An Observational study to Analyse the Role of Visual Evoked Potential in Visual Prognosis Before and After Panretinal Photocoagulation for Diabetic Retinopathy in Type 2 Diabetic Mellitus

Dheebalakshmi, J (2019) An Observational study to Analyse the Role of Visual Evoked Potential in Visual Prognosis Before and After Panretinal Photocoagulation for Diabetic Retinopathy in Type 2 Diabetic Mellitus. Masters thesis, Madurai Medical College, Madurai.


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Visual evoked potential is a measurement of electrical signal of occipital cortex in response to light stimulus. Abnormalities in VEP denote a nonselective functional neuronal loss .it reveals integrity of afferent visual pathway or any damage along the visual pathway. Therefore, VEP should be considered as a valid method for detecting neuronal damage (ganglion cell and nerve fibre layers of the retina) in diabetic retinopathy. Diabetic mellitus can leads to visual impairment by both diabetic retinopathy and neurodegeration. In an compromised retina in DR, laser axotomy also leads to wallarian degeneration of retinal ganglion cells. Though Pan retinal photocoagulation is considered to be a mainstay of treatment for PDR, its complication can also even worsen the vision such as macular edema, peripheral visual field loss, consecutive optic atrophy, choroidal effusion. In our study, we try to analyse and establish the role of VEP in assessing preexisting retinal nerve damage due to diabetic retinopathy. Thus, VEP helps in predicting the retinal nerve status in patients with diabetes who is going for laser treatment. Early detection of complication and visual prognosis by VEP can change the mode of treatment includes Intra vitreal anti-VEGFor adjust the parameter of laser burns like PASCAL, MIP. In our study, we had taken one hundred eyes of fifty patients with diabetic retinopthy who is fit for pan retinal photocoagualation according to EDTRS classification. In this study, age of the patients distribution ranges around 50-55 years of age.Mean Pre PRP VEP amplitude is significantly decreases with severity of diabetic retinopathy (P < 0.001). It shows strong correlation with severity of DR and abnormal VEP which may attributed for extensive retinal nerve damage in grade 3 diabetic retinopathy. Mean pre PRP VEP amplitude is 7.6μV and post PRP VEP amplitude is 5.3μV.A statistically significant number of patients shows reduced VEP after PRP. In this study, macular edema is more frequently seen (44%) followed by nil complication (36%), choroidal effusion (4%),COA(5%), other(11%). Complications followed by laser is equally distributed among 3 grades of DR. When Pre PRP VEP amplitude is ≤ 6μV, there is significant reduction in post PRP VA and complications.As diabetic retinopathy and neuropathy leads to functional detoriation by significant thinning of the ganglion cell and nerve fibre layer, complicatios of PRP is increase in already compromised retina. CONCLUSION: From this study, we conclude that VEP can play a major role in assessing functional neuronal loss in DR. In severe NPDR, very severe NPDR and early PDR, consider full scatter Pan Retinal photocoagulation as an optional after doing VEP. When VEP amplitude is ≤ 6μV, we can modify the LAER parameter like spot size, energy, distance between spots or other newer modalities like selective retinal therapy (SRT) transpupillary thermotherapy (TTT), subvisible diode micropulse (SDM) photocoagulation and other treatment like intra vitreal anti-VEGF.

Item Type: Thesis (Masters)
Additional Information: Reg.No.221613102
Uncontrolled Keywords: Diabetic retinopathy, Pan retinal photocoagulation, visual evoked potential.
Subjects: MEDICAL > Ophthalmology
Depositing User: Subramani R
Date Deposited: 01 Sep 2019 03:48
Last Modified: 01 Sep 2019 03:48

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