Abstract
AIM
To investigate the frequency of idiopathic phacodonesis (IP) in senile cataract subjects and the short-term clinical outcomes following cataract surgery.
METHODS
This institutional case-control study included 1301 consecutive low-income cataract subjects from June to November 2009. Anterior segment were carefully evaluated with dilated pupil under slit-lamp. IP were screened and graded by a criteria set by the authors. Risk factors, surgical outcomes, and operative complications were analyzed.
RESULTS
A total of 42 subjects (3.2%) with IP were diagnosed and classified as grade 1 (36 subjects), grade 2 (5 subjects) and grade 3 (1 subject). Harder lenses and intumescent cataracts were observed in the IP group than the control group (P<0.05). Logistics regression test also indicated the main risk factor was the hardness of the lens. The incidence of zonular dialysis during surgery was 23.8% (10 eyes), which was significantly higher than the controls (0.7%, P<0.001). Visual outcomes of the two groups were not statistically or clinically significant.
CONCLUSION
Hard nucleus and intumescent cataract are related to IP in senile cataract subjects in Qinghai, China. With more care being taken, grade 1 and some of the grade 2 IP subjects achieved similar surgical outcomes as compared to controls.
Keywords: phacodonesis, lens nucleus, zonular dialysis
INTRODUCTION
Phacodonesis is present if lens trembled upon movement of the eye during slit-lamp examination[1]. Zonular apparatus is the main support system of human lens, weakness in the zonules could cause instability of the lens, leading to complication during cataract extraction surgery. Phacodonesis is the major sign of weakness of the zonular apparatus[1],[2]. In severe cases, iridodonesis, subluxation or dislocation of the lens could be noted.
While many studies have documented pseudoexfoliation syndrome as a cause of weakness in the zonular apparatus[1],[3]-[5], other reports indicated that injury, laser[6], vitrectomy, glaucoma surgery, glaucoma[7], uveitis, aging, retinitis pigmentosa[8], diabetes, Marfan's syndrome[9], homocystinuria[10] and Weill-Marchesani syndrome[11],[12] could also weaken the lens apparatus. There remains some phacodonesis cases without known cause[13].
During the period from June to November 2009, the Chinese Lifeline Express Medical Team, an organization aimed to cure blindness from cataract for the poor, was in Qinghai province. Qinghai is a located in north-east of the Qinghai-Tibet Plateau. Due to high altitude and high ultraviolet radiation intensity, the incidence of age-related cataract is 0.3%. Cataract is the most common cause of blindness and visual impairment among adults. As members of this team, we found some cases of phacodonesis in cataract subjects without the above known causes, so we named this “idiopathic phacodonesis (IP)”. We focused on studying the clinical features, risk factors and surgical outcomes of this disease.
For economic and other reasons, the study could only be conducted for a short period, and long-term follow-up was not possible. Further study on the pathology of IP and long-term evaluation on the surgical outcomes will published in future reports.
MATERIALS AND METHODS
Materials
Subjects for this study were collected from a general ophthalmology practice in a group-model health maintenance organization,Lifeline Express. 1523 low-income cataract subjects were recruited by Qinghai Health Bureau from all districts of Qinghai province. Most of them were of Han ethnicity, (763, 50.1%), other ethnicities included were Hui (239,15.7%), Sara (181,11.9%), Tibetans (167,11.0%), Tu (110,7.2%), and Mongolians (63,4.1%) minorities. Detailed past medical history was collected including diabetes, hypertensive disease, ocular trauma, ocular surgery, refractive error and ocular disease.
Methods
All subjects underwent a complete ophthalmologic examination including best-corrected visual acuity (BCVA), slit-lamp evaluation of the anterior segment with dilated pupils, detailed fundus assessment, B-mode ultrasound and contact A-scan ultrasound for axial length measurements. Phacodonesis was diagnosed during the preoperative dilated slit-lamp examination by one doctor and confirmed by another. The information of lens nucleus hardness (which was graded by Emery and Little[14] system), intraocular pressure, retinal pathology, axis length, lens stability and intraoperative complications were recorded immediately. Subjects with pseudoexfoliation, uveitis, diabetes mellitus, ocular trauma, previous ocular surgery, glaucoma, Marfan's syndrome, high myopia and other known disease which could cause lens dislocation were excluded in this study. Also, Morgagnian cataract which could cause the movement of the nucleus alone was excluded.
We established the criteria to grade the IP. Grade 1, phacodonesis could be found by careful slit-lamp examination, without iridodonesis or visible zonular dialysis; Grade 2, phacodonesis could be easily noticed by slit-lamp examination, with or without iridodonesis, also no zonular dialysis noticed; Grade 3, phacodonesis could be easily noticed by slit-lamp examination, acompanied by iridodonesis and zonular dialysis and even dislocation of the lens. According to Lifeline Express policy, only one eye could be operated in this program for each subject, so our study only included the operative eyes.
Surgery was performed mostly using topical anesthesia with a few subjects having retrobulbar anesthesia. Preoperatively, subjects were given 1 drop each of tropicamide 1%, phenylephrine 0.25%(Mydrin-P), oxybuprocaine hydrochloride 0.04% (Benoxil), and repeated every five minutes for four sets. All cases underwent a superior 5.5mm or more scleral pocket incision, 0.06% trypan blue (Aurolab, India) 0.1mL was injected into the anterior chamber to stain the capsular if necessary and continuous curvilinear capsulorhexis (CCC), hydrodissection, and hydrodelineation followed by phacoemucification or extracapsular cataract extraction (ECCE) was performed depending on the the hardness of nucleus classification. (Nucleus hardness in all eyes was classified as grade1-5. Grades 4 and 5 were considered as hard nucleus in this article). After aspiration of the cortex, a PMMA (polymethyl methacrylate, Eye Good Medical Co. Ltd, Zhuhai, China) intraocular lens was implantated into the capsular bag. Anterior vitrectomy was performed when the posterior capsular was compromised and vitreous loss occurred. All operations were performed by two experienced ophthalmologists (W.H.Y & X.W.L). Due to the financial reason, majority of the subjects could be only accommodated and followed-up by our team for 3-7 days, Limited long-term follow-up information could be obtained from local health bureau.To evaluate the zonular apparatus, some of the subjects who were available and lived close to the train were evaluated by ultrasound biomicroscopy (UBM, Suowei Electronic Technology. Co. Ltd. China) preoperatively and 4 weeks postoperatively.
Statistical Analysis
Data were analyzed with SPSS 13.0 data processor for Windows. Means and standard deviations were used to compare age, axial length, and anterior chamber depth. Pearson chi-square tests were used to compare the baseline categorical characteristics and incidence of intraoperative complications between subjects with and without IP. A logistic regression model for multiple analyses subsequently was used. A P-value of less than 0.05 was considered statistically significant.
RESULTS
Total subjects included in this study were 1301. The mean age of subjects with idiopathic phacodonesis (IP) was 67.4± 9.8 years (range 40 to 84 years, 82 eyes of 42 subjects), including 18 males (42.9%) and 24 females (57.1%). The mean age of subjects without phacodonesis (the controls) was 66.4±10.1 years (range 41-91 years, 1259 eyes of 1259 subjects), including 584 males (46.4%) and 675 females (53.6%). The preoperative BCVA ranged from light perception to 0.3 on the Snellen Chart. Phacodonesis was observed bilaterally except in two subjects, one with dense corneal opacity and the other who had underwent remote enucleation in the other eyes. There were no significant difference in phacodonesis between the right eyes and the left eyes in all subjects (two independent samples tests, Mann-Whitney U test Z=-0.388, P=0.698). Only the 42 operated eyes were included in this study.
In our study, we identified 36 eyes with grade 1 phacodonesis, and 5 eyes with grade 2, 1 eye with grade 3. There was no difference between the mean age of the IP subjects and the controls (t=0.61, P=0.54). Neither did the mean axial length between the two groups differ (23.59±2.43mm in IP group & 23.50±2.33mm in control group, t=0.25, P=0.80). More eyes had harder nucleus (grade 4-5) in the IP group than those in the control group (Pearson chi-square test, χ2=7.26, P=0.007).In addition, more intumescent but not mature or hypermature cataract was observed in the IP group(Pearson Chi-square test, χ2=38.90, P<0.001,Table 1).
Table 1. Distribution of nucleus hardness grades and intumescent cataract in the IP subjects and the controls.
| Nucleus grade |
Cortex |
|||
| 1-3 | 4-5 | Non-intumecent | Intumescent | |
| IP | 16 | 26 | 27 | 15 |
| control | 517 | 742 | 1249 | 100 |
| χ2 | 7.26a | 38.90b | ||
a Pearson Chi-squared test, P=0.007 bPearson Chi-squared test, P<0.001
n
We identified several risk factors that may be associated with IP, including: age, sex, IOP, the depth of the anterior chamber, axial length, hardness of the lens nucleus, diabetes and cardiovascular diseases. We tested all these risk factors using logistic regression, which showed hardness of lens as the main risk factor (χ2=6,846, P= 0.011)associated with IP, and the logistic regression equation was logit P=-4.238+0.234X1. With an increase in lens hardness grade by one, the relative risk increases 1.28 times.
Zonular dialysis was found intraoperatively in 10 eyes (10/42,23.8%) and one of them (1/42,2.4%) developed vitreous loss during surgical procedure in the IP group. Up to 3 clock-hours of zonular dialysis occurred in 6 eyes (6/10,60%, 4 eyes with grade I IP, 2 eyes with grade 2 IP); up to 6 clock-hours of zonular dialysis was observed in 2 cases (2/10, 20%, 1 eye was grade 1 IP, 1 eye was grade 2 IP ); more than 6 clock-hours of zonular dialysis was seen in 2 cases (2/10 20%, one was grade 2 IP, and the other was grade 3), one of them with vitreous loss had anterior vitrectomy and no IOL implanted due to poor cooperation, the other without vitreous loss had scleral fixated IOL. Most common site of zonular dialysis was found in the inferotemporal or inferonasal quadrants (7 eyes), and a few were encountered in the superior quadrants (2 eyes). In control group, 9 eyes (0.72%) were found to have zonular dialysis. There was a significant difference in the incidence of zonular dialysis between the IP group and control group (Pearson Chi-square test, χ2=8.37, P<0.0001,Table 2).
Table 2. Intraoperative complications of the IP and control groups.
| Complication/IOL | IP (n=42) |
Control (n=1249) | |||
| Grade1 n=36 | Grade 2 n=5 | Grade3 n=1 | Total | ||
| ZDa | 5 | 4 | 1 | 10 | 9 |
| 3 CHs ZD | 4 | 2 | 0 | 7 | 8 |
| 6 CHs ZD | 1 | 1 | 0 | 2 | 1 |
| >6CHs ZD | 0 | 1 | 1 | 2 | 0 |
| Vitreous loss | 0 | 0 | 1 | 1 | 3 |
| Capsule rapture | 0 | 1 | 1 | 4 | |
| Suture fixed IOL | 0 | 1 | 0 | 1 | 2 |
ZD= zonular dialysis CHs= clock-hours aPearson Chi-square test, χ2=8.37, P<0.001
n
Phacoemulsification was performed in 812 subjects in the control group, and 19 in the IP group. ECCE was performed in 447 subjects in the control group and 23 in the IP group. In the IP group, 2 cases of zonular dialysis occurred with phacoemulsification, but 8 cases when ECCE was performed (Pearson Chi-square test, χ2=3.38, P=0.066) , in control group, 1 case with phacoemulsification and 8 with ECCE(Pearson Chi-square test, χ2=11.28, P=0.001, Table 3).
Table 3. Zonular dialysis in ECCE and phacoemulsification procedure.
| IP (n=42) |
Control (n=1459) |
|||
| PE | ECCE | PE | ECCE | |
| ZD | 2 | 8 | 1 | 8 |
| No ZD | 17 | 15 | 811 | 439 |
| Total | 19 | 23 | 812 | 447 |
| χ2 | 3.38 | 11.28 | ||
| P | 0.066 | 0.001 | ||
n
Follow-up period was limited to 3-7days. IOL dislocation was not observed in any subjects. Postoperative BCVA significantly improved from baseline, except in one subject whose BCVA remained at counting finger due to advanced age-related macular degeneration. There was no significant difference in the BCVA improvement between the 2 groups. Ultrasound biomicroscopy(UBM) was used to evaluate the zonular apparatus of 12 IP subjects and 23 controls who were available pre-and post-operation. Cross-sectional zonular UBM images were obtained circumferentially at eight evenly spaced locations.
UBM showed that grade 1 IP subjects' zonular apparatus appeared similar to controls (Figure 1); however, in some of the grade 2 IP subjects, the zonules were uneven, slack or elongated compared with the controls. And there is a gap between the iris and the lens, which could be a reason for phacodonesis and iridodonesis (Figure 2). After phacoemulsification, phacodonesis of the IOL became more pronounced, the gap between the lens and iris became larger than in preoperative images (Figure 3). In grade 3 eyes, the dialysis of the zonules and the dislocation of the lens were easily observed (Figure 4).
Figure 1. Grade 1 IP patient, the images of the zonles was as normal as normal zonular images, the iris and the lens were contact.
Figure 2. Grade 2 IP( the only one without intraoperative zonular dialysis), which showed the separation of the iris and the lens, although the zonular seemed as normal as that of the controls.
Figure 3. The same eye of Figure 2, postoperative zonules image, showed bigger gap between the iris and the lens, tensionless and lengthened of the zonules.
Figure 4. A grade 3 IP eye, which showed dialysis of the zonles and dislocation of the lens.
Transient postoperative high IOP was found in 3 cases of IP subjects, but all resolved within 3 days.
DISCUSSION
In 1970, Bartholomew[1] reported 7 cases (9 eyes) of phacodonesis after investigation of 300 cataract eyes and the fellow eyes of 195 subjects with displacement of the lens. Six of them were attributed to pseudoexfoliation, only one case was thought to be idiopathic phacodonesis. He assumed that phacodonesis was the transitory stage before complete lens dislocation. The prevalence of IP has not been reported in literature, the 3.2% prevalence in our study is among the selected cataract elder subjects in Qinghai province, including several ethnic groups. To determine the general prevalence, further studies are needed. Due to the small number in the IP group, we could not implicate if there is an ethnic or sexual predilection for IP.
In the literature, phacodonesis and dislocation of lens are mostly associated with pseudoexfoliation. In our study, most of the known risks to phacodonesis were excluded, the reason of instability of the lens is still not clear, so we named this sign “idiopathic phacodonesis” (IP). No poor papillary dilation was observed in the IP subjects, a sign commonly seen in pseudoexfoliation syndrome[15],[16].
The reason for weakness of the zonules remains unclear, but we found that hardness of the lens was one of the major risk factors, which should also be related to the age of the subject. But in our study, the relationship between IP and age was not significant. The authors presumed that is due to the small sample size of subjects with IP. Although intumescent cataract is not a risk factor for IP in logistics regression test in our study, the rates of intumescent cataract subjects in IP group was significantly higher than in the control group, so we still considered intumescent cataract to be closely related to IP. No difference was found in axial length or anterior chamber depth between the two groups. We hypothesize that hard nucleus and intumescent cataract could cause degeneration of the zonular apparatus, this will need pathological studies to confirm.
With UBM examinations, no abnormal image was observed in preoperative and uneventful surgery grade 1 IP eyes. However, in the grade 2 subjects, even though the preoperative zonules image appeared “normal”, some of the eyes showed non-contact of the lens and the iris, some of the eyes showed the elongated zonules. In postoperative images, there was discontinuity of the zonules, which could be due to damage of zonules during surgery.
Shingleton[17] found that 60% of subjects with zonular weakness confirmed by phacodonesis developed vitreous loss during surgery. Artzen et al[4] reported phacodonesis was significantly associated with capsular complication during cataract surgery. In our study, we also found that the IP subjects more frequently suffered from zonular dialysis (26.2%) during cataract surgery than the control group (0.7%). The more severe the phacodonesis was, the more likely for zonular dialysis occured during cataract surgery. Most of the zonular rupture in surgery occurred in the inferonasal or inferotemporal quadrants of eye, which is probably due to increased stress to inferior zonules during phacoemulsification or ECCE. With surgical tools such as capsular tension rings[18],[19] or surgical technique such as scleral-fixation IOL by experienced surgeons, most of the phacodonesis subjects could achieve good postoperative visual outcome[16]. In our study, capsular tension ring was not available, so for some subjects we performed scleral-fixated IOL implantation.
In this study, we found modern phacoemulsification could be safer for zonules than the ECCE in both IP (although not significant) and the controls. Katsimpris et al[20] also believe that phacoemulsification induces less stress on the zonules than ECCE. But, in our study, most ECCE surgeries were performed on brunescent and white cataracts which would be of challenge with either phacoemulsification or ECCE techniques[21].
Jehan et al[22] reported 8 of pseudoexfoliation eyes with late spontaneous intraocular lens dislocation 57-115 months after uneventful phacoemulsification in pseudoexfoliation syndrome. However, Nagashima[15] reported 67 eyes with pseudoexfoliation who had phacoemusificaiton, after a mean follow up of 54.1 months, no IOL dislocation was noted. For our subjects, we were not able to perform long-term follow-up, and some medical information can be obtained from the local health bureau which may provide further information related to long term surgical outcomes.
Phacodonesis in these subjects may be due to zonular degeneration, which was confirmed preoperatively by UBM and/or during surgery. Although only a small part of our subjects were available for UBM evaluation of their zonular apparatus, we still identified some clues of zonular fragility, such as: large gap between the iris and the lens, elongated and laxity of the zonules and even rupture of the zonules. To gain more detailed information by UBM, further study should be carried out.
As a sign of incipient lens dislocation, phacodonesis is significant and its recognition may be taken as an indication for lens extraction before actual dislocation, which can make surgery more challenging. If surgery is to be performed, outmost care should be taken to prevent uncontrolled lens displacement and possible vitreous loss, and these subjects should be operated on by experienced surgeons. Surgery procedure could be as safe as in controls when only mild phacodonesis (grade 1) is identified, but complication rate is significantly increased in advanced phacodonesis (grade 2 and grade 3).
Acknowledgments
The authors thank Dr. Lan Chang for editorial assistance. Many thank Dr. Jinlian Zhu, Dr. Ai Guo, and Lifeline Express officers and Qinghai Health Bureau officers for help in coordinating subject recruitment and schedules. Thanks to Dr. Gangwei Chen for his expertise in UBM.
Footnotes
Foundation item: Supported by Lifeline Express Hong Kong Foundation, China
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