Hyperopic Keratoconus

Clinical update in nanophthalmos: Features, diseases and complications associated

Nanophthalmos is a rare congenital condition of the eyeball that is characterised by a smaller size of the anterior and posterior segments without associated ocular malformations. Typical features that have traditionally been described in these eyes are short axial length, thickened sclera, cornea with a smaller diameter, narrow anterior chamber, and an increased lens to globe volume ratio. However, at present, there is still a lack of recognised diagnostic criteria for nanophthalmos and a classification of its severity. Its clinical relevance stems from the increased risk of multiple ocular conditions, such as high hyperopia, amblyopia, angle-closure glaucoma, retinal detachment, and cataracts. Likewise, in relation to surgery in these eyes, there are particularities in cataract and glaucoma surgery and with a greater risk of associated intra- and postoperative complications. In this way, the treatment of nanophthalmos focuses on controlling the associated eye conditions and reducing and controlling surgical complications. This review aims to update what has been published in recent years regarding nanophthalmos.

Under-the-Flap Crosslinking and LASIK in Early Ectasia with Hyperopic Refractive Error

Purpose

To present safety, efficacy, and early results of a new combinational treatment for early corneal ectasia with hyperopic refractive error aimed to reinstate emmetropia and stabilize cornea.

Method

This is a retrospective case series. All surgeries were performed at the Beirut Eye Specialist Hospital, Lebanon. Surgical procedure consisted of (1) lifting flap (post-LASIK ectasia)/creation of corneal flap (keratoconus), (2) application of excimer laser ablation to correct refractive error, (3) loose repositioning of flap, (4) under-the-flap irrigation with riboflavin 0.1% dextran solution, and (5) application of UVA light.

Results

A total of 7 eyes (4 patients; mean age 24.25 years; all male) were included. 2 patients had early keratoconus, and 2 patients had early post-LASIK ectasia. Pretreatment vs. last postoperative follow-up visit (mean 11.25 months; range 6–15 months) UDVA (logMAR), spherical equivalent (SE) (D), astigmatism (D), and central pachymetry (µm) were 0.35 ± 0.18 vs. 0.05 ± 0.07, p=0.017; −0.81 ± 0.67 vs. −0.46 ± 0.57, p=0.078; 2.46 ± 0.53 vs. 0.68 ± 0.28, p=0.018; and 547 ± 58 vs. 536 ± 49, p=0.07, respectively. In all eyes, BCVA was 0.1 logMAR or better before and after treatment. No eye showed a decrease in BCVA. Two eyes of one patient had an epithelial ingrowth, which was removed in one case. Follow-up results showed no major complications and no progression of corneal ectasia.

Conclusion

Early results showed that under-the-flap CXL with excimer laser correction is an effective treatment for early hyperopic keratectasia, with the advantage of rapid recovery, postoperative corneal stability, and no epithelial healing complications. The procedure seems to bear a risk for postoperative epithelial growth into the flap interface.

Collagen crosslinking after radial keratotomy

PURPOSE

The aim of this study was to report the outcomes of corneal collagen crosslinking (CXL) after previous radial keratotomy (RK) in patients with decreasing visual acuity and/or diurnal visual fluctuations.

METHODS

The charts of all patients who had undergone CXL because of a worsening corrected distance visual acuity (CDVA) and/or diurnal visual fluctuations after RK were reviewed retrospectively. Uncorrected distance visual acuity, CDVA, manifest refraction, and corneal topography were recorded preoperatively and at 1, 3, 6, and 12 months after the procedure.

RESULTS

Nine eyes of 6 patients that had undergone an RK 15 to 23 years before the CXL were included in the study. In 5 patients (8 out of 9 eyes), discontinuation of diurnal visual fluctuation was reported between 6 and 12 months after the CXL. The mean uncorrected distance visual acuities pre and 12 months after the CXL were 0.7 logarithm of the minimum angle of resolution (logMAR) and 0.6 logMAR, respectively (P = 0.3). The mean CDVAs pre and 12 months after the CXL were 0.2 logMAR and 0.1 logMAR (P = 0.5), respectively. The mean average keratometry pre and 12 months after the CXL were 40.1 and 39.1 diopters (P = 0.06), respectively. The mean corneal astigmatism values pre and 12 months after the CXL were 2.3 and 1.9 diopters (P = 0.06), respectively. The mean manifest refraction spherical equivalents (MRSEs) before and 12 months after the CXL were +1.4 and +2.5 (P = 0.1), respectively.

CONCLUSIONS

CXL is a safe and effective method to restore corneal stability in eyes with a history of RK. However, some of the effect that was achieved at the 6-month visit was blunted at the 12-month visit. Therefore, a longer follow-up is necessary to validate these findings.

Differences in the early biomechanical effects of hyperopic and myopic laser in situ keratomileusis

PURPOSE

To compare changes in corneal hysteresis (CH) and the corneal resistance factor (CRF) in myopic and hyperopic laser in situ keratomileusis (LASIK) and evaluate their relationship to the number of photoablative pulses delivered, a surrogate for ablation volume.

SETTING

Cleveland Clinic Cole Eye Institute, Cleveland, Ohio, USA.

METHODS

Preoperative and 1-week postoperative Ocular Response Analyzer measurements in eyes that had femtosecond-assisted LASIK were studied retrospectively. Changes in CH and CRF were compared and tested for correlation with the number of excimer laser pulses.

RESULTS

Thirteen myopic eyes and 11 hyperopic eyes were evaluated. Preoperative corneal thickness, CH, CRF, programmed correction magnitude, flap thickness, and total number of fixed spot-size photoablative pulses were similar in the 2 groups (P>.1). Decreases in CH and CRF were greater after myopic LASIK than after hyperopic LASIK (P<.005), and changes in CRF were correlated with the number of excimer laser pulses in the myopic group only (r = -0.63, P = .02). Regardless of ablation profile, changes in CH were more strongly correlated with preoperative CH values than with attempted ablation volume.

CONCLUSIONS

With comparable flap thickness and attempted ablation volumes, myopic photoablation profiles were associated with greater decreases in CRF and CH than hyperopic profiles. Results indicate that preoperative corneal biomechanical status, ablation volume, and the spatial distribution of ablation are important factors that affect corneal resistance and viscous dissipative properties differently. Preferential tissue removal in the natively thicker paracentral cornea in hyperopia may partially account for the rarity of ectasia after hyperopic LASIK.