P-621 Different gonadotrophins adopted for controlled ovarian stimulation do not affect metaphase-II oocyte competence. A matched case-control study on 351 patients and 2258 oocytes

Study question

Do different gonadotrophins for controlled-ovarian-stimulation (COS) affect metaphase-II (MII) oocyte competence?

Summary answer

Euploid blastocyst rate (EBR) per cohort of MII-oocytes, live-birth-rate (LBR) per first vitrified-warmed euploid single-embryo-transfer (SET) and cumulative-LBR are independent from the gonadotrophins used.

What is known already

Controlled-ovarian-stimulation (COS) is a cornerstone of IVF. Its purpose is maximizing ovarian reserve exploitation and obtaining ≥1 euploid blastocyst to transfer. Indeed, ovarian reserve decreases and blastocyst aneuploidy rates increase with increasing maternal age, making this task quite complicated in advanced maternal age. Old-fashioned studies suggested an association between COS and embryonic aneuploidy rates. Conversely, recent studies excluded an impact of COS dosage, duration, ovarian response, and ovulation trigger, on blastocyst aneuploidy rate. An aspect, though, needs more clarity: do different gonadotropins impact oocyte competence after COS, comprehensively defined as EBR per cohort of MII-oocytes?

Study design, size, duration

Out of 3169 PGT cycles with ³1 MII oocyte conducted between 2014-2018, we excluded (i)PGT-M/-SR, (ii)women<35yr, (iii)severe-male-factor, (iv)DuoStim or long-active FSH, (v)culture with sequential-media, and (v)multiple cycles. Among the 784 cycles left, a propensity-score-matching (PSM) based on the number of inseminated MII-oocytes was adopted to match patients using recFSH [without (N = 57; 337 MII-oocytes)/with recLH (N = 55; 374 MII-oocytes)] and Human-Menopausal-Gonadotrophin (HMG; N = 127; 835 MII-oocytes). The patients using recFSH+HMG were all included (N = 112; 712 MII-oocytes).

Participants/materials, setting, methods

Only GnRH-antagonist COS, ICSI with fresh MII-oocytes, single culture in continuous-media, trophectoderm biopsy without assisted-hatching, comprehensive-chromosome-testing to assess full-chromosome non-mosaic aneuploidies and vitrified-warmed euploid SET were conducted. Oocyte competence was comprehensively defined as EBR per cohort of MII-oocytes with all intermediate outcomes (fertilization, blastulation and euploidy). LBR per first vitrified-warmed euploid SET and cumulative-LBR per retrieval were also assessed. Generalized-linear-models and multivariate regressions were adopted to adjust the results for confounders. All cycles were concluded.

Main results and the role of chance

Patients using recFSH+recLH and recFSH+HMG (40.7 yr) were older than patients using recFSH-only or HMG-only (40 yr; ANOVA<0.01). No other difference was reported in the 4 patient populations. The overall gonadotrophins dosage (2615±977, 3601±1889, 3818±946 and 2892±911 IU in the recFSH-only, recFSH+recLH, recFSH+HMG and HMG-only groups, respectively) and duration of COS (9.7±1.9, 9.4±1.5, 9.9±1.8 and 10.2±1.8 days) were different (Kruskal-Wallis tests=0.02). The number of cumulus-oocyte-complexes (9.2±6.5) and MII-oocytes collected (6.4±4.4) were instead well-matched across the groups. The EBR per cohort of inseminated MII-oocytes was different in the four groups (20.7±27.1%, 9.6±12.9%, 12.4±18.5% and 16.9±21.8%, respectively), but, when adjusted for maternal age in a generalized-linear-model, the gonadotrophin used for COS did not show any significant association with this outcome (partial-eta2=0.02, p = 0.1, power=0.6). All intermediate embryological outcomes were also similar. The LBR per first vitrified-warmed euploid SET was comparable in the four groups [N = 14/33 (42%), N = 9/22 (41%), N = 26/62 (45%), N = 24/55 (44%), respectively], as confirmed by the logistic regression adjusted for blastocyst quality (multivariate-OR: 0.97, 95%CI 0.73-1.31, adjusted-p=0.9). Lastly, the cumulative-LBRs per retrieval were equivalent [N = 17/57 (30%), N = 14/55 (26%), N = 34/127 (27%), and N = 33/112 (30%), respectively], as confirmed by the logistic regression adjusted for maternal age (multivariate-OR: 1.01, 95%CI 0.8-1.3, adjusted-p=0.9).

Limitations, reasons for caution

The gonadotrophins were chosen based on patient compliance to their administration route and gynecologist judgement, and only qualitative outcomes were assessed. Therefore, randomized-controlled-trials and cost-effectiveness analysis investigating the efficiency in oocyte recruitment and cumulative-LBR per intention-to-treat are needed.

Wider implications of the findings

Different gonadotrophins might not affect MII-oocyte competence. This information is key since, in view of the optimization of follicle recruitment through personalized-COS, it allows more flexibility in the choice of the most suitable protocol. Therefore, gynecologists might ponder also features like patient reproductive history and compliance to different administration routes.

Trial registration number

none

O-072 Can preimplantation genetic testing for monogenic conditions represent an indication for DuoStim? A multicenter case series

Study question

Is double stimulation in the same ovarian cycle (DuoStim) a valuable strategy to improve the chance of success in couples carrier of monogenic conditions?

Summary answer

DuoStim is advantageous in patients indicated for preimplantation genetic testing for monogenic diseases and aneuploidy testing (PGT-M/-A) and obtaining ≤5 blastocysts after the I-stimulation.

What is known already

PGT-M is a well-established strategy to identify unaffected blastocysts in a cohort of embryos produced from couples carrier of single gene disorders. When PGT-M is conducted in poor prognosis and/or advanced maternal age (POR/AMA) patients, also aneuploidy-testing among unaffected blastocysts is suggested on a single biopsy. The Poseidon group stated that retrieving an adequate number of oocytes to produce ≥1 euploid blastocyst should be considered the main goal of controlled-ovarian-stimulation (COS). This task is even more complex when PGT-M is required in POR/AMA patients. Therefore, lately we started suggesting DuoStim to these couples to maximize their chance of success.

Study design, size, duration

Multicenter case series (2016-2021). Comprehensive description of IVF outcomes derived from DuoStim application in POR/AMA patients undergoing PGT-M. Aneuploidy-testing was also conducted on unaffected blastocysts. All results were compared between the two stimulations in the same ovarian cycle, and we reported the contribution of II-stimulations to higher chances of success.

Participants/materials, setting, methods

GnRH-antagonist COS was performed with recombinant-gonadotrophins and agonist-trigger. Based on the expected risk each embryo would be affected-aneuploid, DuoStim was suggested to all patients obtaining ≤5 blastocysts (day5-7 from I-retrieval). 61 patients accepted and underwent II-stimulations with the same protocol. Only ICSI, trophectoderm-biopsy, qPCR, and vitrified-warmed unaffected-euploid single-blastocyst-transfer(s) were conducted.

Main results and the role of chance

90 patients (36.7±3.7yr) indicated to PGT-M/-A and obtaining ≤5 blastocysts after I-stimulations were suggested starting a II-stimulation in the same ovarian cycle. Among them, 61 accepted (67%). 7.2±4.4 and 7.4±4.2 cumulus-oocyte-complexes were retrieved after I- and II-stimulations, respectively (p = 0.7). 5.1±3.0 and 5.8±3.4 were metaphase-II oocytes (p = 0.2), resulting in 75±21% and 77±25% maturation-rates (p = 0.6). 3.6±2.1 and 4.6±2.9 2PN-zygotes were obtained (p = 0.04), resulting in 75±27% and 81±20% fertilization-rates (p = 0.19). 1.6±1.3 and 2.2±1.8 blastocysts were obtained (p = 0.04), resulting in 43±32% and 46±32% blastulation-rates (p = 0.6). Lastly, 0.5±0.7 and 0.7±1.0 blastocysts were diagnosed unaffected-euploid (p = 0.3), resulting in 35±40% and 30±36% transferable blastocyst rates per biopsied embryo, respectively (p = 0.53), and identical 10±16% transferable blastocyst rates per metaphase-II oocyte in both groups (p = 0.9). 23 (38%) and 24 (39%) patients obtained ≥1 transferable blastocyst after the I- and II-simulation, respectively. Overall, 36 (59%) patients obtained ≥1 transferable blastocyst thanks to DuoStim. To date, 57 (93%) cycles were concluded, and the cumulative live birth rate (CLBR) was 37% (N = 21/57). The patients with a LB have 1.7 surplus transferable blastocysts, and 3 patients already delivered 2 singleton healthy-LBs. The CLBR among patients undergoing the conventional strategy was 21%, no surplus transferable blastocyst is available, and no patient delivered >1 LB.

Limitations, reasons for caution

Observational case series based on real-life data. Of note, the adoption of DuoStim (or any other oocyte/embryo accumulation strategy) in PGT-M/-A is valuable also to amortize the costs of PGT-M set-up and genetic testing through a larger number of blastocysts. In this context, cost-effectiveness analyses in different settings are desirable.

Wider implications of the findings

DuoStim is a fully-personalized strategy advisable any time lower chance of success and higher treatment costs could be balanced by a larger number of blastocysts produced in a short time-frame. Adopting GnRH-antagonist protocols in these patients allows to suggest DuoStim even in progress, based on the embryological outcomes after I-stimulations.

Trial registration number

Not applicable

P–606 A second stimulation in the same ovarian cycle rescues advanced-maternal-age patients obtaining ≤ 3 blastocysts after the conventional approach by preventing treatment-discontinuation

Study question

Is double stimulation in the same ovarian cycle (DuoStim) a valuable strategy to rescue advanced-maternal-age patients obtaining ≤ 3 blastocysts for chromosomal-testing after conventional stimulation?

Summary answer

DuoStim is effective to prevent treatment discontinuation thereby increasing the 1-year cumulative-live-birth-rate among advanced-maternal-age patients obtaining 0–3 blastocysts after a first conventional stimulation.

What is known already

Folliculogenesis is characterized by continuous waves of follicular growth. DuoStim approach exploits these dynamics to conduct two stimulations in a single ovarian cycle and improve the prognosis of advanced-maternal-age and/or reduced-ovarian-reserve women. Independent groups worldwide successfully adopted DuoStim with various regimens reporting similar oocyte/embryo competence after both stimulations. Recently, we have demonstrated the fruitful adoption of DuoStim in patients fulfilling the Bologna criteria, especially because of the prevention of treatment discontinuation. Here we aimed at investigating whether DuoStim can be adopted to rescue poor prognosis patients obtaining 0–3 blastocysts after the conventional approach.

Study design, size, duration

Proof-of-concept matched case-control study. All patients obtaining 0–3 blastocysts after conventional-stimulation between 2015–2018 were proposed DuoStim. The 143 couples who accepted were matched for maternal age, sperm factor, cumulus-oocyte-complexes and blastocysts obtained after the first stimulation to 143 couples who did not. The primary outcome was the 1-year cumulative-live-birth-rate. If not delivering, the control group had 1 year to undergo a second attempt with conventional-stimulation. All treatments were concluded (live-birth achieved or no euploid left).

Participants/materials, setting, methods

Only GnRH-antagonist with recombinant-gonadotrophins and agonist trigger stimulation protocols were adopted. All cycles entailed ICSI with ejaculated sperm, blastocyst culture, trophectoderm biopsy, comprehensive-chromosome-testing and vitrified-warmed euploid single-embryo-transfer(s). Cumulative-live-birth-rate was calculated per patient considering both stimulations in the same ovarian cycle (DuoStim group) or up to two stimulations in 1 year (control group). Treatment discontinuation rate in the control group was calculated as patients who did not return for a second stimulation among non-pregnant ones.

Main results and the role of chance

Among the 286 couples included (41.0±2.9yr;4.9±3.1 cumulus-oocytes-complexes and 0.8±0.9 blastocysts), 126 (63 per group), 98 (49 per group), 52 (26 per group) and 10 (5 per group) obtained 0,1,2 and 3 blastocysts after the first stimulation, respectively. The cumulative-live-birth-rate was 9% in the control group after the first attempt (N = 13/143). Among the 130 non-pregnant patients, only 12 returned within 1-year (165±95days later;discontinuation rate=118/130,91%), and 3 delivered. Thus, the cumulative-live-birth-rate from two stimulations in 1-year was 11% (N = 16/143). In the DuoStim group, the cumulative-live-birth-rate was 24% (N = 35/143; Fisher’s-exact-test< 0.01,power=80%). The odds-ratio of delivering in the DuoStim versus the control group adjusted for all matching criteria was 3.3,95%CI:1.6–7.0,p<0.01. This difference (0%,22%,15% and 20% in the control versus 10%,31%,46% and 40% in the DuoStim group among patients obtaining 0,1,2 and 3 blastocysts at the first stimulation, respectively) is mainly due to treatment discontinuation in the control group (98%,65%,77% and 80% among patients obtaining 0,1,2 and 3 blastocysts at the first stimulation, respectively) and the further increased maternal age at the time of second retrieval (∼6 months). Notably, 2 patients delivered 2 live-births after DuoStim (none in the control) and 14 patients with a live-birth have euploid blastocysts left (2 in the control).

Limitations, reasons for caution

Randomized-controlled-trials and cost-effectiveness analyses are desirable to confirm these data. Moreover, 75% of the patients included were >39yr and 44% obtained no blastocyst after the first stimulation. Therefore future studies among younger women and/or more women obtaining ≥1 blastocyst are advisable to set reasonable cut-off values to apply this strategy.

Wider implications of the findings: A second stimulation in the same ovarian cycle might be envisioned as a rescue strategy for poor IVF outcomes after a first stimulation, so to prevent treatment discontinuation and increase the cumulative-live-birth-rate. This is feasible since 6–7 days span the first and the second stimulation in the DuoStim protocol.

Trial registration number

none

P–519 Investigation of embryo chromosomal constitution and live birth rate after vitrified-warmed euploid single blastocyst transfer across ranges of maternal body-mass-index

Study question

Does maternal body-mass-index (BMI) associate with blastocysts’ chromosomal constitution and clinical outcomes in infertile patients undergoing preimplantation genetic testing for aneuploidies (PGT-A)?

Summary answer

A higher euploidy rate per biopsied blastocyst was reported among underweight women. Overweight women were instead subject to higher miscarriage (MR) and lower live-birth-rates (LBR).

What is known already

Different studies in the literature revealed an association between BMI and infertility, suggesting a J-shaped relationship: both underweight and overweight women can suffer from infertility issues. Even if IVF might increase the success rate in both these categories of patients, it seems insufficient per se to overcome the complex and multifactorial fertility impairment derived from unbalanced nutritional intakes. Miscarriage, in particular, is common in both underweight and overweight women. However, most of the literature is based on chromosomally-untested embryos. Study design, size, duration: Retrospective observational study. Only the first IVF cycle with ≥1 biopsied blastocyst from each woman was included. The primary outcome was the association between maternal BMI (underweight, BMI<18.5, n = 160; normal-weight, BMI=18–25, N = 1392; overweight, BMI>25, N = 259) and the mean euploidy rate per cohort of biopsied blastocysts (m-ER). The secondary outcomes were the association between maternal BMI with clinical (mainly MR and LBR), gestational and perinatal outcomes after first vitrified-warmed single euploid blastocyst transfers.

Participants/materials, setting, methods

We included 1811 women undergoing PGT-A at a private IVF center between April–2013 and March–2020. The secondary outcomes were investigated on 1125 first vitrified-warmed single euploid blastocyst transfers from all patients obtaining ≥1 transferable blastocyst. Only ICSI with ejaculated sperm and continuous culture in standard incubators were performed. Logistic regressions were conducted to identify putative confounders and adjust the results accordingly.

Main results and the role of chance

Except for a lower maternal age among underweight women (38.3±3.1 versus 38.9±3.4 yr, p < 0.01) and higher among overweight ones (39.3±3.6 yr, p = 0.04), no difference was reported with respect to normal-weight women in terms of duration of infertility, hormonal levels, main cause of infertility, sperm quality, and reproductive history. The mean number of biopsied blastocysts was ∼3 in all groups. The m-ER shows a decreasing trend as the maternal BMI increases between 17 and 22–23, to then plateau. In fact, a significant difference was reported between underweight (50.8%±36.4%) and normal-weight women (41.4%±37.5%, p < 0.01). A linear regression adjusted for maternal age confirmed this moderate association between increasing BMI and m-ER (unstandardized-coefficient-B –0.6%, 95%CI:–1.1% to –0.1%, p = 0.02).

Morphological quality and day of full-blastulation among transferred euploid blastocysts was similar in the three groups. Overweight women showed higher MR per pregnancy (N = 20/75, 26.7%, 95%CI:17.4%–38.3% versus N = 67/461, 14.5%, 95%CI:11.5%–18.2%; OR 2.0, 95%CI:1.1–3.6, p = 0.01) and lower LBR per transfer (N = 55/154, 35.7%, 95%CI:28.3%–43.8% versus N = 388/859, 45.2%, 95%CI:41.8%–48.6%; OR adjusted for euploid blastocysts’ features 0.67, 95%CI:0.46–0.96, p = 0.03). Clinical outcomes were instead similar among underweight and normal-weight women. All gestational and perinatal outcomes were comparable in the tree groups.

Limitations, reasons for caution

Our study is limited by its retrospective nature, and the fact that maternal BMI was measured only before oocyte retrieval and not before embryo transfer. Moreover, the reduced sample size did not allow for further relevant sub-analyses among solely obese women.

Wider implications of the findings: When possible nutritional/lifestyle modifications should be encouraged to adjust maternal BMI before IVF. Overweight patients should be especially informed of their higher risk for miscarriage. Yet, BMI is just a gross marker, future studies based on body fat localization and percentage (e.g. by bioelectrical impedance analyses) are desirable.

Trial registration number

None

Impact of the COVID-19 pandemic in the MR availability for iron overloaded patients

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): The E-MIOT project receives “no-profit support” from industrial sponsorships (Chiesi Farmaceutici S.p.A. and Bayer).

Background

The T2* magnetic resonance imaging (MRI) technique for the noninvasive quantification of iron overload has significantly improved the survival of patients with hemoglobinopathies by tailoring the chelation therapy. In Italy, the E-MIOT (Extension-Myocardial Iron Overload in Thalassemia) Network, a collaborative project among MRI and hematological centers, has assured high-quality quantification of iron in vital organs such as heart, liver, and pancreas. The COVID-19 pandemic has disrupted healthcare services around the world, also leading to postpone  or delete deferable diagnostic evaluations.

Aim

  We evaluated the impact of the COVID-19 pandemic on MRI services for iron overload quantification in Italy.

Methods

The activity of the MRI centers of the E-MIOT Network in the year 2020 was compared to the activity in the same months of 2019. A specific survey was filled out by the MRI operators to evaluate if the availability of MRI slots for patients with hemoglobinothies was reduced and the reasons.

Results

In comparison with the year 2019, in 2020 there was a significant reduction in the number of T2* MRIs performed (350 vs 656; P < 0.0001). The comparison month by month between the two years highlighted a marked decline (86.9%) in the four-month period March-June 2020, a reduction in the gap between the two years in the three-month period July-September, and a new decline (41.4%) in the three-month period October-December (Figure 1). No patient with hemoglobinopathy could undergo an MRI scan during the Italian lockdown (9 March-10 May 2020).

Figure 2 shows the percentage of  decline (year 2020 vs 2019) in the number of T2*MRI scans for each MRI center. If no decline or an increase were present, the vertical axis was set at 0. All centers experienced a significant drop in the number of the T2* MRIs in the four-month period March-June (from 75 to 100%). In the three-month period July-September only the centers of Pisa and Taranto dropped the number of T2* MRIs due to the rescheduling of the other MRI appointments deleted during the lockdown. In the three-month period October-December a reduction of the T2* MRI scans was experienced by all centers, except for Campobasso. In the centers of Ferrara and Lamezia Terme the reduction was the consequence of the general reduction in the number of the total MRIs scheduled per day for the  sanitation procedures. In the other centers, the availability for T2* MRI scans was unchanged in comparison to 2019, but the patients refused the MRI follow up for fear of getting sick of COVID.

Conclusion

The COVID-19 pandemic is having a strong negative impact on the quantification of iron overload by MRI, which may seriously worsen the prognosis of patients with hemoglobinopathies. Strategies to ensure proved lifesaving MRI exam and to reassure patients about the health safety of the hospitals are recommended.

The ovarian follicular pool and reproductive outcome in women

Both quantitative and qualitative aspects of the ovarian reserve are inversely related to age, hence the relationship existing between low quantity and low quality may be only indirect and depending on their strong relationship with the third variable, namely women's age. However the possibility exists that they may also be directly related. The objective of this study was to investigate the relationship between ovarian reserve and female reproductive outcome. Eight published studies reporting histological data on the human ovaries have been carefully reviewed. Only studies where the reproductive history of women was reported have been included for the analysis. The non-growing follicle count was plotted versus age and the best fit line through the data was calculated. All patients were assigned as to be above or below the calculated median hence differentiating women with high or low ovarian reserve for their age. A similar number of pregnancies ended in miscarriage in women with low and high ovarian reserve. The number of deliveries per woman in both the groups was not statistically different. The results of the study do not support the hypothesis that quality and quantity of the follicular pool are directly related.

Arterial narrowing as a predictive factor in glaucoma

PURPOSE

To evaluate whether retinal arteriolar widths change in normal patients and in different glaucoma types. We measured the arteriolar width at the merge in the optic nerve (MD), at the edge of the optic nerve (ED) and at the peripapillary area (1 disc diameter distance) (disc distance D). HRT software 1.11, Interactive Means program was used. One hundred forty three eyes of seventy-two patients divided in four subgroups normal, low-tension glaucoma (LTG), primary open angle glaucoma (POAG) and ocular hypertensive (OH). No statistically significant was found in each studied group. The normal patients showed no changes in the retinal arteriolar width compared with all the glaucoma groups.

Optic capture of the AcrySof intraocular lens in pediatric cataract surgery

PURPOSE

To assess the results of acrylic intraocular lens (IOL) optic capture in children with cataract.

SETTING

Department of Ophthalmology, Hospital de Clínicas José de San Martín, and Instituto de la Vision, School of Medicine, University of Buenos Aires, Argentina.

METHODS

Eight children had cataract surgery. After lens and cortex aspiration, an AcrySof (Alcon) IOL was implanted in the bag. A primary posterior capsulorhexis was performed. The optic edges were slipped through the posterior capsule leaflets. Clarity of the visual axis, preoperative and postoperative best corrected visual acuities (BCVAs), and refraction were evaluated.

RESULTS

The visual axis remained clear in all cases. No case required a secondary procedure. The mean preoperative BCVA was 0.06 +/- 0.06 (SD). Postoperatively, the mean BCVA was 0.88 +/- 0.11 and the mean spherical equivalent, +0.62 +/- 1.31. The mean follow-up was 28.9 +/- 5.3 months.

CONCLUSION

Results show that the optic of an acrylic IOL may be captured through a posterior capsulorhexis in pediatric cataract surgery, combining the advantages of optic capture with a smaller incision and a decreased inflammatory response.

Corneal ectasia after laser in situ keratomileusis

PURPOSE

To describe 7 patients who developed ectasia following laser in situ kerato-mileusis (LASIK).

SETTING

Instituto de la Visión, Buenos Aires, Argentina.

METHODS

In this retrospective study of 7 patients, visual acuity, refraction, pachymetry, and corneal topography were examined before and after the refractive procedure and the occurrence of ectasia.

RESULTS

Two of the 7 patients required penetrating keratoplasty. Ectasia developed within a mean of 1.02 years +/- 0.31 (SD). The clinical evolution of ectasia and the potential physiopathogenic causes of ectasia are described.

CONCLUSION

Ectasia should be considered a potential complication of LASIK that is closely related to corneal thickness, but another variable, the optical zone diameter, should also be considered.

Ciliary body tumor and cataract: local resection combined with phacoemulsification

A 57-year-old man developed a ciliary body mass, clinically diagnosed as malignant melanoma of the ciliary body, that produced a cataract in the right eye. Treatment was cataract surgery with sclerouvectomy performed simultaneously. Pathohistologic examination revealed an acquired adenoma of the nonpigmented ciliary epithelium. The clinicopathologic features and treatment of this tumor are discussed.

Customized ablation for asymmetrical corneal astigmatism

PURPOSE

To evaluate laser in situ keratomileusis (LASIK) cases in which a customized ablation assisted by corneal topography was performed.

SETTING

Instituto de la Visión, Buenos Aires, Argentina.

METHODS

The study group comprised 23 cases with asymmetrical corneas; 17 had myopia and 6, hyperopia. Visual acuity, spherical equivalent (SE), and cylinder vectorial change measurements, along with keratometry and corneal topography, were performed in all cases preoperatively and postoperatively.

RESULTS

In the myopic cases, the mean preoperative SE was -4.92 diopters (D) +/- 2.46 (SD); it was -0.38 +/- 0.66 D after a mean follow-up of 4.41 +/- 2.32 months. In the hyperopic cases, the preoperative SE was +3.54 +/- 1.57 D; it was +0.33 +/- 0.50 D after a mean follow-up of 3.42 +/- 3.23 months. Cylinder vectorial change, visual acuity, and the number of visual acuity lines gained or lost were also evaluated in both groups.

CONCLUSION

Although some features of our algorithm for corneal-topography-assisted customized ablations should be modified, the results of our treatment of cases with asymmetrical astigmatism were encouraging.

Deep sclerectomy with a collagen implant using the excimer laser

We describe a new technique of nonpenetrating glaucoma surgery that uses the excimer laser to reduce the risk of perforating the trabeculo-Descemet's membrane. With this technique, the ablation is precise and homogeneous. A collagen device is sutured over the scleral bed to create an outflow pathway for aqueous humor drainage. After a superficial scleral flap is dissected with a diamond knife, the sclera, under direct visualization, is ablated with the excimer laser over Schlemm's canal until aqueous humor percolates through from the anterior chamber. A collagen device is placed over the sclera to allow the aqueous humor to flow from the anterior chamber through the trabeculo-Descemet's membrane. The preliminary results show a drop in intraocular pressure to the middle teens.

Smoothness of Ablation on Acrylic by Four Different Excimer Lasers

PURPOSE

There are many different excimer laser devices available for photoablative refractive surgery. Smoothness of ablation may vary with different excimer lasers systems.

METHODS

Ablations were performed on polymethylmethacrylate (PMMA) plates of 8 x 4 x 0.5 cm, with four different excimer lasers: VISX-Star, Coherent Schwind Keratom I/II, Chiron Technolas Keracor 117C (Plano Scan), and the Nidek EC-5000, to determine and compare the homogeneity and smoothness of the surface. Ten -3.00 D samples, ten -6.00 D samples, and ten -9.00 D samples were ablated with each laser. The PMMA discs were examined with optical microscopy, documented by photographs, and each sample was measured quantitatively using a Hommel-Werkel rugosimeter. We used the same PMMA material throughout.

RESULTS

Statistically significant differences in smoothness were found between the Chiron Technolas 117C and the VISX-Star, Nidek and VISX-Star, and Coherent Schwind and VISX-Star in the homogeneities achieved by ablating -3.00 D. Ablations of -6.00 D resulted in homogeneities that were statistically significantly different: Chiron Technolas 117C with the other three devices, the Nidek EC-5000 with the VISX-Star, and the Coherent-Schwind with the VISX-Star. In the ablations for -9.00 D, statistically significant differences in homogeneity were found between the Chiron Technolas 117C and Nidek, between the Chiron and VISX-Star, between the Coherent Schwind and VISX-Star, and between the Nidek and VISX-Star. The laser with the scanning spot system was smoother.

CONCLUSION

Scanning spot technology produced smooth ablations even up to -9.00 D.

Contrast sensitivity assessment using the visual performance tester

The visual performance tester (VPT), a device that uses patient response time as a variable to assess visual power, is described. Results in 126 emmetropic eyes that had not had surgery are presented. The VPT provides more complete and accurate information about visual performance than the standard visual acuity examination because the device considers all variables involved in visual function results.

Laser in situ keratomileusis versus arcuate keratotomy to treat astigmatism

PURPOSE

To analyze the effectiveness of laser in situ keratomileusis (LASIK) and arcuate keratotomy (AK) to treat simple myopic, compound myopic, and mixed astigmatism.

SETTING

Instituto de la Visión, Buenos Aires, Argentina.

METHODS

This retrospective nonrandomized study comprised 821 cases treated with LASIK and 46 cases treated with AK. Patients were divided into 4 groups, which had the following preoperative cylinder corrections: simple myopic astigmatism (Group 1) (LASIK: n = 76, -3.91 diopters [D] +/- 1.29 [SD]; AK: n = 5, -3.85 +/- 0.65 D); compound myopic astigmatism up to 2.00 D (Group 2) (LASIK: n = 401, -1.69 +/- 0.76 D; AK: n = 14, -1.48 +/- 0.41 D); compound myopic astigmatism over 2.00 D (Group 3) (LASIK: n = 253, -3.61 +/- 0.89 D; AK: n = 16, -3.09 +/- 0.84 D); mixed astigmatism (Group 4) (LASIK: n = 91, +3.65 +/- 1.62 D; AK: n = 11, 4.39 +/- 0.92 D).

RESULTS

Six months postoperatively, the cylinder's vector-corrected change was as follows: Group 1, LASIK 3.75 +/- 1.08 D, AK 3.16 +/- 0.84 D; Group 2, LASIK 1.55 +/- 1.12 D, AK 1.34 +/- 0.44 D; Group 3, LASIK 3.39 +/- 0.98 D, AK 2.70 +/- 1.21 D; Group 4, LASIK 3.77 +/- 1.43 D, AK 3.75 +/- 0.89 D. Respective mean uncorrected visual acuities in each group were as follows: Group 1, 0.71 +/- 0.12 and 0.60 +/- 0.12; Group 2, 0.83 +/- 0.12 and 0.78 +/- 0.24; Group 3, 0.78 +/- 0.18 and 0.48 +/- 0.24; Group 4, 0.69 +/- 0.21 and 0.55 +/- 0.18.

CONCLUSIONS

The vector-corrected change and visual acuity achieved with LASIK were better, although not significantly, than those attained with AK except for the UCVA obtained with LASIK in eyes with compound myopic astigmatism over 2.00 D. Both methods proved to be safe.

An Intersurface Stress Tensor

Distributed forces resulting from molecular interactions between macroscopic bodies are usually concentrated near surfaces. A new formulation has been developed that replaces these distributed body forces by effective surface tractions and is not limited by the geometrical restrictions of Derjaguin's approximation. It offers great computational simplification over the use of the body-force distribution. The body-force distribution is integrated and partitioned to various surface elements. The resulting expressions for surface traction involve a second-order tensor termed the intersurface stress tensor. It is a symmetric tensor defined for any body in terms of the intermolecular potential and the shape of the body. It acts much like the internal stress tensor; the surface traction vector on a surface introduced into its field is the inner product of the tensor and the surface normal. The new surface formulation reduces to Derjaguin's approximation for the case of a half-space with a plane surface. Properties of the new tensor are explored. Actual components are derived for several geometries.

Incidence of postoperative posterior capsular opacification with types of senile cataracts

The most frequent postoperative complication in extracapsular cataract surgery is opacification of the posterior capsule. The purpose of this study was to correlate the frequency of capsular opacification with each kind of senile cataract. A total of 566 eyes with cataracts were studied. They had been operated on between 1980 and 1990 using the extracapsular, intercapsular, and phacoemulsification techniques. Our results confirm that senile complete cataracts (mature cataracts) had a significantly lower tendency to produce postoperative capsular opacification than other cataract types (nuclear, cortical, posterior subcapsular).

Study of the lens epithelial cell density in cataractous eyes operated on with extracapsular and intercapsular techniques

Epithelial cell counting was performed in 47 fragments from lens anterior capsules obtained during extracapsular and intercapsular surgery. Mean cell count was 3,277 cell/mm2; there was no correlation between cell number and age and no significant difference in cell counts between extracapsular and intercapsular surgery. There were, however, significant differences between advanced cataracts and the other cataract types (2,947 vs. 3,356). This may be important in explaining the differences in regenerative opacification of the posterior capsule in the different types of cataracts.

Scanning electron microscopy of the trabecular meshwork in normal and glucomatous eyes

The ultrastructure of trabeculectomy specimens obtained from enucleated eyes was compared to that of 23 similar specimens extracted from glaucomatous eyes. It was thus possible to study the trabecular meshwork from Schwalbe's line to the iris root, the corneal endothelium, the canal of Schlemm, its inner and outer walls, and the collectors. In the glaucomatous specimens it was possible to verify, for the first time, two aspects which show clinical correlation. The first aspect is pseudoexfoliation: we find in the trabecular meshwork two types of deposits in great quantity. One is formed by a dense irregular fibrillar net, with a diameter oscillating betwwwn 600 and 830 A, surrounding the trabeculae; the others are pigment granules. Both fill the intertrabecular spaces. The first type is also observed on the corneal endothelium lining Schwalbe's ring, stressing the visibility of the intercellular spaces. The second aspect is the pectinate ligament (mesodermic remnant) in late-onset congenital glaucoma. Its pattern is characteristically different from that of the corneoscleral meshwork.