The Reliability of Cone Density Measurements in the Presence of Rods.

Alfredo Dubra // Publications // Jun 01 2018

PubMed ID: 29946495

Author(s): Morgan JIW, Vergilio GK, Hsu J, Dubra A, Cooper RF. The reliability of cone density measurements in the presence of rods. Transl Vis Sci Technol. 2018 Jun 22;7(3):21. doi: 10.1167/tvst.7.3.21. eCollection 2018 Jun. PMID 29946495

Journal: Translational Vision Science & Technology, Volume 7, Issue 3, Jun 2018

PURPOSE Recent advances in adaptive optics scanning light ophthalmoscopy (AOSLO) have enabled visualization of cone inner segments through nonconfocal split-detection, in addition to rod and cone outer segments revealed by confocal reflectance. Here, we examined the interobserver reliability of cone density measurements in both AOSLO imaging modalities.

METHODS Five normal subjects (nine eyes) were imaged along the horizontal and vertical meridians using a custom AOSLO with confocal and nonconfocal split-detection modalities. The resulting images were montaged using a previously described semiautomatic algorithm. Regions of interest (ROIs) were selected from the confocal montage at 190 μm, and from split-detection and confocal montages at 900 and 1800 μm from the fovea. Four observers (three experts, one naïve) manually identified cone locations in each ROI, and these locations were used to calculate bound densities. Intraclass correlation coefficients and Dice’s coefficients were calculated to assess interobserver agreement.

RESULTS Interobserver agreement was high in cone-only images (confocal 190 μm: 0.85; split-detection 900 μm: 0.91; split-detection 1800 μm: 0.89), moderate in confocal images at 900 μm (0.68), and poor in confocal images at 1800 μm (0.24). Excluding the naïve observer data substantially increased agreement within confocal images (190 μm: 0.99; 900 μm: 0.80; 1800 μm: 0.68).

CONCLUSIONS Interobserver measurements of cone density are more reliable in rod-free retinal images. Moreover, when using manual cell identification, it is essential that observers are trained, particularly for confocal AOSLO images.

TRANSLATIONAL RELEVANCE This study underscores the need for additional reliability studies in eyes containing pathology where identifying cones can be substantially more difficult.