Treatment of Cataracts

Treatment of Cataracts

Medical Treatment

In spite of theoretical approaches in animal research, the effectiveness of con-servative cataract treatment in humans has not been demonstrated.

At present there are no available conservative methods to prevent, delay, or reverse the development of a cataract. Galactosemic cataracts are the only exception to this rule.

Surgical Treatment

Cataract surgery is the most frequently performed procedure in ophthal-mology.

When is surgery indicated?

Earlier surgical techniques were dependent upon the maturity of the cataract.

This is no longer the case in modern cataract surgery.

❖ In the presence of bilateral cataracts, the eye with the worse visual acuity should undergo surgery when the patient feels visually handicapped.However, this threshold will vary depending on the patient’s occupational requirements.

❖ In the presence of a unilateral cataract, the patient is often inclined to postpone surgery as long as vision in the healthy eye is sufficient.

❖ In the presence of a mature cataract, it is important to advise the patient to undergo surgery as soon as possible.

Will the operation be successful?

The prospect of a successful outcome is important for the patient. Most patients define a successful outcome in terms of a significant improvement in vision. Therefore, it is important that the patient undergoes a thorough pre-operative eye examination to exclude any ocular disorders, aside from the cataract, that may worsen visual acuity and compromise the success of the cataract operation. Such disorders include uncontrolled glaucoma, uveitis, macular degeneration, retinal detachment, atrophy of the optic nerve, and amblyopia.

A detailed history of the patient’s other ocular disorders and vision prior to development of the cataract should be obtained before surgery.

Several methods aid in making a prognosis with respect to expected visualacuity (retinal resolution) following cataract surgery. These include:

❖ Retinoscopy to determine visual acuity.

❖ Evaluation of the choroid figure (in severe opacifications such as a maturecataract).

Reliability of cataract surgery

Cataract surgery is now performed as a microsurgical technique under an operating microscope. Modern techniques, microsurgical instruments, atrau-matic suture material (30 µm thin nylon suture thread), and specially trained surgeons have made it possible to successfully perform cataract surgery without serious complications in 98% of all patients. The procedure lasts about30 minutes and, like the postoperative phase, is painless.

Duration of hospitalization

The patient may be hospitalized for 3 days, depending on the adequacy of postoperative care at home. Older patients who live alone may be unable to care adequately for themselves and maintain the regime of prescribed medi-cations for the operated eye in the immediate postoperative phase. The operation may be performed as an outpatient procedure if the ophthalmolo-gist’s practice is able to ensure adequate care.

Possible types of anesthesia

Cataract extraction may be performed under local anesthesia or generalanesthesia. Today, most operations are performed under local anesthesia.Aside from the patient’s wishes, there are medical reasons for preferring one form of anesthesia over another:

General anesthesia: This is recommended for patients who are extremelyapprehensive and nervous, deaf, or mentally retarded; it is also indicated for patients with Parkinson’s disease or rheumatism, who are unable to lie still without pain.

Local anesthesia (retrobulbar, peribulbar, or topical anesthesia): This is rec-ommended for patients with increased anesthesia risks.

Preoperative consultation regarding options for achieving refractive correction (Table 7.4)

Intraocular lens: In 95 – 98% of all cataract extractions, an intraocular lens(IOL) is implanted in place of the natural lens (posterior chamber lens). An eye with an artificial lens is referred to as a pseudophakia. The power of the lens required is determined preoperatively by biometry. The IOL refractive power is determined by ultrasonic measurement of axis length, IOL refraction con-stants, and the refractive power of the cornea. There are two types of intraocular lenses:

❖ Monofocal IOLs.The patient can select whether the strength of the artifi-cial lens is suitable for distance vision or near vision.

❖ Bifocal or multifocal IOLs.These allow close and remote objects to appearin focus. However, it should be noted that bifocal and multifocal lenses do not achieve the optical imaging quality of monofocal lenses.

Cataract eyeglasses: The development of the intraocular lens has largelysupplanted correction of postoperative aphakia with cataract lenses. Long the standard, this method is now only necessary in exceptional cases. Cataract eye-glasses cannot be used for correcting unilateral aphakia because the differ-ence in the size of the retinal images is too great (aniseikonia). Therefore, cat-aract eyeglasses are only suitable for correcting bilateral aphakia. Cataract eyeglasses have the disadvantage of limiting the field of vision (peripheral and ring scotoma).

Contact lenses (soft, rigid, and oxygen-permeable): These lenses permit anear normal field of vision and are suitable for postoperative correction of uni-lateral cataracts as the difference in image size is negligible. However, manyolder patients have difficulty learning how to cope with contact lenses.

Surgical Techniques

The operation is performed on only one eye at a time. The procedure on the fellow eye is performed after about a week if once the first eye has stabilized.

Historical milestones:

❖Couching(reclination): For 2000 years until the 19 th century, a pointedinstrument was used to displace the lens into the vitreous body out of the visual axis.

❖ 1746: J. Daviel performed the first extracapsular cataract extraction byremoving the contents of the lens through an inferior approach.

❖ 1866: A. von Graefe performed the first removal of a cataract through a superior limbal incision with capsulotomy.

Intracapsular cataract extraction: Until the mid 1980s, this was the method ofchoice. Today intracapsular cataract extraction is used only with subluxationor dislocation of the lens. The entire lens is frozen in its capsule with a cryo-phake and removed from the eye through a large superior corneal incision (Fig. 7.17).

Extracapsular cataract extraction: Procedure(Figs. 7.18a – c): The anteriorcapsule is opened (capsulorrhexis). Then only the cortex and nucleus of the lens are removed (extracapsular extraction); the posterior capsule and zonule suspension remain intact. This provides a stable base for implanta-tion of the posterior chamber intraocular lens.

Extracapsular cataract extraction with implantation of a posterior chamber intraocular lens is now the method of choice.

Today phacoemulsification (emulsifying and aspirating the nucleus of the lens with a high-frequency ultrasonic needle) is the preferred technique for removing the nucleus. Where the nucleus is very hard, the entire nucleus is expressed or aspirated. Then the softer portions of the cortex are removed by suction with an aspirator/irrigator attachment in an aspiration/irrigation maneuver. The posterior capsule is then polished, and an intraocular lens (IOL) is implanted in the empty capsular bag (Fig. 7.19a and b). Phacoemulsi-fication and IOL implantation require an incision only 3 – 6 mm in length. Where a tunnel technique is used to make this incision, no suture will be nec-essary as the wound will close itself.

Advantages over intracapsular cataract extraction.Extracapsular cataractextraction usually does not achieve the same broad exposure of the retina that intracapsular cataract extraction does, particularly where a secondary cataract is present. However, the extracapsular cataract extraction maintains the integrity of the anterior and posterior chambers of the eye, and the vit-reous body cannot prolapse anteriorly as after intracapsular cataract extrac-tion. At 0.1 – 0.2%, the incidence of retinal detachment after extracapsular cat-aract extraction is about ten times less than after intracapsular cataract extraction, which has an incidence of 2 – 3%.

Secondary Cataract

Epidemiology: Approximately 30% of all cataract patients develop a second-ary cataract after extracapsular cataract extraction.

Etiology: Extracapsular cataract extraction removes only the anterior centralportion of the capsule and leaves epithelial cells of the lens intact along with remnants of the capsule. These epithelial cells are capable of reproducing and can produce a secondary cataract of fibrous or regenerative tissue in the pos-terior capsule that diminishes visual acuity (Fig. 7.20a).

Treatment: A neodymium:yttrium-aluminum-garnet (Nd:YAG) laser canincise the posterior capsule in the visual axis without requiring invasive eye surgery. This immediately improves vision (Fig. 7.20b).

Special Considerations in Cataract Surgery in Children

Observe changes in the child’s behavior: Children with congenital, trau-matic, or metabolic cataract will not necessarily communicate their visual impairment verbally. However, it can be diagnosed from these symptoms:

❖ Leukocoria.

❖ Oculodigital phenomenon: The child presses his or her finger against the eye or eyes because this can produce light patterns the child finds interest-ing.

❖ Strabismus: the first sign of visual impairment (Fig. 7.21). ❖The child cries when the normal eye is covered.

❖The child has difficulty walking or grasping. ❖Erratic eye movement is present.

❖ Nystagmus.

Operate as early as possible: Retinal fixation and cortical visual responsesdevelop within the first six months of life. This means that children who undergo surgery after the age of one year have significantly poorer chances of developing normal vision. 

Children with congenital cataract should undergo surgery as early as possible to avoid amblyopia. The prognosis for successful surgery is less favorable for unilateral cataracts than for bilateral cataracts. This is because the amblyopia of the cataract eye puts it at an irreversible disadvantage in comparison with the fellow eye as the child learns how to see.

Plan for the future when performing surgery: After opening the extremelyelastic anterior lens capsule, one can aspirate the soft infantile cortex and nucleus. Secondary cataracts are frequent complications in infants.

Therefore, the procedure should include a posterior capsulotomy with anterior vit-rectomy to ensure an unobstructed visual axis. The operation preserves the equatorial portions of the capsule to permit subsequent implantation of a pos-terior chamber intraocular lens in later years.

Refraction changes constantly: The refractive power of the eye changesdramatically within a short period of time as the eye grows. The refraction in the eye of a newborn is 30 – 35 diopters and drops to 15 – 25 diopters within the first year of life. Refractive compensation for a unilateral cataract is achieved with a soft contact lens (Fig. 7.22). The use of soft contact lenses in infants is difficult and requires the parents’ intensive cooperation. Refractive correction of bilateral cataracts is achieved with cataract eyeglasses.

Refraction should be evaluated by retinoscopy  every two months during the first year of life and every three to four months during the second year, and contact lenses and eyeglasses should be changed accordingly.

Implantation of posterior chamber intraocular lenses for congenital cata-ract is not yet recommended in children under three years of age. This is because experience with the posterior chamber intraocular lens and present follow-up periods are significantly less than the life expectancy of the children. In addition, there is no way to adapt the refractive power of the lens to changing refraction of the eye as the child grows.

Orthoptic postoperative therapy is required: Unilateral cataractsin partic-ular require orthoptic postoperative therapy in the operated eye to close the gap with respect to the normal fellow eye. Regular evaluation of retinal fixation is indicated, as is amblyopia treatment (see patching).