Dr.Subhrakali Paramguru, S21577, Dr.Nirupama Rout, Dr.Sabita
Mohanta, Dr.Sumita Mohapatra
INTRODUCTION
The role of vitreous inflammation in intraocular pathologies is now clearly defined by advanced methods of examinations and surgery.Inflammmatory disesases of various etiologies can produce vitreous inflammation by vitreo-retinal adhesions and vitreous detachment.One of the greatest challenges in caring for patients with sight-threatening vitreous inflammations is the lack of objective marker of primary disease activity.The current gold standard for assessing vitreous inflammation is the National Eye Institute(NEI) system for grading vitreous haze,often reffered to as Nussenblatt scale.But this technique has a number of limitations as it is 1-subjective 2-non-continuous 3-poor discriminatory at lower levels of vitreous haze 4-poor sensitivity.In recent era,a new objective imaging modality,OPTICAL COHERENCE TOMOGRAPHY(OCT) provides high resolution,cross-sectional images of ocular tissues in a non-invasive manner,pioneering to provide automated measurements of disease morphology and vitreous inflammation
AIM-
In this study,we obtain measurement of vitreous signal intensity from OCT images obtained in cohorts of patients with vitreos inflammation secondary to uveitis.We co-relate these findings with standard assesments of vitreous haze in an objective to develop an improved marker of inflammatory activity in patients with this disease
INCLUSION CRITERIA-
For this study,OCT image sets from 2 separate groups,attending outdoor patient basis in SCB Medical College,cuttack were retrospectively collected.In this 1st group(40 patients) images from eyes with viteous haze were included.These images were then compared to those of a 2nd group(40) patients without vitreous haze but with or without intraocular disease.Clinical data collection about age,gender,diagnosis of uveitis including keratic precipitates,posterior synechiae,cataract,posterior capsular opacification(in pseudophakic eye),BCVA,anterior chamber cells and flare was done and classified according to NEI system.
QUANTITATIVE ANALYSIS OF VITREOUS INFLAMMATION USING OCT-
Raw OCT datas were validated using custom grading software,which enables easy navigation of spectral domain OCT volume scans and manual boundary annotation of each B scan of a subset.Based on these boundaries the intensities of all pixels in vitreous compartment was summerised and mean OCT Intensity values were generated.In each case,3-5 B scans passing through the foveal central subfield were analysed.This typically required 5-10 minutes of grading time per image set.These boundaries consisted of 1)Vitreous top 2)Retinal Pigment Epithelium(RPE) 3)RPE-Outer,the outer boundary of RPE.After completion of grading,mean intensity values were calculated for the vitreous space(termed as VIT-Absolute Intensity) and the RPE space (termed RPE-Absolute Intensity).Intensity values for vitreous and RPE spaces were then expressed as a ratio (termed as VIT/RPE-Relative Intensity).The resulting measurements were correlated with those obtained from the foveal central subfield (n=40 for all eye in subset,r=0.9318.p<0.001 and n=40 for those eyes in subset with vitreous with or without uveitis r=0.9112 p<0.001).For comparision of each OCT Intensity values between groups,non-parametric Kruskal-Wallis testing was used.For co-relation of vitreous haze scores with mean OCT Intensity values,non-parametric Spearman testing was used.Agreement between graders was also axamined using Bland-Altman analysis.p values<0.05 were considered statistically significant
RESULT-
A significant difference in VIT/RPE-Relative Intensity was found between those eyes with ” no vitreos haze” or “normal eyes” (median= 0.076,IQR =0.047) when compared to those with “vitreous haze” (median =0.160,IQR=0.145)(p=0.0001) and between each grade of vitreos haze.A significant co-relation was found between VIT/RPE-Relative Intensity and clinical vitreous haze scores,visual acquity and clinical anterior chamber cells and flare.When evaluated in a step-wise multivariable model examining factors governing media clarity,visual acquity,disease etiology,location of inflammation,VIT/RPE-Relative Intensity remained independently associated with clinical vitreous haze scores.
REFERENCES-
1.Article by Pearse A. KEANE.MD FRCOphth.Michael Karampelas and Alastair K. Denniston
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