Reversible Changes in Frequency-Doubling Perimetry With TransientlyElevated Intraocular Pressure

Frequency-doubling technology (FDT) has been useful in screening patientsfor glaucoma.¹ One report shows that 1 dropof unoprostone could induce improvement with FDT by lowering intraocular pressureand increasing ocular blood flow.² We examined1 patient with secondary glaucoma and transient rise of high intraocular pressurewith FDT and with a Humphrey field analyzer (HFA) (Carl Zeiss Meditec, Inc,Dublin, Calif) for 1 year to study the effect of intraocular pressure on visualfield results.

A 33-year-old woman had had attacks of high intraocular pressure withslight inflammation several times in both eyes. Her visual acuity was 20/16.7OU. Fluorescein angiography showed no abnormal findings. With maximally toleratedtherapy, intraocular pressure remained higher than 40 mm Hg OS, and the patientunderwent trabeculectomy in that eye. Her left intraocular pressure stayedin the 20s after surgery. Her right intraocular pressure transiently roseto higher than 40 mm Hg with maximally tolerated therapy. The high pressuredecreased to normal levels within 1 month. The patient had large disc cuppingin the right eye; a 0.472 cup-disc ratio was determined using a retina tomograph(Heidelberg Engineering, Heidelberg, Germany). The HFA visual fields werealways normal independent of intraocular pressure for 1 year (Figure 1) (Table1) .The FDT, however, showed abnormal areas only twice during the same period,with high intraocular pressure (> 40 mm Hg) (Figure 2). On the same day in February 2002, when intraocular pressurewas 45 mm Hg, the FDT showed abnormal findings while the HFA appeared normal.During the final attack, 1% apraclonidine reduced intraocular pressure transientlyand improved the FDT mean deviation slightly in 1 hour (Figure 2 ). The FDT mean deviation correlated well with changesin the intraocular pressure, but not necessarily with the FDT pattern standarddeviation (Table 1). No inflammatorycells were seen in the anterior chamber of the right eye and no corneal edemawas observed during the attacks.

In this patient, visual field defects detected with FDT were thoughtto be due to elevated intraocular pressure. After reduction of intraocularpressure, the FDT mean deviation always showed improvement, even in 1 hour.Visual field loss with FDT under high intraocular pressure was reversible.The mechanism for this improvement was unclear. The FDT was thought to reflectthe function of relatively large retinal ganglion cells, called the M ganglioncells, since the FDT has large-sized (10°), high-temporal-frequency (25Hz) and low-spatial-frequency (0.25 candela/s) stimuli, inducing frequency-doublingillusion.³ The large retinal ganglion cellsthat may not be completely damaged under elevated intraocular pressure couldrecover when intraocular pressure was lowered. Another mechanism was improvementin corneal edema.⁴ No epithelial edema wasseen by slitlamp microscopy. Not only did diffuse loss mean deviation appear,but abnormal areas appeared with high intraocular pressure in the presentpatient. If corneal edema affected visual field, only diffuse loss would occur.Refractive error was corrected at examination of FDT. Good visual acuity wasmaintained under high intraocular pressure. In conclusion, FDT perimetry mayshow intraocular pressure–dependent, reversible changes.

Correspondence: Dr Fujimoto, 1-8-1 Inohana, Chuoku, Chiba 260-8670,Japan, Department of Ophthalmology and Visual Science, Graduate School ofMedicine, Chiba University (fujimoto@faculty.chiba-u.jp).

The authors have no relevant financial interest in this article.