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Dysphotopsia: Elucidating The Riddle

by | Mar 1, 2022 | Manuscripts | 0 comments

Aishwarya Jha, B.Optometry

Fellow Optometrist, Dr Shroff’s Charity Eye Hospital, Delhi, India

 

Dysphotopsia is a digressive optical phenomenon occurring after the implantation of an IntraOcular Lens (IOL). It is common after an uncomplicated, successful cataract surgery. This condition is presented as unwanted images particularly in form of flashes, arcs streaks, starbursts, rings, or halos occurring either centrally or mid-peripherally in Positive Dysphotopsia (PD), & as a dark shadow or temporal arcing shadow or a crescent in negative Dysphotopsia (ND).

The aetiology of dysphotopsia remains unclear. Some leading hypotheses suggest the cause of Positive Dysphotopsia include the shape, size, refractive index, and the material of IOL.(1) It is demonstrated that the obliquely oriented light ray striking the  truncated square edges of the IOL reflect on to the retina and induce the symptoms of Positive Dysphotopsia (PD). (2) A high refractive index is also a causal factor for the development of PD.(3)

Negative Dysphotopsia (ND) is likely to be multifactorial and is not as clearly understood as PD. The leading hypothesis describes the cause as an “illumination gap” between the light rays that are refracted by the IOLs and those that miss the lenses optic and go to one part of the periphery. (4) Multiple studies suggest Negative Dysphotopsia symptoms are more  frequent with thick IOLs rather than thin IOLs.(1) Also some hypotheses suggest that ND can occur with small pupil, large kappa value, sharp IOL edge design, acrylic material, decentration, tilt, and aspheric surface. (5)

Intraocular Lens and Dysphotopsia

In mesopic or scotopic conditions, when the pupil is large enough for the incident ray to strike near or on the edge of the IOL, the nasal edge of the IOLs seemingly scatter light which is perceived as multiple images by the patient on the temporal side thus results in Dysphotopsia (positive). An internal reflection from the front surface of the IOL can also cause PD, when angle of incidence exceeds the critical angle (CI). A glare source positioned at or around 35⁰ off the visual axis creates an internal reflection within the IOL that is projected on the temporal retina. (6)

Negative Dysphotopsia is a less understood and more debilitating condition than PD. Scattering of  light at the  nasal edge of IOL,  leads to a dark area on the retina and perceived as a dark shadow by the patient hence  perceived only in the temporal area as the nose blocks the nasal part. It manifests after perfect in-the-bag Posterior Chamber Intraocular Lens (PC-IOL) implantation surgery.(5)

Management

Non-surgical approaches:

  • Pharmacologic miotic drugs pilocarpine and brimonidine can help relieve PD.
  • Spectacles with a thick frame.
  • By making the anterior portion of the square edge IOLs rounder, reducing the thickness of the IOL square edge, and moving the IOL optical power more anterior rather than posterior.

Surgical approaches:

  • To reduce Positive Dysphotopsia using IOL materials with a lower refractive index, reduces surface reflectivity.(2)
  • IOLs exchange to (PMMA), silicone, or copolymer IOLs has been reported to be most successful.(2)
  • Reverse optic capture has been shown to ameliorate Dysphotopsia.(7)

 

References:

  1. Masket S, Fram NR. Pseudophakic dysphotopsia: review of incidence, cause, and treatment of positive and negative dysphotopsia. Ophthalmology. 2021 Nov 1;128(11):e195-205.
  2. Masket S, Rupnick Z, Fram NR, Kwong S, McLachlan J. Surgical management of positive dysphotopsia: US perspective. Journal of Cataract & Refractive Surgery. 2020 Nov 1;46(11):1474-9.
  3. Holladay JT, Bishop JE, Lewis JW. Diagnosis and treatment of mysterious light streaks seen by patients following extracapsular cataract extraction. American Intra-Ocular Implant Society Journal. 1985 Jan 1;11(1):21-3.
  4. Holladay JT, Simpson MJ. Negative dysphotopsia: causes and rationale for prevention and treatment. Journal of Cataract & Refractive Surgery. 2017 Feb 1;43(2):263-75.
  5. Holladay JT, Zhao H, Reisin CR. Negative dysphotopsia: the enigmatic penumbra. Journal of Cataract & Refractive Surgery. 2012 Jul 1;38(7):1251-65.
  6. Kinard K, Jarstad A, Olson RJ. Correlation of visual quality with satisfaction and function in a normal cohort of pseudophakic patients. Journal of Cataract & Refractive Surgery. 2013 Apr 1;39(4):590-7.
  7. Masket S, Fram NR, Cho A, Park I, Pham D. Surgical management of negative dysphotopsia. Journal of Cataract & Refractive Surgery. 2018 Jan 1;44(1):6-16.

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