The surgical correction of astigmatism has evolved over the past 15 years. Astigmatic correction included incisional surgeries and then excimer laser surgery. Now astigmatism management includes other modalities such as intraocular toric implants, both phakic and Pseudophakie. The evolution of these different modalities in astigmatic correction has widened the refractive surgical horizon and continues to enhance astigmatic correction.1
Years ago, Worst and Fechner introduced the iris claw anterior chamber lens for the correction of high myopia with initially satisfactory results.2 The implantation of the Artisan phakic intraocular lens (PIOL) (iris-claw) (Ophtec BV, Groningen, The Netherlands) has shown good results in high myopia and hyperopia with a low complication rate.3"6 Reports published using corneal techniques such as laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and holmium laser thermokeratoplasty for correcting high astigmatic errors were not satisfactory in these patients; in addition, these procedures led to significant optical aberrations and induced more irregular astigmatism.79 Corneal refractive surgery remains limited in patients with high myopia and hyperopia, and phakic toric implants may be a better alternative.
The results and complications of implantation of a toric phakic iris-claw intraocular lens (Artisan) in the correction of astigmatism are presented. The aim of this study was to investigate the safety, stability, predictability, and complications of implanting such lenses in patients with high degrees of astigmatic refractive errors.
PATIENTS AND METHODS
Twenty-five eyes (20 patients) were implanted with an Artisan toric PIOL in this prospective consecutive study. Mean patient age was 34.8±1.4 years (range: 24 to 58 years). Patients were divided into three groups. Group 1 comprised patients with myopic astigmatism (8 eyes), mean sphere 6.4±4.6 diopters (D) and mean cylinder 4.3 ±0.7 D. Group 2 included patients with hyperopic astigmatism (9 eyes), mean sphere 3.6±1.0 D and mean cylinder 4.6±0.8 D. Group 3 comprised patients with mixed astigmatism (8 eyes), mean sphere 5.8±2.1D and mean cylinder 4. 4 ±1.5 D.
All eyes included in this study had primary (16 eyes) or residual (9 eyes) astigmatism induced by previous corneal refractive procedures. Previous corneal refractive procedures included penetrating keratoplasty, incisional corneal surgery, and LASIK. The eyes included in this study were not amenable to other methods for correction of their refractive error due to marked reduction of corneal thickness and repeated corneal procedures.
The toric design of the phakic iris claw lens, Artisan toric PIOL, was implanted in all eyes. This lens is biconcave and made of polymethylmethacrylate with an ultraviolet-absorbing Prespex. It has an overall 8. 5 -mm diameter, 5 -mm lens width, 5 -mm optic zone, 1.04-mm height, and a 0.9 3 -mm thickness. The Artisan toric PIOL has two models. Model A has a 0° cylinder axis corresponding to the main lens axis, which runs through the claws. This model is implanted in cases where the cylinder axis to be corrected is between 0° and 45° or in cases with astigmatic meridians between 135° and 180° if the surgeon prefers a superior approach. Model B has its cylinder axis at 90°. The cylinder axis is perpendicular to the main lens axis, which runs through the claws. It is implanted when the cylinder axis to be corrected is between 45° and 135° if the surgeon prefers a superior approach.
When performing a temporal approach, the previous two models could be used but in the reversed manner - model A for correction of astigmatism between 45° and 135° and model B for correction of astigmatism between 0° and 45° or in cases with astigmatic meridians between 135° and 180°.
The power of the lens was calculated by property software based on the Van der Heijde formula (Ophtec BV).6 The parameters used for its calculation were manifest refraction, anterior chamber depth, and keratometry. Anterior chamber depth was measured with an ultrasonic biometer (Ocuscan; Alcon Laboratories, Ft Worth, Tex). Keratometry was estimated from the tangential map of the Corneal Topography (EyeSys Technologies, Houston, Tex), measured at the 3-mm optical zone.
After providing the appropriate information concerning the possible outcome, limitations, different treatment modalities, and complications, patients chose to receive the Artisan toric PIOL to improve their uncorrected visual acuity. All patients read and signed a written informed consent. Exclusion criteria for implantation of the Artisan toric PIOL were history of uveitis, glaucoma, intraocular pressure >20 mmHg, cataracts, anterior or posterior synechia, corneal dystrophy, central endothelial cell count <2000 cells/mm2, and anterior chamber depth <2.8 mm. Hyperopic eyes with abnormal iris bulge may be at higher risk for postoperative inflammation.
The study protocol was done according to the Helsinki Declaration.10 A complete preoperative ocular examination was performed in all patients. Corneal endothelial cell density (cells/mmp 2) was calculated using contact wide-field specular microscope (Konan SP-5500; Konan Camera R&I Ine, Honyo, Japan) with a 40 X magnification cone.
Snellen charts were used to measure the visual acuity and later transformed to the equivalent feet values. Evolution of the inflammatory response and corneal endothelial cell studies were performed at regular intervals during follow-up at 1, 3, and 6 months. Corneal astigmatic changes induced by the surgical procedure were analyzed by vector analysis of the keratometric values measured at the 6-mm optical zone.
The procedure was performed under peribulbar anesthesia using 8 mL of bupivacaine 0.75% and lidocaine 2% with 1 cc of hyaluronidase. Honan Balloon (Lebanon Corp, Lebanon, Ind) was used for at least 20 minutes before surgery. Pupillary miosis was maintained using one drop of pilocarpine 2% (Isopto Carpine 2%; Alcon-Cusi, Barcelona, Spain) 30 minutes before surgery to prevent damage to the natural lens. If necessary, an intraoperative miotic solution could be injected into the anterior chamber constricting the pupil to facilitate lens centration. Astigmatic marker (Katena, Denville, NJ) is used to mark the astigmatic axis selected for lens implantation using slit-lamp microscopy, not in the supine position, to avoid any possible cyclotorsion or rotation movement of the eye.
Two clear corneal 1.4-mm self-sealed incisions were performed at the indicated axis, 2 mm away from the limbus and directed towards the peripheral iris followed by filling the anterior chamber with an ophthalmic viscosurgical device (Healon; Pharmacia, Upsala, Sweden). The main incision (6 mm) was performed at the superior corneal limbus centered at the perpendicular axis to the selected axis for lens implantation using a 1-mm MVR blade (Sharpoint; Surgical Specialties Corp, Reading, Pa). A peripheral iridotomy was done using Alió forceps and scissors (ASICO, Westmont, 111). Additional amounts of Healon were injected and the lens was inserted through the corneal incision using specially designed implantation forceps (Artisan; Ophtec) and rotated to its proper position using a Lester Hook (Katena).
Artisan lens-forceps was introduced through the main corneal incision to fix and center the lens optic over the pupil. Through the stab incision, with a specially designed enclavation iris-forceps (Alió iris forceps; ASICO), a small fold of iris was engaged and grabbed for enclavation in the lens claw. After completing the first enclavation, instruments were removed and the hands were switched to enclave the other claw to the iris.
The ophthalmic viscoelastic device was removed and the main incision was sutured accordingly using single figure of eight 10/0 suture. Postoperative regimen included the instillation of cyclopentolate 1% (AlconCusi) two drops immediately after surgery and one drop daily for 5 days. Dexamethasone with polymyxin B and neomycin (Maxitrol; Alcon-Cusi) drops were instilled 4 times a day for 15 days, and diclofenac drops (Voltaren; Ciba Vision, Barcelona, Spain) were instilled 3 times a day for 1 month. Oral carbonic anhydrase inhibition (Edemox; Chiese-Wasermann, Barcelona, Spain) was prescribed for the first 24 hours at a dose of 250 mg/8 h with potassium supplementation. During the first 6 months, the sutures were removed when induced astigmatism of >1.0 D was noted; however, if no induced astigmatism was noted, sutures were removed at the end of the first year. To evaluate postoperative inflammation, a previously reported clinical grading system was used.11
Sixteen of 25 eyes completed 1-year follow-up. The data concerning the standards for reporting the outcome of refractive surgery procedures, as safety, efficacy, and predictability, were analyzed at 6-month follow-up as previously described.12
Statistical analysis of the results was performed using SPSS/8.0 for Windows (Microsoft Corp, Redmond, Wash). Results were expressed as mean±standard deviation and statistically significant differences between data sample means were determined by using Student t test and paired sample t test. The comparison between the different groups was carried out using analysis of variance. The astigmatic data were analyzed using vector analysis. The safety index is equal to the ratio mean postoperative best spectacle-corrected visual acuity (BSCV A)/mean preoperative BSCVA. The efficacy index is equal to the ratio mean postoperative uncorrected visual acuity (UCVA)/mean preoperative BSCVA. A P value of 0.05 was considered significant.
Refraction data of all groups are presented in Table 1. The change in sphere, cylinder, and spherical equivalent refraction in the myopic astigmatism group at the end of 6 months was statistically significant (paired samples t test, P=.005, P=.001, and P=.02, respectively). In the hyperopic astigmatism group, the change in sphere, cylinder, and spherical equivalent at 6 months was statistically significant (paired samples t test, P=.002, P=.000, and P=.000, respectively). In the mixed astigmatism group, the change in sphere, cylinder, and spherical equivalent refraction at 6 months was statistically significant (paired samples t test, P=.002, P=.014, and P=.002, respectively).
Table 2 presents the visual acuity reported in decimal values ± standard deviation and Snellen fraction. In the myopic astigmatism group, the changes in UCVA and BSCVA were statistically significant (paired samples t test, P=. 005 and P=. 000). In this group, seven eyes gained ≥1 line of BSCVA and only one eye lost 1 line ofBSCVA(Table 3).
In the hyperopic astigmatism group, the changes in UCVA and BSCVA were not statistically significant (paired samples t test, P=. 199 and P=. 89). In this group, three eyes gained ≥1 line of BSCVA and one eye lost 1 line of BSCVA. Two eyes lost 2 lines of BSCVA, which was expected as they underwent multiple corneal refractive procedures that induced irregular astigmatism (Table 3).
In the mixed astigmatism group, the changes in UCVA and BSCVA were statistically significant for UCVA but not BSCVA (paired samples t test, P=.007 and P=.129). In this group, four eyes gained ≥1 line of BSCVA and no eyes lost any lines of BSCVA (Table 3).
SAFETY AND EFFICACY
The safety and efficacy indices of the procedure for all groups are plotted in the Figure. The safety indices were 1.6 for the myopic astigmatism group, 1.3 for the hyperopic astigmatism group, and 1.3 for the mixed astigmatism group (Table 3). The efficacy indices were 1.2 for the myopic astigmatism group, 1.0 for the hyperopic astigmatism group, and 1.0 for the mixed astigmatism group (Table 3).
Refractive Data with the Implantation of Artisan Toric PIOL
In the mixed astigmatism group, 5 (62.5%) of 8 eyes were within ±0.5 D of the intended correction. In the hyperopic astigmatism group, 4 (44.4%) of 9 eyes were within ±0.5 D of the intended correction. In the mixed astigmatism group, 6 (75%) of 8 eyes were within ±0.5 D of the intended correction.
In the myopic astigmatism group, 6 (75%) of 8 eyes were within ±1.00 D of the intended correction. In the hyperopic astigmatism group, 7 (77.8%) of 9 eyes were within ±1.00 D of the intended correction. In the mixed astigmatism group, 7 (87.5%) of 8 eyes were within ±1.00 D of the intended correction.
Postoperative inflammation was within the expected amount of any anterior segment postoperative inflammation. No case had significant intraocular inflammation or uveitis.
CORNEAL ENDOTHELIAL CELL COUNT
The preoperative mean cell density was 2797 ±288 cells/mmp 2 (range: 2125 to 3155 cells/mmp 2). After surgery, the percentage of endothelial cells lost during follow-up was 11.1%. Follow-up at 1 month postoperatively showed a mean cell density of 2543 ±224 cells/mmp 2 (range: 2022 to 2866 cells/mmp 2). At 6 months postoperatively, the mean cell density was 2 548 ±441 cell/mmp 2 (range: 1927 to 3580 cells/mmp 2).
Statistically significant differences in mean endothelial cell density were noted between the preoperative values and 6-month postoperative values (P<.02; paired samples t test), indicating that the cause of this loss was related to the surgical trauma.
HALOS AND GLARE
Fixation of the lens by enclavating part of the midperipheral iris to the claw allowed free pupillary movement with the IOL in place. Moderate halos and glare were reported at night in two eyes that previously underwent refractive corneal procedures. The halos and glare were decreasing as reported by the patients at last follow-up.
Visual Acuity Data With the Implantation of Artisan Toric PIOL*
PUPIL DEFORMATION, IOL DECENTRATION, AND OTHER COMPLICATIONS
None of the eyes included in the study showed pupil deformation or clinically significant IOL decentrati on during follow-up.
None of the reported complications that could occur following implantation of PIOLs including severe endothelial loss, wound leakage, corneal decompensation, pupillary block, cataract formation, inflammatory lens deposits, or retinal detachment,13 were reported in the eyes included in this study. One (7%) eye experienced shadow images (transient diplopia) during follow-up that resolved spontaneously and did not require further management.
Corneal diseases, ocular trauma, and surgical procedures might induce secondary astigmatism.1 Astigmatism has a multifactorial etiology and can arise from the cornea, lens, and retina.1 High degrees of refractive errors are becoming more difficult to correct both surgically and optically with glasses or contact lenses than low errors including both myopic and hyperopic refractive errors.14
Among the surgical options to treat astigmatism are astigmatic keratotomy,15-17 limbal relaxing incisions,18 and LASIK, which is able to treat only moderate degrees of compound or simple myopic or hyperopic astigmatism.19 Other procedures such as astigmatic keratotomy and laser thermokeratoplasty have a limited ability and are only used to treat low degrees of astigmatism.2023 Photorefractive keratectomy was used to treat low to moderate degrees of astigmatism but with the risk of developing corneal haze and regression after the procedure.2425 Performing LASIK for management of compound and mixed high astigmatism is still under investigation. Authors have reported that LASIK is not highly beneficial in managing these high astigmatic errors although it provides better accuracy, quick visual recovery, and less regression.26
Safety Data With the Implantation of Artisan Toric PIOL
Other surgical techniques to correct high degrees of astigmatism include the closed system surgical technique and the spreader device, which allow safe implantation of the iris supported claw lens, as described by Krumeich et al.27
Krumeich et al28 described an improvement of a technique for circular keratotomy, which included trephining a 7-mm diameter of the astigmatic cornea to a depth of 300 pm then deepening the trephination with a diamond knife to 550 pm over the steeper semimeridians. The amount of astigmatic correction and extent of deepening were controlled intraoperatively with a keratoscope using no sutures, with the ability to correct up to 10.00 D of astigmatism.28
Another alternative for astigmatic correction is implantation of PIOLs containing cylindrical elements to correct the existing astigmatism while correcting the spherical error. Budo et al29 reported the safe use of Artisan lenses. Tehrani and Dick30 reported the use of Artisan toric intraocular lenses to correct corneal astigmatism in a phakic eye that underwent penetrating keratoplasty to manage decompensated keratoconus with BSCVA of 20/32. In contrast to the keratorefractive option, minor manipulation on the allograft can be expected.
Dick et al31 reported the use and safety of Artisan toric lens implantation for management of astigmatism in 70 eyes. Complications reported included postoperative wound leak in one (1.4%) eye, low intraocular pressure (4 to 8 mmHg), flattening of the anterior chamber requiring a suture closure of the incision, and a 15° deviation of the lens from the target axis in one (1.4%) eye, in which repositioning was done 1 week postoperatively. The final position of the lens was achieved with only 1° deviation from the target axis and the patient's refraction was emmetropic at the end of follow-up.31 The authors reported pronounced iris pigments on the optic of the Artisan PIOL in one (1.4%) eye, mild photic phenomena postoperatively in three (4.3%) eyes, and moderate glare in one (1.4%) eye.31 According to Dick et al,31 halos and glare remained with an average of 5.7% and were related to poor centration of the lens or relatively large iridectomy.
Figure. Scattergrams show safety and efficacy of Artisan toric PIOLs 6 months postoperatively in eyes with A) myopic astigmatism (group 1), B) hyperopic astigmatism (group 2), and C) mixed astigmatism (group 3). BSCVA = best spectaclecorrected visual acuity, UCVA = uncorrected visual acuity
Certain precautions are recommended to avoid or decrease the incidence of complications such as iritis and lens decentration that might occur with Artisan toric PIOLs. Preoperative gonioscopy is important to evaluate the iris configuration, excluding cases of abnormal iris insertion or peripherally shallow anterior chamber. Surgical attention should be paid during enclavation to minimize trauma to the iris during lens implantation and assure a patent iridotomy. Other precautions include reducing intraocular pressure preoperatively either digitally or with a compressing device and assuring lens centration and claw positioning not too close to the iris root without causing excessive tension on the iris and iris root (patients with short white-to-white measurements may not be good candidates). Scheduling postoperative examinations more frequently, anti-inflammatory drops for 4 to 6 weeks, and meticulous examinations are also important.
The Artisan toric PIOL can be used safely to treat astigmatism either as a primary procedure or after a previous corneal surgery. It seems that patients who underwent previous multiple refractive procedures may occasionally develop irregular astigmatism. This problem may be due to induction of astigmatism by the relatively large incision required to implant the Artisan toric lenses. A foldable toric iris -claw lens might be the best solution to overcome the problem of induced astigmatism related to the incision size.
1. Raviv T, Epstein RJ. Astigmatism management. Int Ophthalmol Clin. 2000;40:183-198.
2. Worst JGF, Van Der Veen G, Loss LI. Refractive surgery for high myopia. The Worst-Fee hner biconcave iris claw lens. Documenta Ophthalmologics 1990;75:335-341.
3. Alió JL, De la Hoz F, Ismail MM. Subclinical inflammatory reaction induced by phakic anterior chamber lenses for correction of high myopia. Ocular Immunology and Inflammation. 1993;1:219-223.
4. Alió JL, S ay ans JA, Chip ont E. Flare-cell meter measurements of inflammation after uneventful cataract surgery with intraocular lens implantation. J Cataract Refract Surg. 1997;23:935-939.
5. Alió JL, De la Hoz F, Pérez-Santonja JJ, Ruiz-Moreno JM, Quesada JA. Phakic anterior chamber lenses for the correction of myopia: a 7-year cumulative analysis of complications in 263 cases. Ophthalmology. 1999;106:458-466.
6. Alió JL, Mullet E, Shalaby A. Artisan phakic iris claw intraocular lens for high primary and secondary hyperopia. J Cataract Refract Surg. 2002;18:697-707.
7. Alió JL, Ismail MM, Art ola A, Pérez-Santonja JJ. Correction of hyperopia induced by photorefractive keratectomy using noncontact Ho: YAG laser thermal keratoplasty. J Refract Surg. 1997;13:13-16.
8. Fyodorov SN, Durnev VV. Surgical correction of complicated myopic astigmatism by means of dissection of circular ligament of the cornea. Ann Ophthalmol. 1981;13:115-118.
9. Koch DD, Abarca A, Villarreal R, Menefee R, Kohnen T, Vassiliades A, Berry M. Hyperopia correction by non-contact holmium: YAG laser thermal keratoplasty. Clinical study with twoyear follow-up. Ophthalmology. 1996;103:731-740.
10. Ethical principles for medical research involving human subjects. 52nd World Medical Association General Assembly; October 2000; Edinburgh, Scotland.
11. Nussenblatt RB, Tabbara K, Ben Ezra D, Timonen P, Forrester JV. Uveitis Scoring System. Berlin, Germany: Spring er -Ver lag; 1991:1-13.
12. Koch DD, Kohnen T, Obstbaum SA, Rosen ES. Format for reporting refractive surgical data. J Cataract Refract Surg. 1998;24:285-287.
13. Ruiz-Moreno JM, Alió JL, Pérez-Santonja JJ, de la Hoz F. Retinal detachment in phakic eyes with anterior chamber intraocular lenses to correct severe myopia. Am J Ophthalmol. 1999;127:270-275.
14. Dart JK. Diseases and risks associated with contact lenses. Br J Ophthalmol. 1993;77:49-53.
15. Price FW, Grene RB, Marks RG, Gonzales JS. Astigmatism reduction clinical trial: a multicenter prospective evaluation of the predictability of arcuate keratotomy. Evaluation of surgical nomogram predictability. ARC-T Study Group. Arch Ophthalmol. 1995;113:277-282.
16. Pulaski JP. Transverse incisions for mixed and myopic idiopathic astigmatism. J Refract Surg. 1996 ;22:307-312.
17. Kwitko ML, Jovkar S, Yan H, Rymer S. Arcuate keratotomy to correct naturally occurring astigmatism. / Cataract Refract Surg. 1996;22:1439-1442.
18. Gills JP, Gayton JL. Reducing pre-existing astigmatism. In: Gills JP, ed. Cataract Surgery: The State of the Art. Thorofare, NJ: SLACK Incorporated; 1998:53-66.
19. Shah S. Photo -astigmatic refractive keratectomy - the cure of astigmatism. Ophthalmology. 1999;106:2045-2046.
20. Werblin TP. Why should refractive surgeons be looking beyond the cornea? J Refract Surg. 1999;15:357-376.
21. Neumann AC, Sanders D, Raanan M, DeLuca M. Hyperopic thermokeratoplasty: clinical evaluation. J Cataract Refract Surg. 1991;17:830-838.
22. Goldberg MF. Clear lens extraction for axial myopia. An appraisal. Ophthalmology. 1987;94:571-582.
23. Siganos DS, Siganos CS, Pallikaris IG. Clear lens extraction and intraocular lens implantation in normally sighted hyperopic eyes. J Refract Corneal Surg. 1994;10:117-124.
24. Dausch D, Klein K, Schroder E. Excimer laser photorefractive keratectomy for hyperopia. Refract Corneal Surg. 1993;9:20-28.
25. Sher NA, Barak M, Daya S, Da Marchi J, Tucci A, Hardten DR, Frantz JM, Eifferman RA, Parker P, Telfair WB III, et al. Excimer laser photorefractive keratectomy in high myopia. A multicenter study. Arch Ophthalmol. 1992;110:935-943.
26. Lindstrom RL, Hardten DR, Chu YR, Muller A. Laser in situ keratomileusis (LASIK) for the treatment of low moderate and high myopia. Trans Am Ophthalmol Soc. 1997;95:286-296.
27. Krumeich JH, Daniel J, Gast R. Closed-system technique for implantation of iris -sup ported negati ve -power intraocular lens. J Refract Surg. 1996;12:334-340.
28. Krumeich JH, Knulle A, Daniel J. Improved technique of circular keratotomy for the correction of corneal astigmatism. J Refract Surg. 1997;13:255-262.
29. Budo C, Hessloehl JC, Izak M, Luyten GP, Menezo JL, Sener BA, Tassignon MJ, Termote H, Worst JG. Multicenter study of the Artisan phakic intraocular lens. J Cataract Refract Surg. 2000;26:1163-1171.
30. Tehrani M, Dick HB. Implantation of an Artisan toric phakic intraocular lens to correct high astigmatism after penetrating keratoplasty. KHn Monatsbl Augenheilkd. 2002;219:159-163.
31. Dick HB, Alió JL, Bianchetti M, Budo C, Christians BJ, El Danasoury MA, Guell JL, Krumeich J, Landesz M, Loureiro F, Luyten G, Marinho A, Rahhal M, Schwenn O, Spirig R, Thomann U, Venter J. Toric phakic intraocular lenses: European multicentric study. Ophthalmology. 2003;110:150-162.
Refractive Data with the Implantation of Artisan Toric PIOL
Visual Acuity Data With the Implantation of Artisan Toric PIOL*
Safety Data With the Implantation of Artisan Toric PIOL