Pellucid marginal corneal degeneration*1

Endothelium sparing - Air-assisted wedge resection for the treatment of pellucid marginal degeneration

To describe the surgical technique of performing a wedge resection of a 1 mm area of inferior corneal stroma using stromal air injection assisted separation sparring the endothelium in a patient with bilateral Pellucid Marginal Degeneration. 68-year-old male Caucasian advanced, non progressive. A 30G needle on a 1 ml air-filled syringe injects air into the stromal lamellae with the bevel up, leading to stromal emphysema. An MVR blade is used to incise the marked area until clear corneal tissue is seen. The incised areas are separated with a lamellar dissector, and the crescentic area is excised. The lips of the wound are approximated with 10-0 Prolene sutures. This surgical approach leads to adequate management of the Pellucid Marginal Degeneration without injury to the endothelium, ensuring reduced antigenic input and maintenance of the architectural integrity of the eye.

Application of a Revised Tissue Saving Protocol for Combined Topography-Guided Photorefractive Keratectomy and Cross-Linking in a Cohort Having Pellucid Marginal Degeneration

Purpose

To evaluate the efficiency, safety, and stability of a revised tissue-saving treatment protocol in a cohort having pellucid marginal degeneration (PMD).

Methods

A retrospective cohort study was conducted on patients with PMD and no previous treatments. A revised protocol of topo-guided photorefractive keratectomy to be followed by customized phototherapeutic keratectomy and then corneal crosslinking was evaluated by comparing the pre and postoperative outcomes regarding visual (subjective refraction) and topographic (using data from Sirius CSO topography software) outcomes.

Results

There were both statistically significant and clinically relevant improvements in the postoperative parameters, where each of the unaided and corrected visual acuity, spherical equivalent, refractive cylinder, K readings, topographic cylinder, inferior minus superior difference at the 2- and 4- mm diameters, coma aberration, and higher order aberrations were significantly better postoperatively (all p values were less than 0.01, except for maximum k readings where the p-value was 0.017). The safety and efficacy indices for the surgical procedure were remarkably high (1.53 ± 0.70 and 0.90 ± 0.32, respectively).

Conclusion

Our proposed tissue-saving protocol (which showed satisfactory results in keratoconus cases according to a previously published article by our research team) has proven its successful outcomes (both topographically and visually) in cases of PMD, which is a rare ectatic entity with guarded prognosis using the available conventional ectasia treatment modalities.

Corneal Hydrops - Aetiology and Advanced Therapeutic Strategies

Acute hydrops refers to sudden corneal edema caused by rupture of Descemet's membrane (DM) - often in progressive keratectasia. It leads to a sudden decrease in visual acuity, pain, and foreign body sensation as well as an increased glare sensation. Acute hydrops usually heals with scarring within months, but complications such as corneal perforation, infectious keratitis, and corneal vascularization may occur. The prevalence in keratoconus patients is 2.6 to 2.8%. Risk factors include keratoconjunctivitis vernalis, atopic dermatitis, high keratometry, male gender, and eye rubbing. Keratoplasty should be avoided in the acute phase. The prognosis of the graft is reduced, and after scar healing of the hydrops, wearing contact lenses or glasses may be possible again. Conservative therapy alone with lubricants and hyperosmolar eye drops, prophylactic antibiotic eye drops to prevent superinfection, and topical steroids was long considered the only possible form of treatment. However, healing under conservative therapy takes an average of over 100 days. In the meantime, there are different surgical strategies that rapidly shorten the healing and thus the recovery phase of the patients to a few days. If the DM is detached without tension, a simple injection of gas into the anterior chamber can already lead to reattachment and thus to almost immediate deswelling of the cornea. If the DM is under tension, predescemetal sutures combined with a gas injection into the anterior chamber can flatten the cornea and reattach the DM. Mini-Descemet membrane endothelial keratoplasty (mini-DMEK) allows for sutureless closure of the DM defect by transplantation of a small (< 5 mm) graft. In cases of particularly large DM tears and very pronounced hydrops, suture loosening and relapse may occur after the placement of predescemetal sutures. Mini-DMEK can then lead to permanent healing, but in contrast to simple corneal sutures, it is usually performed under general anesthesia and by aid of intraoperative optical coherence tomography. The very good results with regard to the rapid healing prove that surgical therapy makes sense in the vast majority of patients with acute hydrops and should be initiated quickly.

Perforation in interstitial keratitis associated with hidradenitis suppurativa: medical and surgical management

We present a case of bilateral interstitial keratitis leading to perforation in a woman with hidradenitis suppurativa (HS). A woman in her mid-20s with a history of HS and Grave's disease was referred to the corneal service with loss of vision and pain in both eyes since childhood. She was found to have circumferential thinning and steepening affecting her peripheral cornea bilaterally. Corrected distance visual acuity with spectacles was in the right eye 6/7.5, and in the left 6/30, with local thinnest area of 209 and 217 µm in the right and left eyes, respectively. She experienced recurring episodes of redness and irritation, and perforation occurred. The corneal perforation was managed with cyanoacrylate glueing, followed by a local conjunctival flap. Systemic immunosuppression with mycophenolate mofetil and adalimumab was commenced, with improvement after 18 months of treatment. Dermatologists and ophthalmologists should be aware of this association given its potential severity.

Demographic, clinical and tomographic characteristics of pellucid marginal degeneration patients in South Egyptian population

Purpose

To retrospectively evaluate the demographic, clinical, and tomographic characteristics of pellucid marginal degeneration (PMD) patients in South Egypt.

Methods

This study was retrospective cross-sectional, including all patients who attended and sought refractive surgery at Sohag Center for Corneal and Refractive Surgeries, Sohag, South Egypt, between October 2016 and October 2020, and had a diagnosis of PMD. It included cases of PMD at different stages. Cases with PMD were diagnosed by the two authors (experienced in corneal refractive surgery), combining both slit-lamp biomicroscopy findings and corneal tomography.

Results

Out of the 2534 patients attending the Sohag Center for Corneal and Refractive Surgeries (between October 2016 and May 2020) seeking correction of their refractive errors, 24 patients were found to fit in the diagnosis of PMD. Forty-three eyes of the 24 patients were diagnosed with PMD. The topographic patterns ranged from horizontal bow tie (against the rule astigmatism) being the least presenting, followed by crab claw, then butterfly pattern.

Conclusion

PMD is a separate entity of the ectatic corneal spectrum that can easily be misinterpreted as Keratoconus. Topographic and tomographic patterns cannot solely diagnose PMD as they should be enforced by slit-lamp findings.

Pellucid marginal corneal degeneration in a teenager

A teenage boy presented to the clinic complaining of poor vision in both eyes. His best-corrected visual acuity was 20/25. The slit lamp examination revealed vertically oval corneas, crescentic peripheral inferior corneal thinning and ectasia in both eyes. Corneal topography showed against-the-rule astigmatism with mean keratometry (Km) of 45.1 and 45.2 dioptres in the right and left eyes, respectively. High-resolution optical coherence tomography corroborated the clinical findings, and the patient was diagnosed with pellucid marginal corneal degeneration (PMD). Collagen cross-linking was performed in the right eye. Left eye cross-linking is awaited. Although PMD is typically seen in middle-aged (third-fourth decade) patients, it can also occur at earlier ages. Collagen cross-linking can be considered to prevent the progression of the condition.

Prevalence of Corneal Topographic Patterns in Ectatic Corneal Diseases

SIGNIFICANCE

The article highlights various topographic patterns and their prevalence in a large spectrum of ectatic corneal diseases (ECDs). Knowledge of these patterns can help clinicians for quicker diagnosis and selection of appropriate contact lens design.

PURPOSE

This study aimed to determine various corneal topography patterns and their prevalence in patients with ECDs who visited a tertiary eye hospital in western India.

METHODS

Keratoconus, pellucid marginal degeneration, keratoglobus, and post-refractive surgery progressive corneal ectasia are considered under ECDs. This cross-sectional retrospective study reviewed records of 632 consecutive patients with clinical ECDs at their first presentation. The right eye was considered for pattern analysis. In cases with suspected or forme fruste ectasia in the right eye, the fellow eye was considered. A sagittal map with standard scale of Atlas 9000 topographer (Carl Zeiss Meditec AG, Jena, Germany) was used for pattern analysis. They were classified into 18 categories and grouped under five groups. The prevalence of these patterns was calculated and assessed with 95% confidence interval (CI).

RESULTS

The mean ± SD age of patients was 23.6 ± 8.2 years. The highest prevalence was of asymmetric patterns (39.6% [95% CI, 35.7 to 43.5%]; asymmetric bowtie [AB] with steepest radial axis index [SRAX], 18.8%; AB with inferior steep, 16.0%; AB with superior steep [SS], 3.2%; symmetric bowtie with SRAX, 1.6%) and of central or paracentral patterns (28.6% [95% CI, 25.1 to 32.3%]; inferior steep, 12.2%; heart, 7.4%; oval, 4.1%; symmetric bowtie, 2.4%; round, 1.6%; irregular, 0.9%) followed by advanced patterns (17.3% [95% CI, 14.4 to 20.4%; nonmeasurable, 5.4%; globus, 4.9%; indiscriminate, 7.0%). The peripheral patterns were 11.7% (95% CI, 9.3 to 14.4%) (claw, 6.3%; junctional, 3.2%; butterfly, 1.9%; SS, 0.3%). Rare patterns were 2.8% (95% CI, 1.7 to 4.5%) (superior [junctional, claw, and heart], AB with SS with SRAX, and AB with SRAX located temporally).

CONCLUSIONS

Asymmetric and central or paracentral are the most common patterns in our study. The higher prevalence of advanced patterns indicates the need for earlier diagnosis of ECDs in our population. The peripheral patterns also have significant prevalence.

Outcomes of a Single-Segment Intrastromal Corneal Ring in Early Keratoconus and Early Pellucid Marginal Degeneration

PURPOSE

To determine the effect of a single-segment intrastromal corneal ring segment (ICRS; Intacs SK) on early keratoconus (KCN) and pellucid marginal degeneration (PMD).

METHODS

It is a prospective interventional study. One hundred twenty-four eyes (99 patients) with KCN and 36 eyes (26 patients) with PMD at early stage (the maximum keratometric reading less than 55 diopters) were included to ICRS implantation using femtosecond laser at a tertiary university-based hospital and a private outpatient center. The uncorrected distance and spectacle-corrected visual acuity (UDVA and SCDVA), manifest spherical and cylindrical refractions, and keratometry indices were measured preoperatively and postoperatively, 1 week, 2 and 6 months.

RESULTS

One week after surgery, significant improvements were observed in UDVA, SCDVA, cylinder and keratometry readings of both KCN and PMD groups (all P < 0.05) with no significant changes afterward. No significant change occurred in the sphere refraction of PMD group (P = 0.10) in contrast to KCN group (P < 0.001). Corneal irregularity of KCN group in central 3 and 5 mm zones increased at 1 week (both P < 0.001) and then started to decrease up to 6 months. However, the corneal irregularity of PMD group had significant reduction only at 1 week in 5-mm zone (P = 0.02) and 2 months in 3-mm zone (P = 0.01) postoperatively. The final efficacy indexes were 1.44 ± 0.71 and 0.87 ± 0.40 in KCN and PMD groups, respectively.

CONCLUSION

Visual acuity, refractive errors and keratometry values have been improved after one-segment Intacs SK implantation in early KCN and PMD patients.

Corneal cross-linking in pellucid marginal degeneration: Evaluation after five years

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Methods:

Results:

Conclusion:

Clinical profile and demographic distribution of pellucid marginal corneal degeneration in India: A study of 559 patients

Purpose:

The aim of this study was to describe the clinical profile and demographic distribution of pellucid marginal corneal degeneration (PMD) in patients presenting to a multitier ophthalmology hospital network in India.

Methods:

This cross-sectional hospital-based study included 2,470,793 new patients presenting between September 2012 and September 2020 (~8 years period). Patients with a clinical diagnosis of PMD in at least one eye were included as cases. The data were collected using an electronic medical record system.

Results:

Overall, 559 (0.02%) new patients were diagnosed with PMD. The prevalence rates were 0.004% in children (age <16 years) and 0.03% in adults. The majority of patients were males (70.13%) with the bilateral affliction (77.1%). The mean age of the patients was 37.91 ± 13.19 years. The majority (30.23%) of the patients were between 31 and 40 years of age. A significant number of patients were from higher socioeconomic status (93.74%) and from the urban region (45.08%). Of the 990 eyes, the most common clinical signs were ectasia/thinning (58.99%), corneal scar (17.47%), and corneal hydrops (1.01%). The majority of the eyes (87.97%) were managed with either spectacles or contact lenses. Among those who had surgical intervention, collagen cross-linking was the most performed procedure (5.25%) followed by cataract surgery (4.14%).

Conclusion:

PMD is a rare disease affecting patients seeking eye care in India. It commonly affects adult males and is bilateral in nature. The disease progression is slow and usually occurs beyond 3 years. Conservative management is more common than surgical intervention.

Different mRNA expression patterns in keratoglobus and pellucid marginal degeneration keratocytes

PURPOSE

Alike keratoconus (KC), keratoglobus (KG) and pellucid marginal degeneration (PMD) belong to ectatic corneal diseases. While there are numerous studies on keratoconus pathophysiology, there is no exact knowledge on genetic and pathophysiological background of KG and PMD, so far. It is not yet clarified, whether KG and PMD are independent clinical entities or represent different stages of the same disease. Our purpose was to investigate key parameters concerning collagen synthesis, intracellular LOX expression and inflammation in corneal stromal cells of KG and PMD subjects, in vitro.

METHODS

Normal human keratocytes of corneas from the LIONS Cornea Bank Saar-Lor-Lux, Trier/Westpfalz and human keratocytes of KG and PMD patients were isolated and cultured as keratocytes. To examine Collagen I and V (Col I, Col V), heat shock protein 47 (Hsp47), Lysyl Oxidase (LOX), nuclear factor kappa B (NF-κB) mRNA and protein expression in all cell types, quantitative PCR and Western blot analysis has been performed.

RESULTS

Col5A1 mRNA expression was significantly lower in KG and PMD keratocytes and LOX mRNA expression was significantly higher in KG-keratocytes, compared to controls. Col1A1, Hsp47 and NF-κB mRNA expression and the analyzed protein expressions did not differ from controls, in KG or PMD.

CONCLUSIONS

Col5A1 mRNA expression is decreased in KG and PMD and LOX mRNA expression is increased in KG. Therefore, the pathophysiology of KG and PMD differs from KC and these seem to be from KC independent entities. The explanation of the peripheral corneal thinning in KG and PMD must be investigated in further studies.

Treatment strategies for the management of acute hydrops

Acute corneal hydrops is a condition characterized by marked stromal edema attributable to leakage of aqueous humor through a rupture in Descemet's membrane. In addition to the clinical examination, imaging options include ultrasound biomicroscopy, anterior segment optical coherence tomography and in vivo confocal microscopy. While it is a self-limiting condition, the duration of acute hydrops is an important factor linked to complications such as neovascularization. Therapeutic options may relieve symptoms and/or reduce healing time; these include conservative, medical and/or surgical therapies. Several new medical and surgical management options have been reported in the past few years and will be discussed in this article.

Evaluation and management of a spontaneous corneal rupture secondary to pellucid marginal degeneration, using swept-source anterior segment optical coherence tomography

We describe a case of bilateral spontaneous corneal perforation secondary to pellucid marginal degeneration and present the associated swept-source anterior segment optical coherence tomography (SS-ASOCT) findings and management principles used.

A 47-year-old woman presented with ocular pain, redness, foreign body sensation and clear discharge in the right eye in 2017 and with very similar symptoms in 2019 in the left eye. Clinically she had a corneal perforation at the inferior cornea with associated loss of anterior chamber volume. Corneal topography demonstrated peripheral thinning and steepening in the contralateral eye. ASOCT images revealed full-thickness perforation, iridocorneal touch and iris stranding. The patient was managed with a combination of contact bandaging and corneal gluing.

SS-ASOCT is a useful adjunctive tool in the clinical assessment and evaluation of spontaneous corneal perforation. Alongside the clinical evaluation, it can be used to monitor the clinical response.

Evaluating the safety and efficacy of compression sutures with intracameral perfluoropropane (C3F8) in the management of acute corneal hydrops

BACKGROUND

To evaluate the safety and efficacy of using corneal compression sutures with intracameral perfluoropropane (C3F8) in patients presenting with acute corneal hydrops in ectatic disorders.

METHODS

A retrospective analysis was done for 43 eyes of patients of acute corneal hydrops, managed using a combination of intracameral 14% C3F8 and full-thickness compression sutures. Time for resolution of edema, corneal thickness (CT) change on anterior segment ocular coherence tomography (ASOCT), and visual outcomes were assessed.

RESULTS

Corneal edema resolved with a mean duration of 14.8 ± 3.5 days (range 10-21). The mean CT on ASOCT decreased from a mean of 1437 µm (689-2770 µm) preoperatively to 543 µm (434 -66 µm) on the complete resolution of corneal edema.

CONCLUSION

Our results suggest that full-thickness compression sutures and intracameral C3F8 injection can restore the imperviousness of posterior stroma. This technique appears to be a safe and effective technique for faster resolution of corneal edema post hydrops.

Long-term outcome of custom toric intraocular lens for treating high astigmatism in case of cataract associated with pellucid marginal corneal degeneration

Pellucid marginal corneal degeneration (PMCD) is a progressive corneal ectasia that ultimately results in high regular astigmatism and correction of this astigmatism is always challenging. However, when a PMCD patient develops a cataract, it provides a golden opportunity to treat this coexisting astigmatism with toric intraocular lens (IOL) implantation. Regular toric IOLs would correct astigmatism only up to 6 diopters in the IOL plane but higher astigmatism would require customization of such IOLs. Our case report describes the long term outcomes of customized toric IOL to tackle this high astigmatism during cataract surgery in PMCD cases.

A Teenager with Vernal Keratoconjunctivitis and Pellucid Marginal Degeneration, Presenting with Exotropia

Background

Vernal keratoconjunctivitis (VKC), an allergic disease, has a known association with ectatic disorders of the cornea. Pellucid marginal degeneration (PMD) is a bilateral, asymmetrical, ectatic disorder of the cornea characterized by inferior corneal thinning. We report a case of sensory exotropia due to PMD in association with VKC.

Case Details

A 19-year old boy with a history of VKC presented with exotropia of the right eye of 3 years’ duration. His unaided vision in his right eye was 1/60 and in his left eye it was 6/36. On examination, both eyes had high against the rule astigmatism, which was more in the right eye. There was exotropia of 15º (40 prism diopter base in) in the right eye with suppression (Worth four dot test). Corneal examination in both eyes showed inferior band thinning, 2 mm above the inferior limbus, extending from 4 to 8 clock hours, with bulging of the cornea just above the thinning. The clinical features were suggestive of PMD, which was supported by his corneal scans – Atlas, Pentacam, and Optovue. Although he was undergoing treatment for VKC, the onset of PMD and decrease in vision went unnoticed. The asymmetric error which was not corrected during the sensitive period of visual development led to sensory exotropia.

Conclusion

A child with VKC should undergo regular refraction so as not to miss any ectatic changes occurring in the cornea. A delay in diagnosing corneal ectasia may negate the possibility of collagen cross-linking which prevents progression of ectasia. If visual rehabilitation is delayed beyond the age of visual maturation, it can lead to strabismus, suppression, and loss of binocular function.

Aberrometric outcome of customized toric IOL in cataract with very high corneal astigmatism due to pellucid marginal degeneration

A case of pellucid marginal degeneration (PMD) with cataract where a customized high-power toric IOL was implanted is reported. The patient had preoperative corneal astigmatism of 13.96 diopters (D), and a customized toric IOL of 19 D toricity was implanted; postoperative visual acuity was 6/9 on Snellen chart. The visual quality and aberrometric outcome were assessed with a ray-tracing aberrometer. The toric IOL gave not only a better uncorrected visual acuity but also better quality of vision in this patient with corneal astigmatism due to PMD.

Late progressive corneal flattening, haze and visual loss after eccentric crosslinking for Pellucid marginal degeneration

Purpose

Observation

Conclusion and Importance

Corneal cross-linking as a treatment for corneal dystrophy with secondary bacterial infection in a Friesian horse

Corneal cross-linking should be considered as treatment option in Friesian horses with infectious keratitis and corneal dystrophy. Optical coherence tomography, giving information of corneal structure, can help for diagnosis and monitoring.

Corneal crosslinking in a case with Axenfeld-Rieger syndrome and unilateral pellucid marginal degeneration

A 31-year-old male patient presented with the complaint of progressive vision loss in his left eye. Slit-lamp examination showed posterior embryotoxon, iris hypoplasia, and iridocorneal adhesion in both eyes, corectopia in the right, and peripheral inferior thinning and ectasia in the left eye. Corneal topography showed slightly asymmetric bowtie pattern in the right eye and crab-claw pattern in the left eye. Topographic examination was compared with his previous topography. The comparison showed 1.6-D steepening of maximum keratometry (K_max) and 22-µm decrease of thinnest corneal pachymetry. Corneal crosslinking treatment was performed on the left eye. At the postoperative 28-month follow-up visit, K_max decreased from 54.1 to 53.0 D and corrected distance visual acuity improved to 20/20 with scleral lens. This is the first reported a case with Axenfeld–Rieger syndrome and pellucid marginal degeneration association. We suggest that corneal crosslinking can be useful for management of pellucid marginal degeneration and longer follow-up might be needed in order to corroborate the effectiveness of the corneal crosslinking procedure.

Surgical management of peripheral corneal thinning disorders

The peripheral corneal thinning disorders are associated with degenerative, autoimmune, or infective causes. Corneal thinning can subsequently affect the visual acuity either by inducing severe astigmatism or by progressive involvement of the central cornea. In addition to this, the integrity of the eye is at risk. Medical management is necessary to address the underlying inflammatory or infectious causes; however, most of the cases require surgical intervention for tectonic support or for visual rehabilitation in patients with severe astigmatism. Preoperative investigations help in mapping the corneal curvature and thickness, thereby facilitating planning of treatment. Routine corneal transplantation techniques do not yield good results in peripheral corneal thinning disorders. Various surgical modifications have been described to manage these challenging cases. We review the available literature on causes and management of peripheral corneal thinning disorders.

Prospective, randomized contralateral eye study of accelerated and conventional corneal cross-linking in pediatric keratoconus

PURPOSE

To compare the outcomes of two different cross-linking (CXL) protocols, in pediatric keratoconus eyes.

MATERIALS AND METHODS

In this prospective randomized contralateral eye interventional study, 68 eyes of 34 patients, 9-16 years old, underwent CXL and enrolled between October 2011 and October 2013. Group A represents conventional riboflavin-ultraviolet A (UVA)-induced CXL with 30 min of exposure to UVA irradiation of 3 mW/cm². Group B represents accelerated cross-linking with 5 min of continuous UVA irradiation of 18 mW/cm². In either group, total energy delivered was adjusted to 5.4 J/cm². Follow-up of all patients was accomplished throughout the postoperative 3 years, and the data from the preoperative, 12, 24, and 36 months visits were analyzed and compared in both groups. Uncorrected visual acuity, corrected distance visual acuity, steepest keratometry (K_max), corneal astigmatism (simulated K), total wavefront aberrations, central corneal thickness (CCT), corneal densitometry, manifest refraction spherical equivalent, and endothelial cell density (ECD) were evaluated at baseline, 12, 24, and 36 months post-CXL.

RESULTS

At 1-year assessment, the mean value of UCVA, CDVA, and K_max showed a statistically significant difference between both groups, without any documented change in the variables throughout the remaining follow-up (1-3-year) period. Twelve months postoperatively, mean LogMAR UCVA and CDVA were (0.11 ± 1.60) and (0.03 ± 1.60), respectively, in accelerated CXL group, compared to conventional CXL group values of (0.20 ± 1.00) and (0.06 ± 1.22), showing a statistically significant difference (P < 0.05). Mean K_max in accelerated CXL group (45.47 ± 0.44) showed a statistically significant difference (P < 0.05) compared to conventional CXL group (46.41 ± 1.59) at 12 months post-CXL. On the other hand, wavefront aberrations, simulated K, corneal densitometry, ECD, and CCT changes showed nonstatistically significant difference in conventional CXL group, compared to accelerated CXL group (P > 0.05) throughout the follow-up course.

CONCLUSIONS

Both conventional and accelerated CXL improved UCVA and CDVA, attenuated disease progression, and reduced corneal steepness and wavefront aberrations at 1, 2, and 3 years postoperatively. In no case did keratoconus progress over the 36-month follow-up.

Primary Outcomes of Accelerated Epithelium-Off Corneal Cross-Linking in Progressive Keratoconus in Children: A 1-Year Prospective Study

Purpose

To evaluate corneal transparency following accelerated collagen cross-linking (ACXL) in pediatric keratoconus.

Design

A prospective interventional case series.

Methods

This study included 47 eyes (25 patients), aged 9–14 years, with documented progressive keratoconus. After applying 0.1% riboflavin drops, ACXL was performed. Assessment included corrected distance visual acuity (CDVA), uncorrected visual acuity (UCVA), corneal haze, and corneal densitometry in grayscale units (GSU).

Result

The mean baseline and corneal densitometry peaked at 3 months post-ACXL while central and posterior densitometry showed a statistically significant increase (P < 0.05) and peaked at 8 months postoperatively. By 12 months, densitometry in all corneal layers (P ≥ 0.99) and concentric zones (P ≥ 0.97) reached near baseline values. Slit-lamp graded haze peaked at 1 month to 1.82 ± 0.65 (P < 0.05) and declined to near baseline at 12 months (0.39 ± 0.58). There was a statistically significant increase in the mean UCVA and CDVA at 12 months.

Conclusion

Total and anterior corneal densitometry peaked after 3 months, while central and posterior densitometry peaked after 8 months. Maximum haze was at 1 month post-ACXL. All corneal layers, concentric zone densitometry and haze reached near baseline values after 1 year. Scheimpflug densitometry showed weak correlation with CDVA over the 12-month follow-up period (r = −0.193).

Crab claw pattern on corneal topography: pellucid marginal degeneration or inferior keratoconus?

PurposeTo evaluate the topographic, tomographic, and densitometric properties of patients with pellucid marginal degeneration (PMD) and inferior keratoconus.Patients and methodsRetrospective, comparative case series. Forty-seven eyes of 32 patients with crab claw patterns were identified from 2751 patients with corneal ectasia. They were divided into two groups, inferior keratoconus and PMD, based on clinical findings. The topographic, tomographic, and densitometric measurements were analyzed.ResultsPMD was detected in 11 eyes of eight patients (mean age 50.2±11.1 years), and inferior keratoconus was detected in 36 eyes of 24 patients (mean age 34.7±10.1 years). The control group consisted of 40 patients (33.1±4.6 years). The thinnest corneal point and maximum anterior and posterior elevation points were located lower in the PMD than in the inferior keratoconus (P<0.01). In the PMD, all deviation indices were higher than the controls (P<0.01), whereas the deviation indices, except Dt (P=0.960), were lower than the inferior keratoconus (P<0.01). The densitometry values of PMD were significantly higher than those of the controls in all zones and layers (P<0.01) and significantly higher than the densitometry values of inferior keratoconus in the 6-10 and 10-12 mm zones (P<0.05).ConclusionThere is a higher probability of a patient with crab claw pattern on the topography of having inferior keratoconus than having PMD. Therefore, analyzing only the anterior corneal surface is not sufficient in differential diagnosis. Tomographic and densitometric evaluations may facilitate the differential diagnosis.

Corneal hysteresis and corneal resistance factor in pellucid marginal degeneration

Purpose

To evaluate and compare corneal hysteresis (CH) and corneal resistance factor (CRF) in pellucid marginal degeneration (PMD), keratoconus (KCN), and normal eyes using the Ocular Response Analyzer (ORA).

Methods

In this retrospective study, corneal biomechanical parameters were measured in patients with PMD (n = 102) and KCN (n = 202) and normal subjects (n = 208) using the ORA. Data, including full patient history as well as the results of refraction, slit-lamp biomicroscopy, Pentacam HR (Oculus), and ORA (Reichert; Buffalo, New York, USA), were collected from medical records. Also, the data of only one eye per individual were selected for the analysis. The inclusion criteria for PMD and KCN groups were a reliable diagnosis of these ectatic disorders based on the clinical and corneal tomographic findings. CH, CRF, CH–CRF, intraocular pressure (IOP) measurements were assessed for each subject. Data were analyzed with SPSS and MedCalc using the ANOVA, Pearson Correlation, and receiver operating characteristic (ROC) curve analysis.

Results

The mean CH was 8.91 mmHg ± 1.05 [standard deviation (SD)], 8.43 ± 0.78, and 10.89 ± 1.08 in the PMD, KCN, and normal group, respectively. Also, the mean CRF was 8.21 ± 1.35, 7.19 ± 1.11, and 10.69 ± 1.41 in the PMD, KCN, and normal group, respectively. ANOVA showed differences in the mean CH, CRF, and CH–CRF between three groups (P < 0.001). Also, ROC curve analysis showed the cut-off points ≤9.5, ≤9.5, and >1.3 mmHg for CH, CRF, and CH–CRF in the PMD group, respectively. For biomechanical parameters in PMD eyes, CRF had the highest sensitivity (75.49%) while the greatest area under the ROC curve (AUC) was seen for CH (0.903). Moreover, central corneal thickness (CCT) showed no correlation with CH (P = 0.30, r = −0.104) or CRF (P = 0.75, r = 0.033) in the PMD group.

Conclusions

This study presented the values of corneal biomechanics for PMD using the ORA. The results of the ORA were markedly different between PMD, KCN, and normal eyes.

Refractive and Corneal Aberrometric Changes After Crescentic Lamellar Wedge Resection in Pellucid Marginal Degeneration

OBJECTIVE

To evaluate the effectiveness of crescentic corneal lamellar wedge resection for the treatment of pellucid marginal degeneration (PMD) in improving refractive, visual, and corneal aberrometry.

METHODS

The study included 10 eyes of 10 patients who had undergone corneal lamellar wedge resection for PMD. Pellucid marginal degeneration was diagnosed based on the clinical signs and corneal topography. The corneal aberrometry was evaluated with Sirius corneal topography.

RESULTS

The mean follow-up period was 14.1 months (range, 9-24 months). Uncorrected visual acuity was improved in nine eyes and remained unchanged in 1 case, whereas best-corrected visual acuity was improved in all eyes postoperatively. By vector analysis, the overall mean astigmatic drift at the last visit was calculated to be 13.0±6.3 diopters (D). At last visit, significant reductions were found for all aberrometric measurements. However, the differences were not significant for the measurements of trefoil (P=0.189).

CONCLUSIONS

Corneal lamellar wedge resection is a favorable surgical option for management of PMD, allowing for improved visual acuity, keratometric cylinder, and corneal aberrations.

Tear Mediators in Corneal Ectatic Disorders

Purpose

To compare the concentrations of 11 tear mediators in order to reveal the biochemical difference between pellucid marginal degeneration (PMD) and keratoconus (KC).

Methods

We have designed a cross-sectional study in which patients with corneal ectasia based on slit-lamp biomicroscopy and Pentacam HR (keratometry values (K1, K2, Kmax), astigmatism, minimal radius of curvature (Rmin), corneal thickness (Apex and Min), indices (surface variation, vertical asymmetry, keratoconus, central keratoconus, height asymmetry and decentration)) were enrolled. Eyes of keratoconic patients were similar to the PMD patients in age and severity (K2, Kmax and Rmin). Non-stimulated tear samples were collected from nine eyes of seven PMD patients, 55 eyes of 55 KC patients and 24 eyes of 24 healthy controls. The mediators’ (interleukin -6, -10, chemokine ligand 5, -8, -10, matrix metalloproteinase (MMP) -9, -13, tissue inhibitor of metalloproteinases (TIMP)-1, tissue plasminogen activator, plasminogen activator inhibitor, nerve growth factor) concentrations were measured using Cytometric Bead Array.

Results

MMP-9 was the only mediator which presented relevant variances between the two patient groups (p = 0.005). The ratios of MMP-9 and TIMP-1 were 2.45, 0.40 and 0.23 in PMD, KC and the controls, respectively.

Conclusion

As far as we are aware, this is the first study that aims to reveal the biochemical differences between PMD and KC. Further studies of biomarkers to investigate the precise role of these mediators need to be defined, and it is important to confirm the observed changes in a larger study to gain further insights into the molecular alterations in PMD.

Differences in central and non-central keratoconus, and their effect on the objective screening thresholds for keratoconus

PURPOSE

To evaluate the differences in central and non-central keratoconus (based on cone location), and their effect on the objective screening thresholds for keratoconus.

METHODS

This comparative case series was performed at tertiary care cornea and refractive surgery service. Three groups were made: KC apex within central 2 mm (central keratoconus, n = 50), apex outside central 2mm (non-central keratoconus, n = 50) and normal controls (n = 100, with 50 cases each with apex within and outside central 2 mm). All cases underwent clinical evaluation and corneal topography (CSO, Sirius, Italy). Apex keratometry (ApexK), simulated keratometry at 3 mm (SimK), central corneal thickness (CCT) and minimum corneal thickness (MCT), anterior corneal higher-order aberrations root mean square (HOARMS), and Zernike's coefficients up to fourth order at different zones were measured.

RESULTS

In spite of the keratoconic groups having comparable ApexK (p > 0.05), central keratoconus had higher SimK and thinner CCT and MCT (p < 0.001). HOARMS was significantly more for central keratoconus at 3 mm zones. These findings had moderate to large effect size (Cohen's d). Receiver operating curve analysis was carried out to compare central keratoconus and non-central keratoconus with control group. ApexK and HOARMS had best discriminative parameters. Using single parametric suspicion cut-offs of 'either SimK steep >47.2 D or CCT < 491.6 μ' had a good sensitivity (0.98) for central keratoconus, but not for non-central keratoconus (0.80). Changing this cut-off to 'either SimK steep K ≥ 45.8 D or CCT ≤ 503 μ' gave a sensitivity and specificity of 0.95 and 0.87 for non-central keratoconus and 0.99 and 0.87 for central keratoconus.

CONCLUSION

Non-central keratoconus has lesser effect on SimK, pachymetry and smaller-aperture HOARMS. Using 'SimK steep >47.2 D or CCT < 491.6 μ' may miss timely referral for topography in many of these cases. Using more stringent criteria of SimK steep K ≥ 45.8 D or CCT ≤ 503 μ to get a corneal topography done to rule out keratoconus is recommended, especially in cohorts with higher risk.

Characterization of Ocular Biomechanics in Pellucid Marginal Degeneration

PURPOSE

This study sought to investigate the diagnostic capacity of corneal biomechanical response parameters in a group of patients with pellucid marginal degeneration (PMD) using the Ocular Response Analyzer (ORA) and Corvis ST devices.

METHODS

In this prospective clinical study, we used the Corvis ST and ORA devices to investigate the ocular biomechanics of patients with PMD. Eighty-one eyes were included, and 2 study groups were formed: the PMD group (the study group, n = 29) and the control group (n = 52). We focused on 13 biomechanical parameters. Statistical analysis was performed using SPSS. Biomechanical parameters for the 2 groups were compared using analysis of covariance.

RESULTS

The ORA results demonstrated that the Keratoconus Match Index was significantly lower in the PMD group than in the control group (0.031 ± 0.37 vs. 0.79 ± 0.33; P = 0.001). The 2 groups did not significantly differ with respect to intraocular pressure- and central corneal thickness-adjusted values for corneal hysteresis or corneal resistance factor. Regarding the Corvis parameters, differences between the control and PMD groups were detected for CorWmax amp (control 1.01 ± 0.01, PMD 1.06 ± 0.01; P = 0.020) and CorA2 t (control 21.78 ± 0.03, PMD 21.66 ± 0.04; P = 0.0003).

CONCLUSIONS

We identified 2 Corvis parameters that could be used to characterize PMD and differentiate PMD corneas from normal corneas. These parameters support the hypothesis that there is significantly less deformation of the central cornea in PMD corneas than in healthy corneas. However, because useful "first-line" diagnostic devices for diagnosing PMD (such as Pentacam and the ORA) exist, the Corvis ST serves as an additional diagnostic tool that can also be used for long-term monitoring after diagnosis confirmation.

Reliability of Pentacam HR Thickness Maps of the Entire Cornea in Normal, Post-Laser In Situ Keratomileusis, and Keratoconus Eyes

PURPOSE

To measure the repeatability and reproducibility of Pentacam HR system thickness maps for the entire cornea in normal, post-laser in situ keratomileusis (post-LASIK), and keratoconus (KC) eyes.

DESIGN

Reliability study.

METHODS

Sixty normal subjects (60 eyes), 30 post-LASIK subjects (60 eyes), and 14 KC patients (27 eyes) were imaged with the Pentacam HR system by 2 well-trained operators. For pachymetry the cornea was divided into 4 zones: a central zone (2-mm diameter) and concentric pericentral zone (2-5 mm), transitional zone (5-7 mm), and peripheral zone (7-10 mm). The 3 concentric zones were subdivided into 8 sectors. Intraobserver repeatability and interobserver reproducibility of entire corneal thickness maps were tested by the repeatability and reproducibility coefficients, intraclass correlation coefficients, coefficient of variation, and 95% limits of agreement.

RESULTS

From central to peripheral zones, the precision of corneal thickness measurements became gradually smaller. Central zone repeatability and reproducibility were the best in the normal, post-LASIK, and KC groups. The peripheral superior sectors showed poorer repeatability and reproducibility for all subjects. The intraobserver repeatability and interobserver reproducibility for all zones were ≤19.3 μm, ≤22.1 μm, and ≤20.7 μm, in the normal, post-LASIK, and KC groups, respectively. The intraobserver and interobserver coefficients of variation for all zones were ≤1.3%, ≤1.6%, and ≤1.6% for all 3 groups.

CONCLUSIONS

Pentacam HR system pachymetry of the entire cornea provided good precision in normal, post-LASIK, and KC corneas. Thickness measurements in the peripheral cornea should be interpreted with caution in abnormal corneas after surgery or with diseases.

Spontaneous Corneal Hydrops in a Patient with a Corneal Ulcer

PURPOSE

We report the case of a 77-year-old man with no history of keratoconus or other ectatic disorders who presented with corneal hydrops in the setting of a corneal ulcer. The risk factors, pathogenesis and treatment options of corneal hydrops are discussed.

METHOD

This is an observational case report study.

RESULTS

A 77-year-old man presented with a 1-day history of severe pain, redness, mucous discharge and photophobia in the right eye. A slit-lamp examination of the right eye showed an area of focal corneal edema and protrusion. Within the area of edema and protrusion, there was an infiltrate with an overlying epithelial defect consistent with an infectious corneal ulcer. The Seidel test showed no leakage, so a clinical diagnosis of corneal hydrops associated with nonperforated corneal ulcer was made. With appropriate antibiotic treatment, the corneal ulcer and hydrops both resolved over a 1-month period.

CONCLUSION

Corneal hydrops can occur in the setting of corneal infections.

Full-Ring Intracorneal Implantation in Corneas With Pellucid Marginal Degeneration

BACKGROUND

Keratoconus (KCN) is a progressive, non-inflammatory ectacic disorder characterized by bilateral and asymmetrical conical protrusion of the cornea. MyoRing implantation and Collagen Crosslink (CXL) are two separate effective treatments for all stages of keratoconous. This study wants to show the effect of these treatments combination in patients with moderate and severe keratoconus.

OBJECTIVES

The aim of this study was to report on the visual and refractive outcomes of corneas with pellucid marginal degeneration following MyoRing implantation (DIOPTEX GmbH).

PATIENTS AND METHODS

This study included 15 eyes of 15 patients, with an age range from 22 to 49 years old, and pellucid marginal degeneration. An intrastromal corneal ring (MyoRing) was inserted by the means of mechanical dissection using a PocketMaker microkeratome. The main outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, and keratometry readings. The mean postoperative follow-up was ten months (range 6 - 12 months).

RESULTS

The mean UDVA (LogMAR) improved significantly from 1.13 ± 0.21 preoperatively to 0.24 ± 0.13 postoperatively (P < 0.001), and the mean CDVA (LogMAR) improved significantly from 0.39 ± 0.12 to 0.19 ± 0.09 (P < 0.001). The mean cylinder of manifest refraction decreased significantly by 4.00 diopter (D) (P < 0.001). The mean spherical equivalent error (SE) decreased significantly from -6.00 ± 3.60 D to -0.70 ± 1.90 D, at the end of the follow-up period. Furthermore, with regards to corneal topography, a significant reduction was observed in keratometric values. The Kmax, Kmin and Kaverage decreased significantly by 5.00, 1.10 and 4.00 D, respectively (P < 0.001).

CONCLUSIONS

MyoRing implantation using the PocketMaker microkeratome appears to provide an effective method for treating pellucid marginal degeneration. Both UDVA and CDVA improved significantly. The corneal steepening and astigmatism were reduced in all subjects after MyoRing implantation.

Spontaneous Resolution of Acute Corneal Hydrops in a Patient With Post-LASIK Ectasia

PURPOSE

To describe a case of acute corneal hydrops in a patient with corneal ectasia after laser in situ keratomileusis (LASIK).

METHODS

An observational study presenting clinical, slit-lamp, and optical coherence tomographic findings.

RESULTS

A 66-year-old man with a history of moderate myopic astigmatism presented with a sudden loss of vision in his left eye 11 years after undergoing LASIK. He underwent a single enhancement in his left eye and was subsequently diagnosed with ectasia 9 years later. Slit-lamp examination demonstrated a small tear in the Descemet membrane with a large fluid-filled cleft separating the LASIK flap and extending to the flap edge. Because no aqueous humor leakage was detected, the patient was managed conservatively with eventual resolution of the fluid-filled cleft and return of 20/30 visual acuity.

CONCLUSIONS

Acute corneal hydrops is a rare complication of post-LASIK corneal ectasia. In the absence of flap dehiscence and wound leak, such patients may be managed with simple observation.

Acute corneal hydrops in keratoconus: a national prospective study of incidence and management

PurposeTo determine incidence and management of acute corneal hydrops in the UK.MethodsWe used the BOSU report card system to survey cases of acute corneal hydrops in patients with keratoconus that occurred in the UK between November 2009 and December 2010. Ophthalmologists who reported a case were sent an initial questionnaire, with a follow-up questionnaire after 6 months. We collected information on the demographics, complications, changes in visual acuity, and management. The 2011 National Census was used as a source for population and ethnicity in the UK.ResultsThere were 73 incident cases of acute corneal hydrops, with a response to the initial questionnaire for 64 (88%) patients and follow-up data at 6 months for 57 (78%) patients. For the 64 confirmed cases the median (interquartile range) age of onset was 31.9 (23.2, 41.3) years and 48 (75%) of the cases occurred in males. A total of 42 (66%) patients were white, 14 (22%) were South Asian, and 7 (11%) were black. The proportion of South Asian and black patients with acute corneal hydrops was significantly higher than in the general population (P<0.001). The minimum estimated annual incidence of acute corneal hydrops in patients with keratoconus was estimated to be 1.43 (1.10, 1.83) per 1000. At 6 months following acute corneal hydrops a decision to proceed with keratoplasty had been made for 12 (20.3%) patients.ConclusionsThis is the first population-based estimate of the incidence of acute corneal hydrops in keratoconus.

Outcome of complete intrastromal ring implantation using femtosecond laser in pellucid marginal degeneration

PURPOSE

To evaluate the effect of complete intrastromal corneal ring implantations on patients with pellucid marginal degeneration (PMD).

DESIGN

Prospective interventional case series.

PATIENTS AND METHODS

Thirty-three eyes with PMD were included into the study. After pocket creation with femtosecond laser (Femtec; 20/10 PerfectVision), MyoRing implantation was performed. Uncorrected and corrected distance visual acuity (UDVA, CDVA), subjective refraction, keratometry, central corneal thickness, corneal biomechanical profile (Ocular Response Analysis), and whole-eye wavefront aberrometry (iTrace) were evaluated preoperatively and also postoperatively, 1 month, 3 months, 6 months, and 1 year after the operation.

RESULTS

One month after surgery, significant improvements were observed in UDVA (ANOVA; P=0.02), mean keratometry, sphere (ANOVA; P <0.001), and cylinder (ANOVA; P=0.04) with no significant changes afterwards. No significant change occurred in the corneal biomechanical profile. Primary coma and trefoil reduced after 1 year (ANOVA; P values were 0.02 and 0.06, respectively). Primary spherical aberration significantly increased according to the 1-year follow-up (ANOVA; P<0.001). No significant complication was observed.

CONCLUSION

MyoRing is considered as a treatment modality for spherocylindrical correction in patients with PMD, with an acceptable safety and efficacy profile.