INFLUENCE OF LASER PHOTOCOAGULATION FOR CLINICALLY SIGNIFICANT DIABETIC MACULAR EDEMA (DMO) ON SHORT-WAVELENGTH AND CONVENTIONAL AUTOMATED PERIMETRY

The aim of the study was to determine the effect of laser photocoagula tion for clinically significant diabetic macular oedema (DMO) on macul ar visual function as assessed by conventional and short-wavelength au tomated static threshold perimetry. The sample comprised 24 patients w ho required laser photocoagulation for clinically significant DMO (mea n age 59.75 years, range 45-75 years). One eye of each patient was sel ected for the study. Patients underwent conventional and short-wavelen gth perimetry using programme 10-2 of the Humphrey Field Analyser on t wo separate occasions prior to treatment and subsequently within 1 wee k of, and at 1, 2, 4 and 12 weeks after, treatment. The pointwise patt ern deviation plot was analysed for conventional perimetry and a point wise horizontal and vertical hemifield asymmetry analysis was derived for short-wavelength perimetry (thereby negating the influence of pre- receptoral absorption). The extent of sensitivity loss was determined by counting the number of stimulus locations with statistical probabil ity levels of p less than 0.05. Group mean log minimum angle of resolu tion (logMAR) visual acuity was largely unchanged over the course of t he study. Conventional perimetry showed an increase in the group mean number of abnormal contiguous stimulus locations from 2.4 (SD 4.3, ran ge 0-14) immediately prior to treatment, to 12.4 (SD 7.8, range 0-30) within 1 week of treatment; at 3 months post-treatment, the group mean number of abnormal contiguous stimulus locations was 8.1 (SD 6.5, ran ge 0-20). A similar but less pronounced change was found for short-wav elength perimetry. The spatial position of the posttreatment localised sensitivity loss corresponded with the area of retinal photocoagulati on. Despite proven benefit in the stabilisation of visual acuity, lase r photocoagulation for clinically significant DMO invariably results i n a localised loss of perimetric sensitivity within 10 degrees eccentr icity of the fovea. Evidence for the value of laser therapy for clinic ally significant DMO must be re-examined.