F. Schirra

Spontaneous bilateral late-onset Descemet membrane detachment after successful cataract surgery.

We report the case of a 68-year-old man who developed bilateral Descemet membrane detachment (DMD) 4 weeks after successful cataract surgery and discuss the possible role of an underlying predisposition to DMD. Surgical intervention with gas injection in the anterior chamber resulted in excellent visual acuity restoration in the patient. To our knowledge, this is the first report of spontaneous bilateral DMD in the late postoperative period after cataract extraction.

Results of excimer laser penetrating keratoplasty in aphakic eyes

BackgroundCorneal grafting in aphakic eyes is often challenging. We report about the outcome of excimer laser trephination in aphakic eyes.MethodsWe examined 17 eyes of 17 patients. Diagnosis in 11 eyes was endothelial decompensation and in six, corneal scars. We performed an excimer laser keratoplasty with intraoperative “Flieringa ring” suturing. Follow-up ranged between 3 and 41 (17.6 ± 11.7) months. Main outcome measures included: best-corrected visual acuity (BCVA), intraocular pressure (IOP), topographic astigmatism, corneal refractive power (CRP), central corneal thickness (CCT) and endothelial cell density (ECD).ResultsPreoperative BCVA was light perception in two eyes, hand motion in seven, finger counting in one eye, under 20/400 in six eyes and 20/200 in one eye. IOP ranged between 4 and 28 (13.6 ± 5.1) mmHg. Topographic astigmatism ranged from 0.5 to 18.5 (7.0 ± 6.9) dioptres. CRP was between 38 and 59 (46 ± 9) dioptres. CCT was between 404 and 1069 (748 ± 181) μm. Postoperative BCVA was hand motion in five eyes, under 20/400 in two and ranged between 20/200 and 20/20 in ten eyes. IOP ranged between 10 and 40 (18.3 ± 8.5) mmHg. Topographic astigmatism ranged from 0.9 to 13 (5.5 ± 3.2) dioptres. CRP was between 31.9 and 46.7 (42 ± 4.1) dioptres. CCT was between 349 and 820 (552 ± 115.57) μm. ECD was between 592 and 2319 (1674 ± 553) cells/mm2.ConclusionsExcimer laser trephination can deliver beneficial visual outcomes in most of the aphakic eyes.

Corneal hysteresis and intraocular pressure in mucopolysaccharidosis I and VI

Editor, F ahnehjelm et al. (2011) have recently presented an interesting case series of patients with mucopolysaccharidosis I (n = 5) and VI (n = 2) (MPS-I and MPS-VI). The authors measured the corneal hysteresis (CH) and corneal resistance factor (CRF) by ocular response analyser (ORA), as well as the intraocular pressure (IOP) by ORA pneumotonometry or Icare-tonometry to investigate the potential impact of the corneal biomechanical profile on IOP. They have documented an increase in CH and CRF in all patients, suggesting that an increase in corneal stiffness is probably responsible for the falsely increased IOP values, which were recorded in these patients. Nevertheless, we would like to emphasize some points which, in our opinion, merit further consideration. All patients with MPS-I had corneal opacification and they were subjected to stem cell transplantation (SCT), which resulted in an improvement in the corneal transparency, according to the authors. Corneal evaluation with the aid of ORA and measurement of IOP was conducted after SCT treatment. As the authors report, the accumulation of glycosaminoglycans (GAGs) in the lysosomes of the corneal keratocytes may not only cause corneal opacity but may also increase the corneal thickness (Kottler et al. 2010). On the other hand, Summers et al. (1989) have reported normal corneal thickness in some patients with MPS-I. However, the authors do not provide any data regarding the central corneal thickness (CCT) of their patients. Was the CCT increased before SCT? What was the CCT at the time of examination (after SCT)? In our opinion, it is important for the authors to specify whether the increase in CH and CRF was an epiphenomenon occurring predominantly because of the increased CCT or a primary phenomenon associated with the altered stromal homeostasis because of the accumulation of GAGs in the lysosomes of corneal keratocytes. We can imagine that improvement in corneal opacification after SCT, as reported by the authors, may have induced a relative normalization of CCT. The evaluation of CCT would enable a valid interpretation of the biomechanical findings providing evidence regarding the nature of the corneal biochemical profile in MPS-I and MPS-VI. Moreover, the authors conclude that increased rigidity of the cornea and the increased thickness of the cornea and sclera may cause an increased stiffness and reduced elasticity in their patients. Glass et al. (2008) have recently described a viscoelastic biomechanical model of the cornea, which illustrates in an extremely convincing manner the impact of viscosity and elasticity upon CH. Corneal hysteresis may increase or decrease with stiffening depending on the behaviour of the viscous material element, which is modified in MPS because of the stromal accumulation of GAGs. High CH may be associated with high elasticity or low elasticity depending on the viscosity; alteration in CH alone has too many undefined degrees of freedom to deliver a valid statement regarding corneal stiffness (Glass et al. 2008). Finally, the authors suggest that all patients in this study had falsely high IOP values, as measured by ORA pneumotonometry, probably due to increased corneal rigidity. The main question which one should address is whether a primary ‘endogenous’ increase in corneal rigidity accounts for the falsely increased IOP or whether the observed false increase in IOP represents the aftermath of a secondary increase in CCT. In our opinion, the consideration of CCT is of paramount importance in the attempt to evaluate in a valid manner the corneal biochemical properties, especially in a corneal model where a metabolic disorder is involved, such as MPS, which increases the complexity of the biomechanical investigation.