Postoperative discoloration of a multifocal hydrophobic acrylic lens: case report with laboratory analyses

Abstract

Introduction: 

A case of discoloration of a multifocal hydrophobic acrylic intraocular lens (IOL), which was explanted and exchanged as well as underwent laboratory analysis, is reported.

Patient and Clinical Findings: 

The patient presented with a corrected distance visual acuity of 20/50 and glare in the right eye 8 years after implantation. Slitlamp examination revealed a nasally decentered IOL with a whitish-brownish haze throughout.

Diagnosis, Intervention, and Outcomes: 

The discolored IOL (ZMB00) was explanted and exchanged for a 3-piece IOL (sulcus fixation). Grossly, the explanted IOL showed a whitish discoloration of the optic only after hydration, corresponding to a yellowish-brownish discoloration observed under light microscopy. Back light scattering revealed bulk scatter throughout the optic. Light transmittance (%T) showed a slight progressive decrease starting at 500 nm when compared with %T in the directions for use (DFUs). Although modulation transfer function analysis demonstrated similar values to the control lens, the contrast of U.S. Air Force targets appeared slightly decreased.

Conclusions: 

To the authors' knowledge, this is the first reported case of a discolored ZMB00 IOL that underwent explantation and laboratory assessment. Although current analyses did not reveal the etiology of the discoloration, surgeons should be aware of this possible occurrence with this lens design and carefully assess signs and symptoms before explantation.

Various pathologic processes may lead to opacification or discoloration of the optic component of intraocular lenses (IOLs) composed of different materials.¹ Factors such as patient-associated conditions, manufacturing process, method of IOL storage, surgical technique and adjuvants, or a combination of these may be involved.¹ Distinguishing between IOL opacification/discoloration and posterior capsular opacification is crucial to prevent unnecessary procedures, such as Nd:YAG posterior capsulotomy or vitrectomy.² In 2016, Wong et al. reported a series of 16 cases of brown discoloration of hydrophobic acrylic IOLs manufactured by Abbott Medical Optics (now Johnson & Johnson Vision).³ The patients were asymptomatic, and no explantation was performed in that study. The present case uniquely reports a brown discoloration of a multifocal hydrophobic acrylic IOL from the same manufacturer, which was explanted/exchanged and has undergone laboratory analysis.

Patient Consent Statement

Written informed consent was obtained from the patient for publication of deidentified information in this case report. This study was performed in accordance with HIPAA regulations and the tenets of the Declaration of Helsinki. The Institutional Review Board (University of Utah) sanctioned the study design, data collection, and storage.

CASE REPORT

In March 2022, a 69-year-old pseudophakic Southeast-Asian man presented to one of us (J.M.M.) with a corrected distance visual acuity (CDVA) of 20/50 in the right eye (+1.00 −0.25 at 96 degrees) and severe symptoms of glare/halos, which developed over the recent years. The patient had received a TECNIS multifocal 1-piece IOL, ZMB00 (Abbott Medical Optics, Illinois, USA), in 2014 (surgery performed in Vietnam). He had a history of metformin intake for type 2 diabetes mellitus, as well as smoking (1 pack of cigarettes per week). Slitlamp examination of the right eye revealed a clear cornea, a flat iris, and a nasally decentered IOL, which also exhibited a whitish-brownish haze (Figure 1). The left eye had a CDVA of 20/20 (0.00 −0.50 at 88 degrees) and a centered monofocal posterior chamber IOL. Early signs of posterior capsular opacification were noted in the left eye. Intraocular pressure (IOP) was 15 mm Hg in both eyes. Examination of the posterior segment showed an epiretinal membrane in the right eye, and no signs of diabetic retinopathy were noted. The patient was seen again in April 2022, when a possible posterior capsule break was noted in the right eye (the patient had no history of previous posterior capsulotomy). It was suspected that this was a case of dead bag syndrome, with subluxation of the IOL through the capsular break in this eye.⁴

Figure 1.: Slitlamp examination photograph of the right eye revealing a clear cornea, a flat iris, and a nasally decentered IOL with a whitish-brownish haze throughout the optic substance.

Operative Management

Appropriate consent was obtained, and an IOL exchange was performed in the right eye. The original discolored multifocal IOL was removed through the modified twist-and-out technique to keep it whole for laboratory analyses.⁵ Briefly, 2 paracenteses were created with a 1 mm side-port blade, and the anterior chamber (AC) was filled with a dispersive ophthalmic viscosurgical device (OVD). The IOL was carefully dissected away from the capsular bag and prolapsed into the AC. Anterior vitrectomy was performed to free the IOL of any vitreous before extraction. The right-sided paracentesis was enlarged with a 2.4 mm keratome, and the IOL was positioned with 1 haptic in the main wound. A paracentesis was created 180 degrees away from the left-most paracentesis, and the shaft of a 25-gauge cannula was placed across the AC to connect these two incisions. Toothed 0.12 forceps were used to grasp and slowly twist the IOL counterclockwise, away from the hub of the cannula, using the cannula shaft placed across the AC to guide the IOL around the forceps while protecting the endothelium. Once the IOL was well wrapped, the forceps were withdrawn and the IOL inspected to ensure complete removal. The 25-gauge cannula shaft was removed and the OVD inserted to enlarge the sulcus. A 3-piece IOL (Alcon MA60AC) was then inserted into the sulcus, the OVD was removed with bimanual irrigation/aspiration, and the wounds were sealed.

Postoperative Course

On day 1, the CDVA was 20/100, with an IOP of 16 mm Hg. There was mild corneal edema and aqueous cells (graded +1). The 3-piece IOL was found to be well centered. At week 1, the CDVA improved to 20/60, with an IOP of 15 mm Hg. The eye had a residual corneal edema, punctate epithelial keratopathy, and an epiretinal membrane. The CDVA returned to the baseline (20/50) at week 6, with a resolution of the glare/halo symptoms.

Laboratorial Analyses

The explanted discolored IOL was received dry in a plastic specimen container. Gross examination was performed, and gross pictures were taken using a Nikon digital camera (model D1x with a Nikon ED 28 to 70 mm AF lens). Microscopic examination and photographs under a light microscope (Olympus Optical Co., Ltd.) were also completed in both the dry and hydrated states (after immersion in distilled water for 24 hours at body temperature). Back light scattering was assessed with Scheimpflug photography. A purpose-designed 3-piece dark-eye model with a poly(methyl methacrylate) cornea was used to hold the IOL under immersion in distilled water. The assembly was then placed in front of an EAS-1000 Scheimpflug camera (Nidek, Inc.) (cornea facing the device), and the room lights were turned off. A cross-sectional image of the IOL inside the model was obtained (settings: flash level 200 W, slit length 10.0 mm, and meridian angle 0). Light transmittance was measured with a Lambda 35 UV/Vis spectrophotometer (PerkinElmer, Inc.) operated in a single-beam configuration with an RSA PE-20 integrating sphere (Labsphere, Inc.). The lens was fitted to a plastic custom insert with a 5.0 mm diameter aperture for the optic. The insert containing the IOL was mounted in a rectangular quartz cuvette filled with distilled water. The assembly was then placed directly in front of the opening of the integrating sphere, so the anterior surface of the IOL faced the light source. The IOL spectrum was then collected at room temperature with the following settings: wavelength range 850 to 300 nm, slit width 2 nm, scan speed 120 nm/min, and data interval 1 nm.

Power and modulation transfer function (MTF) measurements for 2 mm, 3 mm, and 4.5 mm pupils were taken using the PMTF device (Lambda-X S.A.), designed for refractive and diffractive IOLs. It is ISO 11979-2 compliant, has an ISO 11979-2 model eye 1, and uses a measurement wavelength of 546 nm. This assessment was performed for the explanted lens and a never-used lens of the same design (ZMB00; +20 D with +4.0 D add; SN: 8235071308).

Gross and microscopic examination in the dry state did not reveal any opacification/discoloration. Deposits corresponding to a dry OVD, as well as marks secondary to maneuvering of the implant with forceps during explantation, were noted on microscopic examination (Figure 2, A). In the hydrated state, the IOL optic showed a distinct whitish discoloration under gross examination, corresponding to a yellowish-brownish discoloration observed under light microscopy (Figure 2, B). The fact that discoloration/opacification is only observed when the lens is hydrated suggests the influx of water as the discoloration/opacification mechanism in a lens that is normally hydrophobic. Regarding back light scattering, Scheimpflug photograph revealed a bulk scatter throughout the substance of the optic of the explanted lens after complete hydration, similar to the aspect observed under slitlamp examination (Figures 1 and 2C). Light transmittance (%T) in the visible light spectrum (400 to 700 nm) was 93.65%. Although we did not have a control lens for this assessment, the light transmission curve (Figure 3, A) was compared with the curve presented in the directions for use for model ZMB00 (DFUs; https://www.precisionlens.net/wp-content/uploads/JJ-TMF-4.0-DFU.pdf; assessed on September 6, 2022; Figure 3, B). The curve of the explanted lens showed a slight progressive decrease of %T starting at 500 nm, not present in the DFU curve. The UV cutoff at 10%T was approximately at 380 nm in the DFU curve and approximately at 379 nm in the curve of the explant. The contrast of the U.S. Air Force targets appeared slightly decreased in comparison with that of the control, although the MTF of the explanted lens was similar to that of the control (Figure 4, A–D).

Figure 2.: Photographs of the explanted IOL. A: IOL in the dry state; the optic is colorless and exhibits deposits corresponding to a dry OVD, as well as forceps marks. B: IOL in the hydrated state; a yellowish-brownish discoloration can be seen, especially in the central part of the optic. C: Cross-sectional Scheimpflug image from the explanted IOL demonstrating intense optic bulk scatter. A and B: Light microscopy; original magnification 20×.

Figure 3.: A: Light transmission (%T) curve (between 850 nm and 300 nm) of the explanted IOL. The dashed rectangle shows an area of slight progressive decrease of %T starting at 500 nm. B: Same curve obtained from the DFU, for comparison; https://www.precisionlens.net/wp-content/uploads/JJ-TMF-4.0-DFU.pdf; assessed on September 6, 2022 (1 = 5.0 D IOL; 2 = 34 D IOL; 3 = 53-year-old phakic eye).

Figure 4.: Optical analyses of the explant. A: USAF target image with the explanted lens (3.0 mm pupil; far). B: USAF target image with the control (3.0 mm pupil; far). C: MTF curves of the explanted lens (50 and 100 lp/mm; in distilled water at 35°C; 3.0 mm pupils). D: MTF curves of the control (50 and 100 lp/mm; in distilled water at 35°C; 3.0 mm pupils). MTF = modulation transfer function; USAF = U.S. Air Force

DISCUSSION

In hydrophobic acrylic IOLs, increased light scattering associated with the presence of subsurface nanoglistenings may give the IOL surface an appearance of whitish discoloration when the light is directed at the IOL at an angle of incidence of at least 30 degrees during slitlamp examination or during image capture at an angle of 45 degrees with Scheimpflug photography.⁶ Nanoglistenings are usually concentrated in the subsurface of the optic, not within the optic substance, and are much smaller than glistenings. The later are microvacuoles filled with fluid that can be observed within the substance of the lens.⁷ Glistenings and subsurface nanoglistenings have been rarely reported as causes of IOL explantation.^6,7

Wong et al. reported on brown discoloration of hydrophobic acrylic IOLs in 16 eyes of 14 patients (11 AAB00, 3 ZCB00, and 2 ZMB00 IOLs) observed between 1 to 327 days after phacoemulsification (mean time 158.5 days).³ Uneventful surgeries were reported in all but one patient who had a posterior capsule rupture requiring anterior vitrectomy. Prolonged postoperative inflammation was observed in four patients, which responded to topical corticosteroids in all but one patient who subsequently developed pigment dispersion glaucoma requiring a trabeculectomy. Overall, the discoloration could not be attributed to a clinical cause, and none of the IOLs required explantation. The desaturated Lanthony D-15 Hue test was found to be abnormal in 8 of the 16 eyes, but no patient reported abnormal color perception.

In our report, laboratory analyses of the explanted lens were provided for the first time in such cases, to our knowledge. The opacification/discoloration could be reproduced in vitro and was associated with small changes in the light transmittance curve, as well as U.S. Air Force target contrast. It is difficult, though, to establish any clinical significance of the opacification/discoloration in the present case because the lens has a diffractive optic and was decentered, which could lead to glare symptoms. It is possible that the opacification/discoloration is related to light scattering because of water vapor diffusing throughout the lens, as it is only observed in the hydrated state. Similar observations have been reported with early silicone IOLs by Milauskas, which were apparently related to the manufacturing process.⁸ Approximately 20 years later, the same author reported on brown discoloration of blue light–filtering hydrophobic acrylic IOLs manufactured by Alcon and Hoya.⁹ Although our current analyses do not allow us to establish the exact etiology of the water influx into this hydrophobic acrylic IOL, leading to opacification/discoloration, surgeons should be aware of this possible finding with the ZMB00 lens design and carefully assess signs and symptoms, before deciding on explantation. Light transmittance and contrast changes in this opacified lens were overall mild and likely clinically insignificant.

WHAT WAS KNOWN

• Various pathologic processes may lead to opacification or discoloration of IOLs composed of different materials.

WHAT THIS PAPER ADDS

• To the authors' knowledge, this is the first report of a discolored ZMB00 IOL that underwent explantation and laboratory assessment.
• Although our current analyses do not establish the exact etiology of the water influx into this hydrophobic acrylic IOL, leading to opacification/discoloration, surgeons should be aware of this possible finding with this lens design, before considering explantation.