Accuracy of intraocular lens power calculations in eyes with axial length <22.00 mm.

BACKGROUND: To assess the accuracy of Haigis, Holladay 1, Hoffer Q and SRK/T formulae in eyes with axial length of <22.00 mm. DESIGN: Retrospective comparative analysis. PARTICIPANTS: 163 eyes of 97 patients undergoing phacoemulsification and intraocular lens (IOL) implantation. METHODS: Ocular biometry was performed using IOLMaster laser interferometry. Predicted refractive outcomes before and after lens constant adjustment were compared to actual refractive outcomes. MAIN OUTCOME MEASURES: Mean prediction (ME) and mean absolute errors (MAE) with standard deviations (±SD). RESULTS: Mean preoperative spherical equivalent was +5.44D ± 1.97D. Mean axial length was 21.20 mm ± 0.60 mm. Using standard IOL constants the MAE for Hoffer Q (0.62D, ±0.52D) and Holladay 1 (0.66D ± 0.52D) were significantly lower than SRK/T (MAE 0.91D ± 0.64D; P = <0.0005 and P = 0.001 respectively), but not Haigis (MAE 0.82D ± 0.83D, P = 0.071 and 0.22 respectively). MAEs for all formulae were significantly reduced by IOL constant adjustment (all P = <0.001). Following this there was no statistically significant difference in MAEs between formulae (range 0.50-0.57D, P = 0.57). Increasing MAE was significantly associated with reducing axial length and increasing IOL power for all formulae. For bilateral cases, prediction errors between eyes were significantly correlated across all formulae (all P = <0.0001) and explained 32-42% of the variance in prediction error between eyes. CONCLUSIONS: Prediction of postoperative refraction in patients with short axial lengths is challenging and at the limit of current, popular IOL formulae. There is now a clear need for prospective studies to assess latest generation IOL formulae such as Holladay 2 or Olsen in small eyes.

Double-clip technique in cataract surgery using topical anesthesia.

We describe a simple technique that reduces the effect of blepharospasm in the presence of sub-Tenon's or topical anesthesia without the administration of a lid block or a reduction in adequate analgesia.

Estimation of true corneal power after keratorefractive surgery in eyes requiring cataract surgery: BESSt formula.

PURPOSE: To describe a new formula, BESSt, to estimate true corneal power after keratorefractive surgery in eyes requiring cataract surgery. SETTING: Moorfields Eye Hospital, London, United Kingdom. METHODS: The BESSt formula, based on the Gaussian optics formula, was developed using data from 143 eyes that had keratorefractive surgery. The formula takes into account anterior and posterior corneal radii and pachymetry (Pentacam, Oculus) and does not require pre-keratorefractive surgery information. A software program was developed (BESSt Corneal Power Calculator), and corneal power was calculated in 13 eyes that had keratorefractive surgery and required cataract surgery. RESULTS: In the eyes having phacoemulsification, target refractions calculated with the BESSt formula were statistically significantly closer to the postoperative manifest refraction (mean deviation 0.08 diopters [D] +/- 0.62 [SD]) than those calculated with other methods as follows: history technique (-0.07 +/- 1.92 D; P = .05); history technique with double-K adjustment (0.13 +/- 2.39 D; P = .05); Holladay 2 with K-values estimated with the contact lens method (-0.76 +/- 1.36 D; P = .03); Holladay 2 with K-values from Atlas topographer (Humphrey) (-0.55 +/- 0.61 D; P<.01). Using the BESSt formula, 46% of eyes were within +/-0.50 D of the intended refraction and 100% were within +/-1.00 D. CONCLUSIONS: The BESSt formula was statistically significantly more accurate than the other techniques tested. Thus, it could significantly improve intraocular lens power calculation accuracy after keratorefractive surgery, especially when pre-refractive surgery data are unavailable.

Predictors of femtosecond laser intrastromal astigmatic keratotomy efficacy for astigmatism management in cataract surgery.

PURPOSE: To evaluate the factors associated with the efficacy of femtosecond laser intrastromal astigmatic keratotomy (AK). SETTING: Moorfields Eye Hospital, London, United Kingdom. DESIGN: Prospective case series. METHODS: Eyes having intrastromal AK for corneal cylinder correction were analyzed. Preoperative biometric parameters included axial length, anterior chamber depth, central corneal thickness, and Ocular Response Analyzer corneal hysteresis (CH) and corneal resistance factor (CRF). Preoperative and 1-month postoperative corneal keratometry was measured using the Topcon KR8100PA topographer-autorefractor. Astigmatic analyses were performed using the Alpins method. RESULTS: The study analyzed 319 eyes of 213 patients with a mean target induced astigmatism of 1.24 diopters (D) ± 0.44 (SD), mean surgically induced astigmatism (SIA) of 0.71 ± 0.43 D, and mean difference vector of 0.79 ± 0.41 D. Two multiple regression models were constructed for SIA prediction. Model 1, based on previous manual limbal relaxing incision parameters, confirmed age and astigmatism meridian (with/against the rule and oblique) to be associated with SIA in addition to AK arc length, AK start depth, and preoperative corneal cylinder magnitude. Model 2, additionally considering other parameters, found only lower CH (-0.06 DC per unit CH), a higher CRF (0.04 D per unit CRF), and the astigmatism meridian to be independent predictors of greater SIA (after adjusting for intrastromal AK arc length, start depth, and preoperative corneal cylinder). With-the-rule astigmatism was associated with a 0.13 D higher SIA than against-the-rule astigmatism, holding all other variables constant. CONCLUSION: Corneal biomechanical parameters and astigmatism meridian were independent predictors of femtosecond laser intrastromal AK efficacy even after adjusting for AK arc length, AK start depth, and preoperative corneal cylinder. FINANCIAL DISCLOSURE: Dr. Stevens is a previous consultant to Optimedica, Inc. which is now part of Abbott Medical Optics, Inc. Drs. Stevens and Day have no financial or proprietary interest in any material or method mentioned.

Stability of Keratometric Astigmatism After Non-penetrating Femtosecond Laser Intrastromal Astigmatic Keratotomy Performed During Laser Cataract Surgery.

PURPOSE: To investigate the stability of keratometric astigmatism after femtosecond laser intrastromal astigmatic keratotomy (ISAK) performed during laser cataract surgery. METHODS: In this prospective comparative case series, data were collected from patients during follow-up 1 and 6 months after laser-assisted cataract surgery. Corneal keratometry was measured preoperatively and postoperatively by Topcon KR8100PA topographer-autorefractor (Topcon Corporation, Tokyo, Japan). Astigmatic analyses were performed by Alpins' method to calculate surgically induced astigmatism (SIA). All operations were performed by a single surgeon. RESULTS: Data were available on 263 eyes, of which 87 had undergone ISAK during cataract surgery for astigmatism management (cases) and 176 had cataract surgery without ISAK (controls). For ISAK cases, comparing the magnitudes of the individual SIA vectors at 1 and 6 months postoperatively showed a 0.09 diopters cylinder (DC) regression (P = .009). Calculating the change in SIA between 1 and 6 months considering both magnitude and angular direction, the mean regression vector was 0.08 DC @ 94°. For controls (without ISAK), comparing the magnitudes of the individual SIA vectors at 1 and 6 months postoperatively showed a 0.11 DC regression (P < .001). Calculating the change in SIA between 1 and 6 months considering magnitude and angular direction, the mean vector was 0.14 DC @ 88°. There was no significant difference in SIA regression magnitudes between cases and controls. CONCLUSIONS: For both cases with and without ISAK, there were small but statistically significant regressions in SIA between 1 and 6 months postoperatively. These values were low and appear to be of little clinical significance.

Nonpenetrating femtosecond laser intrastromal astigmatic keratotomy in eyes having cataract surgery.

PURPOSE: To describe the effect of femtosecond laser intrastromal astigmatic keratotomy (AK) performed during cataract surgery. SETTING: Moorfields Eye Hospital, London, United Kingdom. DESIGN: Prospective case series. METHODS: This study comprised patients having laser cataract surgery with concurrent astigmatism management by intrastromal AK. All eyes had greater than 0.7 corneal diopter (D) cylinder. An intrastromal AK nomogram with 8.0 mm diameter paired symmetric limbal centered arcs was used. Corneal keratometry was measured preoperatively and 1 month postoperatively using a KR8100PA topographer-autorefractor. Astigmatic analyses were performed using the Alpins method considering 3 vectors-target induced astigmatism (TIA), surgically induced astigmatism (SIA) and difference vector (DV)-and calculation of coupling measures. RESULTS: In all, 196 eyes of 133 patients were analyzed. The mean TIA (equivalent to preoperative corneal cylinder) was 1.21 D ± 0.42 (SD) (range 0.75 to 2.64 D) and the mean SIA was 0.74 DC ± 0.40 (range 0.00 to 2.86). The mean difference vector was 0.74 ± 0.38 D (range 0.00 to 2.25 D). The mean correction index was 0.63 ± 0.32 (range 0.00 to 1.93), indicating that the mean astigmatism correction was 63%. Fourteen eyes (7.1%) and 7 eyes (3.6%) had an astigmatism correction of greater than 100% and greater than 120%, respectively. Overall 0%, 48.5%, and 51.5% of eyes had 0.50 D or less, 1.0 D or less, or greater than 1.0 D, respectively, preoperatively compared with 32.1%, 85.7%, and 14.3%, postoperatively. There were no cases of corneal endothelial perforation or inadvertent placement within the visual axis. CONCLUSIONS: The intrastromal AKs were easily programmed as an integral part of laser-assisted cataract surgery without additional cost, significantly reduced corneal cylinder, and appeared to be safe through 1 month of follow-up. FINANCIAL DISCLOSURE: Dr. Day was supported by the National Institute for Health Research (NIHR) Biomedical Research Centre based at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology. Dr. Stevens has been a consultant to Optimedica Inc., now part of Abbott Medical Optics.

Comparison of dynamic digital pupillometry and static measurements of pupil size in determining scotopic pupil size before refractive surgery.

PURPOSE: To compare 2 digital infrared pupillometers. SETTING: Anterior Segment Service, Moorfields Eye Hospital, London, England. METHODS: Eighty-eight eyes of 44 healthy subjects were recruited into the study. The scotopic pupil size was measured with 2 instruments, a digital pupillometer (Procyon) and a Hartman-Shack wavefront aberrometer (Visx WaveScan). Agreement between the instruments was assessed. RESULTS: There were 21 men and 23 women with a mean age 38.1 years +/- 9.2 (SD) (range 23 to 62 years). The mean scotopic pupil diameter was significantly larger with the WaveScan (6.61 +/- 0.92 mm) than with the Procyon pupillometer (6.40 +/- 0.90 mm), P<.001. CONCLUSIONS: There was good agreement in measurement of scotopic pupil size between the two instruments. The larger pupil diameter found with the Visx WaveScan than with the Procyon digital pupillometer probably represents the different illumination level used by each instrument, the effects of accommodation, and target fogging.

Fixed dilated pupil (Urrets-Zavalia syndrome) after air/gas injection after deep lamellar keratoplasty for keratoconus.

PURPOSE: To describe three cases of fixed dilated pupil and presumed iris ischemia (Urrets-Zavalia syndrome) after anterior chamber air/gas injection after deep lamellar keratoplasty for keratoconus. METHODS: Interventional case series. Three eyes of three patients with keratoconus underwent deep lamellar keratoplasty and intraoperative or postoperative injection of air/gas in the anterior chamber to appose the host-donor lamellar graft interface. RESULTS: Urrets-Zavalia syndrome was diagnosed on clinical grounds in three cases and was associated with the Descemet membrane microperforation intraoperatively and introduction of air/gas into the anterior chamber intraoperatively or postoperatively. CONCLUSION: A fixed dilated pupil is an uncommon complication of penetrating keratoplasty for keratoconus that can also develop after deep lamellar keratoplasty. Leaving an air or gas bubble in the anterior chamber of a phakic eye after deep lamellar keratoplasty is a risk factor and should therefore be avoided.

Results of photorefractive keratectomy for hyperopia using the VISX star excimer laser system.

PURPOSE: To evaluate safety, efficacy, and predictability of photorefractive keratectomy (PRK) for hyperopic astigmatism of +1.75 to 00 D manifest refractive sphere and up to -2.50 D manifest refractive astigmatism using the VISX Star excimer laser system, version 2.5 software. METHODS: Treatment was performed on 32 eyes of 21 patients. Eighteen of 21 patients were 45 years of age or older. Manifest and cycloplegic refraction together with Pelli-Robson contrast sensitivity assessment was performed prior to surgery and 1, 3, 6, 12, and 24 months after treatment. RESULTS: Twenty-seven of 32 surgical procedures were reviewed 1 year after treatment (84%). Corneal epithelial healing was complete between day 4 and 10. Twelve months after treatment, 25 of 27 eyes (93%) achieved 20/40 or better uncorrected visual acuity and 19 eyes (70%) achieved 20/20. No patient lost two or more lines of Snellen visual acuity assessed 6 months and later after treatment. The mean spherical equivalent refraction was reduced from +2.90 at baseline to +0.10 D at 1 year and +0.40 D at 2 years; 65% of eyes had a refraction within +/- 0.50 D. Four patients had further treatment by laser in situ keratomileusis for undercorrection in three eyes and overcorrection in one eye. Pelli-Robson contrast acuity was significantly reduced 12 months after treatment from a mean 1.72 before to 1.66 after PRK (P = .02, t-test). CONCLUSIONS: PRK for hyperopia using the VISX Star excimer laser system was effective in the treatment of hyperopic astigmatism. Although no patient lost two or more lines of high contrast best spectacle-corrected Snellen visual acuity 1 year after treatment, there was a significant decrease in Pelli-Robson contrast acuity.

Prospective study of photorefractive keratectomy for myopia using the VISX StarS2 excimer laser system.

PURPOSE: To evaluate the safety, efficacy, and predictability of excimer laser photorefractive keratectomy (PRK) for compound myopic astigmatism using the VISX StarS2 excimer laser system with international version 3.1 software. METHODS: We report a prospective consecutive study of myopic excimer laser PRK, performed in a multi-surgeon environment with 200 eyes of 117 patients, to correct naturally occurring compound myopic astigmatism of between -0.50 to -5.90 D manifest refractive sphere and up to -3.50 D manifest refractive astigmatism. Patients were assessed prior to surgery and at 1, 3, 6, and 12 months after treatment. RESULTS: One hundred and ninety-eight of 200 treatments (99%) were reviewed 1 year after surgery; 193 of 198 eyes (97%) achieved 20/40 or better uncorrected visual acuity and 163 of 198 eyes (82%) achieved 20/20 or better. One eye lost two lines of Snellen visual acuity assessed at 12 months but recovered acuity when assessed at 18 months. Mean spherical equivalent corneal plane power was reduced from -3.50 to +0.90 D 1 month after treatment and 0 D at 12 months (SD 0.67 D). Three eyes of three patients underwent further treatment, two with LASIK and one with PRK for residual refractive error. Refractive astigmatism of >1.00 D was reduced from a mean -1.70 to -0.70 D at 1 year after treatment. Vector magnitude was 79% of that intended and mean vector axis error (absolute) was 8.5 degrees. No eye had a severe haze response. Pelli-Robson contrast acuity was significantly reduced after treatment from a mean 1.72 D preoperatively to 1.63 D at 12 months (P<.01). CONCLUSIONS: PRK for myopia using the VISX StarS2 excimer laser system was effective in the treatment of low myopic astigmatism, although there was a significant reduction in Pelli-Robson contrast sensitivity.

Efficacy of anterior capsulotomy creation in femtosecond laser-assisted cataract surgery.

PURPOSE: To report the rate of complete capsulotomies without adhesions and anterior capsule tears using the Catalys femtosecond laser. SETTING: Moorfields Eye Hospital, London, United Kingdom. DESIGN: Prospective consecutive case series. METHODS: This study evaluated femtosecond laser-assisted cataract cases performed between January 2013 and March 2014. Platform software versions 2.15, 2.15.13, and 2.20 were used. RESULTS: A complete 360-degree capsulotomy (without adhesions or bridging tags, so free floating at the entire capsulotomy circumference) was present in 998 (99.8%) of the 1000 cases (95% confidence interval [CI], 99.2% to >99.9%). None of these cases had intraoperative anterior capsule tears. In the 2 cases in which the capsulotomy was incomplete, 1 was due to the laser being aborted during capsulotomy and was completed manually without incident. The second was in a routine procedure with a single adhesion (bridging tag) at capsulotomy removal and a radial tear (not extending to the posterior capsule) identified after nucleus removal. Thus, the rate of anterior capsule tear was 0.1% (1 in 1000) (95% CI, 0.01% to 0.62%). CONCLUSION: The results suggest high efficacy and safety of this femtosecond laser system in creating capsulotomies.

Outcomes of phacoemulsification and intraocular lens implantation in microphthalmos and nanophthalmos.

PURPOSE: To evaluate the outcomes of phacoemulsification and intraocular lens (IOL) implantation in microphthalmos and nanophthalmos. SETTING: Moorfields Eye Hospital, London, United Kingdom. DESIGN: Retrospective case series. METHODS: Eyes with an axial length (AL) less than 21.0 mm had elective phacoemulsification and IOL implantation. RESULTS: One hundred three eyes (63 patients) were enrolled. The median AL was 20.65 mm (interquartile range [IQR], 20.26 to 20.86) and the median follow-up, 6.3 months. Complications occurred in 16 cases (15.5%). Zonular dehiscence, severe uveitis, and aqueous misdirection accounted for the majority of complications. Complication rates were 6 (7.3%) of 82 cases with an AL from 20.0 to 21.00 mm and 10 (47.6%) of 21 cases with an AL less than 20.0 mm (P=.0001). Only AL (odds ratio [OR], 0.52 per mm; P≤.0005) and abnormal intraocular pressure (IOP) of 22 mm Hg or more or on topical IOP control (OR, 10.1; P=.001) were significant independent risk factors for complications. For the cohort after adjusting for abnormal IOP, an AL less than 20.5 mm was associated with a 4 times higher odds of any complication (P=.028), an AL less than 20.0 mm was associated with a 15 times higher odds of any complication (P≤.0005), and an AL less than 19.00 mm was associated with a 21 times higher odds of any complication (P≤.0005). CONCLUSIONS: Phacoemulsification and IOL implantation in microphthalmos/nanophthalmos was challenging but appears safer than previously reported. A shorter AL and abnormal IOP were significant risk factors for complications.

Moorfields technique of donor cornea mounting for femtosecond-assisted keratoplasty: use of viscoelastic in the artificial anterior chamber.

Appropriate mounting and cutting of the donor sclero-corneal cap is often cumbersome during femtosecond laser-assisted keratoplasty. The authors describe a technique for donor cornea femtosecond laser cutting using ophthalmic viscoelastic devices. The donor sclero-corneal cap is mounted on the artificial anterior chamber using a dispersive ophthalmic viscoelastic device instead of saline solution. The chances of artificial anterior chamber pressure loss, inadequate applanation, and fluid leaks are consistently reduced with the use of dispersive ophthalmic viscoelastic devices. The speed of donor femtosecond laser cutting is increased. The viscosity and elasticity of dispersive ophthalmic viscoelastic devices greatly assist the procedure with regard to ease of applanation, corneal endothelium protection, and decreased distortion of the applanated cornea.

Effect of the angle of the operating microscope light beam on visual recovery after phacoemulsification: Randomized trial.

PURPOSE: To evaluate differences in visual recovery after phacoemulsification with direct or tilted surgical microscope illumination using a macular photostress test. SETTING: Western Eye Hospital, Imperial College Health Care National Health Service Trust, London, United Kingdom. METHODS: This randomized double-masked controlled trial enrolled patients presenting to a daycare unit for single-eye cataract surgery. Inclusion criteria were no ocular pathology other than cataract, corneal keratometric astigmatism less than 1.50 diopters, intended target of emmetropia in the operated eye, and cataract grade 1 to 3 (Lens Opacification Classification System II). Exclusion criteria were an abnormal preoperative photostress test. Patients were randomized to have phacoemulsification with the operating microscope angled 15 degrees nasal to the fovea (study group) or with the operating microscope directly overhead around the optic disc region (control group). The same surgeon performed all phacoemulsification procedures using a standardized technique and topical anesthesia. Outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuity 10 minutes and 60 minutes postoperatively. RESULTS: In the 30 patients evaluated, the mean UDVA 10 minutes postoperatively was 0.40 logMAR +/- 0.26 (SD) in the study group and 0.72 +/- 0.36 logMAR in the control group (P<.01). The mean CDVA was 0.18 +/- 0.26 logMAR and 0.44 +/- 0.30 logMAR, respectively (P = .016). There was no significant between-group difference in acuity at 60 minutes. CONCLUSION: Tilting the microscope beam away from the fovea resulted in faster visual recovery and less macular photic stress. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.