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Subtle signs of zonular damage

Marques, Daniela M.V MDa,b; Marques, Frederico F MDa,b; Osher, Robert H MD*,a,c

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Journal of Cataract & Refractive Surgery: June 2004 - Volume 30 - Issue 6 - p 1295-1299
doi: 10.1016/j.jcrs.2003.09.071
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Signs of zonular damage should be sought in every patient, especially when there is a history of ocular trauma, pseudoexfoliation syndrome, or systemic abnormalities associated with zonular weakness (Marfan's syndrome, Weill-Marchesani syndrome, homocystinuria).1–4 Obvious signs such as phacodonesis, iridodonesis, vitreous prolapse, and lens subluxation are not always present, however, and a loose cataract can be easily overlooked, with severe surgical consequences. We describe 5 subtle signs that, if detected during the preoperative examination, can warn the surgeon of zonular weakness.

Case Reports

Case 1

A 47-year-old woman was referred with a chief complaint of a gradual bilateral vision reduction. She was also bothered by daytime glare. Family history was positive for Marfan's syndrome in her brother and her mother.

Examination revealed visual acuity measuring 20/400 in the right eye and 20/40 in the left eye. Biomicroscopy revealed advanced nuclear sclerosis with extensive posterior subcapsular opacification in the right lens. A mild superior subluxation with visible zonules between 5 and 8 o'clock was evident in the primary position. The left lens showed moderate axial posterior subcapsular opacification and appeared in the normal position through a pupil that dilated to 7 mm. The posterior subcapsular opacity, however, appeared a bit superior to the visual axis. Therefore, the patient was asked to look down, and the inferior lens equator was visible in extreme downgaze. Phacodonesis was absent, and the remainder of the evaluation was unremarkable.

Cataract surgery was performed in the right eye using slow-motion phacoemulsification and a Morcher modified capsular tension ring (MCTR). The intraocular lens (IOL) was placed in the capsular bag after the ring was sutured through the sclera beneath a flap. Postoperative visual acuity was 20/20.

Two years later, the patient's left eye vision had deteriorated to 20/200, consistent with advanced nuclear sclerosis and extensive posterior subcapsular opacification. It was easier to identify slight upward decentration of the nucleus, although the lens equator was invisible in the primary position and evident only in extreme downgaze (Figure 1, A and B). A similar surgical procedure was performed using a MCTR followed by implantation of a +12.00 diopter foldable acrylic IOL in the capsular bag. No complications were encountered, and the patient's postoperative uncorrected visual acuity was 20/20.

Figure 1.
Figure 1.:
(Marques) A: The lens equator was not visible in the primary position. B: White arrows show the lens equator in extreme downgaze.

Case 2

A 75-year-old man was referred with a 10-year history of blunt trauma, acquired when he was struck in his left eye with a fist. At the time of the injury, he recalled a transient loss of 25% of his vision, which spontaneously cleared, although his pupil remained larger. The vision in the involved eye gradually deteriorated, and he complained of faulty depth perception and glare.

Examination revealed visual acuity of 20/20 in his right eye and 20/200 in his left eye. The right pupil diameter measured 3 mm; the left pupil was 7 mm in diameter and unreactive to light. Biomicroscopy revealed a brunescent nuclear cataract with diffuse posterior subcapsular opacification. Atrophy of the pupillary ruff was present. Although phacodonesis was absent, a subtle superior displacement of the nucleus was present in the primary position of gaze (Figure 2). Gonioscopy revealed an angle recession, and there was no view of the fundus. Intraocular pressure (IOP) was normal in each eye.

Figure 2.
Figure 2.:
(Marques) Subtle superior displacement of the nucleus in the primary gaze position is seen.

Cataract surgery was complicated by a tear in the loose anterior capsule. The lens was removed by phacoemulsification, and a posterior chamber IOL was sewn into the ciliary sulcus. The traumatic mydriasis was corrected by a pupilloplasty. Intraocular pressure was elevated during the early postoperative course. This was managed by medical therapy, and postoperative visual acuity was 20/20.

Case 3

A 32-year-old man was referred with chief complaints of a gradual reduction of vision in his left eye and severe glare. He had been involved in an automobile accident the previous year in which an air bag had deployed, causing bilateral retinal hemorrhages, a damaged left iris with a large pupil, mild hyphema, and transient elevation of IOP. The referring ophthalmologist prescribed pilocarpine 1% twice daily for the traumatic mydriasis and prednisolone acetate 1% (Pred Forte®) twice daily for occasional flare-ups of iritis.

Examination revealed visual acuity of 20/20 in the right eye and 20/40 in the left eye. Glare further reduced the acuity to 20/70 in both eyes. The undilated left pupil measured 5 × 7 mm and was unreactive to light. Biomicroscopy revealed a fibrotic callous on the central anterior capsule and a diffuse posterior subcapsular cataract. The iris stroma was atrophic for 3 clock hours temporally, with both sphincter damage and retroillumination defects. A gap was present between the inferotemporal pupillary border and the anterior capsule, which did not exist in the other quadrants (Figure 3, A–C). Phacodonesis was absent, and IOP was normal. Each fundus showed healthy optic nerves with 0.2 cupping, and gonioscopy revealed heavy pigmentation in the inferior angle.

Figure 3.
Figure 3.:
(Marques) Top: White arrows show the gap between the inferotemporal iris border and the anterior lens capsule. Middle: Diagram shows the gap between the iris and the anterior capsule. Bottom: Normal lens position shows the relationship between the iris border and the adjacent anterior lens capsule.

The surgery was characterized by a difficult capsulorhexis because of inferotemporal zonular weakness. Phacoemulsification was performed with low parameters and low infusion. Cortical removal was facilitated by the injection of a viscoelastic agent, cleaving the cortex from the loose capsular bag inferiorly. Two Morcher Model 96G segmental prosthetic iris devices were implanted temporally and inferiorly, serving to reexpand the capsular bag and fill the retroillumination defects. A partial pupillary cerclage reduced the size of the pupil after a +18.5 diopter, single-piece, SA60AT acrylic IOL was implanted in the capsular bag.

The postoperative course was uneventful, and uncorrected visual acuity improved to 20/25 with a marked reduction in glare. Intraocular pressure remained normal, and a mild epiretinal membrane was identified, which was not visualized before surgery.

Case 4

A 64-year-old man gradually lost sight in his right eye 3 decades after severe ocular trauma. A penetrating injury had resulted in a corneal laceration, iris prolapse, and an iridodialysis. Examination revealed a best corrected visual acuity of 20/50 in the right eye and 20/20 in the left eye.

Biomicroscopy of the right anterior segment disclosed a peripheral corneal scar with iris incarceration. The pupil was updrawn into the laceration site, and a large temporal iridodialysis revealed subtle zonular loss through which minimal vitreous herniation was present. The cataract was characterized by anterior cortical opacification, moderate fetal nuclear sclerosis, and extensive posterior subcapsular opacification. A “bite” out of the visible perimeter of the lens was present (Figure 4). No phacodonesis was observed.

Figure 4.
Figure 4.:
(Marques) Slitlamp photograph demonstrates the altered contour of the lens equator.

Gonioscopy confirmed the iris incarceration as well as the subtle vitreous within the zonula. Intraocular pressure measured 22 mm Hg in the right eye and 16 mm Hg in the left eye; fundus examination was unremarkable.

Case 5

A 58-year-old man with a history of severe trauma to his left eye was referred for cataract surgery. Examination revealed that visual acuity was reduced to 20/60, consistent with a nuclear cataract. Biomicroscopy disclosed focal temporal iridodonesis and a pupil that dilated to 5 × 6 mm, and there was a suggestion that the nucleus was slightly decentered. Vitreous prolapse, phacodonesis, and the edge of the lens were not visible (Figure 5, A).

Figure 5.
Figure 5.:
(Marques) A: Slitlamp photograph shows no lens subluxation despite subtle focal temporal iridodonesis. B: Operative view shows temporal lens equator with zonular dialysis.

In the operating room, more vigorous dilation was achieved with phenylephrine hydrochloride 10% (Neo-Synephrine®) and cyclopentolate hydrochloride 1% (Cyclogyl®). The pupil dilated to 7 mm, revealing the temporal equator of the lens (Figure 5, B). Slow-motion phacoemulsification with low parameters was performed, followed by implantation of a Morcher capsular tension ring (CTR) and injection of a single-piece acrylic IOL. Vitreous herniation into the anterior chamber occurred, and kenalog was injected to facilitate visualization. A bimanual anterior vitrectomy was accomplished by placing the automated cutter through the pars plana while infusion was established through the second stab incision.

The postoperative course was uneventful, and visual acuity was 20/20 with minimal refractive error.

Discussion

During the past decade, we have seen many improvements in the intraoperative management of traumatic and congenital zonular weakness since Osher presented a controversial series demonstrating the efficacy of phacoemulsification for the loose lens in 1987 (R.H. Osher, MD, “Update of Extracapsular and Phacoemulsification Techniques: Phacoemulsification of the Loose Cataract,” presented as a course at the ASCRS Symposium of Cataract, IOL and Refractive Surgery, Orlando, Florida, USA, May 1987). Low parameter techniques for zonular dialysis were published.5 In 1993, Legler et al. introduced the Morcher CTR to provide intraoperative and postoperative stabilization of the capsular bag and IOL (U. Legler, MD, et al., “The Capsular Ring: A New Device for Complicated Cataract Surgery,” video presented at the 3rd American-International Congress on Cataract, IOL and Refractive Surgery, Seattle, Washington, USA, May 1993). In 1995, Cionni and Osher described the use of the CTR in patients with severe zonular compromise or lens subluxation,6 followed in 1998 by the report of their expanded series using the MCTR.7

It must be recognized that the outcome of cataract surgery performed in the eye with zonular damage depends on preparedness. The slow-motion phacoemulsification technique using reduced fluidics initially described by Osher is effective in gently removing the cataract with minimal stress to the zonular apparatus. Moreover, at the time this manuscript was submitted, the CTR and the MCTR were not approved in the United States and require extra effort to obtain. Therefore, if the surgeon is not anticipating defective zonules, he or she may select an approach that is more likely to result in intraoperative complications, and a CTR may be unavailable. Hence, it is critical to make the initial diagnosis of zonular dialysis in the office rather than in the operating room.

The signs of zonular dialysis vary from subtle to obvious. Diagnosis becomes even more challenging to establish and can be easily overlooked when the history is unremarkable and the examination fails to reveal evidence of phacodonesis, iridodonesis, vitreous prolapse, or severe lens subluxation. We have observed several signs in multiple patients that have provided advance warning that the zonules compromised. The presence of a gap between the iris border and the anterior surface of the crystalline lens may signify focal zonular loss, which has caused a slight posterior lens tilting (microsubluxation). This is best identified by observing the distance between the iris border and the adjacent lens capsule as the slit beam passes across the anterior segment.

The cross-sectional anatomy of the lens, especially the nucleus, may also appear decentered, which is only significant when the patient's eye is in the primary position. Focal zonular loss may alter the usual symmetry of forces applied to the lens, resulting in a subtle but abnormal shift of the lens away from the area of zonular compromise. This finding is best detected by observing the position of the fetal nucleus in every patient with a cataract to establish a comparative frame of reference for the examiner.

Focal iridodonesis is caused by the lack of a barrier and stabilizing effect that the zonules provide. The vitreous is able to occupy the space immediately behind the iris. Any eye movement is associated with quivering of the vitreous gel, which makes the overlying iris appear to shimmer.

Another sign of zonular weakness is the visibility of the lens equator when the patient's gaze is eccentric. This finding represents a microluxation and can be missed if the examiner observes the lens anatomy in the primary position only. Changes in the contour of the peripheral lens may also indicate a loss of zonular tension on the equator. A focal zonular loss may allow the elastic forces of the capsule to retract, taking a bite out of the lens. A sector of zonular loss will create a corresponding flattening of the lens equator.

In summary, the surgical approach to the eye with zonular weakness has greatly improved but requires several critical modifications in both technique and technology. Therefore, preoperative detection of compromised zonules is essential to optimize the outcome. The identification of subtle but important signs including the iridolenticular gap, the decentered nucleus in the primary position, focal iridodonesis, an altered contour of the lens equator, or the visualization of the lens equator during eccentric gaze will better prepare the surgeon for an often challenging but highly rewarding operative procedure.

References

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© 2004 by Lippincott Williams & Wilkins, Inc.