Ординатура / Офтальмология / Английские материалы / The Art and the Science of Cataract Surgery_Boyd, Barraquer_2000

order to dilate small pupils (Figs. 205 and 196) except that the retractors are placed in the margins of the anterior capsulotomy instead of the margins of the pupil.

3)During disassembling of the nucleus, maneuvers to rotate the nucleus should be reduced to a minimum. In order to prevent the need for these maneuvers, hydrodissection and hydrodelamination should done carefully but thoroughly.

4)Padilha recommends that the intracapsular tension ring be introduced after

other very important measure to provide support to the capsular bag. Usually the ring is held by a long Kelman-McPherson forceps and introduced clockwise. When operating on the right eye using a superior sclerocorneal tunnel incision, the ring is moved 1 hour in the direction of 3 o’clock and 6 o’clock. A spatula—preferably Koch’s spatula—is used to facilitate the insertion of the ring in the correct position inside the bag. These rings come in different sizes. They are produced by Morcher GmbH, Germany, and Corneal, France, and will be commercially available through Alcon in the near future.

If an accidental cataract subluxation occurs during a conventional cataract surgery, the surgery must be interrupted and the ring should be introduced as described above. In these cases, Padilha prefers to implant a one-piece intraocular lens, all PMMA, inside the capsular bag and to make its length coincide with the meridian where the zonular rupture occurred.

Increasing the Safety of

Posterior Lens Implantation in

Extensive Zonular Disinsertion

In those cases where a more extensive zonular disinsertion is present, it is important to create safer conditions to implant a lens in the posterior chamber. Variations and constant improvements of this technique have been presented at various meetings and publications by many authors, especially Drs. Jorge Villar-Kuri, from Mexico, Robert Osher, from the United States, Yoshihiro Tokuda, from Japan, Charlotta Zetterstrom, from Sweden, among others.

Some guidelines are basic and very important in these extreme situations, including cases of Marfan’s syndrome. The surgeon should always opt for a small capsulorhexis using a bent needle, and carry out the hydrodissection very carefully.

Padilha considers there are at least three options in order to increase the safety of the posterior chamber lens implantation. The first consists in totally removing the capsular bag following removal of the cataract. This could be indicated in certain situations where the lens is too dislocated either superiorly or inferiorly, and vitreous loss is present. Following a generous anterior vitrectomy using an automated vitrector, the intraocular lens is sutured to the sclera, (Fig. 156).

Fixation of the Anterior Capsule to the Ciliary Sulcus

The second option to increase the safety of the posterior lens implantation and to prevent it from dislocating is to actually suture the anterior capsule to the ciliary sulcus. This is done so that when the IOL is sutured and implanted, it will remain in place.

This technique involves making two incisions in the anterior capsule, through the small CCC (Fig. 206), as in the intercapsular technique advocated some years ago by Sourdille and Galand. The borders of the free edge of the capsule should be folded and sutured to the sclera at the opposite side of the luxation, as suggested by Villar-Kuri . The step-by- step technique is shown in Figs. 206-210.

Figure 209 (center): Subluxated Cataracts - Fixation of the Anterior Capsule to the Ciliary Sulcus - Stage 4

The suture is used to pull up the anterior capsule (C) to the inferior scleral bed (S). The knot is buried inside the sclera, closing the scleral flap (F) with a 10-0 nylon suture (N).

T H E A R T A N D THE S C I E N C E OF C ATA R A C T S U R G E R Y

Figure 208 (above): Subluxated Cataracts - Fixation of the Anterior Capsule to the Ciliary Sulcus - Stage 3

Viscoelastic is reinjected in the anterior chamber. Through an inferior triangular scleral flap (F), 2.0 mm from the limbus, the surgeon introduces a straight, long, 25 gauge needle (N), emerging through the primary incision (M), with its bevel up. Into its bore the surgeon inserts the C7 needle (magnified inset), and slowly pulls the long needle until it goes out of the globe through the inferior scleral flap.

Figure 210 (below): Subluxated Cataracts - Fixation of the Anterior Capsule to the Ciliary Sulcus - Last Stage

At this point the anterior capsule (C) is fixed to the ciliary sulcus to permit more space and safety for the IOL insertion. Finally, the IOL of the surgeon’s choice (L) is implanted, placing it in a position perpendicular to the disinsertion. The primary incision is closed with a horizontal 10-0 nylon suture (N).

Previous Controversies Now

Resolved

Cataract surgery in the pediatric patient and the post op management of these children is still a complex problem, but significantly less than up to five years ago. The difficult controversies previously existing regarding finding solutions for their visual recovery have been solved in most cases. These controversies are:

1) Age and Timing for Surgery

Bilateral Cataracts

It is now generally agreed that early cataract surgery in bilateral cataracts and immediate optical correction can prevent otherwise irreversible deprivation amblyopia in the child born with dense cataracts. Unless this is done, children with bilateral cataracts who undergo surgery later in childhood or in their teens recover only limited visual acuity, usually an average of no better than 20/60. Optimum optical correction following surgery is more effectively done today with IOL implantation.

In infants with bilateral cataracts, despite an increased complication rate, surgery must be performed within the first months of age to avoid irreversible amblyopia.

Cataract surgery in children over the age of 1 year is less complex with a higher success rate and with fewer complications in the postoperative period. It is best to perform surgery in both eyes at the same «sitting». Sterility must be maintained during the whole

procedure in bilateral cases. This requires changing all instruments and sterile clothing of the surgeon, nurse and patient between eyes. Patching is not indicated. General anesthesia is used in all cases.

Unilateral Cataracts

Unilateral congenital cataract presents a more challenging problem, since even a mild cataract will cause irreversible deep amblyopia in one eye if not treated. Treatment is based on surgery within two months of life, prompt optical correction with intraocular lens implantation and aggressive occlusion therapy with frequent follow-up have been successful in several series.

Preconditions to be Met for Useful Vision

In cases of unilateral cataracts, if cataract surgery with IOL implantation is not done very early in life, the chances of achieving good vision are slim. It is possible to achieve useful vision in some children with monocular congenital cataracts provided certain important preconditions are met. The most important is the age at which the surgery is undertaken along with equally important immediate optical correction and occlusion therapy as emphasized by Noel Rice, M.D. at Moorfields Eye Hospital in London and

Eugene Helveston, M.D. in the U.S. years ago. These preconditions continue to be valid. It is essential first to provide a focused image and second, eliminate suppression.

This «triumverate» or «troika» of treatment is the key to success. To a great

extent, the ophthalmologist depends on other professionals who determine when the cataract is identified and referral takes place. If the child does not present to the ophthalmologist within the optimal period for surgery and optical rehabilitation, clearly the ophthalmic surgeon is considerably constrained in the quality of care he/she can provide. Timing is absolutely the key. If the surgeon decides to operate on a unilateral cataract, the family needs to expect the very high likelihood of only a helper eye, and not an eye that will have very good vision. It is important to acknowledge this limitation.

Role of Parents

Their role is absolutely essential for achieving a good result. The surgeon would be wise to take this factor into consideration before undertaking treatment. Parents who do not understand what they and the child need to go through for pre and postoperative management to prevent and «conquer» amblyopia, become the first contraindication to surgery. This is particularly important in unilateral cataracts in which prolonged amblyopia treatment is essential.

Importance of Asymmetrical

Visual Input

The period of sensitivity of the visual system and its responsiveness to the development of vision through having a good visual input in humans is still not precisely determined, but we know that it is most responsive during early infancy, and it falls off rapidly during the first year of life. The clinical research made by Rice at Moorfields and Von Noorden in the U.S. determined

that the implications of asymmetrical input into the visual system are vitally important, particularly in relation to unilateral congenital cataracts.

When Should We Not Operate?

Any unilateral lenticular opacity that is moderately severe will cause amblyopia. If management as here described is not possible very early in life, it may be best if we advise against it. Very mild unilateral lenticular opacity, may be best left alone. Removing a small unilateral cataract that causes a small degree of amblyopia creates aphakia, which may lead to even more amblyopia, unless we implant the adequate IOL and undertake aggressive occlusion therapy.

Preoperative Evaluation

History

In the workup of a child with cataract, a detailed history is necessary. It is important to determine whether the cataract is progressive, particularly in older children. Contrary to some earlier teaching, we now know that bilateral cataracts are often progressive. Frequently, in children from ages 3 to 6 and even of high school age, vision is gradually diminished bilaterally because of progressive congenital cataracts.

As pointed out by Charlotta Zetterstrom, M.D., PhD, of Stockholm, Sweden, in a clinically healthy child, an extensive preoperative evaluation to establish the cause for the cataract is not routinely necessary. Congenital cataracts are frequently inherited as an autosomal dominant trait but a recessive inheritance also occurs.

It is important, to rule out metabolic disorders, genetically transmitted syndromes, intrauterine infections and ocular conditions with associated anomalies.

Examination

The workup of the congenital cataract patient continues with the office examination. Infants with congenital cataracts generally resist having their eyes examined, and do not cooperate with the examining physician. This causes considerable stress in the family. The ophthalmologist must use special examination techniques. First, the light should be turned down to low levels of illumination, which causes the eyes to open immediately. Direct illumination is used to determine the extent of the opacity.

The red reflex should first be determined by direct ophthalmoscopy with the pupil undilated. The cataract is often most dense in the central part of the lens and after dilatation it seems to be less significant. While the newborn child is awake it is also important to assess visual function, if possible, with a Teller acuity card. Watch for the ability to fix and follow with an object that attracts attention. Clarify with the parents whether they have had any visual interaction with the child.

Children with significant bilateral congenital cataracts may seem to have delayed development as well as obviously impaired visual behavior. Children with monocular cataracts often present with strabismus, which however may not develop until severe irreparable visual loss has occurred. Children with monocular cataract are almost always detected much later than cases with bilateral cataract. The presence of nystagmus

at the age of 2-3 months generally indicates a poor visual prognosis.

Complete examination of infants with dilated pupils often requires sedation or general anesthesia and can be performed during the same anesthesia as the surgery although, if possible, days before surgery, so that the surgeon can be better informed to enable him/her to make adequate decisions, and to inform the parents properly.

Measurement of the corneal diameter, intraocular pressure using a handheld tonometer, type and density of the cataract by photography, are all part of a good examination in these patients. Zetterstrom emphasizes that when the clarity of the media permits, indirect ophthalmoscopy may reveal persistent fetal vessels or other posterior segment abnormalities that may have an impact on the visual outcome. A-scan measurement of the axial length, and keratometer readings are done. These are essential measurements for contact lens and IOL power calculation. Newborn eyes with congenital cataract are shorter and have a smaller corneal diameter compared to controls (Fig. 31 and text pages 54-56).

A B-scan ultrasound is also performed in cases in which visualization of the retina is impossible, in order to determine whether there are retinal abnormalities, masses, or the presence of hypoplastic primary vitreous. Helveston considers it important to determine the intraocular pressure because there is a significant relationship between reduced corneal diameter, intraocular pressure, and the presence of glaucoma. One of the most serious problems in the management of congenital cataracts, particularly bilateral congenital cataracts, is the glaucoma that may occur 5 to 10 years after successful cataract

surgery treatment. This glaucoma resembles chronic simple glaucoma in the adult patient. While the intraocular pressure may show only a modest increase, glaucoma in children can be extremely resistant to successful treatment. If not controlled, it can cause the same type of atrophy in the optic nerve that occurs in chronic simple glaucoma.

The Special Case of Lamellar

Cataracts

Saunders, the founder of Moorfield’s Eye Hospital, determined 200 years ago that lamellar cataracts often do not interfere at all or at a rather insignificant level with visual development. The lamellar cataract looks central and quite dense on retroillumination, but is revealed under slit-lamp illumination as definitely lamellar. Children with lamellar cataracts usually achieve very good vision if these cataracts are operated on much later in life, even late in childhood or the teens or twenties. Patients do not usually develop nystagmus and often achieve normal or near normal vision. The corollary is that there is no need to operate on these children in early infancy. The prognosis is better if operated when older, when visual development is complete. An accurate calculation of IOL power can be made, with a better visual result.

In his clinical research, Rice observed that in many children with lamellar cataracts, if ophthalmoscopy is undertaken even with a reasonably dilated pupil, the view of the fundus is often extremely obscured; in fact, there may not even be any red reflex. If eyes are examined fully, however, it can always be seen that there is clear cortex. If there is a reasonable view of the peripheral fundus

through the peripheral lens, there is no indication for precipitous and early surgery. Such cases can be treated very conservatively.

These patients often have vision sufficiently reduced in primary and early secondary school years to benefit from cataract removal and IOL implantation between ages 5 and 15 or even a little earlier.

Rubella Cataracts

These cataracts used to be an important source of blindness. Rubella cataracts tend to be bilateral and progressive and result in a membranous type of partially resolved cataract, posterior synechiae, and chronic uveitis. For the past 25 years, since rubella immunization has been available, rubella cataracts have been virtually nonexistent. The key point in managing these rubella cataracts is not to aspirate them incompletely because eventually the eyes are lost. The process of aspiration reactivates the virus.

The Need for Close Monitoring

These children should be closely monitored. This includes evaluating visual development to be sure it is proceeding in a satisfactory manner. The surgeon’s responsibility is to both nurture the process of sight and to help prevent amblyopia. Otherwise, the outcome will be poor because of insufficient attention to the anti-amblyopia treatment.

Preoperative Considerations

The most important relates to the calculation and selection of the type of IOL to

be used and its correct power. The method and the considerations relating to IOL power calculation in pediatric cataracts is amply and clearly presented in pages 54, 55, 56 and Fig. 31, page 56.

The Decision to Implant IOL’s in Children with Cataract Surgery

How to optically correct patients with bilateral congenital cataracts and monocular congenital cataract has been a major subject of controversy for many years. Some distinguished ophthalmic surgeons 20 years ago were strongly against performing surgery in monocular congenital cataract followed by treatment of amblyopia with a contact lens. Visual results were so bad that children with this problem must be amblyopic by nature, they thought, and the psychological damage to the children and the parents by forcing such treatment was to be condemned.

Surgery of bilateral congenital cataracts at a very early age followed by correction with spectacles and sometimes with contact lenses usually ended with no better than 20/60 vision bilaterally. This was again a source for the belief that congenital cataracts either unilateral or bilateral were by nature associated with amblyopia, profound in cases of monocular cases and fairly strong in bilateral cataracts.

When posterior chamber IOL implantation in adults became established as the procedure of choice, strong influences within ophthalmology were adamantly opposed to their use in children for the following reasons: 1) the eye grows in length with consequent significant change in refraction. It was considered impossible to predict such change

and consequently, the accurate IOL power adequate for each child. 2) There was opacification of the posterior capsule in most cases. This required a second operation for posterior capsulotomy and the presence of an IOL would impede proper surgical maneuvers.

The situation has now significantly changed. The previous failures with spectacles and contact lenses, the new developments in technology and surgical techniques and the fresh insight of surgeons of a new generation have led us to discard the previous thinking and to consider the implantation of posterior chamber IOL’s a very positive development in children. This has been made possible by the following developments: 1) new medications that effectively prevent and/ or control inflammation. 2) The introduction of posterior capsule capsulorhexis by Gimbel in North America promptly followed by Everardo Barojas in Mexico and Latin America (Fig. 30). 3) High viscosity viscoelastics to facilitate intraocular surgery in smaller eyes. 4) New, more appropriate IOL’s for children and implantation in the capsular bag. 5) Refined technology that leads to a more precise calculation of the IOL power.

A «Major» Controversy No More

The controversy as to whether to implant IOL’s or not in the management of cataract surgery in children has been almost resolved. At present, most surgeons place intraocular lenses, whether treating congenital cataracts or traumatic cataracts, following evidence that they can be safely tolerated in most children. The informed consent discussion with the parent or guardian, however, should include the fact that intraocular lenses

have still not been approved by the FDA for use in children. This is a matter of particular importance in the U.S.

The previously existing controversy of the timing of the IOL implantation in children has also been resolved as a consequence of experience. Intraocular lens implantation may be significantly easier at the time of cataract extraction than at a later date, since iridocapsular adhesions and fusion of the anterior and posterior capsular flaps make a subsequent secondary implant procedure more challenging.

Surgical Technique

The Incision

A sclero-corneal tunnel 3.5 to 3.8 mm wide is the procedure of choice (Fig. 40-B). Manage the conjunctiva very carefully in case the patient develops secondary glaucoma later in life. Because the sclera is soft and elastic in children, it is hard to achieve a selfsealing incision. Consequently, the incision should be sutured.

The Anterior Chamber and Pupil

High-viscosity viscoelastic material is used because the anterior chamber is shallow in these small eyes. If the pupil is small, stretching the pupil with flexible iris retractors (Alcon-Grieshaber) can be very helpful (Fig. 198). They are placed before the continuous anterior capsulorhexis is performed.

Anterior Capsulorhexis

This is an important step to assure in the bag placement of the IOL. Its size should be smaller than the IOL optic. Zetterstrom

points out that the anterior capsule is thick and elastic in children and a capsular tear can easily extend out to the equator.

A central puncture is made with a cystotome and the leading edge of the capsule is grasped with forceps. Several repeated grasps are recommended to avoid extension to the equator and to assure maximal control. The capsulorhexis should be kept small because it usually enlarges due to the inherent elasticity of the capsule. (See figures 97, 98, 99, 100 for CCC with cystotome and 45, 46 with forceps).

Nucleus Removal

After an appropriate hydrodissection, the removal of the nucleus and cortex in the majority of cases can be performed using an I/A probe with a 0.5 mm orifice, because for the most part the congenital cataract is usually very soft. Occasionally the cataract is hard and has to be disassembled and removed. All the lens cortical material must be aspirated in order to reduce postoperative inflammation (Fig. 128, page 206). Proliferation of cells leading to a secondary cataract formation is more aggressive in the younger child.

Posterior Capsulorhexis

In children a posterior capsulorhexis combined with an anterior vitrectomy are necessary to produce a clear optical axis and reduce the need for a secondary operation. The diameter of the posterior capsulorhexis must be at least 3.5 to 4.0 mm or it will tend to close. Moreover, the anterior and posterior capsules must be separated with the use of additional viscoelastic. This maneuver will push the vitreous back and prevent its

prolapse into the anterior chamber (Fig. 211). Posterior capsulorhexis is performed by most surgeons before IOL implantation, as presented here. Nevertheless, some surgeons do it after IOL implantation, as shown in Fig. 30, page 52. The latter procedure may be cumbersome.

Anterior Vitrectomy

This important step is performed after completing posterior capsulorhexis and aims at removing 1/3 of the anterior vitreous gel before there is any vitreous presentation. It is

performed using a vitrectomy probe, as shown in Fig. 212. Special care should be given to removing any vitreous present in the anterior chamber. A so-called “dry” vitrectomy, without infusion of fluid, is safely performed between the anterior and posterior capsulorhexis. Viscoelastic is removed to avoid elevated intraocular pressure after surgery.

Using this method it is possible to implant an IOL in the capsular bag during primary surgery or in the ciliary sulcus if a secondary implantation is scheduled in the future.