Article type :

Original article

Author :

Jaideep Singh Bhalla

Volume :

3

Issue :

2

Abstract :

Background and Objectives: (a) To compare manual tangent screen perimetry and automated Humphrey perimetry for visual field testing, and (b) to analyze whether manual tangent screen perimetry still has a role or it should be replaced by computerized automatedHumphrey perimetry in physiology labsandclinicaldiagnostic settings. Methods: Study was done on 45 patients between 18 and 65 years of age that included 30 eyes of patients suffering from glaucoma/ other eye diseases giving rise to visual field defects, 5 eyes of patients suffering from neurological diseases and 10 eyes of normal subjects. All patients underwent perimetry examination by tangent screen at 1 meter distance (and 2 meter distance, if required) and automated Humphrey perimetry by Humphrey visual field analyzer (HFA) using 30-2 ‘white on white’ full threshold strategy. Tangent screen consists of black screen 2 metersquare or 1 metersquare. Accordingly, patient is seated at a distance of 2 meter or 1 meter respectively. A patient with organically constricted visual fields willshow an increase in the size of the visual field whenmoved to a farther distance while a patient with functional visual field loss will oftenreportthe same absolute size of the field (tubular or gun-barrel field) to be consistent with their first field. This is clear evidence of functional visual field impairment. Results: Out of 45 patients, 29 were male and 16 were female. The age cases in the study ranged from40-79 years withmean age of 60.70 years. Tangentscreenperimetry was able to detect about 5 patients with early field defects and 15 patients with moderate/ advanced field defects.On the other hand, Humphrey automated perimetry was able to detect 10 patients with early field defects and 18 patients with moderate/ advanced field defects. While only 13.33% technicians preferred tangent screen perimetry, around three-fourths of the technicians found Humphrey automated perimetry more preferable. 91.11% technicians found HVF to be technically easier because the automated perimeter eliminates observer bias, is easier to perform and also overcomesthe tedium of manual perimetry.Moreover, automated perimetry also uses quantified parameters whilemanual perimetry does not.On evaluating sensitivity and specificity of manual tangent screen perimeter using the Humphrey automated perimeter as the standard, the tests showed that the tangent screen perimeter had 75.75% sensitivity and 88.88% specificity. Since the mean time taken was more in automated perimetry: 474.5 sec, 474 sec and 459.9 sec versus 340.5 sec, 339.1 sec, and 339.1 sec in glaucoma, neurological and normal patients respectively; more patients66% preferred tangent screen perimetry. Interpretation and Conclusions: Our results suggest that visual field testing with automated perimetry is superior to visual field testing with tangent screen perimetry. The automated perimeter picked up visual field defectsin a larger number of eyesthan the tangentscreen perimeter. Visual field defects were more extensive on automated perimetry compared to tangent screen perimetry.