Predisposing factors, direction of dislocation, and changes in intraocular pressure after intrascleral intraocular lens fixation surgery

Introduction

Various surgical techniques have been devised to fix an intraocular lens (IOL) in the eye when IOL insertion is not possible due to crystalline lens dislocation/subluxation (ectopia lentis), IOL dislocation/subluxation, lens capsule breakage, or rupture of the ciliary zonule.¹ However, there have been several problems with previous techniques. For example, insertion of an IOL into the anterior chamber is associated with a high risk of corneal endothelial damage and bullous keratopathy.² Transscleral sutured posterior-chamber IOL is technically complicated and can lead to infection.^3,4,5 Flanged IOL fixation with the double-needle technique solves many of these problems and has been widely used in recent years as it is safe and simple.^1,6,7

Predisposing factors for IOL intrascleral fixation include acquired breakage of the ciliary zonule due to trauma, history of vitrectomy, problems during cataract surgery (such as posterior capsule rupture), and internal factors (pseudoexfoliation [PE] syndrome and genetic diseases), but few reports have reviewed these factors in detail.^8,9 In fact, some studies have examined predisposing factors for IOL dislocation, but to the best of our knowledge, so far, no studies have evaluated predisposing factors for dislocation, including ectopia lentis.^10,11

It has been reported that intraocular pressure (IOP) in patients with PE can be lowered by treatment of IOL dislocation.¹² However, no reports have evaluated IOP trends according to other predisposing factors or the direction of dislocation.

Thus, this study aimed to identify the predisposing factors and direction of dislocation of the natural crystalline lens or IOL in IOL intrascleral fixation surgery and the change in IOP after surgery.

Materials And Methods

Medical records of 240 eyes (232 patients) that underwent IOL implantation using sutureless intrascleral fixation and concurrent pars plana vitrectomy between February 2015 and September 2020 at Chiba University Hospital were retrospectively reviewed. Four cases were excluded from this study because of the following reasons: one case in which an IOL was inserted secondarily after cataract surgery in childhood, one case in which an IOL was removed and a secondary IOL was inserted for endophthalmitis, and two cases in which a secondary IOL was intentionally inserted in an aphakic eye during surgery for severe retinopathy.

All data (age, sex, predisposing factors, eye drop scores, IOPs, and direction of lens or IOL deviation) were collected from medical records.

The predisposing factors were determined based on a review of medical records as follows: (1) PE; (2) trouble in surgery (intraoperative problems during cataract surgery, such as rupture of the ciliary zonule or posterior capsule cases); (3) history of trauma; (4) genetic diseases (such as Marfan syndrome); (5) history of vitrectomy; (6) retinitis pigmentosa (RP); (7) history of atopic dermatitis; and (8) long eye axis (> 26 mm).

Eye drop scores were examined with regard to glaucoma medication use before and after surgery. The eye drop score was 1 point per glaucoma eye drop (2 points for combination drugs). Acetazolamide oral medication was scored as 1 point.

IOP was measured with noncontact tonometer (NCT) using TONOREF II auto-refractometer (Nidek, Aichi, Japan) or a Goldmann applanation tonometer (GAT) preoperatively and at 1 day, 1 week, and 1 month after surgery. Fifty-two cases with lack of some IOP data were excluded from further IOP analysis.

Statistical analyses were performed with Mann-Whitney U test and mixed-effect model using R version 4.1.2 (https://www.r-project.org/). A mixed-effect model analysis (subject as random effect) was conducted using the lme4 package (Bates et al., 2022) and lmerTest (Kuznetsova et al., 2020) to compare the preoperative and postoperative IOPs. Statistical significance was set at p < 0.05.

The study protocol was approved by the Institutional Review Board of Chiba University Graduate School of Medicine (No. 3917), and the procedures complied with the tenets of the Declaration of Helsinki. Patients were informed about the purpose of the study via the internet and were allowed to opt out of the study. Data collection was conducted based on the Ethical Guidelines for Medical and Health Research Involving Human Subjects in Japan (https://www.mhlw.go.jp/file/06-Seisakujouhou-10600000-Daijinkanboukouseikagakuka/0000080278.pdf).

Results

The data of total 236 eyes (160 male and 76 female patients) with a median age of 68 years are summarized in Table 1.

The predisposing factors of the 236 cases were as follows: 48 (20.3%) long eye axis, 44 (18.6%) PE, 42 (17.8%) trouble in surgery, 40 (16.9%) history of trauma, 34 (14.4%) history of vitrectomy, 21 (8.9%) history of atopic dermatitis, 6 (2.5%) genetic disease, 4 (1.7%) RP, 58 (24.6%) unknown cause; and 56 (23.7%) cases had overlapping predisposing factors (Table 1). The most common overlap was PE and trouble in surgery in 18 cases, followed by long eye axis and history of vitrectomy in 15 cases. All cases with overlapping predisposing factors are listed in Supplementary Table S1 online.

The directions of lens and IOL deviation of the 236 cases were as follows: 31 (13.1%) were aphakic eyes; 12 (5.1%) with the natural crystalline lens fall into the vitreous cavity, 4 (1.7%) with the natural crystalline lens deviation upward, 1 (0.4%) nasally, 8 (3.4%) downward, 2 (0.8%) temporal, and 16 (6.8%) anteriorly; 46 (19.5%) with the IOL fall into the vitreous cavity, and 6 (2.5%) with the IOL deviation upward, 1 (0.4%) nasally, 52 (22.0%) downward, 4 (1.7%) temporal, 6 (2.5%) anteriorly, and 1 (0.4%) posteriorly; 46 (19.5%) cases showed no evidence of deviation (Table 1). Fifteen of these patients were converted to IOL intrascleral fixation during cataract surgery at our institution. In addition, 25 and 5 of the 46 cases had donesis of the natural crystalline lens and IOL, respectively.

In the PE and trouble in surgery groups, the cases with aphakic eyes (PE: 16 of 44, trouble in surgery: 23 of 42) and no deviation (PE: 12 of 44, trouble in surgery: 15 of 42) were observed mainly, whereas the cases with the IOL fall into the vitreous cavity (vitrectomy: 20 of 34, long eye axis: 19 of 48) and the IOL deviation downward (vitrectomy: 10 of 34, long eye axis: 13 of 48) were observed in the history of vitrectomy and long eye axis groups (Table 2). The cases with the deviation in various directions were observed in the history of trauma group, and 5 of the 16 cases with the natural crystalline lens deviation anteriorly had a history of trauma.

The time course changes in IOP in 184 individual cases are shown in Figure 1. The mean IOP at all timepoint (preoperative and 1 day, 1 week and 1 month postoperative) in the 184 cases were 18.7±8.7 mmHg, 17.9±7.7 mmHg, 15.6±7.0 mmHg and 14.5±4.5 mmHg, respectively (Table 1 and Figure 1, red line); 1 week and 1 month postoperative IOPs showed a significant decrease from preoperative IOP (p<0.001, mixed-effect model).

The mixed-effect model analysis for each group of the predisposing factors showed that the decreases of 1 week and 1 month postoperative IOPs from preoperative are significant in history of trauma and long eye axis groups, and the decrease of 1 month postoperative IOP is also significant in history of vitrectomy, history of atopic dermatitis and unknown groups (Figure 2). After excluding the cases with overlapping of predisposing factors, the decrease of 1 month postoperative IOP in history of trauma group was still significant, while that in long eye axis group was not significant (Supplementary Table S2 online and Supplementary Fig. S1 online).

In the analysis for each group of the directions of lens and IOL deviation, the mean IOP of the cases with anterior lens deviation was significantly higher than that of the other cases before surgery (33.5 mmHg vs. 17.5 mmHg; p<0.001, Mann-Whitney U test), and showed a significant decrease at 1 day, 1 week and 1 month after surgery (p<0.001, mixed-effect model) (Table 1, Figure 3). The mixed-effect model analysis by the direction of lens and IOL deviation showed that there are also significant decreases in the IOPs at 1 week and 1 month after surgery in downward IOL deviation group, and at 1 month after surgery in upward lens deviation and IOL fall into the vitreous cavity groups (Figure 3).

In 93 of the 129 cases whose eye drop scores were available, both scores before and after surgery were zero (Supplementary Table S3 online and Supplementary Fig. S2 online). In 10 cases, the score after surgery decreased to zero from before surgery; in 3 cases, decreased but the score after surgery was ≥1; in 12 cases, increased; in 11 cases, scores before and after surgery were the same (≥1).

Discussion

The indications for IOL intrascleral fixation included long eye axis (20.3%), PE (18.6%), trouble in surgery (17.8%), history of trauma (16.9%) and so on; however, in 24.6% of cases, surgery was performed for unknown causes. These unknown causes may include causes that were not identified in the interview, but numerous genetic disorders and other causes may have been missed.

In addition, it was observed that 23.7% of cases had overlapping predisposing factors. Among them, the case with both PE and trouble in surgery was one of the most common. It was reported that the prevalence of PE in a Japanese population was 3.4%,¹³ and it is also known that PE is one of the causes of intraoperative problems during a cataract surgery.¹⁴ Therefore, the observation of many cases with both PE and trouble in surgery is convincing. The case with both long eye axis and history of vitrectomy was also one of the most common cases with overlapping predisposing factors. It was reported that the mean eye axial length for the patients with IOL dislocation after lens replacement surgery was 25.6 mm,⁹ so a history of vitrectomy might be relevant to a long eye axis. On the other hand, considering the previous report that 15.2% of junior high school students in Japan have an eye axis length of 26 mm or longer,¹⁵ it seems that the number of persons with long eye axis is much larger than those with the other predisposing factors. However, only 16 of 48 cases with long eye axis had no other predisposing factor. This result suggests that a patient with long eye axis complicated by the other predisposing factor may tend to undergo IOL intrascleral fixation more often than with long eye axis alone, even though a patient with only long eye axis may necessitate IOL intrascleral fixation.

In total, there were more than twice as many male cases as female cases. In contrast, males were more than three times as many compared to women in the history of trauma, atopic dermatitis, and vitrectomy groups. In Japan, the number of male patients with rhegmatogenous retinal detachment is approximately twice that of female patients. ¹⁶ In this study, the number of male patients was also higher than that of female patients. It is believed that males are more active than females and therefore suffer more trauma. Although atopic dermatitis is more common in females than in males,¹⁷ more males had atopic dermatitis than females in this study. Although the number of patients with RP in Japan is not sex-dependent¹⁸; in this study, RP was more common in females. However, the results of this study cannot be considered definitive due to the small sample size.

In the cases of lens deviation, anterior and fall into vitreous cavity are most often seen. On the other hand, downward and fall into vitreous cavity are most popular in the case of IOL deviation. Lens dislocation in Marfan syndrome is usually bilateral and most often occurs in the superotemporal direction, although other directions are not uncommon.^19,20 Downward deviation and fall into vitreous cavity were more common in this study, and it is most likely that the weight of the lens placed strain on the superior ciliary zonule throughout life. In addition, regarding IOL deviation after pars plana vitrectomy, it has been suggested that extensive peripheral vitrectomy probably damages the zonular fibers and resulted in the dislocation of the IOL.⁹ The reason why there are many aphakia cases with PE or trouble in surgery is that they were referred to our clinic after cataract surgery performed at other hospitals, and intraoperative problems prevented IOL insertion. In the trauma cases, the direction of deviation also varied, perhaps because of the various directions of impact.

In this study, we found that IOP decreased in the short term (1 month postoperatively) compared to the preoperative period as a whole. Cases with upward and anterior deviation of the lens, IOL fall into the vitreous cavity, and downward deviation of the IOL demonstrated significant decrease in IOP after surgery, whereas there were no significant differences between the preoperative and postoperative IOPs in cases with aphakic eyes and no dislocation. Crystalline lenses and IOL dislocation in chambers may be linked to hypertension, which can be attributed to two main factors: circulatory disturbances of the aqueous humor and inflammation. Abnormalities in the position of the lens and IOL may cause retention of aqueous humor, which may inhibit smooth circulation and increase IOP. In particular, a significantly high preoperative IOP was observed in the cases with anterior lens deviation of this study and surgery resulted in good IOP reduction. Cases with anterior lens deviation are prone to IOP elevation due to pupillary block. In fact, it has been reported that lens subluxation is often misdiagnosed as angle closure glaucoma.²¹

Residual lens material in the eye is also known to cause high IOP. The first is phacolytic glaucoma, which occurs when the lens protein itself and the macrophages that phagocytose it obstruct the outflow of aqueous humor.²² The other is phacoanaphylactic glaucoma, which is secondary to lens-induced uveitis, caused by an immune response to lens proteins.²³ In some cases, including those with intraoperative cataract problems, there may have been residual lens material in the eye, causing the inflammation described above and elevated IOP.

The observations of significant differences between preoperative and postoperative IOPs in history of vitrectomy and long eye axis groups might be due to many cases of vitreous cavity and downward deviation in these groups, whereas many cases of aphakia and no deviation might result in no significant IOP change in PE or trouble in surgery groups. After excluding the cases with overlapping of predisposing factors, the decreases of postoperative IOP in history of vitrectomy or long eye axis groups are not remarkable due to the small sample sizes. The cases with history of trauma showed significant differences in IOP before and after surgery, and most of the cases had lens dislocations in various directions (not necessarily aphakia or no deviation). These results support the idea that the presence of intraocular residues influences the increase in IOP.

We were able to examine eye drop score in about 70% of the cases in this study, and in almost all cases eye drop score was zero both preoperatively and postoperatively. We believe that the influence of eye drop score is not so strong.

It should be noted that IOL intrascleral fixation does not lower IOP; rather, patients who require IOL intrascleral fixation are likely to have elevated IOP for some background reasons, and intrascleral fixation is not recommended for lowering IOP. The effectiveness of combined treatments such as IOL fixation plus the implantation of the Ahmed glaucoma drainage device has also been reported for treating ocular hypertension in conjunction with IOL fixation.²⁴ Trauma-induced ocular hypertension has also been investigated through various mechanisms.²⁵ When deciding on a surgical procedure, it is necessary to carefully examine whether surgery improves symptoms.

The limitations of this study are as follows. First, the day after surgery, IOP was measured in the ward with GAT; however, in the outpatient setting, GAT and NCT were mixed and were not measured by a single examiner. However, GAT and NCT are thought to be correlated.^26,27 Second, long-term changes and the development of complications were not included in this study. In many cases, patients referred for IOL intrascleral fixation were then referred back to the original institution relatively early after surgery; therefore, long-term follow-up was not available.

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Predisposing factors, direction of dislocation, and changes in intraocular pressure after intrascleral intraocular lens fixation surgery

Abstract

Introduction

Materials And Methods

Results

Discussion

Conclusion

Declarations

References

Tables