Toric phakic IOLs in keratoconus-evaluation of preoperative parameters on the outcome of phakic anterior chamber lens implantation in patients with keratoconus

Differences in anterior chamber depth in keratoconus patients with binocular very asymmetry ectasia

BACKGROUND

To evaluate the difference in anterior chamber depth (ACD) between two eyes among keratoconus patients with binocular very asymmetric ectasia (VAE) and to explore the influencing factors.

METHODS

The corneal curvature and ACD in both eyes of patients with VAE were measured by Sirius (version 3.2, CSO, Italy) at the following points: corneal vertex, maximum curvature (apex), and the 1.5 mm, 2.5 mm, and 3.5 mm superior-, inferior-, nasal-, temporal-paracentral from center. The mean pupil power (MPP) and corneal morphology parameters were also measured. Correlations between ACD and curvature and morphology parameters were analyzed by linear regression.

RESULTS

172 eyes of 86 patients (9 to 45 years) were classified into the VAE-N (n = 86) group and the VAE-E group (n = 86) based on the corneal morphology. The central (3.32 ± 0.27 mm versus 3.43 ± 0.29 mm, P < 0.001) and paracentral ACDs increased significantly in the VAE-E group, and the corneal morphology parameters were also significantly higher. The central ACD was significantly correlated with the MPP (r = 0.465), KVf/b (Keratoconus Vertex front/back) (r = 0.306, r = 0.327), and BCVf/b (Baiocchi Calossi Versaci front/back) (r = 0.356, r = 0.416). Linear regression showed good relationships between △ACD and △MPP (R2 = 0.429) and △KVf/b (R2 = 0.504, R2 = 0.536).

CONCLUSIONS

The ACD was larger in the VAE-E group. The difference in ACD between the VAE-E and VAE-N groups was significantly correlated with corneal curvature and the extent of corneal elevation, indicating the influences of both the corneal magnification effect and corneal ectasia on ACD.

Refractive surgical correction and treatment of keratoconus

Keratoconus is an ectatic corneal disorder that causes severe vision loss. Surgical options allow us to correct, partially or totally, the induced refractive error. Intracorneal ring segments (ICRS) implantation represents a minimally invasive surgical option that improves visual acuity, with a high success rate and a low overall complication rate. Corneal allogenic ICRS consists of ring segments derived from allogenic eye bank-processed donor corneas. Selective topography-guided transepithelial photorefractive or phototherapeutic keratectomy combined with CXL is another way in selected cases to improve spectacles corrected distance visual acuity. The microphotoablative remodeling of the central corneal profile is generally planned by optimizing the optical zones and minimizing tissue consumption. Phakic intraocular lens (PIOL) implant is considered in patients with stable disease and acceptable anatomical requirements. The two types of pIOLs, depending on their implantation inside the eye, are anterior chamber-pIOLs, which fixate to the anterior surface of the iris by using a polymethomethacrolate claw at the two haptics, and posterior chamber-pIOLs. In patients with both cataracts and keratoconus, the correct IOL power is difficult to obtain due to the irregular corneal shape and K values. Toric IOL is recommended, but carefully judging the topography and the possible need of subsequent keratoplasties.

Indications for keratoplasty in management of corneal ectasia

PURPOSE OF REVIEW

The current review aims to describe recent advancements in treatment of corneal ectasias and its effect on indications for corneal transplantation.

RECENT FINDINGS

The majority of patients affected by ectatic corneal disease use contact lenses to correct resulting astigmatism. Patients who are intolerant of contact lenses or cannot achieve acceptable vision through conservative measures could consider keratoplasty. However, continuing advancements in both nonsurgical and surgical treatments are either reducing or delaying the need for keratoplasty in patients affected by ectatic corneal disease.

SUMMARY

Corneal transplantation has been the mainstay of treatment for patients with advanced ectatic corneal disease. In the past decade, numerous improvements have been occurred to make contact lenses not only more effective for visual correction, but also more comfortable. Although corneal cross-linking is the only proven treatment known to prevent progression of disease, several other therapies show early potential for those in which cross-linking is contraindicated. Patients now have access to a wider range of therapies before considering keratoplasty.