Corneal perforation due to vitamin A deficiency in a patient with short bowel syndrome.

A 55-year-old Caucasian woman presented with a 1-week history of left eye redness and blurred vision. Her medical history included previous small bowel resection and ileostomy for ischaemic bowel. Ophthalmic examination revealed a left corneal ulcer requiring hospital admission for intensive topical antibiotics. Overnight she became systemically unwell and was diagnosed with urinary tract infection requiring intravenous antibiotics. Her corneal condition deteriorated resulting in corneal perforation, which required a surgical gluing procedure. Despite surgery, the cornea perforated on two further occasions. At this stage, vitamin A deficiency (VAD) was suspected, due to the corneal melting response that was occurring. VAD was subsequently confirmed by serology and had occurred in this case due to malabsorption as a result of short bowel syndrome caused by previous small bowel surgery. The patient was treated with intramuscular vitamin A and eventually made a good visual and systemic recovery.

Peripheral ulcerative keratitis and corneal melt: a 10-year single center review with historical comparison.

PURPOSE: Management of noninfectious ulcerative keratitis (UK) and associated systemic disorders has changed over recent years. This study aimed to analyze a recent cohort of patients with UK in this context. METHODS: The case notes of all the patients attending a specialist corneal immunosuppression clinic between June 2002 and July 2012 were reviewed. A subgroup comparison of those with rheumatoid arthritis (RA) was made with those included in an earlier report from this same center (Malik et al. Eur J Ophthalmol. 2006;16:791-797). The Fisher exact test was used for statistical comparison, and a Bonferroni correction was applied. RESULTS: Seventy patients, whose mean age was 65.0 years (median, 64 years), were included. Fifteen (21%) had bilateral disease, and forty-six had RA (66%). At presentation, the mean (median) visual acuity (VA) was 0.59 (0.18) logarithm of the minimum angle of resolution equivalent to 6/24 (6/9) Snellen. All the patients were prescribed systemic corticosteroids, which were later stopped in 45 (64%) patients. All but 2 were treated with steroid-sparing immunosuppressive agents, with each patient being prescribed a mean of 1.5 medications (range, 0-4), including prednisolone. These included prednisolone (70, 100%), methotrexate (47, 67%), mycophenolate (15, 21%), tacrolimus (5, 7%), and azathioprine (4, 6%). No irreversible side effects occurred. After perforation, 12 eyes of 11 patients (16%) underwent a corneal transplantation, and 10 (83%) of these remained clear. The mean (median) VA of the affected eyes when last seen was 0.34 (0.18) logarithm of the minimum angle of resolution equivalent to 6/13 (6/9) Snellen. The subset of patients with RA had significantly lower rates of corneal perforation and a VA ≤ 6/60 when last seen (P < 0.05) compared with that of the earlier cohort. CONCLUSIONS: Ocular morbidity associated with UK has fallen, possibly because of a move toward more aggressive systemic antiinflammatory therapy.

In vitro quantification of the stiffening effect of corneal cross-linking in the human cornea using radial shearing speckle pattern interferometry.

PURPOSE: To quantify the magnitude of the stiffening effect of corneal cross-linking (CXL) by studying intact human corneas exposed to physiological pressure transients. METHODS: Nine organ-cultured human corneas mounted in artificial anterior chambers were studied. A radial shearing speckle pattern interferometer was used to measure changes in corneal strain following an increase in artificial anterior chamber pressure from 15.0 to 15.5 mmHg before and after treatment. Measurements were taken from all corneas with their epithelium intact before all underwent epithelial debridement. Three specimens were used as controls and did not receive any further treatment; three underwent riboflavin/ultraviolet A (UVA) CXL using 30 minutes of 370-nm irradiation at 3 mW/cm2 following epithelial removal and saturation with 0.1% riboflavin; and three were fixed with the cross-linking agent 2.5% glutaraldehyde. Strain measurements were repeated after these treatments. Young's moduli of individual corneas were calculated by mathematical analysis. RESULTS: Mean donor age was 81.7 years. Before treatment, the mean Young's moduli of the control, riboflavin/UVA CXL, and glutaraldehyde-fixed corneas did not differ significantly: 0.46±0.03, 0.48±0.03, and 0.47±0.03 MPa, respectively. Following treatment these values changed to 0.46±0.2, 2.06±0.22, and 3.48±0.41 MPa, respectively. In proportional terms, this was equivalent to an increase in corneal Young's modulus by a factor of 4.3 (P<.05) following riboflavin/UVA CXL and 7.3 (P<.05) after glutaraldehyde fixation. CONCLUSIONS: Riboflavin-UVA CXL increases the stiffness of organ-cultured corneas by a factor of more than four. This finding quantifies the efficacy of CXL in a physiologic configuration.

Effects of variation in depth and side cut angulations in LASIK and thin-flap LASIK using a femtosecond laser: a biomechanical study.

PURPOSE: To study the corneal biomechanical effects of varying LASIK flap depth and side cut angulations and evaluate the relative contribution of the lamellar and side cuts using a femtosecond laser and radial shearing speckle pattern interferometry (RSSPI). METHODS: Forty-two organ-cultured human corneas were divided into a control group and three investigative groups, each undergoing different incision types at both 90- and 160-µm depth using a femtosecond laser. In the first group, typical LASIK flaps were created; in the second group, only the bed was cut (delamination); and in the third group, side cuts alone were affected. Corneal strain was measured using RSSPI before and after treatment following an increase in hydrostatic pressure from 15.0 to 15.5 mmHg and again after 1 week of incubation in culture medium. RESULTS: The flap group demonstrated a weakening of strength related to the depth of cut, with strain increasing by 9% and 32% at 90 and 160 µm, respectively. Similar changes, 9% and 33%, were observed following execution of side cuts to the same depths. By contrast, strain increase following delamination showed no relationship with depth, increasing by 5% in both instances. When the side cut angle was made more acute, strain decreased with a 2% strain increase being measured after a 90-µm, 150° side cut was created. No significant changes occurred during the period of organ culture. CONCLUSIONS: Vertical side cuts through corneal lamellae rather than horizontal delamination incisions contribute to the loss of structural integrity during LASIK flap creation. Angulating side cuts such that the stromal diameter of the flap exceeds its epithelial diameter can decrease this effect.

First eye prediction error improves second eye refractive outcome results in 2129 patients after bilateral sequential cataract surgery.

OBJECTIVE: To define theoretical correction factors for second-eye intraocular lens (IOL) power adjustment based on first eye refractive prediction error (PE). DESIGN: Database study. PARTICIPANTS: We included 2129 patients who underwent bilateral sequential phacoemulsification cataract surgery with the same IOL model. METHODS: Retrospectively calculated PEs (Hoffer Q, Holladay 1, SRK/T) were analyzed for association between paired eyes, examining the effect of interocular differences in axial length (AL) and corneal power. A range of correction factors (CF) derived from the first eye PE were applied to the second eye PE using optimized and non-optimized IOL constants (IOLCs). MAIN OUTCOME MEASURES: Second eye mean absolute error (MAE). RESULTS: Prediction errors of paired eyes were correlated. Interocular corneal power differences exceeding 0.60 diopters (D) were associated with a weaker correlation but interocular AL differences did not affect the correlation. When a 50% CF was applied to second eyes of patients with a first eye PE between ±0.50 and ±1.50 D, it improved refractive outcomes from 30%, 56%, and 92% to 42%, 75%, and 96% within ±0.25 D, ±0.50 D and ±1.00 D, respectively, and reduced the MAE from 0.49 to 0.37 D (P<0.0001). For first eye PE below ±0.50 D, a 50% CF reduced the MAE from 0.32 to 0.30 D (P<0.00001). A 50% CF also reduces second eye MAE for eyes with nonoptimized IOLCs. CONCLUSIONS: A 50% CF reduces second eye PE when either first eye optimized PE is within ±1.50 D or when nonoptimized IOLCs are used. The correlation is weaker when interocular corneal power differences are >0.60 D.

Age-related differences in the elasticity of the human cornea.

PURPOSE: The goal of this study was to determine age-related variation in the elasticity of the human cornea using nondestructive means. METHODS: Organ cultured human corneoscleral buttons were studied. Changes in strain were measured with a radial shearing speckle pattern interferometer after an increase in intraocular pressure from 15.0 to 15.5 mm Hg. Changes in central corneal displacement were calculated by integration, and a bulk corneal Young's modulus was derived by mathematical analysis. RESULTS: Fifty corneas, including 17 pairs, were studied. Donors were aged between 24 and 102 years (mean, 73.1); 29 (58%) specimens were from male donors and 21 from female donors. Young's modulus of the cornea increased with age, with the line of best fit indicating an approximate doubling from 0.27 MPa at age 20 years (95% confidence interval, 0.22-0.31) to 0.52 (0.50-0.54) MPa at age 100 years (R² = 0.70). CONCLUSIONS: The stiffness of the human cornea increases by a factor of approximately two between the ages of 20 and 100 years. This variation is relevant to the algorithms used to predict the response to incisional and ablative refractive surgery and will also affect the formulas used to calculate intraocular pressure by applanation.

Intraocular lens formula constant optimization and partial coherence interferometry biometry: Refractive outcomes in 8108 eyes after cataract surgery.

PURPOSE: To assess the benefits of intraocular lens (IOL)-constant optimization for IOLMaster biometry on refractive outcomes after cataract surgery for all surgeons and individual surgeons, define acceptable levels of error in IOL-constant optimization, and calculate the minimum number of eyes required for IOL-constant optimization. SETTING: Department of Ophthalmology, Gloucestershire Hospitals NHS Foundation Trust, Cheltenham, United Kingdom. DESIGN: Database study. METHODS: Hypothetical prediction errors were retrospectively calculated on prospectively collected data extracted from electronic medical records using manufacturers' and optimized IOL constants with Hoffer Q, Holladay 1, and SRK/T formulas for 2 IOLs. The acceptable IOL-constant optimization error margins, personalized IOL constants for individual surgeons, and minimum sample sizes for IOL-constant optimization were evaluated. RESULTS: Optimization of IOL constants reduced the mean absolute errors from 0.66 diopters (D) and 0.52 D to 0.40 D and 0.42 D for the Sofport AO IOL and Akreos Fit IOL, respectively. The percentage of eyes within ±0.25 D, ±0.50 D, and ±1.00 D of target refraction improved from for both IOL models. The IOL-constant errors exceeding 0.09 for the Hoffer Q, 0.09 for the Holladay 1, and 0.15 for the SRK/T produced inferior outcomes. Differences in personalized IOL constants between most surgeons were clinically insignificant. Calculating IOL constants to within 0.06, 0.06, and 0.10 for the Hoffer Q, Holladay 1, and SRK/T, respectively, required 148 to 257 eyes. CONCLUSIONS: Optimizing IOL constants for IOLMaster biometry substantially improved refractive outcomes, far exceeding any additional benefit of personalizing IOL constants for individual surgeons. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes.

Formula choice: Hoffer Q, Holladay 1, or SRK/T and refractive outcomes in 8108 eyes after cataract surgery with biometry by partial coherence interferometry.

PURPOSE: To assess how intraocular lens (IOL) formula choice affects refractive outcomes after cataract surgery using IOLMaster biometry. SETTING: Department of Ophthalmology, Gloucestershire Hospitals NHS Foundation Trust, Cheltenham, United Kingdom. DESIGN: Database study. METHODS: Hypothetical prediction errors were retrospectively calculated on prospectively collected data from electronic medical records using optimized Hoffer Q, Holladay 1, and SRK/T formulas (Sofport AO and Akreos Fit IOLs) across a range of 0.5 mm or 1.0 mm axial length (AL) subgroups. RESULTS: In short eyes, the Hoffer Q had the lowest mean absolute error (MAE) for ALs from 20.00 to 20.99 mm. The Hoffer Q and Holladay 1 had a lower MAE than the SRK/T for ALs from 21.00 to 21.49 mm. There were no statistically significant differences in MAE for ALs from 21.50 to 21.99 mm. In medium eyes, there were no statistically significant differences in MAE for any IOL formula for ALs from 22.00 to 23.49 mm. For ALs from 23.50 to 25.99 mm, there was a trend toward lower MAEs for the Holladay 1, with statistically significant differences in 2 subgroups. In long eyes, the SRK/T had the lowest MAE, with statistically significant differences for ALs of 27.00 mm or longer. CONCLUSIONS: The Hoffer Q performed best for ALs from 20.00 to 20.99 mm, the Hoffer Q and Holladay 1 for ALs from 21.00 to 21.49 mm, and the SRK/T for ALs of 27.00 mm or longer. Using optimized constants, refractive outcomes of 40%, 75%, and 95% within ±0.25 diopter (D), ±0.50 D, and ±1.00 D, respectively, were achievable. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes.

3D collagen orientation study of the human cornea using X-ray diffraction and femtosecond laser technology.

PURPOSE: To study the distribution and predominant orientations of fibrillar collagen at different depths throughout the entire thickness of the human cornea. This information will form the basis of a full three-dimensional reconstruction of the preferred orientations of corneal lamellae. METHODS: Femtosecond laser technology was used to delaminate the central zones of five human corneas into three separate layers (anterior, mid, and posterior stroma), each with predetermined thicknesses. Wide-angle x-ray diffraction was used to study the gross collagen fibril orientation and distribution within each layer. RESULTS: The middle and posterior parts of the human cornea demonstrated a preferential orthogonal arrangement of collagen fibrils, directed along the superior-inferior and nasal-temporal meridians, with an increase in the number of lamellae toward the periphery. However, the anterior cornea (33% of total corneal thickness) showed no systematic preferred lamellar orientation. CONCLUSIONS: In the posterior two thirds of the human cornea, collagen lies predominantly in the vertical and horizontal meridians (directed toward the four major rectus muscles), whereas collagen in the anterior third of the cornea is more isotropic. The predominantly orthogonal arrangement of collagen in the mid and posterior stroma may help to distribute strain in the cornea by allowing it to withstand the pull of the extraocular muscles, whereas the more isotropic arrangement in the anterior cornea may play an important role in the biomechanics of the cornea by resisting intraocular pressure while at the same time maintaining corneal curvature.

Branch retinal vein occlusion and fluoxetine.

A case of branch retinal vein occlusion associated with fluoxetine-induced secondary hypertension is described. Although an infrequent complication of selective serotonin reuptake inhibitor therapy, it is important that ophthalmologists are aware that these agents can cause hypertension because this class of drugs is widely prescribed.