RiTe conjugate mediated corneal collagen crosslinking, a novel therapeutic intervention for keratoconus - in vitro and in vivo study

Corneal collagen crosslinking (CXL) is an effective method to halt the disease progression of keratoconus, a progressive corneal dystrophy leading to cone shaped cornea. Despite the efficacy of standard protocol, the concerning step of this procedure is epithelial debridement performed to facilitate the entry of riboflavin drug. Riboflavin, a key molecule in CXL protocol, is a sparsely permeable hydrophilic drug in corneal tissues. The present study has employed cell penetrating peptide (CPP), Tat2, to enhance the penetration of riboflavin molecule, and thereby improve currently followed CXL protocol. This study demonstrates approximately two-fold enhanced uptake of CPP riboflavin conjugate, Tat2riboflavin-5'Phosphate (RiTe conjugate), both in vitro and in vivo. Two different CXL protocols (Epi ON and Epi OFF) have been introduced and implemented in rabbit corneas using RiTe conjugate in the present study. The standard and RiTe conjugate mediated CXL procedures exhibited an equivalent extent of crosslinking in both the methods. Reduced keratocyte loss and no endothelial damage in RiTe conjugate mediated CXL further ascertains the safety of the proposed CXL protocols. Therefore, RiTe conjugate mediated CXL protocols present as potential alternatives to the standard keratoconus treatment in providing equally effective, less invasive and patient compliant treatment modality.

Central Toxic Keratopathy After Collagen Cross-Linking: A Case Series

PURPOSE

The aim of this study was to report a case series of central toxic keratopathy (CTK) after collagen cross-linking (CXL) in keratoconus.

METHODS

This is a retrospective case series between January 2020 and September 2021. In this period, CXL was performed for progressive keratoconus in 964 eyes. CXL was performed using the epithelium-off accelerated protocol in all patients with a riboflavin soak time of 20 minutes and a UVA light exposure of 9 mW for 10 minutes using the Avedro KXL (Glaukos Inc, Aliso Viejo, CA) cross-linking system.

RESULTS

Twelve of 964 eyes (1.2%) developed CTK within 1 week of CXL. All patients presented with well-circumscribed, central disciform haze that was broader in the anterior stroma and narrower in the posterior stroma. We noted initial flattening in keratometry up to 3 months post-CXL in these patients, which gradually steepened over 12 months, but did not reach preoperative levels. We also noted exuberant flattening in pachymetry in the first 3 months, which improved over 12 months. There was a statistically significant decrease in pachymetry in patients who developed CTK at 3 and 12 months postoperatively when compared to patients who underwent CXL but did not develop CTK.

CONCLUSIONS

Several reports of CTK postrefractive surgery have been described previously. However, the association of CXL in the development of CTK has not been described previously. Here, we elucidated the clinical features of CTK after CXL and how it differs from corneal scarring or haze that occurs post-CXL.

Keratoconus in India: Clinical presentation and demographic distribution based on big data analytics

PURPOSE

This paper aims to describe the clinical presentation and demographic distribution of keratoconus (KCN) in India by analyzing the electronic medical records (EMR) of patients presenting at a multitier ophthalmology hospital network.

METHODS

This cross-sectional hospital-based study included the data of 2,384,523 patients presenting between January 2012 and March 2020. Data were collected from an EMR system. Patients with a clinical diagnosis of KCN in at least one eye were included in this study. Univariate analysis was performed to identify the prevalence of KCN. A multiple logistic regression analysis was performed using R software (version 3.5.1), and the odds ratios are reported.

RESULTS

Data were obtained for 14,749 (0.62%) patients with 27,703 eyes diagnosed with KCN and used for the analysis. The median age of the patients was 22 (inter-quartile range (IQR): 17-27). In total, 76.64% of adults (odds ratio = 8.77; P = <0.001) were affected the most. The majority of patients were male (61.25%), and bilateral (87.83%) affliction was the most common presentation. A significant proportion of the patients were students (63.98%). Most eyes had mild or no visual impairment (<20/70; 61.42%). Corneal signs included ectasia (41.35%), Fleischer ring (44.52%), prominent corneal nerves (45.75%), corneal scarring (13.60%), Vogts striae (18.97%), and hydrops (0.71%). Only 7.85% showed an association with allergic conjunctivitis. A contact lens clinic assessment was administered to 47.87% of patients. Overall, 10.23% of the eyes affected with KCN underwent a surgical procedure. the most common surgery was collagen cross-linking (8.05%), followed by deep anterior lamellar keratoplasty (1.13%) and penetrating keratoplasty (0.88%).

CONCLUSION

KCN is usually bilateral and predominantly affects males. It commonly presents in the second and third decade of life, and only a tenth of the affected eyes require surgical treatment.

Structure-Function Relationship in Keratoconus: Spatial and Depth Vision

Purpose

The purpose of this study was to determine changes in spatial and depth vision with increasing severity of keratoconus and to model the structure-function relationship to identify distinct phases of loss in visual function with disease severity.

Methods

Best-spectacle corrected, monocular high-contrast visual acuity, contrast sensitivity function (CSF) and stereoacuity of 155 cases (16-31 years) with mild to advanced bilateral keratoconus was determined using standard psychophysical tests. Disease severity was quantified using the multimetric D-index. The structure-function relationship was modeled using linear, positive exponential, negative exponential, and logistic nonlinear regression equations.

Results

The logistic regression model explained the highest proportion of variance for spatial vision, without bias in the residual plots (R2 ≥ 66%, P < 0.001). Visual acuity showed a distinct ceiling phase and a steeper loss rate with increasing D-index (1.8 units/D-index) in this model. The area under the CSF lacked this ceiling phase and had a shallower loss rate (0.28 units/D-index). Stereoacuity loss with D-index was poorly explained by all models tested (P ≤ 0.2). Cases with lower and bilaterally symmetric D-index had better stereoacuity (181.6-376 arc seconds) than those with higher D-index (>400 arc second); both were significantly poorer than controls (approximately 30 arc second).

Conclusions

Vision loss in keratoconus varies with the visual function parameter tested. Contrast sensitivity may be an earlier indicator of spatial vision loss than visual acuity. Depth perception is significantly deteriorated from very early stages of the disease.

Translational Relevance

The study outcomes may be used to forecast longitudinal vision loss in keratoconus and to apply appropriate interventions for timely preservation/enhancement of vulnerable visual functions.

Efficient reduction of the scrolling of Descemet membrane endothelial keratoplasty grafts by engineering the medium

The Descemet Membrane Endothelial Keratoplasty (DMEK) procedure for corneal transplantation is challenging due to the need to unscroll the donor graft within the recipient's eye. This process of unscrolling is complex, time-consuming, leads to a loss of endothelial cells and, most importantly, can negatively impact the graft's adhesion and integration with the host tissue after surgery. This problem is particularly evident when the graft is young. However, the physics behind this scrolling is not well understood, and therefore no sustainable solution is attained. Here, we propose that the concentration gradient of the medium used during transplant leads to a displacement gradient across the graft thickness, resulting in an out-of-plane folding or scrolling of the graft tissue. Using chitosan bilayer-based experimental models, it is experimentally demonstrated that this diffusion-coupled-deformation phenomenon can successfully explain why younger donor grafts tend to scroll tighter than older ones. Most importantly, we illustrate here through experiments that the medium can be engineered to reduce the scroll tightness and thus reduce the surgical inconveniences and improve post-transplant recovery. STATEMENT OF SIGNIFICANCE: This paper addresses a major issue that surgeons face while doing Descemet Membrane Endothelial Keratoplasty (DMEK) in unscrolling grafts during the graft insertion procedure. The currently used tapping method to unscroll the graft inside the patient's eye significantly reduces endothelial cell count, thus affecting its lifetime. Surprisingly, the physics behind graft scrolling is not well understood, so no sustainable solutions are proposed by the medical community. In this work, we present the underlying mechanism of DMEK graft scroll and illustrate experimentally the reason for scroll tightness through a chitosan bilayer based experiment model. Most importantly, we have successfully demonstrated that the preserving medium of the grafts can be engineered to reduce scroll tightness.

A goat eye, wet lab model for training in Descemet membrane endothelial keratoplasty

Here we describe a new, non-human, ex-vivo model (goat eye model) for training surgeons in DMEK surgeons. In a wet lab setting, goat eyes were used to obtain a pseudo-DMEK graft of 8 mm from the goat lens capsule that was injected into another goat eye with the same maneuvers described for human DMEK. The DMEK pseudo-graft can be easily prepared, stained, loaded, injected, and unfolded into the goat eye model reproducing the similar maneuvers used for DMEK in a human eye, except for the descemetorhexis, which cannot be performed. The pseudo-DMEK graft behaves similar to human DMEK graft and useful for surgeons to experience and understand steps of DMEK early in learning curve. The concept of a non-human ex-vivo eye model is simple and reproducible and obviates the need for human tissue and the issues of poor visibility in stored corneal tissue.

The Evolution of Diagnostics for Keratoconus: From Ophthalmometry to Biomechanics

PURPOSE

To enumerate the various diagnostic modalities used for keratoconus and their evolution over the past century.

METHODS

A comprehensive literature search including articles on diagnosis on keratoconus were searched on PUBMED and summarized in this review.

RESULTS

Initially diagnosed in later stages of the disease process through clinical signs and retinoscopy, the initial introduction of corneal topography devices like Placido disc, photokeratoscopy, keratometry and computer-assisted videokeratography helped in the earlier detection of keratoconus. The evolution of corneal tomography, initially with slit scanning devices and later with Scheimpflug imaging, has vastly improved the accuracy and detection of clinical and sub-clinical disease. Analyzing the alteration in corneal biomechanics further contributed to the earlier detection of keratoconus even before the tomographic changes became evident. Anterior segment optical coherence tomography has proven to be a helpful adjuvant in diagnosing keratoconus, especially with epithelial thickness mapping. Confocal microscopy has helped us understand the alterations at a cellular level in keratoconic corneas.

CONCLUSION

Thus, the collective contribution of the various investigative modalities have greatly enhanced earlier and accurate detection of keratoconus, thus reducing the disease morbidity.

Vitamin B12 deficiency in a large cohort of healthcare professionals across the network of an eyecare organization in India

Purpose:

To evaluate Vitamin B12 levels in healthcare professionals at a tertiary eyecare centre in India.

Methods:

This was a cross-sectional study conducted among healthcare professionals working at a tertiary eyecare centre in India. The sample included 2,374 employees. Chemiluminescent immunoassay method (reference range, 211–911 pg/ml) was used to assess serum vitamin B12 levels. Effect of age and gender was analyzed in vitamin B12 normal and vitamin B12 deficient groups. To evaluate risk factors, questions related to vitamin B12 deficiency were asked to the study participants in a survey.

Results:

The mean age of employees was 29.2 ± 0.7 years. Around 26% of them were vitamin B12 deficient. The proportion of males in the vitamin B12 deficient group (61.2%) was significantly higher (P < 0.0001) than that of the vitamin B12 normal group (44.9%). There was no effect of age on vitamin B12 levels in both vitamin B12 normal and vitamin B12 deficient groups. Mean vitamin B12 levels in males (289.1 ± 22.2 pg/ml) was significantly lower (P < 0.0001) than that of females (338.7 ± 30.0 pg/ml).

Conclusion:

This is the first such study on eyecare professionals. One-fourth of the eyecare professionals were vitamin B12 deficient. The proportion of males was higher in the vitamin B12 deficiency group. Males had lower vitamin B12 levels than females. Annual blood tests for vitamin B12 are recommended for timely diagnosis and management of vitamin B12 deficiency, particularly in males.

KEDOP: Keratoconus early detection of progression using tomography images

PURPOSE

To investigate a method to identification of early progression of keratoconus using deep learning neural networks.

METHODS

Retrospective evaluation of medical records of patients with progressive keratoconus and had more than one followup visits. Images extracted from the single scheimplug analyzer for analysis were captured during the patient visits. The baseline progression of keratoconus is detected by a change in flat or steep K of ≥1.0D which is labeled as keratometric progression (KP) and progression detected by image based deep learning convolutional neural network (CNN) models, is labeled as latent progression (LP). Patient data consisted of model data (385 eyes of 351patients) to train and test the learning models and prediction data (1331 eyes of 828 patients) to determine the LP based on the learning models.

RESULTS

The LP prediction model was able to identify progression at a mean of 11.1 months earlier than KP (p < 0.001). LP prediction model was able to identify progression earlier than KP irrespective of age category, gender, the severity of keratoconus, presenting visual acuity, astigmatism, and spherical equivalent (P < 0.001). When compared to the first visit the corrected distance visual acuity was more stable in 71% of the eyes at LP prediction visit compared to 50% at KP visit (p < 0.001).

CONCLUSION

Through this study, we propose a possible solution to address the shortcomings noted in the current approaches of detecting progression relying only on KP. Avoiding bias towards feature selection from tomography images as done in the current study aids in identifying very subtle changes on the images between visits.

Visual photosensitivity threshold and objective photosensitivity luminance in healthy human eyes assessed using an automated ocular photosensitivity analyser: a step towards translation of a clinical tool for assessing photophobia

PURPOSE

To evaluate the visual photosensitivity threshold and objective photosensitivity luminance in healthy eyes, thereby providing a normative dataset that will lead to a better understanding of diseases causing photophobia.

METHODS

This was a prospective cross-sectional study. Emmetropes whose visual acuity was better than 0.18 logMAR (6/9) with no other ocular abnormality were included. Headache Impact Test-6 and visual light sensitivity questionnaires were administered. Visual photosensitivity threshold was measured subjectively using the ocular photosensitivity analyser. Objective photosensitivity luminance was assessed manually by evaluating videos recorded using an infrared camera and noting the intensity of light at the first squeezing reflex.

RESULTS

Seventy five normal subjects (age range, 7-71 years) were included. Median age was 32.7 years (inter-quartile range, 20.3-47.9 years). Forty (53.3%) were males. Median Headache Impact Test score was 38 (inter-quartile range, 36-42) and visual light sensitivity questionnaire score was 11 (inter-quartile range, 8-15). Mean (standard deviation) right eye, left eye and binocular visual photosensitivity threshold was 3.34 (0.78), 3.33 (0.81) and 3.37 (0.78) loglux, respectively. There was a significant negative correlation of visual light sensitivity questionnaire scores with right eye, left eye and binocular visual photosensitivity thresholds, and positive correlation of age with binocular visual photosensitivity thresholds. Mean (standard deviation) right eye, left eye and binocular objective photosensitivity luminance was 3.25 (0.55), 3.35 (0.47) and 3.15 (0.52) loglux, respectively. Age was only positively correlated with binocular objective photosensitivity luminance, and there was no correlation between age and right eye or left eye objective photosensitivity luminance.

CONCLUSIONS

The study characterised, for the first time, objective photosensitivity luminance and established normative data for both visual photosensitivity threshold and objective photosensitivity luminance. The data will help in understanding the pathophysiology of diseases causing photophobia, monitoring the disease progression and evaluating treatment modalities.

Feasibility and Outcomes of Corneal Transplantation Performed at Rural Centers: An Extension of the Pyramidal Model of Enhanced Eye Care at Rural Outreach

PURPOSE

The aim of this study was to report on the feasibility of setting up a system of corneal transplants at rural outreach centers and report the outcomes of the first 111 cases.

METHODS

Retrospective analysis of the outcomes of corneal transplantation performed on patients with optical indications between March 2016 and September 2019 at 4 secondary (rural) centers. The centers are a part of a network in the pyramidal model developed by L V Prasad Eye Institute. The graft clarity and best-corrected visual acuity (BCVA) at 1-year follow-up were analyzed.

RESULTS

Of the 111 patients, 34.23% underwent penetrating keratoplasty and 65.77% endothelial keratoplasty. The mean age was 59.4 ± 15.0 (range-17-86 years); 47.75% were men and 52.25% were women. The indications for surgery were bullous keratopathy (54.05%), corneal scar/adherent leukoma (23.42%), and repeat grafts (13.51%). At the end of 1 year, 69.37% grafts remained clear. Factors associated with graft failure included poor socioeconomic status and graft infiltrate in both univariate and multivariate analyses. Surgical technique of endothelial keratoplasty was associated with failure on multivariate analysis only. Of the 77 eyes with clear corneal grafts at 1 year, the preoperative mean logMAR BCVA was 1.91 ± 0.06, which improved to 0.90 ± 0.08 postoperatively. Overall, 84.4% had preoperative BCVA of <3/60. Postoperatively, 40% had BCVA of 6/18 or better.

CONCLUSIONS

Our study showed that close to 70% grafts remained clear at 1 year. Graft failure was associated with poor socioeconomic status and graft infiltrates. This study established a viable model for delivery of corneal transplant surgery and care in a rural setup.

Year one of COVID-19 pandemic in India: Effect of lockdown and unlock on trends in keratoplasty at a tertiary eye centre

PURPOSE

To describe the impact of lockdown and unlock phases of the COVID-19 pandemic on keratoplasty trends at a tertiary eye care center in India.

METHODS

This cross-sectional hospital-based study included 6,277 patients presenting between March 25, 2017 and March 31, 2021. The data of the patients who underwent keratoplasty during the lockdown and unlock phases were compared with the respective periods in the previous three years before COVID-19.

RESULTS

During the year one of pandemic, there was a 29.46% decline in the total number of keratoplasty performed at the institute compared to previous year's annual numbers. The patients undergoing keratoplasty decreased by 90.28% (28/288) of pre-COVID-19 volumes during the lockdown phase. This was mainly because of a 40.6% reduction in the proportion of patients requiring interstate travel. There was complete recovery in the number of patients undergoing keratoplasty to 129.27% (184/142) of pre-COVID-19 volumes by March 2021. This gradual incremental trend was seen across all types of keratoplasty in Descemet stripping endothelial keratoplasty (135.29%), penetrating keratoplasty (117.6%), therapeutic keratoplasty (122.22%), anterior lamellar keratoplasty (150%), and Descemet membrane endothelial keratoplasty (141.18%) by March 2021 with the gradual ease of lockdown regulations. The eye bank affiliated to the institute saw a 55.44% decline in donor cornea collection and an increase in utilization rate from 58.12% in previous years to 83.78% in year one of the pandemic. The overall eye bank donor cornea collection recovered to 86.96% (627/721) and tissue utilization increased by 109.99% (455/414) by March 2021.

CONCLUSION

The first year of the COVID-19 pandemic saw an overall reduction of 29.46% of the patients undergoing keratoplasty at the institute. There was a gradual and incremental increase in all types of keratoplasty in the unlock phase, which surpassed the preceding years' monthly numbers in February and March.

Changes in post-keratoplasty astigmatism after suture removal: refraction vs tomography vs aberrometry

AIM

To analyse the changes in magnitude and orientation of astigmatism after suture removal (SR) in keratoplasty eyes as measured by refraction, tomography, and aberrometry.

METHODS

Twenty-six eyes of 25 patients after optical keratoplasty requiring SR to reduce the astigmatism during the follow-up period were prospectively included. Eyes with poor quality topography scans or if there were no sutures in the steepest semi meridian were excluded. Corrected distance visual acuity (CDVA), manifest refraction, corneal tomography and aberrometry were performed on all patients before and after SR.

RESULTS

The mean age of the patients was 40.8±14.4y. Penetrating keratoplasty was performed in 23 eyes (89%) and deep anterior lamellar keratoplasty was done in 3 eyes (11%). There was a statistically significant reduction in the magnitude of refractive, tomographic and aberrometry astigmatism after SR (P<0.001) at 2h after suture removal. The mean net reduction of the astigmatism was greater as measured by corneal tomography compared to refractive astigmatism (P<0.05). There was no statistically significant change in refractive astigmatism between 2h and 2mo after SR (P=0.55). Vector calculations demonstrated a greater amount of undercorrection in the tomography group and the rotational error was more towards counterclockwise direction. Mean monocular logMAR CDVA improved from 0.57 D to 0.49 D after SR (P=0.002).

CONCLUSION

The net reduction in the magnitude of astigmatism after SR is greater in the tomography and aberrometry groups. With one episode of SR, there is no difference in the aberration profile.

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.

CIRCLE Software for Management of Epithelial Ingrowth After SMILE

PURPOSE

To report a novel therapeutic use of CIRCLE software (Carl Zeiss Meditec) to manage visually significant epithelial ingrowth following small incision lenticule extraction surgery (SMILE).

METHODS

Case series.

RESULTS

In this case series, the authors describe three eyes with progressive and visually significant epithelial ingrowth following an uneventful SMILE procedure. The management of epithelial ingrowth following SMILE is challenging, given the small access incision to the interface and the risk of incomplete removal. All cases were successfully managed by converting the SMILE cap into a flap using the CIRCLE software, which provided the necessary access to the original SMILE interface. Once the flap was lifted, the epithelial in-growth was completely debrided from the underlying stroma and undersurface of the flap, followed by a thorough interface wash. Postoperative recovery was uneventful, with no recurrence noted in any of the eyes.

CONCLUSIONS

Use of CIRCLE software provides a novel and unique approach to successfully treating vision-threatening epithelial ingrowth after SMILE. [J Refract Surg. 2021;37(11):776-780.].

Complications and visual outcomes of cataract surgery in patients with pseudoexfoliation

PURPOSE

To compare outcomes of cataract surgery performed by ophthalmic trainees and consultants in patients associated with pseudoexfoliation (PXF) METHODS: Retrospective review of medical records of all patients with PXF who had undergone cataract surgery from January 2016 to December 2018 at L V Prasad Eye Institute, Hyderabad, India, were analysed RESULTS: A total of 914 eyes were included in the study; surgeries on 501 (54.8%) eyes with PXF were performed by trainees, while 413 (45.2%) were performed by consultants. Posterior capsule rupture (PCR) with vitreous loss (VL) occurred in significantly fewer eyes operated on by consultants (n = 8, 1.9%) than those operated on by trainees (n = 23, 4.5%) (p = 0.002). Eyes that underwent small incision cataract surgery (n = 100, 21.2%) had a significantly greater number of complications than those that underwent phacoemulsification (n = 31, 7.1%) (p = 0.00001). Multivariate logistic regression analysis shows that chances of a complication are higher when operated on by a trainee (OR = 1.59, 95% CI: 1.09-2.34, p = 0.02).The mean logMAR corrected distance visual acuity of patients one month post-surgery was significantly higher for patients in the consultant group (0.15 ± 0.3) than for those in the trainee group (0.2 ± 0.4) (p = 0.003).

CONCLUSION

Patients with PXF operated on by trainees for cataract had a relatively higher risk of developing PCR with VL and had poorer visual outcomes than those operated on by consultants.

Comparison of total keratometry with corneal power measured by optical low-coherence reflectometry and placido-dual Scheimpflug system

PURPOSE

To compare the total keratometry (TK) and astigmatism measurements in eyes with cataract using automated keratometry of swept-source optical coherence tomography (ss-OCT), optical low-coherence reflectometry (OLCR), simulated keratometry (SimK), and total corneal power (TCP) of combined placido-dual Scheimpflug imaging system.

SETTING

The study was conducted at LV Prasad Eye Institute, Hyderabad, India.

DESIGN

Retrospective evaluation of electronic medical records of patients who were evaluated for cataract surgery.

METHODS

Twenty-eight eyes of 28 patients were included in the study. All patients evaluated for cataract surgery underwent corneal power measurements using three devices: ssOCT, OLCR, and combined placido-dual Scheimpflug imaging were included in the study. Vector analysis was performed to evaluate corneal astigmatism and Bland-Altman analysis was conducted to evaluate the limits of agreement of similar parameters among devices.

RESULTS

The mean TK was statistically significantly different from the keratometry obtained from optical biometers and values measured by the Scheimpflug imaging system. The magnitude of mean difference was greater between TK and TCP (0.75 ± 0.25) compared to other variables. The mean difference in astigmatism between TK, ss-OCT-K (0.09 ± 0.12, p = 0.48), OCLR-K (0.10 ± 0.48, p = 0.91), and TCP (0.09 ± 0.47, p = 0.31) was not statistically significant but was statistically significant between TK and SimK values (0.23D ± 0.49D). The axis of orientation (<20°) of astigmatism was comparable (100%, 28 eyes) between two keratometry variables measured by ss-OCT.

CONCLUSION

There appears to be a greater correlation of automated keratometry, and TK values obtained from ss-OCT compared to other variables studied. The measurements from TK, Simk, and TCP cannot be used interchangeably.

Phototherapeutic keratectomy: Indications, methods and decision making

Phototherapeutic keratectomy (PTK) involves treating anterior corneal lesions by superficial corneal ablation using an excimer laser (193 nm). Some of the commonly treated conditions include recurrent corneal erosions (RCE), corneal dystrophies, spheroidal degeneration, keratoconus, and corneal scars. We discuss various techniques of PTK including large area PTK, focal PTK, and multifocal PTK and alternatives to PTK. Masking agents like hyaluronate, methylcellulose, and dextran are recommended to help achieve a better outcome when ablating irregular corneal surfaces. Antifibrotic agents like mitomycin C reduce the chances of recurrence of the disease, apart from minimizing the postoperative scarring. Some of the complications include induced hyperopia and irregular astigmatism, haze, recurrence, and corneal thinning. However, earlier postoperative recovery, possibility of a repeat procedure, and ability to control the depth of ablation make PTK a promising, minimally invasive alternative to keratoplasty in cases with anterior corneal pathologies.

Response of L V Prasad Eye Institute to COVID-19 outbreak in India: experience at its tertiary eye care centre and adoption to its Eye Health Pyramid

AIM

To summarize the experience of response to COVID-19 outbreak at a tertiary eye care institute and its network of health facilities in India.

METHODS

Our responses are based on the principles of social distancing, hand hygiene, respiratory etiquettes, surface disinfection protocol, and rational use of appropriate personal protective equipment (PPE). We describe our response in terms of administrative controls, clinical protocols, staff protection, environmental controls, and social distancing measures. We also discuss our communication strategies and monitoring systems, to ensure compliance to protocols.

RESULTS

Administrative control is mainly related to formation of task force and its functions. Clinical protocols are related to patient triaging methods and clinical examination guidelines in Outpatient, Inpatient and Operating Room. Staff protection is focused on training staff on the protocols to be followed in hospital as well as at home, and use of PPE. Environmental protocol is focused on cleaning and disinfectant methods to be used in the hospital. In addition, there are systems for communication as well as monitoring compliance to protocols.

CONCLUSION

We hope that these protocols and our experience would help the ophthalmic community globally and serve as a guide to protect ophthalmologists and ophthalmic care personnel, and their patients across the world.

Early results of circularity and centration of capsulotomy prepared by three different methods

AIM

To compare the difference of capsulotomy produced by precision pulse capsulotomy (PPC), manual (M-CCC), and femtosecond laser assisted capsulotomy (FLAC) in relation to intraocular lens (IOL) centration, circularity and its effect on visual outcomes.

METHODS

Prospective, non-randomized comparative study conducted at LV Prasad Eye Institute, Hyderabad, India. Sixty eyes of 52 patients were grouped into 3 (FLAC, PPC and M-CCC) based on capsulotomy techniques used. Twenty consecutive eyes with uneventful phacoemulsification and with no comorbidities affecting the capsulotomy or visual outcome were included in each group. The main outcome measure was IOL centration in relation to capsulotomy and pupil. Secondary outcome measures were post-operative visual acuity, manifest refraction and aberration profile between groups.

RESULTS

At 5wk the visual, refractive outcomes and endothelial cell density were comparable between the 3 groups. The median circularity index of FLAC was statistically significantly different to M-CCC or PPC (1-10) groups (P<0.01) but PPC (11-20) was comparable to FLAC. Decentration of IOL center in relation to capsulotomy was seen only between the PPC (1-10) group and FLAC group (P=0.02). The IOL was well centered in relation to the pupil in all the groups (P=0.46). The quality of vision parameters like the higher order aberrations, spherical aberration, coma, trefoil, modular transfer function, and Strehl ratio were comparable between the groups.

CONCLUSION

Our study shows that despite differences in the morphology of capsulotomy produced by PPC, M-CCC, FLAC a well-centered IOL can be achieved. The measured capsular morphology parameters do not affect visual outcomes.

Short-term changes in topometric indices after discontinuation of rigid gas permeable lens wear in keratoconic eyes

Purpose:

To estimate the time taken for topometric indices to stabilize in keratoconic corneas following cessation of habitual RGP contact lens wear.

Methods:

A total of 29 eyes of 20 patients, diagnosed with mild to severe keratoconus were included in this prospective observational study. All patients were experienced RGP contact lens wearers (either conventional RGP or Rose K2 lens) with each patient having used these lenses for at least a year. Corneal topography was performed immediately following discontinuation of habitual contact lens wear at baseline and each of four consecutive visits, 1-week apart.

Results:

An overall reduction in the keratometry and thickness values were noted on tomography immediately following cessation of contact lens wear and these indices increased significantly in the 1^st week (P < 0.001). Consecutive visits following the first visit did not show any significant change in the topometric parameters (P > 0.05). Subgroup analysis revealed a similar trend in eyes with “severe” keratoconus and in eyes fitted with the “three-point touch” philosophy. However, eyes with “mild-moderate” keratoconus and those fitted with “apical clearance” fitting philosophy showed marginal differences even within the 1-week period of lens cessation.

Conclusion:

Maximum changes in keratometry and pachymetry values following discontinuation of RGP lens wear stabilize within the 1^st week of cessation of rigid lens wear in a keratoconic cornea. These changes were more pronounced in patients with severe keratoconus and those with an apical bearing fit. This information would be useful for practitioners to assess the progression of keratoconus in RGP lens users before collagen cross-linking.

Outcomes of rebubbling for graft detachment after Descemet's stripping endothelial keratoplasty or Descemet's stripping automated endothelial keratoplasty

Purpose

To study the outcomes of rebubbling for graft detachment after Descemet's stripping endothelial keratoplasty (DSEK) or Descemet's stripping automated endothelial keratoplasty (DSAEK).

Methods

From 2260 eyes that underwent DSEK or DSAEK from July 2008 to June 2015, 80 eyes of 80 patients developed graft detachment and were retrospectively reviewed. Host-related, surgery-related and donor-related factors that have a bearing on graft adhesion were looked at retrospectively, and eventual outcomes after rebubbling procedure were studied.

Results

Successful attachment was observed in 77 (96.25%) eyes and clear grafts were achieved in 55 (68.75%) eyes, while 25 (31.25%) eyes had graft failure. The uncorrected and best-corrected distance visual acuities significantly improved from 1 month to 3 months post-operatively and remained stable till 12 months of follow-up. Three lenticules that failed to attach with the first rebubbling procedure underwent a second rebubbling, two underwent a repeat DSEK with good outcomes and four underwent penetrating keratoplasty. On evaluating possible risk factors for graft failure, lower donor endothelial cell density was found to be a significant factor (P = 0.03). The median graft survival following rebubbling was 30 months.

Conclusion

Rebubbling procedure in detached grafts after DSEK or DSAEK can reattach the lenticule in 96% of eyes in immediate post-operative period and the majority of the grafts remained clear on long-term follow-up with a median graft survival period of 2.5 years.

A new normal with cataract surgery during COVID-19 pandemic

Cataract is the second leading cause of preventable blindness on the globe. Several programs across the country have been running efficiently to increase the cataract surgical rates and decrease blindness due to cataract. The current COVID-19 pandemic has led to a complete halt of these programs and thus accumulating all the elective cataract procedures. At present with the better understanding of the safety precautions among the health care workers and general population the Government of India (GoI) has given clearance for functioning of eye care facilities. In order to facilitate smooth functioning of every clinic, in this paper, we prepared preferred practice pattern based on consensus discussions between leading ophthalmologists in India including representatives from major governmental and private institutions as well as the All India Ophthalmological Society leadership. These guidelines will be applicable to all practice settings including tertiary institutions, corporate and group practices and individual eye clinics. The guidelines include triage, use of personal protective equipment, precautions to be taken in the OPD and operating room as well for elective cataract screening and surgery. These guidelines have been prepared based on current situation but are expected to evolve over a period of time based on the ongoing pandemic and guidelines from GoI.

Tele-consultations and electronic medical records driven remote patient care: Responding to the COVID-19 lockdown in India

Purpose:

To describe the experience of tele-consultations addressed at the centre of excellence of a multi-tier ophthalmology hospital network in India during the ongoing novel coronavirus (COVID-19) lockdown.

Methods:

This cross-sectional hospital-based study included 7,008 tele-consultations presenting between March 23^rd and April 19^th 2020. A three-level protocol was implemented to triage the calls. The data of patient queries were collected using a Google Form/Sheets and the tele-calls were returned using the patient information retrieved from the electronic medical record system.

Results:

Overall, 7,008 tele-calls were addressed, of which 2,805 (40.02%) patients where a clinical-related query was answered were included for analysis. The most common queries were related to redness/pain/watering/blurring of vision (31.52%), closely followed by usage of medications (31.05%). The majority of the queries were directed to the department of cornea (34.15%), followed by retina (24.74%). Less than one-fifth of the patients were from the lower socio-economic class (16.08%) and one-fourth were new patients (23.96%). The most common advice given to the patient was related to management of medications (54.15%) followed by appointment related (17.79%). Emergency requests requiring further evaluation by an ophthalmologist accounted for a small percentage (16.36%) of patients.

Conclusion:

Tracking of tele-consultations and access to patient information from the electronic medical records enabled a timely response in an ongoing lockdown due to the COVID-19 pandemic. The current experience provided valuable insights to the possibility of managing patient follow-up visits remotely in the future.

Micrococcus keratitis following microkeratome-assisted laser in situ keratomileusis

We hereby report a case of infectious keratitis after laser in situ keratomileusis (LASIK) caused by Micrococcus luteus, a commensal, managed successfully in a nonimmunocompromised individual. A 25-year-old healthy male underwent uneventful bilateral simultaneous LASIK for myopia using disposable blades. Postoperatively, topical antibiotic and steroids were advised; he discontinued antibiotic on his own after using for a day. On the 5^th postoperative day, he had pain, redness, decreased vision, and white spot in the left eye (LE) for 1-day duration. Uncorrected visual acuity (UCVA) of LE reduced to 20/80 from postoperative 20/20. Slit-lamp biomicroscopy revealed tiny infiltrate in the interface with reticular haze in the flap and stroma. Gram-positive cocci in pairs and tetrads were found on corneal smears that were collected after lifting the flap from infiltrate, stromal bed, and undersurface of the flap. M. luteus was isolated on culture. The infiltrate resolved with scarring with intensive topical antibiotics. UCVA was 20/25. To the best of our knowledge, this is a first case report of post-LASIK infectious keratitis caused by M. luteus.

Refractive surprise: twice the SMILE

A 35-year-old man presented with decreased vision in his left eye following small incision lenticule extraction (SMILE) surgery. The refractive error after surgery was nearly twice his preoperative refractive error in the left eye. The patient was diagnosed as having a retained lenticule after SMILE surgery, which was folded on itself and was successfully managed by conversion to a flap. Postoperatively, the patient maintained good uncorrected visual acuity and a low refractive error, with the best spectacle corrected acuity of 20/20.

Correction: Etiology and Management of Raised Intraocular Pressure following Posterior Chamber Phakic Intraocular Lens Implantation in Myopic Eyes

[This corrects the article DOI: 10.1371/journal.pone.0165469.].

Etiology and Management of Raised Intraocular Pressure following Posterior Chamber Phakic Intraocular Lens Implantation in Myopic Eyes

AIM

To evaluate the etiology and management of elevated intraocular pressure (IOP) following posterior chamber phakic implantable collamer lens (ICL) surgery.

METHODS

Between 2009 and 2015, 638 eyes of 359 subjects with refractive myopia, underwent V4b and V4c (CentraFLOW) model ICL implantation. Ocular hypertension (OHT) was defined as IOP of ≥ 22 mm Hg on two separate occasions and elevated IOP with corresponding optic disc or visual field damage was defined as glaucoma.

RESULTS

Elevated IOP ≥ 22 mm Hg was noted in 33 eyes of 30 subjects (33/638; 5.17%). Median age of subjects with raised IOP was 26 years (Inter quartile range (IQR):22, 29) and median refarctive error was -16 diopters (-19.5, -13). The median follow up was 7.8 months (IQR:0.3, 17.6) and median time for postoperative IOP rise was 12 days, (IQR:2, 24). The various etiologies for elevated IOP were steroid response in 21 eyes (64%; 10 eyes with V4b, 11 eyes with V4c), retained viscoelastic in 5 eyes (15%) (3 with V4b, 2 with V4c), pupillary block in four eyes (12%; 3 with V4b, 1 with V4c), malignant glaucoma in one eye (3%, V4b), and missed pre-existing Juvenile open angle glaucoma (JOAG) in two eyes (6% with V4b). Elevated IOP in 31 eyes resolved with conservative management. One eye (centraFLOW design) with central aquaport block by viscoelastic, needed AC wash and one eye with malignant glaucoma needed parsplana vitrectomy and hyaloidotomy. Ten eyes required longterm (>2 months) antiglaucoma medications (AGM) for IOP control. Except the two eyes with JOAG, none had disc and field damage.

CONCLUSION

In our series, OHT was seen in 4.85% and glaucoma in 0.3% eyes that underwent V4b and V4c model ICL implantation. Multiple etiologies were noted and steroid induced ocular hypertension was the most common cause of elevated IOP followed by retained viscoelastic and pupillary block. One third of these eyes required longterm AGM for IOP control.

Outcomes of Repeat Keratoplasty for Failed Therapeutic Keratoplasty

PURPOSE

To analyze clinical outcomes of repeat optical penetrating (PK) or endothelial keratoplasty (EK) after failed therapeutic keratoplasty (TPK).

DESIGN

Retrospective consecutive, comparative, interventional case series.

METHODS

setting: LV Prasad Eye Institute, Hyderabad, India.

STUDY POPULATION

Patients aged >18 years who underwent a repeat PK or EK following a failed TPK with a follow-up of at least 1 year were included. Patients with culture-negative ulcers, viral etiology, coexistent ocular surface disease, and multiple grafts were excluded from the study.

INTERVENTION

PK or EK for failed TPK.

MAIN OUTCOME MEASURE

Corrected distance visual acuity at 1 year follow-up. secondary outcome measure: Graft clarity.

RESULTS

One hundred twelve eyes (67 PK, 45 EK) were included in the study. The PK group had a significantly higher number of cases with high-risk features prior to regraft. Improvement in visual acuity in each of the types of grafts was statistically significant (P < .01), but there was no difference between the 2 groups at 1 year postoperatively. A statistically significant proportion of grafts regained graft clarity after regrafting in the PK group (P < .01) but not in the EK group (P = .205) at 1 year postoperatively. Endothelial rejection rates were higher in the PK group. Subgroup analysis showed that eyes that had PK or EK for failed TPK conducted for Aspergillus keratitis showed better outcomes in terms of graft clarity. Kaplan-Maier (KM) survival analysis for graft clarity showed cumulative survival of 50% at 5 years. The survival using the KM curve was not statistically different between the 2 groups (P = .33).

CONCLUSION

This study shows that visual rehabilitation with relatively good functional outcomes can be achieved by performing repeat PK or EK in patients after failed TPK.

Endothelial Keratoplasty: A Review of Indications at a Tertiary Eye Care Centre in South India

PURPOSE

The objective of this study was to review the indications for endothelial keratoplasty (EK) performed at a tertiary eye care center in South India between January 2007 and December 2011.

DESIGN

This was a hospital-based, cross-sectional study.

METHODS

A retrospective analysis of the indications of EK surgeries between January 2007 and December 2011 was done using the Corneal Tissue Utilization Register available with the Ramayamma International Eye Bank, L. V. Prasad Eye Institute, Hyderabad, India. Additional data such as age, sex, and socioeconomic status of the transplant recipients were obtained from the Medical Records Department, L. V. Prasad Eye Institute.

RESULTS

Data were available for 1048 EK surgeries performed on 978 patients. The number of EK surgeries increased from 40 in 2007 to 232 in 2011. The median age of the patients was 58 years (range, 5 months to 92 years) with a male-female ratio of 1.5:1. The clinical indications for EK were pseudophakic corneal edema (47.9%), failed prior penetrating keratoplasty (20.0%), Fuchs endothelial corneal dystrophy (10.8%), aphakic corneal edema (6.0%), failed prior EK (4.3%), congenital hereditary endothelial dystrophy (1.8%), Descemet membrane detachment/tear (1.6%), iridocorneal endothelial syndrome (1.4%), and corneal edema due to other reasons (6.2%).

CONCLUSIONS

The most common indication for EK was pseudophakic corneal edema, followed by post-penetrating keratoplasty graft failure and Fuchs endothelial corneal dystrophy.

Cross-linking for microbial keratitis

The success of collagen cross-linking as a clinical modality to modify the clinical course in keratoconus seems to have fueled the search for alternative applications for this treatment. Current clinical data on its efficacy is limited and laboratory data seems to indicate that it performs poorly against resistant strains of bacteria and against slow growing organisms. However, the biological plausibility of crosslinking and the lack of effective strategies in managing infections with these organisms continue to focus attention on this potential treatment. Well-conducted experimental and clinical studies with controls are required to answer the questions of its efficacy in future.

The use of Bowman's layer vertical topographic thickness map in the diagnosis of keratoconus

PURPOSE

To evaluate the use of Bowman's layer (BL) vertical topographic thickness maps in diagnosing keratoconus (KC).

DESIGN

Prospective, case control, interventional case series.

PARTICIPANTS

A total of 42 eyes: 22 eyes of 15 normal subjects and 20 eyes of 15 patients with KC.

INTERVENTION

Bowman's layer 2-dimensional 9-mm vertical topographic thickness maps were created using custom-made ultra high-resolution optical coherence tomography.

MAIN OUTCOME MEASURES

Bowman's layer average and minimum thicknesses of the inferior half of the cornea, Bowman's ectasia index (BEI; defined as BL minimum thickness of the inferior half of the cornea divided by BL average thickness of the superior half of the cornea multiplied by 100), BEI-Max (defined as BL minimum thickness of the inferior half of the cornea divided by BL maximum thickness of the superior half of the cornea multiplied by 100), keratometric astigmatism (Ast-K) of patients with KC, and average keratometric (Avg-K) readings.

RESULTS

In patients with KC, BL vertical thickness maps disclosed localized relative inferior thinning of the BL. Inferior BL average thickness (normal = 15±2, KC = 12±3 μm), inferior BL minimum thickness (normal = 13±2, KC = 7±3 μm), BEI (normal = 91±7, KC = 48±14), and BEI-Max (normal = 75±8; KC = 40±13) all showed highly significant differences in KC compared with normal subjects (P< 0.001). Receiver operating characteristic (ROC) curve analysis showed excellent predictive accuracy for BEI and BEI-Max with 100% sensitivity and specificity (area under the curve [AUC] of 1) with cutoff values of 80 and 60, respectively. The AUC of inferior BL average thickness and minimum thickness were 0.87 and 0.96 with a sensitivity of 80% and 93%, respectively, and a specificity of 93% and 93%, respectively. Inferior BL average thickness, inferior BL minimum thickness, BEI, and BEI-Max correlated highly to Ast-K (R = -0.72, -0.82, -0.84, and -0.82, respectively; P< 0.001) and to Avg-K (R = -0.62, P< 0.001; R = -0.59, P = 0.001; R = -0.60, P< 0.001; and R = -0.59, P = 0.001, respectively).

CONCLUSIONS

Bowman's layer vertical topographic thickness maps of patients with KC disclose characteristic localized relative inferior thinning. Inferior BL average thickness, inferior BL minimum thickness, BEI, and BEI-Max are qualitative and quantitative indices for the diagnosis of KC that accurately correlate with the severity of KC. In our pilot study, BEI and BEI-Max showed excellent accuracy, sensitivity, and specificity in the diagnosis of KC.

Corneal topography and corneal thickness in children

PURPOSE

To evaluate the corneal topography, thickness, and elevation (anterior and posterior corneal surface) in children.

METHODS

One hundred eyes of 100 patients with a mean ± standard deviation age of 10.6 ± 2.7 years (range: 5 to 15 years) were imaged. The corneal elevation maps were classified into regular ridge, irregular ridge, incomplete ridge, island, and unclassified patterns.

RESULTS

Mean simulated keratometry (Sim K) astigmatism was -0.69 ± 0.35 diopters (D) with mean maximum and minimum keratometry (K) of 44.26 ± 1.55 and 43.56 ± 1.57 D, respectively. Mean astigmatism and refractive power in the 3- and 5-mm zones was 0.64 ± 0.36, 43.85 ± 1.53 and 0.78 ± 0.5, 43.41 ± 1.48, respectively. The thinnest site on the cornea had an average thickness of 540 ± 34.03 μm. This site was most commonly located in the inferotemporal quadrant in 61% of eyes, followed by the superotemporal quadrant in 31%. Among the nine regions of the cornea evaluated, the central cornea had the lowest average thickness of 540 ± 34.03 μm and the superonasal cornea had the greatest average thickness of 628 ± 38.94 μm. The most common anterior corneal elevation pattern was the incomplete ridge (52%), followed by the island pattern. The incomplete ridge was most commonly observed on the posterior corneal elevation map (35%).

CONCLUSIONS

These results provide normal standards for elevation and curvature topography and corneal thickness in children. These data may prove useful as a reference for future comparative studies of different corneal diseases in children.

Complications of femtosecond laser-assisted re-treatment for residual refractive errors after LASIK

PURPOSE

To report complications of femtosecond laser-assisted re-treatment by the creation of side cuts within the old flaps for residual refractive error after primary LASIK in two patients.

METHODS

Case report.

RESULTS

Three eyes of two patients had complications with a circumferential sliver of stromal tissue displaced during surgery due to overlap of old and new side cuts. The displaced tissue was repositioned and corneal anatomy was restored. Two of three eyes demonstrated improvement in the uncorrected visual acuity, whereas one eye lost two lines of corrected visual acuity due to loss of tissue at side cut resulting from flap manipulation, which was done at 1 week.

CONCLUSIONS

These cases demonstrate a complication of femtosecond laser-enabled side-cut for LASIK enhancement and factors that may lead to this complication and precautions to avoid it.

Management, clinical outcomes, and complications of shield ulcers in vernal keratoconjunctivitis

PURPOSE

To assess the clinical outcomes and complications of shield ulcers by various treatment methods.

DESIGN

Retrospective, interventional case series.

METHODS

setting: Cornea and anterior segment service of L.V. Prasad Eye Institute, India. study population: One hundred ninety-three eyes of 163 patients clinically diagnosed with vernal keratoconjunctivitis and shield ulcers. intervention: The treatment algorithm was based on the Cameron clinical grading of shield ulcers. Grade 1 ulcers received medical therapy alone. Grade 2 and grade 3 ulcers received either medical therapy alone or medical therapy combined with debridement, amniotic membrane transplantation (AMT), or both. main outcome measures: Re-epithelialization time and best-corrected visual acuity.

RESULTS

Grade 1 ulcers were seen in 71 (37%) eyes, grade 2 ulcers were seen in 79 (41%) eyes, and grade 3 ulcers were seen in 43 (22%) eyes. In the grade 1 group, re-epithelialization was seen in 67 (94%) eyes. In the grade 2 group, re-epithelialization was seen in 36 (88%) eyes that received medical treatment, in 20 (95%) eyes that underwent debridement, and in 17 (100%) eyes that underwent AMT. In the grade 3 group, re-epithelialization was seen in only 1 (1.7%) eye that received medical treatment, whereas it was seen in all eyes that underwent debridement and AMT. The mean best-corrected visual acuity after re-epithelialization of the shield ulcer was 20/30, 20/30, and 20/40 in the grade 1, grade 2, and grade 3 groups, respectively. Recurrence and secondary bacterial keratitis were seen in 28 (14.5%) and 20 (10%) eyes, respectively.

CONCLUSIONS

Grade 1 shield ulcers respond well to medical therapy alone, whereas grade 2 ulcers occasionally may require additional debridement or AMT. Grade 3 ulcers, however, largely are refractory to medical therapy and require debridement and AMT for rapid re-epithelialization.

Deep anterior lamellar keratoplasty in children

PURPOSE

To evaluate the outcomes of deep anterior lamellar keratoplasty (DALK) in children.

DESIGN

Retrospective interventional case series.

METHODS

setting: Institutional, L.V. Prasad Eye Institute, a tertiary care center in south India. study population and intervention: All children less than 16 years of age undergoing DALK from January 2003 to January 2011. main outcome measure: Visual outcome and complications.

RESULTS

Twenty-six eyes of 26 children (13 male and 13 female) with a mean age of 7.82 ± 4.64 years underwent DALK for keratoconus (8), microbial keratitis (6), corneal scar (6), corneal keloid (3), chemical injury with limbal stem cell deficiency (2), and dermoid (1). Big bubble was achieved in 5 eyes, while manual dissection was done in 21. Follow-up ranged from 1 week to 7.3 years. Seventeen patients with a minimal follow-up of 6 months were evaluated for visual outcomes. Final vision varied from counting fingers to 20/20 (mean sphere 2.32 diopters, mean cylinder -2.5 diopters). Complications encountered were suture-related graft infiltrate (3), graft dehiscence (3), and Descemet membrane detachment (2).

CONCLUSIONS

DALK is a feasible option in children with stromal corneal pathology. It offers advantages in the form of lower risk of graft rejection. However, the risk of complications such as suture-related infections and graft dehiscence persists even in these cases.

Corneal thickness in keratoconus: comparing optical, ultrasound, and optical coherence tomography pachymetry

PURPOSE

To compare the central and peripheral pachymetry measurements determined using Orbscan IIz (Bausch & Lomb, Rochester, NY), Visante optical coherence tomography (OCT; Carl Zeiss Meditec, Dublin, CA), and RTVue OCT (Oculus Technologies, Wynwood, WA) with ultrasound pachymetry in eyes with established keratoconus and to evaluate the agreement between them.

DESIGN

Evaluation of diagnostic technologies.

PARTICIPANTS

One hundred six eyes of 67 consecutive patients with a clinical diagnosis of keratoconus ranging in age from 12 to 40 years.

METHODS

Central corneal thickness (CCT) was determined by all the 4 techniques. Peripheral corneal thicknesses were determined using Orbscan IIz, Visante OCT, and RTVue at 8 points (superior, inferior, temporal, nasal, superior-temporal, inferior-temporal, superior-nasal, and inferior-nasal) all in the 5.0- to 7.0-mm arcuate zone.

MAIN OUTCOME MEASURES

Central and peripheral keratoconus thickness.

RESULTS

Ultrasound pachymetry determined significantly higher CCT values than Orbscan IIz (P<0.001), Visante (P<0.001), and RTVue (P = 0.037), with a mean ± standard deviation difference of 14±3 μm, 13±2 μm, and 5±3 μm, respectively. The mean CCT difference was minimal (1±3 μm; P = 0.69) between the Orbscan IIz and Visante. A strong correlation was found (r>0.80) between all the CCT measurement techniques. Orbscan IIz significantly overestimated the peripheral thickness compared with the rest, and the mean differences ranged between 21 and 60 μm. Mean peripheral thickness differences between RTVue and Visante OCT always remained less than 20 μm. Weak correlations and larger limits of agreement were found between the techniques in thinner and peripheral zones.

CONCLUSIONS

Orbscan IIz, Visante, RTVue, and ultrasound pachymetry show high correlation, although Orbscan IIz and Visante significantly underestimated CCT measurements compared with ultrasound pachymetry in keratoconus. Orbscan IIz significantly overestimated peripheral corneal thickness compared with RTVue and Visante.