Peripheral defocus of monofocal intraocular lenses.

PURPOSE: To quantify the angular dependence of monofocal intraocular lens (IOL) power. SETTING: Ophthalmic Biophysics Laboratory, Kallam Anji Reddy campus, L V Prasad Eye Institute, Hyderabad, India. DESIGN: Laboratory study. METHODS: Experiments were performed on IOLs from 2 different manufacturers (APPALENS 207, Appasamy Associates and SN60WF, Alcon Laboratories, Inc.). IOL powers ranged from 17 to 25 diopters (D). The IOLs were mounted in a fluid-filled chamber, and the on-axis and off-axis powers were measured using a laser ray tracing system over the central 3 mm zone with delivery angles ranging from -30 to +30 degrees in 5-degree increments. The position of the best focus was calculated for each IOL at each angle. The angular dependence of IOL power was compared with theoretical predictions. RESULTS: Peripheral defocus increased significantly with increasing incidence angle and power. The peripheral defocus at ±30 degrees increased from 5.8 to 8.5 D when the power increased from 17.5 to 24.5 D for APPALENS 207 and from 4.9 to 7.4 D when the power increased from 17 to 25 D for SN60WF. The mean difference between the measured and theoretical tangential power at ±30 degrees was 0.50 ± 0.16 D for the APPALENS 207 and -0.40 ± 0.10 D for the SN60WF, independent of IOL power. CONCLUSIONS: IOLs introduce a significant amount of peripheral defocus which varies significantly with IOL power and design. Given that peripheral defocus is related to lens power, replacement of the crystalline lens (approximately 24 D) with an IOL will produce a significant difference in peripheral defocus profile after surgery.

Effectiveness of simulation-based training for manual small incision cataract surgery among novice surgeons: a randomized controlled trial.

This study was designed to determine the effect of a novel simulation-based training curriculum for scleral tunnel construction in manual small incision cataract surgery (MSICS) compared with traditional training. In this multicenter, investigator-masked, randomized clinical trial, resident surgeons within 3 months of matriculation with minimal or no prior experience with MSICS were assigned either to simulation-based training, the Experimental Group (EG), or to conventional training, the Control Group (CG). EG residents were trained to perform scleral tunnel construction using a simulation-based curriculum (HelpMeSee Eye Surgery Simulator), while residents in the CG followed institution-specific curriculum before progressing to live surgery. Surgical videos of the first 20 attempts at tunnel construction were reviewed by masked video raters. The primary outcome was the total number of any of 9 pre-specified errors. On average, the total number of errors was 9.25 (95% CI 0-18.95) in the EG and 17.56 (95% CI 6.63-28.49) in the CG (P = 0.05); the number of major errors was 4.86 (95% CI 0.13-9.59) in the EG and 10.09 (95% CI 4.76-15.41) in the CG (P = 0.02); and the number of minor errors was 4.39 (95% CI 0-9.75) in the EG and 7.47 (95% CI 1.43-13.51) in the CG (P = 0.16). These results support that novice surgeons trained using the novel simulation-based curriculum performed fewer errors in their first 20 attempts at tunnel construction compared to those trained with a conventional curriculum.

Pregnancy-induced keractesia - A case series with a review of the literature.

We report a case series of patients who developed post-laser-assisted in situ keratomileusis (LASIK) ectasia or had a progression of keractesia during pregnancy. We reviewed the medical records of 12 patients (20 eyes) who had reported deterioration of vision during their pregnancy and were diagnosed with keractesia. All 12 patients had experienced symptoms of deterioration of vision between 2 months to 1 year of onset of their pregnancies. A total of 17 eyes of 10 patients had developed post-refractive surgery keractesia. Sixteen of these had undergone LASIK and one had undergone femtosecond lenticule extraction (FLEX). Three eyes of two patients had an exacerbation of keratoconus during pregnancy while one patient had associated hypothyroidism. The results indicate that the hormonal changes that take place in pregnant women can affect the biomechanical stability of the cornea and may trigger the onset of keractesia.