Comparison between time-domain and spectral-domain OCT in the detection of retinal nerve fiber layer defects in glaucoma patients

AIM: To compare, using the instruments’ built-in normative databases, the sensitivities of time-domain optical coherence tomography (Stratus OCT) and spectral-domain OCT (Spectralis OCT) in the detection of retinal nerve fiber layer (RNFL) defects in patients with glaucoma. METHODS: Fifty-two eyes of 35 patients with open angle glaucoma were included. A total of 69 hemiretinas with photographically identified RFNL defects were analyzed using the fast RNFL scan of Stratus OCT and the circle scan in Spectralis OCT. The OCT parameters were evaluated at 5% and 1% abnormality levels using the instruments’ built-in normative databases. The diagnostic sensitivity of each parameter was compared between the two devices. RESULTS: The Spectralis OCT detected RNFL defects within each quadrant more frequently than the Stratus OCT at both the 5% (79.7% vs 63.8%, P=0.01) and 1% (56.5% vs 40.6%, P=0.01) abnormality levels. At the 1% abnormality level, the sensitivity was significantly higher in the standard sector of Spectralis OCT than in the clock-hour sector of the Stratus OCT (68.1% vs 39.1%, P<0.01).

Нормотензивная глаукома или аденома гипофиза?

Цель: дифференциальная диагностика патологии зрения при макроаденоме гипофиза и нормотензивной глаукоме. Материал и методы: Под наблюдением находилась пациентка И., 59 лет с жалобами на снижение остроты зрения и выпадение поля зрения на левом глазу. В дополнение к стандартному офтальмологическому обследованию были произведены: оптическая когерентная томография (Stratus OCT 3000), экстракраниальная и транскраниальная ультразвуковая допплерография и магнитно–резонансная томография (МРТ) головного мозга. Результаты: Была обнаружена частичная атрофия зрительного нерва левого глаза, которая явилась следствием гормонально неактивной макроаденомы гипофиза размерами 3-29-26 мм с эндо-, супра- и параселлярным (левосторонним) ростом. Представленный клинический случай позволил расставить некоторые акценты в дифференциальной диагностике аденомы гипофиза и нормотензивной глаукомы. Выводы: На примере данного клинического случая хотелось бы подчеркнуть важность своевременного и сочетанного ведения специалистами узкого профиля (офтальмологами, невропатологами, эндокринологами и нейрохирургами) пациентов такого рода для ранней и точной диагностики, что может предотвратить высокий процент инвалидизации.

comparative evaluation of time domain and spectral domain optical coherence tomography in retinal nerve fiber layer thickness measurements

Introduction: Before any new device can replace another for use in clinical practice, it is imperative that its reproducibility, diagnostic accuracy, and ability to detect changes over time are tested.Objective: To evaluate retinal nerve fiber layer (RNFL) measurements between two optical coherence tomography (OCT) systems: the Stratus OCT, a time domain system, and the Cirrus HD-OCT, a spectral domain system (both by Carl Zeiss Meditec, Inc., Dublin, CA). Materials and methods: An observational cross-sectional study was carried out involving 20 eyes with primary open angle glaucoma and 32 eyes of healthy controls. One eye of each patient was imaged on the same day with each instrument. The RNFL thicknesses measured by the two instruments were compared.Main outcome measures: Each clock hour, quadrant, and average RNFL thickness was determined on each of the two instruments.Statistics: The reliability was assessed by the intra-class correlation coefficient (ICC) and the Bland Altman plot for the limits of agreement for the overall mean RNFL thickness and for each quadrant. Results: A randomly selected eye of each of the 52 participants was analyzed. The mean temporal, superior, nasal and inferior RNFL thickness (in microns) were found to be 65.42 ±18.98, 114.85±26.67, 75.83±28.61 and 116.35±29.43 when measured by the Stratus OCT. In glaucoma patients these values were 55.06±18.22, 97.86±29.37, 63.44±24.89, and 102.94±38.20; and in controls these values were 70.59±17.40, 123.61±20.65, 82.03±28.67 and 123.06±21.63 respectively. The mean temporal, superior, nasal and inferior RNFL thickness (in microns) were 62.00±13.08, 112.00±25.13, 68.56±16.66 and 114.23±25.82 respectively, when measured with the Cirrus OCT. In glaucoma patients these values were 57.88±12.99, 98.56±26.88, 64.63±12.52 and 105.50±29.49; while in the control group these were 64.06±12.82, 118.72±21.63, 70.53±18.33, and 118.59±23.05 respectively. Intraclass correlation coefficient alpha (ICC alpha) for the temporal, superior, nasal and inferior quadrant RNFL thickness measurements were 0.81, 0.85, 0.66 and 0.93 respectively. Bland-Altman plots showed the limits of agreement (95%CI) for average RNFL to be 4.59 ±20.10 in the control group. In patients of glaucoma, Bland-Altman plots showed the limits of agreement (95%CI) for average RNFL to be 1.56±21.50. Conclusions: There is considerable variability in the RNFL thickness measurements made by the Cirrus and Stratus OCT that exceeds the limits of resolution afforded by the instruments. RNFL measurements obtained from the two OCT systems may not be used interchangeably.DOI: http://dx.doi.org/10.3126/nepjoph.v6i2.11692Nepal J Ophthalmol 2014; 6(12): 185-191