Impact of high and low aspiration parameters on postoperative outcomes of phacoemulsification: Randomized clinical trial

Phacoemulsification using an active fluidics system at physiologic vs high intraocular pressure: impact on anterior and posterior segment physiology

PURPOSE

Evaluate the impact of high vs low intraoperative intraocular pressure (IOP) during phacoemulsification on anterior and posterior physiology.

SETTING

Private practice in Des Moines, Iowa.

DESIGN

Prospective, randomized, paired-eye clinical trial of patients anticipating bilateral cataract surgery.

METHODS

27 participants randomized at the time of their first cataract surgery to either low IOP or high IOP group. The subsequent cataract surgery was performed under the alternate condition. During phacoemulsification and cortex removal, IOP was maintained either at low (≤28 mm Hg) or at high (≥55 to 60 mm Hg) levels. The primary outcome was fluid usage, with secondary outcomes of central corneal thickness, foveal avascular zone area, foveal and macular thickness, endothelial cell density (ECD), and postoperative inflammation.

RESULTS

Surgery with low IOP settings used less fluid (40.0 mL vs 55.6 mL, P < .0001). Corneal thickness changes were smaller in low IOP eyes at 1 day and 1 week (3.0% vs 8.1%, P = .01; 3.1% vs 4.4%, P = .01) but were similar by 1 and 3 months. ECD dropped less in low IOP eyes at 1 and 3 months (-1.7% vs -12.3%, P = .001, 2.1% vs -8.9%, P = .0003.) IOP remained a significant predictor of ECD change when relationship was controlled for fluid use and phacoemulsification energy. Retinal parameters did not vary among all eyes or when compared by IOP setting. Visual acuity was similar at all timepoints.

CONCLUSIONS

Low IOP settings resulted in less inflammation and less corneal trauma, as evidenced by a smaller drop in ECD and less postoperative corneal edema, when compared with high IOP settings. Retinal parameters did not change significantly. The different outcomes did not result in a difference in visual acuity.

Systematic and objective wet-lab testing of instruments for phacoemulsification: new Formalin Quadrant Model

PURPOSE

To validate an improved wet-lab model for systematic and objective efficiency testing of instruments for phacoemulsification.

SETTING

Institute of Medical Engineering, Lucerne University of Applied Sciences and Arts, Lucerne, Switzerland.

DESIGN

Experimental study.

METHODS

Porcine lenses were incubated for different time spans in formalin to simulate different cataract densities. Lenses were cut in quadrants and emulsified in a silicone test chamber. The use of ultrasound was restricted to full occlusion and the minimal power needed to promote emulsification. Equivalence to the surgical situation and cataract consistency were judged by an experienced surgeon. Efficiency was rated by effective phacoemulsification time, liquid consumption, and total surgery time.

RESULTS

Formalin incubation times of 2 hours, 1.25 hours, and 0.5 hours were validated for hard, middle-hard, and soft cataracts, respectively. Systematic testing of different fluidics settings revealed the unique opportunities of the improved model: Experiments could be performed by laboratory staff without any surgical experience after a short training, and the model provided results in a fast and reproducible manner. Reduced effective phacoemulsification time, shorter total surgery time, and less liquid consumption were observed with higher fluidics settings, confirming and complementing earlier clinical findings.

CONCLUSIONS

The Formalin Quadrant Model can be used to test new designs of instrumentation on different cataract densities or various instrument settings for efficiency. Using a validated cataract substitute, it closely represents the clinical situation and thus renders valid results in a short time. Instruments can be tested and improved profoundly before costly and elaborate clinical trials have to be applied.

Effect of elevated irrigation bottle height during cataract surgery on corneal endothelial cells in porcine eyes

BACKGROUND

Cataract surgery induces corneal endothelial cell loss (ECL). This study investigates the relationship between bottle height (BH) and ECL induced due to irrigation and aspiration (I/A) in cataract surgery and quantifies protective effects of intraoperatively used ophthalmic viscoelastic substances.

METHODS

Intermittent I/A without phacoemulsification was performed in porcine eyes for 10 min with varying BHs of 100 cm (BH100), 125 cm (BH125), 150 cm (BH150) or no treatment (control, no I/A). Additionally, in one group a dispersive ophthalmic viscoelastic substance was injected into the anterior eye chamber before treatment with I/A at a BH of 150 cm (BH150 + V). After exposure of the corneal endothelium to I/A, the corneas were prepared to split corneal buttons on day 0 and cultivated for 15 days. Endothelial cell density (ECD) was analyzed blinded on days 1, 8 and 15.

RESULTS

Relative ECL significantly correlated with irrigation BH (control (n = 13): -9.69 ± 6.03% (average ± standard deviation); BH100 (n = 12): -9.69 ± 4.81%-p = 1.000; BH125 (n = 14): -19.44 ± 7.30% - p < 0.001; BH150 (n = 13): -21.99 ± 6.70%-p < 0.001). I/A-induced ECL was significantly decreased by the injection of ophthalmic viscoelastic, as BH150 + V (n = 14; -10.92 ± 4.09%-p = 1.000) showed a cell loss comparable to the control group.

CONCLUSIONS

ECL is altered by I/A BH and reduced when viscoelastic substances are used.

Comparative anatomical outcomes of high-flow vs. low-flow phacoemulsification cataract surgery: A systematic review and meta-analysis

Background

Phacoemulsification is an effective and widely performed technique in cataract surgery, but the comparative anatomical outcomes, including endothelial cell loss (ECL), central corneal thickness (CCT), and central macular thickness (CMT), between high-flow and low-flow phacoemulsification cataract surgery remain unclear.

Methods

This study followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement. Random-effects models were applied to measure pooled mean differences (MD) with 95% confidence intervals (CI) of anatomical outcomes between high-flow and low-flow phacoemulsification cataract surgery. We judged overall certainty of evidence (CoE) based on Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria.

Results

We included six randomized controlled trials (RCTs) totaling 477 participants. The meta-analysis showed similar changes associated with these two surgery types in both ECL at postoperative days 2–14 (MD: −1.63%; 95% CI: −3.73 to 0.47%; CoE: very low), days 15–42 (MD: −0.65%; 95% CI −2.96 to 1.65%; CoE: very low) and day 43 to month 18 (MD: −0.35%; 95% CI: −1.48 to 0.78%; CoE: very low), and CCT at postoperative day 1 (MD: −16.37 μm; 95% CI: −56.91 to 24.17 μm; CoE: very low), days 2–14 (MD: −10.92 μm; 95% CI: −30.00 to 8.16 μm; CoE: very low) and days 15–42 (MD: −2.76 μm; 95% CI: −5.75 to 0.24 μm; CoE: low). By contrast, low-flow phacoemulsification showed less increase in CMT at postoperative days 15–42 (MD, −4.58 μm; 95% CI: −6.3 to −2.86 μm; CoE: low).

Conclusions

We found similar anatomical outcomes, except in CMT, for both high-flow and low-flow phacoemulsification cataract surgery. Future head-to-head RCTs on visual outcomes should confirm our findings.

Systematic review registration

PROSPERO, identifier: CRD42022297036.

Defining the surgical footprint in cataract surgery: patient-related outcomes dependent on the experience of the surgeon

PURPOSE

To investigate which patient-related outcomes are dependent on the experience of the cataract surgeon.

METHODS

The study was designed as a prospective observational study. Novice (<150 surgeries performed) and experienced (>1000 surgeries performed) cataract surgeons from the Department of Ophthalmology, Rigshospitalet - Glostrup and Nordsjaellands Hospital - Hillerød were included in the study. Patients operated by the included surgeons were examined preoperatively, 1 day, 3 days, and 3 weeks after standard, noncomplicated cataract surgery. Primary outcomes were change in central corneal thickness and endothelial cell loss. Secondary outcomes were best-corrected visual acuity, intraocular pressure, aqueous flare, central macular thickness, and surgical complications.

RESULTS

Surgery performed by novice surgeons resulted in significantly lower visual acuity (mean -3.6 letters (Early Treatment Diabetic Retinopathy Study (ETDRS)); 95% CI: -7.3; -0.4, p = 0.03) and greater corneal thickness (mean 26.7 µm; 95% CI: 6.8; 46.6, p = 0.01) on the first day postoperative than surgery performed by experienced surgeons.

CONCLUSION

The experience of the cataract surgeon affected visual acuity and central corneal thickness in the immediate postoperative period. In the future, these patient-related outcomes may be used to assess the technical proficiency of surgical trainees and investigate the effect of different training programs.

Optical coherence tomography angiography evaluation of the effects of phacoemulsification cataract surgery on macular hemodynamics in Chinese normal eyes

PURPOSE

To quantitatively evaluate the possible effects of phacoemulsification cataract surgery on macular hemodynamics using optical coherence tomography angiography (OCTA).

METHODS

This was a prospective observational study. Superficial and deep macular vascular densities, as well as parameters of foveal avascular zone (FAZ), were measured preoperatively (baseline) and at 1 day, 1 week, and 4 weeks postoperatively in normal eyes (≥ 22 mm and ≤ 24 mm) of patients scheduled for phacoemulsification cataract surgery with intraocular lens implantation. The correlations between the rate of change of pre- and postoperative vascular densities and surgical parameters were analyzed.

RESULTS

A total of 107 eyes of 107 patients were included in this study. Compared to the baseline measurements, no statistically significant variation was found in macular vascular densities at 1 day after the surgery (P > 0.05). Both superficial and deep macular vascular densities were significantly increased postoperatively at weeks 1 and week 4 (P < 0.05; P < 0.05); however, no statistically significant differences were detected in any of the FAZ parameters between the baseline measurements and the entire follow-up period (P > 0.05 for all). Also, no statistically significant correlations were established between main surgical parameters and macular vascular densities changes.

CONCLUSIONS

In normal eyes, macular blood perfusion gradually increased after phacoemulsification cataract surgery and was stabilized in one week. The foveal avascular zone was stabilized before and after the surgery. The main parameters and intraoperative perfusion of phacoemulsification surgery may not be the key factors affecting macular hemodynamics.

Elevated intraocular pressure causes cellular and molecular retinal injuries, advocating a more moderate intraocular pressure setting during phacoemulsification surgery

PURPOSE

To evaluate the cellular and molecular retinal injuries induced by various intraocular pressure (IOP) settings in a mouse model of acute ocular hypertension (AOH), and to advise using a more moderate target IOP during phacoemulsification (phaco) surgery.

METHODS

A mouse model of AOH that mimics a transient IOP elevation during phacoemulsification cataract surgery was established. Six groups with various settings of target IOP were included. Retinal tissues were assessed with terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end-labeling (TUNEL) staining for neuron loss, immunofluorescence with Iba1 for microglia activation, and quantitative real-time polymerase chain reaction analysis with tight junction proteins (claudin-3 and claudin-5) or classic inflammation markers (IL-1β and eNOS) for impairment of the blood-retinal barrier (BRB) and inflammatory injury.

RESULTS

Compared with those in the 45-mmHg IOP group, significantly increased number of neurons loss and increased microglia activation were observed in 90-mmHg IOP group. In addition, the expression of claudin-3 and claudin-5 was significantly decreased, while the expression of IL1-β and eNOS was up-regulated, indicating impairment of the BRB and inflammatory injury in the retina. Furthermore, these findings of neuron loss, microglia activation, and inflammation in the 90-mmHg groups were exacerbated when an IOP-induced retinal injury was established 5 days earlier, while those in the 45-mmHg groups remained almost unchanged.

CONCLUSIONS

In conclusion, these results showed that a relatively commonly used high IOP setting (90 mmHg) could induce significantly more serious retinal injury. An IOP setting around 45 mmHg is relatively safe and might be recommended in phaco surgery, especially in patients with advanced glaucoma, previous acute angle closure crisis, or other diseases with fragile retina and optic nerve.

Effects of ultrasound energy on the porcine corneal endothelium - Establishment of a phacoemulsification damage model

PURPOSE

The purpose of this study was to establish a standardized in vitro phacoemulsification damage model for future investigations of the effects of phacoemulsification, surgical devices, protective ophthalmic viscoelastic devices (OVDs), irrigation solutions and other aspects related to cataract phacoemulsification surgery on the corneal endothelium using porcine eyes.

METHODS

Thirty-four porcine eyes were randomly assigned to three groups (phacoemulsification (n = 13), irrigation (n = 9), control (n = 12)). A total of 5 min of ultrasound energy with intermittent irrigation/aspiration was applied in the eyes of the phacoemulsification group. The eyes of the irrigation group received the identical treatment, but without the application of ultrasound energy. The control group was left untreated. All eyes were then prepared to split corneal buttons followed by 15 days of cultivation. Endothelial cell density (ECD) was assessed blinded on day 15.

RESULTS

Endothelial cell density declined significantly more until day 15 in the phacoemulsification group (2567 ± 317/267 cells/mm² (median ± 25%/75%-quartiles), -32.5 ± 7.0/6.4%) compared to the irrigation (3450 ± 350/383 cells/mm², -11.8 ± 5.3/2.6%; p < 0.001) and the control group (3650 ± 288/258 cells/mm², -10.2 ± 3.2/4.6%; p < 0.001).

CONCLUSION

The phacoemulsification damage model presented in this study is sensitive to phacoemulsification energy and may reliably be used to investigate various factors involved in phacoemulsification with regard to their influence on corneal endothelial cells. This method is able to replace animal experiments or in vitro cell culture experiments that often do not translate well to the in vivo situation in humans.

Perioperative Use of Rho-Kinase Inhibitors has Beneficial Effect on Corneal Endothelium after Phacoemulsification

PURPOSE:

Does perioperative use of Rho-Kinase (ROCK) inhibitors have beneficial effect on corneal endothelial cells after phacoemulsification? SETTING: This study was conducted at King Abdulaziz University Hospital in Riyadh.

DESIGN:

This was a prospective study assessing the effect of ROCK inhibitors on corneal endothelium after phacoemulsification.

METHODOLOGY:

Three patients have used ROCK inhibitor 1 day before and 1 week after phacoemulsification surgery, and specular microscopy and Pentacam were done preoperatively and 3 months postoperatively.

RESULTS:

Endothelial cell density decreased to 11.3%, 9.45%, and 4.09% in eyes with ROCK inhibitors and 23.9% in one eye without ROCK inhibitor.

CONCLUSION:

Perioperative ROCK inhibitor use has a possible protective effect on corneal endothelium.

Effect of high-vacuum setting on phacoemulsification efficiency

PURPOSE

To evaluate the effect of a high-vacuum setting versus a low-vacuum setting on the efficiency of phacoemulsification.

SETTING

Sunderland Eye Infirmary, Sunderland, United Kingdom.

DESIGN

Prospective clinical trial.

METHODS

Consecutive patients having cataract surgery in 2014 were recruited. Cataract surgery was performed by 2 experienced surgeons using a phacoemulsification machine with monitored forced infusion. The cataractous lens was split into 2 heminuclei using the stop-and-chop technique; in 1 heminucleus, phacoemulsification and aspiration used a high-vacuum setting (600 mm Hg; treatment group) and in the other heminucleus, a low-vacuum setting (350 mm Hg; control group). The high and low settings were alternated by case per the operating list to reduce surgeon bias. The main outcome measures were cumulative dissipated energy (CDE) and active heminucleus removal time.

RESULTS

One hundred sixty patients (160 eyes) were enrolled in the study, and 158 were included in the analysis. The CDE per heminucleus was significantly lower with the high-vacuum setting than with the low-vacuum setting (mean 2.81 percent-seconds; 95% confidence interval (CI), 2.44-3.21 versus 3.81 percent-seconds; 95% CI, 3.38-4.20; P < .001). The active heminucleus removal time was significantly shorter in the high-vacuum group than the low-vacuum group (mean 27.77 seconds; 95% CI, 25.26-30.19 versus 33.59 seconds; 95% CI, 31.07-35.92; P < .001). The observed differences were independent of the surgeon, patient age and sex, incision size, and nucleus density. No intraoperative complications were observed in either group.

CONCLUSION

A high-vacuum setting improved phacoemulsification efficiency using an active fluidics system and torsional phacoemulsification.

Impact of fluidic parameters during phacoemulsification on the anterior vitreous face behavior: Experimental study

Purpose

To evaluate the eff ect of different aspiration flow rates (AFR) and bottle heights (BH) on vitreous face (AVF) during phacoemulsifi cation.

Methods

Experimental study in 20 porcine eyes. Transzonular viscodissection was performed between the posterior capsule(PC) and AVF to dissect out the Berger's space. Triamcinolone acetonide was injected into this space to aid visualization with ultrasound B-Scan(USG). Realtime USG was performed during phacoemulsifi cation. Eyes were divided randomly into-Group I: Low parameters(AFR = 20 cc/min, BH = 90 cm, vacuum = 400 mmHg),and Group II: High parameters (AFR = 40 cc/min, BH = 110 cm, vacuum=650 mm Hg).

Results

15 eyes were analysed (8 in Group I; 7 in Group II). In all eyes, forward and backward movement of the PC was seen when going from foot position 0 to 1, or on occlusion break. Amplitude of these movements was much greater in Group II compared to Group I. There was no PC rupture in either group. In 2 of the 7 eyes in Group II, USG showed a sudden, spontaneous dispersion appearance of sono-opaque echoes in the vitreous cavity alongwith disappearance of the well-defi ned, crescentic stained space despite an intact PC. This suggests rupture of the AVF, leading to dispersion of the triamcinolone into the entire vitreous cavity. No AVF rupture was seen in Group I.

Conclusion

We report a rarely described entity of AVF rupture with intact PC. The use of high AFR and BH may have clinically invisible detrimental consequences to the anterior vitreous face.

Phacoemulsification of the rock-hard dense nuclear cataract: Options and recommendations

We describe the essential steps in the successful phacoemulsification of the rock-hard, dense cataract. Appropriate and directed preoperative history, physical examination, and diagnostics allow the surgeon to select the best incision, anesthesia, and intended surgical technique for a given dense nuclear challenge. Hard nucleus-specific approaches for hydrodissection, pupil management, and zonular protection then allow the surgeon to approach the rock-hard nucleus with maximum safety. Dense nuclear dismantling options are then discussed in detail along with fluidic and power modulation considerations. Various specific phacoemusification machine settings for rock-hard cataracts from the authors representing several different phaco systems are then presented. The combination of these steps and considerations allow a more successful dense cataract removal and potential restoration of vision for patients. This paper represents the collective experience and advice of the Challenging and Complex Cataract Surgery Subcommittee.

Publication rates from the All India Ophthalmic Conference 2010 compared to 2000: Are we improving?

PURPOSE

To determine the publication rates of free papers and posters presented at the All India Ophthalmic Conference (AIOC) 2010 in peer-reviewed journals up to December 2015 and compare this with publication rates from AIOC2000 published previously.

METHODS

A thorough literature search was conducted using PubMed, Google Scholar, and the general Google search engine by two independent investigators. The title of the paper, keywords and author names were used to "match" the AIOC free-paper with the published paper. In addition, the "purpose," "methods," and "outcome measures" between the two were studied to determine the "match."

RESULTS

A total of 58 out of 394 free-papers (14.7%) from AIOC2010 were published till December 2015 compared to 16.5% from AIOC2000. Out of these, 52 (90%) were published in PubMed indexed journals. Maximum publications were seen in pediatric ophthalmology (50%) followed by glaucoma (24.4%) and cornea (23.8%). Fifteen out of 272 posters (5.5%) were published; orbit/oculoplastics had the highest poster publications (13%). Excluding papers in nonindexed journals and those by authors with international affiliations, the publication rate was approximately 12%.

CONCLUSION

The publication rate of free papers from AIOC2010 has marginally reduced compared to AIOC2000. Various causes for this such as lack of adequate training, motivation, and lack of incentives for research in the Indian scenario have been explored, and measures to improve this paradigm have been discussed. It will be prudent to repeat this exercise every decade to compare publication rates between periodic AIOC, stimulate young minds for quality research and educate policy makers toward the need for developing dedicated research departments across the country.

Effect of fluidics on corneal endothelial cell density, central corneal thickness, and central macular thickness after phacoemulsification with torsional ultrasound

Aim:

To study the relative effects of high and low fluidic parameters on endothelial cell density (ECD), central corneal thickness (CCT), and central macular thickness (CMT) after phacoemulsification with torsional ultrasound.

Settings and Design:

Prospective, randomized clinical trial based on a tertiary eye hospital.

Subjects and Methods:

The study included 65 patients in each group. Patients were randomized to either the high or the low flow group using a computerized random number table. The study was patient and examiner masked. All patients underwent phacoemulsification with torsional ultrasound. Visual acuity, ECD, CCT, and CMT were measured for all patients preoperatively at 2 weeks and 6 weeks postoperatively.

Statistical Analysis Used:

The Shapiro–Wilks test was used to assess the normality of the data. Mann–Whitney U-test with the P value set at 0.05 was used to compare the two groups.

Results:

Cumulative dissipated energy was significantly higher in the low flow group (16.44 ± 9.07 vs. 11.74 ± 6.68; P = 0.002). No statistically significant difference was noted between the two groups in the ECD, CCT, CMT, or corrected distance visual acuity at the end of 6 weeks.

Conclusions:

No significant difference was noted in the postoperative outcome between high and low flow groups. Parameters can be modified to suit the surgeon's preference, as both high and low flow parameters were found to have comparable postoperative outcomes.

Comparison of Phacoemulsification Cataract Surgery with Low versus Standard Fluidic Settings and the Impact on Postoperative Parameters

Purpose

To compare complications after cataract surgery using 2 different phacoemulsification fluidic settings.

Methods

One cataract surgeon (M.K.) performed phacoemulsification cataract surgery in one eye of 43 patients in this randomized prospective clinical study conducted at St. Erik Eye Hospital, Stockholm, Sweden. The patients were randomized to phacoemulsification with low fluidic settings in one group and standard fluidic settings in the other group. Corrected distance visual acuity (CDVA), central corneal thickness (CCT), endothelial cell density (ECD), anterior chamber flare, intraocular pressure (IOP), and macular thickness were measured preoperatively and postoperatively, with a final evaluation at 3 months. Surgical time, ultrasound energy, and amount of balanced saline solution used intraoperatively were recorded.

Results

Twenty-one patients were included in the group with standard settings and 22 patients were in the group with low settings. There were no significant differences between the groups in CDVA, CCT, flare, IOP, macular thickness, or ECD at 1 day, 3 weeks, or 3 months postoperatively. The surgical time was significantly (p = 0.009) longer and cumulative dissipated energy was significantly (p<0.001) higher in the group with low fluidic settings.

Conclusions

Although the surgical time and ECD were significantly higher in the group with low fluidic settings, there were no differences in the CCT, ECD, macular thickness, or inflammation postoperatively between the low and standard fluidic settings during phacoemulsification.

Real-time intraocular pressure measurement during phacoemulsification in dogs ex vivo

This study was performed to evaluate changes in intraocular pressure (IOP) during standard coaxial phacoemulsification using 4 different bottle heights (BHs) and 2 different incision sizes. Coaxial phacoemulsification was performed with a venturi-based machine in 8 enucleated canine eyes through 3.0 and 3.2 mm clear corneal incisions (CCIs). A pressure transducer inserted in the peripheral cornea monitored the IOP in real-time. The surgery was subdivided into 4 stages: sculpt-segment removal, irrigation/aspiration, capsular polishing and viscoelastic removal. The mean IOP and the difference between the maximum and minimum IOPs were calculated at each stage and compared. The ultrasound time and volume of irrigation fluid used were recorded. The mean IOP increased with an elevation in the BH. The mean IOP in the irrigation/aspiration stage was significantly higher than that in the sculpt-segment removal stage at the same BH. The difference between the maximum and minimum IOP at each stage was greater in the 3.2 mm than the 3.0 mm CCIs, although the mean IOP was lower with the 3.2 mm than the 3.0 mm CCIs. The ultrasound time and irrigation fluid volume were greater with the 3.2 mm than the 3.0 mm CCIs. Therefore, fluidic parameters during each stage could be reassessed and adjusted to reduce complications arising from an elevated IOP. Phacoemulsification with 3.0 mm CCIs at a lower BH might lead to less stress on the eye from IOP fluctuations, ultrasound energy and irrigation fluid.

Real-time dynamic intraocular pressure fluctuations during microcoaxial phacoemulsification using different aspiration flow rates and their impact on early postoperative outcomes: a randomized clinical trial

PURPOSE

To compare the impact of varying fluidic parameters on intraoperative intraocular pressure (IOP) fluctuations and postoperative outcomes.

METHODS

Prospective randomized study of 80 eyes undergoing cataract surgery that were randomly assigned to low (aspiration flow rate: 20 cc/min; bottle height: 90 cm; vacuum: 400 mm Hg) and high (aspiration flow rate: 40 cc/min; bottle height: 110 cm; vacuum: 400 mm Hg) fluidic parameter groups. Real-time dynamic intraoperative IOP was measured during nuclear fragment removal. Mean maximum and minimum IOP and percentage reduction in IOP from maximum were compared between groups. Postoperatively, the rate of change in central corneal thickness and anterior chamber inflammation at days 1 and 7, endothelial cell density at 3 months, and corneal clarity on day 1 were compared.

RESULTS

Minimum IOP in the low and high parameters groups was 35 ± 4.0 and 34.5 ± 6.8 mm Hg, respectively. Maximum IOP in the low and high parameters groups was 69 ± 3.0 and 85 ± 1.2 mm Hg, respectively (P < .002). Mean percent reduction from maximum was 59% in the high parameters group compared to 41% in the low parameters group, with the difference being statistically significant (P < .002). Rate of change in central corneal thickness was greater in the high parameters group at postoperative days 1 and 7 (P < .001). Anterior chamber inflammation and corneal clarity on the first postoperative day were significantly better in the low parameters group.

CONCLUSIONS

Higher aspiration flow rate and bottle heights are associated with high intraoperative IOPs of up to 85 mm Hg. Prolonged elevated IOP during cataract surgery was found to have more anterior segment inflammation and more edematous corneas.

Fluid dynamics and intraocular pressure using venturi phacoemulsification machine in dogs ex vivo

OBJECTIVE

To optimize fluid dynamics through measuring intraocular pressure (IOP) in a venturi phacoemulsification machine in dogs.

PROCEDURES

In step I, flow and IOP of the test chamber were measured using a pressure transducer with the bottle height (BH) set at 50, 70, 100, and 120 cm and the vacuum from 30 to 450 mmHg. A 19-gauge phaco and a 0.3-mm irrigation/aspiration (I/A) handpiece were used. In step II, flow and IOP were measured in an enucleated canine eye with a 3.0- and a 3.2-mm clear corneal incision (CCI), respectively. IOP was measured using the pressure transducer at a 30-mmHg vacuum to allow corneal deformation, to define the fluidic parameters for preventing surge.

RESULTS

Flow was directly proportional to the BH and vacuum, whereas IOP was directly proportional to the BH and inversely to the vacuum. Flow with an I/A handpiece was significantly less than with a phaco handpiece, explaining why IOP with an I/A handpiece was significantly higher than with a phaco handpiece. With the I/A handpiece, vacuum parameters less than 450 mmHg did not result in corneal deformation. IOP with a 3.2-mm CCI was significantly lower than with a 3.0-mm CCI, with the 3.2-mm flow being greater than the 3.0-mm flow.

CONCLUSIONS

BH during the I/A stage could be reduced to avoid unnecessary stress on the canine eye when using a venturi system. Although phacoemulsification with a 3.2-mm CCI could induce lower IOP, a 3.0-mm CCI might lessen the irrigation flow stress on the eye.

Impact of low versus high fluidic settings on the efficacy and safety of phacoemulsification

PURPOSE

  To compare intraoperative efficiency and postoperative outcomes of cataract surgery with low and high fluidic settings.

METHODS

  In this prospective, randomized, single-blinded study, 114 eyes of 57 patients were operated with low fluidic settings for one eye (group I) and high fluidic settings for the other eye (group II). Efficiency was judged as metred surgery time, effective phacoemulsification time (EPT) and the amount of balanced salt solution used. Visual outcome and endothelial cell count were determined 1 week and 18 months postoperatively.

RESULTS

  The overall effective phacoemulsification energy was statistically significantly lower (p = 0.003) in group II than in group I. Conquest of the nuclei was achieved with about two-thirds of the energy needed in group I, with 6.59 ± 4.79 effective ultrasound energy compared with 3.99 ± 3.18 (p = 0.001). Overall, about 12% more solution was used in group II than in group I. Median visual acuity was 1.0 for both groups 18 months after surgery. The mean endothelial cell loss was 5.0% in eyes in group I compared with 6.3% in eyes in group II (p > 0.5).

CONCLUSION

  Switching from low fluidic settings with a conventional coaxial 20G phacoemulsification tip to higher fluidic settings with a microcoaxial phaco tip statistically significantly decreases EPT. As only marginally more solution was used with the higher aspiration flow, occlusion must be accomplished more often with high than with low fluidics. Aspiration of the quadrants was therefore more efficient with high fluidic settings. The enhanced pump speed did not result in more tissue damage.

Anatomy and physiology of the cornea

The importance of the cornea to the ocular structure and visual system is often overlooked because of the cornea's unassuming transparent nature. The cornea lacks the neurobiological sophistication of the retina and the dynamic movement of the lens; yet, without its clarity, the eye would not be able to perform its necessary functions. The complexity of structure and function necessary to maintain such elegant simplicity is the wonder that draws us to one of the most important components of our visual system.