July 2013
Volume 54, Issue 7
Free
Letters to the Editor  |   July 2013
RNFL Damage After Treatment for Retinal Detachment
Author Notes
  • Department of Ophthalmology, University of Athens, Athens, Greece. 
  • E-mail: ancode@otenet.gr  
Investigative Ophthalmology & Visual Science July 2013, Vol.54, 5027. doi:10.1167/iovs.13-12426
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      Menelaos Kanakis, Ilias Georgalas, Chryssanthi Koutsandrea; RNFL Damage After Treatment for Retinal Detachment. Invest. Ophthalmol. Vis. Sci. 2013;54(7):5027. doi: 10.1167/iovs.13-12426.

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It was with great interest that we read the paper by Lee et al., 1 in which the authors concluded that in patients undergoing vitrectomy for rhegmatogenous retinal detachment, the retinal nerve fiber layer (RNFL) was significantly thinner in the area of the detached retina compared with the same area of the patients' fellow eye, 12 and 24 months postoperatively. 
Despite the prospective nature of the study, we regard as rather arbitrary the pairing of the clock hours of the detachment to those of the RNFL scan, given that RNFL trajectories are not at all linear. In fact, they are curved and there have been many attempts to describe them in terms of more or less complex mathematical equations. 2 Assuming linear trajectories—although never clearly stated in this paper—underlies the whole methodology, and inevitably leads to disproportionate overestimation (and in some occasions, underestimation or no estimation) of the RNFL scan portion referring to the detached area of the retina, as demonstrated below (Fig.). 
Figure
 
Reprinted from Jansonius NM, Schiefer J, Nevalainen J, Paetzold J, Schiefer U. A mathematical model for describing the retinal nerve fiber bundle trajectories in the human eye: average course, variability, and influence of refraction, optic disc size and optic disc position. Exp Eye Res. 2012;105:70–78. With permission for use and modification from Elsevier.
Figure
 
Reprinted from Jansonius NM, Schiefer J, Nevalainen J, Paetzold J, Schiefer U. A mathematical model for describing the retinal nerve fiber bundle trajectories in the human eye: average course, variability, and influence of refraction, optic disc size and optic disc position. Exp Eye Res. 2012;105:70–78. With permission for use and modification from Elsevier.
In the Figure, one can follow the lines from the center of the optic disc to the edges of the detached area (blue lines and blue area, respectively) and compare the supposedly affected—according to Lee et al.—RNFL arc (within the blue angle), to the really affected area (blue circles) as described by the RNFL trajectories (red curved lines). The RNFL scan line is represented by the green circle. 
Furthermore, the healthy eye of a subject is not guaranteed to be valid as reference for the RNFL thickness values, since there are studies that have demonstrated statistically significant differences between the two eyes of the same individual regarding RNFL thickness. 3,4 Asymmetry seemed to be greater in East Asian individuals than Caucasians. 4  
These remarks suggest that the results of the paper by Lee et al., according to our opinion, should be considered with caution, although we agree that retinal detachment is very likely to lead to loss of nervous tissue in the affected area and beyond this. 
References
Lee YH Lee JE Shin YI Lee KM Jo YJ Kim JY. Longitudinal changes in retinal nerve fiber layer thickness after vitrectomy for rhegmatogenous retinal detachment. Invest Ophthalmol Vis Sci . 2012; 53: 5471–5474. [CrossRef] [PubMed]
Jansonius NM Schiefer J Nevalainen J Paetzold J Schiefer U. A mathematical model for describing the retinal nerve fiber bundle trajectories in the human eye: average course, variability, and influence of refraction, optic disc size and optic disc position. Exp Eye Res . 2012; 105: 70–78. [CrossRef] [PubMed]
Budenz DL. Symmetry between the right and left eyes of the normal retinal nerve fiber layer measured with optical coherence tomography (an AOS thesis). Trans Am Ophthalmol Soc . 2008; 106: 252–275. [PubMed]
Dalgliesh JD Tariq YM Burlutsky G Mitchell P. Symmetry of retinal parameters measured by spectral-domain OCT in normal young adults [ published online ahead of print February 28, 2013]. J Glaucoma . doi:10.1097/IJG.0b013e318287ac2f .
Figure
 
Reprinted from Jansonius NM, Schiefer J, Nevalainen J, Paetzold J, Schiefer U. A mathematical model for describing the retinal nerve fiber bundle trajectories in the human eye: average course, variability, and influence of refraction, optic disc size and optic disc position. Exp Eye Res. 2012;105:70–78. With permission for use and modification from Elsevier.
Figure
 
Reprinted from Jansonius NM, Schiefer J, Nevalainen J, Paetzold J, Schiefer U. A mathematical model for describing the retinal nerve fiber bundle trajectories in the human eye: average course, variability, and influence of refraction, optic disc size and optic disc position. Exp Eye Res. 2012;105:70–78. With permission for use and modification from Elsevier.
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