|Year : 2018 | Volume
| Issue : 2 | Page : 202-206
Influence of the shape of Nd:YAG capsulotomy on visual acuity and refraction
Hazem M El-Feky1, Waheed M Orouk1, Rana H Ahmed2
1 Ophthalmology Department, Faculty of Medicine, Banha University, Banha, Egypt
2 Ophthalmology Department, Damanhour Medical National Institute, Damanhur, Egypt
|Date of Submission||03-Nov-2017|
|Date of Acceptance||15-Mar-2018|
|Date of Web Publication||17-Aug-2018|
Dr. Rana H Ahmed
Gharbia Kafr El Zayat, El Malal Street Infont of El Hoda Mosque, 2 Elmalah at Infront of el Hoda Mosque, Kafr Elzayat City, Elgharbia Government, 31611
Source of Support: None, Conflict of Interest: None
Background Posterior capsule opacification (PCO) is a common complication after cataract surgery. The need for PCO prevention becomes increasingly important. During the past decades, various forms of prevention have been examined, including general measures during surgery, pharmacological prevention, and by interfering with the biological processes of epithelial mesenchymal transformation (EMT) in lining epithelial cells (LECs). The first-line treatment option is posterior capsulotomy performed with a neodymium:yttrium–aluminum–garnet (Nd:YAG) laser. To evaluate the influence of the size and shape of Nd:YAG laser capsulotomy on visual acuity and refraction.
Patients and methods We evaluated 20 eyes of 20 patients treated with Nd:YAG laser posterior capsulotomy for PCO. Patients were divided into two groups according to the shape of capsulotomy: patients with cruciate shape capsulotomies with openings of more than 3 mm (group 1) and patients with circular shape capsulotomies of more than 3 mm.
Results The mean number and energy of laser firings were significantly higher in group 2 and significantly lower in group 1 (P=0.011). In the preprocedural spherical equivalent, there was no statistical significance between the two groups (P=0.971). In the postprocedural spherical equivalent also there was no statistical significance between the two groups (P=0.643). Significant change in intraocular pressure following capsulotomy was observed in group 2 (P=0.011), but there was no significant change in group 1. A higher number of patients in group 2 and a lower number of patients in group 1 report floating bodies after YAG laser capsulotomy (P≤0.050 significant). Regarding floating bodies there was statistical significance between the two groups (P=0.025). Best-corrected visual acuity highly significantly improved following capsulotomy in both the groups (P≤0.001).
Conclusion Cruciate shape capsulotomy provides improvement in visual function with minimal complications.
Keywords: cataract extraction, crystalline, intraocular, laser therapy, lens capsule, lens, ocular, phacoemulsification, refraction, visual acuity
|How to cite this article:|
El-Feky HM, Orouk WM, Ahmed RH. Influence of the shape of Nd:YAG capsulotomy on visual acuity and refraction. Benha Med J 2018;35:202-6
|How to cite this URL:|
El-Feky HM, Orouk WM, Ahmed RH. Influence of the shape of Nd:YAG capsulotomy on visual acuity and refraction. Benha Med J [serial online] 2018 [cited 2018 Oct 18];35:202-6. Available from: http://www.bmfj.eg.net/text.asp?2018/35/2/202/239192
| Introduction|| |
Posterior capsule opacification (PCO) was the most common visually disabling complication of the present cataract surgery .
However, there has been a gradual and unobserved decrease in its incidence and subsequent neodymium:yttrium–aluminum–garnet (Nd:YAG) laser capsulotomy rates over the past decade. This has been attributable to advancements in the technique of cataract surgery, appreciation of the importance of thorough cortical clean up, and better intraocular lens (IOL) designs and biomaterials .
However, PCO rates may be much greater in developing countries, where a sizeable population still has restricted access to phacoemulsification and modern IOLs .
Nd:YAG laser capsulotomy showed itself to be an efficient alternative to surgical dissection, avoiding such complications such as endophthalmitis as well as vitreous loss. Improvement in visual acuity after Nd:YAG laser capsulotomy in patients with significant PCO has been well documented. Improvements in glare and contrast sensitivity may also be significant outcome measures for many patients .
Although Nd:YAG laser capsulotomy is believed as the standard treatment for PCO and has been found to be safe and effective, it is not without complications, some of which can be sight threatening such as retinal edema and detachment. Numerous studies have described damages in the IOL, increased intraocular pressure (IOP), glaucoma, retinal hemorrhage, iritis, vitreous prolapse, corneal injury, vitritis, pupil blockage, hyphema, cystoid macular edema, retinal detachment, IOL dislocation, or exacerbation of endophthalmitis .
A number of Nd:YAG laser capsulotomy shapes and sizes may be utilized. Cruciate and circular shapes are most commonly performed with a wide range of opening sizes (3–6 mm) .
Specific capsulotomy shapes and sizes confer particular advantages and disadvantage .
| Patients and methods|| |
In this study, 20 eyes of 20 patients were treated with Nd:YAG laser posterior capsulotomy for PCO.
Eyes were divided into two groups according to the shape of capsulotomy:
- Group 1 consists of 10 eyes with cruciate shape capsulotomies with openings of more than 4 mm.
- Group 2 consists of 10 eyes with circular shape capsulotomies with openings of more than 4 mm.
All patients had PCO after phacoemulsification and IOL implantation.
Patients with ocular (corneal opacity − glaucoma − retinitis pigmentosa) or systemic diseases (diabetes
mellitus hypertension) that are likely to affect vision were excluded from the study.
History of lens implantation
The interval between iol implantation and tag laser capsulotomy.
- Visual acuity and refraction.
- IOP recording.
- Slit lamp examination.
An ophthalmic Nd:YAG laser with capsulotomy contact lenses (double aspheric capsulotomy lens; Volk, USA).
The following were carried out for the patients
- Explaining the procedure to the patient
- The patients were informed about the purpose of the procedure, duration, painless nature, and importance of maintenance of steady fixation.
- They may hear a small clicking noise produced by the acoustic waves generated.
- Antiglaucoma medication
- Brimonidine tartrate (0.2%): one drop 1 h before the laser procedure to protect one from the immediate postoperative IOP spike.
- Pupillary dilation (mydriasis)
- Dilation was done by a mydriatic such as tropicamide 1.0%, phenylephrine 2.5%, or cyclopentolate 1–2%.
- Topical (lignocaine 4% or preferably proparacaine HCl 0.5%).
- Comfortable sitting of the patient
- Steady fixation obtained by:
- Use of a head strap to prevent patients’ tendency to pull back his/her head during the procedure.
- Suitably adjusting illuminated target.
Illumination of the room
The laser room should be darkened/semidarkened to improve the surgeon’s visualization of the target and consequent accurate focusing of the laser beam.
It should be narrow and obliquely angled. As the Nd:YAG laser is actually invisible, a helium–neon laser is actually used as a focusing device.
Proper capsulotomy technique
Method of focusing to avoid intraocular lens pitting
Posterior defocusing: In pseudophakic eyes, to avoid IOL pitting intentionally focus posterior to posterior capsule (posterior defocusing) to cause optical breakdown in the anterior vitreous. The shock wave radiates forward and ruptures the posterior capsule instead of the uniform anterior vitreous face, the breakdown threshold of which is higher than an optical interface like the posterior capsule. This is conveniently done by the posterior defocus setting in the YAG laser.
Pattern of capsulotomy opening
- Cruciate shape capsulotomies with openings of more than 4 mm ([Figure 1]):
Create a cruciate opening, beginning superiorly near the 12 o’clock position and progressing downward toward the 6 o’clock position.
Unless a wide opening has already developed, shots are then placed at the edge of the capsule opening, progressing laterally toward the 3 and 9 o’clock positions.
- Circular shape capsulotomies with openings of more than 4 mm ([Figure 2]):
Refraction, spherical equivalent (SE), best-corrected visual acuity (BCVA), and IOP were compared within groups and between groups prior to at 1 week following capsulotomy. The number and energy of laser firings, and the number of patients reporting floating bodies, and any complications were recorded.
| Results|| |
[Table 1],[Table 2],[Table 3],[Table 4],[Table 5].
| Discussion|| |
In the present study, we found that the interval between cataract extraction and performing Nd:YAG laser capsulotomy in our study was 1.90 years. In Hasan et al.  the interval was 2.49 years and in the study done by Kundi and Younas  it was 24 months .,
Increased IOP was reported in 15–30% of patients in different studies .
In a study done by Petal et al. , it was observed that 36% of the patients showed no change in IOP, while 64% patients showed elevated IOP. Among these, 59% patients show a rise in IOP that was up to 5 mmHg while only 5% of the patients had a rise of IOP more than 5 mmHg. Most of these patients achieved their baseline IOP within 1 day and only 7% patient had a rise in IOP compared with baseline IOP on day 1. None of the patients show elevated IOP after 1 week, but in our study there was elevation in IOP but within the normal range. Hassan et al. and Kraff et al.  reported an average rise in IOP of 6 and 3.5 mmHg after laser capsulotomy, respectively. Channell et al.  Morique Leys et al.  and Shubert et al.  reported more than 10 mmHg of IOP rise in 59, 29, and 15% cases, respectively .
The incidence given by these authors and those found in our study are variable which may be due to the use of higher energy and larger capsulotomy as explained in their studies. Various other factors documented in different studies explain for the rise of IOP after laser capsulotomy such as the presence or absence of IOL, sulcus or bag fixation of IOL, pre-laser IOP, glaucomatous patients, different time period of IOP recording, type of PCO, size of capsulotomy, initial pulse energy, and treatment given .
Shetty et al. , who noted that the IOP rise was within the normal range and hence was observed and no intervention was done and the same noted in our study.
As regards SE, in this study no significant change in SE following capsulotomy was observed and the same noticed in Peter and Naeser .
Also Cetinkaya et al.  noticed that SE is usually not affected by the size and shape of capsulotomy.
On the other hand, Shetty et al.  and Karahan et al.  observed that a larger capsulotomy causes more backward movement with a hyperopic shift.
Outcomes and effects of Nd:YAG laser capsulotomy used for PCO depend on several factors, including the size of capsulotomy, the amount of energy, and IOL design .
Regarding visual acuity Nd:YAG laser posterior capsulotomy improved visual acuity in 83–96% of eyes in Steinert study .
In our study, the BCVA was improved after YAG laser posterior capsulotomy, but there was no statistical differences between groups the same was noticed by Cetinkaya et al. .
Erisa et al.  proved that Nd:YAG laser capsulotomy enabled a significant improvement in visual function even in patients with PCO with good visual acuity.
In a study done by Bari , they proved that Nd:YAG laser capsulotomy for PCO is safe, effective, and a rewarding procedure for improvement of vision. The same is observed in our study.
The study by Petal et al.  was favored by studies conducted by Slomovic et al.  Kraff et al., Dawood et al.  Holwegar, Mahtab et al.  who noted that there is no statistically significant linear correlation between the rise of IOP and total energy used. But our study has found significant correlation between IOP elevation and energy and the same was observed by different studies conducted by Stark et al., Mohammad et al., Channell et al., who postulated that higher energy levels tend to cause higher rise in IOP .
Cetinkaya et al.  found the amount of energy used and the proportion of patients complaining of floaters was significantly higher in large sized circular shape capsulotomy. The same result was found in our study.
Kara et al. , noticed that the circular technique is associated with a higher amount of energy used, more floater symptoms, and the same was found in our study.
| Conclusion|| |
Nd:YAG laser capsulotomy is effective, relatively safe, noninvasive, fast, outpatient procedure in the treatment of PCO. Nd:YAG laser posterior capsulotomy provides excellent outcome in terms of improvement in BCVA. Nd:YAG laser capsulotomy is associated with a rise in IOP. The rise in IOP is transient in natural as that elevation subsided within 1 week. Floaters are more frequently reported, and the amount of energy used is higher, in circular shape capsulotomies. Cruciate shape capsulotomy provides improvement in visual function with minimal complications.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]