FP508 : Intrascleral fixation of single piece intraocular lens- a prospective study

Dr. Nagendra Shekhawat, Dr. Karishma Goyal, Prof. Kamlesh Khilnani, Dr. JITENDRA KUMAR BAGARIA

Intrascleral fixation of single piece intraocular lens- a prospective study

Planned intracapsular method of cataract extraction, [1] extracapsular cataract extraction complicated by marked zonular dehiscence or a large posterior capsular break without an intact capsulorhexis or traumatized eye, [2] Ectopia lens or pediatric lensectomies, these all resulted in an absence of capsular support, ultimately causing aphakia. Visual rehabilitation in such patients is quite challenging not only due to the visual outcome but also to the related complications in the post-operative period. Usual modalities accomplished in the past are the spectacles, contact lens or implantation of Anterior chamber IOL (ACIOL), iris fixated IOL or Scleral fixated IOL (SFIOL). [3] Spectacles & contact lens have limited use due to their complication profile. [4, 5] Then came the concept of intraocular lens implantation. [6]

The endocapsular placement is the most preferred anatomical site for IOL placement. Thus, placement of the IOL in the posterior, rather than the anterior chamber reduces the risk of damage to anterior chamber angle structures & corneal endothelium. [7] We evaluated a new technique of intrascleral fixation of three-piece IOL without the use of suture (risk of suture-induced inflammation, suture degradation and delayed IOL subluxation or dislocation due to broken suture) & glue (expensive or risk of prion infections). [8]

Material & Method

The ethical committee of the hospital approved the study. It was an Observational study included 24 patients. All aphakic patients above 12 years who were ready to give consent were included in the study. Exclusion criteria included patients with corneal opacity, retinal disorder, optic atrophy, bleeding disorder, pregnancy & those who were unwilling to give consent. Preoperative & post-operative visual acuity, Slit lamp & Fundus examination, Applanation tonometry, Keratometry, Biometry), optical coherence tomography (OCT) was done for extensive evaluation of anterior & posterior segment.

Statistical analysis- with the use of Software – IBM SPSS 19.0, Qualitative data was summarized in form of proportion. Quantitative data was summarized in form of mean and SD. The significance of difference in proportion measured by chi-square test. The significance of difference in mean measured by unpaired t-test or ANOVA whichever is appropriate. p< 0.05 was considered as significant.

Surgical technique:

Under Peribulbar anesthesia, 5.0 mm conjunctival peritomy was done at the 2 o’clock and 8 o’clock positions. Then, 2 T-shaped incisions (1.5-2 mm long) were made 1.5-2.0 mm from the limbus and depth was half of scleral thickness, exactly 180 degrees apart diagonally. An infusion cannula or anterior chamber maintainer was inserted.  To prevent interference with the creation of the T-shaped incision, infusion cannula should be positioned at 4 o’clock. Anterior vitrectomy (deep core) was performed, if necessary. Sclerotomy was done parallel to the iris at the T-shaped incision with a 23-gauge angled microvitreoretinal (MVR) knife and a scleral tunnel (3-3.5 mm long) was made parallel to the limbus at the branching point of the T-shaped incision. 2.8 mm keratome was used to make a corneal incision at 10 o’clock through which IOL, with overall diameter 13 mm and optic diameter 6 mm, was implanted with an injector; the trailing haptic was left outside the incision. The tip of the haptic was then grasped with 24/25-gauge IOL haptic gripping forceps, pulled through the Sclerotomy, and externalized on the left side. After the trailing haptic was inserted into the anterior chamber& the haptic tip was grasped with a 24/25-gauge forceps, pulled through the second sclerotomy and externalized on the right side. The haptic insertion into the anterior chamber may be difficult depending on the material or shape of the haptics, which can cause the IOL to rotate clockwise and the leading haptic to slip back into the eye. To prevent such risks, the IOL optic was pushed to the back of the iris and moved to the 2 o’clock position with a push-and-pull hook inserted through the side port at the 1 o’clock position. The tip of the haptic was subsequently inserted into the limbus–parallel scleral tunnel. A single 8-0 vicryl suture is used to fixate the haptic to the scleral bed to prevent it from shifting immediately after surgery.Scheimpflug imaging was done to evaluate proper centration of IOL. Follow up was done on 1st, 7th, 28th post-operative day, at 3 month & 6 month.

Results

The study population consisted of 24 patients (10 female & 14 male). Mean age was 58.2 years (standard deviation 11.4 year). The minimum age was 25 years while the maximum age of the patient was 75 years. Out of 24, 12 were aphakic due to complicated cataract surgery & 2 were aphakic after Intracapsular Cataract Extraction (ICCE). These cases underwent deep core anterior vitrectomy through 23-gauge pars plana route with scleral fixation in the same sitting. During anterior vitrectomy, infusion continued through anterior chamber maintainer and a single pars plana incision 3.5 mm behind the limbus was made. This allowed the flow to move in one direction from anterior to posterior making removal of vitreous more efficient. The rest of the cases included dropped IOL (4), nucleus drop (5), subluxated cataractous lens (1). In these cases, 23- gauge primary pars plana vitrectomy with 360° endolaser was done. Silicon oil was injected in required cases. Then after 4 weeks, SFIOL was implanted. In silicon filled eye SFIOL was implanted after silicon oil removal.

Change in uncorrected visual acuity (UCVA) in LOGMAR from pre-operative (1.8±0.6) value to every follow up post operatively (0.8±0.3; 0.6±0.3; 0.5±0.2; 0.5±0.2: 0.5±0.3 respectively) was highly significant (p=0.0000).

Changes in best corrected visual acuity (BCVA) in LOGMAR from preoperative (0.6±0.2) to day 1 follow up (0.6±0.3) was not significant (p=0.6842) but on next follow up (0.5±0.4) change was significant (p=0.0183) and later on every follow up (0.3±0.2; 0.3±0.2; 0.3±0.2) change was highly significant (p=0.0000).

Corneal topography (K1 & K2) & astigmatism was measured using scheimpflug imaging preoperatively (K1=43.2±2; K2=44.6±2; astigmatism=2±1.8) & on final follow up at 6 months (K1=43.3±1.8; K2=44.5±1.9; astigmatism=1.8±1.6). Changes in keratometry (K1, K2) & Astigmatism was found insignificant (p value = 0.6324, 0.4556 & 0.0510 respectively), showing that scleral tunnel made in this technique does not effect corneal astigmatism.

Complications were noted on each follow up.

On day 1, there were 1case of corneal edema due to surgical manipulations which got resolved in the next follow up, on day 7 there were 2 cases of raised Intraocular Pressure (IOP) which were managed medically. At 3 months, there was 1 case of Cystoid Macular Edema (CME) which was managed medically.

Mean IOP was 14.6±3.2 mmHg preoperatively while it was 15.00±1.7 mmHg postoperatively at 6 months. Mean IOP change from preoperative period to 6 weeks postoperative period was not statistically significant p=0.4980. Mean change in IOP from preoperative period to post op day 1 (15.9±2) (p=0.0110) and post op day 7 (16.3±4.7) (p=0.0300) was found significant as there was some case of raised IOP due to inflammation or pigment release due to maneuvering. These cases were treated medically and on next follow up their IOP came out normal.

At the end, all cases have well centered IOL with good visual acuity.

Discussion

The endocapsular placement of an Intraocular lens (IOL) is undoubtedly anatomically most preferable following successful cataract extraction as implantation of an IOL in the capsular bag provides stable fixation at a position closest to the nodal point of the eye. In eyes with insufficient or no capsular support, IOL implantation and fixation techniques are still controversial. Scleral-sutured IOLs have been popular in the past; however, to avoid the intraoperative and postoperative suture-related problems, Gabor and Pavlidis developed a sutureless technique for sulcus fixation of posterior-chamber IOL using permanent incarceration of the haptics in a scleral tunnel parallel to the limbus. [9] This method offers the postoperative axial stability of the IOL while avoiding suture-related problems. This method combines the control of a closed-eye system with the postoperative axial stability of the posterior chamber IOL. This technique has an advantage in that it can be performed in the presence of significant structural abnormalities of the anterior chamber and that it mitigates many of the adverse outcomes associated with ACIOL’s, iris fixated IOL’s and sutured scleral-fixated IOL’s.

Removal of the crystalline lens deprives the eye of the stabilizing effect of the lens-zonule barrier. When the eye moves, it acquires kinetic energy from its muscles and attachments and the energy is dissipated to the internal fluids as it stops. Thus pseudophacodonesis is the result of oscillations of the fluids in the anterior and posterior segment of the eye. The oscillations, initiated by movement of the eye, resulting in shearing forces on the corneal endothelium which may result in damage. The similar motion of the vitreous causes shearing forces which may damage the retina. [10, 11] In addition, positioning the lens closer to the rotational center of the eye, just anterior to the vitreous face, may reduce the centrifugal forces on the lens and stabilize the ocular contents, thereby decreasing the probability of complications such as iritis, CME, and retinal detachment. Another advantage of positioning the lens closer to the nodal point and center of rotation of the eye is the superior optical properties accrued by the lens in this position.  In sutured scleral-fixated IOL, there is increased chance of pseudophacodonesis due to the torsional instability of ciliary body-suture-haptic attachment while in scleral tucking of haptic there is less chance of torsional instability due to rigid ciliary body-haptic-optic attachment. [12]

Because of the overall diameter of these IOLs, we did not observe increased forces to the sclera. Scleral tunnels are well known from cataract surgery, and we would not expect scleromalacia to occur except, possibly, in cases of pre-existing inflammation (eg, Scleritis, episcleritis, rheumatoid arthritis, herpes zoster ophthalmicus). [13]

The large optics lowers the risk of clinically significant postoperative decentration. [12] Externalization of the greater part of the haptic along its curvature stabilizes the axial positioning of the IOL and thereby prevents IOL tilt. [14] Sulcus fixation of single-piece IOLs is not popular owing to postoperative complications like pigment dispersion, iris transillumination defects, dysphotopsia, elevated IOP, intraocular hemorrhage and cystoid macular edema. This is due to the fact that bulky single-piece haptics are large and thick enough to contact the posterior iris when placed in the sulcus. Also, the haptics are planar rather than angulated and therefore do not vault the optic posteriorly from the iris. [15]. Single piece Tecnis®1 foldable lenses have an offset

design. Hence, neither the optic nor haptics come in contact with theiris nor the above mentioned complications are minimized. Single piece lens haptics are sturdy, this allows easy exteriorization.

Although larger sclerotomies are required (as compared to three piece IOL), these are usually blocked completely by the thick stubby haptics; mitigating the need for suturing. However, sclerotomies can be sutured when needed.

The scleral fixation technique has evolved over time, with one of the greatest changes being the use of foldable IOL. This makes it possible to perform the entire procedure through small self-sealing incisions. This has the intraoperative advantage of having a well-formed globe throughout the surgery. It eliminates iris prolapse during IOL insertion and wound suturing and significantly decreases surgical time. This foldable IOL has postoperative advantages of having fewer complications associated with larger wounds, such as postoperative wound leak and shallow anterior chamber, as well as decreases astigmatism.

We believe this method of IOL implantation is appropriate for eyes with deficient or absent posterior capsule and this can be performed easily with the available IOL designs, instruments and with less surgical time.

Based on our current experience and published results, sutureless posterior chamber IOL implantation is an effective alternative in the eyes with deficient capsule support.

References

1. Apple DJ, Mamalis N, Loftfield K, Googe JM, Novak LC, Kavka-Van Norman D et al. Complications of intraocular lenses. A historical and histopathological review. Surv Ophthalmol. 1984;29:1–54.
2. Lundström M, Brege KG, Florén I, Lundh B, Stenevi U, Thorburn W.: Postoperative aphakia in modern cataract surgery: part 2: detailed analysis of the cause of aphakia and the visual outcome. J Cataract Refract Surg. 2004 Oct;30(10):2111-5.
3. Alpar J-“Present state of management of aphakia. Future of spectacles and contact lenses”. Indian J Ophthalmol. 1989 Apr-Jun;37(2):54-7
4. Dabezies OH Jr., Defects of vision through aphakic spectacle lenses. Ophthalmology. 1979 Mar;86(3):352-79.
5. Ferris RL. Complications associated with aphakic contact lenses. Ophthalmology. 1979 Jun;86(6):1120-3.
6. Por YM, Lavin MJ. Techniques of intraocular lens suspension in the absence of capsular/zonular support. Surv Ophthalmol 2005; 50:429–462
7. Apple DJ, Brems RN, Park RB, Norman DK, Hansen SO, Tetz MR, Richards SC, Letchinger SD. Anterior chamber lenses. Part I: Complications and pathology and a review of designs. J Cataract Refract Surg. 1987 Mar; 13(2):157-74.
8. Durak A, Oner HF, Kocak N, et al. Tilt and decentration after primary and secondary transsclerally sutured posterior chamber intraocular lens implantation. J Cataract Refract Surg27:227-32,2001.
9. Gabor SGB, Pavlidis MM. Sutureless intrascleral posterior chamber intraocular lens fixation. J Cataract Refract Surg 2007; 33:1851–1854
10. Jacobi KW, Jagger WS. Physical forces involved in pseudophacodonesis and iridodonesis. Albrecht Von Graefes Arch KlinExp Ophthalmol. 1981;216(1):49-53.
11. Binkhorst CD. Corneal and retinal complications after cataract extraction. The mechanical aspect of endophthalmodonesis. Ophthalmology. 1980 Jul;87(7):609-17
12. Kumar DA, Agarwal A, Agarwal A, Prakash G, Jacob S. Glued intraocular lens implantation for eyes with defective capsules: A retrospective analysis of anatomical and functional outcome. Saudi J Ophthalmol 2011;25:245-54.
13. Mamalis N, Johnson MD, Haines JM, Teske MP, Olson RJ. Corneal-scleral melt in association with cataract surgery and intraocular lenses: a report of four cases. J Cataract Refract Surg 1990; 16:108–115
14. Teichmann KD, TeichmannI A. The torque and tilt gamble. J Cataract Refract Surg 1997;23:413-8
15. David F Chang, Samuel Masket, Kevin M. Miller, Rosa Braga-Mele, Brian C. Little, Nick Mamalis et al: Complications of sulcus placement of single-piece acrylic intraocular lenses. Recommendations for backup IOL implantation following posterior capsule rupture. J Cataract Refract Surg 2009;35:1445-1458.