Comparison of deep anterior lamellar keratoplasty and penetrating keratoplasty with respect to postoperative corneal sensitivity and tear film function

Purpose

To investigate tear film function, central and peripheral corneal sensitivity and corneal subbasal nerve morphology in the cornea after deep anterior lamellar keratoplasty (DALK) compared with penetrating keratoplasty (PK).

Methods

This prospective study compared the changes in 16 eyes of 16 patients who underwent DALK (DALK group) with those in 28 eyes of 28 patients who underwent PK (PK group). Thirty healthy volunteers were also included as controls. Tear functions were evaluated using tear break-up time (TBUT), tear meniscus height (TMH) and corneal fluorescein staining. Corneal sensation was measured with a Cochet-Bonnet esthesiometer. Corneal subbasal nerve morphology was evaluated using in vivo confocal microscopy (IVCM). The patients were examined 1, 3, 6, 9 and 12 months after keratoplasty.

Results

Postoperatively, TMH recovered significantly faster in the DALK group than in the PK group (p?p?p?p?Conclusions Tear film function was restored more rapidly after DALK compared with PK, but there was no significant difference in corneal sensitivity between PK and DALK.     

Dry eye evaluation and correlation analysis between tear film stability and corneal surface regularity after small incision lenticule extraction

Purpose

To investigate the dry eye after small incision lenticule extraction (SMILE) and explore the correlations between changes in the tear film stability, the tear secretion and the corneal surface regularity.

Methods

Sixty-two eyes of 22 men and 13 women who underwent SMILE were included in this study. Corneal topography was measured to assess the index of surface variance (ISV) and the index of vertical asymmetry (IVA). Dry eye tests including subjective symptom questionnaire, tear breakup time (TBUT), corneal fluorescein staining and Schirmer’s test (ST) were evaluated before and at 1 and 6 months postoperatively.

Results

TBUT was found to be significantly decreased from 9.8 ± 3.4 s preoperatively to 7.4 ± 3.8 s at 1 month and 6.5 ± 3.6 s at 6 months (both P < 0.001). There was a significant decrease in ST at 1 month postoperatively (P = 0.012); however, ST returned to baseline by 6 months (P = 0.522). Both ISV and IVA significantly increased after the surgery (all P < 0.001). In addition, the changes in TBUT were negatively correlated with the increases in ISV and IVA (r = ?0.343, P = 0.006 and r = ?0.311, P = 0.014, respectively).

Conclusions

Patients undergoing SMILE might develop a short-TBUT type of dry eye. Corneal surface regularity indices might be helpful in the assessment of tear film stability following SMILE procedure.

     

激光扫描共焦显微镜对飞秒激光小切口基质透镜取出术后角膜帽神经修复的动态观察

背景 飞秒激光小切口基质透镜取出术(SMILE)术后角膜中央部上皮基底膜下神经纤维丛存在再生的过程,但术后不同时间点角膜上皮基底膜下神经纤维的生长方式及角膜帽缘神经修复的动态变化鲜见报道. 目的 探讨SMILE术后角膜帽神经损伤情况及其修复规律. 方法 对2014年4月至2015年4月于山东医学高等专科学校附属眼科医院接受SMILE手术且按时完成随访的近视患者16例32眼进行回顾性分析.术眼于术前及术后1周、1个月、3个月、6个月进行随访检查,采用激光扫描共焦显微镜对术眼角膜中央部及帽缘切口部位进行0.4 mm×O.4 mm区域的扫描,采用Image-Pro Plus图像分析软件对上皮基底膜下神经纤维丛成像最为清晰的图片进行分析,测定术眼角膜中央每平方毫米范围内图像中神经纤维的总长度,即角膜中央神经纤维密度,并观察帽缘神经纤维分支的修复.结果 术眼术前及术后1周、1个月、3个月、6个月角膜中央神经纤维密度分别为(19 687.45-1 147.59)、(10 500.46±1 056.22)、(12 833.40±1 047.98)、(13 564.04±1 173.01)、(14 661.35±941.92) μm/mm2,手术前后不同时间点总体比较差异有统计学意义(F=319.440,P=0.000).术眼术后角膜神经纤维密度均明显低于术前,手术1个月后随时间推移角膜中央神经纤维密度逐渐增加,各时间点间两两比较差异均有统计学意义(均P＜0.01).术眼术后角膜上皮基底膜下均发现有较丰富的神经纤维丛,形态与术前接近,术后1周角膜帽缘小切口处可见神经纤维的断端及崩解,角膜帽缘非切口处神经纤维越过角膜帽缘伸入角膜帽;术后1个月角膜帽缘切口处可见新生神经芽穿过角膜切口;术后3～6个月角膜帽缘切口处可见明显的神经纤维连续延伸. 结论 SMILE术后部分浅层神经纤维未受到损伤,神经纤维的修复呈从角膜帽外向角膜帽内水平放射状再生的模式;术后角膜帽中央神经纤维密度随时间的延长逐渐增加.     

Corneal nerve alterations in different stages of Fuchs’ endothelial corneal dystrophy: an in vivo confocal microscopy study

Purpose

To analyze potential alterations in corneal nerve morphology and function in different stages of Fuchs’ endothelial corneal dystrophy (FECD).

Methods

Thirty eyes with FECD underwent in vivo confocal microscopy using the Heidelberg Retina Tomograph II (HRT II; Heidelberg Engineering, Heidelberg, Germany) and the Rostock Cornea Module (RCM) to quantify the morphology of the central subbasal corneal nerve plexus (total nerve length, total nerve number, number of main nerve trunks, number of nerve branches) as well as esthesiometry (using the Cochet-Bonnet esthesiometer) of the central cornea to determine central corneal sensation as a measure of nerve function. Findings were correlated with an age-matched control group of 30 healthy individuals. Comparisons to biomicroscopical stage of FECD, visual acuity and central corneal thickness were performed using Spearman correlation.

Results

Depending on slit-lamp examination, all 30 eyes were classified into FECD stage 1–4 (stage 1: six eyes; stage 2: 15 eyes; stage 3: six eyes; stage 4: three eyes). Total nerve length (ρ?=??0.8, p?<?0.001), total nerve number (ρ?=??0.7, p?<?0.001), number of main nerve trunks (ρ?=??0.6, p?<?0.001), and number of nerve branches (ρ?=??0.7, p?<?0.001) decreased significantly with increasing FECD stages. Comparing to the visual acuity, significant positive correlations were found for total nerve length (ρ?=?0.5, p?=?0.012), total nerve number (ρ?=?0.5, p?=?0.005), number of main nerve trunks (ρ?=?0.4, p?=?0.017), and number of nerve branches (ρ?=?0.5, p?=?0.009). With central corneal thickness, there were significant inverse correlations for total nerve length (ρ?=??0.6, p?=?0.001), total nerve number (ρ?=??0.5, p?=?0.012), number of main nerve trunks (ρ?=??0.4, p?=?0.015), and number of nerve branches (ρ?=??0.4, p?=?0.017). Central corneal sensation was full in all FECD stage 1, stage 2 and stage 3 eyes, but mildly reduced in FECD stage 4 eyes.

Conclusions

Increasing severity of Fuchs’ endothelial corneal dystrophy (FECD) is concurrent with marked attenuation of the density, as well as mild diminishment of the function, of the subbasal corneal nerve plexus in late stage of the disease.     

不同角膜屈光手术对基底膜下神经的影响

目的：观察角膜屈光不同术式后基底膜下神经恢复情况。
　　方法：角膜激光共焦显微镜观察术后1 mo 的 LASEK 12眼、LASIK 12眼、FLEx 12眼、SMILE 12眼,并对部分其它术后时段进行了对比观察。
　　结果：术后1 mo SMILE组基底膜下神经均未见明显破坏,走行规律,完整,切口处被切断神经对合良好;LASEK, LASIK和FLEx基底膜下神经仍现不同程度损害,其它时段眼显示随着时间推移,逐渐形成交通支。
　　结论：SMILE手术对基底膜下神经影响小,相对于其他几种角膜屈光手术,在术后神经恢复方面可能有一定优势。     

Corneal nerve regeneration after herpes simplex keratitis: A longitudinal in vivo confocal microscopy study

Purpose

To evaluate the long-term alterations of corneal nerves in patients with herpes simplex virus (HSV) keratitis using in vivo confocal microscopy (IVCM).

Comparison of corneal sensitivity between FS-LASIK and femtosecond lenticule extraction (ReLEx flex) or small-incision lenticule extraction (ReLEx smile) for myopic eyes

Background

To compare the effect on corneal sensitivity between femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) and femtosecond lenticule extraction (ReLEx flex) or FS-LASIK and small-incision lenticule extraction (ReLEx smile) surgery.

Methods

Twenty-seven subjects (54 eyes) underwent FS-LASIK, 22 subjects (40 eyes) underwent ReLEx flex, and 32 subjects (61 eyes) underwent ReLEx smile surgery. Cochet-Bonnet esthesiometry (Luneau Ophthalmologie Chartres, Cedex, France) was used to evaluate corneal sensitivity preoperatively as well as at 1 week and 1 and 3 months after surgery.

Results

At 1 week, central, superior, nasal, and temporal corneal sensitivity in the ReLEx flex group was significantly higher than in the FS-LASIK group (P?=?0.007, 0.004, 0.020, 0.004 respectively) and in the central and inferior areas at 3 months (P?=?0.002, 0.009 respectively). A higher corneal sensitivity after ReLEx smile surgery was observed in every quadrant at 1 week and 1 and 3 months compared with FS-LASIK surgery (P?<?0.01). Furthermore, in the ReLEx smile group, there were no statistical differences in the superior and temporal quadrants at 1 month postoperatively compared with preoperatively (5.19?±?0.61 cm, P?=?0.198 and 5.64?±?0.48 cm, P?=?0.330 respectively) and no significant differences in any quadrant at 3 months.

Conclusions

Postoperative corneal sensitivity was not remarkably changed after ReLEx smile surgery compared with FS-LASIK. This might be because ReLEx is a flapless procedure.     

The effect of hinge location on corneal sensation and dry eye after LASIK: a systematic review and meta-analysis

Background

The aim of this meta-analysis is to investigate the possible effect of hinge location on corneal sensation and dry eye syndrome after laser-assisted in situ keratomileusis (LASIK).

Methods

A comprehensive literature search was conducted in the PubMed, EMBASE, and Cochrane Controlled Trials Register to identify potentially relevant randomized controlled trials (RCTs) of comparing the effects of horizontal-hinge flaps and vertical-hinge flaps on corneal sensation and dry eye after LASIK. Meta-analyses were performed for corneal sensation, tear break-up time (TBUT), Schirmer's I test and corneal fluorescein staining (CFS) at 1 week, 1, 3, and 6 months postoperatively.

Results

Eight RCTs (657 eyes) investigating the effects of hinge location on the corneal sensation and dry eye syndrome after LASIK were identified. The results showed that the horizontal-hinge group causes less loss of sensation than the vertical-hinge group, and the difference was significant at 3-month postoperative (p?=?0.01). The TBUT value was significantly larger and a lower percentage of patients with CFS in the horizontal-hinge group than in the vertical-hinge group at 1-month postoperative (p?=?0.007 and p?=?0.01, respectively) and 3-month (p?=?0.03 and p?=?0.009, respectively); Schirmer's I test values were also higher in the horizontal-hinge group, but the difference did not reach statistically significance at each postoperative period.

Conclusions

According to the available data, we suggest that hinge location may have some effect on corneal sensation and dry eye syndrome after LASIK at the early postoperative period. However, there was no significant difference between the groups at 6 months after surgery. Further well-organized, prospective, randomized studies involving more patients are warranted.     

Are cefuroxime and vancomycin really safe on the corneal endothelial cells?

Purpose

To investigate the biochemical changes of the oxidant/antioxidant balance in corneal tissue, and determine the relative corneal endothelial toxicities of the following intracameral antibiotic agents: cefuroxime and vancomycin.

Methods

The experiment was conducted using New Zealand rabbits. The rabbits were randomly divided into three experimental groups as follows: cefuroxime group (n?=?10), vancomycin group (n?=?10), and control group (n?=?10). Only the right eyes of the rabbits were used in this study. Twenty eyes received injections of 0.1 ml of one of the two antibiotic preparations, and ten control eyes received injections of 0.1 ml of balanced salt solution. Corneal thickness and clarity were measured before, and 3 and 6 h after surgery. The corneal tissues of the rabbits were extracted and homogenized in 2 ml of physiological saline, and kept at ?80ºC. In the corneal tissue, malondialdehyde (MDA) and total thiol (SH) levels were measured with spectrophotometric methods. Friedman and Kruskal–Wallis tests were used for statistical analysis.

Results

Neither cefuroxime nor vancomycin caused corneal thickening and edema at 3 and 6 h after injection, and no anterior chamber reaction was observed in both groups at both measurement times. The level of SH significantly decreased, while the level of MDA significantly increased in the corneal tissue in the cefuroxime group (p?=?0.001 and p?<?0.001 respectively). In contrast, no statistically significant change in oxidative-stress parameters was observed in the vancomycin group (p?=?0.165 and p?=?0.876 respectively).

Conclusions

Corneal endothelial cells are very sensitive to any form of toxic exposure. Using intracameral cefuroxime during the anterior segment surgery may be more toxic on the endothelial tissue in patients with vulnerable corneal endothelium. Because of the definite risk of dosage errors, these agents should be prepared in the hospital pharmacy and not in the operating theatre.     

The impact of tear functions on visual outcome following keratoplasty in eyes with keratoconus

Background

To investigate the impact of preoperative and postoperative tear functions on visual outcome and the recovery of visual function following keratoplasty in eyes with keratoconus.

Methods

Twenty-five eyes of 25 consecutive patients (5 females, 20 males, mean age: 34.3?±?15.8 years (range: 19–70 years) with keratoconus who underwent either penetrating keratoplasty (PKP) or deep anterior lamellar keratoplasty (DALK) were included in this prospective study. One patient who had a rejection episode during the follow-up period was excluded. All subjects underwent best corrected visual acuity (BCVA), corneal topography (refractive cylinder, surface regularity index: SRI and surface asymmetry index: SAI), Schirmer I test, tear film break-up time (BUT), corneal sensitivity, and fluorescein staining score measurements before as well as 1, 3, 6 and 12 months after keratoplasty. The relation between the tear functions and the duration until the achievement of maximum BCVA was also evaluated. Linear regression analysis was performed to study the statistical significance of the correlations and the time wise change of each examined parameter.

Results

SRI, SAI, and BCVA significantly improved after keratoplasty. The postoperative corneal sensitivity was still significantly low even at 12 months postoperatively. Postoperative BCVA at 3, 6 months and maximum BCVA showed a significant linear negative correlation with the preoperative BUT (3 months; r?=??0.461, p?=?0.036, 6 months; r?=??0.494, p?=?0.023, maximum BCVA; r?=??0.473, p?=?0.030). The duration until the achievement of maximum BCVA showed a significant negative correlation with the preoperative Schirmer test (r?=??0.429, p?=?0.036). BCVA at 1 and 3 months postoperatively showed significant linear negative correlations with BUT value at the respective periods (1 month; r?=??0.665, p?=?0.0036, 3 months; r?=??0.580, p?=?0.0059).

Conclusion

Preoperative tear functions appeared to have an influence on postoperative BCVA and the duration of visual recovery in keratoconus patients undergoing keratoplasty. Postoperative tear film stability appears to play an important role for obtaining a better BCVA in the early postoperative period after keratoplasty.     

One-year refractive results,contrast sensitivity,high-order aberrations and complications after myopic small-incision lenticule extraction (ReLEx SMILE)

Background

To report one year results of the first cohort of routine refractive lenticule extraction through a small incision (ReLEx SMILE) for correction of myopia and myopic astigmatism.

Methods

Fifty-four eyes of 27 patients with spherical equivalent of ?4.68?±?1.29D who underwent routine ReLEx SMILE by a single surgeon were prospectively followed-up for 1 year. We used the VisuMax® femtosecond laser system (Carl Zeiss Meditec AG, Germany) with a 500 kHz repetition rate. Folow-up intervals were at 1 day, 1 week, 1, 3, 6, and 12 months after surgery. We obtained following parameters: uncorrected (UDVA) and distance-corrected visual acuity (CDVA), contrast sensitivity, and wave front measurements. We also recorded all complications.

Results

Because of suction loss in one eye, 12-month results were obtained in 53 eyes as follows. After 1 year, 88 % of eyes with plano target had an UDVA of 20/20 or better. Twelve percent of eyes lost 1 line of CDVA, while 31 % gained 1 line and 3 % gained 2 lines. The mean SE after 1 year was ?0.19?±?0.19. The mean refraction change between month 1 and 12 was 0.08 D. Neither mesopic nor photopic contrast sensitivity showed any significant changes. The high-order aberrations (HOA) increased from 0.17 to 0.27 μm (Malacara notation). No visually threatening complications were observed.

Conclusion

In this first cohort, ReLEx® SMILE produced satisfactory refractive outcomes with moderate induction of HOA and unaffected contrast sensitivity after 1 year.     

Evaluation of rigid gas permeable lens fitting in keratoconic patients with optical coherence tomography

Purpose

To assess fitting of rigid gas permeable (RGP) lenses in patients with keratoconus, using spectral domain optical coherence tomography (SD-OCT).

Methods

The study was conducted on 30 eyes of 30 keratoconic patients fitted with RGP lenses, namely Rose K2 lens. Biomicroscopic examination with and without RGP lens was done. Fluorescein pattern was examined to determine the fitting, if ideal (three-point light touch), steep (central fluorescein pooling) or flat (central heavy bearing touch). Post-lens tear film thickness was measured centrally and at the lens edges using SD-OCT. Patient’s comfort was assessed and graded.

Results

Mean central post-lens tear film thickness was 35.1?±?7.3 μ in patients with ideal fitting. Mean post-lens tear film thickness of 50.4?±?8.2 μ and 25.3?±?6.1 μ was noted in patients with steep and flat fitting, respectively. Mean post-lens tear film thickness of 102.5?±?12.1 μ, 85.4?±?11.4 μ, 135.6?±?13.3 μ was demonstrated in eyes with ideal, steep and flat edge lift, respectively. Tear film thickness under the edges was significantly (p?=?0.04) lower in patients unsatisfied with their contact lenses.

Conclusion

SD-OCT can image and measure the tear film thickness in keratoconic patients with different fitting patterns of RGP lenses. OCT- guided fitting can be used to evaluate and modify the lens parameters to increase patient satisfaction. Lens intolerance may be related to edge lift rather than central fitting.     

In vivo confocal microscopy detects bilateral changes of corneal immune cells and nerves in unilateral herpes zoster ophthalmicus

Purpose

To analyze bilateral corneal immune cell and nerve alterations in patients with unilateral herpes zoster ophthalmicus (HZO) by laser in vivo confocal microscopy (IVCM) and their correlation with corneal sensation and clinical findings.

Corneal biochemical features of patients with vernal keratoconjunctivitis

Background

Vernal keratoconjunctivitis (VKC) is a chronic, bilateral, seasonally exacerbated, allergic inflammation of the ocular surface, involving bulbar and ? or tarsal conjunctiva and cornea. The ocular response analyzer (ORA) measures corneal biomechanical properties in vivo by monitoring and analyzing the corneal behavior when its structure is submitted to a force induced by an air jet. This study was designed to examine corneal biomechanical properties and intraocular pressure in patients with VKC, and to compare with control eyes.

Methods

ORA measurements were performed on the both eyes of 26 patients with VKC (group I) and 14 healthy children who served as the control group (group II). Corneal hysteresis (CH), corneal resistance factor (CRF) and intraocular pressure [Goldmann correlated (IOPg) and corneal compensated (IOPcc)] were recorded with ORA.

Results

Mean age of patients with VKC and control groups were 11.3?±?5.8 and 10.6?±?1.9 years for groups I and II respectively. Mean (± SD) of the CH and CRF readings were 10.1?±?1.6 versus 10.5 ±1.6 (p?>?0.05) and 9.5?±?1.7 versus 10.8?±?1.7 mmHg (p?<?0.05), in groups I and II respectively. Mean (± SD) of the IOPg and IOPcc recordings were 13.3 ±3.4 versus 16.6 ±3.6 mmHg (p?<?0.05) and 14.3?±?3.4 versus 16.9?±?3.7 mmHg (p?>?0.05) in groups I and II respectively. Statistical analysis revealed significant differences for CRF and IOPg between the study groups.

Conclusion

The mean CRF and IOPg values of patients with VKC were lower than those of controls. According to the results of our study, one can conclude that corneal biomechanical property, CRF, could be different in VKC patients compared to normals.     

Subbasal nerve regeneration after LASEK measured by confocal microscopy

PURPOSE: To determine the relationship between the degree of subbasal nerve regeneration and corneal sensation and tear film functions after LASEK using corneal confocal microscopy. METHODS: This prospective, observational, and longitudinal study included 35 LASEK patients who underwent tear breakup time assessment, phenol red thread test, corneal esthesiometry, and confocal microscopy preoperatively and 1, 3, and 6 months postoperatively. Subbasal nerve images were analyzed to assess nerve regeneration. RESULTS: Postoperatively, tear breakup time decreased significantly and had not returned to the preoperative level by 6 months after surgery. There were no significant differences in the phenol red thread test results before and after LASEK. Central corneal sensation decreased significantly 1 month after LASEK and returned to normal levels 3 months after surgery. Nerve fiber density, nerve branch density, and nerve fiber length and width decreased significantly after LASEK and had not returned to preoperative levels 6 months after surgery. Subbasal nerve fibers retained their vertical orientation after LASEK. There were no significant correlations between the length and density of subbasal nerve fibers and central corneal sensitivity, tear volume, or breakup time after surgery. CONCLUSIONS: Subbasal nerves were injured by LASEK and had not returned to preoperative levels 6 months after surgery. Corneal sensitivity was reduced after LASEK and returned to normal levels 3 months after surgery.     

Changes in corneal subbasal nerve morphology and sensitivity during orthokeratology: Recovery of change

Purpose

To investigate the recovery of orthokeratology (OK)-induced changes in corneal nerve morphology and sensitivity following lens wear discontinuation, over a 3-month period.

Corneal Nerve and Epithelial Cell Alterations in Corneal Allodynia: An In Vivo Confocal Microscopy Case Series

Purpose

To investigate morphological changes of the corneal epithelium and subbasal nerves in patients with corneal allodynia using in vivo confocal microscopy (IVCM).

Analysis of internal astigmatism and higher order aberrations in eyes implanted with a new diffractive multifocal toric intraocular lens

Background

To evaluate the intraocular lens (IOL) position by analyzing the postoperative axis of internal astigmatism as well as the higher-order aberration (HOA) profile after cataract surgery following the implantation of a diffractive multifocal toric IOL

Methods

Prospective study including 51 eyes with corneal astigmatism of 1.25D or higher of 29 patients with ages ranging between 20 and 61 years old. All cases underwent uneventful cataract surgery with implantation of the AT LISA 909 M toric IOL (Zeiss). Visual, refractive and corneal topograpy changes were evaluated during a 12-month follow-up. In addition, the axis of internal astigmatism as well as ocular, corneal, and internal HOA (5-mm pupil) were evaluated postoperatively by means of an integrated aberrometer (OPD Scan II, Nidek).

Results

A significant improvement in uncorrected distance and near visual acuities (p?<?0.01) was found, which was consistent with a significant correction of manifest astigmatism (p?<?0.01). No significant changes were observed in corneal astigmatism (p?=?0.32). With regard to IOL alignment, the difference between the axes of postoperative internal and preoperative corneal astigmatisms was close to perpendicularity (12 months, 87.16°?±?7.14), without significant changes during the first 6 months (p?≥?0.46). Small but significant changes were detected afterwards (p?=?0.01). Additionally, this angular difference correlated with the postoperative magnitude of manifest cylinder (r?=?0.31, p?=?0.03). Minimal contribution of intraocular optics to the global magnitude of HOA was observed.

Conclusions

The diffractive multifocal toric IOL evaluated is able to provide a predictable astigmatic correction with apparent excellent levels of optical quality during the first year after implantation.     

Corneal biomechanical properties measured by the ocular response analyzer in acromegalic patients

Purpose

To investigate the effect of acromegaly on corneal biomechanical parameters.

Methods

This cross-sectional, comparative clinical study included 34 acromegalic patients and 30 age-matched and sex-matched healthy controls. Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated and corneal-compensated intraocular pressure (IOPg and IOPcc, respectively) were measured using the Ocular Response Analyzer. Central corneal thickness (CCT) was determined with the ultrasonic pachymeter.

Results

The mean duration of disease for the acromegalic patients was 5.3 years. There was no significant difference between the groups regarding mean CH, CRF, IOPg and IOPcc values. The respective mean values in patients with acromegaly and controls were 10.3?±?2.2 and 9.5?±?1.5 mmHg (p?=?0.13) for CH; 10.5?±?2.4 and 9.7?±?1.7 mmHg (p?=?0.16) for CRF, 16.1?±?3.6 and 15.5?±?2.9 mmHg (p?=?0.49) for IOPg, 16.8?±?3.4 and 17.0?±?2.8 mmHg (p?=?0.82) for IOPcc, and 544.8?±?32.2 and 530.7?±?22.9 μm (p?=?0.05) for CCT. A significant moderate correlation was detected between the duration of acromegaly and IOPg OD (r?=?0.430, p?=?0.01). There was no significant correlation between other ocular parameters and levels of GH and IGF-1 at the time of diagnosis, the status of control, adenoma type, radiotherapy treatment, and drug usage.

Conclusions

In acromegalic patients, the duration of disease was correlated with IOPg OD level. Corneal biomechanical parameters and CCT values were not significantly different than those in age-matched and sex-matched healthy individuals.     

In vitro effect of corneal collagen cross-linking on corneal hydration properties and stiffness

Background

The purpose of this study is to evaluate in-vitro the immediate effect of corneal collagen cross-linking (CXL) on corneal hydration and stiffness.

Methods

Forty-two corneal buttons from freshly enucleated porcine eyes were immersed in riboflavin 0.1% in dextran 20% dilution for 3 h in order for their hydration to reach equilibrium. Corneal buttons where divided into two groups; the first group was stored in dark conditions while the other group was irradiated with UV radiation (370 nm) for 30 min to simulate CXL according to the clinically applied protocol. After irradiation, all corneas were immersed in dextran 20% solution for 3 additional hours. Subsequently, each button underwent weighing, thickness measurement, and was mounted in a special device for the measurement of force versus deformation by compression. Finally, all corneal buttons were dehydrated for 48 h in a desiccating oven set at 62 °C and weighed again to obtain their dry mass. Hydration (%) of each button was calculated.

Results

Mean corneal hydration in the irradiated and the non-irradiated group of corneas was 69.8 and 72.2%, respectively (p?<?0.001). Differences in thickness and compressibility were not statistically significant. Thickness and hydration were positively correlated (Pearson’s r?=?0.714, p?<?0.001).

Conclusions

CXL causes corneal dehydration that can be detected immediately after the procedure. This phenomenon may contribute to increased mechanical stiffness of the cornea. A change in stiffness by means of compressibility could not be detected in porcine corneas.