Given a passage, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.
Q: To investigate the alteration of the retinal nerve fiber thickness (NFLT) before and after vitreous surgery for a macular hole in cases with or without visual field defects.', 'The NFLT of 23 eyes with idiopathic macular hole was measured with scanning laser polarimeter upto 12 months after surgery. The NFLT was divided into superior, inferior, nasal, and temporal quadrants. The mean NFLT of each quadrant was analyzed statistically and compared to the results of visual field tests.', 'In all cases, the NFLT decreased significantly upto 3 months after surgery, but increased gradually upto 12 months. In cases with visual field loss, the thickness of the nerve fiber layer that corresponds to the visual field defect diminished strongly, in contrast with other quadrants. Even in cases without visual field loss, the NFLT decreased significantly a month after surgery, especially in the nasal and inferior quadrants.
A:
Does [ Thickness of retinal nerve fiber layer decrease after vitreous surgery for idiopathic macular hole ]?