PREVALENCE AND CHARACTERISTICS OF CENTRAL BINOCULAR VISUAL FIELD DEFECTS IN PATIENTS ATTENDING A GLAUCOMA PERIMETRY SERVICE

ANANTH C. VISWANATHAN,1,2 DAVID P. CRABB,3 FRED W. FITZKE1 and ROGER A. HITCHINGS2

1Institute of Ophthalmology, London; 2Moorfields Eye Hospital, London; 3Nottingham Trent University, Nottingham; UK

Background

Evidence suggests that, when the results of bilateral monocular visual field tests are merged by taking the higher decibel threshold value from either eye for each test location (the ‘best location’ algorithm), an accurate model of the binocular visual field is obtained.1,2 Furthermore, scores based on such integrated visual fields (IVFs) appear to correlate better with patient assessment of vision than the Esterman test.3

Since the level of binocular visual field loss is associated with vision-related quality of life4-6 and legal fitness to drive in the UK,7 we examined the prevalence and characteristics of binocular visual field defects in the Moorfields Eye Hospital Glaucoma service over a defined time period by constructing IVFs, where appropriate.

Methods

The following criteria were applied to obtain pairs of monocular visual fields for IVF construction:

•visual fields were from the Moorfields Eye Hospital Glaucoma Service database, which contains all visual field tests performed in the Service

•the observation period was from January 16th, 1985 to August 6th, 1997

•testing strategy 24-2 or 30-2

•white-on-white size III Goldmann equivalent stimulus

•reliable fields (fixation losses < 20%, false positives and false negatives < 33%)

•the first two fields for each eye were ignored to obviate learning effects8 From the monocular fields thus obtained, IVFs were constructed for patients who

had both eyes tested on the same day. On the rare occasions when a patient had more

Address for correspondence: A.C. Viswanathan, BSc(Hons), FRCOphth, MD, Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK. Email: a.viswanathan@ucl.ac.uk

Perimetry Update 2002/2003, pp. 83–85

Proceedings of the XVth International Perimetric Society Meeting, Stratford-upon-Avon, England, June 26–29, 2002

edited by David B. Henson and Michael Wall

© 2004 Kugler Publications, The Hague, The Netherlands

than one field test on each eye in the same day (39 of 15912 tests), the two monocular fields done earliest in the day were chosen, provided they satisfied the other criteria given above. IVF defects were defined as <10 dB to conform with the Esterman test. The IVF locations corresponding to either physiological blind spot were excluded from analysis: these locations are ignored when a patient’s legal fitness to drive a motor car is assessed in the UK.

Results

IVFs were constructed for 2567 patients. The majority (1326 patients) had only one pair of visual fields suitable for IVF construction, but a substantial minority were suitable for up to five IVFs to be constructed, and a few patients produced long series of IVFs. These results are displayed graphically in Figure 1.

Of the 2567 patients studied, 1523 (59.3%) had defects somewhere in at least one IVF, 518 (20.2%) were within the central 20 degrees and, 200 (7.8%) were in one of the four paracentral locations. In this last group, 15 patients had isolated IVF defects in the paracentral locations, with no defects anywhere else in the IVF. These defects would be missed by the Humphrey Esterman test: 12 of these 15 patients had visual acuities of 20/40 or better.

Fig. 1.

Discussion

It is not surprising that the number of IVF defects in the central 20 degrees (518, 20.2%) is less than half that anywhere in the IVF (1523, 59.3%), as the latter figure is likely to receive more of a contribution from artefacts, such as lens rim and ptosis, than the former. By the same token, the IVF defects in the central 20 degrees are more likely to represent genuine binocular scotomata.

The central 20 degrees of the binocular field is of particular importance regarding legal fitness to drive in the UK since a ‘significant scotoma’ in the central 20 degrees is sufficient for an individual’s driving license to be revoked. In the past, ‘significant scotoma’ has been interpreted as being a single missed point on the Esterman test (not corresponding to either blind spot). By this definition, one in five of the patients in our study population would be at risk for being classified as legally unfit to drive.

In contrast, this study also identified a small group of individuals whose binocular defects were confined to the four locations nearest fixation in the IVF. It seems reasonable to suggest that these paracentral locations are among the most important in terms of functional vision, yet they are not tested in the Esterman strategy. Furthermore, defects this close to fixation do not necessarily have an effect on visual acuity: 12 of these 15 patients had visual acuities of 20/40 or better. Although the IVF does not provide information about the visual field beyond 30 degrees, it is possible that some or all of these 12 patients would meet the UK visual field and acuity standards for legal fitness to drive, notwithstanding their binocular defects adjacent to fixation.

The findings of this study, as outlined in the previous two paragraphs, suggest a need to redefine the psychophysical basis of visual fitness to drive.

Acknowledgment

This work was funded by the International Glaucoma Association, UK, and the Medical Research Council, UK.

References

1.Crabb DP, Viswanathan AC, McNaught AI, Poinoosawmy D, Fitzke FW, Hitchings RA: Simulating binocular field status in glaucoma. Br J Ophthalmol 82(11):1236-1241, 1998

2.Nelson-Quigg JM, Cello K, Johnson CA: Predicting binocular visual field sensitivity from monocular visual field results. Invest Ophthalmol Vis Sci 41(8):2212-2221, 2000

3.Jampel HD, Friedman DS, Quigley H, Miller R: Correlation of the binocular visual field with patient assessment of vision. Invest Ophthalmol Vis Sci 43(4):1059-1067, 2002

4.Mills RP, Drance SM: Esterman disability rating in severe glaucoma. Ophthalmology 93(3):371-8, 1986

5.Parrish RK II, Gedde SJ, Scott IU, Feuer WJ, Schiffman JC, Mangione CM et al: Visual function and quality of life among patients with glaucoma. Arch Ophthalmol 115(11):1447-1455, 1997

6.Viswanathan AC, McNaught AI, Poinoosawmy D, Fontana L, Crabb DP, Fitzke FW et al: Severity and stability of glaucoma: patient perception compared with objective measurement. Arch Ophthalmol 117(4):450-454, 1999

7.Munton G: Vision. In: Taylor JF (ed) Medical Aspects of Fitness to Drive, 5th Edn, ch 11, pp 118132. London: The Medical Commission on Accident Prevention 1995

8.Werner EB, Krupin T, Adelson A, Feitl ME: Effect of patient experience on the results of automated perimetry in glaucoma suspect patients. Ophthalmology 97(1):44-48, 1990

AUTOMATED STATIC PERIMETRY IN THE YOUNG PEDIATRIC GROUP

Lessons from the Nintendo generation

STEVEN A. NEWMAN

University of Virginia, Charlottesville, VA, USA

Abstract

Purpose

To review the utility of automated static perimetry as a means of assessing the extrafoveal function in the young pediatric age group, a retrospective case-controlled series was assembled from files at the University of Virginia. Previous studies have demonstrated the ability of young children to perform automated static perimetry, but we were unaware of any attempts to apply this in a clinical setting.

Material and methods

Sixty thousand automated fields stored at the University of Virginia were screened for children aged ten years or younger. A total of 180 patients was selected. These patients had undergone a total of 538 visual fields. Fields were assessed for pattern of defect, reliability coefficients, and duration. Diagnoses were compared with results.

Results

Most common diagnoses included hydrocephalus and papilledema, closed head injury, and anomalous disc. Visual field patterns most frequently included arcuate defects, diffuse depression in sensitivity, and homonymous hemianopsia. Of the 52 fields run SITA Fast, duration ranged from 2:39 to 7:34 minutes, with a mean of 4:065 minutes. This contrasted with a duration of between 3:23 and 25:21 minutes when run full threshold (mean > 12 minutes). Of the 431 24-2 programs run with the full threshold strategy, 104 were identified as being non-reliable, based on fixation loss, false-positives, or false-negatives. In addition, 12 visual fields were uninterpretable despite acceptable reliability coefficients. This contrasted with a total of five of the 52 SITA Fast fields being identified as having greater than one in three false-positives or false-negatives. If the criteria were tightened to 27%, only eight of the 52 fields were unacceptable.

Conclusions

Children aged ten years or less are often capable of performing extraordinarily well on standard automated static perimetry. The introduction of SITA allows a tremendous decrease in the test time, with subsequent improvement in reliability coefficients. A subgroup of patients, particularly those who are ill or with severe optic nerve or visual pathway pathology, remain poor candidates for automated perimetry. In particular, problems maintaining attention and fixation remain paramount. Automated static perimetry is an appropriate standard extrafoveal function assessment, even in very young children.

Address for correspondence: S.A. Newman, MD, Department of Ophthalmology, University of Virginia, Box 475#1, Jefferson Park Ave, Charlottesville, VA 22906-0009, USA. Email: san7a@virginia.edu

Perimetry Update 2002/2003, p. 87

Proceedings of the XVth International Perimetric Society Meeting, Stratford-upon-Avon, England, June 26–29, 2002

edited by David B. Henson and Michael Wall

© 2004 Kugler Publications, The Hague, The Netherlands