CASE REPORT

Fresnel prism effect and chromatic aberration produced by posterior capsular folds after intraocular lens implant

Ali, Zaria C. MBChB; Usmani, Hasan A. MBBS, FEBO, PGCert, FRCOphth; Vishwanath, Mandagere FRCS(Ed)

Author Information
Journal of Cataract and Refractive Surgery: July 2020 - Volume 8 - Issue 3 - p e00021
doi: 10.1097/j.jcro.0000000000000021
  • Free

Abstract

Phacoemulsification and intraocular lens implantation is now a routine procedure that can be performed in patients who still have a relatively good visual acuity, and patient expectation of the end visual outcome and function is often high.1 Patients may undergo uneventful cataract surgery and may achieve a good refractive outcome; however, they may have the phenomenon of dysphotopsias. These are visual disturbances that can include flashes of light, halos, glare (positive dysphotopsia), and shadows or darkening of vision (negative dysphotopsia).2 The presence of these dysphotopsias is often disconcerting and can lead to patient dissatisfaction after an otherwise successful operation with good visual acuity.2,3 We present a new and, to our knowledge, previously unreported type of positive dysphotopsia that we believe resulted from the presence of posterior capsular folds, and its subsequent management.

CASE REPORT

A 73-year-old man presented complaining of seeing multicolored ray of light obliquely across luminous sources from his left eye. He described this as a diagonal line running from the top right of his visual field to the bottom left of the visual field on his left eye (Figure 1). The line consisted of alternating green and red rays. The man had had uncomplicated phacoemulsification surgery 3 weeks earlier with a hydrophilic acrylic injectable intraocular lens (Rayner C-flex) placed in the capsule. Despite the symptoms, his postoperative uncorrected visual acuity was 0.0 logarithm of the minimum angle of resolution (logMAR) for this eye. On slitlamp examination, he was found to have 3 folds on the posterior capsule, which were perpendicular to the axis of the line of the red and green rays (Figures 2 and 3). This was managed with routine Nd:YAG laser posterior capsulotomy. The symptoms completely resolved instantly without complications, resulting in a final uncorrected visual acuity of −0.1 logMAR.

Figure 1.
Figure 1.:
Patient's own drawing of multicolored ray of light seen obliquely across luminous sources.
Figure 2.
Figure 2.:
Anterior segment photography showing 3 posterior capsule folds.
Figure 3.
Figure 3.:
Patient's drawing superimposed onto the image of the posterior capsular folds.

DISCUSSION

Posterior capsular folds can commonly occur after phacoemulsification and may lead to the development of posterior capsular opacifications and visual disturbances.4 The optical aberrations caused by folds on its own as opposed to secondary opacification are uncommon and may be overlooked.

Although the phenomenon of seeing a perpendicular ray secondary to folds has been reported before, the prismatic effect leading to a multicolored beam has not. We believe that the uniquely multiple oblique folds of the capsule in our subjects may have induced a Fresnel prism effect (Figure 4) with additional chromatic aberration causing the alternating red-green lines across the diagonal. As there were multiple folds, they could at as multiple prisms creating a line perpendicular to the prisms. Because they were central and likely sitting near the nodal point, there was minimal displacement of the image and so there was no diplopia. The identification of the folds as the cause of visual disturbance played an important factor in terms of further investigation and patient management. Visual disturbance after phacoemulsification is often a cause for concern because it can be indicative of a postoperative complication.5 When there is no obvious pathology seen, such as cystoid macular edema or postoperative inflammation, it can be difficult to discern why the patient is experiencing difficulties with their vision. It may have been assumed at this point that our patient had a positive dysphotopsia, which is related to the intraocular lens shape and position.3,6 Assuming it was a positive dysphotopsia could have led to inappropriate use of the Nd:YAG to laser the anterior capsule or more invasive measures such as inserting a piggyback intraocular lens or even a lens exchange.7

Figure 4.
Figure 4.:
Diagram demonstrating how folds may have induced a Fresnel prism–like effect.

To avoid issues with posterior folds, we suggest that if folds are seen during the operation, fluid is injected until the folds are flattened. It is also important to ensure that the wounds are sealed sufficiently, so there is no leak and subsequent development of folds.

To our knowledge, there is no other report of a patient having this particular visual phenomenon and chromatic aberration after phacoemulsification. Through our case, we highlight that a thorough examination can find a simple solution for a seemingly complex presenting complaint and can avoid unnecessary investigations and invasive procedures.

WHAT WAS KNOWN

  • Patients can have dysphotopsias after seemingly uneventful cataract surgery leading to dissatisfaction despite a good refractive outcome.
  • These can be difficult to treat and may lead to invasive procedures such as intraocular lens exchange to try and resolve the visual disturbance.

WHAT THIS PAPER ADDS

  • A new type of dysphotopsia, a multicolored line caused by posterior folds, was treated simply with YAG capsulotomy.
  • The cause of the dysphotopsia and how it might be avoided is discussed.

REFERENCES

1. Tielsch JM, Steinberg EP, Cassard SD, Schein OD, Javitt JC, Legro MW, Bass EB, Sharkey P. Preoperative functional expectations and postoperative outcomes among patients undergoing first eye cataract surgery. JAMA Ophthalmol 1995;113:1312–1318
2. Davison JA. Positive and negative dysphotopsia in patients with acrylic intraocular lenses. J Cataract Refract Surg 2000;26:1346–1355
3. Tester R, Pace NL, Samore M, Olson RJ. Dysphotopsia in phakic and pseudophakic patients: incidence and relation to intraocular lens type(2). J Cataract Refract Surg 2000;26:810–816
4. Meacock WR, Spalton DJ, Boyce J, Marshall J. The effect of posterior capsule opacification on visual function. Invest Ophthalmol Vis Sci 2003;44:4665–4669
5. Chan E, Mahroo OAR, Spalton DJ. Complications of cataract surgery. Clin Exp Optom 2010;93:379–389
6. Schwiegerling J. Recent developments in pseudophakic dysphotopsia. Curr Opin Ophthalmol 2006;17:27–30
7. Hu J, Sella R, Afshari NA. Dysphotopsia: a multifaceted optic phenomenon. Curr Opin Ophthalmol 2018;29:61–68
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