruction (CRVO) has significant visual morbidity. We prospectively evaluated an outpatient haemodilution (HD) regimen for CRVO.

METHODS

We recruited 59 patients with CRVO of less than three months' duration and visual acuity (VA) worse than or equal to 6/9.5. Thirty patients underwent HD (packed cell volume of <0.35, 12 weeks); there were 29 controls and follow-up was for six months.

RESULTS

Incidence rates for VA improvement (P = 0.708) and rubeosis iridis (P = 0.619) between the two groups were not different. The incidence rate of VA deterioration was 5.315 times higher with HD (P = 0.035, Cox Proportional analysis).

CONCLUSION

This data does not support the previous studies on haemodilution.

Partial laser ablation of massive peripapillary subretinal neovascularization

BACKGROUND

Although peripapillary subretinal neovascular membranes (PSRNs) are less common and often larger than neovascular complexes arising near the fovea, they may lead to severe visual loss. Very large (massive) PSRNs (MPSRNs) are 3.5 disc areas or greater in overall size, are even less common, and may contain a significant occult component, leading to slow and unpredictable growth. Such massive lesions may begin at the nasal margin of the disc and do not become symptomatic until they have extended around the disc toward the macula, threatening central vision. Although complete laser ablation has been used for symptomatic PSRNs with variable success, the optimal treatment of MPSRNs remains controversial.

METHODS

The authors reviewed the clinical course of 12 eyes of seven patients with MPSRNs. Ten eyes received laser treatment, which was limited to the temporal portion of the subretinal neovascular complexes only and two received no treatment.

RESULTS

Of the ten eyes receiving laser treatment, six showed stabilization of visual acuity, whereas in four the neovascular membrane progressed beneath the fovea with severe visual loss. In the two untreated eyes, the subretinal neovascular membrane progressed beneath the macula with the loss of central vision.

CONCLUSIONS

In contrast to the small symptomatic PSRNs, which are usually treated by complete laser ablation, MPSRNs may stabilize with only partial laser treatment. However, both types of lesions may remain stable for long periods of time without any treatment and require treatment only if progression toward the fovea occurs.

The venous closing pressure in central retinal vein obstruction

OBJECTIVE

To assess the rate of change in the central retinal venous closing pressure in central retinal vein obstruction over time, and its relationship to visual acuity improvement and the development of rubeosis iridis.

METHODS

Fifty patients presenting with central retinal vein obstruction of less than three months' duration, between the ages of 40 and 80 years, were reviewed prospectively. The central retinal venous closing pressure was measured by digital ocular compression. Patients were discharged from the study after the six-month visit.

RESULTS

All patients had elevated venous closing pressure at presentation, whereas at six months only 24 patients had persistent elevation. Of 16 patients with lowering of the venous closing pressure within four months of onset of central retinal vein obstruction, 11 (69%) had two or more lines of visual acuity improvement. Only two of 10 patients (20%) developing lowering of the venous closing pressure thereafter had visual improvement. No patient developed rubeosis iridis after the venous closing pressure lowered.

CONCLUSION

The central retinal venous closing pressure is raised in central retinal vein obstruction to about central retinal arterial diastolic pressure, and is its pathognomonic sign. This sign is easily elicited via digital pressure on the eyelid, and has prognostic significance for visual acuity improvement and the development of rubeosis iridis.

The gene responsible for autosomal dominant Doyne's honeycomb retinal dystrophy (DHRD) maps to chromosome 2p16

Degeneration in the macula region of the retina is a feature of a heterogeneous group of inherited, progressive disorders, causing blinding visual impairment. Autosomal dominant Doyne's honeycomb retinal dystrophy (DHRD) is characterised by the presence of drusen deposits at the level of Bruch's membrane in the macula and around the edge of the optic nerve head. We have studied 63 members of a large, nine-generation British pedigree by linkage analysis. Two-point analysis showed significant linkage to nine markers on the short arm of chromosome 2, a region overlapping that recently reported to be linked to Malattia leventinese. A maximum lod score (Zmax) of 7.29 (theta = 0.0) was obtained at marker locus D2S2251. Haplotype analysis of recombination events localised the disease to a 5 cM region between marker loci D2S2316 and D2S378. Striking clinical similarities between DHRD and the more common condition age-related macular degeneration (ARMD) suggest that the disease gene at this locus could be considered as the most likely candidate in future studies on ARMD.

A new family linked to the RP13 locus for autosomal dominant retinitis pigmentosa on distal 17p

A form of autosomal dominant retinitis pigmentosa (ADRP) mapping to chromosome 17p has been reported in a single large South African family. We now report a new family with severe early onset ADRP which maps to 17p. Linkage and haplotype analysis in this family places the ADRP locus in the 5 cM interval between markers AFMc024za5 and D17S1845, confirming the data obtained in the South African family. The discovery of a second 17p linked family may imply that this is one of the more common loci for dominant RP. In addition, the confirmation of an RP diagnosis at this locus is of interest since loci for a dominant cone dystrophy and Leber's congenital amaurosis (LCA1) have recently been linked to the same markers. While the cone dystrophy locus may be allelic with RP, our data and that of Goliath et al show that distinct genes are responsible for dominant RP and Leber's congenital amaurosis on chromosome 17p.

Clinical features of progressive bifocal chorioretinal atrophy: a retinal dystrophy linked to chromosome 6q

PURPOSE

The gene for progressive bifocal chorioretinal atrophy (PBCRA) has been linked to chromosome 6q, near the genomic assignment for North Carolina macular dystrophy. A study was undertaken to define the clinical features of a large PBCRA pedigree and to determine whether PBCRA and North Carolina macular dystrophy are phenotypically distinct entities.

METHODS

Fifteen affected individuals from 1 large family were examined clinically, which included angiography and electrophysiologic studies.

RESULTS

The PBCRA is an autosomal dominant chorioretinal dystrophy of early onset characterized by large atrophic macular and nasal retinal lesions, nystagmus, myopia, poor vision, and slow progression. A large atrophic macular lesion and nasal subretinal deposits are evident soon after birth. An atrophic area nasal to the optic nerve head appears in the second decade, which enlarges progressively. Electro-oculographic and electroretinographic studies indicated marked, diffuse abnormalities of rod and cone function. Fluorescein and indocyanine green angiography showed a large circumscribed area of macular choroidal atrophy with staining of deposits in the peripheral retina. In addition to previously documented features, nasal retinal abnormalities from a few weeks of age, marked photopsia in a number of patients, and retinal detachments in three eyes are reported as new features of the disease.

CONCLUSIONS

An extended description of PBCRA is presented highlighting that the phenotype is distinct from North Carolina macular dystrophy, although some phenotypic similarities exist between the two conditions. These disorders may be the result of different mutations on the same gene or nearby genes.

Retinal angiography in divers

OBJECTIVE

In the light of previous reports, to examine the possibility that professional diving might cause abnormalities of the retina and choroid.

METHODS

The retinal fluorescein angiograms of 55 Royal Naval divers and 24 non-diver servicemen were compared.

RESULTS

No differences were found between divers and non-divers and the prevalence of abnormalities was not correlated with diving experience.

CONCLUSION

In contrast to previous reports, there seem, at least in naval personnel, to be no ocular consequences of diving.

Retinopathy in haemoglobin C trait

Retinopathy associated with sickle-C and sickle cell disease is well described. Sickle trait and haemoglobin C trait are generally considered benign conditions, with infrequent systemic manifestations. Rare cases of retinopathy in sickle trait, in the presence of contributory factors, exist and we recently reported three such patients. The occurrence of retinopathy in haemoglobin C trait is even less well documented. Haemoglobin C does not cause red blood cell sickling but is known to decrease erythrocyte plasticity and increase blood viscosity. We report three cases in which haemoglobin C trait was associated with significant peripheral vascular occlusion and seafan formation (confirmed by fluorescein angiography) similar to that seen in sickle retinopathy. Two patients had coexistent systemic disease (hypertension and diabetes mellitus). Vitreous haemorrhage was the presenting feature in two patients. It is evident that haemoglobin C trait may be associated with sight-threatening complications.

Autosomal dominant optic atrophy with asymptomatic peripheral neuropathy

The association between hereditary motor and sensory neuropathy (HMSN) and optic atrophy has been termed HMSN type VI. The autosomal dominant inheritance of this syndrome is reported. Three generations were affected with optic atrophy, which differed in some respects from classic dominant optic atrophy, and an asymptomatic, mainly sensory, neuropathy.

Sorsby's fundus dystrophy in the British Isles: demonstration of a striking founder effect by microsatellite-generated haplotypes

Sorsby's fundus dystrophy (SFD) has been mapped to a genetic interval of 8 cM between loci D22S275 and D22S278. A total of 15 families, unrelated on the basis of genealogy and expressing the SFD phenotype were identified from a large data base of genetic eye disease families originating from diverse parts of the British Isles. The identification of the same Ser181Cys mutation cosegregating with disease in each family led us to consider the hypothesis of a founder effect being present. In all families studied, the same relatively infrequent allele (occurring in just 11% of the control group) was associated with disease at marker locus D22S280. A highly significant disease-associated haplotype, spanning across 3 cM of the SFD locus, was conserved in 11 of the 15 families (68% of all affected chromosomes); a further extended haplotype spanning up to 7 cM, was identified in 5 families (27% of SFD-associated chromosomes) and possibly represents the ancestral haplotype. This haplotype analysis has refined the TIMP3 gene localization to a 1- to 3-cM interval between marker loci D22S273 and D22S281 and provides strong evidence for a single mutational event being responsible for the majority of SFD identified in the British Isles.

Colour contrast sensitivity in patients with age-related Bruch's membrane changes

Patients with bilateral drusen as a manifestation of early age-related macular degeneration (AMD) may have minor psychophysically detectable visual defects in the presence of normal visual acuity. In a variety of retinal diseases, one of the earliest changes in visual processing is an impairment of normal colour vision. This study was undertaken to evaluate colour vision deficits in patients with macular drusen and to determine whether changes in colour contrast sensitivity may occur over time. In a prospective study, colour vision in 84 eyes of 84 patients aged 55-84 years (mean, 68.89 +/- 6.23 years) with macular drusen and clear media was tested using a computer graphics technique. A total of 47 patients were reviewed annually for up to 2 years and measurements were obtained at annual intervals. Colour contrasts sensitivity along protan, deutan and tritan colour confusion lines was determined at a foveal and a parafoveal region. The sensitivity to all stimuli showed large variations between patients. The thresholds for foveal blue-colour contrast sensitivity were elevated and increased during the review period. In contrast, there was no significant change in sensitivity with time for red and green at the foveal or parafoveal region. Tritan threshold changes suggest that the SW cone-receptor population is more susceptible to damage associated with early age-related macular disease than are red or green cones. The results indicate that blue colour contrast sensitivity determined over time may serve as a measure to assess the progression of age-related maculopathy prior to the manifestation of atrophic or exudative macular lesions associated with visual loss.

Detection of tumor-associated antigens in sera of canine cancer patients by monoclonal antibodies generated against canine mammary carcinoma cells

Two murine monoclonal antibodies (MAbs), 1A10 and SB2, generated against a canine mammary carcinoma cell line, were used in a competitive enzyme-linked immunosorbent assay (ELISA) to measure tumor-associated antigens (TAAs) in canine serum samples. Sera were tested from disease-free dogs and from dogs diagnosed with mammary carcinoma, non-mammary carcinoma, sarcoma, benign mammary tumor, benign non-mammary tumor, or non-neoplastic disease. Serum antigen concentrations measured by ELISA were expressed as inhibitory units (IU). The upper limit of normal, defined as the mean plus 2 SD of the TAA concentration in disease-free dogs, was 20 IU with antibody 1A10 and 22 IU with antibody SB2. Compared with disease-free dogs, the frequency of TAA-positive sera was significantly greater (P < 0.05) among dogs with mammary or non-mammary carcinoma when tested with MAbs 1A10 or SB2, and also with sarcoma when tested with MAb SB2. Testing a serum sample with both antibodies rather than just one increased the sensitivity of the competitive ELISA for TAA detection. The presence of TAA in serum might serve as a useful marker for certain types of carcinomas or sarcomas in canine cancer patients.

Localization of the gene for progressive bifocal chorioretinal atrophy (PBCRA) to chromosome 6q

Progressive bifocal chorioretinal atrophy (PBCRA) is a rare, autosomal dominant congenital chorioretinal dystrophy. We have performed genetic linkage analysis on a five-generation British pedigree. Two-point linkage analysis showed significant linkage with nine microsatellite marker loci mapping to chromosome 6q. Multipoint analysis gave a maximum lod score of 11.8 (theta = 0.05) between D6S249 and D6S283. This region overlaps with that to which the gene for North Carolina macular dystrophy (MCDR1) has been assigned. However, given the range of differences in phenotype between these two retinal disorders, it is likely that different mutation mechanisms are responsible for each disease.

Bimodal expressivity in dominant retinitis pigmentosa genetically linked to chromosome 19q

A clinical, psychophysical, and electrophysiologic study was undertaken of two autosomal dominant retinitis pigmentosa pedigrees with a genetic mutation assigned to chromosome 19q by linkage analysis. Members with the abnormal haplotype were either symptomatic with adolescent onset nyctalopia, restricted visual fields, and non-detectable electroretinographic responses by 30 years of age, or asymptomatic with normal fundus appearance and minimal or no psychophysical or electroretinographic abnormalities. There was no correlation in the severity in parents and their offspring. Pedigree analysis suggested that although the offspring of parents with the genetic mutation were at 50% risk of having the genetic defect, the risk of being symptomatic during a working lifetime was only 31%. Such bimodal phenotypic expressivity in these particular pedigrees may be explained by a second, allelic genetic influence and may be a phenomenon unique to this genetic locus. Genetic counselling in families expressing this phenotype can only be based on haplotype analysis since clinical investigations, even in the most elderly, would not preclude the presence of the mutant gene.

Fine matrix mapping of the macular region in normal subjects

Using a Humphrey field analyzer and fine matrix mapping, we measured photopic and scotopic thresholds for a blue light stimulus at 100 locations on a 9 degrees by 9 degrees matrix of 1 degree spacing centered at the fovea in 14 normal subjects. Additionally, trial lenses were used to investigate the effect of refractive error. Under photopic conditions the mean sensitivity varied by less than 1 dB over this region. Under scotopic conditions the central values were reduced in sensitivity by 15 dB compared with those at 4 degrees eccentricity. Defocus showed less than 1.2 dB loss with 1.00D of refractive error under photopic condition. The results reflect the properties of rod and cone photoreceptors and the effects of the rod mosaic near the fovea. This technique is a sensitive test of macular visual function.

Retinal photoreceptor dystrophies LI. Edward Jackson Memorial Lecture

PURPOSE

To assess the state of knowledge of photoreceptor dystrophies.

METHODS

The current literature concerning photoreceptor dystrophies is reviewed, and their potential impact on concepts of pathogenesis of disease and clinical practice is assessed.

RESULTS

As a result of cooperative investigative work between researchers in various disciplines, major advances in the classification of retinal photoreceptor dystrophies have been made. Until recently, classification of retinal dystrophies was based on clinical observation alone, and it was evident that this method was imprecise and of limited value. Largely through the work of molecular biologists, it has been shown that diseases clinically indistinguishable from one another may be a result of mutations on a variety of genes; conversely, different mutations on a single gene may give rise to a variety of phenotypes. It is reassuring that it is possible to generate concepts as to potential pathogenetic mechanisms that exist in retinal dystrophies in light of this new knowledge. More important for the clinician is the potential impact on clinical practice. There is as yet no therapy by which the course of most of these disorders can be modified. However, there is a considerable body of work in which therapeutic intervention is being explored, and many researchers now see treatment as a justifiable objective of their work.

CONCLUSIONS

Knowledge of the causative mutation is of value to the clinician in that it provides a precise diagnosis and allows the distribution of the abnormal gene to be documented fully within a family. To take full advantage of the opportunities provided by current research, clinical practice will have to be modified, particularly if therapy can be justified.

Modulation by canine interferon-gamma of major histocompatibility complex and tumor-associated antigen expression in canine mammary tumor and melanoma cell lines

In an effort to enhance the antigenicity of canine tumor cells, canine interferon-gamma (CnIFN-gamma) was applied in vitro to seven canine mammary tumor (CMT) and two canine melanoma (CML) cell lines. Surface expression of major histocompatibility complex (MHC) antigens and tumor-associated antigens (TAA) was measured by a flow cytometric fluorescence assay using commercially available anti-MHC antibodies, and anti-canine TAA monoclonal antibodies generated against CMT and CML cell lines. Compared to constitutive antigen levels in untreated cells, treatment with CnIFN-gamma resulted in increased expression of MHC class I and II antigens (up to 19- and 167-fold, respectively) and a TAA (up to 5-fold) by CMT cell lines, and increased expression of class I antigen (131-fold) by one CML and of class II antigen (18-fold) by the other CML cell line. Expression of MHC antigens and a TAA by tumor cells was increased by Cn-IFN-gamma treatment, and such an increase may be of potential benefit in tumor cell recognition and rejection by the immune system.

Recurrent acute multifocal placoid pigment epitheliopathy in two cousins

PURPOSE/METHODS

To test the hypothesis that there may be inherited predisposition in acute multifocal placoid pigment epitheliopathy, HLA typing was undertaken in two cousins with recurrent disease.

RESULTS/CONCLUSIONS

Both cousins were shown to have HLA antigens DR2 but not B7; both antigens have been associated with this disorder previously. This finding is compatible with the concept that DR2 may be associated with an increased risk of recurrent disease.

Ocular findings in Saudi Arabian patients with sickle cell disease

AIM

This study was set up to determine whether or not retinal changes occur in sickle cell disease in Saudi Arabian subjects with either the Benin, which exists in the south western part of the kingdom, or Asian haplotypes in the east, and to compare the findings with those in sickle cell disease in Jamaica.

METHODS

Retinal examination and fluorescein angiography were performed in 61 patients with SS disease (40 eastern, 20 south western, 1 central region) and 10 with sickle cell beta(0) thalassaemia.

RESULTS

Peripheral retinal vascular changes were common, and a qualitatively abnormal vascular border believed to imply risk of proliferative sickle retinography (PSR) was significantly more common in south western SS patients and PSR was shown in one of these. There were no differences in visual acuity, the presence of peripheral retinal patches, or the circumferential or posterior extent of peripheral retinal vessel closure between SS disease and sickle cell beta(0) thalassaemia or between SS disease in the two regions. Compared with the Jamaican Cohort Study, > 180 degrees of the peripheral retinal vasculature was seen significantly less frequent, suggesting factors inhibiting vascular remodeling in Saudi patients in early life.

CONCLUSION

Sickle cell disease in Saudi Arabia affects the retina and represents a potential threat to vision. Changes occur whatever the haplotype, and is similar to that observed in Jamaica.

Distribution of fundus autofluorescence with a scanning laser ophthalmoscope

BACKGROUND

Variation of fluorescence derived from lipofuscin in the retinal pigment epithelium has been recorded with age and in retinal diseases. Studies have been based largely on in vitro observations on eye bank eyes which has placed severe limitations on the data available.

METHODS

A technique is described whereby in vivo imaging of autofluorescence of the fundus was achieved using a scanning laser ophthalmoscope.

RESULTS

The optical characteristics, distribution, and variation with disease imply that the fluorescence is derived from lipofuscin in the pigment epithelium. Autofluorescence is shown to be abnormally high in certain inherited diseases, and low in the presence of retinal atrophy.

CONCLUSION

This technique may be useful both in clinical practice and research. It may allow the detection of the abnormal phenotype in genetically determined disease at a time when other techniques may not. Longitudinal studies of age related macular disease would permit correlation between changes in the pigment epithelium and Bruch's membrane to be established.

Autosomal dominant pattern dystrophy of the retina associated with a 4-base pair insertion at codon 140 in the peripherin/RDS gene

OBJECTIVE

To define the phenotype of a retinal dystrophy associated with a 4-base pair insertion at codon 140 of the peripherin/RDS gene.

PATIENTS

Six affected members spanning two generations of a single family were examined. Five were studied in detail electrophysiologically and psychophysically.

METHODS

Psychophysical testing included color vision testing, photopic and scotopic static threshold perimetry, and dark adaptometry. Electrophysiological testing included flash and pattern electroretinography, as well as electrooculography.

RESULTS

Clinical findings ranged from subtle pigmentary changes at the level of the retinal pigment epithelium to more widespread pigmentary changes associated with choroidal neovascularization. Those with severe fundus changes exhibited greater abnormalities in psychophysical and electrophysiological testing than those with minimal fundus changes.

CONCLUSIONS

This particular peripherin/RDS gene mutation is associated with dominantly inherited pattern dystrophy of the retina. The phenotypic expression is variable in a manner not explained by age.