Clinical

Cataract Surgery in Retinitis Pigmentosa Patients Dr. Rathini Lilian David, MS Resident, Aravind Eye Hospital, Madurai

Cataract is a recognized complication of all types of retinitis pigmentosa especially posterior sub capsular lens opacity which occurs at a relatively younger age, which may be combined with a restricted visual field causing significant visual disturbance. Glare1 is a major symptom and the patient may require surgery at a younger age. Apart from the general risks of cataract surgery, there are specific additional risk factors2 that may result in decreased visual outcome after cataract extraction in the presence of RP namely, 1. The zonules are usually fragile in RP. 2. Posterior capsular opacificaton and anterior capsular contraction are more aggressive in the presence of RP. The reason for the increased cellular proliferation of the capsular remnants may be due to the cellular nature of the posterior capsule in retinal dystrophies. There is a high incidence of posterior capsular opacification about 63%. This reaction may be due to release of mediators by the neurosensory retina which may modify the lens fibre growth and differentiation. Similar stimulus may cause the contraction of the anterior capsulorhexis observed in 9.6%. • Outer retinal atrophy at the macula in advanced RP. • Macular edema occurs in approximately 10 – 15% of cases.2 • Risk of phototoxic retinal damages in normal patients undergoing cataract surgery. • The threshold for light damage is probably lower in RP.

In a study conducted by Jackson et al,2 patients with X-linked disease had surgery approximately 10 years earlier than the other groups. The predominant cataract morphology in 96.5% of RP patients was typically a combined posterior cortical and posterior subcapsular lens opacity. The morphology of cataract did not vary significantly between heredofamilial group.3 Heredofamilial types of RP and age at surgery

Number

AD

AR

27

26

6

33

46.3

36.3

49.5

Mean age at 48.4 surgery

XSimplex linked

In large series of 142 eyes of patients with RP, following cataract surgery visual acuity improved in 77%, was unchanged in 20.5% and worsened in 2.5% eyes. A subjective improvement in 96.6% despite the acuity being unchanged or worse. The majority of them had confirmed or suspected macular edema which do not show any leakage on fluorescein . In another study by John.R.Hekenlively et al 1 83% of the eyes in the study achieved an improvement in visual acuity of at least 2 lines on the Snellens Chart. Prognosis • Patient benefit from early cataract surgery and the vast majority have a subjective improvement in their symptoms. • The benefit from surgery for patients with a poor pre-op acuity is less marked because of preexisting macular edema.

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• Due to susceptibility of anterior capsular contraction a small capsulorhexis should be avoided. • The use of CTR is proven to reduce the rate of contraction. • Also avoid the use of silicon IOL and plate haptics due to increased risk of anterior capsular contraction. Anterior capsular contraction Contraction of the anterior capsule opening is a unique complication of continuous curvilinear capsulorhexis in cataract surgery. The capsule contraction syndrome is defined by Davison as “an exaggerated reduction in the anterior capsulotomy opening and equatorial capsular bag diameter after extracapsular cataract surgery”. It usually occurs when the anterior surface of the IOL optic biomaterial4 comes into contact with the adjacent posterior aspect of the anterior capsule, the remaining anterior lens epithelial cells {A cells} may undergo fibrous metaplasia leading to anterior capsular contraction.5 ACO is a misnomer as it is not the capsule that opacifies but rather the cells lining the capsule. A more accurate term would be Anteior subcapsular opacification. ACO generally occurs much earlier in comparison to PCO within the first 3 to 6 months postoperatively.5 An excessive anterior capsule contraction may lead to anterior capsular fibrosis or opacification causing clinical problems and sequelae such as capsulorhexis phimosis and IOL decentration and difficulty in visualizing the retinal periphery. The contrast sensitivity is affected more than visual acuity according to Ken Hayashi.6

Pathology The cuboidal cells lining the anterior capsule (A cells) are the cells of origin of Anterior Capsular Opacification (ACO). Hara et al indicated that post-op ACO is composed of fibroblast - like cells derived from metaplasia of lens epithelial cells and collagen.

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The ACO is composed of proliferated cellular components and extracellular matrix. The proliferation was located between IOL optic and anterior capsule. Ultrastructural analysis revealed that the cell composition had two characteristics of epithelial cells • A basal lamina • Desmosome between the adjacent cells The extracellular matrix consists of collagen fibrils, basal lamina like material and microfibrils There are 2 phases in the formation of ACO • An early phase consisting of proliferation of lens epithelial cells. • Late phase involving the degeneration or disappearance of lens epithelial cells and the presence of extracellular matrix. According to Caporossi et al 7 the proliferating tissues were devoid of vessels and composed of dense fibrous tissue and numerous activated fibroblasts with contractile capacity (myofibroblast) and they were strongly positive for α-SM actin.7 According to Okihiro Nishi8 the fibrosis may be caused by cytokines and IL -1, IL -6 synthesized by the residual lens epithelial cells, that in turn affect the epithelial cells in an autocrine manner. Factors contributing to ACO • The initial size of capsulorhexis • The IOL material and design • Preexisting conditions for example the quality of zonular support. Capsulorhexis size Continuous Curvilinear Capsulorhexis (CCC) is the preferred method of capsulotomy in cataract surgery. Gimbel9 detailed the numerous advantages of CCC. The CCC is stronger, resistant to peripheral extension, preserves the bag and allows in the bag implantation. Endolenticular phacoemulsification can be done with minimal traction on the zonular fibres and a sulcus fixated IOL can be placed in the presence of posterior capsular defect.

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Capsulorhexis also lowers the incidence of PCO according to Tae Kyung Park et al.10 The sphincter effect of an intact capsulorhexis seems to be important in creating significant capsular shrinkage. 11 The ideal capsulorhexis size is 5.5 mm to 6 mm, which will protects the pupillary zone and thus prevent progressive capsular contraction. With a rhexis size smaller than the diameter of the IOL optic, the contact of the optic biomaterial with the anterior capsule will induce contraction. However some authors like Gonver, Sickenberg and G. Van Melle12 found no relation between the initial rhexis size and the magnitude of contraction. Tsubi et al indicate an unfavourable effect of in the bag fixation with a small rhexis and thus a broad area of contact between the IOL optic and anterior capsule. It is postulated that the more epithelial cells that are left behind, greater the potential for contraction. According to Hayashi et al a larger size rhexis decreased the risk of contraction but there was a higher risk of PCO. Another phenomenon is the capsule contraction syndrome related to the small rhexis size defined as a blockage of the contents within the bag. IOL material and design A rigid optic associated with a resistant haptic could resist some of the centripetal forces induced by capsular fibrosis, whereas a flexible lens might not. IOL optic material silicone13,14 has a higher rate of contraction than single piece PMMA according to Cochener and co-authors13 due to the low grade inflammation.12 Acrylic has the lowest rate of contraction, this may be due to the increased adhesiveness of the acrylic IOL to the capsule inhibiting LEC migration and thus metaplasia according to Tae Kyung Park et al .10 The single piece Acrysof IOL showed lesser ACO than the three piece Acrysof IOL as the three piece acrylic IOL has a relatively flat anterior curvature.15

AECS Illumination

The Poly Hema IOL also resulted in marked contraction according to Choun–Ki Joo et al.16 Macroscopic study performed by Werner et al 13 confirmed that ACO scores are higher with silicone plate IOL17,2 which may be due to the larger area of contact. The lowest mean decentration and the ACO scores are obtained with hydrophobic Acrysof IOL.13 Square edged optic design is more important for preventing PCO than ACO.4 Round edge IOL has a higher rate of ACO than square edge. It is recommended not to use soft lenses where increased inflammation is anticipated cases like in Diabetes, Pxf, retinitis pigmentosa, uveitis, trauma according to Davison.18 Preexisting conditions During an intact CCC procedure, the centripetal force generated by the capsular fibrosis along the smooth circular margin of the capsular opening exceeds the centrifugal zonular force causing contraction of the capsule according to Davison et al16. When the zonular force is weak, the strength of centripetal contraction is exaggerated and the capsular opening contraction may be eccentric. Conditions prone to contraction are retinitis pigmentosa, uveitis, trauma, diabetes, 19 high myopia, Pxf,20 myotonic dystrophy,21 advanced age, previous ocular surgeries. The zonular weakness may be one of the factors responsible. Also instability of the blood aqueous barrier appears to be an inciting factor for the contraction. Macroscopic Classification of ACO Centrifugal Forces Normal zonular traction Minimal retained lens epithelium

Centripetal Forces Weak zonular support

Large anterior capsulotomy Can-opener

Small anterior capsulotomy Capsulorhexis

More retained lens epithelium

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Grade 0 - Clear {transparent} anterior capsule. Grade 1 - Opacification localized to the edge of the rhexis. Grade 2 - Diffuse opacification sometimes with areas of capsular folding . Grade 3 - Interior opacification with areas of capsule folding. Grade 4 - Constriction {phimosis}of the capsular opening {capsulorhexis diameter 3.5 mm} Sequelae of ACO The process of contraction occurs in 4 stages • Fibrosis or opacification of the capsulorhexis margin occurs at some places. • The entire anterior capsular edge is in contact with the IOL optic biomaterial becomes progressively opacified. • Formation of capsular folds. • Excessive or asymmetric fibrosis and shrinkage may result in complications like eccentric displacement of the CCC opening, IOL decentration, capsulorhexis phimosis, visual obscuration. Methods of Prevention of ACO • Large capsulorhexis of 5.5 mm. • An effective hydrodissection helps to make lens substance removal easier, ensuring complete removal of cortex and cells. • Polishing of the anterior capsule and removing anterior sub capsular epithelial cells.22 • Nishi18 proposed the use of irrigation aspiration tip with abrasive surface. • By implanting a capsule tension ring. • Placing the IOL made of the right material. Treatment of ACO Davison23 was the first to advocate the use of Q Switched Nd : YAG LASER capsulotomies to interrupt the contraction forces and to maintain the IOL centration. When capsular phimosis develops, radial anterior Nd :Yag capsulotomies can be performed to create 4 equally spaced radial cuts about 1 mm

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in length using an average power of 1.5 to 2 mJ. It might be prudent to initiate linear cuts in all 4 quadrants removing the traction symmetrically before completeing the cuts. The technique may avoid extension of a radial tear from the first cut . According to a study done by Hayashi et al,24 3 relaxing incisions made in the anterior capsule at 0, 120, 140 meridan have a clinically relevant preventive effect on contraction than 2 relaxing incisions. In addition the number of incisions did not affect the IOL centration. Some authors recommend releasing anterior capsulotomies immediately when capsule contraction is observed. They postulate that early Nd: Yag laser25 for active capsule fibrosis may help rather than late intervention. It also prevents later IOL decentration. According to Sunil P Deokule23, the success rate was more if capsulotomy was performed within the first 6 months of cataract surgery. Complications of Nd : Yag Anterior Capsulotomy23 • IOL Decentration • Extension of the radial cuts • Hyphema • Raised IOP • Uveitis • Loss of endothelial cells • Anterior lens surface pitting • Posterior capsule rupture

Methods of Assessment of Anterior Capsular Contraction Scheimpflug Videophotography (EAS 1000; NIDEK)17,26,27 The EAS 1000 System is composed of Scheimpflug charge coupled videotape camera and on line image analysis computer. The margin of the anterior capsule opening in the retro illumination image is traced digitally. The computer uses a special image analysis software to measure the anterior capsule opening area.

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Evaluation of Posterior Capsule Opacification (EPCO)

The Evaluation of Posterior Capsular Opacification (EPCO) software which is a computer assisted system is used in the evaluation of anterior capsular contraction; it was first introduced in 1997 by Tetz et al. It is an objective method of assessment of PCO. The pupil should be well dilated. Standardized retro illumination photographs are taken using Zeiss photo slit lamp at 10 x and 16 x magnification using a co-axial illumination with a flash light intensity and a fully open f-stop. For better evaluation the slit is slightly decentered towards the temporal and nasal rim of the IOL optic. Specialized digital cameras attached to the slit lamp are used for taking images. Method Evaluation within the total IOL optic border method, where 100% area behind the IOL optic is taken for evaluation. The border of the IOL optic is marked by three points in order to get the optic area as 100% evaluation area. A closed circle is drawn along the capsulorhexis. The total IOL area is taken as 1. Hence grading is done using ‘area 1 ‘minimal of the EPCO software. Percentage of ACO will be calculated by multiplying the EPCO value by 100. Slitlamp Photographic Technique and image Analysis12 Standardized photographs of the anterior capsule in psuedophakes can be taken with a digital camera (NC 2000 kODAK) mounted on a photograph slit lamp (Zeiss 40 SL –P). The prerequisite is that the pupil dilation should exceed the size of the optic. The slit lamp settings used are; aperture 64, intensity of flash 3; slit angles 45 to 60 degrees; slit width 3.0 to 5.0; slit height maximal; magnification x 10. The angle of incidence of the slit is adjusted until reflex artifacts from the cornea or IOL were minimized but was always kept between 45 degrees and 60 degrees.

AECS Illumination

Two photographs are taken of each eye, 1 of the temporal and 1 of the nasal half focused on the anterior capsule; the two photographs are combined to produce a final image of the entire capsule. Method The area of the anterior capsule in contact with the IOL was defined as the area of analysis (area A). Only a part of the dark area not directly illuminated by the slit beam within the capsulorhexis (area B) served as the control area. The difference in brightness between the area of analysis and the control area, defined the grade of fibrosis in percentage, with 0% representing a clear anterior capsule and 100% a completely white anterior capsule. This method is simple and straight forward. It allows standardized documentation and objective quantification of ACO with highly reproducible results. AQUA (Automated Quantification of After – Cataract)28 Standardized high resolution digital retro illumination photographs were taken in the plane of the anterior capsule. The capsulorhexis area was measured with the computer program Aqua (Automated Quantification of After - Cataract). The optic diameter was measured and used as a reference to define the magnification. The capsulorhexis edge was outlined roughly with the cursor. Thereafter, an automated capsulorhexis edge detection algorithm traced the capsulorhexis edge. Incorrect points were corrected manually. The capsulorhexis area (square millimeters) was then calculated by the software.

Capsule Tension Ring The capsule tension ring is polymethyl methacrylate (PMMA) intraocular implantation device introduced in 1993 by Witschel and Legler.29 The original was introduced into the market by Morcher.

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How it Works? The diameter of the CTR is larger than that of the capsular bag. (Average 10.37 ± 0.25) • The centrifugal force inherent within the CTR expands the capsule equator. • Buttresses areas of poor zonular support. • Provides equal distribution of support for the remaining zonules. • Tautens the posterior capsule. Applications of the CTR • In zonular rupture or dehiscence after blunt trauma or surgical trauma.30 • Inherent zonular weakness as in pseudoexfoliation, high myopes, diabetics, retinitis pigmentosa, myotonic dystrophy, uveitis.10 Eyes with zonular weakness are at a higher risk of developing asymmetrical capsule shrinkage because the remaining zonules cannot resist the centripetal forces exerted by the fibrosing anterior capsule rim. • To maintain the circular capsule’s contour and to stretch the posterior capsule. • Better IOL centration.29,31 • Resists contraction of the capsular bag30,29 by inhibiting the migration of the lens epithelial cells. It has been suggested that the contact between the PMMA optic and sub capsular epithelium induces an inflammatory response and fibrosis. The CTR provides an interspace by keeping the anterior capsular leaf away from the anterior optic surface and the posterior capsule, preventing the myofibroblastic transdifferentiation of LEC on the back surface. • Protects against capsule fornix aspiration. • Prevents irrigation fluid flow behind the capsule. Selection of Size The size of the CTR is chosen based on the capsular bag dimension and usually a large diameter CTR

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is preferred32 approximately corresponding to the white to white diameter.29 VASS and co-workers32 have shown that the size of capsular bag positively correlates with the axial length and negatively with the corneal power. In eyes with normal axial length 13,11 is used. In high myopia we use a large CTR.14,12 Appropriate Timing of CTR Insertion The CTR can be inserted at any time after completion of capsulorhexis. The advantage of implanting CTR before hydrodissection is that the rhexis margin is clearly visible which makes it easier to implant the ring in the bag. Implanting the CTR after hydrodissection helps break the cortical adhesions making cortical aspiration better. It can also be placed after phacoemulsification as done in our study, where it, • Keeps the bag stretched • Prevents fall back of the equatorial bag • Chances of vitreous prolapse are minimized Insertion Techniques Manual Technique

CTR can be inserted with a Mc Phersons forceps through the tunnel or paracentesis.33 A micromanipulator can assist the maneuver. The capsular bag is stable once the CTR is in place. Injector Technique

After the CTR is loaded in the injector, only the curved tip is exposed. The injector is directed laterally beneath the anterior capsule leaf and injected. Limitations • If the CCC is torn, implanting a tension ring may extend the tear and dislocate it. • If the posterior capsule is torn prior to inserting a tension ring there is a likelihood of extension of the tear with resultant posterior dislocation of the ring. • Severely subluxated lens >270º zonular dialysis.

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Complications • An open capsular tension ring against capsular contraction forces may consequently collapse resulting in capsular contraction • Entanglement of the ring within the bag • Damage to zonules

AECS Illumination

• • • •

Extrusion of the ring Dislocation of CTR IOL tilts Pigment dispersion.

Comparison of Different Types of Capsular Tension Rings30 Types

Material

Design

PMMA • Open circular filament Capsule Tension Ring Eyelet at both free ends Round or oval shaped cross section

Cionni Ring

Functions • Maintains circular contour of capsular bag. • Enhances safety and efficacy during phaco and IOL surgery. • Reduces capsular bag contraction. • Provides support to the bag avoiding IOL decentration. • May inhibit lens epithelial cells migration to posterior capsule.

PMMA • Single or double loop hooks Manages profound zonular loss. • Suture eyelet on free end of hook scleral wall fixation

Aniridia Ring PMMA • Conventional ring with an iris diaphragm. • Black projections stemming from the ring

Manages loss or absence of iris tissue (coloboma).

Capsule Tension Segment

• To stabilize the capsule in case of damaged or missing zonules. • To stabilize the capsule in case of myopia. • To prevent subluxation of IOL. • For circular expansion of the capsular bag. • To prevent capsular fibrosis.

PMMA • It’s a partial ring with a fixation hook for temporary or permanent fixation

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References 1. John Heckenlively, MD, Cataract surgery in Retinitis Pigmentosa patients. Ophthalmology Aug. 1982; Vol. 89, No 8:880-882. 2. Role of capsule tension ring in preventing capsule contraction JCRS June 2000; Vol.26:791-792. 3. H Jackson, D Garway – Health, Outcome of cataract surgery in patients with Retinitis Pigmentosa. BJO 2001; 85:936 – 938. 4. Milind V Pande et al, In Vitro human lens epithelial cell proliferation on the anterior surface of PMMA intraocular lenses. BrJO 1996; 80:469 – 474. 5. Priscilla Arnold MD, Anterior Capsular Contraction. Ophthalmology 2007. 6. Ken Hayashihi, MD, Hideyuki Hayashi, MD. Effect of anterior capsule contraction on visual function after cataract surgery JCRS Nov.2007; Vol.33:1936 – 1940. 7. Aldo Caporossi, MD, Fabrizio CAsprini, MD, Gian Marco Tosi, MD. Histology of Anterior Capsule Fibrosis following Phacoemulsification. JCRS, Oct. 1998; Vol. 24: 1343 – 1346. 8. Okihiro Nishi MD, Kayo Nishi MD, Intraocular lens encapsulation by shrinkage of the capsulorhexis opening. JCRS July 1993; Vol. 19; 544 – 545. 9. Howard V Gimbel, MD, Thomsas Neuhann, MD. Development, Advantages and method of the continuous circular capsulorhexis technique. JCRS Jan. 1990; Vol.16: 31 – 37. 10. Tae Kyung Park MD, Sung Kun Chung, MD. Changes in the areas of the anterior capsule opening after IOL implantation, JCRS 2002; 28: 1613 – 1617. 11. Werner L, Pandey SK, Escobar – Gomez M, Visessook N. Anterior capsule opacification; a histopathological study of comparing different IOL styles. Ophthalmology 2000; 107: 463 – 471. 12. M. Gonvers, M. Sickenberg, G. Van Melle, Change in capsulorhexis size after implantation of three types of intraocular lenses. JCRS March 2006; Pg. 231 – 237. 13. Lilliana Werner MD, Suresh K. Pandey, MD, David J. Apple MD, Anterior Capsular Opacification. Opacification Sep. 2001; Vol. 108, No.8: 1675 – 1681. 14. Hayashi H, Hayashi F, Hayashi K, Nakao F, Reduction in the area of the anterior capsule opening after Polymethyacrylate, Silicone, Soft Acrylic Intraocular lens implantation. American Journal of Ophthalmololgy 1997; 123: 441-447. 15. Wallin TR, Hinckley M, Nilson C, Olson RJ, A clinical comparison of single piece and three piece truncated hydrophobic acrylic intraocular lenses. American Journal of Ophthalmology 2003; 136: 614 – 619. 16. Choun Ki Joo MD, Jeong – Ah Shin MD, Capsule opening contraction after continuous curvilinear capsulorheis and intraocular lens implantation. JCRS June 1996; Vol. 22: 585 – 589. 17. Rachipalli R Sudhir, Srinivas, Capsulorhexis phimosis in retinitis pigmentosa despite capsule tension ring implantation. JCRS Oct. 2007; Vol.27: 1691 – 1693. 18. James A. Davison, MD, Capsule contraction syndrome. JCRS Sept.1993; Vol.19: 582 – 588. 19. Hayashi H, Hayashi F, Hayashi K, Nakao F, Area reduction in the anterior capsule opening in eyes of Diabetic Mellitus Patients. JCRS 1998; 24 : 1105 – 1110. 20. Hayashi H, Hayashi K, Nakao F, Hayashi F, Anterior capsule contraction and intraocular lens dislocation in eyes with pseudoexfoliation. BJO 1998; 82: 1429 – 1432. 21. Steven O Hansen, MD, Alan S Crandall, MD, Progressive constriction of the anterior capsule opening following intact capsulorhexis JCRS Jan. 1993; Vol. 19; 77 – 82.

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22. Stephen Sacu, MD, Rupert Menapacae, MD, Effect of anterior capsule polishing of fibrotic capsule opacification JCRS 2004; Vol. 30:2322-2327. 23. Sunil P Deokule, Subhanjan S. Mukerjee, Neodymium: Yag laser anterior capsulotomy for capsule contraction syndrome. Ophthalmology surgery, lasers and imaging March April 2006; Vol.37 No.2:99 – 105. 24. John Heckenlively, MD, Frequency of posterior subcapsular cataract in the Heriditary retinal degeneration. American journal of ophthalmology; Vol. 93: 733 – 738. 25. Nishi O, Nishi K, Fujisawa T et al, Effect of Cytokines on the proliferation and collagen synthesis by human cataract lens epithelial cells. BJO 1996; Vol. 80, 63-68. 26. Satoshi Kato MD, Toshikazu Suzuki MD, Yoshie Hayashi MD, Risk factors for contraction of the anterior capsule opening after cataract surgery. JCRS Jan. 2002; Vol. 28: 109 – 112. 27. Wataru Kimura MD, Shigeki Yamanishi MD, Tohru Kimura MD, Measuring the Anterior capsule opening after cataract surgery to assess the capsular shrinkage. JCRS Sep.1998; Vol. 24: 1235 – 1238. 28. Paolo Lanzetta, MD; Raffella Gortana Chionini, MD, Uses of capsule tension ring in phacoemulsification indication and technique. IJO Dec. 2002; Vol. 50: 333 – 337. 29. Howard V. Gimbel, MD; Ran Sun, MD, Clinical application of capsular tension ring in cataract surgery ophthalmic surgery and lasers, Jan / Feb 2002; Vol.33: 44-53. 30. Rupret menapace, MD, Oliver Find MD, Michael Georgopoulos MD. The capsule tension ring: Design, application and technique. JCRS June 2000; Vol. 26: 898 – 911. 31. Khalid Waheed, FRCS, Haralabos Eleftheriadis, MD. Anterior capsular phimosis in eyes with capsule tension ring JRCS Oct.2001; Vol.27:1688-2001. 32. Sabine Kurz, MD, Frank Krummenauer, Ph.D, Philipp Hacker, MS. Capsular Bag Shrinkage after implantation of a capsular bending or capsule tension ring. JCRS Oct.2005; Vol. 31: 1915 – 1920. 33. Paolo Lanzetta, MD; Raffella Gortana Chinodini, MD. Uses of capsule tension ring in phacoemulsification indication and technique. IJO Dec.2002; Vol. 50: 333 – 337.