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Clear lens extraction with intraocular lens implantation for hyperopia

Preetha, Rajasekaran MBBSa; Goel, Parul MSa; Patel, Nishant DOa; Agarwal, Sunita MS, FSVH, FRSH, DOa; Agarwal, Athiya MD, FRSH (Lon), DOa; Agarwal, Jaiveer FICS, DOMS, FORCEa; Agarwal, Tahira FICS, DOMS, FORCEa; Agarwal, Amar MS (Oph), FRCS, FRCOphth (Lon)*,a

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Journal of Cataract & Refractive Surgery: May 2003 - Volume 29 - Issue 5 - p 895-899
doi: 10.1016/S0886-3350(02)01979-X
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Abstract

Hyperopia is a refractive error in which parallel rays of light are brought to focus at a distance behind the sentient layer of the retina when the eye is at rest. The image formed comprises circles of diffusion of considerable size that are thus blurred.1 The hyperopic eye is small with a shallow anterior chamber and predisposition to angle-closure glaucoma. Depending on their age and the magnitude of the refractive error, patients with hyperopia cannot see clearly at distance or near. This problem becomes worse as they approach the presbyopic age.

Various surgical procedures have been developed to correct hyperopia. These include keratophakia, hexagonal keratotomy, automated lamellar keratoplasty, thermal keratoplasty, photorefractive keratectomy (PRK), and laser in situ keratomileusis (LASIK).2 Significant regression, poor predictability, and instability are some disadvantages of hyperopic refractive surgery. Hexagonal keratotomy leads to poor wound healing, corneal edema, and irregular astigmatism.3 Thermal keratoplasty causes regression to the pretreatment steepness of the central cornea.2,4 Fyodorov's radial thermokeratoplasty damages the corneal endothelium. Holmium:YAG laser thermal keratoplasty causes regression.5,6

Of the lamellar procedures,2 keratophakia induces keratometric astigmatism,7 epikeratophakia leads to regression and problems with the cryolathe,8,9 and PRK is limited to +3.00 to +4.00 diopters (D) as the ablated ring tends to fill with epithelium, increasing regression and haze and decreasing best corrected visual acuity (BCVA) in eyes with high hyperopia.10,11 Automated lamellar keratoplasty is unpredictable and can cause ectasia.12 Laser in situ keratomileusis for hyperopia provides better predictability, less regression, and less corneal haze than PRK.13

The results of another approach, posterior chamber phakic intraocular lens (IOL) implantation, show short-term safety, efficacy, and stability.14 Iris-claw IOLs have been used in phakic eyes; however, observation by specular microscopy is mandatory.15

Clear lens extraction (CLE) with posterior chamber IOL implantation for hyperopia has been proposed as an alternative treatment. We evaluated the efficacy, safety, and predictability of this procedure.

Patients and Methods

This prospective study comprised 20 eyes of 12 patients. The mean age of the 7 men and 5 women was 35.75 years (range 19 to 50 years). All patients provided written informed consent.

Preoperatively, patients had a slitlamp evaluation, cycloplegic refraction, fundus examination, applanation tonometry, gonioscopy, and keratometry. A few patients had early lenticular nuclear sclerotic changes according to their age that had not developed to cataract. Ultrasound A-scan was performed using the applanation technique, and the axial length was measured. The mean axial length was 20.98 mm (range 18.4 to 22.2 mm). The IOL power, calculated using the Holladay 2 formula,16 ranged from +27.0 to +37.0 D. The observed outcome of refraction was used to adjust the IOL power in the other eye.

The eye was prepared for surgery with cyclopentolate hydrochloride 1% and phenylephrine 5% eyedrops, 1 drop every 10 minutes 1 hour before surgery. Routine cleaning and draping of the eyes were done.

The anterior chamber was entered through the side port through clear cornea with a 26-gauge needle, and hydroxypropyl methylcellulose 2% was injected. A 3.2 mm wide temporal clear corneal incision was made with a sapphire knife. A continuous curvilinear capsulorhexis was made with a bent 26-gauge needle mounted on a viscoelastic syringe. Hydrodissection was done. The side port was enlarged for the chopper. An Alcon Universal II unit was used for phacoemulsification. The nucleus was emulsified/aspirated and the remaining cortex aspirated. Viscoelastic material was then injected into the eye. In 12 eyes, a Staar silicone plate-haptic foldable IOL was implanted in the bag. In 8 eyes requiring an IOL power greater than +30.0 D, a Rayner poly(methyl methacrylate) (PMMA) IOL was implanted. The viscoelastic material was removed, and stromal hydration was done. No intraoperative complications occurred.

A peripheral iridectomy was done in 5 eyes as the angles were occludable. In 8 eyes, a single 10-0 nylon suture was used to close the tunnel as the section had been extended to insert the 5.25 mm PMMA IOL. The suture was removed within 1 month postoperatively.

All eyes were examined on the first postoperative day. Treatment comprised topical steroid and antibiotics for 1 month. Follow-up was at 1 week and 1 month and every 6 months thereafter. The mean follow-up was 16.96 months (range 6 to 35 months). At each visit, the uncorrected visual acuity (UCVA) and BCVA were measured and a slitlamp examination and applanation tonometry were performed.

Results

The mean preoperative spherical equivalent (SE) was +6.66 D ± 2.17 (SD) (range +4.75 to +13.00 D). The range was from +4.12 to +8.00 D in 16 eyes (20%), +8.12 to +12.00 D in 3 eyes (15%), and greater than +12.12 D in 1 eye (10%). The mean postoperative SE was +0.68 ± 0.67 (range 0 to +2.50 D). Three eyes (15%) had a postoperative SE of 0 D and 17 eyes (85%), from +0.12 to +2.50 D. The predictability of the procedure (attempted versus achieved correction) was statistically significant (P<.05; Student t test).

The mean preoperative UCVA (decimal equivalent) was 0.10 ± 0.09 (range 0.03 to 0.25) (Figure 1). It was worse than 0.10 in 14 eyes (70%) and from 0.10 to worse than 0.25 in 6 eyes (30%). The mean postoperative UCVA was 0.45 ± 0.25 (range 0.10 to 1.00). It was worse than 0.10 in 2 eyes (10%), from 0.10 to 0.25 in 3 eyes (15%), from 0.25 to 0.50 in 10 eyes (50%), and better than 0.50 in 5 eyes (25%).

Figure 1.
Figure 1.:
(Preetha) Cumulative Snellen UCVA.

The mean preoperative BCVA (decimal equivalent) was 0.53 ± 0.29 (range 0.10 to 1.00). It was worse than 0.10 in 2 eyes (10%), from 0.10 to 0.25 in 1 eye (5%), from better than 0.25 to 0.50 in 7 eyes (35%), and better than 0.50 in 10 eyes (50%). The mean postoperative BCVA was 0.63 ± 0.30 (range 0.10 to 1.00). It was worse than 0.10 in 2 eyes (10%), from 0.10 to 0.25 in 2 eyes (10%), from better than 0.25 to 0.50 in 4 eyes (20%), and better than 0.50 in 12 eyes (60%). Two eyes (10%) with a postoperative BCVA of 0.10 were amblyopic. Fourteen eyes (70%) were within ±0.50 D of the intended refraction and 18 eyes (90%), within ±1.00 D. Two eyes (10%) lost 1 line of BCVA, 2 eyes (10%) gained 1 line, and 4 eyes (20%) gained 2 or more lines (Figure 2).

Figure 2.
Figure 2.:
(Preetha) Change in Snellen lines of BCVA.

The efficacy index (mean postoperative UCVA/mean preoperative BCVA) was 0.84. The safety index (mean postoperative BCVA/mean preoperative BCVA) was 1.1.

One eye developed fibrin in the early postoperative period that responded to steroid drops instilled over 2 hours while awake. Six patients developed significant posterior capsule opacification (PCO) over a mean follow-up of 17.16 months (range 7 to 19 months) and required a neodymium:YAG (Nd:YAG) posterior capsulotomy. No patient who had an Nd:YAG posterior capsulotomy developed complications such as cystoid macular edema (CME) or retinal detachment during a mean follow-up of 11.83 months (range 6 to 18 months).

Discussion

The refractive surgical correction of hyperopia has lagged far behind the advances in the treatment of myopia and astigmatism. Clear lens extraction for the correction of high myopia is a concept known since at least 1800. After the invention of sterilization, CLE for myopia was done by Fukala and Vacher.17

Hyperopic eyes with a smaller axial length, small anterior chamber, and small corneal diameter are more vulnerable to intraoperative and postoperative complications. However, CLE with IOL implantation for hyperopia is considered to be a safe and effective modern small-incision cataract technique except in eyes with extreme hyperopia such as those with nanophthalmos. For patients with presbyopic hyperopia, CLE with IOL implantation has great appeal.18

There have been several reports of CLE for hyperopia in the past decade. In a study by Siganos and Pallikaris19 using the SRK II formula for IOL power calculation, 100% of eyes were within ±1.00 D of emmetropia. The authors report the treatment was safe and effective for hyperopia from +6.75 to +13.75 D and that the SRK II formula proved superior to the SRK/T formula for IOL power calculation. Lyle and Jin20 report that 89% of patients achieved a UCVA of 20/40 or better; all eyes had a BCVA of 20/25 or better. The IOL power was calculated using the Holladay formula as it reduces the chance of residual hyperopia postoperatively. The authors found the formula to be less accurate for hyperopia less than +3.00 D.20 Kolahdouz-Isfahani and coauthors21 report a close association between achieved SE and predicted SE using the Holladay Consultant formula for IOL power calculation. They suggest that clear lensectomy is superior in the correction of moderate to high hyperopia in patients 35 years or older. They also report postoperative malignant glaucoma in 1 nanophthalmic eye and recommend peripheral surgical iridectomies in all eyes with an axial length less than 20.0 mm.

In our study, 12 eyes (60%) achieved a BCVA better than 20/40. Clear lens extraction was also done in amblyopic eyes. Using the Holladay 2 IOL power formula, 3 eyes (15%) achieved the intended refraction (emmetropia) whereas 18 eyes (90%) were within ±1.00 D of the intended refraction. Two eyes of the same patient had a postoperative SE of +2.50 D (axial length 21.5 mm) and +2.00 D (axial length 21.0 mm). Postoperatively, the axial length and anterior chamber depth measurements were found to be accurate. Inaccurate IOL power calculations were not related to the results in eyes with shorter axial lengths because other eyes with shorter axial lengths achieved emmetropia with the same IOL power formula.

Hyperopic eyes with shallow anterior chambers are more prone to angle closure. All eyes in our series had gonioscopic evaluation preoperatively; peripheral iridectomies were done in 5 eyes (25%) with occludable angles. We recommend preoperative gonioscopy in all patients who have CLE for hyperopia.

No intraoperative complications such as capsule rupture occurred in our series. Postoperatively, PCO developed in 6 eyes (30%); the mean time to opacification was 17.16 months. All 6 eyes had a successful Nd:YAG capsulotomy with no complications such as CME or retinal detachment. In our series, there were no nanophthalmic eyes, which are more prone to intraoperative and postoperative complications such as uveal effusion, retinal detachment, intraocular hemorrhage, and malignant glaucoma. Foldable piggyback IOLs may be required in nanophthalmic eyes. In-the-bag implantation of piggyback IOLs has been associated with interlenticular pseudophakic opacification and a hyperopic shift.22 Thus, 1 IOL must be placed in the bag and the other in the sulcus. In our study, the IOL dioptric power ranged from +27.00 to +37.00 D. Eyes requiring more than +30.00 D received a PMMA IOL. We did not implant piggyback IOLs as higher power IOLs are now available. However, PMMA IOLs require a larger incision, negating the advantages of a watertight environment, which is particularly desirable in small eyes, especially nanophthalmic eyes.

In this study, CLE was done in patients in the presbyopic age group. However, phakic IOLs may be a better option in these patients as they do not lose their accommodative power.

Laser in situ keratomileusis has been suggested as an alternative to correct hyperopia. However, Ditzen and coauthors13 suggest that the preoperative corneal radius is an important factor. Sanders et al.14 report an increased incidence of undercorrection and epithelial ingrowth in eyes with hyperopia, especially in those with more than +6.00 D, because of problems with the suction ring and the microkeratome. Regression and undercorrection are major concerns in LASIK for hyperopia. Göker and coauthors23 report regression and undercorrection of more than 2.00 D in 12.9% of eyes that had LASIK for hyperopia. Tabbara and coauthors24 point to the lack of a specialized nomogram for hyperopia to achieve results comparable to those of LASIK for myopia. Postoperative glare is a common side effect of LASIK for hyperopia,25 as is dry eye, particularly in women, which has been associated with refractive regression.26 Thus, the choice of LASIK to correct hyperopia should be made with caution.

Clear lens extraction with IOL implantation appears to be a safe and effective procedure to correct hyperopia with minimal complications, especially in patients in the presbyopic age group. However, longer follow-up is required to ensure long-term safety. Also, caution should be taken during surgery in nanophthalmic eyes. Further refinement is needed in the calculation of IOL power in patients with hyperopia.

References

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