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O.A. Lee, C.A. Rosende; The Level of Pan Retinal Photocoagulation Related to Subsequent Vitrectomy . Invest. Ophthalmol. Vis. Sci. 2005;46(13):376.
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Purpose: The Diabetic Retinopathy Study (DRS) and The Early Treatment Diabetic Retinopathy Study (ETDRS) established standards for managing patients with proliferative diabetic retinopathy (PDR) and severe nonproliferative diabetic retinopathy (SNPDR). The DRS specifically showed that laser panretinal photocoagulation (PRP) decreased by 50% the rate of severe vision loss (<5/200). In the clinic setting, patients often require additional PRP due to persistence of retinal neovascularization or the occurrence of vitreous hemorrhages. A trans pars plana vitrectomy (TPPV) is sometimes required to manage these cases. This study investigates whether the total surface area of retinal ablated in PDR and SNPDR patients who subsequently received vitrectomies was significantly less than those who did not need subsequent vitrectomy Methods: A retrospective chart review was performed on 259 patients (405 eyes) who received PRP for PDR or SNPDR between 01 January 2001 and 31 December 2001 at the Ophthalmology Clinic, Texas Diabetes Institute. Demographic data were collected. Incomplete records or vitrectomies for trauma were excluded. Procedure parameters were collected, and the surface area treated for PRP was determined by multiplying the number of laser shots by the individual burn area [radius of laser spot multiplied by magnification factor of Mainster lens (not always used) ––1.96–– then squaring that value and multiplying it by : 3.1416]. Results: Two–hundred fifty three eyes (180 patients) met inclusion criteria. Males were 48.9% of patients and females 53.3%. Mean age was 53.3 years, and 90.6% of the patients were Hispanic. Type 2 diabetics comprised 94.4%, and the mean duration of diabetes was 16 years, with a range of newly diagnosed to 33 years. Forty–five of the 253 eyes underwent TPPV after PRP; their PRP treatment area averaged 206+/–126mm2, with range of 24 to 505mm2. One–hundred ninety–nine eyes not undergoing subsequent TPPV had PRP treatment area that averaged 240+/–104mm2, with range of 14 to 577mm2. Conclusions: The DRS demonstrated the effectiveness of PRP in reducing the risk of severe visual loss in PDR and SNPDR. Though literature suggests that the extent of PRP is correlated with its effectiveness, our study does not support such a relationship, as there was no statistical difference between the two study groups. Certainly, there are many factors unique to each patient that may affect the result of PRP; nevertheless, we recommend a prospective study to determine the optimal PRP treatment area.
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