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| ORIGINAL ARTICLE |
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| Year : 2013 | Volume
: 5
| Issue : 2 | Page : 49-53 |
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Visual field deficit in diabetes mellitus in presence of no or minimal diabetic retinopathy
Galal Mohamed Ismail
Department of Neuroscience, Faculty of Optometry and Visual Science, Al Neelain University, Khartoum, Sudan
| Date of Web Publication | 10-Jan-2014 |
Correspondence Address:
Galal Mohamed Ismail
Faculty of Optometry and Visual Science, Al Neelain University, Khartoum
Sudan
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/1858-540X.124821
Introduction: Central visual field examination is a great clinical interest in diabetes mellitus, since changes in the visual field would be accepted as an indication of pathological condition. Hence, it is reflecting structural abnormalities in the ocular and the neural mechanisms of vision. The central visual field was examined in this study to investigate possible early changes in the macular area with a view to providing an assessment of early neural functional integrity in the presence of no or minimal diabetic retinopathy. Materials and Methods The investigation was carried out on a healthy visual system control group and a number of age-and sex-matched non-insulin dependent diabetic groups with different levels of diabetic retinopathy. The psychophysical test used was Oculus Tubingen perimeter. Results: The results were considered in terms of the presence of functional changes relative to the severity of retinopathy and the duration of diabetes. The visual fields test differentiated between normals and those with diabetes but with retinopathy. The test failed to differentiate between normals and diabetics without retinopathy. Conclusion: Visual filed defects are not strongly related to the duration of diabetes, but more to the severity of the retinopathy. They can be correlated to areas of capillary non-perfusion. Keywords: Diabetes mellitus, diabetic retinopathy, visual field defects
How to cite this article:
Ismail GM. Visual field deficit in diabetes mellitus in presence of no or minimal diabetic retinopathy. Sudanese J Ophthalmol 2013;5:49-53 |
How to cite this URL:
Ismail GM. Visual field deficit in diabetes mellitus in presence of no or minimal diabetic retinopathy. Sudanese J Ophthalmol [serial online] 2013 [cited 2023 Feb 7];5:49-53. Available from: https://www.sjopthal.net/text.asp?2013/5/2/49/124821 |
| Introduction | |  |
Visual field defects reflect structural abnormalities in the ocular and the neural mechanisms of vision. The central visual field was examined in this study to investigate possible early changes in the macular area. Central field defects have been reported in diabetes with and without retinopathy. [1],[2],[3] Such findings have implications in the screening and monitoring of diabetic retinopathy.
| Materials and Methods | | |
Using the Oculus Tubingen perimeter, the test was carefully explained to the subject. Subjects wore their optimal near refractive correction and were requested to rest their chins on the chin rest. The test was performed from a distance of 33 cm. Six visual field positions were tested and depicted graphically in [Figure 1]. The overall score was calculated by averaging the sum of all six threshold sensitivity values.
The non-insulin dependent diabetes patients were recruited from the University of Bradford Diabetic Retinopathy Screening Programme. Patients were not in a tight diabetic control; therefore they can be accepted as reflecting a real image of the diabetic population. The non-diabetic control group was recruited from patients, partners and members of the University in departments other than Optometry. Diabetics and non-diabetics tested within the same period of the study.
Subjects were excluded from the study if they had any sign of cataract within the undilated pupillary area using direct ophthalmoscopy, if they reported any major systemic pathology other than diabetes.
The age and duration of diabetes for all subject groups were normally distributed. [Table 1] shows the values for the mean, standard deviation and ranges of age for the subject groups who participated in the study. [Table 2] shows the values for the mean, standard deviation and ranges of diabetic duration for the subject groups who participated in the study. None of the age means were significantly different from each other (F 3,100 = 2.406, P > 0.05). | Table 1: Means table of the age of the subject groups, showing the standard deviation, range and sex distribution
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 | Table 2: Means table of the duration of diabetes for each diabetic subject group, showing the standard deviation and range
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Diabetic Retinopathy Grading Systems
Quantitative systems of grading retinal changes are more acceptable compared to qualitative systems in which statistical analysis is difficult to apply. Davis's diabetic retinopathy grading was employed to the present study. The classification was containing stages 10-70 (i.e., seven fields) and only grade 10, 20 and 30 groups were used. [4],[5]
| Results | | |
[Table 3] shows the visual field sensitivity scores with their associated standard deviation and standard error for each tested position and for all four subject groups. The data are represented graphically in [Figure 2]. A repeated measures analysis of variance (ANOVA) with 1 between-subjects factor (subject category) and 1 within-subjects factor (visual field position) was used to analyse the data [Table 4]. The analysis clearly shows the decrease in retinal sensitivity as a function of diabetic group (F 3,100 = 9.412, P < 0.0001). | Figure 2: Plot of visual field score against subject category for each visual field position
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 | Table 3: Means table for visual field score for each position and for each subject group
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 | Table 4: ANOVA table for the effect of field position and subject category upon visual field score
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Post-hoc analysis was performed using Scheffe's F-test in order to examine, which subject categories differed from one another in terms of visual field sensitivity. The results are shown in [Table 5], which demonstrates that the non-diabetic group differed from DRL group 20 and 30, but not from DRL group 10. Therefore, the central visual field measurements performed in this study are unable to distinguish between normals and those diabetics without retinopathy. The only other significant difference was between DRL group 20 and DRL group 30. | Table 5: Post-hoc comparison of visual field scores for each subject group
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The ANOVA presented in [Table 6] also demonstrates a just-significant effect of visual field position (F 5,500 = 2.471, P < 0.05). [Table 6] shows the mean sensitivity for the six field positions averaged across subject category. These are plotted in [Figure 3], which suggests that the significant effect of visual field position arises due to the lower sensitivity at position 1 [Figure 1] for positioning of the stimuli examined].
Correlation coefficients between duration of diabetes and visual field score, averaged across field position, was calculated for each subject group individually and found not significant. However, when all the diabetic subjects were considered together, the relationship reached significance (r = 0.38, P < 0.01) and is shown in [Figure 4]. The gradient of the relationship is −0.1324 asb/year. | Figure 3: Bar plot showing visual field score at each field location averaged across subject group. Standard errors are shown
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 | Figure 4: Relationship between visual field score averaged across field position and duration of diabetes
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 | Table 6: Means table for visual field scores at each field location averaged across subject group
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| Discussion | | |
Defects in the visual fields reflect the structural abnormalities in ocular and neural mechanisms of vision. The visual fields can be disturbed by diseases of the ocular media, retina or visual path way. Each defect has characteristic effects on the visual field. In diabetes, the visual fields defects are rarely considered to be the major feature of background and pre-proliferative retinopathy. [6],[7],[8] More recent studies have also found some evidence of visual field defects in their early diabetic groups compared with matched control groups. [9],[10],[11],[12] Chee and Flanagan found that the severity of field loss is associated with non-insulin diabetes mellitus and age. Trick et al. also noted that visual field defects occur more in non-insulin dependent patients, even in the absence of significant diabetic retinopathy. Jeddi et al. investigated 16 patients without diabetic retinopathy or with background retinopathy for central visual field. They found a deficiency of visual field in 35% of their cases.
On the other hand, Henricsson and Heijl investigated different stages of diabetic retinopathy using the Humphrey perimeter. They found no evidence of field loss in eyes with mild retinopathy, defects only becoming evident in eyes with more advance retinopathy. They reported that significantly reduced sensitivity was correlated with non-perfusion and there was a tendency toward a greater deficit in the midperiphery than paracentrally. [13]
The present results support the view that no significant paracentral visual field defect occurs in diabetics with no retinopathy (DRL10), although a highly significant effect occurs once retinopathy is present, i.e., for the DRL20 and DRL30 groups [Figure 2] and [Table 5]. When visual field sensitivity was correlated to the duration of diabetes a significant relationship was found, with a sensitivity loss approximating to 0.13 asb/year.
The loss of sensitivity as a function of subject category followed the same trend for each of the examined visual field positions [Figure 2], suggesting that the loss due to diabetes is diffuse rather than being concentrated to specific areas of the visual field. Overall sensitivity was, however, lowest in the superior visual field, a finding which is to be expected on the basis of the well-established oval-shaped visual field isopters, [14] which lie closest to the fovea in the superior visual field.
The methods used by Jeddi and Henricsson and Heijl are different from the method used in this study, as the former used automated perimetry and the latter data manual perimetry. Automated perimetric techniques are clearly more sophisticated than manual methods, but tend to be more time consuming. In addition, since the effects of diabetic retinopathy on the visual field tend to be diffuse, there may be little advantage to be gained in measuring thresholds at numerous locations throughout the visual field. Clearly, central field defects would be expected to increase rapidly with the increase of the diabetic retinopathy level beyond DRL30.
| Conclusion | | |
The results were interpreted in terms of the presence of functional changes relative to the severity of retinopathy and length of time the patient had been diagnosed as diabetic. They revealed significant deficit in visual function for visual filed. The deficit is not strongly related to the duration of diabetes, but more to the severity of the retinopathy. They can be correlated to areas of capillary non-perfusion.
| Acknowledgment | | |
The author would like to thank Professor David Whitaker for his help and support to study and analysis. My sincere thanks go to the participants, secretarial and technical personnel who organised for this study.
| References | | |
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| 13. | Sloan LL. Area and luminance of test object as variables in examination of the visual field by projection perimetry. Vision Res 1961;1:121-38.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]
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