Ординатура / Офтальмология / Английские материалы / Field of Vision A Manual and Atlas of Perimetry_Barton, Benatar_2003

DISCUSSION

Field description: Junctional scotoma, with diffuse loss OD and superior temporal quadrantanopia OS.

Localization: Junction of right intracranial optic nerve and optic chiasm. Pathology: Compression by anterior communicating artery aneurysm.

Tangent screen perimetry showed similar findings.

The patient has severe visual loss OD on perimetry (note, however, that even in this eye the loss as depicted on the sensitivity plot is more severe temporally). In the other eye, there is a superior temporal hemifield defect that respects the vertical meridian. These are the essential features of a junctional scotoma.

Coronal CT scan showed the large aneurysm in a location appropriate to compress the right optic chiasm and nerve anteriorly. Traditionally, a junctional scotoma is ascribed to compression of the termination of the optic nerve, where decussating fibers from the superior temporal field of the other eye were supposed to loop forward before passing posteriorly into the optic tract (115). Recent work has argued that this is an artifact (116). The combination may result instead from compression of both the terminal optic nerve and the adjacent inferior optic chiasm. The clinical implication remains the same, however. Perimetry in all cases of optic neuropathy should examine the superior temporal field of the opposite eye, because a defect there changes the differential diagnosis from one of optic neuropathy to that of lesions of the optic chiasm. Most lesions of the chiasm are masses, which is not true of optic neuropathy.

HISTORY AND EXAM

During the last week of her pregnancy, this 20-yr-old woman had bitemporal headache and blurred and decreased color vision in the left eye. When seen 2 days following deliv-

ery, the headaches were much improved. Visual acuity was 20/20 OD and 20/40 OS with an RAPD OS. There was red desaturation OS. Optic disks were normal.

DISCUSSION

Field description: Central scotoma in the left eye with a superotemporal vertical step. Localization: Intracranial left optic nerve and chiasm.

Pathology: Lymphocytic hypophysitis.

The initial field showed a large central scotoma, which might suggest an optic neuritis in a young woman. However, the key finding is the vertical step in the I4e isopter superiorly. No optic neuropathy does this.

T1-weighted coronal MRI showed a moderately enlarged pituitary gland abutting the optic chiasm (arrow), with homogeneous enhancement. Over the next 2 weeks, the vision OS worsened to count fingers and repeated visual field testing (this page) showed temporal hemifield defect OD and only a remaining nasal and inferior temporal islands of vision OS. This clearly indicated a lesion of the chiasm and left intracranial optic nerve. CSF was normal. Endocrine testing revealed low thyroid-stimulating hormone (TSH)

(<0.1) and low luteinizing hormone (LH) (<0.6). The patient was diagnosed with lymphocytic hypophysitis and treated with iv methylprednisolone, with visual fields returning to normal 1 month later.

A chiasmal lesion in late pregnancy or the postpartum period suggests lymphocytic hypophysitis, postpartum pituitary necrosis (Sheehan syndrome), or pituitary adenoma. The lack of mass effect or hemorrhage on MRI is against the latter two, and more consistent with an inflammatory process. The management of lymphocytic hypophysitis is not well established (114). If headache and visual symptoms are mild, close observation is appropriate. Progressive visual loss should prompt trans-sphenoidal biopsy. If this shows lymphocytic infiltration without tumor, decompression without removal of the pituitary gland should be performed. The efficacy of corticosteroids is unproven. Hormone replacement may be needed.

HISTORY AND EXAM

This 51-yr-old man with hypercholesterolemia had gradual deterioration over a few years in the vision of the right eye, affecting the central and temporal field. More recently, he occasionally missed words on the left side of the page when reading with both eyes

open. Visual acuity was 20/400 OD and 20/25 OS, and there was a prominent RAPD OD. There was marked diffuse optic disk pallor OD and bowtie optic atrophy OS. The remainder of the neurologic examination was normal.

DISCUSSION

Field description: Bitemporal hemifield loss, more superior OS, with additional central scotoma OD.

Localization: Optic chiasm and right intracranial optic nerve. Pathology: Prolactin (PRL)-secreting pituitary macroadenoma.

Other features: Bowtie atrophy.

The patient has dense superior loss with lesser inferior central depression OS (note that the smallest I2e isopter is only a semicircle, missing its left hemifield portion). There is complete loss of the temporal hemifield OD with extension into the nasal field centrally, indicating an added central scotoma OD from compression of the distal right optic nerve.

As with Case 58, the more severe superior loss in the temporal defect OS suggests compression of the decussating fibers in the inferior optic chiasm, from a mass below.

T1-weighted coronal MRI demonstrated a huge enhancing multilobulated tumor with cystic components, arising from the pituitary with lateral extension into the cavernous sinus, encasement of the left internal carotid, and downward extension into the sphenoid sinus. Serum PRL was markedly elevated at 2500 (normal: <25). Follicle-stimulating hormone, LH, and TSH were normal. The patient was started on cabergoline, a dopamine agonist similar to bromocriptine, but he developed a sudden severe headache from pituitary apoplexy, necessitating surgical decompression.

Bowtie (band) optic atrophy (see case 69) is a classic finding with long-standing compression of fibers from the nasal hemiretina (temporal hemifield), in either the optic chiasm or the optic tract (117). The superior and inferior aspects of the optic disk are spared the atrophy, because they are occupied by the arcuate fibers arching in from the temporal hemiretina, around the papillomacular bundle (see Chapter 2).

HISTORY AND EXAM

This 61-yr-old woman reported gradually progressive visual loss in the left eye over 5 months. In the days prior to presentation, she could not read the numbers on her bedside clock. Vision was worst in the center and in the temporal field. She had glaucoma in the right eye and an iatrogenic peripheral neuropathy following cisplatin treatment for

ovarian cancer. Acuity was 20/20 OD and 20/40 OS. Ishihara color plates were 13/14 OD and 9/14 OS. Fundoscopy showed normal disks. The remainder of the neurologic examination was normal, apart from the peripheral neuropathy.

DISCUSSION

Field description: Bitemporal hemifield defects with superior nasal step OD. Localization: Optic chiasm and optic nerve OD.

Pathology: Meningioma.

Confrontation testing was normal OD and showed decreased color and hand comparisons temporally OS.

In addition to the by-now familiar bitemporal depressions in the central field that align along the vertical meridian, the patient has a curious superior nasal step respecting the horizontal meridian OD, indicating damage to the right optic nerve (which could be from her glaucoma too). Enhanced axial T1-weighted MRI demonstrated a parasellar menin-

gioma with compression of the optic chiasm (note the optic tracts emerging just behind the bright mass, arrows).

Visual loss with or without nonspecific headaches is the most common presentation of patients with meningiomas of the sella or medial sphenoid ridge. Gradually progressive asymmetric visual field loss is the rule. However, acute onset with fluctuations over weeks or months may also occur, mimicking optic neuritis (see Case 67). Surgery remains the mainstay of therapy for patients with meningiomas involving the intracranial optic nerve and chiasm. Radiotherapy reduces the risk of recurrence when surgical removal has been incomplete. The visual outcome is related primarily to the duration of symptoms.

HISTORY AND EXAM

This 34-yr-old healthy woman suddenly noted painless decreased vision in the right eye 1 year earlier, which partly improved a month later and was diagnosed as optic neuritis. However, the vision of this eye continued to fluctuate. In particular, it always seemed to deteriorate 10 days before her menstrual period and improve at its end. In the preceding few months, the vision of the left eye also started to appear “washed out” or

pale. Acuity was 20/100 OD and 20/25 OS. She read 7/14 Ishihara color plates OS. There was an RAPD OD and optic disk pallor OD. Visual fields were obtained at the initial visit (top), then during (middle) and at the end (bottom) of a menstrual period, as depicted in this overview plot of the two eyes.

DISCUSSION

Field description: Diffuse depression with temporal hemifield defect OD, inferior arcuate defect OS.

Localization: Intracranial optic nerves and chiasm. Pathology: Compression by meningioma (shown below).

Note that on May 24, 1991, the patient has thresholds of 0 dB in almost the entire temporal hemifield and inferonasal quadrant OD, with the defect aligning along the vertical meridian in the superior field. On the same day, the field OS shows a typical inferior arcuate defect arching out of the blind spot on the gray-scale image and ending in a nasal step at the horizontal meridian, best seen on the total deviation plot. Five days later, on May 29, with her menstrual period ending, there is already evident improvement in both eyes, with the mean deviation (MD) of both eyes improving by about 3–4 db, confirming her own observations.

The history of acute visual loss with improvement suggested optic neuritis. In retrospect, she had probably suddenly noticed a visual loss that had been present for some

time. Recurrence of optic neuritis does occur (see Case 25), but frequent predictable relapses timed to the menstrual cycle are definitely odd. This history, verified by perimetry, suggests a hormonally sensitive tumor. Some meningiomas contain estrogen receptors and can fluctuate in this manner.

Suprasellar meningiomas frequently express estrogen and progesterone receptors and may enlarge under the influence of these hormones, particularly during the second half of pregnancy (118). Cyclical enlargement and shrinkage of these hormone-sensitive meningiomas may also occur concurrent with the hormonal fluctuations that accompany menstrual cycles. In a similar vein, the pituitary gland enlarges slightly during pregnancy principally because of hypertrophy of the PRL-secreting cells. However, under normal circumstances, the chiasm is situated about 4–10 mm above the diaphragm sella, so visual symptoms due to changes in the size of the pituitary should not occur in the absence of an underlying macroadenoma (119).

HISTORY AND EXAM

This 26-yr-old man had 1 year of unusual persistent headaches and 3 months of blurry peripheral vision in both eyes that had gradually encroached on central vision. He then found that letters disappeared or doubled vertically or horizontally when he tried to read. His doctor discovered hypothyroidism with a low TSH and obtained brain imaging. He

was treated surgically a few days prior to evaluation and the reading disturbance resolved, but his peripheral vision to the left seemed worse. His acuity was 20/20 OU and there was an RAPD OS. Optic disks showed temporal pallor OU. Eye movements were normal.