| Diabetic macular edema is a leading cause of vision loss in patients withdiabetes mellitus. The incidence and prevalence of macular edema increase withlonger duration of diabetes and with increasing severity of concurrent retinopathy.Usually, the clinical diagnosis of macular edema is viewing the fundus using indirectophthalmoscope at the slitlamp through a pharmacologically dilated pupil. This is asubjective process that is dependent on many factors. Optical coherence tomography(OCT) is a new diagnostic technique in recent years that can provide cross-sectionalimages of macula in vivo and quantify macular thickness variation with a precision of10um. It appears to be more objective and reproducible which indicates that OCTmay be the best choice to investigate macular changes.Panretinal photocoagulation (PRP) is a standard and mostly common usedmethod for the treatment of severe nonproliferative diabetic retinopathy andproliferative diabetic retinopathy. Also PRP can delay the progression of diabeticretinopathy, but macular edema may be induced or increase, with either transient orsustained decrease of vision, that is the most common cause of visual loss in patientswith diabetic retinopathy after the treatment of PRP.Objectives1. To compare the two methods of OCT to indirect ophthalmoscope for the detectionof diabetic macular edema, search for case characteristics that predict disagreement,begin to build an evidence-based framework for clinical application of OCTmeasurement in diabetic retinopathy.2. To compare the changes of visual acuity and macular thickness before and after PRP, find the incidence and evolution of macular edema after PRP, and to prevent andreduce the incidence ofmacular edema induced by PRP.Methods1. We examined 45 patients with diabetes mellitus, 78 eyes. After pupil dilated, allpatients were under observation using pre-microscopy (78-diopter) and OCT tomeasure the macular thickness.2. 50 eyes of patients who were receiving panretinal photocoagulation, were under theobservation of eyesight, macular thickness by OCT before and 1, 3, 6 months aftertreatment.Results1. The indirect ophthalmoscopy was positively correlated with the results of OCT(r=0.575, P＜0.001). The overall agreement of indirect ophthalmoscopy and OCT onthe detection of diabetic macular edema was 68% (kappa=0.359, P＜0.01). Theoverall agreement excluding cases with mild edema by OCT was good (86%, kappa=0.660, P＜0.001), 47 cases of 55 were in line.2. There was no significant difference between the visual acuity before and after PRP.The macular thickness after 1 month, 3 months, 6 months of PRP had increased invarying degrees; among them, 1 month had the largest increase(25%), 3 months(21%)and 6 months(11%) edged down. We compared the macular thickness every two andfound: With the comparison of macular thickness before PRP, 1 month(P=0.000＜0.01) and 3 months (P=0.003＜0.01) after PRP, the macular thicknessincreased significantly; but 6 months (P=0.132＞0.05) after PRP, there was nosignificant differecne. The macular thickness was significantly positive correlatedwith the negative logarithm of visual acuity before and 1, 3, 6 months after PRP (thecorrelation coefficient r=0.5～0.8). Before PRP the correlation coefficient r=0.746 (P=0.000); after 1 month the correlation coefficient r=0.570(P=0.000); after 3 months the correlation coefficient r=0.518 (P=0.000); after 6 months the correlationcoefficient r=0.599 (P=0.000).Conclusions1. In nondiabetic macular edema, moderate diabetic macular edema, severe diabeticmacular edema detection, there was better relevance, but in mild diabetic macularedema (also known as sub-clinical macular edema, 201～300um-OCT measurement)detection, there was poor relevance.2. There was no significant difference of the visual acuity before and 1, 3, 6 monthsafter PRP. Visual whole, maintained stability. With the comparison of macularthickness before PRP, 1 month and 3 months after PRP, the macular thicknessincreased significantly; but 6 months after photocoagulation, the macular thicknessdecreased nearly to the levels before photocoagulation, there was no significantdifferecne between them. Macular thickness measured by OCT had significantlynegative correlation with eyesight. That's the thicker of the macular thickness, thetrend of low vision was increasingly.
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