Dark Adaptation? a Pitfall in Evaluation of Reliability of Visual Fields of Second Eye in Glaucoma Patients

Abstract

Purpose: To analyze that dark adaptation may be a pitfall in evaluation of reliability of visual fields of second eye of glaucoma patients.

Materials & Methods: The study was conducted in the Department of Ophthalmology, Abbasi Shaheed Hospital from January 2007-June 2008. In this study evaluation of patients were randomly selected from the glaucoma clinic who went for routine perimetery for the first time. Patients were examined in detail, diagnosis was established and were sent for field examination to assess the extent of damage by glaucoma .Perimetery was done on Octopus 300 series perimeter after setting all the parameters and under constant supervision.

Results: A total of 117 patients were examined from January 2007- June 2008. A male preponderance was seen and majority of the patients belonged to 60-70 years age group making up to 37.4 %followed by 40-50 years age group i.e 25.6%. Maximum number of patients have percentage of false positives and false negatives between the range of 0-5 % which shows that a large number of patients(62% patients in false positives and 79% patients in false negatives in their right eyes and 68.4% patients in false positives and 74.6% patients in false negatives in their left eyes) had a reliable field, 96(82%) patients had reliability factor in acceptable normal range their right eyes and 104(89%) patients had reliability factor in acceptable normal range in left eyes. It shows that majority of patients had a reliable field test. It is obvious that fields of left eyes were more reliable as compared to right eyes.

Conclusion: It was concluded that the results of second eye of the patients were more reliable as compared to the reliability of the results of first eye. This could be due to the phenomenon of dark adaptation .The second eye gets dark adapted behind the occluder as the patient proceeds the test for first eye, and thus produces better results when examined. So dark adaptation may be a pitfall in interpretation of reliability of visual fields of second eye.