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15.1 ACQUIRED CATARACT

Symptoms

Slowly progressive visual loss or blurring, usually over months to years, affecting one or both eyes. Glare,particularly from oncoming headlights while driving at night, and reduced color perception may occur, but notto the same degree of dyschromotopsia as can occur with optic neuropathies. The particular symptoms arebased on the location and density of the lens opacity.

Critical Sign

Opacification of the normally clear crystalline lens (see the respective types).

Other Signs

The retina often appears indistinct on funduscopic examination, and the dilated red reflex may be dim onretinoscopy. A direct ophthalmoscope at distances of 3 to 5 feet also may show a decreased red reflex or thehardened nucleus or cortical spokes on retroillumination. The patient may be found to be more myopic thanpreviously noted (so-called second sight). A cataract alone does not cause a relative afferent pupillarydefect.

Types of Cataracts

Nuclear: Yellow or brown discoloration of the central part of the lens on slit-lamp examination. Typically blursdistance vision more than near vision.Posterior subcapsular: Opacities appear near the posterior aspect of the lens, often forming a plaque. Theyare best seen in retroillumination against a red fundus reflex. Glare and difficulty reading are commoncomplaints. May be associated with ocular inflammation, prolonged steroid use, diabetes, trauma, orradiation. Classically occurs in patients younger than 50 years.Cortical: Radial or spoke-like opacities in the lens periphery that expand to involve the anterior and posteriorlens. Often asymptomatic until the changes develop centrally.

Note A mature cataract is defined as anterior cortical changes sufficiently dense to obscure totally the viewof the posterior lens and posterior segment of the eye.

Etiology

Age-related

Trauma (Ocular or head contusion, electrocution, others.)

Toxic [Steroids, anticholinesterases, antipsychotics (e.g., phenothiazines), others.]

Intraocular inflammation (e.g., uveitis)

Radiation

Intraocular tumor (A ciliary body malignant melanoma may produce a sector cortical cataract.)

Degenerative ocular disease (e.g., retinitis pigmentosa)

Systemic disease:1. Diabetes (The juvenile form is characterized by white snowflake opacities in the anterior and

posterior subcapsular locations. It often progresses rapidly. Adults develop age-related cataracts as

described previously, but at an earlier age.)2. Hypocalcemia (Small, white, iridescent cortical changes, usually seen in the presence of tetany.)3. Wilsons disease [Redbrown pigment deposition in the cortex beneath the anterior capsule (a

sunflower cataract). Seen with a corneal KayserFleischer ring.]4. Myotonic dystrophy (Multicolored opacities cause a Christmas-tree cataract behind the anterior

capsule.)5. Others (e.g., Downs syndrome, atopic dermatitis)

Workup

Determine the etiology, whether the cataract is responsible for the decreased vision, and whether surgicalremoval would improve vision.

1. History: Medications? Systemic diseases? Trauma? Ocular disease or poor vision in youth or youngadulthood (before the cataract)?

2. Complete ocular examination, including distance and near vision, pupillary examination, and refraction. Adilated slit-lamp examination by using both direct and retroillumination techniques is usually required to

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view the cataract properly. Fundus examination, concentrating on the macula, is essential in ruling outother causes of decreased vision. It is helpful for preoperative planning to note the degree of pupildilation, density of the cataract, and presence or absence of pseudoexfoliation syndrome orphacodonesis.

3. B-scan ultrasound when the fundus is obscured by a dense cataract to rule out posterior-segmentpathology.

4. The potential acuity meter or laser interferometry can be used to estimate the visual potential whencataract extraction is being considered in an eye with posterior segment pathology.

Note Laser interferometry and the potential acuity meter (PAM) often overestimate the eyes visual potential

in the presence of macular holes or macular pigment epithelial detachments. Interferometry also makes anoverprediction of results in cases of amblyopia. Near vision is often the most accurate manner of evaluatingmacular function if the cataract is not too dense. Nonetheless, both laser inferometry and PAM are usefulclinical tools.

1. When surgery is planned, keratometry readings and an A-scan ultrasound measurement of axial lengthare required for determining the power of the desired intraocular lens. An evaluation of the cornealendothelium, usually done at the slit lamp but occasionally requiring an endothelial cell count, is alsoneeded.

Treatment

Cataract surgery may be performed for the following reasons:

a. To improve visual function in patients with symptomatic visual disability.b. As surgical therapy for ocular disease (e.g., lens-related glaucoma or uveitis).c. To facilitate management of ocular disease (e.g., to monitor or treat diabetic retinopathy or

glaucoma).

Correct any refractive error if the patient declines cataract surgery.

A trial of mydriasis (e.g., scopolamine, 0.25%, daily) may be used successfully in some patients if thepatient desires nonsurgical treatment. The benefits of this therapy are only temporary.

Follow-up

Unless there is a secondary complication from the cataract (e.g., glaucoma; quite rare), a cataract itself doesnot require urgent action. Patients who decline surgical removal are reexamined yearly, and sooner if thereis a symptomatic decrease in visual acuity.

If congenital, see Congenital Cataract, Section 9.7.