Ординатура / Офтальмология / Английские материалы / Small Incision Cataract Surgery (Manual Phaco)_Singh_2002

push HPMC close to the posterior capsule. Practically the whole of the lens mass rises anteriorly and the chamber becomes deep. At this stage the HPMC cannula is introduced through the upper incision. This results in the raised lens mass passing out of the top incision. Further HPMC push into the lens fornices is done to raise and deliver the remaining lens masses. At the end, if so needed, a small saline irrigation/ aspiration is done. The technique described above seems to work best if capsulotomy has been done with a Fugo blade, since this capsulotomy allows the big lens mass to be delivered without tearing. It is pertinent to mention that Fugo blade helps make much bigger intact capsulotomy than by other procedures, which is an advantage.

Lens Implantation

The choice of an intraocular lens is surgeon’s preference. I use an artisan lens (earlier called iris-claw lens for the following reasons. This lens avoids the angle of the anterior chamber, the corneal endothelium, the reactive space behind the iris (which I call Pandora’s box), every part of the lens and the tissues in contact can be examined in the follow-up examinations, posterior capsulotomy is easy to perform afterwards, the lens can be explanted or exchanged atraumatically, if ever a need arises. The lens is well-tolerated as our 22-year experience shows.

Many surgeons have other choices–in the bag lens implantation with or without a posterior capsulotomy, anterior vitrectomy and optic capture. The sulcus fixation is however much more risky for fear of ciliary body erosion and related problems.

Peripheral Iridectomy

It is good to do peripheral iridectomy in most young patients even if an in the bag lens implantation has been done. The reason is that any postoperative reaction is likely to cause synechia formation and iris bombe. True, you can overcome this with a laser Peripheral Iridotomy (PI). But laser PIs are highly unpredictable in black eyes and are likely to get closed soon. In young infants, I have seen large iridectomies and even complete iridectomies closed with tissue growth, even without a sign of inflammation.

How to do a peripheral iridectomy through a pocket incision? It is not possible to hold the periphery of the iris. The other alternative is to hold the iris close to the inner opening of the incision, pull the iris downwards and cut it inside the eye with a scissors (normally we are used to cutting the iris by pulling it out). A number of

times the process of iris pulling will cause a tear at the iris root resulting in iris bleeding. The bleeding can be reduced by raising the pressure inside the anterior chamber with saline or HPMC and waiting for a sufficient length of time. In the end the anterior chamber is washed clean.

Air Bubble

The two sides of the pocket section come together only if the anterior chamber is well-formed at the end of the operation, either with saline or with air or a combination of the two. Make sure that there is no leakage from any incision. Look at the possibility of a leakage when the patient is out of anaesthesia. If in doubt, it is better to apply a couple of sutures and provide security to the incisions (Fig. 38.2).

The above description suffices for a patient of say 3 to 5 years suffering from a textbook type of zonular cataract without any other complicating factor. Obviously the conditions are going to be different if the patient is much younger, say of about 3 months of age or much older, say around 17 years.

Fig. 38.2: Look of the eye after surgery

Dislocated Lenses

Dislocated lenses are more difficult to manage for obvious reasons (Fig. 38.3). The following approaches are practiced:

1.Pars plana lensectomy and vitrectomy, with or without lens implantation. The intraocular lens fixation is in the sulcus, over some of the retained lens capsule. Or it can be a scleral fixated intraocular lens.

2.Anterior approach: A capsular tension ring followed by in the bag intraocular lens. If the crystalline lens is considerably off centre, then a loop of the intraocular lens may be scleral fixated.

Fig. 38.3: Subluxated lens

3.Lensectomy by one of the many ways, followed by angle supported lens.

4.Anterior route lens extraction followed by artisan lens implantation.

The size of the incision will vary with the technique adopted. For the last technique that I employ, the size and position of the incision remains the same as for routine congenital cataract cases. The lens extraction is done by one of the following ways:

1.Manual capsulotomy, dry aspiration of the lens and artisan lens implant.

2.Automated capsulotomy with Fugo blade. The beauty with this device is that the capsular bag does not move during the cutting process and the cut edge is stronger than we get by manual means. HPMC is injected into the capsular bag to deliver most of the lens while the rest is removed by dry aspiration assisted by HPMC. The use of this instrument minimises disturbance to the vitreous, since it becomes possible to preserve the zonular fibres that are present at the start of the procedure.

3.A dislocated lens with little or no zonular supported is manoeuvred into the anterior chamber, the pupil is contracted and the lens is removed by dry aspiration, the capsular bag being removed at the end. A small anterior vitrectomy is done after artisan lens implantation.

4.In adults with dislocated opaque lens, a small incision cataract surgery is highly risky. In some cases a 180° incision and cryo-extraction is a sensible procedure. In a rare case, the lens might need removal by lensectomy or phaco-fragmentation through pars plana route.

Traumatic Cataract

In most cases, it is possible to use the same basic pocket incisions to deal with most of the trauma situations, at the end of which an intraocular lens may or may not be implanted. For any kind of lens implantation, it will be necessary to create a favourable anatomical situation for the lens to be fixed. Synechia need to be broken and the space behind the iris cleared, before a lens can go into the sulcus. The iris needs to be freed from adhesions before an artisan lens can be fixed. Whenever anterior vitrectomy becomes necessary to deal with disturbed vitreous or to clear the visual axis, It is important to suture the incision line, else a satisfactory closure of the incision line is not possible.

Secondary Cataract

After cataract or secondary cataract formation is common after ECCE and lens implantation in paediatric patients. It may not form if the cataract was membranous, milkbag or one that had a pre-existing posterior capsular opening (and needed anterior vitrectomy). It may or may not form if a subtotal anterior capsulectomy was done during operation. Its formation in Marfan cases is not ruled out if the posterior capsule has been saved during lens extraction.

In subtotal anterior capsulectomy cases it has been observed that unless there is an element of inflammation, the secondary cataract is thin and can be easily cut with Yag laser or with a capsulotomy needle.

Sometimes the secondary cataract is thick and has dense synechia with the intraocular lens or with the uveal tissues. A manual capsulotomy in these cases can produce a traction on the vitreous and retina or the uveal tissues. For this reason it is necessary to adopt alternate approaches, which are:

•Make a pocket incision. Reach the membrane with the tip of a knife and stab it. Introduce a vitrectomy probe and cut the membrane if it can be held by suction. If it does not succeed, a Vannas scissors can be used to cut the membrane, with as little pull as possible. HPMC is used liberally to protect endothelium and to create space for the scissors to work.

•Erbium laser Erbium laser energy can easy cut a thick secondary cataract. A 1.5 mm incision is enough for the purpose. The broken up material is irrigated out.

•Fugo blade can cut a dense membrane without any resistance. It can also be introduced through a 1.5 mm incision. The membrane can be cut in two ways. Go round the membrane, cut it and then pull out the

separated piece. The other way is to keep touching the membrane again and again with the plasma blade tip. The touched point just disappears in the plasma field.

Secondary Lens Implantation

Secondary lens implantation in paediatric patients is an important field. Aphakia results from the surgery on congenital cataract, traumatic cataract after blunt or perforating trauma and after PP lensectomy for endophthalmitis resulting from perforating injuries. The presentations are extremely varied and each case merits individual assessment and an appropriate surgical approach. The surgical approach has the following ingredients:

•The incision is made in an anatomically undisturbed part of the limbus.

•The peripheral anterior synechia are broken if they are likely to interfere with secondary lens implantation.

•The synechia in the pupillary area are cut. Synechia between the posterior surface of the iris and the capsular membrane are separated and sufficient space is created, if a posterior chamber lens is to be inserted.

•The anterior chamber is cleared of vitreous and any

strands going to the limbal or the injury site.

The synechia can be cut with the tip of a disposable 27-gauge needle, with erbium laser or with Fugo plasma knife. The advantage with plasma knife is that the cutting is done without any bleeding.

The surgical and post-surgical problems connected with secondary lens implantation depend upon the type

of lens selected (angle supported, sulcus supported, in the bag and scleral fixated), the ease with which a space has been created where to fix the lens and the amount of trauma that is suffered by the tissues, especially uveal. Artisan lens implantation seems to be the least traumatic procedure in most cases, especially the ones that have no posterior capsule.

The most difficult cases are the ones in which pars plana vitrectomy has been done. The moment the anterior chamber is opened the eyeball seems to collapse. If a lens is introduced in the anterior chamber and is left un-held with a forceps, it call pass through the pupil and get lost in the vitreous cavity (without vitreous). A Sheet glide is a reliable tool to prevent such a mishap. Even a sheet glide can fall into the vitreous, if care is not taken. It is best to fashion a glide (it has to be made by the surgeon himself) such that its outer end is much larger than the incision line. In all cases of pars plana vitrectomy, it is important to suture all incision lines, howsoever, small, else the eyeball will tend to collapse in the postoperative period.

To Sum up

In paediatric cataract cases, the incisions are always small. But the construction of the incision line should be such that it allows the performance of all surgical steps, prevents collapse of the anterior chamber during surgery, allows perfect closure of the incision line at the end of the surgery and prevents the formation of peripheral anterior synechiae.

SICS in 39

Paediatric Cataracts

Kuldeep Kr Srivastava

P Vijayalakshmi

Cataract surgery has undergone great refinement in recent years. Small incision cataract surgery, has become the technique of choice, because of

early visual and functional rehabilitation. Self-sealing sutureless wound construction has recently achieved great success and popularity in adult cataract surgery but its use in paediatric cataract management is still gaining popularity and is not well established.1,2

Self–Sealing Sutureless Wound Construction

Since the self-sealing sutureless wound construction has achieved great success in adult cataract surgery, it was also applied to children,3 but with mixed success. Although one study has documented secure self – sealing sutureless wound following ECCE with IOL implantation in children, other surgeons found the need for suturing the wound at the conclusion of surgery because of aqueous leakage.4,5 In a prospective study investigating the role of sutureless wound construction in children, the wound leak was reported in 100% of eyes of children below 11 years of age who underwent ECCE with PPC with AV + IOL.6 The incidence of wound leak was only 33% in eyes of same age group that had an intact posterior capsule at the end of surgery. No leaks were observed in eyes of the patients above 11 years of age. The wound leak is probably because of low scleral rigidity in children causing fish mouthing of the internal aspect of the wound, with inadequate apposition of the corneal flap to overlying stroma. So, suturing of such wounds are required to ensure proper apposition of corneal flap.7 We suture such wounds as a routine practice in children below 11 years of age.

Capsulorhexis

Manual Continuous Curvilinear Capsulorhexis

Anterior capsulotomy shape, size, and edge integrity are important for long-term centration of a capsular fixated IOLs. Since manual continuous curvilinear capsulorhexis

has become a standard anterior capsulotomy technique in adult, it was naturally also applied to children but with mixed success.8 The paediatric lens capsule is more elastic than in adults and requires more force before it tears. Reduced scleral rigidity in children results in posterior vitreous upthrust when the eye is entered. The vitreous pressure pushes the lens anteriorly and keeps the anterior lens capsule taut which causes difficulty in completing the rhexis resulting in the so called “run away rhexis”. In addition, a small rhexis may end up much larger than intended, because of marked elasticity of anterior capsule in children. CCC can be applied on very young eyes but its successful application needs paediatric experience and modification of technique.4

For the successful completion of continuous curvilinear capsulorhexis (CCC) in children following points are helpful.9

•Use high molecular weight viscoelastics to push the anterior capsule back and deepen the anterior chamber. This will create laxity in anterior capsule and counter the effect of vitreous up thrust caused by globe collapse.

•Aim to make slightly smaller CCC in children than adults.

•While creating the CCC, frequently release the capsular flap and inspect the size, shape and direction of tear. Regrasp near the site of continuous tear and re-adjust the direction of pull as needed to keep the capsulotomy on the planned courses.

•Tractional forces must be directed centripetally at all times, rather than circumferentially in order to avoid extention of the CCC out to the equator.

•Additional viscoelastic should be injected as needed to keep the anterior capsule lax during the tearing.

•Lenticular content may leak into the anterior chamber during CCC as a result of increased intralenticular pressure from vitreous upthrust. If this happens, aspiration of a portion of lens contents may be needed before completing the CCC.

Vitrectorhexis

A mechanized, vitrector-cut anterior capsulotomy has compared favourably to manual CCC in a direct comparison using very fresh paediatric autopsy eyes.8 The mechanized capsulotomy, referred to vitrectorhexis is easier to perform and resists tearing during IOL placement. According to M Edward Wilson who performed vitrectorhexis in more than 150 children, after an initial learning curve, radial tears are very rare when using this technique.9

When performing a vitrectorhexis, the following surgical caveats are offered.9

•Use a vitrector supported by a venturi pump. Peristaltic pump system will not cut anterior capsule easily.

•Use an infusion sleeve or a separate infusion port, but with either approach, maintain a snug fit of the instrument in the incision through which they are placed. The anterior chamber of these eyes will collapse readily if leakage occurs around the instrument thereby making vitrectorhexis more difficult to

complete.

Vitrectorhexis begins by placing the vitrector with its cutting port positioned posteriorly, on the centre of the intact anterior capsule. The cutter is turned on and suction is increased till the anterior capsule is engaged and opened. It usually begins with cutting rates of 150 to 300 cuts per minute and an aspiration maximum of 150 to 250 mm Hg. With the cutting port facing posteriorly against the capsule, the capsular opening is enlarged to the desired shape and size. Although vitrectorhexis is less than ideal when compare to CCC,it is next to CCC.

Bipolar Radiofrequency Capsulotomy

Radiofrequency diathermy capsulotomy, first described by Kloti in 1984 and then by Gassman and Coauthors in 1988,has been used as an alternative to CCC for intumescent adult cataracts and for cataract surgery in children.10,11,12 The Kloti device cuts the anterior capsule with a platinum alloy tipped probe using a high frequency current of 500 KHz. The probe tip is heated to about 160°C and produces a thermal capsulotomy as it is moved in a circular path across the anterior capsule. Even when performed perfectly, a diathermy cut capsulotomy can be seen to have coagulated capsular debris along the circular edge. In addition, the edge has been shown experimentally to be less elastic than a manual CCC edge.13 Since the stretching force needed to break the edge of a diathermy cut capsulotomy is much less compared to a CCC edge, the surgical manipulation

needed to remove a cataract and place an IOL may result in a radial tear when the diathermy is used. However, Comer et al12 reported no radial tear when using the diathermy cut capsulotomy in children where the mean age was 23 months.

Posterior Capsular Opacification (PCO)

The posterior capsular opacification, which is not a major concern in adults, remains a significant concern in children particularly below two years of age. According to a study in children, PCO occurs an average of two years after surgery regardless of the age.14 Experience with Nd: Yag capsulotomy in children has shown mixed results, with recurrence of opacification requiring repeated laser treatment and sometimes surgical membranectomy as a secondary procedure.15,16

Prevention of Posterior Capsular Opacification

In order to prevent PCO, various techniques have been in practice. Some of them are as follows:

1.Extracapsular cataract extraction with primary posterior capsulotomy/capsulorhexis with anterior vitrectomy (ECCE + PPC/PCCC + AV) Because of high incidence of PCO in children, PPC/PCCC should be considered

in children who are not expected to be a candidate for Yag capsulotomy within 18 months of surgery.14 The PPC and AV is combined with ECCE in order to avoid the need for Yag capsulotomy and secondary surgical membranectomy after ECCE, while retaining a capsular bag that is suitable for IOL implantation. It is more effective than procedures, which leaves vitreous undisturbed (ECCE +PPC) in preventing reopacification of posterior capsule. Although technically challenging when IOL implantation is planned, this approach has shown encouraging early

results as a means of maintenance of a clear visual axis.16,17

2.Posterior capture of IOL optic by posterior continuous

curvilinear capsulorhexis (PCCC) A new technique developed by Gimbel 18 consists of ‘in the bag’ IOL placement followed by PCCC and capture of the IOL optic by the PCCC. This approach was premised on the belief that 360° apposition of the anterior and posterior capsular leaflets would lead for formation of a Sommering’s ring configuration anterior to IOL and that lens epithelial cells would be kept in anterior chamber, where they would be carried away with aqueous fluid. Gimbel’s preliminary results appear to support this view.

3.IOL Modification A square edge intraocular lens has been proposed to prevent PCO.19

Management of PCO

a.YAG capsulotomy Cystoid macular edema (CME), which is an important complication of YAG capsulotomy in adults, is not of a major concern in children. It can be done even on the table at the completion of the surgery or weeks after surgery without a significant risk of CME.

b.Surgical membranectomy In certain situations like thick PCO, uncooperative patient, recurrence of PCO after YAG capsulotomy or soft after-cataract, YAG capsulotomy may not clear the visual axis and surgical membranectomy with anterior vitrectomy is required.

IOL Implantation in Children

The advantage of using IOL for aphakic correction in children is its ability to provide continuous, optically optimal refractive correction, immediately following surgery without dependence on compliance by the patient and family. Although IOLs were first tried in children in the late 1950s, 20 paediatric usage has lagged far behind implantation in adults because of the basic conservatism of most paediatric ophthalmologist who wanted to see ample, confirmation of the safety and efficacy of IOLs in adults before subjecting children to their widespread uses. Recent reports in the literature indicate very encouraging short to intermediate term results following childhood cataract surgery with IOL

implantation and have considerably decreased the controversy surrounding it.3,4,13,21,22 Presently the major

controversy of IOL implantation in children is the problem of its application in infants. The small dimension of infant eye, the many significant difference between its tissue and those of the mature eye, the magnitude of changes it will undergo during completion of development, and its tendency to react intensively to the presence of an intraocular foreign body, are the major limitations of IOL implantation in infants.

Choice of IOL

Of available lens materials, only PMMA has so far stood the test of time adequately to be considered appropriate for implantation in eyes with life expectancy of many decades. Presently foldable IOLs (silicon and acrysoft) and heparin surface modified IOLs are also being implanted with short-term encouraging results.23,24 Single piece, biconvex modified ‘C’ loop designs have been the choice of most paediatric cataract surgeon in recent

years.25 The lens size of 12 mm is generally suitable for posterior chamber implantation in eyes more than two years old, with capsule fixation.26 The lens size of 10 mm is reccomonded for children less than two years of age. Optic diameter and designs are not very important.

IOL Power

Selection of IOL power has been one of the most controversial topics relating to paediatric cataract management. It is well known that the power required for aphakic correction declines rapidly during first year of life and to a considerable degree further during the childhood. Thus, a pseudophakic eye that is emmetropic at age of one year may become 5–10 diopters myopic at maturity. Furthermore, if an eye is rendered significantly hypermetropic at early age, it will need supplemental refractive correction to ensure optimal visual development negating much of the advantage of IOL.

Gordon and Donzis, in their study on the growth of the eye after birth, demonstrated that approximately 90% of the growth of the eyeball is complete during the first 18 months after birth.27 Since the overall increase in axial length from 18 months of age to 11 years is about 2mm, many surgeons today attempt towards making the eye hypermetropic by two diopters in children between two and four years of age.27

Some of the currently prevalent approaches are outlined below:

•Vasavada and Chauhan (1994), recommended 60% under correction for infant eyes. Using modified SRK II formula 1.0 D is added for every 1mm decrease in

axial length instead of standard 2.50 D, taking 23.0 mm as an average adult axial length and 22 .0D as standard IOL power.3 This approach results in 60% undercorrection. Based on a similar modification, Dahan and Salmenson (1990) aim for 80% undercorrection in children below 18 months of age.28

• Dahan et al (1997) suggested the guidelines for IOL power calculation as below 29

<2 years : Do Biometry and undercorrect by 20%

2-8 years : Do Biometry and undercorrect by 10%

•Same power as calculated with SRK II formula is implanted in children over 8 years of age.

With the above methods of IOL power calculation, child is left with residula hypermetropia which is amblyogenic and needs supplemental correction. To avoid this problem, Piggyback intraocular lenses have been proposed wherein one IOL of adult power is implanted in the bag (permanent lens) and another foldable acrylic lens of 7-14D is implanted in sulcus (temporary lens) at the same sitting.30 Temporary lens is removed later when an adult refraction is achieved.

IOL Placement

Since the uveal tissue in the children is highly reactive, ‘in the bag’ placement of IOL is highly desirable. The significantly lowered incidence of severe postoperative uveitis described in several recent reports in paediatric IOL implantation seems largely attributed to improved success in ‘in the bag’ implantation.3,4 In eyes that lack sufficient capsular bag for ‘in the bag’ implantation, ciliary sulcus placement is considered an alternative site of lens placement.23 Majority of the surgeons do not consider anterior chamber IOL placement in children even in absence of adequate capsule support.23

A new technique developed by H.V. Gimbal consist of in the bag placement of IOL followed by posterior CCC and capture of the IOL optic by PCCC.18 This technique claims to maintain clear visual axis for longer time and preliminary results appears to support this view.18

REFERENCES

1.McFarland MS: McFarland surgical technique. In Gills JP, Sanders DR (Eds): Small–Incision Cataract Surgery: Foldable Lenses, One–Stitch Surgery, Sutureless Surgery, Astigmatic Keratotomy. Slack Inc, Thorofare, NJ 107-16, 1990.

2.Th.Pfleger, Scholz U, Skorpik Ch: Postoperative astigmatism after no-stitch, small incision cataract surgery with 3.5 mm and 4.5 mm incisions. J Cataract Refract Surg 20: 400-05, 1994.

3.Vasavada AR, Chauhan H: Intraocular lens implantation in infants with congenital cataracts. J Cataract Refract Surg 20: 592-98, 1994.

4.Gimbel HV, Ferensowicz M, Raannan M et al: Implantation in children. J Pediatr Opthalmol Strabismus 30: 69-79, 1993.

5.Zetterstrom C, Kugelberg U, Oscarson C: Cataract surgery in children with capsulorhexis of anterior and posterior capsules and heparin–surface–modified intraocular lenses.

J Cataract Refract Surg 20: 599-601, 1994.

6.Basti S, Krishnamachary M, Guptha S: Results of sutureless wound construction in children undergoing cataract extraction. J Paediatr Ophthalmol Strabismus 33(1): 52-54, 1996.

7.Gimbel HV, Sun R, DeBroff BM: Recognition and management of internal wound gape. J Cataract Refract Surg 21: 121-24, 1995.

8.Wilson ME, Bluestein EC, Wang XH et al: Comparision of mechanized anterior capsulotomy and manual continuous capsulorhexis in pediatric eyes. J Cataract Refract Surg. 20: 602-06, 1994.

9.Edward Wilson M: Anterior Capsule Management for Pediatric Intraocular Lens Implantation. J Paediatr Ophthalmol Strabismus 36: 314-19, 1999.

10.Gassmann F, Schimmelpfennig B, Kloti R: Anterior Capsulotomy by means of bipolar radiofrequency endodiathermy. J Cataract Refract Surg. 14: 673-76, 1988.

11.Delcoigne CD, Hennekes R: Circular continuous anterior capsulotomy with high frequency diathermy. Bull Soc Belg Ophthalmol 249: 67–72, 1993.

12.Comer RM, Abdulla N, O’ Keefe M: Radiofrequency diathermy capsulorhexis of the anterior and posterior capsules in pediatric cataract surgery: priliminary studies. J Cataract Refract Surg 23: 641-44, 1997.

13.Luck J, Brahma AK, Noble BA: A comparative study of the elastic properties of continuous tear curvilinear capsulorhexis versus capsulorhexis produced by radiofrequency endodiathermy. Br J Ophthalmol. 78: 392–96, 1994.

14.David A Plager, Stephen N Lipsky, Stephen K Snyder et al: Ophthalmology 104: 600-07, 1997.

15.Atkinson CS, Hiles DA: Treatment of secondary posterior capsular membranes with the Nd: YAG laser in a pediatric population. Am J Ophthalmol 118: 496-501, 1994.

16.Surendra Basti, Uma Ravishankar, Satish Gupta. Results of prospective evaluation of three methods of management of paediatric cataracts. Ophthalmology 103: 713-20, 1996.

17.Mackool RJ, Chattiawala H: Pediatric cataract surgery and intraocular lens implantation: a new technique for preventing or excising postoperative secondary membranes. J Cataract Refract Surg 17: 62-68, 1991.

18.Gimbel HV, DeBroff BM: Posterior capsulorhexis with optic capture: Maintaining a clear visual axis after pediatric cataract surgery. J Cataract Refract Surgery 20: 658-64,1994

19.Nishi O, Nishi K: Preventing posterior capsular opacification by creating a discontinuous sharp bend in the capsule.

J Cataract Refract Surg 25: 521-26, 1999.

20.Choyce DP: Correction of uni-ocular aphakia by means of anterior chamber acrylic implants. Trans Ophthalmol Soc UK. 78: 459-70, 1958.

21.Dahan E, Salmenson BD: Pseudophakia in children. J Cataract Refract Surg 16: 75-82,1990.

22.Sinskey RM, Stoppel J, Amin P: Long term results of intraocular lens implantation in pediatric patients. J Cataract Refract Surg 19: 405-08, 1993.

23.Sima Pavlovic, Felix K Jakobil, Mickeal Graef et al: Cataract Refract Surg 26: 88-95, 2000.

24.Surendra Basti, Murali K Aasuri, Madhukar K Reddy et al: Cataract Refract Surg 25: 782-87, 1999.

25.Apple DJ, Mamalis N, Brady SE et al: Biocompatibility of implant materials: A review and scanning electron

microscopic study. Am Intra–ocular Implant Soc J 10: 53– 66, 1984.

26.Wilson ME, Apple DJ, Bluestein EC et al:, Intraocular lenses for pediatric implantation: Biomaterials, designs and sizing.

J Cataract Refract Surg 20: 584-91, 1994.

27.Gordon RA, Donzis PB: Refractive development of the human eye. Arch Ophthalmol 103: 785-89, 1985.

28.Dahan E, Salmenson BD: Psedophakia in children. J Cataract Refract Surg 16: 75-82, 1990

29.Dahan E, Matthias UH, Drusedau: Choice of lens and dioptric power in paediatric pseudophakia. J Cataract Refract Surg 23: 618-623, 1997.

30.Edward Wilson JI: Paed Ophthal and Strabismus 36: 28186, 1999.

Posterior Capsule 40

Opacification

Jagat Ram

Gagandeep S Brar

Posterior capsule opacification (PCO) and posterior chamber intraocular lens (PCIOL) decentration (Fig. 40.1) still remain two major complications of

extracapsular cataract surgery (ECCE) or phaco- emulsification.1-6 Ridley, who performed the first intraocular lens implantation in 1949, himself noted these complications in his earliest patients.7 In his initial publications, he described lens decentration, and remarking that apparently, the most difficult problem was to retain the lens in position. He also recognized the problem of PCO and designated it as “the principal complication” that is not easy to treat, and which requires division of posterior capsule, i.e surgical posterior capsulotomy.8,9 Control of decentration and PCO is becoming more necessary now that IOL implantation is emerging as a refractive procedure that mandates almost a perfect optical rehabilitation as opposed to the former goal of simply removing the opaque lens material and achieving safe but less than optimal visual rehabilitation.2-5 As the cataract operation continues to be perfected, major goal is to eliminate these complications.

Clinical studies have noted an incidence varying between 10-50 per cent of posterior capsule opacification following ECCE or phacoemulsification with PC IOL implantation.1-3,12-25 Schaumberg et al conducted an important metanalysis of published articles on PCO and generated pooled estimate of eyes developing PCO over three postoperative points: 1,3 and 5 years. They noted that even today the rate of PCO remains unexpectedly and unacceptably high-still over 25 per cent during the 5-year postoperative period.1 Furthermore, adverse clinical sequelae may be associated with Nd:YAG laser posterior capsulotomy. Last but not the least, there are very significant and compelling financial reasons to eliminate the necessity to do Nd:YAG laser capsulotomy. Nd:YAG laser posterior capsulotomy now ranks as the second most expensive surgical cost to the US health care system, second only to the cost of the original cataract operation.13

Fig. 40.1: Slit lamp photograph of left eye of a 65 years old woman, status postcataract surgery (ECCE); with marked upward decentration of a bag-sulcus fixated all-PMMA IOL. Note VS-PCO in the visual axis and sutures are also seen at the incision

The reported Nd:YAG laser posterior capsulotomy rate ranged from 30 to 50 per cent in the 1980s.2,3,11 More recent reports document an additional decrease in PCO and Nd: YAG laser capsulotomy rates.5, 11,14-17 With the use of modern surgical techniques and IOLs, posterior capsule opacification and Nd: YAG laser posterior capsulotomy rate is decreasing to less than 10 per cent.18-23 In a recent study by Apple et al17 comparing foldable versus rigid designs, the foldable IOLs were associated with a much lower Nd: YAG laser posterior capsulotomy rate (14.1% vs. 31.1%). Surgical tools and IOLs are now available to bring these rates down to single digits. Careful application and use of these tools by surgeons can genuinely lead in the direction of virtual eradication of secondary cataract, the second most common cause of visual loss worldwide.

Pathogenesis of Posterior Capsule Opacification

Most secondary cataracts are caused by proliferation of equatorial lens epithelial cells, forming the pearl form of posterior capsule opacification.26 Posterior capsule plaques or fibrous plaque detected in patients after ECCE are not uncommon in the developing countries27 and such plaques are rarely seen in the industrialized world.

The epithelium of the lens consists of anterior epithelial cells known as A-cells which is single continuous cell line. These cells are continuous with the cells of the equatorial lens bow. The cells of equatorial lens bow are the E-cells, which comprise the germinal cells undergoing mitosis as they peel off from the equator. They continuously form peripheral cortical fibers. A-cells tends to remain in place and not migrate and are prone to change toward fibrous tissue (fibrous tissue metaplasia) when disturbed. In contrast E-cells of equatorial lens bow tends to migrate along the posterior capsule and form pearls form of posterior capsule opacification (Fig. 40.2). These equatorial cells are the primary source of classical secondary cataract especially the pearl form of posterior capsule opacification.26 Fibrous form of posterior capsule opacification occurs as result of either posterior proliferation of A-cells or may result from a fibrous metaplasia of posteriorly migrating E cells.

Fig. 40.2: A slit lamp photograph of eye in a 58 years old female with sulcus-sulcus fixated all PMMA IOL after an ECCE showing posterior capsule opacification (epithelial pearls) in the visual axis

Clinical appearance of PCO may also be caused by a postoperative localized endophthalmitis, a condition which has been recognized as a cause of persistent,

usually low grade uveitis.28-30 Meisler and associates28 were first to recognize the role of Propionibacterium acnes as an offending organism. Piest and associates29 and Apple and associates30 were the first to emphasize the concept of a post-ECCE localized infectious process caused by sequestrated organism within the capsular bag. Clinically, it is important to be aware of the fact that clinical picture of PCO may be produced by localized endophthalmitis. The use of Nd: YAG laser capsulotomy to treat the posterior capsule thickening in this condition may lead to precipitation of severe inflammation.

Evaluation Techniques for

Posterior Capsule Opacification

Methods of evaluation are important to measure the progress of posterior capsule opacification. Most of the studies evaluate posterior capsule opacification after ECCE/phacoemulsification after full dilatation of pupil using slit lamp biomicroscopy. PCO is defined as opacification of the posterior capsule in the visual axis that is observed on slit lamp biomicroscopy which includes Soemmering’s ring (PCO peripheral to the IOL optic), Elschnig’s pearls and fibrous opacification behind the IOL optic. The degree of opacification is assessed using distant direct ophthalmoscopy, direct visualisation by slit lamp biomicroscopy, and decrease in best corrected visual acuity after surgery. Visually significant posterior capsular opacification is defined as a decrease in the best corrected postoperative vision by two Snellen lines. Tetz described a photographic image analysis system that can morphologically score posterior capsule opacification without dependence on visual acuity testing.31 Standardised slit lamp retroillumination photographs are analysed. Posterior capsule opacification score is calculated by multiplying the density of opacification and graded from 1-4 by the fraction of capsule area behind the IOL optic that is opacified. This technique shows good interand intra-observer reliability. Pande et al reported a more sophisticated system of retroillumination imaging of the posterior capsule using a computerized high resolution digital system that can produce excellent images for objective documentation and quantitative measurement of posterior capsule opacification.32 Apple et al utilised Miyake-Apple posterior photographic technique (Fig. 40.3) for analyzing commonly used IOL model in eyes obtained postmortem to evaluate PCO and whether or not an eye had an Nd: YAG laser capsulotomy.17