Cataracts, (the white‐water rapids of the Nile), prevented potential invasions, but also kept the Egyptians from going very far. Fig 427 Slit lamp view of lens: A, cornea; B, anterior capsule; C, nucleus; D, posterior cortex; E, posterior capsule. Source: Courtesy of Takashi Fujkado, MD. A cataract is a cloudy lens that blocks and scatters the light passing through it, and it occurs in everyone to some degree with aging. It should be suspected especially when elderly patients complain of blurry vision and glare. One sign is that it causes a hazy view of the retina with an ophthalmoscope. The lens consists of an outside capsule surrounding a soft cortical substance and a hard inner nucleus (Fig. 427). The diagnosis is confirmed with a slit lamp and described in the following ways. Fig 428 Anterior cortical spokes. Fig 429 Posterior subcapsular cataract. Fig 430 Congenital (zonular) cataract surrounded by clear cortex. Fig 431 Brunescent (brown) cataract. A cataract raises two questions. Is it responsible for the decreased vision? Is it ripe? Ripe is the layperson’s term for whether surgery is indicated. In most cases, a surgeon waits for a reduction in vision to 20/40 or worse. It is the number one surgery in the USA and worldwide. Indications vary with the patient’s needs. Surgery is usually elective except in the rare cases of a mature lens that might rupture (Figs 422, 430, and 432), or with a dislocated lens in imminent danger of dropping into the vitreous or anterior chamber. Lens dislocation (Figs 432 and 433) is due to a rupture of the zonules. It may occur with trauma (Fig. 234) or may be associated with pseudoexfoliation (Fig. 368), Marfan’s disease, homocystinuria, or syphilis. Fig 432 Mature lens dislocated into the anterior chamber, obscuring pupil and iris. Fig 433 Superiorly dislocated lens. The surgery is performed as an outpatient procedure using local anesthesia. Xylocaine may be injected into the orbit (Fig. 236) or into the anterior chamber. The 10‐mm lens may be removed through a 3‐mm incision by breaking it up with a phacoemulsifier. The cornea is entered with a blade or laser, making a tunnel incision to minimize chance of leakage and the need for sutures (Fig. 434). If testing of the wound shows leakage, sutures may be used. Iris may prolapse into gaping wound (Fig. 435) and hypotony may cause folds in the cornea called stria (Fig. 267), choroidal effusions (Fig. 351) and macular edema (Fig. 350). Fig 434 A three‐plane corneal incision for entering the eye during cataract surgery. Blade A is guarded to create a uniform mid‐depth incision approximately 3–6 mm in length. Blade B is crescent shaped for a 4‐mm dissection of corneal lamellae. A downward motion with the keratome (blade C) enters the anterior chamber. A watertight closure is critical to prevent fluid egress or ingress as the incision is getting smaller. There is an increase in preference for one‐ or two‐plane incisions. Fig 435 Iris prolapse into gaping wound causing superiorly peaked pupil. Source: Courtesy of Eyerounds.org., Univ. of Iowa. Fig 436 Laser or manual continuous tear capsulotomy (capsulorrhexis). Trypan blue dye may be used to stain this capsule when it is difficult to see. The anterior lens capsule is then removed (Fig. 436). The majority of the time a laser or continuous tear capsulotomy, called capsulorrhexis, is used, or needle punctures to complete an aborted attempt (Fig. 437) at a 360° tear. The hard nucleus is rarely extracted in one piece (Fig. 441). To facilitate removal of the nucleus through a small wound, it is fragmented with a phacoemulsifier, which has a tip that vibrates 40,000 times per second (Fig. 438). (Phaco‐ is a prefix referring to the lens.) Phacoemulsification’s disadvantage is that it requires a lot of energy to liquefy a hard nucleus. This could damage the corneal endothelium or the delicate posterior lens capsule, and the risk may be minimized by initially using a laser to partially breakup the hard nucleus (Fig. 447).
Chapter 9
Cataracts
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