An economic comparison of hospital-based and community-based glaucoma clinics

INTRODUCTION

We have established one model for community care of glaucoma clinic patients. Community optometrists received training and accreditation in glaucoma care. Once qualified they alternated between running half day glaucoma clinics in their own High Street practices and assisting in a hospital-based glaucoma clinic session. This paper reports the cost of this model.

METHODS

Micro-costing was undertaken for the hospital clinic. A consensus meeting was held to agree costs for community clinics involving all optometrists in the project along with representatives of the multiple chain optometry practices who had participated. Costs to patients both indirect and direct were calculated following structured interviews of 197 patients attending hospital clinics and 194 attending community clinics.

RESULTS

The estimated cost per patient attendance to the hospital clinic was £63.91 and the estimated cost per attendance to the community clinic was £145.62. For patients the combined direct and indirect cost to attend the hospital clinic was £6.15 and the cost to attend the community clinic £5.91.

DISCUSSION

The principal reason for the higher cost in the community clinic was higher overhead costs in the community. Re-referral to the hospital system only occurred for 9% of patients and was not a large contribution to the increased cost. Time requested to next appointment was similar for the two clinics. Sensitivity analysis shows a strong effect of increasing patients seen per clinic. It would, however, require 25 patients to be seen per clinician per day in the community in order to make the costs comparable.

The future of glaucoma clinics

The number of patients seen with glaucoma related pathologies is predicted to increase significantly over the next few years as a result of an ageing population, increased optometric screening, and raised public awareness. In addition, the recent glaucoma literature proposes more aggressive management of ocular hypertension, open angle glaucoma, and narrow angle pathologies. This will overburden many glaucoma services and demands a reappraisal of current management strategies. Using a database of patients compiled from their tertiary referral glaucoma service as an example, the authors discuss the current controversies relating to each glaucoma subtype, encompassing issues relating to disease prognosis, efficacy of treatment, and resource management. They also suggest a range of strategies aimed at streamlining glaucoma clinics. Examples include shared care schemes, multidisciplinary teams, clinic guidelines/protocols, and alteration of clinic review times. The predicted effect of such schemes on clinic workloads is discussed, together with any existing validation.

A pilot study of a system for grading of drainage blebs after glaucoma surgery

PURPOSE

To develop and evaluate a novel bleb grading scheme for clinical and photographic evaluation.

METHOD

A system for grading bleb photographs using widely applicable parameters was designed, and reference color photographs printed. A prospective masked agreement study was undertaken comparing slit lamp examination with mono and stereo photographs; 36 eyes of 28 patients with previous glaucoma surgery were graded according to defined parameters on a 1 to 10 scale clinically at the slit lamp by four ophthalmologists and two optometrists. Standardized stereo and mono photographs of the blebs were taken on the same day. The photographs were graded at least one week later in a masked fashion by the same observers, with grading of mono and stereo photographs also separated by one week. Analysis was performed to determine the variability and agreement between slit lamp results and photographic results, and to identify the presence of systematic bias.

RESULTS

High levels of agreement were found between slit lamp and both stereo and mono photographs for vascularity indices, bleb wall thickness, and bleb elevation. Lower levels of agreement were found for the relative components of demarcated versus diffuse areas of the bleb, and for the total width of the bleb. The interquartile range for the median difference between slit lamp and photograph grading was -1.0 to 1.0 for all criteria except diffuse component (-2.0 to 2.0), and the median difference for all scores was 0.0. The median interobserver difference for all criteria was 0.0; the quartile range for all scores was between -0.5 and 1.0 except for diffuse component and width assessments whose quartiles fell in the -1.75 to 1.0 range. Examiners agreed with photographic grading within +/- 1 in more than 80% of gradings for vascularity and bleb height, within +/- 1 in more than 75% of gradings for bleb wall thickness, within +/- 2 in 61% of bleb width assessments, and +/- 2 in 59% of diffuse component.

CONCLUSION

This bleb grading system is reproducible clinically and photographically. High levels of agreement between scores for photographs versus slit lamp examination were found for most categories, with good interobserver agreement for both photograph and slit lamp grading. Further refinement of scoring and reference photographs is required for optimization, especially for grading of bleb morphology.

The cost-effectiveness of technology transfer using telemedicine

The high burden of disease in developing countries often makes it difficult for health systems in these countries to attain the same level of specialist skills as industrialized countries. Technology transfer is one way to improve specialist skills whilst at the same time reducing the burden of disease. This paper describes the use of teleophthalmology, a form of telemedicine, as a mode of technology transfer between the United Kingdom and South Africa. As the burden of eye disease in South Africa is high, the country cannot afford the level of ophthalmic specialization achieved in the UK. The paper estimates the cost-effectiveness of the technology transfer project in terms of a cost per Disability Adjusted Life Year (DALY) averted. We found the technology transfer project to be cost-effective in reducing the burden of eye disease, and that practitioners in South Africa also learned novel procedures that could help future patients and improve cost-effectiveness. Technology transfer using telemedicine is a cost-effective method that richer countries can employ to aid capacity building in the health care systems of poorer countries.

Glaucoma case finding: a cluster-randomised intervention trial

PURPOSE

To assess the effect of an intervention comprising training in optic disc assessment, explicit referral criteria and ophthalmologist feedback on referred patients, on the number of optometrist referrals for suspected glaucoma seen at a referral site and the positive predictive value of those referrals.

METHODS

Optometric practices routinely referring to the Ealing Hospital Eye Clinic were randomly divided into two groups taking into consideration those practices, which shared an optometrist (a cluster) and the number of optometrist days worked per week. One group of practices acted as controls, while the other practices were invited to receive the intervention. Data on 397 new patients referred and presenting to Ealing Hospital with suspected glaucoma were collected over a 20-month period. The data on patients who had failed to attend their appointment were collected over 7 months of this period. The number of referrals seen, the positive predictive value of those referrals, and the attendance rate were calculated. Optometrist's opinions of the intervention were assessed qualitatively. Data relating to optometrist compliance with the intervention were also collected.

RESULTS

The number of glaucoma referrals presenting to Ealing Hospital from the intervention practices was almost double that from the control practices (210 vs 119). When cluster randomisation, the number of optometrist days per cluster and the number of assessed referrals in the preintervention period are taken into consideration, it is estimated that the intervention is associated with a 52% increase in the number of referrals reaching Ealing Hospital. However, the design effect resulting from the cluster randomisation was unexpectedly high (of the order of 13-14)and so the confidence intervals around the estimate of 52% are very wide (95% c.i. 35% decrease to 253% increase, P = 0.34). There was no evidence of an association between optometrist compliance with the intervention and the number of referrals seen at Ealing Hospital. The positive predictive value (PPV)of referrals was similar for the intervention(0.49 (95% c.i. 0.42, 0.55)) and control groups(0.46 (95% c.i. 0.33, 0.60)). Optometrist opinions of the intervention were largely favourable. All expressed a willingness to participate in future programmes.

CONCLUSION

A large difference in the number of referrals between the practice groups was observed. Since the PPV of referral was unchanged, the potential impact of the intervention in terms of numbers of new cases of glaucoma detected in the community is substantial. However, because of its large design effect, this trial does not provide conclusive evidence of an impact of the intervention on referral numbers. A considerably larger trial will be required to produce conclusive evidence of an effect.

Severe and unrecognised: pertussis in UK infants

AIMS

To diagnose pertussis using culture, polymerase chain reaction, and serology, in children admitted to intensive care units (PICUs) and some paediatric wards in London, and in their household contacts to determine the source of infection.

METHODS

Infants <5 months old admitted to London PICUs between 1998 and 2000 with respiratory failure, apnoea and/or bradycardia, or acute life threatening episodes (ALTE), and children <15 years admitted to paediatric wards at St Mary's and St George's Hospitals between 1999 and 2000 with lower respiratory tract infection, apnoea, or ALTE were studied.

RESULTS

Sixty seven per cent of eligible children (142/212) were recruited; 23% (33/142) had pertussis, 19.8% (25/126) on the PICU and 50% (8/16) on wards. Two died. Only 4% (6/142) were culture positive. Pertussis was clinically suspected on admission in 28% of infants (7/25) on the PICU and 75% (6/8) on the wards. Infants on PICU with pertussis coughed for longer, had apnoeas and whooped more often, and a higher lymphocyte count than infants without pertussis. Pertussis and respiratory syncytial virus (RSV) co-infection was frequent (11/33, 33%). Pertussis was confirmed in 22/33 (67%) of those who were first to become ill in the family. For 14/33 children the source of infection was a parent; for 9/33 the source of pertussis was an older fully vaccinated child in the household.

CONCLUSIONS

Severe pertussis is under diagnosed. An RSV diagnosis does not exclude pertussis. Future changes to the UK vaccination programme should aim to reduce pertussis transmission to young infants by their parents and older siblings.

Sensitivity and specificity of two glaucoma case-finding strategies for optometrists

Current best practice for primary open-angle glaucoma case-finding comprises history-taking, disc examination, intraocular pressure measurement and suprathreshold visual field analysis (SVFA). An alternative case-finding technique was formulated replacing SVFA with computerised quantitative disc assessment, using the Heidelberg retinal tomograph II (HRT II). Each approach was adopted by four optometrists who screened 29 POAG and 37 normal patients. Average sensitivities and specificities were similar in the two groups [sensitivity 71% (SVFA) vs 69% (HRT II); specificity 94% both groups]. Our inclusion of pre-perimetric glaucoma cases limited the sensitivity of the optometrists in this study. There was evidence to suggest that the optometrists tended to miss early changes at the optic disc such as disc haemorrhage, nerve fibre layer defects and subtle neuroretinal thinning.

Changes in intraocular pressure following diagnostic mydriasis with cyclopentolate 1%

PURPOSE

To assess the effect of diagnostic mydriasis with 1% cyclopentolate on the intraocular pressure (IOP) of patients attending glaucoma, medical retina and cataract clinics.

METHODS

Levels of agreement for IOP assessment were determined and 95% of repeated readings found to be within +/-2 mmHg. The IOP of 83 cataract, 87 medical retinal and 100 glaucoma patients was measured with Goldmann applanation tonometry before and 45 min after dilatation with 1% cyclopentolate. Those showing a substantial (>10 mmHg) increase in IOP underwent gonioscopy to determine if their angles remained open and were medically treated to lower their IOP.

RESULTS

An approximately normal distribution of change in IOP following dilatation was seen in all three groups (mean change 0.4 mmHg (95% CI 0.1-0.8)). The proportion of patients with a rise of 5 mmHg or more in the right eye was 7% (95% CI 4-10%). Logistic regression using all right eyes, looking at age, sex, diagnosis, ethnicity, ocular medication, iris colour and lens status (phakic/pseudophakic/aphakic) as risk factors for a rise of IOP of 5 mmHg or more did not reveal any significant contribution. Correlation between results obtained for right and left eyes in the glaucoma group was lower (0.43) than for the other groups (0.66 and 0.72), but the extent to which the direction of change in one eye predicted that in the other was shown to be high. Two glaucoma patients with open angles developed a clinically important (>10 mmHg) sustained rise in IOP requiring treatment.

CONCLUSIONS

Individual variability in the effects of cyclopentolate on aqueous dynamics may account for the approximately normal distribution of IOP seen following dilatation in all three groups. This variation was in excess of that due to observation error alone. It is recommended that the IOP be rechecked after dilation in glaucoma patients with significantly damaged optic nerve heads. In medical retina and cataract patients, sustained clinically important rises in intraocular pressure following dilation seem rarer.

Utilization and practical aspects of tele-ophthalmology between South Africa and the UK

A tele-ophthalmology service was established between a regional hospital in South Africa and a specialist eye hospital in the UK. The aim of the service was to provide secondary specialist advice in the diagnosis and treatment of difficult ophthalmology cases in South Africa. Over 12 months, the South African medical officers saw 16,458 ophthalmology patients and would have liked a second opinion in 5.7% of these cases. Case discussions conducted by videoconferencing at 384 kbit/s were carried out in 0.5% of cases. No significant connection problems were experienced during the 12-month study period. On 4% of occasions, the case discussions were conducted at a bandwidth of 256 kbit/s, but this did not affect the quality of the still images. The South African medical officers valued the educational benefits gained from the case discussions with the UK specialists.

Subspecialty adnexal ophthalmological examination using telemedicine

We studied the clinical outcome of examination of a group of patients with adnexal (eyelid and orbit) conditions. Seventeen patients with adnexal problems were assessed by an ophthalmologist at a distance using telemedicine, and then subsequently by an ophthalmologist in a face-to-face consultation. Measurements such as palpebral aperture, levator muscle function and eyelid skin crease position were recorded. The clinical outcomes from both consultations were recorded independently by the consultants and then compared. The study showed that certain adnexal conditions, such as congenital and involutional ptosis, could be accurately assessed using telemedicine, but that other conditions, such as socket problems in patients who had a previous enucleation or those with non-specific ocular pain with less clear-cut features, were better assessed in a face-to-face consultation. Overall, teleconsultations appeared to be suitable for the assessment of uncomplicated ptosis but not for less well defined conditions. Other factors, such as family dynamics and language problems, also limited the usefulness of the technique.

What optic disc parameters are most accurately assessed using the direct ophthalmoscope?

PURPOSE

It has been suggested that over-reliance on the cup-to-disc ratio is a major factor in the misinterpretation of the optic disc. In spite of this optometrist assessment of the optic disc tends to be restricted to measurement of the cup-to-disc ratio and cup depth only. Would interpretation of the disc improve if optometrists were to evaluate other parameters? The aim of this study was to evaluate the accuracy of optometrist assessment of nine parameters of the optic nerve head using direct ophthalmoscopy.

METHODS

Eight optometrists evaluated nine parameters of the optic nerve head (vertical disc diameter, vertical cup-to-disc ratio, neuroretinal rim configuration, cup shape, neuroretinal rim colour, vessel path, presence/ absence of haemorrhage, extent and location of peripapillary atrophy and classification of health status of the disc) in 50 eyes of 50 patients using direct ophthalmoscopy. Intensive training in optic nerve head assessment was given prior to assessing the patients. Criteria for evaluation were discussed. The 'gold standard' reference was the classification of the parameters by a consultant ophthalmologist with a special interest in glaucoma.

RESULTS

Interobserver agreement for vertical cup-to-disc ratio was almost perfect (mean weighted kappa 0.84). Agreement for neuroretinal rim configuration, cup shape, haemorrhage and final classification of the disc was good (mean kappa 0.62-0.67). There was moderate agreement for vessel configuration (mean kappa 0.53). For assessment of peripapillary atrophy, disc size and neuroretinal rim colour, agreement was fair (mean kappa 0.22-0.34).

CONCLUSIONS

Accuracy of assessment was greatest for vertical cup-to-disc ratio, neuroretinal rim configuration and cup shape. Improved agreement has been demonstrated for the final classification of the disc compared with previous reports. The combination of training and assessment of additional disc parameters appears to improve interpretation of the optic nerve head by optometrists.

Telemedicine techniques can be used to facilitate the conduct of multicentre trials

A multicentre randomized controlled trial was established in Pretoria, Bloemfontein and Edendale in South Africa, and coordinated from London. The purpose of the trial was to determine the efficacy of low-dose beta irradiation of glaucoma. Five communication modalities (telephone, fax, e-mail, videoconferencing and face-to-face meetings) were examined in terms of their benefits in a multicentre trial. The eight stages of the multicentre trial examined were: set-up and training, recruitment, standardization, patient management, data transmission, update and data dissemination, clinical follow-up and monitoring, and publication. On four-point Likert scales for rating the usefulness of the communication modalities at each of the eight stages of the trial (from 0 = not useful to 3 = very useful; maximum score 24) the telephone was given a total score of 10, fax 9, e-mail 13, videoconferencing 15 and face-to-face meetings 9. Telemedicine techniques offer considerable benefits in the coordination of multicentre trials by improving data collection, maintaining the efficacy and monitoring of trials, while potentially offering reduced costs in terms of travel and time. The realtime scrutiny of patient records helps to ensure data uniformity and completeness of data collection. Videoconferencing was most useful when considered as one of several communication tools that can be used to improve the effectiveness of a service or process.

Postoperative evaluation of patients following ophthalmic surgery

We have used telemedicine to support the postoperative evaluation of patients who have had ophthalmic surgery. Mobile telemedicine workstations connected using three ISDN lines have enabled us to review patients at an outreach clinic on the first postoperative day. Video slit-lamp images of the patient are captured by a trained ophthalmic nurse at the outreach clinic and viewed by surgeons at Moorfields Eye Hospital in central London during live teleconsultations. During the study period, over 80 teleconsultations were carried out on postoperative cataract, trabeculectomy and combined procedures. Preliminary results are very encouraging. Although 8 (33%) of 24 patients were anxious about being involved in the teleconsultation, 20 (83%) had confidence in the system and only one (4%) found the experience unacceptable.

Comparison of costing tools in paediatric intensive care

The cost of service provision is an issue of concern to all professionals working in health care. Department of Health reports have highlighted the need for more effective costing mechanisms for provision of paediatric intensive care (PIC). This study aimed to determine whether nurse-patient dependency scoring would be as effective as the Therapeutic Intervention Scoring System (TISS) at providing a differential costing tool for PIC. Data were collected on 251 patient admissions over 1,741 nursing shifts and analysis of variance undertaken. Findings suggest that a modified nurse-patient dependency score would be as good as TISS as a potential costing tool in PICU.

Positive predictive value of optometrist-initiated referrals for glaucoma

A study was conducted at the Moorfields Community Eye Clinic at Ealing Hospital to determine the positive predictive value (ppv) of optometric referrals for suspected glaucoma. The information reported in the referrals and the reasons given for referral were also assessed and evaluated in relation to the ppv. Information was gathered through prospective analysis of patient clinic notes. Ninety patients were referred over a six-month period of which 87 fulfilled the inclusion criteria. The optometrist referral letters for 79 of these patients were supplied by the GP. Results indicate a ppv of 0.43. The reason for referral in the majority of cases (48%) was raised IOP alone. However the most frequently reported mode of practice was a combination of disc and IOP assessment (57%). In line with other research our study demonstrates that referral accuracy improves as the number of suspicious findings increases. In addition those referrals reporting all three tests (IOP measurement, optic disc assessment and perimetry) are shown to have the highest ppv.

Cortical cholinergic dysfunction after human head injury

Loss of cholinergic neurotransmission is implicated in memory impairment and cognitive dysfunction after head injury. The aim of the present study was to investigate presynaptic markers, particularly in relation to cholinergic neurotransmission in human postmortem brain from patients who died following a head injury and age-matched controls. Choline acetyltransferase activity and high-affinity nicotinic receptor binding sites were assayed in the inferior temporal gyrus, cingulate gyrus, and superior parietal cortex of 16 head-injured patients and 8 controls. Synaptophysin immunoreactivity was determined in the left cingulate gyrus from the same patient groups. In the head-injured group, choline acetyltransferase activity was consistently reduced in each cortical region compared to control subjects. The presence of a subdural haematoma and a prolonged survival period after head injury tended to be associated with lower choline acetyltransferase activity. In contrast to the marked reduction in choline acetyltransferase activity, nicotine receptor binding was unchanged in head-injured compared to control patients. Synaptophysin immunoreactivity in the cingulate gyrus was reduced by approximately 30% (p < 0.05) in the head-injured group compared to controls. Correlation of choline acetyltransferase activity with synaptophysin immunoreactivity indicated there is a deficit of cholinergic presynaptic terminals in postmortem human brain following head injury.

Risk factors for optic nerve disease in communities mesoendemic for savannah onchocerciasis, Kaduna State, Nigeria

Ophthalmic examinations on 6831 individuals aged 5 years or more, living in 34 guinea savannah communities mesoendemic for onchocerciasis, in Kaduna State, Nigeria, revealed a relatively high prevalence (9%) of optic nerve disease (OND). Further investigations were performed to determine what proportion of this burden of OND might be due to onchocercal infection. Information on history of cerebro-spinal meningitis (CSM), past use of diethylcarbamazine (DEC) and chloroquine, consumption of cassava and locally produced alcohol was collected for all individuals by questioning. In addition, a nested case-control study of 81 cases of OND and 136 age and sex-matched controls was performed to investigate whether syphilis or a variety of other neurological disorders were responsible for a substantial proportion of cases of OND. Our data suggest that in this population, onchocercal infection is the single most important cause of OND and may account for 50% of all cases. Some 13% of cases were associated with signs suggestive of glaucoma. DEC use might be responsible for up to 30% of all OND. We found no evidence to suggest that any of the following are important causes of OND in the communities studied: CSM, syphilis, neurological syndromes such as polyneuropathy or other generalized neurological disease, consumption of raw cassava, consumption of locally prepared alcohol.

Impact of annual dosing with ivermectin on progression of onchocercal visual field loss

Reported are the results of a randomized, double-masked, placebo-controlled trial of annual ivermectin dosing in 34 rural communities, Kaduna State, northern Nigeria, where guinea savanna onchocerciasis is mesoendemic. A total of 939 individuals underwent Friedmann field analysis at the first examination and saw at least 19 spots in at least one eye. Of these, 636 (68%) completed a subsequent Friedmann field analysis 2-3 years later. The adjusted incidence rate ratio for the ivermectin group versus the placebo group was 0.64 (95% confidence interval (CI): 0.42-0.98). There was some evidence that the impact of ivermectin was greatest among those who had received one dose of ivermectin. The majority of the deteriorations occurred in eyes that gave evidence of optic atrophy at the first examination. An analysis restricted to individuals with optic atrophy at baseline indicated a reduction of 45% in the incidence of visual field deterioration in the ivermectin group (95% CI: 8-67%). Previous findings have shown that ivermectin has an impact on the incidence of optic atrophy. Our results indicate, for the first time, that ivermectin has a substantial impact on the progression of visual field loss among those with pre-existing optic atrophy.

Red-dot card test of the paracentral field as a screening test for optic nerve disease in onchocerciasis

A new screening test for optic nerve pathology is described, consisting of a series of four red targets presented at an angle of 12 degrees in the paracentral field above and below the horizontal meridian. Nonperception and desaturation of the targets are recorded. Inter-observer variability studies found a kappa value = 0.8. A total of 6831 individuals aged > or = 5 years in communities that were mesoendemic for savanna onchocerciasis in Kaduna State, northern Nigeria, were screened using the test. Of the participants 22% were unable to complete the test; almost two-thirds of these (62%) were aged 5-8 years. After exclusion of those visually impaired or blind according to WHO criteria and those unable to complete the test, the test showed a sensitivity of 40% and a specificity of 98% for optic nerve disease when inability to visualize one or more targets was used as the definition of test failure. The sensitivity increased to 54% with a specificity of 96% when the criterion for failure included desaturation of one or more targets. These values compare favourably with those for other available screening methods. The test took 1-2 minutes to perform and was readily accepted by patients and nurses.

Ivermectin and onchocercal optic neuritis: short-term effects

In 1982 the macrocyclic lactone, ivermectin, was first tested in human patients with onchocerciasis. It has since undergone phase I to IV trials and is now being widely distributed in onchocercal areas. The previous microfilaricide, diethylcarbamazine citrate (DEC), is known to precipitate or exacerbate active optic neuritis in some onchocercal patients, as part of a wider inflammatory response (the Mazzotti reaction). Ivermectin may also cause a mild reaction, especially in people with high microfilarial loads. Few data are available concerning the effect of ivermectin on active optic neuritis. A large, randomised, double-masked, phase IV trial is reported. Individuals were screened for evidence of optic nerve disease (OND), and those identified as possible cases of OND underwent detailed ophthalmic examination, including fluorescein angiography, before being dosed with ivermectin or placebo. A total of 6831 persons were screened of whom 856 (13%) underwent angiography prior to dosing. At 7-14 days after dosing an attempt was made to re-examine 50% of adults over the age of 20 years, including all those with OND. Six hundred and eighty-eight repeat or new angiograms were performed. During this period, 5 new cases of active optic neuritis and one case of exacerbation of existing optic neuritis were identified. Five of these individuals had received placebo and one ivermectin. Two individuals with optic neuritis before dosing had improved after 7-14 days. One had received placebo, the other ivermectin. Ivermectin does not appear to precipitate or exacerbate optic neuritis at a period of 7-14 days.

Distribution and aetiology of blindness and visual impairment in mesoendemic onchocercal communities, Kaduna State, Nigeria. Kaduna Collaboration for Research on Onchocerciasis

During a field trial of ivermectin in Kaduna State, 6831 people age 5 years and above, living in 34 mesoendemic onchocercal communities in Kaduna State, northern Nigeria, were examined for ocular disease. Visual function assessments included tests of visual acuity and visual fields. A total of 185 individuals (2.7%) were bilaterally blind by acuity criteria with a further 28 blind by field constriction. The overall prevalence of blindness was 3.1%. A further 118 individuals were visually impaired by WHO criteria. Examination for the cause of blindness revealed that 43% of eyes in bilaterally blind patients were blind due to onchocerciasis. A further 11% were blind from optic atrophy much of which was probably onchocercal in origin. Glaucoma was the next most common cause of blindness in the bilaterally blind (11%). Only 6% of eyes were blind from cataract as the primary cause. In the visually impaired population cataract was the most common primary cause of impaired/blind eyes (31%), followed by onchocerciasis (19%) [corrected].

Reduction in incidence of optic nerve disease with annual ivermectin to control onchocerciasis

The safety and efficacy of ivermectin in the prevention of blindness from onchocerciasis have been established in many studies that have addressed the drug's effects on the front of the eye. We undertook a study with sufficient statistical power to detect an effect on optic nerve disease (OND), probably the main cause of blindness in the disorder. The trial was based in 34 mesoendemic communities in Kaduna State, Nigeria. Villagers aged 5 years and older were randomly assigned annual dosing with ivermectin or placebo for 3 years. Participants underwent medical and ophthalmological examinations before the first, third, and fourth treatments. 3522 villagers aged 15 and older were re-examined at least once. Skin-snip samples were taken at baseline for calculation of microfilarial load. The outcome measure was development of disc pallor accompanied by objective evidence of deterioration in visual function; 116 subjects (45 ivermectin-treated, 71 placebo-treated) showed such changes during the trial. The incidence rate ratio (ivermectin vs placebo) was 0.90 (95% CI 0.54-1.51) for subjects with loads of 0-10 mf (microfilariae) per mg skin and 0.52 (0.29-0.93) for subjects with more than 10 mf/mg. The incidence rate ratio varied little when account was taken of age, sex, presence of pre-existing disc pallor in one eye, previous use of diethylcarbamazine citrate, or doses of ivermectin or placebo received. There was evidence that ivermectin reduced the incidence of OND in subjects with microfilarial loads above 10 mf/mg but had little effect in those with lower loads. Sustained annual delivery of ivermectin could prevent a substantial proportion of onchocercal blindness in mesoendemic communities.