Brittle cornea syndrome: A tale of three brothers

Brittle cornea syndrome (BCS) is a genetic connective tissue disorder with discernible ocular features such as blue scleral and thin cornea that predominantly presents in younger children. We herein describe cases of three siblings with BCS, two of whom presented to us with open globe injuries following trivial trauma. Clinical examination of the other eye in both showed diffusely thin corneas and blue sclera. A systemic evaluation revealed sensorineural hearing loss and hyperextensible joints. The third sibling was screened and found to have features concurrent with BCS. This report highlights the challenges faced in the management of ocular injuries and consecutive complications in these patient

Application of hypotonic riboflavin in corneal crosslinking in patients with keratoconus / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM:To compare the results of corneal cross-linking(CXL)with isotonic(IR)and hypotonic riboflavin(HR)in patients with keratoconus.<p>METHODS: Retrospective study of 29 eyes/keratoconus patients submitted to CXL, 15 eyes with application of IR(IR group)and 14 eyes with application of HR(HR group). The parameters analysed included(1-year follow-up): best corrected visual acuity(BCVA), sphere and cylinder, central and finer pachymetry, mean and maximum keratometry(Km and Kmax respectively), complications and progression.<p>RESULTS: An increase on the BCVA scale(LogMAR, logarithm of the minimal angle of resolution)was observed in the two groups: 0.26±0.57(IR)and 0.47±0.72(HR)before treatment, and 0.13±0.79(IR)and 0.29±1.52(HR)at the 1y. Only at 1y, the difference was statistically significant(<i>P</i>=0.018, group IR with higher BCVA). The central pachymetry(μm)decreased at 1mo in both groups, and increased in the following months: 497±28 μm(IR)and 432±14 μm(HR)before treatment, and 480±31 μm(IR)and 424±15 μm(HR)to the 1y. The thinner pachymetry(μm)presented the same evolution: 487±29 μm(IR)and 410±20 μm(HR)before treatment, and 468±33 μm(IR)and 413±13μm(HR)at 1y. Km and Kmax decreased in both groups(<i>P</i>>0.05). 6 eyes from each group presented transitory haze. No eye progressed to the 1y.<p>CONCLUSION:The use of hypotonic riboflavin seems to be a valid alternative for performing the traditional corneal cross-linking technique in eyes with a central corneal thickness of <400 μm.

Current concepts in crosslinking thin corneas

Corneal cross-linking (CXL), introduced by Wollensak et al. in 2003, is a minimally invasive procedure to halt the progression of keratoconus. Conventional CXL is recommended in eyes with corneal thickness of at least 400 microns after de-epithelialization to prevent endothelial toxicity. However, most of the keratoconic corneas requiring CXL may not fulfill this preoperative inclusion criterion. Moderate-to-advanced cases are often found to have a pachymetry less than this threshold. There are various modifications to the conventional method to circumvent this issue of CXL thin corneas while avoiding the possible complications. This review is an update on the modifications of conventional CXL for thin corneas.

Collagen cross-linking in thin corneas.

Collagen cross-linking (CXL) has become the standard of care for progressive keratoconus, after numerous clinical studies have established its efficacy and safety in suitably selected eyes. The standard protocol is applicable in eyes which have a minimum corneal thickness of 400 μm after epithelial debridement. This prerequisite was stipulated to protect the corneal endothelium and intraocular tissues from the deleterious effect of ultraviolet-A (UVA) radiation. However, patients with keratoconus often present with corneal thickness of less than 400 μm and could have otherwise benefited from this procedure. A few modifications of the standard procedure have been suggested to benefit these patients without a compromise in safety. Transepithelial cross-linking, pachymetry-guided epithelial debridement before cross-linking, and the use of hypoosmolar riboflavin are some of the techniques that have been attempted. Although clinical data is limited at the present time, these techniques are worth considering in patients with thin corneas. Further studies are needed to scientifically establish their efficacy and safety.

Advanced Surface Ablation-Photorefractive Keratectomy (ASA-PRK): Safety and Clinical Outcome for the Correction of Mild to Moderate Myopia with a Thin Cornea

PURPOSE: To evaluate the safety, clinical outcome, and change in higher-order wavefront aberrations (HOAs) of Advanced Surface Ablation-Photorefractive Keratectomy (ASA-PRK) for the correction of mild to moderate myopia in cases with a thin cornea. METHODS: ASA-PRK was performed, using a rotary epithelial scrubber, post-laser chilled BSS(R) irrigation, and bandage contact lens, in 127 eyes of 70 patients who had a preoperative spherical equivalent within -7.0 D and who were followed-up for more than six months. The patients were divided into two groups, according to their central corneal thickness (CCT), by ultrasonic pachymetry (Group: CCT520 micrometer, 95 eyes, mean 552.3+/-24.8 micrometer). The clinical outcomes of Group I and II were compared. RESULTS: At six months, 100% of Group I (32/32 eyes) and 93.7% of Group II (89/95 eyes) had an UCVA of 1.0 or better (p>0.05). At six months, a spherical equivalent within 0.5 D of emmetropia was observed in 100% (32/32) of the eyes in Group I and in 94.7% (90/95) of the eyes in Group II (p>0.05). At the 12-month follow-up, all eyes showed good stability of the refractive errors, and none showed corneal haze of grade 1 or more, loss of two or more lines of BSCVA, or serious iatrogenic keratectasia. The magnitude of total HOAs, spherical ablation, and coma were significantly higher six and 12 months after surgery in both groups (p0.05). CONCLUSIONS: ASA-PRK performed on patients with mild to moderate myopia and a thin cornea (> or =490 micrometer) showed a high level of efficacy, predictability, stability, and safety. There was no statistically significant difference in surgically induced HOAs between Groups I and II. The authors suggest that ASA-PRK be used for the correction of mild to moderate myopia, especially in cases with a thin cornea. Further study will be needed to determine the safety of this procedure for thinner corneas in surface keratorefractive surgery.

Simultaneous LASIK on both Stromal Surface and Flap Undersurface for High Myopia with Insufficient Corneal Bed

PURPOSE: To develop a newly modified technique, which is simultaneous laser in situ keratomileusis on both corneal flap undersurface (LASIK-Flap) and the corneal stromal surface, in eyes with insufficient corneal bed of high myopia and thin cornea. METHODS: We performed simultaneous laser in situ keratomileusis on both corneal flap undersurface (LASIK-Flap) and the corneal stromal surface in 38 eyes of 22 patients with high myopia (ranged from SE -4.00D to -14.25D)and corneal thickness (ranged from 435 to 570 micro meter) . In these eyes, all procedures of 130 ~ 160 micro meter thickness of the flap preparation with hinge were successfully made with a use of the Moria M2 microkeratome. The ablation on both the corneal surface and the flap undersurface using VISX star S4 with active track was performed with a plan of postoperative residual corneal stromal bed >250micro meter. We evaluated the changes of visual acuity, refractive error, pachymetry, corneal topography and mesotest for at least 6 months after surgery. Preservation of normal wet state on the flap in very important in procedures. RESULTS: Mean SE was -9.32 +/- 2.75D and mean corneal thickness was 513.37 +/- 36.96 micro meter ranged from 435 micro meter to 570 micro meter before LASIK. Ablation depth of flap undersurface was 48.87 +/- 26.67 micro meter ranged from 6 micro meter to 100 micro meter, and post LASIK spherical equivalent was +0.02 +/- 0.62D (ranged +2.50 ~ -1.50D). No vision concerned complication was found. Follow-up was ranged from 1week to 6 months. CONCLUSIONS: LASIK-flap procedure has an advantage in eyes with insufficient corneal thickness in high myopia.

Accuracy of Corneal Thickness Measurement with Ultrasound Pachymeter in Thin Corneas

PURPOSE: Accurate assessment of corneal thickness is important in order to prevent iatrogenic corneal ectasia after laser in situ keratomileusis (LASIK). More accurate measurement is needed in LASIK enhancement because the cornea becomes thin after previous refractive surgery. We evaluated the reliability of corneal thickness measurement with ultrasound pachymeter (USP) in the thin corneas. METHODS: The corneal thickness was measured in the 22 eyes of 11 rabbits. The corneal flap was made with an Automated Corneal Shaper microkeratome (Bausch and Lomb, USA) with 130 micro meter plate and the flap was removed in order to make the cornea thin. Residual stromal bed (RSB) thickness was measured with USP and thickness gauge, and the two measurements were compared. RESULTS: Mean corneal thickness was 404.69 +/- 11.01 micro meter with USP and 133.23 +/- 15.66 micro meter with thickness gauge. RSB thickness measured with thickness gauge was 269.05 +/- 24.19 micro meter and this was not significantly different from the expected RSB thickness, although RSB thickness measured with USP was 388.14 +/- 10.17 micro meter, which was significantly different from the expected RSB thickness (p=0.00). CONCLUSIONS: In the thin corneas, corneal thickness measurement with ultrasound pachymeter is not reliable.