3/1/2023 0 Comments 768 civilization v![]() ![]() With respect to specific circumpapillary locations, previous works analyzed up to 12 RNFLT sectors. 1, 13 – 16 Consistently, these works reported significantly greater RNFLT values for right eyes. 12 Interocular RNFLT differences were studied on multiple occasions by time-domain and spectral-domain OCT over the past one and one-half decades. Although eyes are paired organs, numerous anatomic asymmetries have been described, even in ophthalmically healthy patients. To determine this, as well as to address the other points population statistics of interocular RNFLT differences along the entire measurement circle are needed. Although each eye individually deviates anatomically from the norm and is therefore flagged by the OCT software, the RNFLT difference between the eyes may still be within normal limits. In particular, in both eyes of this individual, the superotemporal RNFLT maxima are shifted in a temporal direction compared with the machine norms. However, the RNFLT profiles of the two eyes look similar. On the RNFLT measurements of either eye of this patient, the same sectors are marked as abnormally thin by the machine. ![]() S1 for fundus photographs of this patient). ![]() Interocular asymmetry may even help to interpret questionable RNFLT abnormality marks owing to individual eye anatomy deviating from the norm, as illustrated by an example in Figure 1 (see Supplementary Fig. 11 For instance, we have previously shown that the subtype of pseudoexfoliation glaucoma presents asymmetrically for most cases in clinic at the time of its diagnosis. For instance, it has been shown that interocular RNFL asymmetry is a useful clinical and quantitative OCT measurement to assess early glaucomatous damage, 10 and can be even helpful in differentiating subtypes of glaucoma. Because the onset of pathologic RNFL thinning is highly location specific, an interocular comparison of RNFLT may reveal further diagnostically relevant information in addition to the common practice of comparing either eye in isolation to population based norms. 9 Apart from that, it is commonly assumed that the RNFL geometries between the right and the left eye of healthy individuals are highly correlated. RNFLT is known to be associated with age and ocular magnification, 7 race, 8 and sex. Therefore, owing to individual ocular anatomic variability, the onset of RNFL thinning may not fall outside normative limits if a patient's individual RNFLT geometry differs from normative expectations within each single eye. Thinning of the RNFL may occur at small areas on the measurement circle, which may be missed by summary measures such as coarse circle sectors. 4 OCT devices provide printouts of RNFLT along the entire measurement circle together with percentiles of population norms. Typical clinical RNFLT measurement protocols implemented in OCT devices measure thicknesses on a single circle with a diameter of about 3.5 mm around the optic nerve head (ONH). 2, 3 Common clinical ophthalmic OCT devices compare RNFLT with an age-matched normative database incorporated into the software for diagnostic purposes. Optical coherence tomography (OCT) is an established high-resolution imaging technology that objectively measures RNFLT. 1 The ability to detect changes in RNFL early in the course of glaucoma will lead to early diagnosis and treatment of the disease, which can improve the prognosis. Glaucoma is characterized by apoptosis of retinal ganglion cells and their axons, which leads to an increase in the size of the optic nerve cup, and consequent vision loss. Retinal nerve fiber layer thickness (RNFLT) is an important adjunct to diagnosing optic neuropathies like glaucoma.
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