Long term clinical outcome of a randomised controlled trial of anterior chamber lenses after high volume intracapsular cataract surgery

BACKGROUND

Age related cataract remains the major cause of blindness throughout the world. In many countries, the majority of cataract surgery continues to be done by the intracapsular cataract extraction (ICCE) method. The results of a large randomised controlled trial of multiflex open loop anterior chamber intraocular lenses (ACIOL) were reported from a busy eye hospital in Nepal.

METHODS

There was a randomised controlled trial of 2000 people with bilateral cataract reducing vision to less than 6/36. Interventions were ICCE with an ACIOL compared with ICCE with aphakic spectacles (+11 dioptres). Participants were followed at discharge, 6 weeks, 1 year, and 1 1/2-5 years after surgery. Visual acuity and clinical outcome were measured. A poor outcome was defined as vision <6/60.

RESULTS

Visual outcome was comparable in the two groups. More of the control group experienced functional blindness due to loss of aphakic spectacles at 1 year. The majority of cases of poor outcome occurred in the first year after surgery. There was no indication of any lens related problems after 1 year.

CONCLUSION

Multiflex open loop anterior chamber lenses are safe for up to 1 year of follow up when used by experienced surgeons, and the available evidence of 2-5 years of follow up suggests that the complication rate is reasonably low. An ACIOL at the time of cataract surgery offers benefits over routine ICCE surgery with aphakic spectacle correction as it avoids the problem of replacing lost and broken spectacles.

Bilateral external iliac and common femoral artery disruptions after blunt trauma

Blunt trauma to the external iliac or common femoral artery is relatively rare. Since its original description as the "motor-scooter handlebar syndrome," this type of injury has been hypothesized as resulting from compression of the artery by the inguinal ligament. We report a case of mirror-image arterial injuries from blunt trauma. At operation, each distal external iliac and proximal common femoral artery was found to have large intimal flaps. Resection of the injured segments with bilateral saphenous vein interposition grafts led to a successful outcome.

Leaf respiration of snow gum in the light and dark. Interactions between temperature and irradiance

We investigated the effect of temperature and irradiance on leaf respiration (R, non-photorespiratory mitochondrial CO(2) release) of snow gum (Eucalyptus pauciflora Sieb. ex Spreng). Seedlings were hydroponically grown under constant 20 degrees C, controlled-environment conditions. Measurements of R (using the Laisk method) and photosynthesis (at 37 Pa CO(2)) were made at several irradiances (0-2,000 micromol photons m(-2) s(-1)) and temperatures (6 degrees C-30 degrees C). At 15 degrees C to 30 degrees C, substantial inhibition of R occurred at 12 micromol photons m(-2) s(-1), with maximum inhibition occurring at 100 to 200 micromol photons m(-2) s(-1). Higher irradiance had little additional effect on R at these moderate temperatures. The irradiance necessary to maximally inhibit R at 6 degrees C to 10 degrees C was lower than that at 15 degrees C to 30 degrees C. Moreover, although R was inhibited by low irradiance at 6 degrees C to 10 degrees C, it recovered with progressive increases in irradiance. The temperature sensitivity of R was greater in darkness than under bright light. At 30 degrees C and high irradiance, light-inhibited rates of R represented 2% of gross CO(2) uptake (v(c)), whereas photorespiratory CO(2) release was approximately 20% of v(c). If light had not inhibited leaf respiration at 30 degrees C and high irradiance, R would have represented 11% of v(c). Variations in light inhibition of R can therefore have a substantial impact on the proportion of photosynthesis that is respired. We conclude that the rate of R in the light is highly variable, being dependent on irradiance and temperature.

Ginkgo biloba extract for age-related macular degeneration

BACKGROUND

Ginkgo is used in the treatment of peripheral vascular disease and 'cerebral insufficiency'. It is thought to have several potential mechanisms of action including increased blood flow, platelet activating factor antagonism and prevention of membrane damage caused by free radicals. Vascular factors and oxidative damage are thought to be two potential mechanisms in the pathology of age-related macular degeneration.

OBJECTIVES

The objective of this review is to determine the effect of Ginkgo biloba extract on the progression of age-related macular degeneration.

SEARCH STRATEGY

The Cochrane Eyes and Vision Group specialised register, the Cochrane Controlled Trials Register - Central, MEDLINE, reference lists of identified trial reports, and the Science Citation Index were searched. The reviewer contacted Investigators of included studies for additional information. The most recent searches were performed in February 2000.

SELECTION CRITERIA

All randomised trials where Ginkgo biloba extract had been compared to control in people with age-related macular degeneration were included.

DATA COLLECTION AND ANALYSIS

The reviewer extracted data using a standardised form. The data were verified with the trial investigator.

MAIN RESULTS

One published trial was identified. Although a beneficial effect was observed, as only 20 people were enrolled in the trial, and assessment of outcome was not masked, its results must be considered equivocal. Adverse effects and quality of life for people with age-related macular degeneration have not been addressed. One unpublished trial is awaiting translation and assessment.

REVIEWER'S CONCLUSIONS

The question as to whether people with age-related macular degeneration should take Ginkgo biloba extract to prevent progression of the disease has not been answered by research to date.

Randomized controlled trial of anterior-chamber intraocular lenses in Nepal: long-term follow-up

Most of the estimated 20 million people who are blind with cataracts live in rural areas of developing countries, where expert surgical resources are scarce. We have studied the use of multiflex open-loop anterior-chamber intraocular lenses (ACIOL) in high-volume low-cost surgery. Between 1992 and 1995, a total of 2000 people attending Lahan Eye Hospital, Nepal, with bilateral cataracts reducing vision to < or = 6/36 were randomly allocated to receive intracapsular extraction (ICCE) with aphakic spectacles, or ICCE with an ACIOL. We re-examined the cohort (1305/2000, 65%) between November 1996 and April 1997 and report the findings in this article. There were 13 new cases of poor visual outcome (best corrected vision < 6/60) arising after one year: 9 in the ACIOL group and 4 in the control group; odds ratio 2.1 (95% confidence interval, 0.59-9.55). The causes of poor outcome were as follows: ACIOL group--retinal detachment (4 cases), cystoid macular oedema (2), epiretinal membrane (1), age-related macular degeneration (1), and late endophthalmitis (1); control group--retinal detachment (2 cases), late endophthalmitis (1), and primary open-angle glaucoma with age-related macular degeneration (1). In rural areas of developing countries, well-manufactured multiflex open-loop ACIOLs can be implanted safely by experienced ophthalmologists after routine ICCE, avoiding the disadvantages of aphakic spectacle correction.

Antioxidant vitamin and mineral supplementation for preventing age-related macular degeneration

BACKGROUND

Some observational studies have suggested that people who eat a diet rich in antioxidant vitamins (carotenoids, vitamins C and E) or minerals (selenium and zinc) may be less likely to develop age-related macular degeneration.

OBJECTIVES

The aim of this review is to examine the evidence as to whether or not taking vitamin or mineral supplements prevents the development of age-related macular degeneration.

SEARCH STRATEGY

We searched the Cochrane Eyes and Vision Group specialised register, the Cochrane Controlled Trials Register - Central, MEDLINE, reference lists of identified reports and the Science Citation Index. We contacted investigators and experts in the field for details of unpublished studies. The most recent searches were conducted in June 1999.

SELECTION CRITERIA

All randomised trials comparing an antioxidant vitamin and/or mineral supplement (alone or in combination) to control were included. We included only studies where supplementation had been given for at least one year.

DATA COLLECTION AND ANALYSIS

Both reviewers independently extracted data and assessed trial quality. Currently there is only one published trial included in the review so no data synthesis was conducted.

MAIN RESULTS

One trial is included in the review. This was a primary prevention trial in Finnish male smokers with four treatment groups: alpha-tocopherol alone, beta-carotene alone, alpha-tocopherol and beta-carotene, placebo. The add-on maculopathy study was conducted in a subset of the main trial cohort. 269 cases of maculopathy (14 late stage age-related macular degeneration) were identified. There was no association of age-related macular degeneration with treatment.

REVIEWER'S CONCLUSIONS

There is no evidence to date that people without age-related macular degeneration should take antioxidant vitamin and mineral supplements to prevent or delay the onset of the disease. The results of five large ongoing trials are awaited.

Is anterior chamber lens implantation after intracapsular cataract extraction safe in rural black patients in Africa? A pilot study in KwaZulu-Natal, South Africa

PURPOSE

There are an estimated 16 million people blind from cataract world-wide. In many areas the routine operation is intracapsular cataract extraction (ICCE). The role of modern anterior chamber (AC) intraocular lenses (IOLs) is being explored, and they have been shown to be safe and successful in Asia. Are they equally safe in rural black African populations?

METHODS

One hundred black patients aged 50 years and over who attended Edendale Hospital were enrolled in a pilot study of insertion of AC IOLs after ICCE. They were followed up for 6 months.

RESULTS

With financial remuneration, the follow-up rate at 8 weeks increased from the usual 30% to 72%. At 6 months, 67% of eyes achieved a correlated visual acuity of 6/18 or better. Thirty per cent had persistent uveitis, 16% had peripheral anterior synechiae beyond the points of haptic contact, and 5% had an intraocular pressure greater than 21 mmHg.

CONCLUSIONS

A randomised trial comparing ICCE with AC IOL and extracapsular cataract extraction with posterior chamber IOL is probably not justified at this time in this population. However, there may be wide variations in the reaction of the eyes of different African ethnic groups to IOLs. In view of the successful use of AC IOLs in Asian eyes, further pilot studies of AC IOLs may be warranted in other parts of Africa where ICCE is the routine procedure.

Does raised intraocular pressure begin in utero?

AIM

To determine whether fetal and infant growth, as assessed by weight at birth and weight at 1 year, are related to intraocular pressure.

METHODS

717 men and women born in Hertfordshire between 1920 and 1930, for whom records of birth weight and weight at 1 year were available, were examined. Visual fields were assessed using the Takagi central 25 degrees 75 point static threshold screening program. Tonometry was performed using the Perkin's tonometer. The disc was assessed by direct ophthalmoscopy through dilated pupils.

RESULTS

A significant inverse relation was found between systolic blood pressure and birth weight. However, no association was found between birth weight or weight at 1 year and intraocular pressure, cup/disc ratio, or visual field defects.

CONCLUSIONS

There was no evidence to support fetal or infant growth as being important factors for the subsequent development of raised intraocular pressure.

Are rates of ageing determined in utero?

BACKGROUND

epidemiological studies have shown that poor early growth is associated with cardiovascular and other degenerative diseases. This has been explained by programming, whereby undernutrition and other influences which restrict early growth permanently change the structure and physiology of the body. The long-term effects of poor early nutrition on ageing have been demonstrated in animals but not studied in man.

OBJECTIVES

to determine if poor early growth was associated with increased markers of ageing in later life.

METHODS

we traced 1428 men and women, born in Hertfordshire between 1920 and 1930, for whom records of early weight were available. 824 (58%) were interviewed at home and 717 (50%) attended clinic for eye examination, audiometry, grip strength measurement, skin thickness ultrasound and anthropometry.

RESULTS

lower weight at 1 year was associated with increased lens opacity score, higher hearing threshold, reduced grip strength and thinner skin. Visual acuity, macular degeneration and intraocular pressure were not related to early growth.

CONCLUSIONS

the associations between early growth and markers of ageing suggest that in some systems, ageing may be programmed by events in early life. A potential mechanism is the impaired development of repair systems.

Age-related nuclear lens opacities are associated with reduced growth before 1 year of age

PURPOSE

The aim of this study was to assess the relationship between fetal and infant growth, as measured by birthweight and weight at 1 year and the development of age-related lens opacities.

METHODS

A total of 1428 men and women who were born in Hertfordshire, United Kingdom, between 1920 and 1930, and for whom records of birthweight and weight at 1 year were available, were traced and invited for examination. Of these, 717 (50%) attended for ophthalmic examination. After dilation with tropicamide 1%, lens opacities were graded using the Lens Opacities Classification System (LOCS) III.

RESULTS

In this population of English men and women aged 64 to 74 years, most opacities were of the nuclear type. There was no association between birthweight and nuclear lens opacities. Weight at 1 year was negatively correlated with nuclear opacity score in adult life (P=0.001). Subjects in the highest tertile for weight at 1 year (>23 pounds) had an odds ratio of 0.35 (95% confidence interval, 0.17 to 0.74) for having a significant nuclear lens opacity (LOCS score of > or = 3) compared with people in the lowest tertile for weight at 1 year (<21 pounds). This association remained after controlling for age, sex, smoking, social class, adult height, and diabetes.

CONCLUSIONS

To our knowledge, this is the first time that such an association has been reported; it needs to be replicated in other populations. It could provide part of the explanation for the observed excess risk of cataract in developing countries.

Systemic risk factors for idiopathic macular holes: a case-control study

PURPOSE/BACKGROUND

The idiopathic full-thickness macular hole (IFTMH) is an important cause of poor vision in the elderly affecting predominantly women over the age of 60 years. While it is accepted that vitreoretinal traction is an important local factor in the development of IFTMH, the underlying cause is not known. The aim of this study was to identify possible systemic risk factors for the development of IFTMH.

METHODS

Two hundred and thirty-seven patients with IFTMH (cases) attending the Macular Hole Clinic at Moorfields Eye Hospital were identified. These were compared with 172 patients without macular holes (controls) attending other clinics in the same hospital. Cases and controls were frequency-matched by sex. The prevalence of the following factors in both groups was ascertained by interview: ethnic origin, place of birth, housing tenure, any systemic diseases, current and lifetime consumption of medication, severe dehydrational episodes, menstrual and obstetric history, onset and severity of menopause and use of exogenous oestrogens (in women only), osteoporosis, vegetarianism, use of vitamin supplementation, and smoking and alcohol consumption. Height and weight were measured for all participants.

RESULTS

Cases of IFTMH macular holes were predominantly women (67%) and aged 65 years and older (74%). We found very few systemic risk factors that were significantly associated with IFTMH. There was a higher prevalence of diabetes in controls (12% vs 5%). There was no association between the majority of indicators of oestrogen exposure in women and macular holes, but cases had a more difficult menopause as judged by the severity of hot flushes at menopause: odds ratio 2.6 (1.4-4.6).

CONCLUSIONS

In common with other studies, we found only a few systemic factors associated with IFTMH. The study did confirm, however, that IFTMH is a strongly gender-related disease. There is some evidence for the role of sudden changes in hormonal balance, as seen by the increased reporting of severity of symptoms around the menopause along with (statistically non-significant) increased risks associated with hysterectomy and oophorectomy. The particular aetiological factor which puts women at increased risk of macular holes requires further studies.

[Value of anterior chamber lenses in developing countries. Results of a clinical study]

There are estimated to be 20 million people blinded by cataracts, 80-90% of whom live in rural areas of developing countries where expert surgical resources are scarce. The majority of all cataract operations are still intracapsular extractions (ICCE). Aphakic correction using spectacles is problematical in developing countries. This study was undertaken to evaluate the safety of multiflex open loop anterior chamber intraocular lenses (AC IOLs).

METHODS

A total of 2000 people attending Lahan Eye Hospital, South-east Nepal, with bilateral cataract were randomly allocated to receive in their first eye either ICCE with AC IOL (AC IOL group) or ICCE with aphakic correction (control group). All operations were performed by two ophthalmologists using a standardized technology and 4.5 x operating loupe magnification. Functional and best corrected vision was recorded. The primary outcome measure was poor vision after surgery, which was defined as a visual acuity of less than 6/60 at 1 year follow-up (WHO definition for severe visual impairment and blindness).

FINDINGS

The median time needed to perform ICCE was 4.1 min and to perform ICCE with AC IOL 6 min. Of all study patients 91% were examined after 1 year. Five percent of the AC IOL group and 5.4% of the control group had a functional visual acuity of less than 6/60. Causes of reduced vision in the AC IOL group versus the control group were: correctable refractive error (22 vs 29), uveitis/secondary glaucoma (13 vs 2), endophthalmitis (4 vs 7), pre-existing eye diseases (4 vs 5), retinal detachment (0 vs 4), and corneal decompensation (0 vs 1). Of the control group, 24 patients were found to be functionally blind in the operated eye (vision < 3/60) because they did not wear their aphakic spectacles. Normal vision (WHO definition: > or = 6/18) was achieved best corrected in 89.9% of the AC IOL group and 93.2% of the control group. Analysis of additional long-term follow-ups (2-5 years post-operatively) has not yet been completed.

INTERPRETATION

This study provides evidence that in developing countries well-manufactured multiflex open loop AC IOLs can be implanted safely by experienced ophthalmologists after routine ICCE, avoiding the disadvantages of aphakic spectacle correction.

Randomised controlled trial of anterior-chamber intraocular lenses

BACKGROUND

There are an estimated 16 million people blind in both eyes with cataracts. Most live in rural areas of developing countries where surgical resources are scarce. There is no consensus on the most appropriate type of intraocular lens in situations where high-volume low-cost surgery is required. This study was undertaken to evaluate the safety of multiflex open-loop anterior-chamber lenses (ACIOLs).

METHODS

2000 people attending Lahan Eye Hospital, southern Nepal, with bilateral cataracts reducing vision to 6/36 or less were randomly allocated to receive standard surgery--intracapsular extraction (ICCE) with aphakic correction--or ICCE with an ACIOL in their first operated eye. The primary outcome was a visual acuity of less than 6/60 in the operated eye at 1 year follow-up. Visual acuity was measured for 91% of the cohort at 1 year. The sample size was estimated to detect a doubling in poor visual outcome from an estimated rate of 4% in the standard surgery (control) group.

FINDINGS

The median (range) time taken to do the surgery was 6.0 (3.0-17.2) min for the ACIOL group and 4.1 (2.4-10.3) min for the control group. 1 year after surgery, 5.0% of the ACIOL group and 5.4% of controls had functional vision less than 6/60 (OR 0.93 [0.60-1.43], p = 0.71). The causes of poor vision in the ACIOL and control groups were: correctable refractive error (22 and 29), uveitis/secondary glaucoma (13 and two), endophthalmitis (four and seven), pre-existing eye disease (four and five), retinal detachment (none and four), cystoid macular oedema (two and none), corneal ulcer (one and one), and corneal decompensation (none and one).

INTERPRETATION

This study provides evidence that, in rural areas of developing countries, multiflex open-loop ACIOLs can be implanted safely by experienced ophthalmologists after routine ICCE, avoiding the disadvantages of aphakic spectacle correction. Further follow-up is planned.

The relationship between CO2-assimilation rate, Rubisco carbamylation and Rubisco activase content in activase-deficient transgenic tobacco suggests a simple model of activase action

Transgenic tobacco (Nicotiana tabacum L. cv. W38) plants with an antisense gene directed against the mRNA of ribulose-1,5-bisphosphate carboxylase/ oxygenase (Rubisco) activase were used to examine the relationship between CO₂-assimilation rate, Rubisco carbamylation and activase content. Plants used were those members of the r₁ progeny of a primary transformant with two independent T-DNA inserts that could be grown without CO₂ supplementation. These plants had from < 1% to 20% of the activase content of control plants. Severe suppression of activase to amounts below 5% of those present in the controls was required before reductions in CO₂-assimilation rate and Rubisco carbamylation were observed, indicating that one activase tetramer is able to service as many as 200 Rubisco hexadecamers and maintain wild-type carbamylation levels in vivo. The reduction in CO₂-assimilation rate was correlated with the reduction in Rubisco carbamylation. The anti-activase plants had similar ribulose-1,5-bisphosphate pool sizes but reduced 3-phosphoglycerate pool sizes compared to those of control plants. Stomatal conductance was not affected by reduced activase content or CO₂-assimilation rate. A mathematical model of activase action is used to explain the observed hyperbolic dependence of Rubisco carbamylation on activase content.

Specific reduction of chloroplast glyceraldehyde-3-phosphate dehydrogenase activity by antisense RNA reduces CO2 assimilation via a reduction in ribulose bisphosphate regeneration in transgenic tobacco plants

The reduction of 3-phosphoglycerate (PGA) to triose phosphate is a key step in photosynthesis linking the photochemical events of the thylakoid membranes with the carbon metabolism of the photosynthetic carbon-reduction (PCR) cycle in the stroma. Glyceraldehyde-3-phosphate dehydrogenase: NADP oxidoreductase (GAPDH) is one of the two chloroplast enzymes which catalyse this reversible conversion. We report on the engineering of an antisense RNA construct directed against the tobacco (Nicotiana tabacum L.) chloroplast-located GAPDH (A subunit). The construct was integrated into the tobacco genome by Agrobacterium-mediated transformation of leaf discs. Of the resulting transformants, five plants were recovered with reduced GAPDH activities ranging from 11 to 24% of wild-type (WT) activities. Segregation analysis of the kanamycin-resistance character in self-pollinated T1 seed from each of the five transformants revealed that one plant (GAP-R) had two active DNA inserts and the others had one insert. T1 progeny from GAP-R was used to generate plants with GAPDH activities ranging from WT levels to around 7% of WT levels. These were used to study the effect of variable GAPDH activities on metabolite pools for ribulose-1,5-bisphosphate (RuBP) and PGA, and the accompanying effects on the rate of CO2 assimilation and other gas-exchange parameters. The RuBP pool size was linearly related to GAPDH activity once GAPDH activity dropped below the range for WT plants, but the rate of CO2 assimilation was not affected until RuBP levels dropped to 30-40% of WT levels. That is, the CO2 assimilation rate fell when RuBP per ribulose-1,5-biphosphate carboxylase-oxygenase (Rubisco) site fell below 2 mol.(mol site)-1 while the ratio for WT plants was 4-5 mol.m(mol site)-1. Leaf conductance was not reduced in leaves with reduced GAPDH activities, resulting in an increase in the ratio of intercellular to ambient CO2 partial pressure. Conductance in plants with reduced GAPDH activities was still sensitive to CO2 and showed a normal decline with increases in CO2 partial pressure. Although PGA levels did not fluctuate greatly, the effect of reduced GAPDH activity on RuBP-pool size and assimilation rate can be interpreted as being due to a blockage in the regeneration of RuBP. Concomitant gas-exchange and chlorophyll alpha fluorescence measurements indicated that photosynthesis changed from being Rubisco-limited to being RuBP-regeneration-limited at a lower CO2 partial pressure in the antisense plants than in WT plants.(ABSTRACT TRUNCATED AT 400 WORDS)

Third place winner of the Conrad Jobst Award in the gold medal paper competition. Prevention of spinal cord dysfunction in a new model of spinal cord ischemia

Paraplegia or paraparesis caused by temporary cross-clamping of the aorta is a devastating sequela in patients after surgery of the thoracoabdominal aorta. No effective clinical method is available to protect the spinal cord from ischemic reperfusion injury. A small animal (rat) model of spinal cord ischemia is established to better understand the pathophysiological events and to evaluate potential treatments. Eighty-one male Sprague-Dawley rats weighing 300 g to 350 g were used for model development (45) and treatment evaluation (36). The heparinized and anesthetized rat was supported by a respirator following tracheostomy. The thoracic aorta was cannulated via the left carotid artery for post-clamping intra-aortic treatment solution administration. After thoracotomy, the aorta was freed and temporarily clamped just distal to the left subclavian artery and just proximal to the diaphragm for different time intervals: 0, 5, 10, 15, 20, 25, 30, 35, and 40 minutes (five animals per group). The motor function of the lower extremities postoperatively showed consistent impairment after 30 minutes clamping (5/5 rats were paralyzed), and this time interval was used for treatment evaluation. For each treatment, six animals per group were used, and direct local intra-aortic infusion of physiologic solution (2 mL) at different temperatures with or without buffer substances was given immediately after double cross-clamp to protect the ischemic spinal cord. Arterial blood (2 mL) was infused in the control group. The data indicate that the addition of HCO3-(20 mM) to the hypothermic (15 degrees C) solution offered complete protection of the spinal cord from ischemic injury.(ABSTRACT TRUNCATED AT 250 WORDS)

The African Caribbean Eye Survey: risk factors for glaucoma in a sample of African Caribbean people living in London

The purpose of the study was to estimate the prevalence of and risk factors for chronic glaucoma in a sample of African Caribbean people over 35 years of age living in the London Borough of Haringey. A cross-sectional voluntary sample of persons were subjected to detailed ophthalmic assessment including automated tangent screen suprathreshold visual field testing, applanation tonometry and stereoscopic disc evaluation in 50 community-based survey clinics over an 8 month period. Cases and suspects were referred to Moorfields Eye Hospital for more detailed assessment and confirmation of the diagnosis. Of 873 eligible persons examined (out of a total of 1022), 32 definite cases of glaucoma were identified, a prevalence of 3.9%; 42% of these had been previously diagnosed. Approximately 10% of the sample required further assessment and follow-up when ocular hypertensives and glaucoma suspects were included. An age-standardised comparison with the findings of the Roscommon survey revealed a relative risk for glaucoma for Haringey blacks compared with Irish whites of 3.7. Significant risk factors for glaucoma included age, African birthplace and darker skin colour. Neither diabetes nor hypertension reached significance. Despite the lack of a population base, this study provides strong evidence that the 4 times greater risk of glaucoma estimated for American blacks compared with whites applies equally to the United Kingdom population. Community-based facilities are required to raise awareness of the risk among this ethnic minority in this country and case-finding resources should be provided to meet local needs.

Reduction of ribulose biphosphate carboxylase activase levels in tobacco (Nicotiana tabacum) by antisense RNA reduces ribulose biphosphate carboxylase carbamylation and impairs photosynthesis

The in vivo activity of ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) is modulated in response to light intensity by carbamylation of the active site and by the binding of sugar phosphate inhibitors such as 2'-carboxyarabinitol-1-phosphate (CA 1P). These changes are influenced by the regulatory protein Rubisco activase, which facilitates the release of sugar phosphates from Rubisco's catalytic site. Activase levels in Nicotiana tabacum were reduced by transformation with an antisense gene directed against the mRNA for Rubisco activase. Activase-deficient plants were photosynthetically impaired, and their Rubisco carbamylation levels declined upon illumination. Such plants needed high CO2 concentrations to sustain reasonable growth rates, but the level of carbamylation was not increased by high CO2. The antisense plants had, on average, approximately twice as much Rubisco as the control plants. The maximum catalytic turnover rate (k cat) of Rubisco decreases in darkened tobacco leaves because of the binding of CA 1P. The dark-to-light increase in k cat that accompanies CA 1P release occurred to similar extents in antisense and control plants, indicating that normal levels of activase were not essential for CA 1P release from Rubisco in the antisense plants. However, CA 1P was released in the antisense plants at less than one-quarter of the rate that it was released in the control plants, indicating a role for activase in accelerating the release of CA 1P.