Spark Imagewise-67 Optic disc drusen with retinal nerve fiber layer defects

Dr. Ravi Daberao, Dr. Sarang Lambat, Dr. Prabhat Nangia, Dr. Vinay Nangia
Suraj Eye Institute, Nagpur

Case Description
A female, 25 years of age presented to us for glaucoma evaluation. Her best corrected visual acuity was 6/6 in both eyes. Her refraction was -3.00 DS in the right eye (RE) and -2.25 DS in the left eye (LE). Anterior segment examination of both eyes was normal. Intraocular pressure of both eyes was 15 mmHg. Gonioscopy showed open angles in both eyes. Her right eye axial length was 23.58 mm and her left eye was 23.47 mm. The central corneal thickness in right was 577 microns and in the left eye was 579 microns.

Fig. 1 Colour fundus photograph of the right eye showed a small disc with no visible cup and associated blurring of the disc margin (red arrow). Yellow deposits were visible on the surface and partially embedded in the optic disc tissue (blue arrow). Retinal nerve fiber layer defect was noted superiorly and inferiorly (yellow arrows). Macula appears normal.

Fig. 2 Colour fundus photograph of the left eye showed a small disc with no visible cup and associated blurring of the disc margin (red arrow). Yellow deposits were visible on the surface and partially embedded in the optic disc tissue (blue arrow). Retinal nerve fiber layer defect was noted superiorly and inferiorly (yellow arrows). Macula appears normal.

Fig.3 Right eye OCT circumpapillary retinal nerve fiber layer (RNFL) showed significant thinning of temporoinferior RNFL (Fig.3b, yellow arrow) and (Fig.3d, black arrow). The thinning of nasal RNFL (Fig. 3b and Fig.3d, red arrows) and global RNFL is also noted. The distribution of RNFL allows for an apparent thickening of the macular RNFL.

Fig.4 Left eye OCT circumpapillary retinal nerve fiber layer (RNFL) showed significant thinning of RNFL of the inferotemporal, superotemporal and nasal segments (Fig.4b, white arrows) and (Fig.4d, black arrows). The macular RNFL appears to be normal.

Fig.5 Right eye posterior pole deviation map showed ganglion cell layer thinning (Fig.5 A, red arrow). The Macular GCL deviation map showed focal thinning in the temporoinferior area (Fig.5 B, yellow arrow). The GCL classification map also shows thinning in the inferotemporal sector (Fig. 5 D, blue arrow).

Fig.6 Left eye posterior pole deviation map showed ganglion cell layer thinning (Fig.6 A, red arrow). The Macular GCL deviation map showed focal thinning in the temporal area (Fig.6 B, yellow arrow). The GCL classification also shows significant thinning of the temporal and inferior sectors (Fig. 6D, blue arrow).

Fig.7 Right eye Humphrey Field Analyzer [HFA] 24–2 SITA‐Standard showed nasal visual field loss (red arrow).

Fig.8 Left eye Humphrey Field Analyzer [HFA] 24–2 SITA‐Standard showed nasal visual field loss (red arrow).

Discussion

Our patient came to us for a routine eye evaluation and on examination of the retina, optic disc drusen were detected. The clinical appearance of optic disc drusen gives an impression that drusen are present both on the surface and partially embedded with in the disc tissue. The completely embedded disc drusen will not be visible. In the right eye, they are more visible on the temporal margins of the optic disc, while in the LE they are more visible all over around the margins of the optic disc. Because of the number of drusen present in the left optic disc, the disc appears pale due to the color of the drusen. (Fig 2, blue arrow). The optic disc size is small in both eyes and the margins of the disc cannot be made out clearly.

There is the presence of retinal nerve fiber layer defects superotemporally and inferotemporally (Fig 1, yellow arrows). These appear as classic defects but are not typically wedge-shaped, with the apex at the disc margin. In the left eye also supratemporal and inferotemporal RNFL defects can be seen. (Fig 2, yellow arrows)

The RNFL of the right eye on the OCT shows thinning inferotemporally, nasally, and superotemporally. The macular nerve fibers are not affected and are very healthy. (Fig 3b,3c, and 3d, red, yellow, and black arrows). In the LE also, there is significant thinning of the RNFL (Fig 4a, b, c, and, white and black arrows). In the LE, the macular fibers are unaffected and healthy.

The GCL heat maps of the right eye show the loss of GCL (Fig 5a, red arrow) along the inferotemporal sector. This is also manifested in the deviation map (Fig5 b, yellow arrow). In the LE, there is a significant loss of ganglion cells (Fig 6a, red arrow and Fig 6 b, red arrow) on the temporal side of the fovea, extending further superotemporally and inferotemporally.

While the drusen are distributed all across the optic disc, it is hard to ascertain and explain why some areas of the RNFL may be more affected than others. However, in the left eye, there is generalized involvement of all sectors. Further, it is important to see that the macular sector RNFL is well preserved.

If we take a look at the ganglion cell layer maps, we find that the defects are typical of the pattern of glaucomatous loss. It is also important to see that the GCL towards the optic disc has not been affected. Therefore, the mechanism, while not ideally that of glaucomatous damage, is also not clearly of a neurological type. This can only mean good things for the eye since neurological damage could have led to early loss of vision by involving the macular ganglion cells directly responsible for good vision.

Automated perimetry showed the presence of nasal visual field defects seen in both eyes (Fig. 7,8). This correlates with the RNFL (Fig. 3,4). and GCL loss (Fig 5,6).

The IOP of the patient was normal. However, the presence of significant RNFL loss suggests that a regular follow-up must be done. There is no obvious way of preventing further RNFL damage. However, it is possible that the damage may not lead to blindness. The RNFL loss that takes place is likely on account of the possible enlargement of the drusen seeking more space in the constrained prelaminar area and leading to RNFL damage. However, once the drusen have created a space for themselves, one may hope that further loss may not occur if the drusen stop growing.

ReadWise

Roh S, Noecker RJ, Schuman JS, Hedges TR 3rd, Weiter JJ, Mattox C. Effect of optic nerve head drusen on nerve fiber layer thickness. Ophthalmology. 1998 May;105(5):878-85. doi: 10.1016/S0161-6420(98)95031-X. PMID: 9593392; PMCID: PMC1937403.
Malmqvist L, Wegener M, Sander BA, Hamann S. Peripapillary Retinal Nerve Fiber Layer Thickness Corresponds to Drusen Location and Extent of Visual Field Defects in Superficial and Buried Optic Disc Drusen. J Neuroophthalmol. 2016 Mar;36(1):41-5. doi: 10.1097/WNO.0000000000000325. PMID: 26720518.

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

QuizWise

Q1 Optic disc drusen are made of?
a Hyaline deposits
b Calcium
c Amyloid
d All of the above

Q 2 Which condition is associated with disc drusen?
a. Retinitis pigmentosa
b. Age-related macular degeneration
c. Retinal detachment
d. Retinoschisis

Q 3 All of the following are investigations for diagnosis of disc drusen except?
a. Magnetic resonance imaging (MRI)
b. Autofluorescence
d. B-scan ultrasonography
e. Orbital computed tomography (CT)

Q4 Visual loss due to optic disc drusen can result from?
a. Optic atrophy
b. Retinal detachment
c. Papilloedema
d. Venous occlusion
e. Peripapillary choroidal neovascularization

QuizWise Answers

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