NEWS & EVENTS
Retinal Review, Issue 13
CASE NUMBER 13
A 32 year old man was referred for vision loss left eye greater than right. He noted the gradual onset of vision loss over the past year. He did not report pain or photopsias. He reported no past ocular or medical history. There was no family history of ocular disease. He had seen several eye doctors over the past year and was given several pairs of glasses. None of the glasses improved his vision to a significant degree. He was referred to us to determine the cause of vision loss in a patient with a “normal” ocular examination.
On examination visual acuity was OD: 20/25 and OS: 20/100 ph 20/70. IOP’s were normal. The slit lamp examination was normal. There was a possible mild left afferent papillary defect. Color vision was full OD and mildly reduced OS. Dilated examination was unremarkable except for possible mild left optic nerve atrophy.
The patient was diagnosed with unexplained vision loss. He had both perceived and measured subnormal vision in both eyes with what appeared to be a relatively normal structural ocular examination. In cases like this a stepwise detailed approach to rule out subtle ocular diseases is necessary so that an abnormality will not be missed. Differential diagnosis for unexplained vision loss includes undiagnosed amblyopia, corneal irregularity (usually keratoconus), malingering, central nuclear sclerotic cataract (common in young myopes), central vitreous opacity, subtle macular disease, retinal vascular disease, and optic neuropathy. Typical tests include detailed refraction, cover testing to rule out microstrabismus (monofixation syndrome), detailed slit lamp examination, corneal topography, OCT, visual fields, and fluorescein angiography. Not all these tests are necessary of course, but some or all might be performed depending on the individual case.
Because of the possible optic nerve findings (trace afferent papillary defect, mild color vision deficit and optic nerve atrophy), we started with automated perimetry.
The patient was diagnosed with a bitemporal hemianopic visual field deficit with central scotoma OS > OD. Differential diagnosis includes pituitary tumor, chiasmal mass other than pituitary tumor (meningioma or neuroblastoma), demyelinating disease, and chiasmal arachnoiditis (TB or autoimmune disease). An MRI was scheduled.
Results of the MRI were compatible with a pituitary macroadenoma. The lesion measured 4 cm. and extended from the chiasm anteriorly to involve the left optic nerve. The cavernous sinus was not involved. Most macroadenomas are nonsecreting pituitary tumors and therefore the patient did not exhibit any hormonal abnormalities found in secreting pituitary tumors. He was referred to a neurosurgeon for management. Interestingly, many patients will recover all or part of their visual fields after successful treatment of the pituitary tumor. Optic nerve atrophy will usually remain.
This case underscores the need for a thorough, directed examination in patients with unexplained visual loss. Although the patient may be malingering or might have undiagnosed amblyopia, there are potential sight and life threatening conditions that can be diagnosed.