Recurrence or Re-emergence of Keratoconus – What is the Evidence Telling Us? Literature Review and Two Case Reports

Surgical management of complicated Descemet's membrane detachment in corneas without prior endothelial keratoplasty

PURPOSE

To provide insights into morphologic and functional features of eyes with complicated Descemet's membrane detachment (DMD) and report clinical outcomes after surgical intervention.

METHODS

Retrospective study of 18 eyes with complicated DMD between 2010 and 2022. Complicated DMD was defined if any of the following criteria applied: prior penetrating keratoplasty (PKP), corneal thinning, total DMD or persistent DMD after Air/Gas-Descemetopexy. Causes, surgical management, and clinical outcomes were analyzed. Scheimpflug tomography, anterior segment optical coherence tomography (AS-OCT) and histologic examination were performed to characterize corneas with DMD.

RESULTS

Fourteen eyes with prior PKP developed spontaneous DMD after 24.2 ± 12.9 years (range = 18 months - 47 years, median = 25.7 years). Complicated DMD without prior PKP was associated in three eyes after cataract surgery and in one eye after infectious keratitis. In cases with previous PKP, AS-OCT demonstrated rupture of Descemet's membrane (DM) in five eyes and spontaneous reattachment was found in four eyes within 8 weeks of initial diagnosis, with no rupture of DM in any of the cases. There was no rupture of DM in corneas without previous PKP. After prior keratoplasty, definitive surgical treatment was repeat PKP in 13 eyes and Air/Gas-Descemetopexy in one eye. In corneas without prior keratoplasty, three eyes underwent PKP and one eye Air/Gas-Descemetopexy. Histological examination of two corneal explants revealed a severely thinned graft-host junction and a disrupted DM close to the graft-host junction. Visual acuity improved from 1.80 ± 0.58 logMAR to 0.75 ± 0.69 logMAR after prior PKP and from 1.45 ± 0.65 logMAR to 0.85 ± 1.13 logMAR without prior PKP. The postoperative course was uneventful in 16 of 18 eyes.

CONCLUSION

PKP is an effective treatment option for complicated DMD, especially in ectatic corneas, whereas Air/Gas-Descemetopexy or Descemet Membrane Endothelial Keratoplasty do not address the primary issue of the curvature anomaly.

Impact of topographic localization of corneal ectasia on the outcomes of deep anterior lamellar keratoplasty employing large (9 mm) versus conventional diameter (8 mm) grafts

OBJECTIVES

Visual and topographic outcomes of large (9.0 mm) versus conventional (8.0 mm) deep anterior lamellar keratoplasty (DALK) for the treatment of keratoconus (KC) were compared in relation to the different localization of the corneal ectasia (within or beyond the central 8.0 mm).

METHODS

This is a retrospective, comparative case series. Preoperatively, the topographic extension of the conus was calculated by measuring the distance from the geometric center of the cornea and the outermost point of the corneal ectasia (ectasia <8.0 mm, group A; ectasia ≥8.0 mm, group B). DALK was performed using both small grafts (8.0 mm, group 1) and large grafts (9.0 mm, group 2). Best-corrected visual acuity and topographic astigmatism were evaluated preoperatively (T0) and postoperatively after complete suture removal (1 year, T1).

RESULTS

Data from 224 eyes of 196 patients (mean age 37.6 ± 15.1 years) were evaluated. Topographic astigmatism improved from T0 to T1 (4.94 ± 2.92 diopters (D) [95% CI, 4.56-5.33] vs 4.19 ± 2.45 D [95% CI, 3.87-4.51], p = 0.001). There was no significant difference in postoperative topographic cylinder between group 1 and group 2 when considering eyes with corneal ectasia <8.0 mm (group 1 A, 4.15 ± 2.19 D [95% CI, 3.64-4.66] vs group 2 A, 3.65 ± 2.13 D [95% CI, 2.92-4.38], p = 0.14); conversely, the difference was significant considering eyes with corneal ectasia ≥8.0 mm (group 1B, 4.74 ± 2.90 D [95% CI, 4.09-5.38] vs group 2B, 3.68 ± 1.94 D [95% CI, 3.10-4.26], p = 0.02).

CONCLUSIONS

Large 9.0-mm DALK provided better anatomical outcomes compared to conventional 8.0-mm DALK, particularly in eyes with corneal ectasia extending beyond the central 8.0 mm.

Corneal cross-linking for treatment of keratoconus relapse in post-keratoplasty eyes

PURPOSE

Keratoconus relapse after penetrating keratoplasty is a rare condition that may result in severe visual deterioration and corneal graft thinning. Therefore, treatment to stabilize the cornea should be considered. The purpose of this study was to evaluate the safety and efficacy of Corneal Cross-Linking (CXL) in eyes with relapse of keratoconus after penetrating keratoplasty for keratoconus.

MATERIALS AND METHODS

A retrospective review of eyes that developed keratoconus relapse following a penetrating keratoplasty and treated with CXL. The main outcome measures were change in maximal keratometry (Kmax), best-corrected distance visual acuity (BCVA), thinnest corneal thickness (TCT) and central corneal thickness (CCT), and complications.

RESULTS

We identified 10 consecutive eyes of 9 patients. Preoperative median BCVA before the CXL and 1 year after the CXL procedure remained stable (p = 0.68). The median (IQR) of Kmax improved from 63.2 (24.9) D before the CXL procedure to 62.2 (27.1) D at 1 year postoperatively (P = 0.028). Median TCT and CCT also remained with no significant change 1 year after CXL. No complications were noted following the procedure.

CONCLUSION

CXL in eyes with keratoconus relapse after keratoplasty is a safe and effective procedure enabling not only visual stabilization but also might bring keratometry improvement. Routine follow-up after keratoplasty should be performed for early detection of keratoconus relapse and CXL is timely advised when such a relapse is documented.

High Astigmatism Secondary to Peripheral Ectasia Recurrence in Postpenetrating Keratoplasty Eyes Managed With Miniscleral Contact Lenses

OBJECTIVES

After penetrating keratoplasty (PK) for keratoconus, vision can be impaired by high-degree astigmatism, particularly in those patients with recurrent peripheral ectasia. Scleral contact lenses (CLs) have long been used in the management of keratoconus both in treatment-naive corneas and those postcorneal transplants. We report the use of miniscleral CLs and their related visual and clinical outcomes in a series of patients with post-PK peripheral rim ectasia.

METHODS

In this retrospective case series, 5 patients (7 eyes) presented because of reduced visual acuity with their spectacles/CLs and/or reduced comfort with their existing rigid gas-permeable lenses. All patients in this series underwent PK more than two decades ago for keratoconus (mean 28.7 years±7.2). All patients demonstrated characteristic thinning at the graft-host junction, with anterior chamber deepening. Central corneas had remained clear in all patients inferring high visual potential. Contact lenses used were No 7 Comfort 15 miniscleral and the Onefit MED scleral with 14.5 mm and 15.6 mm diameters, respectively.

RESULTS

All eyes achieved a best-corrected visual acuity of 6/9 or greater. One case had difficulty with insertion and removal and has since discontinued wearing lens at this time. All others are successfully wearing the lenses regularly.

CONCLUSION

Despite advances in CL design, surgical management is still required in some patients. Miniscleral CLs are effective in the refractive management of peripheral ectasia in keratoconic post-PK eyes and should be considered in such eyes before proceeding with repeat surgical intervention.

High Astigmatism After Conventional Diameter Deep Anterior Lamellar Keratoplasty in Keratoconus Can Be Successfully Managed With Repeat Wide Diameter Deep Anterior Lamellar Keratoplasty

PURPOSE

The aim of this study was to describe a new surgical technique to replace a conventional diameter (≤8 mm) deep anterior lamellar keratoplasty (DALK) graft with associated high astigmatism refractory to corneal-based astigmatic procedure/intolerance to contact lenses with a larger diameter (≥9 mm) DALK graft to improve best spectacle-corrected visual acuity (BSCVA).

METHODS

Two eyes from 2 keratoconic patients at Southend University Hospital between December 2019 and June 2021 with a minimum follow-up of 17 months were evaluated. The primary outcome of interest was Snellen BSCVA with a secondary outcome of topographic cylinder.

RESULTS

Patient 1 had undergone initial 8 mm diameter DALK, with residual keratometric astigmatism of nearly 12 diopters (D) postoperatively despite numerous astigmatic interventions, with a BSCVA of 6/60, before undergoing 9 mm diameter repeat modified DALK. After suture removal and subsequent in-the-wound blunt manual relaxing incisions, the patient had a final keratometric astigmatism of 3.5 D, manifest refraction of plano/-3.50 × 175, and a BSCVA of 6/9. Patient 2 had undergone initial 7.75 mm diameter DALK, with residual keratometric astigmatism of 10.5 D with a BSCVA of counting fingers. The patient underwent 9 mm repeat modified DALK with final residual keratometric astigmatism of 3.1 D after suture removal, manifest refraction of -1.00/-2.75 × 25, and BSCVA of 6/9.

CONCLUSIONS

Wide diameter DALK (>9 mm) is effective in the management of conventional diameter DALK (≤8 mm) associated high astigmatism in keratoconus. Creation of a peripheral posterior stromal shoulder also allows safe further titration of residual astigmatism if needed.

Recurrent keratoconus: an analysis of breaks in Bowman's layer in corneal grafts

OBJECTIVE

To study in a masked fashion whether an objective histological feature associated with keratoconus (KCN) occurs in donor corneas in eyes originally receiving a corneal graft for KCN.

METHODS

Two ocular pathologists performed a retrospective masked histological analysis of slides from donor buttons recovered from 21 eyes with a history of KCN undergoing repeat penetrating keratoplasty (failed-PK-KCN), 11 eyes that underwent their first PK due to KCN (primary KCN), and 11 eyes without history of KCN which underwent PK for other conditions (failed-PK-non-KCN). Breaks/gaps in Bowman's layer served as the pathological feature indicative of recurrent KCN.

RESULTS

Breaks in Bowman's layer were present in 18/21 (86%) of the failed-PK-KCN group, 10/11 (91%) of the primary KCN group, and in 3/11 (27%) of the failed-PK-non-KCN group. Pathological evidence suggests that the prevalence of breaks is significantly higher in grafted patients with a history of KCN than non-KCN controls (OR: 16.0, 95% CI 2.63 to 97.2, Fisher's exact test p=0.0018) with a conservative Bonferroni criterion of p <0.017 to account for multiple group comparisons. There was no statistically significant difference found between the failed-PK-KCN and primary KCN groups.

CONCLUSIONS

This study provides histological evidence that breaks and gaps in Bowman's layer, consistent with those found in primary KCN, may develop within the donor tissue in eyes with a history of KCN.

[From ocular itching to eye rubbing: a review of the literature]

Ocular itching and eye rubbing are frequent complaints in an ophthalmology practice. Numerous studies address the consequences of eye rubbing, such as keratoconus. However, there are few studies concerning the pathophysiology of itching, its transmission pathways, or its interactions with eye rubbing. Through this literature review, we will address the various clinical, physiological and therapeutic aspects of this pair of symptoms with a variety of ocular consequences. We will then describe the state of the art in itching and scratching in dermatology, in order to draw a parallel between these two vicious cycles. A better understanding of the pathophysiology of ocular itching and eye rubbing, as well as new studies based on dermatological data, might allow more appropriate clinical management of our patients and their symptoms.

Analysis of visual and refractive results after wedge resection for high astigmatism after penetrating keratoplasty in keratoconus

PURPOSE

To analyze visual and refractive results after wedge resection to correct high astigmatism after penetrating keratoplasty (PK) for keratoconus.

SETTING

Cornea Unit of the Centro de Oftalmología Barraquer Barcelona, Spain.

DESIGN

A retrospective quasi-experimental, before and after study.

METHODS

Patients who developed high astigmatism or ectasia in the graft-host junction after PK were treated with wedge resection. The following variables were studied before the surgery, 1-year after and at the final visit: uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive and topographic astigmatism and spherical equivalent. Vectorial analysis of the astigmatism changes was performed.

RESULTS

Fifty-one eyes were included with a mean follow-up of 4.19 ± 3.09 years. Mean refractive astigmatism was 11.47 ± 3.57 diopters (D) pre-operatively and 4.79 ± 3.32 D at the final follow-up (p < 0.001). The mean centroid changed from 2.65 ± 11.82 D at 23 degrees preoperatively to 0.35 ± 5.86 D at 127 degrees postoperatively. Concerning spherical equivalent, the mean preoperative value was -3.10 ± 4.15 D and the mean postoperative value was -1.55 ± 3.41 D (p = 0.002). Mean pre-operative and final follow-up UDVA were 1.25 ± 0.27 and 0.84 ± 0.50 (p < 0.001). Mean Pre-op and final follow-up CDVA were 0.27 ± 0.19 and 0.24 ± 0.24.

CONCLUSIONS

Wedge resection is a useful surgical procedure to correct high astigmatism. It is a safe technique with moderate efficacy and may be considered as initial procedure of choice in high astigmatism due to long-term ectasia in the graft-host junction after PK for keratoconus.

Post Penetrating Keratoplasty Ectasia: Incidence, Risk Factors, Clinical Features, and Treatment Options

BACKGROUND: Corneal transplantation in keratoconus (KC) patients is generally considered to be successful with a high grade of patient satisfaction. Long-term studies suggest a 6% to 11% probability of KC recurrence manifested by keratometric instability and progressive corneal ectasia. METHODS: We propose to review the frequency, risk factors for the development, and the surgical options for the correction of high irregular astigmatism due to late graft ectasia following penetrating keratoplasty (PK). RESULTS: Post-keratoplasty ectasia is characterized by increasing corneal steepening with myopic shift and high irregular astigmatism, developing years or decades after PK, mostly occurring in KC patients. Contact lenses may adequately improve the visual acuity; however, because these patients are often elderly and intolerant to hard contact lenses, ultimately a surgical correction is proposed to the patient. Compressive suture and corneal wedge resection may improve corneal astigmatism, but the outcomes are unpredictable and often temporary. For this reason, a larger PK graft is often proposed for surgical rehabilitation with the consequence of removing more of the recipient’s healthy endothelium and exposing the patient to a renewed immunogenic stimulus and short-term graft failure for endothelial decompensation. More recently, lamellar keratoplasty using various techniques has been proposed as an alternative to PK in order to maximize the visual outcomes and minimize the complications. CONCLUSIONS: Management of advanced corneal ectasia is a significant challenge for corneal surgeons. Many surgical approaches have been developed, so there is a large arsenal of surgical operations to correct post-PK ectasia. Among them, large-diameter anterior lamellar keratoplasty may be a viable, safer, and effective alternative to PK for the correction of post-keratoplasty ectasia.

Comparison of deep anterior lamellar keratoplasty and corneal cross-linking in patients with advanced keratoconus

PURPOSE

To compare outcomes of deep anterior lamellar keratoplasty (DALK) and corneal cross-linking (CXL) in patients with advanced keratoconus, with the primary aim of assessing CXL as a potential therapeutic alternative.

STUDY DESIGN

Retrospective, multi-center, comparative study.

METHODS

Patients with advanced keratoconus (maximum keratometry reading (K-max) > 58D, best spectacle-corrected visual acuity worse than 0.52logMAR), undergoing either DALK or CXL treatment at four tertiary ophthalmic centers in Wenzhou, Hangzhou, Nanjing and Wuhan were included. Visual acuity, refractive error, corneal topography and complications were evaluated at baseline and at least 2 year postoperatively.

RESULTS

75 eyes of 72 patients were included, of which 37 eyes underwent DALK and 38 eyes, CXL. A larger reduction in Kmax was observed in the DALK group (-18.18 ± 9.44 D versus -1.10 ± 2.70D, p < 0.001). Seven eyes (18%) in the CXL group showed progression of keratoconus. No disease progression was observed in the DALK group. Greater improvements in best spectacle-corrected visual acuity (logMAR) were observed in the DALK group (-0.59 ± 0.25 versus -0.24 ± 0.44, p < 0.001).

CONCLUSIONS

Compared to CXL, DALK leads to larger reductions in Kmax and better improvement in visual acuity in advanced keratoconus.

Post-penetrating keratoplasty astigmatism

Postoperative astigmatism is one of the common complications affecting visual outcomes after a penetrating keratoplasty. It can result from various factors related to host, donor and surgical technique, resulting in suboptimal visual outcome. While some of the measures taken during preoperative planning and during actual surgery can reduce the magnitude of postoperative astigmatism, postoperative correction of astigmatism is often required in cases with high degrees of astigmatism. When spectacles and contact lenses fail to provide optimal visual outcomes, various surgical techniques that include astigmatic keratotomy, compression sutures, toric intraocular lens placement, and laser refractive procedures can be considered. When none of these techniques are able to achieve a desired result with in the acceptable optical range, a repeat keratoplasty is considered a last option. We discuss the various causes and management of complication of postoperative astigmatism occurring after a full thickness corneal transplantation surgery.

Anterior pituitary, sex hormones, and keratoconus: Beyond traditional targets

"The Diseases of the Horny-coat of The Eye", known today as keratoconus, is a progressive, multifactorial, non-inflammatory ectatic corneal disorder that is characterized by steepening (bulging) and thinning of the cornea, irregular astigmatism, myopia, and scarring that can cause devastating vision loss. The significant socioeconomic impact of the disease is immeasurable, as patients with keratoconus can have difficulties securing certain jobs or even joining the military. Despite the introduction of corneal crosslinking and improvements in scleral contact lens designs, corneal transplants remain the main surgical intervention for treating keratoconus refractory to medical therapy and visual rehabilitation. To-date, the etiology and pathogenesis of keratoconus remains unclear. Research studies have increased exponentially over the years, highlighting the clinical significance and international interest in this disease. Hormonal imbalances have been linked to keratoconus, both clinically and experimentally, with both sexes affected. However, it is unclear how (molecular/cellular signaling) or when (age/disease stage(s)) those hormones affect the keratoconic cornea. Previous studies have categorized the human cornea as an extragonadal tissue, showing modulation of the gonadotropins, specifically luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Studies herein provide new data (both in vitro and in vivo) to further delineate the role of hormones/gonadotropins in the keratoconus pathobiology, and propose the existence of a new axis named the Hypothalamic-Pituitary-Adrenal-Corneal (HPAC) axis.

Ultrastructural Alterations of Grafted Corneal Buttons: The Anatomic Basis for Stromal Peeling Along a Natural Plane of Separation

PURPOSE

To examine the ultrastructure of the natural plane of separation in grafted corneas and evaluate the outcomes of stromal peeling.

DESIGN

Interventional case series.

METHODS

In this multicenter study, stromal peeling was attempted in 96 consecutive eyes with unsatisfactory vision following penetrating keratoplasty (PK) for keratoconus (n = 79), herpetic keratitis (n = 11), and granular dystrophy (n = 6). Stromal exchange was performed by (1) 9 mm partial-thickness trephination; (2) creation of a corneal flap across the PK wound; (3) opening of the stromal component of the PK wound until a smooth, translucent natural plane was identified; (4) severing the attachment of the PK scar; (5) stromal peeling along the identified plane; and (6) suturing of donor lamella. Grafted corneas from cases that mandated conversion to PK were processed for transmission electron microscopy.

RESULTS

The natural plane of separation was identified in all cases. Stromal exchange was successfully completed in 84 cases (87.5%). Snellen visual acuity ≥20/40 and ≥20/25 was reached in 93% and 72% of cases at 3 years (n = 49) and 86% and 62% at 4 years (n = 21) postoperatively. Mean endothelial cell loss at 1 year was 6.6% ± 9.5%. Stromal peeling occurred along a plane lined with a continuous layer of keratocytes separating pre-Descemet membrane (DM) stroma, DM, and endothelium from the anterior stroma. Pre-DM stroma was made of poorly organized lamellae containing widely spaced, randomly arranged collagen fibrils.

CONCLUSIONS

Ultrastructural alterations in the stromal microarchitecture of grafted corneas provide evidence of a natural plane of separation identified intraoperatively. Stromal peeling can be successfully performed in post-PK eyes with various stromal pathology.

Biomechanical Effects of Deep Anterior Lamellar Keratoplasty and Penetrating Keratoplasty for Keratoconus: A Finite Element Analysis

Purpose

To theoretically compare corneal displacement and the von Mises (VM) stress distribution of deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) for keratoconus (KC) and to evaluate the effects of residual stromal thickness (RST) and intraocular pressure (IOP) on postoperative corneal biomechanics.

Methods

We performed DALK and PK simulations using Ansys by employing anisotropic nonlinear hyperelastic corneal material properties. We analyzed corneal displacement and VM stress in DALK and PK models under IOPs of 10, 15, 20, and 25 mmHg. We established two DALK models: The ideal-type DALK ensured that postoperative central corneal thickness was constant at 560 µm and the corneal graft thickness varied with RST. The clinical-type DALK ensured that corneal grafts had the same thickness (500 µm) regardless of RST. Then we analyzed the effects of RST and IOP on postoperative corneal displacement and VM stress.

Results

Corneal displacement and VM stress were lower in the DALK than in the PK model. In the ideal-type DALK model, an increase in RST was associated with increased deformation and decreased VM stress in the healing zone, except for a RST of 0 µm. In the clinical-type DALK model, deformation and VM stress in the healing zone decreased with an increase in RST, except for a RST of 0 µm.

Conclusions

DALK showed more stability than PK. For the ideal-type DALK model, an increase in RST resulted in decreased postoperative corneal biomechanics in the healing zone. For the clinical-type DALK model, corneal deformation and VM stress decreased with an increase in RST, which provides numerical evidence for the design of corneal transplantation for patients with KC.

Translational Relevance

In this computational modeling study, we first theoretically compared corneal biomechanics between DALK and PK for KC. Then, the effects of RST and IOP on postoperative corneal biomechanics were investigated. Our findings provide novel insights into the optimal design for corneal transplantation for patients with KC.

Pneumatic Dissection for Large-Diameter (9-mm) Deep Anterior Lamellar Keratoplasty in Eyes With Previous Anterior Lamellar Keratoplasty

PURPOSE

To evaluate the surgical and 3-year clinical outcomes of modified big-bubble 9-mm deep anterior lamellar keratoplasty (DALK) in eyes with previous ALK (ALK).

METHODS

In this interventional case series, 21 consecutive eyes with unsatisfactory vision after ALK (superficial ALK n = 9; laser-assisted ALK n = 7; and epikeratophakia n = 5) underwent large-diameter (9-mm) DALK. The surgery involved deep trephination based on the anterior segment optical coherence tomography pachymetry measurement at 9-mm diameter, pneumatic dissection from the base of the trephination and limited stromal clearance of the optical zone (6 mm). Main outcome measures were success rates of pneumatic dissection, best spectacle-corrected visual acuity, and complication rates.

RESULTS

Pneumatic dissection with type 1 bubble formation succeeded in 19 (90%) eyes. In the 2 remaining cases, the 6-mm optical zone was cleared by manual dissection. Perforation occurred in one of the latter cases; no procedure was converted to penetrating keratoplasty. One month after complete suture removal, the preoperative mean best spectacle-corrected visual acuity (0.75 ± 0.23 logMAR) improved to 0.09 ± 0.10 logMAR (P < 0.001) and remained stable up to 3 years after surgery. At the final follow-up, refractive astigmatism was ≤4.5 and <6 D in 20 (95%) and 21 (100%) eyes, respectively. Stromal rejection was observed in 2 eyes (10%) and was treated successfully with steroids.

CONCLUSIONS

Even in eyes with previous ALK, pneumatic dissection can be achieved through a modified DALK technique with a low risk of complications and excellent visual and refractive outcomes.

Stromal peeling for deep anterior lamellar keratoplasty in post-penetrating keratoplasty eyes

Background/aims

To evaluate the clinical outcomes of deep anterior lamellar keratoplasty performed by stromal peeling in eyes that have previously undergone penetrating keratoplasty (PK) for keratoconus.

Methods

Standardised stromal exchange included (1) 9 mm trephination of the recipient bed outside the old PK wound, (2) creation of a partial anterior corneal flap through lamellar dissection across the PK wound, (3) opening the stromal component of the old PK wound using blunt-tipped Vannas scissors until a plane of separation is reached, (4) severing the attachment of the PK surgical scar from the recipient host, (5) peeling the stroma of the PK graft from the underlying tissue and (6) suturing the donor anterior corneal lamella prepared by microkeratome dissection (450 µm depth, 9 mm diameter). Main outcome measures were success rate, best spectacle-corrected visual acuity (BSCVA) and endothelial cell loss (ECL).

Results

Of 21 post-PK eyes, stromal exchange succeeded in all but three cases, which were converted to a two-piece mushroom PK. After complete suture removal, mean BSCVA significantly improved from 0.95±0.39 logMAR preoperatively to 0.23±0.17 logMAR (p<0.001). Mean ECL was 5.4±23.2%. Double anterior chamber formation occurred in eight cases (44%), which all resolved after a single re-bubbling.

Conclusion

In post-PK eyes, stromal exchange can be performed by means of simple peeling without deep anterior lamellar dissection of the previous PK graft. Large-diameter (9 mm) repeat keratoplasty through stromal peeling yields excellent visual outcomes and minimal ECL. Double anterior chamber formation may complicate the postoperative course, but prompt intervention allows successful management.

Acute corneal edema decades after penetrating keratoplasty for keratoconus in eyes wearing scleral contact lenses

PURPOSE

To report three cases of acute corneal edema occurring decades after penetrating keratoplasty (PK) for keratoconus in eyes wearing scleral contact lenses (ScCLs) with previously clear corneal grafts.

METHODS

Retrospective chart review of three ScCL wearers presenting for sudden onset pain and blurred vision. Data extracted included clinical presentation, year and reason for PK, ocular medications and comorbidities, contact lens wearing history, results of any ancillary testing available including corneal topography, anterior segment optical coherence tomography (OCT), and specular microscopy surrounding the event, treatment and outcomes of intervention. The number of PK eyes fit with ScCLs in the author's practice was determined to estimate the prevalence of this event.

RESULTS

The three patients each had a longstanding PK for keratoconus performed between 33-35 years prior to presentation and recurrent ectasia. Each patient presented with an acute, painful eye and reduced vision either 3 days, 4 months or 9 years after refitting into ScCLs. Each eye had well demarcated focal microcystic epithelial and stromal edema within the graft and crossing the wound margin onto the host cornea. Although a definitive break or detachment of Descemet's membrane was not visualized, the presentations suggest these were episodes of acute hydrops.

CONCLUSIONS

Longstanding PKs with recurrent ectasia and acute focal edema suggestive of corneal hydrops is demonstrated in this case series of ScCL wearers. Although similar events have occurred as part of the natural history of post-PK corneas for keratoconus, the proximity of ScCL refitting to two of the events suggests some association.

Pathogenesis and complications of chronic eye rubbing in ocular allergy

PURPOSE OF REVIEW

To review the updated literature regarding eye rubbing complications and its association with ocular allergy disorders.

RECENT FINDINGS

Atopy and ocular allergy disorders, mainly vernal keratoconjunctivitis (VKC), are strongly associated with rubbing-related complications, most probably via itching and watery eye sensations that trigger the habit of chronic eye rubbing. Vigorous and prolonged rubbing may lead to establishment of corneal remodeling and ectatic disorders, such as keratoconus. Keratoconus development in rubbed eyes can be caused by mechanical mechanisms of corneal thinning and its loss of rigidity, by elevated temperature of the epithelium during rubbing, by increased intraocular pressure (IOP) because of distending forces, and by inflammatory molecules that may serve as a causal mediator between eye rubbing and keratoconus. Other eye rubbing complications include acute hydrops and perforation, IOP spikes, iris prolapse and iridoschisis rupture of lens capsule and IOL dislocation, and even posterior segment disorders, such as glaucomatous optic neuropathy, retinal detachment and extrusion of implanted silicone oil in the eye.

SUMMARY

Chronic eye rubbing in allergic eye diseases can lead to progression of keratoconus, and to other rare anterior and posterior segment complications. Strategies eliminating eye rubbing and its consequences are vital, mainly among at-risk populations, such as young children and individuals with allergic ocular disorders or corneal transplants.

The keratoconus enigma: A review with emphasis on pathogenesis

PURPOSE

To review the literature on the etiopathogenesis of keratoconus (KC).

METHODS

A literature search was conducted using PUBMED and Google Scholar for keratoconus. The authors analyzed epidemiology studies, reviews, and case reports.

RESULTS

Atopy and ocular surface inflammation are a common features of KC and should lead to a reconsideration of the traditional definition of KC as a "non inflammatory" condition. Co-morbidities suggest that KC may be the ocular manifestation of a systemic disease. Finally, KC shows higher prevalence in certain ethnicities, which calls into question the status of KC as a rare disease, at least in these communities.

CONCLUSION

We believe that future studies should test whether selected, high prevalence populations exhibit specific genetic background and/or ethno-specific environmental risk factors.

Small Molecule Modulation of the Integrated Stress Response Governs the Keratoconic Phenotype In Vitro

Purpose

The degenerative corneal disease keratoconus is a leading indicator for corneal transplant with an unknown etiology. We recently identified the activation of the integrated stress response (ISR) in ex vivo human corneas and in vitro cell culture. Utilizing small molecules to modulate the ISR we sought to investigate the effects of stimulating the ISR in healthy cells to recapitulate aspects of the in vitro keratoconic phenotype and whether relieving the ISR signaling would recover the disease phenotype.

Methods

Corneal fibroblasts were extracted from patients undergoing corneal transplant or unaffected cadaverous donor limbal rings. Cells were exposed to the DNA damage-inducible protein (GADD34) inhibitor SAL003 to stimulate the ISR, or Trans-ISRIB to relieve ISR signaling pathway. Collagen production was assessed through hydroxyproline production, Sirius Red incorporation, or quantitative (q)PCR. Western blotting, hydroxyproline, and qPCR were used to assess components of the ISR pathway and collagen production.

Results

ISR stimulation through SAL003 resulted in significant decrease of hydroxyproline and COL1A1 transcription and eventual apoptosis in normal fibroblasts. Patient (KC) fibroblast production of hydroxyproline was increased in response to ISRIB, while matrix metalloproteinase (MMP)9 production was lowered. The prospective biomarker of keratoconus prolactin-inducible factor was also upregulated in KC fibroblast cultures in response to ISRIB. Inflammatory markers TNFα and IL-1β were unaffected.

Conclusions

Activation of the ISR is sufficient to recapitulate many key aspects of the KC phenotype in unaffected cells in vitro. Inhibition of the ISR also relieves many of the hallmarks of KC in affected cells. Therefore, targeting of the ISR through small molecules is a potential therapeutic path for small molecule treatment of keratoconus.

Severity Assessment of Acute Hydrops Due to Recurrent Keratoconus after Penetrating Keratoplasty Using Anterior Segment Optical Coherence Tomography

Purpose: To compare the clinical characteristics of acute hydrops between eyes with recurrent keratoconus and eyes with treatment-naïve keratoconus.Methods: Six eyes with acute hydrops caused by recurrent keratoconus (recurrent group) and 29 eyes with acute hydrops due to treatment-naïve keratoconus (naïve group) were included. We collected data from anterior-segment optical coherence tomography (AS-OCT), corneal topography and medical records. With AS-OCT, we investigated the location of Descemet's membrane break, the length and frequency of Descemet's membrane detachment, and the speed of corneal thinning before acute hydrops.Results: Descemet's membrane breaks were detectable in 6 cases in the recurrent group (100%) and 7 cases in the naïve group (70%). Distance from the break to the central line was 2-3 mm in the recurrent group, and less than 1 mm in the naïve group (p < .001). Detachment length was significantly greater in the recurrent group than in the naïve group (p = .003). Steep corneal power values tended to increase before acute hydrops in the recurrent group, but the difference between groups was not significant (observation period; 6.03 ± 2.67, 7.36 ± 5.53 years, respectively). Penetrating keratoplasty was required in 5 cases (83%) in the recurrent group, and 8 cases (28%) in the naïve group (p = .02).Conclusions: Acute hydrops due to recurrent keratoconus occurred around graft-host junctions and was more severe than that in eyes with treatment-naïve keratoconus. Severity assessment of Descemet's membrane detachment using AS-OCT provided clues not only for diagnosis, but also for predicting prognosis.

Characteristics and risk factors of recurrent keratoconus over the long term after penetrating keratoplasty

PURPOSE

To determine the characteristics and risk factors of recurrent keratoconus (KC) after penetrating keratoplasty (PK).

METHODS

We enrolled patients who had maintained clear grafts for at least 10 years after PK based on their medical records. Patients were divided into the KC group or Others group based on the primary indication for PK. Each case was reviewed for clinically observed corneal ectasia. Steepest keratometric power (Ks), cylinder (CYL), and difference between Ks and minimum keratometric power (MinK) were analyzed in patients that underwent corneal topography more than three times after the 5th postoperative year.

RESULTS

One hundred one eyes of 82 patients were enrolled. The KC group comprised 50 eyes and the Others group comprised 51 eyes (herpes [n = 22], corneal leukoma [n = 12], and other [n = 17]). The mean period after PK was 27.2 years in the KC group and 26.0 years in the Others group. Recurrent KCs were observed in 18 eyes of 14 patients (36%), all of whom were in the KC group (p = 0.0001). Six of these eyes underwent PK again and all the grafts showed keratoconic changes histopathologically. The mean Ks during the whole observation period was 52.5 diopters (D) in the KC group and 49.2 D in the Others group (p < 0.0001). Logistic regression analysis revealed the risk factors of recurrent KC with positive Ks change and large CYL with significant p values (p = 0.0102, 0.0318, respectively).

CONCLUSIONS

KC progresses even after PK over the long term, requiring re-grafting in some cases. Risk factors for recurrent KC after PK are increasing Ks over time and a large CYL.

Ultrastructural study of peripheral and central stroma of keratoconus cornea

PURPOSE

Assess the lamellar organisation of the peripheral and central stroma of the keratoconus (KC) and normal cornea.

METHODS

Five normal and three KC corneas were fixed in 2.5% glutaraldehyde and processed for electron microscopy. The ultrathin sections were observed under JEOL 1400 TEM, and digital images were taken with a bottom-mounted 11-megapixel Quamisa camera, using the iTEM software. Measurements of the lamellae were carried out using the iTEM software. Statistical analysis was performed using the SPSS software.

RESULTS

The lamellar organisation at the centre and periphery of the KC cornea was disrupted by the presence of multiple undulations, which were more aggressive at the posterior stroma. Among the KC cornea, the mean lamellar thickness of the peripheral middle (1030.32±86.25 nm) and posterior (615.68±30.94 nm) stroma was also significantly (p<0.05) thinner than their corresponding areas of the central KC cornea (1151.1±48 nm; 783.57±31.10 nm). At the periphery of KC cornea, just above the Descemet's membrane (DM), small undulations appeared to emerge out from the DM. Furthermore, the anterior stroma of the peripheral cornea contained several lamellar sutures. The mean lamellar thickness of the peripheral and central KC cornea was significantly (p<0.0001) thinner than the corresponding areas of the normal cornea.

CONCLUSION

The present study reveals the involvement of lamellae in the peripheral stroma in the pathogenicity of the KC cornea. The emergence of small undulations in the DM suggests that the formation of undulation might be starting from the DM.