ImageWise 16 – Glaucoma

The Ganglion cells and the RNFL in POAG with Diabetes  

Dr Shreya Jaiswal, Dr Prabhat Nangia, Dr Sarang Lambat, Dr Vinay Nangia 
Suraj Eye Institute, 559 New Colony, Nagpur 

Case Description
A male, 45 years of age, came with complaints of diminution of vision in both eyes (OU) since 1 and half years.  He was a known case of  diabetes mellitus since 30 years, systemic hypertension since 10 years and primary open angle glaucoma in both eyes since  5 years. He was on topical alpha agonist and carbonic anhydrase inhibitor combination eye drop in both eyes. His best corrected visual acuity was 6/6, N6 in right eye and 6/12, N10 in left eye. Anterior segment examination was within normal limits. Intraocular pressure recorded by Goldmann applanation tonometer was 26 mmHg in both eyes. His central corneal thickness was 623 microns in right eye (OD) and 628 microns in left eye (OS).

Figure 1 Shows fundus photograph of right eye centered at the disc. Optic disc shows presence a vertical cup to disc ratio (VCDR) of 0.75:1. The superior RNFL is noted to be less visible as compared to the inferior RNFL. Blood vessels are tortuous and along the inferotemporal vessels, there is presence of a white sheen (green arrow) and cotton wool spots (red arrow). There are microaneurysms, dot and flame shaped haemorrhages (yellow arrow), indicative of diabetic retinopathy.
Figure 2 shows fundus photograph of left eye centered at disc. Optic disc shows a VCDR of 0.6:1, similar appearance of RNFL as in right eye which is more prominent seen inferiorly than superiorly. Blood vessels are tortuous with a white sheen along the inferior arcade (green arrow). There are multiple microaneurysms, dot and flame shaped haemorrhages (yellow arrow) with significant cotton wool spots (red arrow) seen nasally and inferiorly.
Figure 3 shows retinal nerve fibre layer (RNFL) thickness map from SD-OCT, which shows significant thinning superotemporally and superonasally and early thinning inferiorly (blue arrow).
Figure 4 shows SD-OCT RNFL thickness map, which shows normal thickness of RNFL in all the quadrants.
Figure 5 shows ganglion cell layer thickness map of the right eye. Figure 5B shows GCL thickness deviation map, where some thinning of the GCL is noted superotemporally (white arrow). However there is thickening of the nasal GCL seen as grey areas in figure 5A (white arrow). On observation of the segmented layers of the retina, hyper reflective areas are seen involving the GCL (figure 5C). These are often seen even in normal eyes, but can also be due to the presence of localised macular oedema.  However  no localised area of retinal oedema was noticed in the  retinal layers in the area of GCL thickening. 
Figure 6 shows ganglion cell layer thickness map of the left eye. Figure 6B shows ganglion cell layer (GCL) thickness deviation map of left eye showing some loss inferiorly (white arrow). Figure 6A also shows thickening of the GCL seen as grey areas (white arrow). There is presence of similar hyper reflective areas involving the GCL as in the right eye (Figure 6C).

Discussion

When assessing a diabetic patient for glaucoma, increase in RNFL thickness due to oedema or cotton wool spots and increase in ganglion cell layer thickness due to macular oedema may be kept in mind, since they may lead to a false  diagnosis.  In this context the segmentation of the retinal layers should be visualised and the deviation map be assessed to rule out any pathology that might influence the layers under study. In this particular  case,  we  could not on clinical visualisation of the retinal layers identify the presence of localised GCL thickening due to diabetic retinopathy. There may be an additional value in a structure-structure correlation between the appearance of the colour photographs, retinal nerve fiber layer and the ganglion cell layer, in assessing, understanding and managing our patients

ReadWise

  1. Lim HB, Sung JY, Ahn SI, Jo YJ, Kim JY. Retinal nerve fiber layer thickness in various retinal diseases. Optometry and Vision Science. 2018 Mar 1;95(3):247-55. doi: 10.1097/OPX.0000000000001181
  2. Salvi L, Plateroti P, Balducci S, Bollanti L, Conti FG, Vitale M, Recupero SM, Enrici MM, Fenicia V, Pugliese G. Abnormalities of retinal ganglion cell complex at optical coherence tomography in patients with type 2 diabetes: a sign of diabetic polyneuropathy, not retinopathy. Journal of Diabetes and its Complications. 2016 Apr 1;30(3):469-76. https://doi.org/10.1016/j.jdiacomp.2015.12.025

Correspondence 

Dr Vinay Nangia
MS, FRCS, FRCOphth
Director 
Suraj Eye Institute
Nagpur
Email –education@surajeye.org

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