Detection of subpigment epithelial neovascularisation in cases of retinal pigment epithelial detachments: a review of the Moorfields treatment trial

The entry angiograms of 42 eyes with detachment of the retinal pigment epithelium in a treatment trial of laser photocoagulation were reviewed in a masked fashion by three observers in order to assess the possible presence of subpigment epithelial neovascularisation. Vascularity or avascularity was designated with reference to a list of clues believed to imply the presence of subpigment epithelial neovascularisation. As a predictor of outcome the initial assessment achieved a sensitivity and specificity of 77% and 82% respectively. Despite notable parity of the degree of sensitivity and specificity among the three observers, full agreement on the initial assessments was reached in only 23 eyes (55%), 10 with vascular and 13 with avascular outcome. Of these, only one eye which developed new vessels after 4 years had an outcome which differed from that predicted by classification of the entry angiograms.

Controlled trial of laser photocoagulation of pigment epithelial detachments in the elderly: 4 year review

Patients who were enrolled in a controlled treatment trial of laser grid photocoagulation for retinal pigment epithelial detachment as part of age-related maculopathy were reviewed 4 years after entry into the trial. The data imply that the original conclusion that this form of treatment did not improve the visual prognosis at 18 months was also justified at 4 years. It has become clear that lesions with evidence of subpigment epithelial new vessels were included in the trial. In a retrospective study the lesions were separated into those in which there was evidence of subretinal neovascularisation and those in which no such evidence existed. A difference was identified in the behaviour of the treated and untreated lesions designated avascular in that the treated eyes had a poorer visual outcome. These cases accounted for the different behaviour between two management groups in the initial study such that the original conclusion that grid photocoagulation of avascular pigment epithelial detachments in the elderly does not improve the visual prognosis is justified.

Development and function of the early B cell repertoire

The early B cell repertoire is characterized by extensive interconnectivity, autoreactivity and multispecificity. Our preliminary sequence analysis of some of the idiotype specific antibodies is beginning to provide molecular clues to explain the observed multireactivity and the expression of shared idiotypic determinants on immunoglobulins of early B cells. The VH gene rearrangements analyzed are typical of the early pre-B cell and CD5 B cell repertoire. Some of these include shared or identical CDR3 regions resulting from the use of germline VH, D and JH gene segments in the absence of N region addition. As previously described, the most D proximal VH genes are also used most frequently. Collectively these genetic restrictions, together with the lack of somatic mutation, suggest that the characteristic self reactivity of the early B cell repertoire is related to the expression of germline gene segments and limited use of diversification mechanisms. It has also been possible for the first time to isolate hybridomas secreting functional IgM molecules which use the most D proximal VH gene, VH81X. These antibodies and another example from the VH7183 family have a broad multireactivity pattern possibly because of the presence of an unusually high number of charged amino acid groups present in the VH region. These findings are preliminary and more extensive studies are needed to establish if these groups are responsible for the highly cross-reactive nature of these antibodies. Nevertheless, these unusual characteristics signify a unique role for antibodies expressing this VH gene during B cell development. It is also clear that the observed anti-lymphocyte reactivity, another feature of the newborn repertoire, is the result of the prevalence of B cells using similar if not identical VHDJH genes and DJH joins. The development of these B cells appears to occur consistently in early ontogeny and, again, are not found in conventional splenic B cells obtained from the normal adult. Understanding the functional significance of the early appearance of these antibodies may help to clarify and understand their role during development as well as in autoimmunity. We propose that the unique self reactive nature of the early repertoire provides a pattern within which self-assertiveness develops and results in the establishment of the adult repertoire. In doing so, dominant clones are established which may or may not be within, but whose selection and differentiation is directed by the CD5 B cell subset.(ABSTRACT TRUNCATED AT 400 WORDS)

Acute tear of the retinal pigment epithelium

The fluorescein angiographic findings immediately following a tear of the retinal pigment epithelium are presented and the mechanisms of fluid movement from the retina to the choroid are discussed. Our case represents a clinical correlate to recent experimental reports on fluid movement across the retinal pigment epithelium-Bruch's membrane complex.

Effect of a long-acting somatostatin analogue (BIM23014) on proliferative diabetic retinopathy: a pilot study

A pilot study on the use of a continuous infusion of somatostatin, by subcutaneous pumps in the management of proliferative diabetic retinopathy is reported. Two patients out of eight with proliferative retinopathy demonstrated improvement. One patient demonstrated regression of disc new vessels and the other a reduced area of retinal capillary non-perfusion, both demonstrated by fluorescein angiography. Control patients showed worsening of fluorescein leakage over the observation period of four to six weeks whereas the other six patients given the somatostatin infusion did not demonstrate any deterioration. The mechanism of action of somatostatin in this study is unknown but it is thought to have direct anti-angiogenic properties as well as inhibiting growth hormone secretion.

Iris clipping of a diode laser beam when performing retinal photocoagulation

The Microlase infrared diode laser has recently become available for retinal photocoagulation. It uses a laser beam with a large convergence angle (23 degrees). This gives rise to a laser beam with a relatively large cross section at the subject's pupil. In this study the pupillary area required to view the fundus at the slit-lamp with a 90-dioptre lens is determined. It is found that the pupillary area required to view the fundus is smaller than the cross section of the Microlase laser beam at the pupil. Thus iris clipping of the laser beam can occur even though the surgeon has a clear and bright view of the fundus. Care should be taken to use the Microlase only in the presence of a widely dilated pupil.

Effects of dibutyryl cyclic AMP, ouabain, and xanthine derivatives on crossbridge kinetics in rat cardiac muscle

In a previous communication, we showed that beta-adrenergic stimulation of cardiac muscles was associated with an increase in the rate of cycling of crossbridges as measured by perturbation analysis in the frequency domain. In this analysis, the frequency at which dynamic stiffness is a minimum (fmin) is taken as a measure of the rate of crossbridge cycling. In this paper, we test the hypothesis that the beta-adrenergic receptor-induced increase in crossbridge cycling rate is mediated by elevation of the intracellular level of cyclic AMP. The approach taken is to compare the effects on fmin in rat papillary muscles during Ba(2+)-activated contractures of 1) an agonist of cyclic AMP that can easily penetrate the cell, namely, dibutyryl cyclic AMP, 2) agents that block cyclic AMP phosphodiesterase, namely, the xanthine derivatives isobutylmethylxanthine and caffeine, and 3) an inotropic agent that does not affect the intracellular level of cyclic AMP, namely, ouabain. Our results showed that dibutyryl cyclic AMP at a dose of 5 mM has the same actions as beta-adrenergic stimulation: it potentiated the isometric twitch force, reduced the time to peak tension and time to half relaxation, and shifted fmin by a factor of 1.8 +/- 0.1 (n = 5). Isobutylmethylxanthine at up to 1.1 mM also acted in the same manner, increasing fmin by a factor of 1.8 +/- 0.2 (n = 6), but ouabain, at a dose (0.03 mM) sufficient to potentiate twitch force by 40 +/- 2% (n = 4), was without effect on the time course of the twitch nor was fmin changed (n = 4). Our findings support the hypothesis that a beta-adrenergic receptor-mediated increase in crossbridge cycling rate is due to an increase in intracellular cyclic AMP level and illustrate the usefulness of the frequency domain analysis approach in the analysis of the mechanism of action of inotropic agents.

Q-switched neodymium YAG laser vitreolysis in the therapy of posterior segment disease

We describe our experience of ten cases of posterior segment vitreolysis, using the short-pulse neodymium YAG (Yttrium Aluminium Garnate) laser. Eight patients had proliferative diabetic retinopathy, one patient had had an intraocular foreign body removed and one patient had had uveitis. Of the ten, five patients had macular traction retinal detachments, three patients had progressive traction retinal detachments threatening the macula and two patients had recurrent vitreous haemorrhages from mechanical traction on areas of fibrovascular proliferation. Eight of the patients were successfully treated. One macular retinal detachment failed to flatten and a tear was found which may have been iatrogenic. In one patient with a traction retinal detachment significant traction was relieved but the detachment failed to flatten completely. We discuss the indications, techniques, difficulties and complications. Our experience suggests that this technique has an important role in the treatment of selected patients, sparing patients conventional vitrectomy, or making possible the treatment of those for whom vitrectomy has been contraindicated or refused. Anterior defocusing of the YAG would be a useful modification of current laser systems and improved aiming systems desirable for the future.

Initial clinical experience using a diode laser in the treatment of retinal vascular disease

A pilot study has been carried out to investigate the clinical use of an infrared diode laser in the treatment of a number of retinal vascular conditions. A hand-held device was employed initially and subsequently a further prototype was developed for use in conjunction with a standard slit lamp microscope. Thirty-three eyes in thirty patients were treated for conditions such as proliferative diabetic retinopathy, exudative retinopathy and branch and central retinal vein thrombosis. Regression of neovascularisation was observed in 13 of 16 eyes (81%) with proliferative diabetic retinopathy and in six of eight eyes (75%) with branch retinal vein occlusion. Four eyes were successfully treated for established or incipient rubeosis iridis following central vein thrombosis. Focal photocoagulation applied to five eyes for diabetic exudative maculopathy resulted in partial resorption of the exudates. These results are presented together with information on the ease of use of the laser and its reliability. The implications of the development of this instrument in the context of its place in ophthalmic therapy are discussed.

Extensive argon laser photocoagulation in the treatment of proliferative diabetic retinopathy

A group of 20 patients (28 eyes) with proliferative retinopathy who required extensive argon laser photocoagulation to induce regression of new vessels is presented. The mean number of burns applied to each eye was 7225, with a maximum of 11,513. These were delivered in a mean of nine sessions over a mean period of 22.9 months. Twenty-five eyes (89%) had a final visual acuity of 6/18 or better. The remaining three eyes (11%) had severely reduced vision attributable to complications of proliferative diabetic retinopathy (traction retinal detachment involving the macula in two eyes and ischaemic maculopathy and a persistent vitreous haemorrhage in the third). Large amounts of confluent argon laser photocoagulation may be necessary for the elimination of new vessels in some patients, and it is our view that laser photocoagulation should be continued until regression of new vessels occurs. This is compatible with the retention of functional vision and good visual acuity.

Optic disc neovascularization in dominant exudative vitreoretinopathy

Dominant exudative vitreoretinopathy (DEVR) is inherited retinal vascular disorder which is characterized by peripheral retinal neovascularization, tractional retinal detachment, subretinal, exudation, and vitreous fibrosis. A milder form of involvement characterized by capillary nonperfusion and straightening of the retinal vessels may be present in asymptomatic individuals. We describe a 15-year-old patient who presented with optic disc neovascularization, a finding not previously reported in association with DEVR. Angiographic evidence of DEVR in successive generations confirmed the diagnosis. The findings in mild and advanced DEVR are reviewed, and the pathogenesis of the capillary nonperfusion is discussed.

Adrenaline increases the rate of cycling of crossbridges in rat cardiac muscle as measured by pseudo-random binary noise-modulated perturbation analysis

The mechanism of action of adrenaline on cardiac contractility in rat papillary muscles containing V1 and V3 isomyosins was analyzed during barium-activated contractures at 25 degrees C by frequency domain analysis using pseudo-random binary noise-modulated perturbations. The analysis characterizes a frequency (fmin) at which dynamic stiffness of a muscle is a minimum, a parameter that reflects the rate of cycling of crossbridges. We have previously shown that fmin for V1- and V3-containing papillary muscles were 2.1 +/- 0.2 Hz (mean +/- SD) (n = 10) and 1.1 +/- 0.2 Hz (n = 8), respectively, and that these values were independent of the level of activation. The present study's goal was to determine whether the inotropic action of adrenaline was associated with an increased rate of crossbridge cycling. The results show that a saturating dose of adrenaline increased fmin in V1 hearts by 49 +/- 2% (n = 11). The action on V3 hearts was significantly less; the increase in fmin was 26 +/- 2% (n = 6). The increase in fmin for V1 hearts was shown to be sensitive to the beta-blocking agent propranolol. These results suggest that adrenaline significantly increases the rate of crossbridge cycling by a beta-receptor-mediated mechanism. We conclude that the increased contractility of the heart in the presence of adrenaline arises not only from more complete activation of the contractile proteins but also from the increased rate at which each crossbridge can transduce energy.

[Expression and mutagenesis of genes coding for protein synthesis in the influenza virus]

Double-stranded cDNA copies of the neuraminidase genes of influenza viruses A/Tokyo/3/67 (N2), A/tern/Australia/G70C/75 (N9), and B/Lee/40, and the hemagglutinin genes of A/Memphis/1/71 (H3) and B/Hong Kong/8/73 were cloned into a SV40 vector in which the late region was replaced by the influenza sequences. Thus the influenza genes were expressed in transfected cells under the control of the SV40 late promoter. The Tokyo/67 neuraminidase gene was modified by oligonucleotide-directed site-specific in vitro mutagenesis. Several of the amino acid residues which are conserved in all known neuraminidases and which line the sialic acid binding pocket were changed, and the mutant gene ligated back into the SV40 vector. Five mutations which have been fully characterized resulted in synthesis of a protein which had totally lost neuraminidase enzyme activity.

Pattern electroretinograms become abnormal when background diabetic retinopathy deteriorates to a preproliferative stage: possible use as a screening test

The pattern electroretinogram (PERG) and other tests were given to a selected group of patients with diabetes, ranging from those who had no retinopathy or funduscopic changes to those in the preproliferative state. None had visual symptoms. The PERG was found to be normal in patients with microaneurysms and a few blot haemorrhages. However, when cotton-wool spots and angiographic evidence of areas of capillary non-perfusion were present, the PERG was reduced below the normal value. Similar changes occurred with the oscillatory potentials of the ERG evoked by an intense flash, but the results were more variable. So in the individual patient the test is not a reliable indicator of the progress of the retinopathy. The value of the PERG in screening is discussed.

Penetration of topical cyclosporine into the rabbit cornea, aqueous humor, and serum

Systemic and ocular absorption of topically applied 10% cyclosporine ointment was determined in rabbit cornea, aqueous humor, and serum by radioimmunoassay. The concentration of the drug in the cornea reached a peak of 900 ng/mL three hours after application. Substantial levels were still present at 24 hours. Relatively low concentrations were measured in the aqueous humor and serum, suggesting corneal stromal pooling of this hydrophobic cyclic peptide. Topical ocular application of cyclosporine may reduce or eliminate the drug's systemic toxic effects while maintaining a therapeutic level of local immunosuppressive activity.

Retinal vein occlusion and the prevalence of lipoprotein abnormalities

Ninety-nine patients with retinal vein occlusion (40 with central, 59 with branch vein occlusion) were investigated for the prevalence of associated diseases for comparison with an age-matched control group. There was a significantly increased prevalence of hyperlipidaemia (p less than 0.001) and hypercholesterolaemia (p less than 0.001) in the group with branch retinal vein occlusion and of hyperlipidaemia (p less than 0.001) and hypercholesterolaemia (p less than 0.02) in the group with central retinal vein occlusion compared with controls. An increased prevalence of hypertriglyceridaemia (p less than 0.001) was also found in patients with central vein occlusion. Other associations were noted (hypertension and oestrogen therapy). Increased serum cholesterol concentrations were found in patients with central vein occlusion (p less than 0.05) and branch vein occlusion (p less than 0.001) compared with controls, and similar tendencies were noted for levels of LDL and HDL cholesterol. Patients with central vein occlusion also had raised levels of serum triglyceride (p less than 0.001) and VLDL-triglyceride (p less than 0.05). The occurrence of both central and branch vein occlusions may be associated with an increased prevalence of hyperlipidaemia and hypertension. Increase of serum lipids may contribute to the aetiology of vein occlusion by altering plasma viscosity or affecting platelet function.

A device for automated laser delivery in retinal photocoagulation

We report a modification to the argon-krypton laser (Lasertek Model AK 41) which allows optional automatic operation. This is a safe, time-saving device for use in cases requiring extensive retinal laser treatment.

Angioid streaks in Jamaican patients with homozygous sickle cell disease

Angioid streaks were observed in 21 of 242 patients with homozygous sickle cell disease. Two morphological types were observed. There is no evidence that angioid streaks in Jamaican patients are related to pseudoxanthoma elasticum.

Photocoagulation for optic disc new vessels in diabetes mellitus

The effects of treatment by argon laser and xenon arc photocoagulation in 165 diabetic patients with optic disc new vessel formation have been studied retrospectively. Visual acuity and degree of new vessel formation have been assessed over a period of between six months and seven years of follow-up (mean 23 months). Visual acuity improved in 36% of treated eyes and remained unchanged in 34%. Improvement was most marked in those with initially poor acuity (less than 6/36). There was no association between improvement in visual acuity and regression of disc vessels, the latter occurring in 79% of treated eyes. Only 6% of eyes became blind during the period of follow-up, principally as a result of vitreous haemorrhage and retinal detachment. There was no difference between the results produced by the use of separate or combined argon laser and xenon arc photocoagulation on the regression of disc new vessels. However, our results suggest that argon laser treatment was more effective than xenon arc photocoagulation in improving visual acuity. These findings suggest that either form of treatment or a combination offers considerable benefit in the management of proliferative diabetic retinopathy, even when very severe at presentation.

Autosomal dominant exudative vitreoretinopathy

Twelve affected members from 3 families with autosomal dominant exudative vitreouretinopathy were examined, and the following conclusions were drawn: (1) There is great variability in the phenotypic expression of the abnormal gene, such that many patients have very mild disease which can be detected with certainty only by fluorescein angiography. (2) Gene penetrance is close to 100%. (3) Progress of fundus changes and visual threat is rare after 20 years of age.

Excessive permeability in diabetic maculopathy

Four cases of diabetic maculopathy with excessive permeability are described. Fluorescence angiography is distinctive, showing profuse early leakage from the entire capillary bed of the posterior pole. Careful studies have failed to reveal any cause for this excessive permeability response at the macula or any constantly associated medical abnormality. The prognosis for visual acuity is poor, and photocoagulation has only rarely been successful in maintaining or improving vision in these patients.