Outcomes of referrals by community optometrists to a hospital glaucoma service

Improving access to optometry services for people at risk of preventable sight loss: a qualitative study in five UK locations

Background

Reducing preventable sight loss is an increasing priority for public health and health care providers. We examined the factors affecting people's use of optometry services in population groups at increased risk of sight loss.

Methods

This is a qualitative study in five UK locations. In England, participants were from the Pakistani and Black Caribbean communities; in Scotland from the Pakistani community; and in Northern Ireland and Wales from white socio-economically deprived communities. Thirty-four focus groups were conducted (n = 289). The study included people who attend optometry services and people not engaged with services.

Results

Barriers to access included limited awareness of eye health and eye disease, concern about the cost of spectacles and the appropriateness of optometry in a commercial setting. Attendance at the optometrist was primarily symptom led. A positive previous experience or continuing relationship with the optometrist helped to alleviate the barriers and promote attendance.

Conclusion

Addressing the disparity between the broader messages about eye health and the current perception of the function of optometry could help improve access to services. Uptake may be improved through the co-production of interventions that better resonate with local communities. Non-retail service delivery options should be explored.

Levels of state and trait anxiety in patients referred to ophthalmology by primary care clinicians: a cross sectional study

Purpose

There is a high level of over-referral from primary eye care leading to significant numbers of people without ocular pathology (false positives) being referred to secondary eye care. The present study used a psychometric instrument to determine whether there is a psychological burden on patients due to referral to secondary eye care, and used Rasch analysis to convert the data from an ordinal to an interval scale.

Design

Cross sectional study.

Participants and Controls

322 participants and 80 control participants.

Methods

State (i.e. current) and trait (i.e. propensity to) anxiety were measured in a group of patients referred to a hospital eye department in the UK and in a control group who have had a sight test but were not referred. Response category analysis plus infit and outfit Rasch statistics and person separation indices were used to determine the usefulness of individual items and the response categories. Principal components analysis was used to determine dimensionality.

Main Outcome Measure

Levels of state and trait anxiety measured using the State-Trait Anxiety Inventory.

Results

State anxiety scores were significantly higher in the patients referred to secondary eye care than the controls (p<0.04), but similar for trait anxiety (p>0.1). Rasch analysis highlighted that the questionnaire results needed to be split into “anxiety-absent” and “anxiety-present” items for both state and trait anxiety, but both subscales showed the same profile of results between patients and controls.

Conclusions

State anxiety was shown to be higher in patients referred to secondary eye care than the controls, and at similar levels to people with moderate to high perceived susceptibility to breast cancer. This suggests that referral from primary to secondary eye care can result in a significant psychological burden on some patients.

The effectiveness of schemes that refine referrals between primary and secondary care--the UK experience with glaucoma referrals: the Health Innovation & Education Cluster (HIEC) Glaucoma Pathways Project

OBJECTIVES

A comparison of glaucoma referral refinement schemes (GRRS) in the UK during a time period of considerable change in national policy and guidance.

DESIGN

Retrospective multisite review.

SETTING

The outcomes of clinical examinations by optometrists with a specialist interest in glaucoma (OSIs) were compared with optometrists with no specialist interest in glaucoma (non-OSIs). Data from Huntingdon and Nottingham assessed non-OSI findings, while Manchester and Gloucestershire reviewed OSI findings.

PARTICIPANTS

1086 patients. 434 patients were from Huntingdon, 179 from Manchester, 204 from Gloucestershire and 269 from Nottingham.

RESULTS

The first-visit discharge rate (FVDR) for all time periods for OSIs was 14.1% compared with 36.1% from non-OSIs (difference 22%, CI 16.9% to 26.7%; p<0.001). The FVDR increased after the April 2009 National Institute for Health and Clinical Excellence (NICE) glaucoma guidelines compared with pre-NICE, which was particularly evident when pre-NICE was compared with the current practice time period (OSIs 6.2-17.2%, difference 11%, CI -24.7% to 4.3%; p=0.18, non-OSIs 29.2-43.9%, difference 14.7%, CI -27.8% to -0.30%; p=0.03). Elevated intraocular pressure (IOP) was the commonest reason for referral for OSIs and non-OSIs, 28.7% and 36.1%, respectively, of total referrals. The proportion of referrals for elevated IOP increased from 10.9% pre-NICE to 28.0% post-NICE for OSIs, and from 19% to 45.1% for non-OSIs.

CONCLUSIONS

In terms of 'demand management', OSIs can reduce FVDR of patients reviewed in secondary care; however, in terms of 'patient safety' this study also shows that overemphasis on IOP as a criterion for referral is having an adverse effect on both the non-OSIs and indeed the OSIs ability to detect glaucomatous optic nerve features. It is recommended that referral letters from non-OSIs be stratified for risk, directing high-risk patients straight to secondary care, and low-risk patients to OSIs.

Comparison of optometrist glaucoma referrals against published guidelines

PURPOSE

To examine if community optometrists follow published guidelines for referral of patients with suspect glaucoma to the hospital eye service.

METHODS

A retrospective audit of new optometrist-initiated referrals to the Glaucoma Service at Moorfields Eye Hospital, London was performed. Clinical data from referral letters recorded included evidence of intraocular pressure (IOP) measurement and tonometer used. Referral letter information was compared to 2009 guidelines published jointly by the College of Optometrists and Royal College of Ophthalmologists on referring glaucoma suspect patients.

RESULTS

A total of 289 new patients were seen in the Glaucoma Service over a 6 week period from 4th January 2011; a 100% hospital record retrieval rate was obtained. Of these, 114 (39%) were optometrists initiated referrals. Optometrist letters were available for 105 patients. IOP measurements were recorded in 102 (97%); most practitioners used non-contact tonometry (NCT; n = 69; 68%). Practitioners recorded <4 NCT readings per eye (4 readings: n = 3, 4%; 3 readings: n = 42, 61%; 2 readings: n = 6, 9%; 1 reading: n = 18, 26%). Seventy-seven patients (73%) reported with raised IOP as the main referral reason; of these, 33 (43%) were referred with raised IOP in isolation. NCT was the instrument used in the majority of these raised IOP cases (n = 56; 73%). In cases where raised IOP in isolation was the referral reason, 24 (73%) were recorded using NCT; 10 (30%) provided repeat IOP measurement data in the letter. One hundred and two (97%) referred patients attended the hospital appointment. Thirty (29%) were deemed not to have glaucoma, with the remainder diagnosed with ocular hypertension (n = 25; 25%), glaucoma suspect/glaucoma (n = 35, 34%) or narrow angles requiring intervention (n = 12, 12%). Thirty of the 33 patients referred with raised IOP in isolation attended their hospital visit. Ten (33%) of these patients were subsequently discharged. Six (20%) patients had IOP within normal limits when measured with applanation tonometry; all of these patients were kept within the service.

CONCLUSIONS

Community optometrists using NCT for measurement should be reminded of the guidelines on number of readings to take and also the value of repeating NCT measures when appropriate. This may help to increase the accuracy of glaucoma suspect referrals to hospital eye service.

Evaluation of the effectiveness of ophthalmic assistants as screeners for glaucoma in North India

AIM

To assess whether ophthalmic assistants are effective in screening people for glaucoma in India.

METHODOLOGY

The study subjects were examined by both trained ophthalmic assistants and an ophthalmologist in both hospital and community settings. Specific tests for the diagnosis of glaucoma suspects included visual field examination using frequency doubling technology perimetry, intraocular pressure measurement (Tonopen), A-scan central anterior chamber depth measurement and dilated optic disc examination. The findings recorded by the ophthalmic assistants were masked to the ophthalmologist to avoid measurement bias.

RESULTS

In the hospital setting, there was a substantial level of agreement between the ophthalmic assistants and the ophthalmologist in the diagnosis of glaucoma suspects (89.29%, k=0.7, 95% confidence interval (CI)=0.54-0.86). The diagnostic accuracy of the ophthalmic assistants in detecting glaucoma suspects was high for sensitivity (95.2%, 95% CI=91.4-97.7%) but lower for specificity at 71.4% (95% CI=60.0-78.7%).In the community setting, there was a moderate level of agreement between the ophthalmic assistants and the ophthalmologist in the diagnosis of glaucoma suspects (78.23%, k=0.50, 95% CI=0.37-0.64). The diagnostic accuracy of the ophthalmic assistants in detecting glaucoma suspects was moderate for sensitivity (82.9, 95% CI=69.7-91.5%) but lower for specificity at 76.8% (95% CI=72.7-79.5%).

CONCLUSION

Ophthalmic assistants can be used for opportunistic case detection of glaucoma suspects in the community. Structured training of the ophthalmic assistants together with enhanced clinical experience would improve their performance in detecting glaucoma suspects in the community.

Glaucoma screening Platform Study group, Burr JM, Campbell MK, Campbell SE, Francis JJ, Greene A, Hernández R, Hopkins D, McCann SK, Vale LD. Developing the clinical components of a complex intervention for a glaucoma screening trial: a mixed methods study

BACKGROUND

Glaucoma is a leading cause of avoidable blindness worldwide. Open angle glaucoma is the most common type of glaucoma. No randomised controlled trials have been conducted evaluating the effectiveness of glaucoma screening for reducing sight loss. It is unclear what the most appropriate intervention to be evaluated in any glaucoma screening trial would be. The purpose of this study was to develop the clinical components of an intervention for evaluation in a glaucoma (open angle) screening trial that would be feasible and acceptable in a UK eye-care service.

METHODS

A mixed-methods study, based on the Medical Research Council (MRC) framework for complex interventions, integrating qualitative (semi-structured interviews with 46 UK eye-care providers, policy makers and health service commissioners), and quantitative (economic modelling) methods. Interview data were synthesised and used to revise the screening interventions compared within an existing economic model.

RESULTS

The qualitative data indicated broad based support for a glaucoma screening trial to take place in primary care, using ophthalmic trained technical assistants supported by optometry input. The precise location should be tailored to local circumstances. There was variability in opinion around the choice of screening test and target population. Integrating the interview findings with cost-effectiveness criteria reduced 189 potential components to a two test intervention including either optic nerve photography or screening mode perimetry (a measure of visual field sensitivity) with or without tonometry (a measure of intraocular pressure). It would be more cost-effective, and thus acceptable in a policy context, to target screening for open angle glaucoma to those at highest risk but for both practicality and equity arguments the optimal strategy was screening a general population cohort beginning at age forty.

CONCLUSIONS

Interventions for screening for open angle glaucoma that would be feasible from a service delivery perspective were identified. Integration within an economic modelling framework explicitly highlighted the trade-off between cost-effectiveness, feasibility and equity. This study exemplifies the MRC recommendation to integrate qualitative and quantitative methods in developing complex interventions. The next step in the development pathway should encompass the views of service users.

Assessment of referrals to the hospital eye service by optometrists and GPs in Bradford and Airedale

PURPOSE

To investigate the content of referrals to a hospital eye department and describe differences between referring clinician (optometrist or GP) and referral formats.

METHODS

A random sample of 433 new referrals to Bradford Royal Infirmary hospital eye service (HES) during 2007 and 2008 were retrospectively analysed.

RESULTS

Three hundred and eleven referrals (72%) were from optometric practice and 122 (28%) from general practice. Optometric referrals were mainly for cataract and posterior capsular opacification (27%), glaucoma or suspect glaucoma (20%) and diabetic retinopathy (10%).

CONCLUSIONS

The proportion of referrals to the hospital eye service from optometrists appears to be increasing (1988: 39%, 1999: 48%, present study 72%). GPs mainly refer patients with anterior segment disorders, particularly lid lesions, based on direct observation and symptoms. Optometrists refer patients with a wide range of ocular diseases and include fundus observations and visual acuity measurements in their referrals. There is a need to inform optometrists of what content is required in a referral to the HES from GOS sight tests, at least for the common referral conditions such as age-related cataract and suspect open-angle glaucoma. Referral forms specifically designed for these commonly referred conditions are likely to improve referral quality.

Optometrists referrals for glaucoma assessment: a prospective survey of clinical data and outcomes

AIM

The aim of this study is to determine the outcomes following referral for glaucoma from routine optometric practice and the positive predictive value (PPV).

METHODS

A prospective study of 441 referrals for glaucoma in the Portsmouth area was performed over 6 months. A positive outcome was defined when the patient had the diagnosis of glaucoma made or if there was a high index of suspicion of glaucoma requiring follow-up. The PPV was determined from positive outcome number/referral number.

RESULTS

The overall PPV was 0.37 (95% confidence interval 0.33-0.42). Open-angle glaucoma (OAG) was confirmed in 33 (7%) patients. A diagnosis of ocular hypertension was made in 49 (11%) patients and glaucoma suspect in 92 (21%) referrals. Two-thirds of optometrists recorded all 3 assessments: fields, intraocular pressure (IOP) and disc appearance, a figure representing 293 referrals (PPV 0.37). However the greatest referral accuracy was seen when only discs and IOPs were recorded (PPV 0.47). When all three tests were given as reasons for suspicion for glaucoma, the PPV was 0.71. The number of patients diagnosed with OAG from Portsea Island during the study period was 7, whereas the expected number of diagnosed patients was 29.

CONCLUSION

Wider use of perimetry by optometrists and increased reporting of all three tests has not led to an increase in PPV. There remain a considerable number of undiagnosed patients with glaucoma in the population.

The Peterborough scheme for community specialist optometrists in glaucoma: a feasibility study

PURPOSE

This study assessed the role of specialist optometrists who were working in the community and sharing the care for glaucoma patients with, and under close supervision of, a consultant ophthalmologist working in the Hospital Eye Services (HES) to ensure high-quality standards, safety, and care.

METHODS

From February 2005 onwards, the majority of all new glaucoma referrals to our eye department were diverted to our specialist optometrists in glaucoma (SOGs) in their own community practices. Selected patients in the HES setting who were already diagnosed with stable glaucoma were also transferred to the SOGs. The completed clinical finding details of the SOGs, including fundus photographs and Humphrey visual field tests, were scrutinised by the project lead.

RESULTS

This study included 1184 new patients seen by specialist optometrists between February 2005 and March 2007. A total of 32% of patients were referred on to the hospital, leaving the remaining 68% patients to be seen for at least their next consultation in the community by the SOGs. The following levels of disagreement were observed between SOGs and the project lead: on cup:disc ratio (11%), visual field interpretation (7%), diagnosis (12%), treatment plan (10%), and outcome (follow-up interval and location) (17%).

CONCLUSION

This study indicates that there is potential for a significant increase in the role of primary care optometry in glaucoma management. The study also confirms a need for a significant element of supervision and advice from a glaucoma specialist. The important issue of cost effectiveness is yet to be confirmed.

The quality of optometrists' referral letters for glaucoma

PURPOSE

The purpose of the study was to evaluate the quality of content of optometrist-initiated glaucoma referral letters arriving at the appointment booking centre at Moorfields Eye Hospital (MEH).

METHODS

The minimum standard of information required for an ophthalmologist to determine the appropriateness and urgency of glaucoma suspect referral was determined, and criteria for three standards of referral letter formulated: 'Ideal', 'Acceptable' and 'Fail'. These standards were applied to a prospective review of all optometrist-derived referrals for glaucoma or suspected glaucoma cases arriving in the MEH booking centre over a 4-month period. The contents of each letter were scrutinised and classified based on the criteria within each standard.

RESULTS

Forty-nine per cent of referral letters were found to be of 'acceptable' quality, 7%'ideal' quality and the remainder classed as "fail". The main reason for failure was an omission of non-clinical information, including patient and/or referring practice details, although 26% of letters failed to include an optic disc evaluation and 6% failed to provide intra-ocular pressure measurements. Two-thirds of 'acceptable' letters did not reach the 'ideal' standard due to a lack of discussion of risk factors, visual field analysis or recommendations for referral speed.

DISCUSSION

The information gleaned from this prospective study indicates a need to improve the quality of optometrists' glaucoma referral letters, particularly with respect to completion of all the items set out on the General Ophthalmic Services (GOS) 18 referral form.

Referrals to ophthalmology: optometric and general practice comparison

PURPOSE

To assess referrals from primary care practitioners to an ophthalmological practice in order to determine whether any differences exist between the two primary care groups in the types of conditions referred, and in concurrence between reasons for referral and ophthalmological diagnosis.

METHODS

This study investigated patient referrals from general practitioners and optometrists to an ophthalmologist's practice in Belfast, over a period of 3 months from January 2007 to the end of March 2007. Anonymised data were divided into two groups depending on the referring practitioner. Within the two groups, patient numbers were sub-divided into 15 categories covering the range of diagnoses made. Preliminary diagnoses or reasons for referral were compared with the definitive diagnoses made by the ophthalmologist.

RESULTS

Optometrists contributed the greatest number of referrals (323) with 243 patients referred by general practitioners. Cataract was the most common condition referred by optometrists, and the second most common condition referred by general practitioners: agreement with ophthalmological diagnosis was high for both groups of primary care practitioners. Concurrence of referral reason with ophthalmological diagnosis for glaucoma was lower for general practitioners (56%) than for optometrists (76%), but optometrists referred more false positive patients for glaucoma than did general practitioners. The opposite was true for lid/tear duct/conjunctival conditions, the most common basis for referral by general practitioners.

CONCLUSIONS

The differences between the two primary care practitioner groups may reflect variations in training, skills and practice. Further investigation of the particular strengths of both groups, and how they can be optimised to promote effective shared care, is required.

The influence of the new general ophthalmic services (GOS) contract in optometrist referrals for glaucoma in Scotland

PURPOSE

To assess the quality of referrals from community optometrists in the northeast of Scotland to the hospital glaucoma service before and after the implementation of the new General Ophthalmic Services (GOS) contract in Scotland.

METHODS

Retrospective study encompassing two 6-month periods, one before the implementation of the new GOS (Scotland) contract in April 2006 (from June to November 2005), and the other after (from June to November 2006). The community optometrist referral forms and hospital glaucoma service notes were reviewed. Comparisons were performed using the t-test and chi (2)-test.

RESULTS

In all, 183 referrals were made during the first 6-month period from June to November 2005, and 120 referrals were made during the second 6-month period from June to November 2006. After the introduction of the new GOS contract, there was a statistically significant increase in true-positive referrals (from 18.0 to 31.7%; P=0.006), decrease in false-positive referrals (from 36.6 to 31.7%; P=0.006), and increase in the number of referrals with information on applanation tonometry (from 11.8 to 50.0%; P=0.000), dilated fundal examination (from 2.2 to 24.2%; P=0.000), and repeat visual fields (from 14.8 to 28.3%; P=0.004) when compared to the first 6-month period. However, only 41.7% of referrals fulfilled the new GOS contract requirements, with information on applanation tonometry the most commonly missing.

CONCLUSIONS

After the implementation of the new GOS (Scotland) contract in April 2006, there has been an improvement in the quality of the glaucoma referrals from the community optometrists in the northeast of Scotland, with a corresponding reduction in false-positive referrals. Despite the relatively positive effect so far, there is still scope for further improvement.

Glaucoma screening of patients with and without dementia

Glaucoma's damage to peripheral vision compromises mobility to a greater extent than ocular pathology limiting central vision. Half of glaucoma is undiagnosed, as the majority of primary care physicians do not screen for glaucoma. Glaucoma is more prevalent in older adults with dementia than without dementia. This study tested the hypothesis that, in adults 60 and older with dementia, glaucoma screening failure is significantly higher than without dementia. An observational cross-sectional research design with a categorical outcome variable was used. Potential participants/caregivers were questioned regarding glaucoma diagnosis and treatment. Those denying glaucoma or treatment qualified for free screening. Participants (n = 103) were 75% African American (75 females, 28 males, average age 75 +/- 7.59). Thirty-three had dementia. Referral rate with dementia was significantly higher than without dementia (54% vs. 27%, chi(2) = 7.32, p = 0.0007) (95% CI = 0.304-0.816), affirming the study hypothesis. Lack of glaucoma screening and treatment follow-up by a majority of primary care physicians treating geriatric patients demonstrates a need for medical professionals to address function, particularly mobility, to discuss glaucoma's effects with patients/caregivers, and to consider measuring intraocular pressure.

The accuracy of accredited glaucoma optometrists in the diagnosis and treatment recommendation for glaucoma

AIM

To compare the diagnostic performance of accredited glaucoma optometrists (AGO) for both the diagnosis of glaucoma and the decision to treat with that of routine hospital eye care, against a reference standard of expert opinion (a consultant ophthalmologist with a special interest in glaucoma).

METHODS

A directly comparative, masked, performance study was undertaken in Grampian, Scotland. Of 165 people invited to participate, 100 (61%) were examined. People suspected of having glaucoma underwent, within one month, a full ophthalmic assessment in both a newly established community optometry led glaucoma management scheme and a consultant led hospital eye service.

RESULTS

Agreement between the AGO and the consultant ophthalmologist in diagnosing glaucoma was substantial (89%; kappa = 0.703, SE = 0.083). Agreement over the need for treatment was also substantial (88%; kappa = 0.716, SE = 0.076). The agreement between the trainee ophthalmologists and the consultant ophthalmologist in the diagnosis of glaucoma and treatment recommendation was moderate (83%, kappa = 0.541, SE = 0.098, SE = 0.98; and 81%, kappa = 0.553, SE = 0.90, respectively). The diagnostic accuracy of the optometrists in detecting glaucoma in this population was high for specificity (0.93 (95% confidence interval, 0.85 to 0.97)) but lower for sensitivity (0.76 (0.57 to 0.89)). Performance was similar when accuracy was assessed for treatment recommendation (sensitivity 0.73 (0.57 to 0.85); specificity 0.96 (0.88 to 0.99)). The differences in sensitivity and specificity between AGO and junior ophthalmologist were not statistically significant.

CONCLUSIONS

Community optometrists trained in glaucoma provided satisfactory decisions regarding diagnosis and initiation of treatment for glaucoma. With such additional training in glaucoma, optometrists are at least as accurate as junior ophthalmologists but some cases of glaucoma are missed.

An analysis of patients discharged from a hospital-based glaucoma case-finding clinic over a 3-year period

PURPOSE

To analyse the false positive referrals by community optometrists to a glaucoma case-finding clinic over a 3-year period.

METHODS

A retrospective study was undertaken of the 531 patients who were referred by community optometrists and discharged after their first visit to the glaucoma case-finding clinic at the Oxford Eye Hospital between 2003 and 2005. The number of patients who were referred on the basis of one, two or three abnormal parameters was determined. The specific reason why the presumed abnormal parameter was considered normal by a glaucoma specialist was determined from the patients' records.

RESULTS

The referral was based on only one presumed abnormal parameter in 65.5-74.3% of patients (minimum-maximum percentage per year, 2003-2005). Physiological cupping was present in 21.5-29.5%, asymmetrical cupping because of asymmetrical disc size in 6.4-8.2% and asymmetrical cupping in the presence of similar disc size in 1.9-5.1%. An intraocular pressure (IOP) within the normal range was measured in 17.6-20.8% and an IOP between 22 and 25 mmHg in association with a central corneal thickness of >588 microm was found in a further 11.5-15.4%. In 11.5-16.1% of patients who were referred because of an abnormal visual field, no field defect was found when the test was repeated. A cause other than glaucoma was responsible for an abnormal visual field defect in 1.2-6%.

CONCLUSION

This study identifies the factors responsible for false positive referrals to a hospital-based glaucoma case-finding clinic. By considering these factors and by combining test data, the number of unnecessary referrals could be reduced in the future.

The role of scanning laser polarimetry using the GDx variable corneal compensator in the management of glaucoma suspects

AIM

To determine the role of scanning laser polarimetry using the GDx variable corneal compensator (VCC) in the management of glaucoma suspects.

METHODS

Over a 12-month period, 43 of 447 (9.6%) patients referred to a glaucoma screening clinic were classified as "glaucoma suspects" when it was not possible to categorise the optic disc appearance and visual fields as definitely glaucomatous or definitely normal. Of these patients, 39 underwent a full ophthalmic review, including assessment of the visual fields and analysis of the retinal nerve fibre layer with the GDx VCC.

RESULTS

After the review, 17 of 39 (43.6%) patients were discharged because of normal GDx VCC results. The remaining 22 of 39 (56.4%) were considered to be at risk of developing progressive glaucoma, and further follow-up in the hospital eye service was recommended. 3 (7.7%) patients received treatment. Of the 22 patients, 12 were considered to have pre-perimetric normal tension glaucoma, 7 normal tension glaucoma and 1 primary open-angle glaucoma (POAG). In 19 of these patients, abnormal GDx VCC results were found, particularly inter-eye asymmetry in the nerve fibre layer thickness. However, in 2 of 39 (5.1%) patients the GDx VCC was normal, despite the presence of a neuroretinal rim defect in the optic disc with corresponding visual field loss, and in 1 patient with POAG.

CONCLUSIONS

Scanning laser polarimetry using the GDx VCC is an important tool in defining the management strategies of glaucoma suspects. In screening for glaucoma, however, GDx VCC results should not be used in isolation, but in conjunction with conventional methods of optic disc and visual field assessment.