IMPROVING THE SENSITIVITY OF THE OKP VISUAL-FIELD SCREENING-TEST WITHTHE USE OF NEUTRAL DENSITY FILTERS

Oculokinetic perimetry (OKP) has been developed to screen for glaucoma tous field loss but has relatively poor sensitivity when compared with threshold perimetry. Forty-two eyes from 42 patients with glaucomatou s field loss on Humphrey threshold perimetry and 32 normals performed hand-held OKP under controlled conditions of refraction and lighting. Those who passed the standard test had their OKP cutoff determined wit h increasing neutral density filters (NDFs) at a new point 15 degrees from fixation in the inferotemporal held (where first glaucomatous def ects are rarest). OKP was then repeated with a NDF that increased the ambient light by 0.3 log units from cut off. Of the 16 glaucomatous ey es to pass standard OKP, 9 failed the NDF test, improving the sensitiv ity from 62% to 83% (p<0.05). These 9 eyes had field defects that were significantly less severe (mean defect 4.85 vs 7.91 (p<0.05) and corr ected pattern standard deviation 4.12 vs 7.00 (p<0.05) and were from y ounger patients (mean age 56 vs 66 years; p<0.05) than those who faile d standard OKP. None of the 32 normals failed standard OKP and only 1 of 32 failed the NDF test. The use of NDFs to customise OKP, producing essentially a staged suprathreshold contrast sensitivity test, appear s to increase the sensitivity of the OKP screener without degrading it s specificity, particularly in younger subjects.