The Petal of Sight
Dr. Rashmi Nagar, Dr. Sarang Lambat, Dr. Prabhat Nangia, Dr. Vinay Nangia
Suraj Eye Institute, 559 New Colony, Nagpur
A male, 50 years of age came to our institute for a regular eye examination. His best corrected visual acuity was 6/6, N6 with a correction of -0.50 DS and presbyopic addition of +1.75D in both eyes. Slit lamp examination showed normal anterior segment. Intra-ocular pressure was 22 mmHg in both eyes. His central corneal thickness was measured to be 509 microns in the right eye (RE) and 513 microns in the left eye (LE). He was not on any treatment.
On dilated fundus examination vertical cup-disc ratio (VCDR) was noted to be 0.90 in the right eye and a VCDR of 0.8 in the left eye. A diffuse loss of retinal nerve fibre layer sparing only the macula was seen in both eyes. He was started on Levobunolol 0.5% eye drops in both eyes.
Our patient presented rather late with significant glaucomatous damage in both eyes. There was presence of significant loss of RNFL superiorly and inferiorly to the extent, that there was evidence of a flooring effect. One may have expected a significant degree of loss of the macular RNFL also. However, the macular fibers are relatively preserved. We would like to call this ‘Macular Sparing in Glaucoma’ in individuals who present with significant loss of RNFL superiorly and inferiorly with classical optic disc damage.
The color photographs Figure 1(a,b) and Figure 2(a,b) show the presence in the RE and LE of preserved macular retinal nerve fiber layer outlined with the yellow dashed lines. The appearance is that of a petal. Let us call this the ‘Petal of Sight’, due to the preservation of the macular RNFL and also the relative preservation of the ganglion cell layer thickness in the heat maps. (Figure 5A and figure 6A). There is also associated preservation of the RNFL in the macula (Figure 3B- yellow arrows and Figure 4B- yellow arrows).
Figure 7 shows the edges of the preserved macular fibers in RE and Figure 8 shows the edges of the preserved macular fibers in the LE. The Hood report, which brings the macular fibers in the center, using the Nasal Superior, Temporal, Inferior and Nasal (NSTIN) arrangement of the RNFL shows the preserved macular fibers in Figure 9(A-yellow arrows, D-red arrows) in RE and Figure 10(A-yellow arrows, D-red arrows) in LE.
The phenomena of relative but significant preservation of the macular fibers and the central ganglion cells in advanced glaucomatous damage may be found in some glaucoma subjects. This leads to the preservation of central vision even through the optic disc shows significant damage, which is a source of anxiety, because the appearance of glaucomatous damage may portend impending blindness.
The cause of the ‘Petal of Sight’ and ‘Macular Sparing in Glaucoma’ is not clear. That is, we may not be able to predict which patient is relatively more protected through this phenomenon from visual impairment and or blindness. The phenomena are important, since there is a natural selection of patients who in spite of advanced glaucomatous damage may continue to preserve their central vision for a much longer period of time, allowing them to live with a reasonable quality of life.
- Hood, Donald C., et al. “The nature of macular damage in glaucoma as revealed by averaging optical coherence tomography data.” Translational vision science & technology 1.1 (2012) doi:https://doi.org/10.1167/tvst.1.1.3
- Kim, Ko Eun, and Ki Ho Park. “Macular imaging by optical coherence tomography in the diagnosis and management of glaucoma.” British Journal of Ophthalmology102.6(2018):718-724.DOI:10.1136/bjophthalmol-2017-310869
Dr Vinay Nangia
MS, FRCS, FRCOphth
Suraj Eye Institute