Graefes Arch Clin Exp Ophthalmol DOI 10.1007/s00417-015-3015-1
RETINAL DISORDERS
Spectral-domain optical coherence tomography reveals prelaminar membranes in optic nerve head pallor in eyes with retinitis pigmentosa Saba Al Rashaed 1 & Arif O. Khan 1 & Sawsan R. Nowilaty 1 & Deepak P. Edward 1 & Igor Kozak 1
Received: 18 December 2014 / Revised: 30 March 2015 / Accepted: 7 April 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract Purpose To determine the relationship between prelaminar structural changes of the optic nerve head (ONH) and optic nerve waxy pallor in retinitis pigmentosa (RP) using spectraldomain optical coherence tomography (SD-OCT) and fundus photography. Methods An observational cross-sectional case control study of patients with RP with and without ONH waxy pallor and controls. Subjects underwent clinical examination, fundus photography, and SD-OCT raster imaging of the ONH. Four independent specialists reviewed the images in a masked fashion. Results Fifty-five eyes of 31 subjects with RP and 28 eyes of 14 controls were included. Optic nerve head waxy pallor was seen in 29 RP eyes (52.7 %) and none in controls. SD-OCT showed a hyper-reflective structure suggestive of a glial membrane-like structure on the surface of ONH in 16 of RP eyes (55.1 %). In the RP group, there was a significant positive correlation between the ONH pallor and the presence of a prelaminar structure (p=0.006). Conclusions There is a presence of glial membrane-like structures on the optic nerve head surface in eyes with RP compared to healthy eyes. As the presence of glial membranes correlated with the presence of ONH waxy pallor, in such cases these membranes might be responsible for ONH waxy pallor.
* Igor Kozak
[email protected] 1
King Khaled Eye Specialist Hospital, P.O. Box 7191, Riyadh 11462, Kingdom of Saudi Arabia
Keywords Retinitis pigmentosa . Spectral-domain optical coherence tomography . Optic nerve head waxy pallor
Introduction Retinitis pigmentosa (RP) refers to a group of inherited retinal diseases with phenotypic and genetic heterogeneity that primarily affects the rod and cone photoreceptors and the retinal pigment epithelial cells. The classic fundus appearance of RP includes retinal pigment epithelial cell (RPE) changes resulting in retinal hypo- or hyperpigmentation, retinal granularity, and bone spicule-like pigment formation. The retinal vessels are often attenuated. The optic disc may be normal in early RP, show a waxy fullness with hyperemia, or appear waxy and pale [1, 2]. A Bgolden ring^ or yellowish-white halo can often be seen surrounding the optic disc in early RP. As the disease progresses, this golden ring is replaced with peripapillary mottling, hyperpigmentation, and atrophy of the RPE. In advanced disease, the optic nerve head can show marked pallor [3, 4]. While some of the clinical findings in RP such as pigmentary retinopathy or bone spicule formation can be partially explained by histopathologic findings in numerous studies, there is little information on why the optic nerve in some RP eyes acquires a waxy pallor appearance. It has been hypothesized that the optical effect of an epiretinal membrane formation, sometimes seen in eyes with RP, may give the optic nerve head (ONH) a waxy pallor appearance. Indeed, a preretinal membrane covering ONH has been described in two post-mortem eyes with RP [5, 6]. In those eyes, the membrane was continuous with Elschnig’s membrane, that originated from fibrous astroglial cells in the optic nerve and formed a continuous cellular layer over the ONH and the retina. Other human histopathological reports
Graefes Arch Clin Exp Ophthalmol
have described preretinal membranes in retinal dystrophies [7]. Spectral-domain optical coherence tomography (SD-OCT) has become an important diagnostic tool in numerous diseases of the posterior segment of the eye. In an OCT imaging study of eyes with RP in which the ONH parameters were characterized, 33 % of eyes exhibited optic disc pallor. However, the latter did not affect the ONH parameters [8]. The absence of a decreased rim area in eyes with optic disc pallor compared to eyes without optic disc pallor suggested that other factors such as glial tissue transformation may play a role in the development of ONH pallor. The above-mentioned study using OCT technology by Hwang et al. has characterized ONH parameters in RP, but did not examine the superficial structural changes that might occur on the optic nerve head [8]. Currently, there is no report available in ophthalmic literature (automated search on PubMed) confirming or refuting the in vivo presence of prelaminar glial membranes or other structure(s) overlying the ONH in eyes with RP. The purpose of this study was to fill this gap by describing the superficial morphology of the ONH and correlating it with the presence or absence of ONH waxy pallor in RP eyes.
Methods Subjects This was an observational, cross-sectional case control study performed at the King Khaled Eye Specialist Hospital in Riyadh, Saudi Arabia after receiving approval from the hospital ethics committee/institutional review board. All subjects provided informed consent prior to enrollment, and all procedures conformed to the Declaration of Helsinki. Patients with RP were diagnosed based on careful history, the presence of night blindness, characteristic fundus appearance, concentric ring-shaped visual field defect, and decreased or non-recordable electroretinogram. Family history was obtained with pedigree drawings. Early RP was defined by absence or presence of mild nyctalopia, presence of bone spicules on retinal examination only in the retinal periphery or in one retinal quadrant, no visual field defect or decreased sensitivity or scotoma in
