Case report

Zonular weakness in patients with gyrate atrophy of the choroid and retina

Chao, Jonathan T.; Rao, Prethy MD, MPH; Hart, John C. Jr. MD*

Author Information
Journal of Cataract and Refractive Surgery Online Case Reports: October 2017 - Volume 5 - Issue 4 - p 69-72
doi: 10.1016/j.jcro.2017.10.002
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Abstract

Gyrate atrophy of the choroid and retina is a rare autosomal recessive inborn error in metabolism caused by a deficiency in ornithine aminotransferase (OAT), with an estimated incidence of less than 1 in 1 000 000 in the general population.1 Systemic findings of gyrate atrophy include hyperornithinemia, central nervous system involvement, and muscular atrophy.2 Ocular findings are characterized by progressive chorioretinal degeneration, high myopia, and, specifically, early cataract formation.3,4

Posterior subcapsular cataracts are the most common cataract subtype that form in the second decade of life in gyrate atrophy patients.5 Cataract extraction may be beneficial in preserving vision and is often performed in the third or fourth decade.5 However, little is known about the unique surgical anatomy, intraoperative approach, and postoperative course in these patients. Case reports have described in-the-bag intraocular lens (IOL) dislocation as a late postoperative complication.6,7 However, the exact mechanism remains unknown. We describe a previously unreported intraoperative clinical finding of zonular weakness in 2 female siblings (4 eyes) with gyrate atrophy of the choroid and retina.

CASE REPORTS

Case 1

A 38-year-old white woman with gyrate atrophy presented with a gradual decline in vision and light sensitivity over several months. On ocular examination, the corrected distance visual acuity (CDVA) was 20/80 with a manifest refraction of −19.50 +1.50 × 115 in the right eye and 20/200 with −20.0 +1.50 × 80 in the left eye. Slitlamp examination of the anterior segment showed posterior subcapsular cataracts in both eyes. No iris transillumination defects, iridodonesis, or phacodonesis was noted. Neither eye exhibited zonular weakness, which was defined as visualization of the edge of the crystalline lens through the pupil after pharmacologic pupillary dilation in the upright position. The posterior segment showed bilateral 360-degree macula-sparing chorioretinal atrophy. Partial coherence interferometry (IOLMaster, Carl Zeiss Meditec AG) showed an axial length (AL) of 31.7 mm and corneal curvatures of 42.20/43.35 diopters (D) in the right eye and an AL of 28.9 mm with a corneal curvature of 42.54/44.34 D in the left eye.

Cataract extraction and IOL implantation was performed under local sedation. Intraoperatively, with the patient in the supine position, 7 to 8 clock hours of zonular weakness were observed in the left eye after dilation (Figure 1). After a standard biplanar temporal clear corneal wound incision and paracentesis were made, a dispersive ophthalmic viscosurgical device (OVD) (Viscoat) was used to stabilize the anterior chamber for a continuous curvilinear capsulorhexis. Cortical cleaving hydrodissection separated the cortex completely from the capsular bag. The cataract was removed using aspiration only. After the capsular bag was filled with a cohesive OVD, a standard capsular tension ring (CTR) (ACTR 11, Alcon Laboratories, Inc.) was inserted into the capsular bag. Insertion of the CTR centered the capsular bag, and the edge of the bag was no longer visualized. A 3-piece acrylic IOL (MN60MA +0.0 D, Alcon Laboratories, Inc.) was inserted into the capsular bag. The IOL centered on the visual axis; there was no vitreous loss and no IOL dislocation.

Figure 1.
Figure 1.:
Seven to 8 clock hours of the crystalline lens edge were seen along the superior border after pharmacologic dilation in the left eye. Zonular weakness is clearly visible prior to OVD instillation. The still image illustrates approximately 6 clock hours of the total because of total internal reflection from the cornea.

Two weeks later, cataract surgery was performed in the right eye. After dilation, with the patient in the supine position, 6 to 7 clock hours of zonular weakness were seen (Figure 2). Cataract surgery was performed as in the left eye, with cortical cleaving hydrodissection separating the cortex completely from the capsular bag. The cataract was removed with aspiration alone. The CTR model used in the left eye was placed in the capsular bag followed by a 1-piece acrylic IOL (SN60WF +6.0 D, Alcon Laboratories, Inc.). After insertion of the CTR, the edge of the lens was no longer visualized.

Figure 2.
Figure 2.:
Six to 7 clock hours zonular weakness were seen in the right eye with the patient in the supine position. Zonular weakness was evident prior to the addition of OVD.

At the 1-year follow-up, the CDVA was 20/25 in the right eye and 20/80 in the left eye. No pseudophacodonesis was noted, and the rest of the ocular examination was unremarkable.

Case 2

A 35-year-old white woman with gyrate atrophy was referred by her sister (Case 1) with complaints of impaired night vision and decreased visual acuity. The CDVA was 20/200 with −15.75 +2.75 × 85 in the right eye and 20/400 with −16.5 +2.25 × 88 in the left eye. Slitlamp examination was significant for bilateral posterior subcapsular cataracts and peripheral chorioretinal atrophy. With the patient in the upright position, no iris transillumination defects, iridodonesis, phacodonesis, or other signs of zonular weakness were noted. Partial coherence interferometry showed an AL of 28.9 mm and corneal curvature of 43.40/44.43 D in the right eye and an AL of 29.3 mm with corneal curvature of 42.81/43.94 D in the left eye.

After dilation, with the patient in the supine position, 5 to 6 clock hours of zonular weakness were seen in the left eye (Figure 3). The right eye did not dilate well initially, which masked the underlying zonular weakness (Figure 4). However, injection of a dispersive OVD (Viscoat) through the paracentesis deepened the anterior chamber, enabling visualization of 8 to 9 clock hours of the lens edge (Figure 5). Both cataracts were removed as in Case 1, with complete cortical cleaving hydrodissection, cataract extraction by aspiration alone, and in-the-bag placement of the same CTR model followed by insertion of a 3-piece acrylic IOL (MN60MA +5.0 D, Alcon Laboratories, Inc.). After insertion of the CTRs, the edge of the lens was no longer visualized in either eye.

Figure 3.
Figure 3.:
After pupillary dilation, with patient in the supine position, 5 to 6 clock hours of zonular weakness was observable in the left eye.
Figure 4.
Figure 4.:
No observable zonular weakness in the right eye after dilation alone (inadequate pupillary dilation).
Figure 5.
Figure 5.:
Eight to 9 clock hours of the crystalline lens border were seen in the right eye after instillation of OVD showed underlying zonular weakness.

The intraoperative course was uneventful, with no vitreous loss or IOL dislocation in either eye. At the 6-month follow-up, the CDVA was 20/25 in the right eye and 20/40 in the left eye. Slitlamp examination was significant for trace pseudophacodonesis in both eyes. At 1 year, the CDVA had improved to 20/25 in both eyes. There was trace pseudophacodonesis in both eyes, but both IOLs remained centered on the visual axis.

DISCUSSION

Gyrate atrophy of the choroid and retina is a rare autosomal recessive metabolic disease characterized by mutations in the gene locus OAT on chromosome 10, leading to OAT deficiency and plasma hyperornithinemia.8 Initial clinical presentation includes a gradual onset of decreased visual acuity and impaired night vision.2 Ocular findings of gyrate atrophy include chorioretinal atrophy, high myopia, and early cataract development. All 3 ocular manifestations were evident in the 4 eyes of our 2 sibling patients, along with a previously unreported finding of concurrent zonular weakness. To our knowledge, no studies have noted an association between weak zonular fibers and gyrate atrophy.

Few reports describe the intraoperative and long-term postoperative course of cataracts in patients with gyrate atrophy.6,7 Kinori et al.7 reported a case of late-onset in-the-bag-dislocation 9 years after cataract extraction, which was attributed to excessive force on the zonular fibers from capsule contraction. Tsilou et al.6 described a case of bilateral spontaneous in-the-bag IOL dislocation several years after uneventful extracapsular cataract extraction, which was attributed to partial zonular rupture from extensive capsule fibrosis. Despite successful IOL repositioning, bilateral IOL exchange was required to correct intermittent blurred vision from pseudophacodonesis. Based on our 2 cases, we suspect that preoperative zonular weakness may have played a role in these cases. This mechanism is consistent with previous reports of spontaneous IOL dislocation in patients with no preexisting risk factors.9–11

Although the exact mechanism of zonular weakness in patients with gyrate atrophy is unknown, the cause may be multifactorial at an anatomic, structural, and functional level. Severe cases of high myopia can be associated with zonular weakness,12 and although high myopia has been documented in patients with gyrate atrophy,4,13,14 the extensive zonular weakness noted in our patients' eyes preoperatively suggests that an underlying metabolic etiology may also contribute to zonular compromise. Further histopathologic studies may be needed to confirm this speculation.

Zonular weakness in patients with gyrate atrophy provides a pathophysiologic mechanism for late in-the-bag IOL dislocations and can be crucial in preoperative cataract surgical planning. These patients may benefit from additional intraoperative precautions, including complete cortical cleaving hydrodissection of the lens from the capsular bag, minimal use of ultrasound, and, most important, a CTR to stabilize the capsular bag. All 4 eyes in our series received a CTR intraoperatively. One patient (Case 2) began to show trace pseudophacodonesis in both eyes at the 6-month follow-up, suggesting that late-onset in-the-bag IOL dislocation may occur despite a well-positioned CTR.

One retrospective analysis indicates that patients with a high AL and associated myopia were at increased risk for secondary dislocation of the IOL–CTR complex.15 Additionally, 1 study describes high AL as a significant risk factor for IOL dislocation, likely attributable to zonular weakening from elongation of the zonular fibers.16 Both of our patients exhibited high axial myopia (mean AL 29.7 mm). Consequently, these patients remain at high risk for further ocular complications and require close long-term follow-up.

In summary, we described 4 eyes with gyrate atrophy and extensive intraoperative zonular weakness, which was noted only when the eyes were dilated and the patients were in the supine position. This previously unreported physical finding can explain the association of late-onset in-the-bag IOL dislocation in gyrate atrophy patients. Awareness of this physical finding can aid cataract surgeons in surgical planning to minimize intraoperative and postoperative complications of zonular weakness in this challenging patient population.

Disclosure:

None of the authors has a financial or proprietary interest in any material or method mentioned.

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