In recent times the topic of Negative Dysphotopsia has gained some interest among surgeons, ever since the phenomenon was first discussed by James Davison in his article published in JCRS in 2000. Davison’s paper first drew the attention of the medical fraternity of the potential visual disturbance that may be caused in some patients post cataract surgery.
Samuel Masket, in his paper published in JCRS in 2011 describes Negative Dysphotopsia (ND) as a dark crescent in temporal field of vision. Note, this condition is different from positive dysphotopsia, wherein patients suffer from undesired optical halos and other photic issues.
Since the work of Davison and Masket, different clinical researchers and at different points of time have brought out different causes of ND. However, the following has often been pointed out as a cause of it –
a. ND may be associated with many different types of Posterior Chamber in the bag fixated IOLs, regardless of material/RI/round or squared edge.
b. Symptoms of ND have been reported to have been reduced by pharmacologic pupil dilation and increased by pupil constriction in the paper published by Masket in 2011.
c. It is not related to pre operative or post operative ametropia
d. ND symptoms have been reported typically within 1 month of cataract surgery with PC IOLs, but in most cases subside over a period of time. Very few cases of severe and persistent symptoms have been reported.
In a recent paper in the JCRS published in February 2018, Jack Holladay gives a scientific explanation of ND. In this paper, Holladay shows by ray tracing 📷that when extreme peripheral rays pass above an angle of 80 degree to the visual field ( see fig left ), some of the rays pass through the peripheral optic of the IOL and some rays reach the retina missing the IOL optic and thus reach unrefracted. If there is a gap between two retinal images formed, patients may see this as a dark temporal crescent. Holladay in this paper goes on to discuss the primary and secondary reasons of this gap between the two retinal images formed.
a. Holladay notes that patients with higher angle kappa are at more risk for ND. Note patients with hyperopia are noted to have higher angle kappa.
b. Very high dioptric power of the IOL ( Hyperopic Eyes )
c. Smaller photopic pupil were seen to have more ND in Holladay’s ray tracing study ( in contradiction to Masker study )
However, both Masket and Holladay have found out that the incidence of Negative Dysphotopsia is less, when the optic-haptic junction is placed horizontally. Hence it is strongly advised (in cases of non-TORIC ), surgeons who find frequent complaint of patients, may place the IOL oriented horizontally, aligning the haptics on the 0/180 deg meridian.
In a very rare case of persistent complaint of patient with ND, despite horizontal placement of IOL in the bag, the following has been advised in Masket and Holladay papers for surgical intervention :
a. Removal of anterior rim of capsulorhexis from the nasal part is the safest and first step to try to reduce persistent complaints of ND.
b. IOL lens exchange in the sulcus as a last step to mitigate patient condition.
c. Reverse optic capture
James Davison : Positive and Negative Dysphotopsia in acrylic IOL ; JCRS 2000
Jack Holladay : Negative Dysphotopsia : Causes and rationale for treatment ; JCRS 2017
Samuel Masket : Pseudophakic Negative Dysphotopsia ; JCRS 2011