Introduction
The earliest attempts to expand the sclera in humans were performed in the mid-1980s and consisted of simple radial incisions in the sclera, similar to radial keratotomy (RK) of the cornea. This technique, however, was primarily applicable to young presbyopes, as the average increase in the amplitude of accommodation was only about 1.50 diopters (D). Additionally, as the incisions healed, the effect regressed.
The first scleral expansion procedures using an encircling band ( Fig. 36.1 ) were performed in 1992. This procedure was a development of an initial concept that consisted of a rigid plastic polymethylmethacrylate (PMMA) ring used to increase the scleral circumference. Although the results were dramatic, the procedure was plagued with complications, such as anterior segment ischemia, conjunctival erosions, and variable results. Various modifications were attempted to circumvent these problems. One such method involved passing portions of the bands through the sclera, forming scleral belt loops. This method did not include the use of scleral sutures in an effort to simplify the surgical technique, reduce the complications, and decrease the variability of the results.
In 1997, six consecutive nonmyopic patients who underwent scleral expansion using a complete encircling band were reported. The band was passed through four separate scleral belt loops located at the 12, 3, 6, and 9 o’clock cardinal positions ( Fig. 36.2A ), which were then ultrasonically fused together at the 1:30, 4:30, 7:30, and 10:30 positions ( Fig. 36.2B ).
Five of the six patients required removal of the scleral expansion bands (SEBs) 3 to 6 months owing due to conjunctival erosion from the roughened areas where the PMMA bands were ultrasonically welded together. After scleral expansion band removal, the accommodative amplitude of these patients returned to preoperative values.
An additional three consecutive patients subsequently underwent the same procedure. In an effort to provide a better cosmetic result with more accommodation, the scleral belt loops were made much deeper. These three patients subsequently developed anterior ischemic syndrome (AIS), and the bands were removed 24 to 96 hours after surgery. Given previous reports of treatment of AIS with hyperbaric oxygen, these patients were treated with hyperbaric oxygen. All responded well, with no loss of vision. This was the first known occurrence of AIS as a result of scleral expansion. Despite the posterior insertions of the rectus muscles, these deeper tunnels likely resulted in a significant reduction of blood flow through the anterior ciliary arteries that perforate the sclera at the insertions of the rectus muscles. To avoid compression of the anterior ciliary arteries and AIS, surgeons began placing the scleral belt loops along the 45-degree meridians at 1:30, 4:30, 7:30, and 10:30.
Scleral Expansion Segments—Manual Approach
Further modifications to the scleral expansion band followed. In 1998, a new prototype was developed consisting of four individual PMMA segments that were not connected to each other. The result was decreased rates of conjunctival erosion, a simplified procedure, and a significant decrease in instrumentation cost. To decrease the risk of AIS, these segments were also placed in scleral belt loops along the 45-degree meridians, away from the ciliary artery insertions ( Fig. 36.3 ).
Scleral Expansion Segments—Automated Approach: VisAbility Micro-Insert
The Refocus Group has developed an automated approach to insert four scleral implants in the oblique quadrants at a defined and reproducible location from the limbus. They developed a sclerotome docking station to enable performing the sclerotomy with consistency. The procedure involves placing four PMAA injection molded implants about 2000 to 4000 µm from the limbus, to the depth of 400 µm within the sclera. The aim is to lift the sclera and the ciliary muscle to tighten the zonular fibers holding the lens. The procedure takes about 1 hour to perform bilaterally. The micro-insert has received the Conformité Européene (CE) mark approval and is currently undergoing FDA clinical trials.
In a 24-month clinical trial with VisAbility Micro-Insert trials presented in 2013, 80 patients were asked to describe their unaided vision as “excellent,” “acceptable,” or “poor,” pre- and postoperatively. At 24 months, 73% patients reported at least “acceptable” vision overall, and 99% reported “acceptable” for distance tasks. About 83% patients were able to perform near tasks such as reading medicine labels, prices, and newspapers. The percentage of patients reporting “acceptable” vision when reading newspapers was reported to improve from 4% preoperatively to 76% at 24 months postoperatively. About 93% eyes were reported to have distance-corrected near visual acuity (DCNVA) of 0.3 logMAR (20/40 Snellen) or better in a 2014 report from the same trial.
Although the results seem promising, one major risk involved for patients undergoing VisAbility micro-insert implant is anterior segment ischemia (ASI) due to the mechanical vascular compression from the implant. The other major risks include implant infection, endophthalmitis, moderate to severe subconjunctival hemorrhage, and implant displacement. About 75% patients with the first generation of VisAbility micro-insert implants were reported to have had at least one implant movement or displacement by the FDA.
Complications of Manual Surgery
Only one case of AIS has been reported using the latest 5.5-mm scleral expansion segments. This complication may have resulted from improper positioning of the segments. The indications of AIS are as follows:
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dilated nonreactive pupil or nonreactive papillary sector
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Desçemet fold, grayish look
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trace of flare and cells
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intraocular pressure (IOP) less than 10 mm Hg
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nausea
To date, no cases of malignant glaucoma have been reported using the new scleral expansion segments. Theoretically, however, this is a possibility as the segments may increase posterior pressure, blocking outflow and resulting in aqueous misdirection. Intravenous mannitol is given to dehydrate the vitreous, decreasing the likelihood of this complication. Other minor complications include the following:
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conjunctival hyperemia
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subconjunctival hemorrhage
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transient ptosis
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scleral expansion segment rotation or subluxation
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photophobia due to tear film instability
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conjunctival erosion
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accommodative fatigue
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temporary keratoconjunctivitis
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swollen or irregular conjunctiva
Clinical Outcomes of Manual Surgery
Increases in accommodation after this technique have ranged from 1.00 D to 10.00 D. Schachar himself has reported 5.80 D to 11.0 D of subjectively measured accommodative amplitude in postoperative patients. Two studies of 29 and 7 patients have reported an increased range of accommodation in all patients with an average of 3.02 D and 3.13 D, respectively. Similar to our findings, an increased range of near vision was noted in the unoperated eye. This increase approached 20% to 50% of the increase in the operated eye.
In an independent study, subjectively measured amplitude increased in three of eight patients 6 months postoperatively but returned to preoperative levels in all eyes within 1 year. Another study of 29 patients reported a mean increase in amplitude by 1.70 D ± 1.50 D in the operated eyes and 1.3 D ± 1.20 D in the unoperated eyes.
A phase I, multicenter, prospective, nonrandomized study by the US Food and Drug Administration (FDA) showed promising results. Approximately 59% of patients gained three lines or more of near vision. The response was variable, perhaps because of the surgeon’s learning curve and the band placement variability. However the company filed for bankruptcy.
Clinical Outcomes of Automated Approach
The ClinicalTrials.gov filing for the VisAbility micro-insert system indicates that the Refocus Group is evaluating the safety and effectiveness of the VisAbility MicroInsert System for the improvement of near visual acuity in presbyopic patients. The objective of this study is to evaluate the safety and effectiveness of the VisAbility Implant System (VIS) for the improvement of near visual acuity in presbyopic patients. This is a prospective clinical study that will enroll and determine eligible a total of 360 subjects ranging in age between 45 and 60 years of age at up to 14 clinical sites. The follow-up period was 1 year. The ClinicalTrials.gov filing indicated that the study will also include a 60-subject randomized controlled sub-study at three investigational sites. Subjects enrolled and eligible at these sites will be randomized (1 : 1 ratio) to a surgery group or a control group. Subjects randomized to the surgery group will undergo surgery and will be followed for 24 months in the same manner as the larger non-randomized surgical group. Subjects randomized to the control group will be followed for 6 months, and will be eligible to undergo surgery after completion of this 6-month follow-up period. Encouraging results have been reported at the 2017 and 2018 OIS meetings. Table 36.1 includes some of the preliminary data presented at these meetings of a relatively small subgroup of 20 to 40 patients.
| Baseline | 3 Months | 1 Year | 2 Years | ||
|---|---|---|---|---|---|
| Distance corrected near visual acuity at 40 cm ( n = 20) | 20/40 (J3) or better (%) | 0 | 100 | 100 | 100 |
| 20/32 (J2) or better (%) | 0 | 90 | 95 | 90 | |
| 20/25 (J1) or better (%) | 0 | 50 | 63 | 75 | |
| Uncorrected near visual acuity at 40 cm ( n = 20) | 20/40 (J3) or better (%) | 10 | 100 | 100 | 100 |
| 20/32 (J2) or better (%) | 3 | 91 | 95 | 100 | |
| 20/25 (J1) or better (%) | 0 | 84 | 90 | 90 | |
| Mean change in MRSE from baseline ( n = 40 at baseline, n = 39 at 3 months, n = 39 at 1 year, and n = 40 at 2 years) | Mean change | −0.05 | 0.11 | 0 | −0.03 |
| (−SD) | −0.37 | −0.27 | −0.25 | −0.26 | |
| (+SD) | 0.26 | 0.11 | 0.25 | 0.25 | |
| Close-up visual performance without glasses ( n = 26 at 3 months, n = 24 at 1 year, and n = 25 at 2 years) | Significantly better or better | 100 | 88 | 96 | |
| No change | 0 | 13 | 0 | ||
| Worse or significantly worse | 0 | 0 | 0 | ||
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