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Haptic modification needed for glued IOL fixation in microcornea
Cataract surgery in eyes with abnormally small corneas is often considered complex.
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Microcornea, in which the horizontal corneal diameter is less than 11 mm, is known to be associated with congenital cataract or more prone to cataractous change in early adulthood. Microcornea may present alone or with other syndromes, often with microphthalmia and rarely with macrophthalmia.
The size or extent of surgical incision, the mode of lens removal, the nature of the IOL and the method of IOL power determination are modified in microcornea. The condition may also be associated with developmental deformity of ciliary zonules, which can lead to lens subluxation or intraoperative zonular dialysis during cataract extraction. Under such circumstances, IOL placement in the normal capsular bag may not be possible. Transscleral IOL fixation is one option in such a clinical scenario, and here we have presented our experience of glued transscleral posterior chamber IOL fixation in microcornea.
Surgical technique
Under sterile conditions and peribulbar anesthesia, two limbal-based partial-thickness scleral flaps with a size of 2.5 mm × 2.5 mm are made 180° diagonally apart. Infusion is maintained through a 23-gauge trocar infusion system, a superior limbal scleral tunnel incision is made with a keratome, and two 20-gauge sclerotomies are made under the existing flaps 1 mm to 1.5 mm from the limbus (Figures 1a and 1b).
When the cataractous lens is membranous or the cataract is grade 1 or 2, lensectomy with the Accurus surgical system (Alcon) via the limbal incision is performed. However when the cataract is grade 3 or 4, intracapsular cataract extraction (ICCE) is performed. In ICCE, an approximately 5-mm corneoscleral incision is made with a keratome, and the lens is extracted by a vectis; 10-0 monofilament sutures are placed in the main wound immediately after lens removal. Closed chamber anterior vitrectomy with the Accurus is performed to remove any vitreous that entered the anterior chamber along with the lens (Figure 1c). A three-piece foldable IOL with PMMA haptics of optic diameter 6 mm is introduced through the scleral tunnel wound through an injector (Figures 1d to 1f). Glued IOL forceps are passed through the sclerotomy, and the tip of the leading haptic is grasped and externalized. The haptic is held by an assistant or silicone tires. The second haptic is then flexed into the anterior chamber and pulled through the opposite sclerotomy by the glued IOL forceps using the handshake technique.
Figure 1. Corneal diameter measured with vernier calipers in an eye with microcornea with aphakia (a). Partial-thickness scleral flaps are made, and 23-gauge trocar infusion placed (b). Vitrectomy is performed in the pupillary region and behind (c). Three-piece foldable posterior chamber IOL is injected, and the haptic is externalized through the sclerotomy (d). Intralamellar scleral tunnel made with 26-gauge needle at the externalization point (e). Haptics inserted, and anterior chamber formed with air (f).
Images: Agarwal A
Figure 2. Intraoperatively, the haptic is trimmed with Vannas scissors (a) and inserted into the scleral tunnel (b).
When both haptics are externalized under the flaps, they have to be trimmed (Figures 2a and 2b) by Vannas scissors. The amount of haptic to be trimmed depends on the corneal diameter. Accurately trimmed haptics, without sharp edges, are tucked into the limbus-parallel intralamellar Scharioth scleral tunnels made with a 26-gauge needle at the point of haptic externalization. The main wound is closed with 10-0 monofilament nylon, and the trocar infusion is removed. Air is injected into the anterior chamber, and then reconstituted fibrin glue is injected under the scleral flaps and local pressure applied for 10 seconds (Figure 1f). Finally, the conjunctiva is closed with fibrin glue.
Visual outcomes and intraoperative modifications
In our cases, there was significant improvement in both corrected distance visual acuity (P = .032) and uncorrected distance visual acuity (P =.012) after surgery. There was no loss of corrected distance visual acuity in any of the eyes. Any non-improvement of corrected distance visual acuity was due to pre-existing conditions such as nystagmus, choroidal coloboma and amblyopia. There has been no significant difference between the potential visual acuity and the postoperative corrected distance visual acuity. There has been no severe postoperative complication in the follow-up.
Intraoperative haptic trimming has been performed in all the eyes. The mean haptic trimmed was 1.54 ± 0.33 mm. There was significant correlation between the corneal diameter and the amount of haptic trimmed (P = .000): The smaller the cornea, the larger the length of haptic to trim.
There was no intraoperative haptic damage noted. The mean main incision size ranged from 3.2 mm to 6 mm (mean: 3.7 ± 0.98 mm). All eyes had the main wound sutured with 10-0 monofilament nylon. There was no postoperative IOL decentration or tilt seen clinically or with anterior segment optical coherence tomography.
Haptic modification and closed globe manipulation
The surgical management of eyes with abnormally small corneal diameters and cataract is often considered complex. The usual intraoperative problem in cataract removal in eyes with microcornea, especially with a hard nucleus, is the requirement of a large incision extending sometimes about 180° — up to half of the cornea. Such a large wound can cause sudden globe decompression, which rarely induces intraoperative suprachoroidal hemorrhage or decompression retinopathy. However, when the cataract is membranous or less dense, lensectomy is beneficial. Open globe manipulation is always a high risk in these eyes. However, this can be dealt with by making a scleral tunnel incision rather than a straight incision and having preplaced sutures that would help to close the globe rapidly in case of suprachoroidal hemorrhage.
By following certain intraoperative modifications, glued posterior chamber IOLs can be placed in these eyes with less difficulty. Customized haptic trimming, implanting an IOL with a small optic diameter, the use of foldable IOLs and maintaining intraoperative closed globe manipulation will make the procedure less challenging. Because a 6-mm optic covers almost the entire pupillary zone, the chances of decentration are less. With the introduction of the foldable glued IOL and scleral tunnel incision, suture-induced astigmatism is often minimized.
Another intraoperative problem in these eyes is the nondilating pupil with iris coloboma. Iris retraction with iris hooks may help in phacoemulsification and visualization. A large iris coloboma can be corrected with iridoplasty with a modified McCannel suture. Patients with microcornea are often hypermetropic and have a shallow anterior chamber. The use of gas-forced infusion during phacoemulsification deepens the chamber and prevents endothelial damage.