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Trauma also should be considered in all patients with a dislocated lens. Rarely, pseudoexfoliation can be a cause.

KEY POINTS: DISLOCATED AND SUBLUXATED LENSES

1.Patients with a natural lens that is dislocated should be evaluated for trauma.

2.Marfan’s syndrome most often causes lenses to dislocate superiorly. Patients need evaluation for possible cardiac and aortic abnormalities and retinal detachments.

3.Homocystinuria most often causes lenses to dislocate inferiorly. Patients have a high risk of thromboembolic events.

18.What other clinical findings are common in patients with a traumatic cataract?

Blunt trauma may produce a cataract. Patients often have associated sphincter tears and may even have iridodialysis or angle recession. If the trauma has been severe, some or all of the zonules may be broken, causing the lens to be mobile within the eye. This phenomenon is called phacodonesis. Retinal detachment and optic neuropathy also may be present and cause decreased vision.

19.What are the indications for cataract surgery?

The basic indication for cataract surgery is reduced visual function that interferes with activities of daily living. This indication obviously varies, depending on the patient’s age and degree of activity. For instance, a 40-year-old accountant with an early posterior subcapsular cataract may be much more symptomatic than an 85-year-old who no longer reads or drives. Cases in which cataract surgery is medically necessary (e.g., phacomorphic and phacolytic glaucoma) are extremely uncommon. Patients with cataracts should be informed that cataract surgery is almost always an elective procedure and that leaving the cataract alone will not hurt or damage the eye. However, it is important to be aware of state standards of Snellen visual acuity and visual field for driving vision and to inform patients accordingly. They can be found in the Physicians’ Desk Reference (PDR) for ophthalmic medicines.

20.Does a cataract need to be ‘‘ripe’’?

Many years ago, when cataract surgery was performed by removing the entire lens and leaving the patient aphakic, the cataract needed to be dense enough to remove in a single entire piece and to be causing sufficiently poor vision that the patient would benefit from cataract surgery.

Currently ‘‘ripeness’’ of the cataract is no longer a consideration. The indications for cataract surgery in general are functional visual difficulties secondary to the cataract, which are interfering with the patients day-to-day activities or overall quality of life. Typically if the patient has a Snellen visual acuity (or glare disability) that reduces their vision to 20/50 or worse, they may be considered candidates for cataract surgery.

21.What is aphakia? What are aphakic spectacles? What is pseudophakia?

Aphakia is the condition in which the patient’s natural lens (phakos) has been removed surgically, leaving the patient without a lens. This is the result of intracapsular surgery. Aphakic spectacles describe the heavy ‘‘coke bottle’’ glasses patients had to wear to achieve the needed focusing power of the eye with the natural lens missing. Pseudophakia or ‘‘artificial lens’’ is the term used to describe an eye with an intraocular lens (IOL).

22.How is the IOL power determined? What is the most commonly used IOL power?

The appropriate IOL power for a patient is determined by measuring the curvature of the patients cornea (keratometry values) as well as the length of the eye (axial length measurement). These

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two measurements are then utilized by multivariable ‘‘IOL power equations’’ to help determine the most appropriate lens for the individual patient.

The most commonly used IOL power is 18D.

23.What are multifocal IOLs? How do multifocal IOLs work?

With standard cataract surgery and conventional intraocular lens (IOL) there is only one fixed focal distance. Therefore, if a patient achieves good uncorrected distance vision following cataract surgery, they will not be able to see at near without correction because the artificial lens cannot accommodate to adjust its focal length the way a natural phakic lens can.

New technology multifocal IOLs now allow patients the ability to see both in the distance and up close. In the United States there are three Food and Drug Administration (FDA)-approved IOLs that achieve these results with different technologies: The crystal lens utilizes a thin small optic lens that is designed to flex and produce a degree of accommodation; the ReZoom lens

uses differing radii of curvature to create a zonal refractive lens to achieve its multifocality; and the ReSTOR lens uses a combination of refractive and diffractive optics to create multifocal images.

24.What is IFIS? What is a flomax pupil?

IFIS is an acronym for intraoperative floppy iris syndrome. This condition occurs in patients who are taking tamsulosin (Flomax) for benign prostatic hypertrophy. Tamsulosin is a systemic sympathetic a1-A receptor blocker, which improves lower urinary tract flow by relaxing the neck of the bladder neck and prostatic smooth muscle.

Patients taking tamsulosin who undergo cataract surgery manifest pupillary abnormalities that include a flaccid iris, which undulates and billows in response to intraocular fluid currents. There is also a tendency for the iris to prolapse through both the phaco incision and paracentesis. Last, there is typically a progressive intraoperative pupillary constriction despite apparent adequate pharmacologic dilation at the initiation of surgery. These iris abnormalities are believed to occur because the smooth muscle in the iris also has a1-adrenoreceptors that are affected by tamsulosin.

Because cataract surgery is more difficult in patients with poorly dilating pupils and abnormalities as noted above, cataract surgery on patients taking tamsulosin can be more difficult as well. Interestingly, even if patients discontinue their tamsulosin for up to 4 weeks prior to cataract surgery, the pupil abnormalities persist. Surgical strategies for dealing with this situation include utilizing a highly cohesive viscoelastic agent and iris retractors.

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25.What is the difference between an anterior chamber lens and a posterior chamber lens? What is ‘‘the capsular bag’’?

A posterior chamber lens is typically utilized in routine cataract surgery. During surgery a circular opening termed a capsulorrhexis is made in the capsule that surrounds the cataractous lens. The cataract is removed and then the new lens is placed into ‘‘the capsular bag,’’ which is the membrane that is left behind once the cataract is removed. This region of the eye is termed the posterior chamber, hence the IOL that resides there is termed a posterior chamber lens.

At times it is not possible to place a posterior chamber lens either because of inherent weakness in the capsular bag or an intraoperative complication that disrupts its integrity. In these cases one of the options is to place a lens in the front (or anterior) portion of the eye; hence the term anterior chamber lens. Anterior chamber lenses fixate in the eye by resting on the scleral spur. If not positioned correctly, these IOLs have the potential to chafe the sensitive uveal tissue in the iris and create complications.

26.What is posterior capsular opacification? What is a secondary membrane? Can a cataract grow back?

The new IOL replaces the cataractous lens by resting inside the capsular bag. Slowly, over time, residual epithelial cells in the capsular bag can grow across the posterior portion of the capsule

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and cause it to become hazy or cloudy. Over time, the capsule can become so cloudy it may seem as if the cataract has ‘‘come back.’’ The cataract can never come back, but the secondary membrane can become cloudy.

27.What is a YAG capsulotomy?

When the reduced vision becomes clinically significant, the patient may undergo a Nd:YAG capsulotomy. The initials are an acronym for neodymium, yttrium, aluminum, and garnet, which are the materials utilized to allow the laser to function properly and open the membrane.

28.What is the origin of the term laser?

Laser is actually an acronym for light amplification by stimulated emission of radiation.

29.What is the difference between an ‘‘intracap’’ and an ‘‘extracap?’’

An intracap describes intracapsular cataract extraction. This is the ‘‘old’’ type of cataract surgery back in the days when patients had a very large incision made at the corneoscleral limbus and the entire lens surrounded by the lens capsule was removed (usually with the aid of a freezing probe termed a cryoprobe). In these cases no lens was replaced and the patient was left aphakic.

In an extracap or extracapsular surgery, the capsule surrounding the lens is opened and the cataractous lens removed. The capsule, however, remains in the eye to support and hold the new posterior chamber IOL.

30.What is couching?

Couching describes an ancient technique for cataract surgery where a needle was inserted into the eye and used to push the opaque cataract back into the vitreous cavity. Although the complication rate of this is extremely high and the visual result limited, in antiquity it would allow patients with mature light perception cataracts to be able to regain a limited degree of vision.

BIBLIOGRAPHY

1.Datilles M: Clinical evaluation of cataracts. In Tasman W, Jaeger E (eds): Duane’s Clinical Ophthalmology, vol. 1. Philadelphia, Lippincott-Raven, 1996, pp 1–15.

2.Datilles M, Kinoshita J: Pathogenesis of cataracts. In Tasman W, Jaeger E (eds): Duane’s Clinical Ophthalmology, vol. 1. Philadelphia, Lippincott-Raven, 1996, pp 1–9.

3.Datilles M, Magno B: Cataract: Clinical types. In Tasman W, Jaeger E (eds): Duane’s Clinical Ophthalmology, vol. 1. Phildelphia, Lippincott-Raven, 1996, pp 1–25.