|Year : 2002 | Volume
| Issue : 2 | Page : 127-130
Visual field defects in non-functioning pituitary adenomas.
R Thomas, K Shenoy, Mandalam S Seshadri, J Muliyil, A Rao, P Paul
Department of Ophthalmology, L V Prasad Eye Institute, L V Prasad Marg, Banjara Hills, Hyderabad-500 034, India
Department of Ophthalmology, L V Prasad Eye Institute, L V Prasad Marg, Banjara Hills, Hyderabad-500 034
Source of Support: None, Conflict of Interest: None
PURPOSE: To report the prevalence and pattern of visual field loss in non-functioning pituitary adenomas and to study the relationship between the tumour size and severity of field defects. METHODS: Ninety-three patients with histologically confirmed pituitary adenomas, non-functional on hormonal assessment, underwent a complete ophthalmic assessment and automated perimetry using the HFA 30-2 programme. Defects with quadrantanopic or hemianopic characteristics, defined using criteria on the threshold/pattern deviation plots were considered typical. Typical defects were graded as mild, moderate and severe. All other defects were considered atypical. A neuroradiologist measured tumour size on a CT or MRI Scan. The Chi-square test for trend was used to test association of tumour volume with severity of typical defects. RESULTS: Eighty-eight (94.6%) of the 93 patients had a field defect. Typical field defects were seen in 69 (74.2%) patients and atypical in 19 (20.4%). A severe typical defect involving at least 3 quadrants in one or both eyes was the most common (24 patients or 25.80%). All 31 patients (33.3%) with a tumour size greater than 20 cc had field defects. Severity of field defect increased with tumour volume (Chi-square test for trends significant p = 0.0096). CONCLUSIONS: Field defects occurred in 95% of patients with non-functioning pituitary macroadenoma. A severe visual field loss involving at least 3 quadrants in one or both eyes was the most common. 20% of patients had atypical field defects. Severity of field defects increased with tumour volume
Keywords: Pituitary adenomas, field defects, automated perimetry
|How to cite this article:|
Thomas R, Shenoy K, Seshadri MS, Muliyil J, Rao A, Paul P. Visual field defects in non-functioning pituitary adenomas. Indian J Ophthalmol 2002;50:127-30
|How to cite this URL:|
Thomas R, Shenoy K, Seshadri MS, Muliyil J, Rao A, Paul P. Visual field defects in non-functioning pituitary adenomas. Indian J Ophthalmol [serial online] 2002 [cited 2020 Jun 4];50:127-30. Available from: http://www.ijo.in/text.asp?2002/50/2/127/14808
Pituitary tumours comprise 12 - 15 % of all intracranial tumours. A majority of these are histologically benign. Clinically, pituitary adenomas present as secretory or non-secretory tumours; visual manifestations are more common amongst non-functional adenomas. The prevalence of field defects in pituitary adenomas in general has been reported in various studies as 37 to 96 %.[3-6]
Automated static threshold perimetry is the current gold standard for visual field examination. While several studies have described the prevalence of field defects in pituitary adenoma, surprisingly few have used automated perimetry.[3-4] Furthermore, even those that utilized automated perimetry have not defined the criteria by which a defect was labeled as hemianopic. Using threshold and pattern deviation plot criteria to characterize field defects we report the prevalence and pattern of field changes in patients with non-functioning pituitary adenomas. We also report the relationship between tumour size and severity of field defects.
| Materials and Methods|| |
This non-concurrent prospective study was conducted in the departments of Ophthalmology and Endocrinology, Christian Medical College and Hospital, Vellore, between January 1995 and December 1997. Patients with nonfunctioning pituitary adenoma who fulfilled the following criteria were included in the study.
- 1. Radiologically confirmed pituitary tumours which were diagnosed to be non functional on hormonal assessment.
- 2. Availability of pre and postoperative visual fields. (This report is part of a larger study requiring pre-and postoperative fields for follow-up).
- 1. Coexisting cataract and/or glaucoma
- 2. Recurrence of tumour following previous surgery
- 3. Patients too ill to allow an adequate visual field assessment on automated perimetry.
In all patients the pituitary adenoma was considered responsible for the field defects.
A complete ophthalmic examination was performed, including biomicroscopy, applanation tonometry and indirect and stereobiomicrocopic fundus examination. Vision was assessed using Snellen's optotypes on a self-illuminated vision drum for distance.
| Fields Protocol:|| |
The 30-2 program on the Humphrey field analyzer (Humphrey Instruments model 630/640), with a white on white Goldmann Size III target was used for visual field evaluation. All patients underwent threshold strategy since suprathreshold strategy does not allow us to follow up the progress of a field defect. The reliability criteria used were fixation losses less than 20%, false positive and false negative errors less than 33%. Examination was repeated until reliable fields were obtained. Only those fields that were reliably performed were included in the analyses. All patients underwent visual field examination pre-operatively. Eyes with visual acuity less than 6/60 in the better eye also underwent field examination on the 30-2 programme with stimulus size III using the large or small diamond for fixation. According to the field defects patients were classified into the following subgroups:
- i) Quadrantanopia
- ii) Hemianopia
- iii) Hemianopic defect involving three or more quadrants, either unilateral or bilateral
- iv) One eye blind with contralateral temporal hemianopia
Quadrantanopia was diagnosed if either of the following criteria were fulfilled:
- 1. Depression of thresholds by 5 db or more, in 3 or more contiguous points adjacent to the vertical meridian in the involved quadrant as compared to their mirror image points across the vertical meridian.
- 2. The pattern deviation plot showed 3 or more points adjacent to the vertical meridian in the involved quadrant depressed to the 1 % probability level with normal mirror image points across the vertical meridian.
For the diagnosis of hemianopia, the diagnostic criteria for quadrantanopia had to be applicable to both quadrants comprising the hemifield.
Advanced field defects were considered hemianopic if comparison of the least involved quadrant across the vertical meridian, met the threshold depression criteria for the diagnosis of quadrantanopia. Here the pattern deviation plot criterion on its own was not considered diagnostic.
Atypical field defect was defined as a defect that did not fit into any characteristic diagnostic pattern considered typical of pituitary adenomas.
| Measurement of tumour size by CT or MRI Scan:|| |
The suprasellar extension of pituitary tumour was assessed radiologically on a CT or MRI scan with 5mm contrast and non-contrast axial slices. The tumour volume was calculated by the neuroradiologist using the following formula:
where a, b, c represent half the diameters in the three dimensions.
| Results|| |
The series included 103 patients with non-functioning pituitary adenomas. Of these nine were excluded because of non-availability of visual fields and one due to a co-existing cataract. The remaining 93 patients with non-functioning pituitary adenomas fulfilled the criteria and were included in the study. The mean age was 43 years (range 16-69 years). The male to female ratio was 2:1. The preoperative visual acuity is shown in [Table - 1]. Of the 93 patients, 88 (94.6%) had a visual field defect. Typical field defects were seen in 69 (74.2%) and atypical defects in 19 (20.4%) cases. The commonest defect in this series was field loss involving three quadrants; it was found in 24 (25.8%) patients. This was followed by bi-temporal hemianopia in 19 (20.4%) patients. Five (5.4%) of the 93 patients had normal fields. The pattern of field defects is shown in [Table - 2].
Tumour volume was calculated on the basis of CT/MRI findings. Patients with a volume more than 20 cc had a field defect. The field defect worsened with increase in tumour volume. The Chi-square test for trends for severe field defect (p = 0.0096) and severe visual loss ( p = 0.0158) was significant. The relationship between tumour volume and field loss is shown in [Table - 3] and the relation between tumour size and loss of visual acuity is shown in [Table - 4].
| Discussion|| |
Non-functioning pituitary adenomas constitute 25 - 30% of all pituitary tumours and present with predominantly ophthalmic features; field defects being the most common. Patients with pituitary macroadenomas may not have symptoms of visual disturbance, yet may have field defects consistent with compression of visual pathways. It is therefore important to perform field testing on patients with pituitary adenomas even if they have no visual complaints. Automated perimetry is a sensitive method for detecting visual field damage and quantifying treatment results. To the best of our knowledge there has been no comparative study between the automated perimetry and Goldmann manual perimetry for detecting visual field defects in pituitary adenomas (Medline search).
While several studies report the features and outcomes in pituitary tumours, findings in the nonsecretory adenomas have not been reported separately. Visual acuity better than 6/12 was found in 120 eyes (65%). Thirty-one (16.6%) had visual acuity less than 6/60. Other studies have reported the prevalence of "decreased" visual acuity between 16% to 46%, but the definition of "decreased" was not provided. [8,9]
Eighty-eight (95%) of our patients had field changes and showed a wide spectrum of defects. Involvement of at least three quadrants (unilateral or bilateral) was the most common defect seen in our series. Theoretically, chiasmal compression from pituitary tumours results in bi-temporal defects. These classical bi-temporal field defects were the second most common presentation in our study. Fields with no typical diagnostic pattern were seen in 19 (20%) patients. Such fields in other series constitute 4.7%. In another report, all cases had field defects, the commonest being bitemporal hemianopia (50%). None of these reports specify the testing methodology nor the criteria used to label the field defects.
The automated perimeter is the current gold standard for visual field testing. To the best of our knowledge, only two series have reported perimetry using these techniques. One study used the Topcon perimeter; patients with poor cooperation were tested on the Goldmann instrument. Another series used the 30-2 program of the Humphrey field analyzer. The most common field defect in both the series was bitemporal hemianopia, 62% and 45% respectively, whereas field defects including three or more quadrants were found in 5% and 14% respectively. This could be related to the fact that the series included all types of pituitary tumours. One of these reports is from a developed country, where early detection could explain the difference in presentation. Neither report defined the criteria by which field defects were characterized. All other reports relate to the Goldmann perimeter. [3, 4, 10]
Based on CT or MRI findings, we have also documented that a larger tumour at presentation is associated with more extensive and severe visual field defect as well as visual acuity loss. None of the 33 patients with a tumour volume above 20cc had a normal field; 3 of 33 patients had an atypical field defect. The rest were typical, mostly advanced. It would appear that automated perimetry is unlikely to miss a tumour with a volume above 20cc. On the other hand, even if the visual field is normal, a small tumour could be present.
In summary, visual field defects (detected by automated perimetry) occurred in 95% in this series of patients with non-functioning pituitary adenomas.
Advanced hemianopic defects were more common than classical bitemporal hemianopia. The severity of field defects and visual loss were related to tumour volume.
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[Figure - 1]
[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5], [Table - 6]
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