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Hydrodissection combined with rotation cleans epithelial cells from capsular bag
The two procedures work synergistically to reduce the number of residual cells, potentially decreasing the risk of PCO.
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In cortical cleaving hydrodissection, fluid is injected directly under the anterior capsule, causing a visible fluid wave that passes around the equator of the lens, traversing between the posterior capsule and posterior cortex. This causes a cleavage between the lens capsule and the cortex.
Today, hydrodissection is accepted as an important surgical tool for adult and pediatric cataract surgery. In a cadaver eye study, Peng and co-authors noted that direct injection of fluid under the anterior capsule is particularly useful in removing equatorial lens epithelial cells (LECs). The beneficial effects of LEC removal on posterior capsular opacification are also seen in a study in adults that we have submitted elsewhere for peer review.
Hydrodissection is generally followed by rotation to confirm the separation of the cataract from the capsular bag. We believe that the synergy of hydrodissection followed by rotation of the nucleus within the capsular bag effectively scrapes the LECs off the capsule, especially those lying deep in the fornices of the capsular bag in the pre-equatorial region. This also causes detachment of the residual cortical fibers from the equatorial cells.
To test this hypothesis, we designed a study to evaluate the impact of hydrodissection alone and hydrodissection combined with rotation on the removal of lens epithelial cells and residual cortical fibers from the equatorial cells.
Methodology
This experimental laboratory study was performed on 20 human cadaver eyes (10 pairs) between 55 and 65 years old obtained from the Shamariya Eye Bank in Ahmedabad, India. The eyes were collected within 4 hours of death. A single eye from each pair was assigned to the control group in which no hydrodissection and no rotation were performed. The other eye was randomized to hydrodissection alone (group 1) or hydrodissection combined with rotation (group 2).
All eyes underwent a standardized surgical procedure of clear corneal incision, 360° iris removal and continuous curvilinear capsulorrhexis. In the control group, no cortical cleaving hydrodissection was done, only hydrodelineation was performed.
In group 1, cortical cleaving hydrodissection was performed. The complete hydrodissection was assumed to correspond to a continuous fluid wave that passed circumferentially between the capsule and the cortex and reached the end opposite to the site of fluid injection. Nucleus decompression was done as soon as the wave and a forward bulge of the nucleus were noted.
In group 2, after cortical cleaving hydrodissection was performed as mentioned above, the nucleus was rotated with a spatula introduced through the paracentesis. After decompressing the nucleus, the nucleus was turned counterclockwise until complete rotation was achieved. Complete nucleus rotation was performed three times.
The nucleus was then emulsified using the Alcon Legacy Series 20000 phacoemulsifier. Bimanual irrigation and aspiration were performed. The endpoint of surgery in all groups was absence of any visible lens matter (nucleus and cortex) in the capsular bag. The viscoelastic (methylcellulose) was injected in the anterior chamber. The cornea was removed. The empty capsular bag was filled with the viscoelastic and detached by excising the zonules around 360°.
The capsular bag was cut with the help of scissors into seven or eight flaps, extending from the rhexis margin to the equator. The entire bag was flattened and fixed on a slide and stained with hematoxylin-eosin. Stained capsular flaps were observed under a laboratory microscope, and photographs were taken with the help of a Sony CCD camera attached to the microscope (Figures 1, 2 and 3). Image analysis was performed to calculate the area of loss of LECs and the area of presence of residual cortical fibers in the pre-equatorial and equatorial zones in all the groups.
The Mann Whitney U and the Wilcoxon signed ranks tests were applied to find the difference between group 1 and group 2.
The mean age of the eyes was 60.06 ± 3.12 years in group 1 and 59.69 ± 4.23 years in group 2. In the control group, area of cell loss in the pre-equatorial and equatorial zones was 3.9% ± 3.2 and 2.7% ± 0.8 respectively; presence of residual cortical fibers was 83.8% ± 1.7.
In the Table, the comparison of the area of cell loss in the pre-equatorial zone and equatorial zone and residual cortical fibers attached to the equatorial cells in group 1 and group 2 are reported.
Discussion
During cataract extraction we maintained a closed chamber in the cadaver eye to simulate the surgery in live patients. In this way the effect of the hydrodissection procedure on rotation would be comparable. Most surgeons perceive rotation as a confirmatory test to gauge the effectiveness of cortical cleaving hydrodissection in separating the cataract from the capsular bag. As a result, they just nudge the nucleus to make sure that it is free from the capsular bag. We performed complete rotation three times, despite the practiced method of rotating the nucleus 180° or 360°. Our aim was to scrape the LECs from the capsule, not just to confirm separation of the cataract from the bag. Complete rotation of the nucleus three times facilitates cell loss by friction. To perform rotation, the surgeon does not need to modify the technique he is conversant with; ie, the surgeon can use any instrument and approach from either the side port or the main incision, as long as complete rotation is performed three times.
The residual cortical fibers begin in the equatorial zone and continue to the pre-equatorial zone. Those at the lens bow region have the potential to grow across the visual axis and cause posterior capsular opacification. Peng and co-authors have mentioned that when the surgeon leaves behind peripheral cortical fibers this increases the possibility of development of PCO as there remain a large number of mitotically active cells that have the potential to grow across the visual axis. It would be interesting to perform a clinical study to evaluate the impact of PCO in patients with leftover residual cortical fibers.
The results of this experiment suggest that significant removal of LECs leaves only a small amount of cells available to participate in mitotic division, proliferation and migration across the visual axis. This could retard the incidence of posterior capsular opacification. In developing nations, cortical cleaving hydrodissection combined with rotation can be done even when performing extracapsular cataract extraction. This could prove useful in developing countries as access to Nd:YAG lasers for capsulotomy is limited.
This study suggests that rotation should be done not only as a confirmatory test to gauge the effectiveness of cortical cleaving hydrodissection in separation of the cataract from the capsular bag. Instead, hydrodissection combined with rotation should be regarded as a procedure to separate lens epithelial cells from the capsule. This study has shown that cortical cleaving hydrodissection combined with rotation removes the LECs in significant quantities in the pre-equatorial region. We advocate the synergy of hydrodissection and rotation.
For Your Information:
- Abhay R. Vasavada, MS, FRCS, can be reached at Iladevi Cataract and IOL Research Centre, Raghudeep Eye Clinic, Gurukul Road, Memnagar, Ahmedabad - 380 052 India; +91-79-27492303 or 27490909; fax: +91-79-27411200; e-mail: shailad1@sancharnet.in. The authors have no direct financial interest in the companies or products mentioned in this article.
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