Visual and refractive outcomes of posterior chamber phakic IOL in stable keratoconus

Keratoconus: imaging modalities and management

Background

Keratoconus (KCN) is characterized by gradual thinning and steepening of the cornea, which can lead to significant vision problems owing to high astigmatism, corneal scarring, or even corneal perforation. The detection of KCN in its early stages is crucial for effective treatment. In this review, we describe current advances in the diagnosis and treatment of KCN.

Methods

This narrative review focuses on recent advancements in the diagnosis and treatment of KCN, especially evolving approaches and strategies. To ensure the inclusion of the most recent literature, relevant publications discussing advanced imaging techniques and treatment options for KCN were extensively gathered from the PubMed/MEDLINE and Google Scholar databases. The following index terms and keywords were used for the online search: keratoconus, diagnosis of keratoconus, advances in the diagnosis of keratoconus, topography or tomography, anterior segment optical coherence tomography, treatment of keratoconus, advances in the treatment of keratoconus, collagen crosslinking, intrastromal ring, keratoplasty, and new techniques in keratoconus.

Results

Various screening methods such as corneal topography, tomography, anterior segment optical coherence tomography, and assessment of corneal biomechanics have been developed to identify KCN in its early stages. After diagnosis, KCN management focuses on preventing disease progression. Corneal collagen crosslinking is a minimally invasive treatment that can slow or stop the progression of the condition. Recent research has also explored the use of copper sulfate eye drops (IVMED-80) as a noninvasive treatment to prevent the progression of KCN. Current treatment options for visual improvement include scleral lenses, intracorneal ring segments, corneal allogeneic intrastromal ring segments, and deep anterior lamellar keratoplasty. Recently, novel alternative procedures, such as isolated Bowman layer transplantation, either as a corneal stromal inlay or onlay, have demonstrated encouraging outcomes. Artificial intelligence has gained acceptance for providing best practices for the diagnosis and management of KCN, and the science of its application is contentiously debated; however, it may not have been sufficiently developed.

Conclusions

Early detection and advancements in screening methods using current imaging modalities have improved diagnosis of KCN. Improvement in the accuracy of current screening or diagnostic tests and comparison of their validities are achievable by well-designed, large-scale, prospective studies. The safety and effectiveness of emerging treatments for KCN are currently being investigated. There is an ongoing need for studies to track progress and evaluate clinicians' knowledge and practices in treating patients with KCN. Artificial intelligence capabilities in management approach considering the currently available imaging modalities and treatment options would best benefit the patient.

Spherical equivalent pre- and post-implantable collamer lens implantation in patients with myopia, hyperopia, and stable keratoconus

PURPOSE

Refractive errors are common in Saudi Arabia and keratorefractive surgeries are usually done to correct them. However, not all patients are fit and complications postoperatively are a concern. Implantable collamer lens (ICL) implantation can be used for patients who are not fit for keratorefractive surgeries. ICL can also be used for keratoconus. We elected to evaluate the outcomes of patients who had ICL implantation for refractive errors or keratoconus.

METHODS

We retrospectively reviewed patients aged between 21 and 45 years old, who attended the anterior segment clinic at King Khaled Eye Specialist Hospital and who had spherical equivalent (SE) ranging between (+16 to -23 diopters), and had ICL implantation between February 2015 and September 2017. The SE was documented before and after the surgery. Depending on the SE, patients were divided into two groups (myopia and hyperopia). Statistical analysis was done to evaluate the change in mean SE before and after surgery for patients.

RESULTS

We identified 169 eyes and 155 (92%) were myopic before the surgery. Before surgery, the mean SE was -8.6 and the standard deviation (SD) was 4.4. Only 14 eyes (8%) were hyperopic before the surgery with a mean SE of +5.5 and SD of 4.8. The difference in the mean of SE between after and before the surgery for myopic eyes was statistically significant (mean difference: 7.8, SD: 5, P < 0.0001). The difference in the mean of SE between post- and pre-operatively was also significant for hyperopic eyes (mean difference: -6.1, SD: 5.2, P = 0.0007). In 32 eyes with keratoconus, the mean SE before surgery was -7.9 with an SD of 4.1. For the keratoconus eyes, the mean difference of SE between after and before surgery was statistically significant as the mean difference in SE was 7.2 with an SD of 4.6 (P < 0.0001).

CONCLUSION

The effect of ICL implantation was significant in improving the SE for myopic, hyperopic, and keratoconus eyes.

Iatrogenic Keratectasia after Refractive Surgery - Causes, Prophylaxis, Therapy

Iatrogenic keratectasia is induced thinning and protrusion of the cornea after laser refractive surgery. Known risk factors include an excessively thin postoperative residual stromal bed, a thicker flap, or preoperatively undetected evidence of preexisting subclinical keratoconus. The rate of post-refractive ectasia in eyes without identifiable preoperative risk factors is 20 per 100 000 eyes for photorefractive keratectomy, 90 per 100 000 eyes for laser in situ keratomileusis, and 11 per 100 000 eyes for small incision lenticule extraction. Traditional screening tools for preoperative risk include the ectasia risk score system and percentage of tissue alteration. More recent methods include corneal elastography and epithelial mapping, in addition to Artificial Intelligence methods for data analysis. Therapy includes contact lenses, cross-linking, implantation of intracorneal ring segments, penetrating or lamellar keratoplasty, and, in early studies, implantation of corneal lenticules.

Indications for exchange or explantation of phakic implantable collamer lens with central port in patients with and without keratoconus

AIM

To evaluate the causes of phakic implantable collamer lens (ICL) exchange/explantation in patients with and without keratoconus (KC) at two tertiary hospitals in Riyadh, Saudi Arabia.

METHODS

A retrospective chart review of all patients who underwent ICL (model V4c with central port) exchange/explantation was performed using the electronic medical record systems. All available preoperative and postoperative data were documented for each patient.

RESULTS

Over 7y, 2283 ICL implantation procedures were performed; 46 implants (2%) required exchange (21 implants)/explantation (25 implants), of which 14 cases (30.4%) were patients with KC. Indications for ICL exchange/explantation in non-KC group were vault measurement, cataract formation, increased intraocular pressure, inaccurate refraction, and patient dissatisfaction in 22 (68.75%), 4 (12.5%), 3 (9.37%), 2 (6.25%), and 1 (3.12%) case, respectively. The most common indication for ICL exchange/explantation in the KC group was inaccurate vault sizing in 11 patients (78.57%), inaccurate refraction in 2 patients (14.28%), and patient dissatisfaction postoperatively in 1 (7.14%) case.

CONCLUSION

ICL implantation results in predictable refractive outcomes over the long term with exchange/explantation rates comparable to previous literature. Improper vault size is the most common cause of ICL exchange/explantation among patients with or without KC.

Early results with the EyeCryl Phakic Toric intraocular lens implantation in keratoconus patients

Objective: Refractive management in keratoconus is challenging. Although some kinds of phakic intraocular lenses have been studied in keratoconus so far, no study evaluated the results of EyeCryl Phakic Toric intraocular lenses in this kind of patients.

Materials and Methods: This is a retrospective chart review study, including all keratoconus patients implanted with an EyeCryl Phakic Toric intraocular lens in at least one of their eyes by an experienced cornea surgeon in Colombia. Follow-up to 6 months after surgery was also included.

Results: A total of 20 eyes of 14 patients were included, with an average age of 29.3 ± 4.2 years. Spherical equivalent improved from a pre-surgical value of –10.31 D to +0.09 D at 6 months. 65% of the patients improved at least one line in the best-corrected distance visual acuity. At 6 months, 70% of the patients were within ± 0.50 D of spherical equivalent emmetropia. No complications occurred in any of the patients.

Conclusion: EyeCryl Phakic intraocular lenses are an excellent option in keratoconus patients with high refractive error.

Abbreviations:

KC = Keratoconus, P-IOL = phakic intraocular lenses, ICL = Implantable Collamer Lens, WTW = White to White, SD = standard deviation, ANOVA = an analysis of variance, UDVA = monocular uncorrected distance visual acuity, CDVA = corrected distance visual acuity

Evaluation of axis alignment and refractive results of toric phakic IOL using image-guided system

AIM

To evaluate accuracy of axis alignment and refractive results of toric phakic intraocular lens (IOL) implantation using a digital imaging system.

METHODS

This retrospective study investigated toric implantable collamer lens (ICL) implantation in 30 eyes of 21 patients with myopic astigmatism more than 2.0 D guided with digital imaging system. Data were collected during the first week after phakic IOL implantation.

RESULTS

Thirty eyes of 21 patients were included in our study. Patients includes 9 males and 12 females. The mean age of the patients was 26.5±7.1 (range 21-44)y. The mean preoperative manifest astigmatism was 3.2±1.7 (range from 2.25 to 4.75) D. The mean postoperative uncorrected distance visual acuity (UCDVA) were 0.07±0.07 (range from 0.1 to 0.0) logMAR. The mean postoperative residual refractive cylinder was 0.25±0.29 (range 0-0.75) D. Eyes with postoperative residual refractive cylinder of 0.5 D or less represented 80% (24 eyes). The mean postoperative toric IOL misalignment measured by the OPD scan III was 1.9°±1.45° (range from 0 to 5°).

CONCLUSION

Image guided system allows accurate alignment of toric ICL. This is associated with good postoperative visual acuity and low residual refractive astigmatism which correlates with the precision of toric phakic IOL alignment.

The Effect of Topical Cyclopentolate on Anterior Segment Parameters in Patients with Keratoconus

Objectives:

To investigate the effect of cycloplegia on anterior segment structures in keratoconus and forme fruste keratoconus patients using corneal topography.

Materials and Methods:

In this study, 40 patients with keratoconus (group 1), 40 patients with forme fruste keratoconus (group 2), and 40 healthy subjects (group 3) were evaluated prospectively. Flat keratometry (K) value (K1), steep K value (K2), mean K value (Kmean), maximum K value (Kmax), corneal astigmatism value, anterior chamber depth (ACD), symmetry index front, symmetry index back, thinnest corneal thickness, central corneal thickness and corneal volume were measured using Sirius topography before and after cycloplegia. Results were compared with one way ANOVA test.

Results:

The mean age of the participants was 24.4±6.2 years for group 1, 26.3±4.3 years for group 2 and 26.5±6.1 years for group 3. There was no difference between the groups with respect to mean age and gender (p>0.05). Mean K1 value was 45.54±2.43 diopters (D) before cycloplegia and 45.46±2.48 D after cycloplegia for group 1 (p=0.044). K1 value didn’t change significantly after cycloplegia for group 2 and 3 (p=0.275, p=0.371). There was no significant difference in K2 and Kmean values after cycloplegia for all groups (p>0.05). Kmax value decreased significantly after cycloplegia in group 1 (p=0.001), but the difference was not significant for group 2 and 3 (p=0.087, p=0.241). ACD increased significantly after cycloplegia in all groups (p=0.001).

Conclusion:

Cycloplegia causes corneal flattening only in manifest keratoconus patients, leading to an increase in ACD in all groups.