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The dos and don’ts of glued IOLs
This method of secondary IOL fixation has its own set of nuances.
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Secondary IOL implantation is often carried out during IOL exchange surgery or for the correction of aphakia. A recent study reported that although the absolute number of secondary IOL procedures increased from 2000 to 2013, the 5-year risk for surgery decreased.
A secondary IOL in the absence of any capsular support may be a scleral-fixated posterior chamber IOL, an iris-fixated anterior chamber IOL or an angle-supported anterior chamber IOL; in the presence of capsular support, a sulcus-placed posterior chamber IOL; or in the presence of an intact capsular bag, in-the-bag placement. It is important to note that clinical studies have shown no long-term differences in visual outcomes and complications after primary anterior chamber IOL or secondary scleral-fixated IOL implantation. While anterior chamber IOL is a faster surgical technique, it requires a peripheral iridectomy. An anterior vitrectomy is performed when vitreous is present in the anterior chamber, in the pupillary region or just behind the iris. Avoid an anterior chamber IOL in the presence of angle abnormalities, glaucoma or corneal endothelial damage. The choice between a secondary posterior chamber IOL vs. anterior chamber IOL is based on surgeon preference, surgeon comfort level and anterior segment tissue anatomy.
Preoperatively, corneal endothelial cell count and pachymetry are performed when applicable. Additionally, vitreous in the anterior chamber or in the pupillary area should be noted. Further, iris, anterior chamber angle and capsular evaluations are essential in the surgical planning of a secondary IOL procedure. Lastly, the posterior segment should be assessed, namely the macula, optic nerve and peripheral retina.
During surgery, the corneal endothelium should be protected using ophthalmic viscosurgical devices. Postoperatively, in addition to anterior segment evaluation, the posterior segment including the peripheral retina should be evaluated.
In this column, Drs. Narang and Agarwal describe useful dos and don’ts when it comes to one of the secondary IOL techniques, namely glued IOL technique to correct aphakia.
Thomas “TJ” John, MDOSN Surgical Maneuvers Editor
Glued intrascleral fixation of an IOL is a proven method of secondary IOL fixation that provides optimal results in the postoperative period. The measurement of the white-to-white diameter is essential to help gauge the amount of haptic that will be available for a scleral tuck. Tucking is the most essential aspect of intrascleral fixation because this imparts stability to the IOL fixation.
Like any other surgery, glued IOL has its own set of nuances to follow with specific dos and don’ts. The essentials to be followed are listed in this article.
180° scleral flap marking
This is an important surgical step that ensures a properly centered IOL in both the intraoperative and postoperative periods (Figure 1).
Do: A simple toric axis marker or a specifically designed glued IOL marker can be used for scleral flap marking. A standard scleral flap size of 2.5 mm by 2.5 mm should be made.
Don’t: A larger scleral flap requires a greater amount of haptic length to traverse beneath the scleral flap from its exit at the sclerotomy site to its tucking. This allows a lesser amount of haptic to be available for scleral tuck. On the contrary, a smaller flap will make the tucking difficult because, upon its exit from the sclerotomy site, it will be difficult to tuck the haptic directly into the pocket. Therefore, an optimum flap size is needed for a smooth surgery.
Source: Priya Narang, MS, and Amar Agarwal, MS, FRCS, FRCOphth
Sclerotomy at 180°
Even though the scleral flaps are made 180° opposite, it is mandatory to make the sclerotomy sites also 180° opposite each other beneath the scleral flaps. The sclerotomy sites denote the exit point of the haptics from the eye after externalization. If the sclerotomy is made beneath the scleral flap but is not 180° opposite, then it can lead to decentration of the IOL.
IOL unfolding
The unfolding maneuver of a three-piece IOL should be slow and gradual. After the IOL has been loaded into the cartridge, the tip of the haptic should be slightly extruded from the cartridge before it is injected inside the eye. Once the cartridge is introduced inside the anterior chamber, glued IOL forceps are introduced from the left sclerotomy site and the tip of the leading haptic is grasped (Figure 2). The IOL is then slowly injected inside the eye, facilitating gradual unfolding.
Do: Start injecting the IOL inside the anterior chamber once the tip of the haptic is grasped to prevent an accidental IOL drop during the surgery.
Don’t: Do not pull the tip of the leading haptic before the entire IOL has unfolded because this can damage the haptic.
Haptic maneuverability
Haptic maneuverability is the most salient aspect of glued IOL surgery. The haptic should always be externalized after holding the tip. The haptic should be maneuvered throughout its length with the help of the handshake technique until the tip of the haptic is reached and held (Figure 3).
Don’t: Do not hold the haptic through its mid-shaft and pull it while externalized. This can lead to haptic kink and breakage, after which it becomes mandatory to explant the IOL and then implant a new IOL.
Vitrectomy
Adequate vitrectomy should be performed in the anterior chamber as well as in the pupillary zone to prevent pulling the vitreous strands during the IOL maneuver. After haptic tuck, vitrectomy should also be performed at the sclerotomy site to prevent any vitreous strand incarceration or prolapse into the sclerotomy site.
Haptic tuck
A mid-scleral pocket should be created with a 26-gauge needle, and the haptic should be tucked into it (Figure 4).
Don’t: Avoid making superficial thin pockets that can lead to haptic exposure.
Large eyes
Eyes with greater white-to-white diameter need to be specially dealt with while performing glued IOL, and various criteria and considerations should be taken into account due to the limitation imposed by the maximum length of the IOL that is commercially available. To overcome this limitation, various methods are adopted, and they are mentioned here in brief.
Vertical glued IOL
The vertical diameter of the cornea is less than the horizontal diameter. Therefore, in cases with greater white-to-white diameter, often a vertical glued IOL is advocated (Figure 5) in which scleral flaps are made at the 6 and 12 o’clock positions. After making the vertical flaps, the surgeon sits temporally and completes the case.
Anterior sclerotomy
Sclerotomy is usually performed at a distance of 1 mm to 1.5 mm away from the limbus. Anterior sclerotomy is performed at a distance of 0.5 mm from the limbus with the concept of shifting the plane of the IOL anteriorly, thereby allowing a greater amount of haptic length to be externalized because the haptics traverse a shorter distance when the plane of IOL is shifted anteriorly.
Do: The 22-gauge needle should be pierced at a distance of 0.5 mm beneath the flap with the direction being kept vertical toward the mid-vitreous cavity.
Don’t: Do not push the needle too hard if resistance is encountered. Withdraw the needle and re-enter a little behind the attempted site. Forceful entry can lead to iridodialysis.
Vitrector-assisted peripheral iridectomy
To overcome the issue of creating an iatrogenic iridodialysis, the technique of vitrector-assisted peripheral iridectomy is adopted. At the proposed site of performing an anterior sclerotomy, peripheral iridectomy is performed with the vitrector set at the rate of 20 cuts per minute (Figures 6 and 7). Low cut rate with moderate vacuum ensures that an adequate amount of iris tissue is caught up in the vitrector probe and then cut.
Single-pass four-throw pupilloplasty
Performing an anterior sclerotomy often causes optic capture into the pupillary margin due to an anterior shift of the IOL plane. Hence, single-pass four-throw pupilloplasty is often indicated so as to narrow down the size of the pupil to less than the diameter of the optic so as to avert an optic capture.
Quintet in glued IOL
As the word “quintet” suggests the number five, the terminology of quintet in glued IOL suggests a combination of five techniques adopted for eyes with greater white-to-white diameter. The vertical glued IOL with fixation of a trocar anterior chamber maintainer, anterior sclerotomy, vitrector-assisted peripheral iridectomy and pupilloplasty is labeled as quintet in glued IOL.
Small eyes
In eyes with a smaller white-to-white diameter, no specific problem is encountered except a greater amount of haptic is externalized (Figure 8). These haptics can be trimmed to the required amount and then tucked into the scleral pockets.
- References:
- Agarwal A, et al. J Cataract Refract Surg. 2008;doi:10.1016/j.jcrs.2008.04.040.
- Agarwal A, et al. J Cataract Refract Surg. 2013;doi:10.1016/j.jcrs.2013.01.019.
- Chan TC, et al. Am J Ophthalmol. 2015;doi:10.1016/j.ajo.2014.10.016.
- Ladi JS, et al. Indian J Ophthalmol. 2013;doi:10.4103/0301-4738.109383.
- Por YM, et al. Surv Ophthalmol. 2005;doi:10.1016/j.survophthal.2005.06.010.
- Szigiato AA, et al. J Cataract Refract Surg. 2017;doi:10.1016/j.jcrs.2017.03.040.
- For more information:
- Amar Agarwal, MS, FRCS, FRCOphth, can be reached at Dr. Agarwal’s Eye Hospital, 19 Cathedral Road, Chennai 600086, India; email: dragarwal@vsnl.com.
- Priya Narang, MS, can be reached at Narang Eye Care & Laser Centre, Ahmedabad, India; email: narangpriya19@gmail.com.
- Edited by Thomas “TJ” John, MD, a clinical associate professor at Loyola University at Chicago and in private practice in Oak Brook, Tinley Park and Oak Lawn, Ill. He can be reached at email: tjcornea@gmail.com.
Disclosures: Agarwal, Narang and John report no relevant financial disclosures.