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

DISCUSSION

Field description: Superotemporal depression OS, minimized by negative lenses. Localization: Globe/local refractive.

Pathology: Nasal fundus ectasia, tilted disc syndrome.

Confrontation testing with red targets but not other stimuli showed a subtle superotemporal field defect OS.

The field shows a mild superotemporal depression of the I4e isopter, and also of the I2e temporally. The temporal defect does not respect the vertical meridian or point in a wedge toward the optic disc. The I4e defect is accentuated by viewing with plus lenses (which shorten the focal length) and eradicated by viewing with minus lenses. This suggests a local elongation of the globe in the inferonasal region. Fundus pictures show a nasally tilted disc (black arrow) with peripapillary atrophy and hypopigmented inferior nasal retina (white arrow) OS. T2-weighted axial MRI confirms elongation of the nasal globe

(compare with right eye, shown here), and also shows anomalous tilted entry of the optic nerve to the globe (not shown).

Nasal fundus ectasia is a developmental anomaly in which the globe nasal to the optic disc is elongated—hence, the reversal of the normal tilt of the disc so that it now faces nasally (17). In 25% of individuals, the ectasia is unilateral. In 65%, the globe anomaly is associated with a nasal tilt of the disc—“tilted disc syndrome”—as here. The retina in the ectatic fundal zone is posterior to the plane of focus of the rest of the eye—essentially, a region of high myopia. The defocus creates a region of relative depression of visual sensitivity that is only present for the smaller targets (which are more dependent on precise focusing) and can be corrected or reduced by adding high negative diopter lenses. If bilateral, this condition may be mistaken for bitemporal hemianopia from compression of the optic chiasm. The lack of a vertical step defect at the meridian and the fundoscopic appearance are key to avoiding this confusion.

DISCUSSION

Field description: Nasal constriction OD, worse inferiorly, with a small dense hole.

Localization: Retina.

Pathology: Retinal detachment.

Confrontation fields showed a peripheral inferior quadrantic scotoma that did not approach either the horizontal or vertical meridians.

The patient has a nasal defect with shallow sloping borders that is more marked inferiorly, but that crosses both nasal horizontal and inferior vertical meridians without a step

defect. This makes it unlikely to represent optic neuropathy, and suggests retinal origin. Retinal detachment causes relative depression of vision in the area where the retina has detached from the underlying choroid. Detachment typically begins in the anterior retina (peripheral visual field) and extends posteriorly (into the central field) as the retinal detachment becomes more extensive. The defect tends to have a gradual sloping border with relative depression. This contrasts with retinoschisis, a separation within the layers of the retina itself that disrupts the connections between the inner and outer retina. Retinoschisis causes a dense absolute scotoma with sharp borders in the affected region.

DISCUSSION

Field description: Relative peripheral depression bilaterally, more marked on the right.

Localization: Retina.

Pathology: Vigabatrin toxicity.

Confrontation testing was normal OU.

At first glance, little appears to be abnormal about the patient’s field. However, for his age, the isopters are constricted in both eyes (see Chapter 4). ERG revealed that photopic (cone) b-wave amplitudes were reduced for single-flash stimuli and for 30-Hz flicker. Such abnormalities correlate strongly with the visual field constriction in vigabatrin toxicity (18).

Visual field defects are present in a proportion of patients taking vigabatrin. The most characteristic defect is a concentric narrowing of the field with preservation of central acuity and color vision. Most patients report no visual symptoms and the defect may be detected only with formal perimetry. Manual kinetic perimetry is most sensitive for demonstrating subtle peripheral depressions and contractions. Some investigators have observed a correlation between the presence of a visual defect and both the total dose and duration of therapy (19). Although cone function may improve following discontinuation of vigabatrin (shown by increased b-wave amplitudes under photopic conditions), it remains unclear whether the visual field defect is similarly reversible (20).

HISTORY AND EXAM

This 76-yr-old African-American woman had a 12-year history of primary open-angle glaucoma (POAG), currently being treated with topical latanaprost (a prostaglandin F2α analog that increases aqueous humor outflow) and dorzolamide (a carbonic anhydrase inhibitor that decreases aqueous humor production). She had also had bilateral cataract

extractions. Her visual acuity was 20/25 OD and 20/30 OS. Ishihara color scores were 13/14 OD and 14/14 OS. She had pale discs with moderate cupping OU. Intraocular pressures most recently were 27 mmHg OU, despite compliance with treatment. Over the previous 3 years they had ranged from 21 to 23 mmHg.

HISTORY AND EXAM

This 50-yr-old woman had been followed for 4 years for POAG. Her intraocular pressures had been borderline, around 21 mmHg OU. She was being treated topically with

timolol and latanoprost. Visual acuity was 20/20 OD and 20/30 OS. Intraocular pressures were 16 mmHg OD and 17 mmHg OS at this visit.

DISCUSSION

Field description: Superior temporal wedge defect OD, large superior arcuate defect OS.

Localization: Bilateral optic nerves. Pathology: Normal tension Glaucoma.

Initially the patient demonstrated a typical advanced glaucomatous defect OS, a severe arcuate defect that approaches an altitudinal loss in one eye, except that there is better residual sensitivity in the temporal portion (note the numbers on the sensitivity map), and an uncommon glaucomatous defect OD, a temporal wedge defect. Both are in the superior field, which is statistically more frequently involved by glaucoma, particularly normal tension glaucoma (22,23).

Over the subsequent 4 years this slowly worsened (fields this page), with deepening

of the superior loss in the temporal portion OS, and merging of the temporal deficit OD with a more typical nasal arcuate defect. In addition, some depressed points began to appear in the inferior fields of both eyes. Her optic discs (shown below) demonstrated optic disc pallor with cupping.

HISTORY AND EXAM

This 67-yr-old man was diagnosed with POAG at age 49. His mother had the same condition, with severe visual loss. His intraocular pressures were asymmetric early in the course of disease, being higher on the right, often in the low 20s (mmHg). He had been treated with timolol and pilocarpine eye drops for many years. His acuity throughout had

remained good, at 20/20 OU, with an RAPD OD. His optic discs showed pallor and cupping of the optic disc OD, with normal disc OS. Intraocular pressures on treatment have stabilized around 16 mmHg OU.