LENS SUBLUXATION AND ITS=20 MANAGEMENT

&n= bsp; &nb= sp; &nbs= p; =20 Dr. Kasturi Bhattacharjee MS, = DNB,FRCSEd

&n= bsp; &nb= sp; &nbs= p; = ; =20 SRI SANKARADEVA NETHRALAYA,

&n= bsp; &nb= sp; &nbs= p; =20 &n= bsp;BELTOLA,=20 GUWAHATI,ASSAM

Ectopia=20 lentis is defined as displacement or malposition of the crystalline lens = of the=20 eye. Though the term Ectopia lentis was introduced by Stellwag in=20 1856¹ , the first description of the dislocated lens was = given in=20 1749 by Berryat . When=20 the crystalline lens lies completely outside the patellar fossa it is = referred=20 as dislocation or = luxation of lens=20 whereas subluxation is considered when the lens is partially displaced = but=20 contained within the lens space.

ETIOPATHOGENESIS

Degree of=20 zonular disruption or dysfunction, regardless of the cause, determines = whether=20 the lens is subluxated or luxated. With the latter, the entire lens may = be in=20 the anterior chamber (anterior luxation) or may fall posteriorly into = the=20 vitreous cavity (posterior luxation). Subluxated lens may be tilted or = displaced=20 slightly in anterior or posterior direction.

Clinical=20 consequences of ectopia lentis are related to the position or location = of the=20 lens. Anteriorly dislocated lens may lead to secondary or pupillary = block=20 glaucoma which could be painful and potentially blinding. Corneal = endothelial=20 damage and decompensation may follow an anteriorly luxated lens-corneal = touch.=20 Cataract and phacolytic uveitis are other sequelae of a luxated lens. = Retinal=20 detachment is commoner in patients with heritable ectopia lentis as in = Marfan=92s=20 Syndrome and homocystinuria in about 10% of cases.

Children with=20 heritable ectopia lentis may have a high incidence of amblyopia and = strabismus=20 due to early visual disturbances usually anisometropia.

&n= bsp; &nb= sp; =20

Fig.=20 1: Superotemporal lens = subluxation

Fig.=20 2: : Superior lens=20 subluxation

Lens=20 displacement can be best studied by classifying the condition into = heritable,=20 acquired and traumatic.

HERITABLE ECTOPIA = LENTIS=20

Marfan=92s=20 Syndrome : Described = by Marfan=20 in 1896², this syndrome is characterized by a triad of = skeletal,=20 cardiovascular and ocular anomalies. This condition has an autosomal = dominant=20 heredity with variable expressivity, without any racial or ethnic = predilection=20 ³.The cardiovascular abnormalities include atrial dilatation, = mitral=20 regurgitation and dissecting aneurysms. However mental retardation is = not seen=20 in Marfan=92s Syndrome.

3D"Text It=20 is nearly always bilateral and symmetrical, usually superior and = temporal,=20 although variations are not infrequent (Fig.3) Zonular attachments are = intact=20 but stretched. The iris dilator muscle hypoplasia results in miotic = pupils with=20 poor response to mydriatics. The patients may be highly myopic, due to = both the=20 lenticular and axial components⁵. Gonioscopy may reveal = pectinate=20 ligaments, dense iris processes, peripheral mounds of iris tissue and a = broad=20 trabecular meshwork¹.

The patients=20 present with variable degrees of optical problems and refractive errors. = Bilateral amblyopia may ensue due to delayed and inadequate refraction.. = Children may rarely present with open angle glaucoma. Pupillary block = and angle=20 closure glaucomas are reported with luxation of the lens into anterior = chamber.=20 Associated retinal detachment has also been reported.

Homocystinuria : This is an = autosomal=20 recessive disorder involving an inborn error in the metabolism of = sulphur=20 containing amino acids, most importantly methionine, and characterized = by=20 excessive urinary excretion of homocystine. There is deficiency of the = enzyme=20 cystathione synthetase. Zonular fibres of the lens normally have a high=20 concentration of cysteine. Deficiency of the same in homocystinuria = causes the=20 zonules to be brittle.

Like Marfan=92s=20 syndrome, this condition also presents with skeletal, cardiovascular and = ocular=20 abnormalities =96 but with certain marked differences.

Cardiovascular = abnormalities=20 are more marked and often present dramatically. Blood coagulation = disorders and=20 increased platelet stickiness are responsible for thrombo-embolic = phenomena=20 occurring in almost 50% of the cases. Myocardial infarction, = cerebrovascular=20 accidents and pulmonary embolism, all have a propensity to occur at a = relatively=20 younger age and may be potentially fatal in 40% cases. Surgery and = general=20 anesthesia predispose to thromboembolism =96 a fact to be borne in mind = by the=20 ophthalmic surgeon.

In contrast=20 to Marfan=92s Syndrome, mental retardation is seen in almost 50% of the = patients=20 and tends to be progressive.

Ocular=20 anomalies like lens dislocation, occurring in almost 90%, tend to be = bilateral=20 and symmetric =96 usually inferior and nasal. It appears in infancy in = about 30%=20 and in 80% by 15 years of age. There is also a higher incidence of = associated=20 complications seen in the form of pupillary block glaucoma and retinal=20 detachment.

The diagnosis=20 of Homocystinuria can be supported by a positive Brand reaction in = urine. This=20 cyanide-nitroprusside test is used for the qualitative determination of = urine=20 cystine. Cystine is reduced to cysteine by sodium cyanide and the free=20 sulphydryl groups react with nitroprusside to produce a red purple = colour.=20 Dietary titrations by reducing methionine content and increasing = cysteine may be=20 beneficial in early cases.

Weill-Marchesani=20 Syndrome :=20 This condition has been attributed to both dominant and recessive = heredity in=20 various reports. The condition is a mesodermal dystrophy. The individual = is=20 short statured with spade-like hands and feet, a condition referred to = as=20 brachydactyly. There is overall brachymorphy with large thoraces and = stiff=20 joints.

The=20 charateristic ocular feature of microspherophakia is considered a must = for the=20 diagnosis, so much so that Weil-Marchesani Syndrome is also called as=20 spherophakia. Ectopia lentis is seen in about 50% of the cases and = occurs late,=20 usually in the early twenties. Angle anomalies and retinal detachment = have also=20 been reported in some studies⁶.

Hyperlysinemia=20 : = This is a=20 rare, recessively transmitted lysine metabolism disorder due to = deficiency of=20 the enzyme lysine alpha ketoglutarate reductase. Affected individuals = show=20 mental retardation, muscular hypotony and lax ligaments. Ocular features = include=20 microspherophakia associated with ectopia lentis in some cases.=20

Sulfite oxidase=20 deficiency=20 : This is a very rare autosomal recessive disorder of sulphur = metabolism.=20 Ectopia lentis is associated with progressive muscular rigidity and = severe=20 mental retardation. Affected individuals usually become disabled by the = age of 5=20 years.

Ehler-Danlos Syndrome : = The=20 condition, described separately by Ehler and Danlos, involves the = integument,=20 skeleton, viscera and eye.

The condition, = described=20 separately by Ehler and Danlos, involves the integument, skeleton, = viscera and=20 eye. Ocular manifestations predominate in two of the seven phenotypes, = described=20 as =91Ocular Ehler Danlos Syndrome=92 (Fragilitas Oculi). Scleral = thinning,=20 keratoconus, dislocated lens with micro- and megalocornea, strabismus, = angioid=20 streaks and retinal detachment have been documented. Hyperstretchability = of the=20 skin, hyperextensibility of the joints, hiatus hernia, gastrointestinal = tract=20 diverticuli and cardiac valvular defects are other=20 associations.

Sturge-Weber = Syndrome=20 : = This Dermato-oculo-neural = syndrome=20 described by Sturge (1879) and Weber(1922) consists of facial nevus = flammeus,=20 ipsilateral cavernous hemangioma of the choroid, glaucoma, subluxated = lens and=20 meningeal hemangiomatosis.

Moreover hereditary Ectopia lentis has also been rarely reported=20 Crouzon=92s Syndrome ,Mandibulofacial Dysostosis , Refsum = Syndrome=20 ,Conradi Syndrome, Pierie Robin Syndrome , Wildervanck syndrome = etc.

Aniridia

A = defect in=20 the PAX 6 gene on chromosome 11 is the cause of aniridia, It is a = panocular,=20 bilateral disorder. Isolated aniridia may sometimes be complicated by = ectopia=20 lentis .

Heritable=20 Isolated Ectopia Lentis : = It is rare=20 and occurs early in life. There is bilaterally symmetrical upward and = temporal=20 ectopia lentis. The condition is accredited with an autosomal dominant = heredity.=20 ( Fig.4)

Ectopia lentis et pupillae

3D"Text =20 Also referred to as Familial Ectopia Lentis, this autosomal = recessive=20 disorder is characterized by a pathological association between the lens = and the=20 pupil. The condition has often been reported as bilateral and=20 symmetrical² though asymmetrical involvement is not=20 infrequent⁷. Here both the pupil and the lens are ectopic = with the=20 pupillary displacement in the direction opposite to that of the lens. = Cataract=20 formation, glaucoma, severe axial myopia, retinal detachment and = abnormal iris=20 transillumination defects have been reported as associated features^=

7. =

ACQUIRED ECTOPIA LENTIS

Trauma=20 ( fig. 5 )=20
High=20 myopia=20
Pseudoexfoliation=20
Perforation=20 of a corneal ulcer=20
Buphthalmos=20
Coloboma=20 of iris and choroid=20
Long standing endophthalmitis=20
Mechanical=20 affect of an intraocular growth=20
Hypermature=20 cataract=20
Megalocornea=20
Retinitis=20 Pigmentosa=20
Chronic=20 uveitis=20
Spontaneous lens dislocation- = It is=20 seen in elderly individuals where progressive age-related weakening of = the=20 zonules first causes a tilting and is gradually followed by complete=20 dislocation of the lens into the vitreous and rarely into the anterior = chamber=20 (Fig.6).

CLINICAL=20 FEATURES

The common=20 presenting symptoms are painful red eye (secondary to trauma, glaucoma, = uveitis=20 etc.), monocular diplopia, decreased distant visual acuity (secondary to = astigmatism, myopia) and poor near vision due to loss of accommodative = power.=20

A = detailed=20 ocular examination should be conducted in all cases of ectopia lentis. = The most=20 important being assessment of visual function as ectopia lentis is a = potentially=20 vision threatening condition. Visual acuity varies with the degree and = location=20 of malposition of the lens; amblyopia being a common cause of preventable visual loss in = congenital=20 ectopia lentis. The other ocular examination includes evaluation of = globe=20 symmetry (e.g. strabismus, secondary to amblyopia, enophthalmos seen in = Marfan=92s=20 syndrome), measurement of corneal diameter (e.g. megalocornea associated = with=20 Marfan=92s syndrome), measurement of intraocular pressure, refraction, = slit lamp=20 examination, funduscopy (retinal detachment is a serious consequence of=20 dislocated lens) and echography (increased axial length found in = Marfan=92s=20 syndrome). Slit lamp examination should be conducted initially in = non-dilated=20 pupil¹⁰. In this way phacodonesis, iridodonesis and increased = anterior chamber depth are more apparent. However the extent of zonular = dialysis=20 and direction of lens displacement are more clearly evident in dilated = pupil.=20 Other signs usually associated with traumatic lens subluxation are = hyphema, iris=20 sphincter lesion, areflexic mydriasis, angle recession and herniation of = vitreous into the anterior chamber. All these are the direct signs of = lens=20 subluxation, which can be evaluated preoperatively. However, appearance = of=20 radial folds on anterior capsule during initiation of capsulotomy or=20 capsulorrhexis, irregular anterior chamber depth and iridic flutter = resulting=20 from inverted fluid infusion into vitreous body through the area of = zonular=20 dehiscence are some of the indirect signs of lens subluxation and are = apparent=20 intraoperatively.

MANAGEMENT

The rational=20 approach to Ectopia lentis would be to regard the eyes as sick and = priority set=20 towards preservation of the globe and vision.. Early diagnosis and = treatment of=20 ectopia lentis in childhood is important. Amblyopia is considered as the = most=20 common cause of decreased vision in ectopia lentis. Amblyopia may be = prevented=20 or minimized by appropriate refractive correction through the phakic or = aphakic=20 part of the pupil. If the edge of the subluxated lens bisects the pupil, = then=20 the phakic portion of the lens could be used for near and the aphakic = portion=20 for distant vision. Alternatively, the pupillary size can be altered to = achieve=20 optical correction. Use of miotics improves the vision with the stenopic = affect=20 and eliminates visual aberrations. The pupil may be altered by = mydriatics, laser=20 therapy or surgery to secure aphakic refractive correction¹¹. = Newer=20 surgical procedures have been tried to displace the lens from the visual = axis by=20 using YAG laser on residual zonular fibres^12,13. These = different=20 nonsurgical procedures should be tried first, especially in patients = with=20 systemic disorders like homocystinuria who are at increased risk with = general=20 anesthesia¹⁴.

Lens surgery=20 is indicated in cases with = ectopia=20 into the anterior chamber with corneal touch, alteration of visual = function,=20 associated cataract, lens-induced uveitis and recurring lens = subluxation.=20 Surgical interventions have been associated with report of incidence of = vitreous=20 loss and retinal detachment ranging from 11-30%^15,16. = Different=20 surgical techniques like discission, aspiration, intracapsular removal = and=20 inadvertent extracapsular removal have been described with surgical = complication=20 rate upto 51% in treating dislocated lens¹⁵.

The=20 introduction of automated vitrectomy has resulted in manifold = improvement in=20 surgical outcomes. Peyman et al in 1979¹⁷ and Seetner = and=20 Crawford in 1981¹⁸ first reported the management of ectopia = lentis by=20 pars plana lensectomy, demonstrating good results and fewer = complications.=20 Though the introduction of pars plana and limbal lensectomy has improved = the=20 functional and anatomical prognosis of these patients, the need to = correct=20 aphakia using contact lenses was inevitable.

The advent of=20 sophisticated surgical accessories like =91Capsular Tension Ring=92 = (CTR) and=20 advancement in surgical technologies have revolutionized the management = of subluxated lens. In 1991 Hara = et=20 el introduced the concept of the =91Equator Ring=92, =91Endo = Capsular Ring=92 (ECR)=20 or =91Capsular Tension Ring=92 to prevent capsular bag contraction = ¹⁹.=20 Although they were initially designed to prevent proliferation of the = equatorial=20 cells¹⁹, Liger et al in 1993 presented a film titled = =91 The=20 Capsular Tension Ring: A New Device for Complicated Cataract Surgery =92 = at the=20 third American International Congress on Cataract, IOL and Refractive = Surgery at=20 Seattle, Washington²⁰. Since then, many others such as Cionni = and=20 Osher²¹, =20 Gimbel²², Fine and Hoffman²³,=20 Orbigozo²⁴, = have made=20 extensive study on CTR and used it for the management of subluxated = lenses.

The advantages of CTR are manifold. It = maintains the=20 circular contour of the bag despite zonular dehiscence, prevents IOL=20 decentration and also retards the migration and proliferation of the = lens=20 equatorial cells, thereby preventing the capsular contraction = syndrome.The CTRs=20 are available in diameters of 12.5 to 14.5, compressible to 10 mm or = less. The=20 size of the CTR is estimated by measuring the corneal white-to-white = distance.=20

Though there are = different=20 designs, dimensions and materials of CTR²⁵, the standard CTR = is made=20 of PMMA and designed as open loop with eyelets at either end in order to = aid=20 manipulation .There are some situations where the standard CTR cannot = provide=20 centering of the capsular bag. In such situations of extensive zonular=20 dehiscence, the use of the modified CTR, (MCTR)²⁶, designed = by=20 Robert Cionni may be used. Here the CTR is incorporated with fixation = hook with=20 an eyelet at the free end to provide scleral fixation without violating = the=20 integrity of the capsular bag. Currently, there are three designs of = modified=20 CTR: Model 1-L has a single fixation hook, away from the insertion end of the = ring; Model 2-C has the single = fixation hook=20 near the insertion end of the ring; Model 2-L has two fixation hooks and = is very=20 useful in patients with very significant zonular weakness.

The CTR can be = inserted into the=20 capsular bag at any point after the capsulorrhexis has been completed. = The=20 rhexis must be started at the point where the zonules are intact, to = minimize=20 the traction. Rhexis is to be followed by hydrodissection, preferably = cortical=20 cleaving hydrodissection. The CTR can be introduced with smooth forceps = through=20 the main incision or through a side port corneal stab incision. A more=20 controlled insertion can be achieved by using a special injector called = the=20 Geuder Shooter. It is important to load the ring = properly=20 onto the injector.One shouldt follow the curvature of the injector with = the=20 curvature of the ring and should always load by hooking the LEFT=20 eyelet.

Fig.=20 7=20 b

Fig.=20 7=20 a

Fig.7=20 e

Fig.7=20 d

Fig.7=20 c

=20 =20

&nbs= p; = ; = =20

3D"Text

Thus, the=20 management of subluxated lens with the use of CTR during = phacoemulsification is=20 a safe surgical procedure. It enhances intraoperative safety and = decreases=20 vitreoretinal complications. Moreover, it maintains the stability of the = capsular bag and prevents IOL decentration, providing good postoperative = visual=20 rehabilitation.

REFERENCES

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Pyerite=20 RE, Mckusick VA: The Marfan=92s Syndrome: Diagnosis and Management, N = Engl J Med=20 300: 772, 1979.=20
Maumenee=20 IH: The Eye in the Marfan=92s Syndrome, Trans Am Ophthalmic Soc 79: = 684, 1981.=20
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