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Joseph E. Zeiter, Mark Juzych, Victoria Landolt, Aman Shukairy; Evaluating Differences In Subjective Cup-to-disc Ratio Measurement Between Ophthalmic Sub Specialties Using Stereoscopic Optic Nerve Head Photos. Invest. Ophthalmol. Vis. Sci. 2012;53(14):646.
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To examine the level of agreement between subjective and objective methods in estimating horizontal and vertical cup-to-disc ratios (HCDR and VCDR, respectively) and to determine if there are differences in percieved CDR between different ophthalmic sub specialties.
Ten glaucoma patients and ten control subjects underwent full ophthalmic examination, stereoscopic optic nerve head photographs (ONHPs), and rNFL analysis using optical coherence tomography (Stratus OCT). The intraclass correlation coefficient (ICC) and Bland Altman plots were used to assess the agreement across the two methods. Analysis of variance (ANOVA), Tukey adjustment, and pairwise P values were used to compare the HCDR and VCDR estimates between 45 clinicians who were assigned to one of 5 groups: residents, glaucoma faculty, retina faculty, comprehensive faculty and occuloplastic faculty. A 5 line raster scan through the nerve was used as the gold standard for accurately assessing the ratio which was compared to that of the physicians who reviewed photos.
Between the five groups of clinicians, the agreement in subjectively assessed HCDR and VCDR was substantial (ICC=0.82 and 0.87, respectively), and for both methods, overall agreement was good (ICC=0.69 and 0.75 for the HCDR and VCDR, respectively). Glaucoma faculty showed a highest correlation to the stratus OCT +/-SD HCDR (0.71+/-0.16) and VCDR (0.68+/-0.13). The lowest overall correlation coefficient was seen in the HCDR by oculoplastic faculty (0.51+/-0.21). For all five groups, repeated measures ANOVA test demonstrated significant differences between subjective CDR and OCT measurements for glaucomatous (P=0.0011 and 0.0013, HCDR and VCDR, respectively) and normal (P=0.0001 for both HCDR and VCDR) eyes. Tukey adjustment demonstrated specific statistical differences between the two methods.
Overall, glaucoma faculty had the highest correlation in subjective assessment of the ONH to the Stratus OCT. This study showed a wide variation in perceived CDR between subspecialties, which may be important when deciding whether or not further glaucoma testing is warranted.
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