6 Diagnostic Capability of Optical Coherence Tomography …
143
reduced thickness of the GCL+IPL in the pericentral region of the macula [20].
While Vujosevic et al. [97] and van Dijk et al. [21, 22] only found early alterations
in the inner retina in diabetics without DR or with initial DR; Cabrera DeBuc et al.
study suggested that the outer segment of the photoreceptor layer may be vulnerable
in both type 1 diabetic individuals both with and without early DR [96]. The results
by Cabrera DeBuc et al. might also indicate that an early sign of vascular alteration
development could be detected by investigating the changes in optical properties
and thickness of the OPL. However, further investigation is required to find whether
outer retinal changes might be associated with long-term inner retinal pathology
[96]. Akshikar et al. [98] has also reported significant thinning of the outer retinal
segment in the ETDRS (Early Treatment Diabetic Retinopathy Study) regions when
investigating macular thickness differences in age-matched subjects using Spectralis
SD-OCT. Inconsistent results are present across different studies and indicate that
caution should be taken when preparing future studies involving diabetic subjects
and OCT imaging [21, 90, 91, 99–103].
Doppler OCT imaging has also demonstrated its clinical utility in detecting blood
flow change in patients with DR as well as evaluating the three-dimensional architecture of neovascular complexes in proliferative DR (PDR) [104]. OCTA, one of the
latest ophthalmic imaging developments, can be used to both quantitatively analyze
blood flow and provide high-contrast images of the retinal vascular bed immediately and without the need for dye injection [106–109]. Recent studies have shown
the potentialities of this modality to assess capillary dropout and confirm neovascularization in other retinal diseases [110–112]. Although not too many studies have
been reported to date, OCTA applications in diabetes eye complications may provide an alternative to more accurate diagnosis and management of DR and DME by
quantitatively assessing capillary dropout and retinal neovascularization [113].
Further developments of OCT technology may impact DR diagnosis and improve
the management of this major clinical and public health problem. However, a lowcost approach solution must be reached to successfully introduce its application in
population-based screening programs.
6.3.2 Multiple Sclerosis
Multiple sclerosis (MS) is a chronic inflammatory disorder that affects the central
nervous system. The disease is characterized by demyelination that leads to axonal
dysfunction and neuronal loss [114]. Unmyelinated neuronal axons offer a good
possibility to examine axonal loss as the thickness of the myelin sheath does not
affect the nerve thickness results. The innermost layer of the retina is the RNFL
being comprised of the axons of the retinal ganglion cells which get myelin sheath
only after leaving the eye through the lamina cribrosa. Therefore, the thickness
measurement of the RNFL might be a good marker of the axonal damage in MS
patients.
143
reduced thickness of the GCL+IPL in the pericentral region of the macula [20].
While Vujosevic et al. [97] and van Dijk et al. [21, 22] only found early alterations
in the inner retina in diabetics without DR or with initial DR; Cabrera DeBuc et al.
study suggested that the outer segment of the photoreceptor layer may be vulnerable
in both type 1 diabetic individuals both with and without early DR [96]. The results
by Cabrera DeBuc et al. might also indicate that an early sign of vascular alteration
development could be detected by investigating the changes in optical properties
and thickness of the OPL. However, further investigation is required to find whether
outer retinal changes might be associated with long-term inner retinal pathology
[96]. Akshikar et al. [98] has also reported significant thinning of the outer retinal
segment in the ETDRS (Early Treatment Diabetic Retinopathy Study) regions when
investigating macular thickness differences in age-matched subjects using Spectralis
SD-OCT. Inconsistent results are present across different studies and indicate that
caution should be taken when preparing future studies involving diabetic subjects
and OCT imaging [21, 90, 91, 99–103].
Doppler OCT imaging has also demonstrated its clinical utility in detecting blood
flow change in patients with DR as well as evaluating the three-dimensional architecture of neovascular complexes in proliferative DR (PDR) [104]. OCTA, one of the
latest ophthalmic imaging developments, can be used to both quantitatively analyze
blood flow and provide high-contrast images of the retinal vascular bed immediately and without the need for dye injection [106–109]. Recent studies have shown
the potentialities of this modality to assess capillary dropout and confirm neovascularization in other retinal diseases [110–112]. Although not too many studies have
been reported to date, OCTA applications in diabetes eye complications may provide an alternative to more accurate diagnosis and management of DR and DME by
quantitatively assessing capillary dropout and retinal neovascularization [113].
Further developments of OCT technology may impact DR diagnosis and improve
the management of this major clinical and public health problem. However, a lowcost approach solution must be reached to successfully introduce its application in
population-based screening programs.
6.3.2 Multiple Sclerosis
Multiple sclerosis (MS) is a chronic inflammatory disorder that affects the central
nervous system. The disease is characterized by demyelination that leads to axonal
dysfunction and neuronal loss [114]. Unmyelinated neuronal axons offer a good
possibility to examine axonal loss as the thickness of the myelin sheath does not
affect the nerve thickness results. The innermost layer of the retina is the RNFL
being comprised of the axons of the retinal ganglion cells which get myelin sheath
only after leaving the eye through the lamina cribrosa. Therefore, the thickness
measurement of the RNFL might be a good marker of the axonal damage in MS
patients.