Background/aims To study the efficacy of pattern deviation (PD) values in the estimation of visual field compensating the influence of cataract in eyes with glaucoma.

Methods The study subjects comprised of 48 eyes of 37 glaucoma patients. Mean total deviation value (mTDs) on Humphrey Field Analyzer after cataract surgery was compared with mean PD (mPD) before the surgery. Visual field measurements were carried out ≤6 months before (VF_pre) and following (VF_post) successful cataract surgery. The difference between the mPD or mTD values in the VF_pre and mTD values in the VF_post (denoted as εmPD/ΔmTD) was calculated, and the influence of the extent of ‘true’ glaucomatous visual field damage or cataract (as represented by εmPD and ΔmTD, respectively) on this difference was also investigated.

Results There was a significant difference between mTD in the VF_pre and mTD in the VF_post (p<0.001, repeated measures analysis of variance). There was not a significant difference between mPD in the VF_pre and mTD in the VF_post (p=0.06); however, εmPD was significantly correlated with the mTD in VF_post and also ΔmTD (R²=0.56 and 0.27, p<0.001, Pearson's correlation). The accurate prediction of the mTD in the VF_post can be achieved using the pattern standard deviation (PSD), mTD and also visual acuity before surgery.

Conclusions Clinicians should be very careful when reviewing the VF of a patient with glaucoma and cataract since PD values may underestimate glaucomatous VF damage in patients with advanced disease and also overestimate glaucomatous VF damage in patients with early to moderate cataract.