Visual Field Defects in Patients with Pituitary Tumors
Overview
Automated perimetry is a standardized technique for assessing the visual field, commonly using the Humphrey Field Analyser (HFA) with the 24-2 or 30-2 test patterns. This study aimed to determine if the 24-2 test pattern could yield similar outcomes as the 30-2 pattern in detecting visual field defects in patients with pituitary tumors affecting the visual pathway.
Through a retrospective cohort study of patients with pituitary tumors causing visual pathway compression, 79 out of 133 participants underwent both the 30-2 and reduced 24-2 visual field tests. Visual field defect locations, visual acuity, mean deviation (MD), and visual field index (VFI) were analyzed.
Interestingly, no patient’s classification differed when assessed using the 24-2 pattern instead of the 30-2 pattern. While most patients exhibited visual field defects in the temporal visual field of each eye, a notable minority did not. Surprisingly, a considerable portion of patients had normal visual acuity (≥0.8).
The study concludes that employing the HFA 24-2 test pattern reliably identifies visual field defects caused by pituitary tumors. Furthermore, it suggests that MD and VFI might not be dependable parameters for assessing visual field defects resulting from compression.
Introduction
The visual pathway around the pituitary region is highly susceptible to damage, especially due to lesions like pituitary tumors, leading to various visual field defects. Pituitary adenomas, the second most common benign intracranial tumors, can cause visual loss and other neurological symptoms, necessitating surgical intervention. Visual dysfunction is often the primary symptom in such cases, with blurred vision and reduced peripheral vision being common complaints. The presentation duration of visual symptoms upon diagnosis varies.
Different patterns of visual field defects arise based on the affected area of the visual pathway. The outcome after decompression surgery ranges from permanent vision loss to complete recovery. The severity of pre-operative visual function loss significantly affects post-operative prognosis, while symptom duration alone doesn’t reliably predict the post-operative outcome.
Automated perimetry, introduced in the 1980s, offers a standardized method to assess the visual field. The Humphrey Visual Field Analyser (HFA) 30-2 and 24-2 applications are used to check factors inside the important visible field. This study aimed to determine if the 24-2 test pattern yields comparable information to the 30-2 pattern for detecting visual field defects in pituitary tumor patients. Investigating this can aid in optimizing testing duration, sensitivity, and specificity, thus aiding clinical decision-making for these patients.
Method
Inclusion Criteria
Patients with pituitary region tumors admitted for surgery at Skåne University Hospital, Lund, Sweden, between 2000 and 2020, who had undergone perimetry within 3 months before surgery were included.
Exclusion Criteria
Patients with other diseases causing visual field defects, monocular vision, or no signs of visual pathway compression in neuroradiology were excluded. Those unable to perform perimetry or exhibiting an unreliable false-positive rate of ≥15% were also excluded.
Visual Field Testing
Humphrey Field Analyzers were used for perimetric testing, employing the 30-2 test pattern. The results were analyzed using the Statpac Single-Field Analysis, providing numerical and grayscale maps of threshold values, deviations from normal values, and summary indices MD and VFI. Test points significantly depressed beyond p<0.005 were considered visual field defects.
Calculation of Visual Field Defect Distribution
To assess visual field defect distribution, the percentage of excess significantly depressed test points (SP) in temporal-nasal and superior-inferior directions was calculated for each patient. The visual fields of left and right eyes were compared, and the number of SP within the inner 24 degrees versus the outer 24–30 degrees of the visual field was analyzed as a percentage of the total SP.
This retrospective study aimed to determine the efficacy of visual field testing patterns in detecting defects related to pituitary tumors, aiding in optimizing test accuracy and reliability for patients’ benefit.
Statistical Analysis
Statistical analyses were conducted using GraphPad Prism version 8.4.3 for Windows (GraphPad Software). Chi-squared tests, Fisher’s exact test, and Pearson correlation tests were utilized to examine associations and relationships between variables.
Results
A retrospective cohort study was conducted on patients with pituitary region tumors who underwent visual field testing before surgery. From an initial pool of 133 patients, 79 (28 females and 51 males) were included after applying specific inclusion and exclusion criteria. Only patients with confirmed radiologic evidence of visual pathway compression, such as the optic nerves, chiasma, or optic tracts, were considered. The patients’ median age was 62 years, and the visual field tests were performed approximately 7 days prior to surgery. Visual acuity ≥0.8 was considered normal. The study revealed that nearly two-thirds of patients with visual field defects had adequate visual acuity. About 20% of patients exhibited small visual field defects, while a majority had mild depressions in mean deviation (MD) and visual field index (VFI), indicating relatively minor visual impairments.
The study investigated both the 30-2 and 24-2 test patterns to ascertain whether essential information about visual field defects was missed when analyzing the 24-2 data. It was found that no visual field defects were overlooked when considering the 24-2 data instead of the 30-2 data, implying comparable diagnostic accuracy between the two patterns. Visual field defect distribution analysis indicated that the majority of defects were primarily located in the temporal region of the visual field. Some patients had defects in the nasal or equally distributed regions. When examining different quadrants, visual field defects were more prevalent in the superior-temporal and inferior-temporal quadrants. Comparisons between the left and right eyes showed that while most patients had more defects in one eye, the cohort as a whole did not exhibit a consistent pattern in which eye was more affected.
Conclusion
The study focused on patients with pituitary region tumor-induced compression of the visual pathway and evaluated the efficacy of the 24-2 test pattern compared to the 30-2 test pattern in detecting visual field defects. None of the patients were missed when using the 24-2 test points, ensuring that clinical decision-making wasn’t compromised. Similar studies found equivalence between the two patterns in identifying visual field defects in patients with optic nerve disease or pituitary adenomas.
The study discussed varying criteria for abnormality assessment in perimetry, emphasizing the importance of adapting analysis methods to specific pathologies. Metrics like Mean Deviation (MD) and Visual Field Index (VFI) were found unreliable for evaluating visual field defects due to compression, as they didn’t consistently reflect the actual defects observed. The study noted the atypical distribution of defects in patients with pituitary tumors, where nasal defects were prevalent despite the common notion of bitemporal defects.
In conclusion, the study highlighted the adequacy of the 24-2 test pattern in detecting visual field defects in patients with pituitary region tumor-induced compression. It emphasized the importance of a critical approach to clinical data evaluation, considering the specific context and pathology.
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