Sustainability of Anterior Segment Surgery.

Abstract

Favorable improvement in visual function, credible, long-term sustainability are requisites for anterior eye-segment surgery of the cornea and the lens, key players in ophthalmological optics. Here we analyzed the sustainability, efficacy, and safety of anterior eye-segment surgery, using treatment data from numerous cases, observed over a long period. The effect of a pterygium on visual function is correlated with the degree of invasion of the pterygium in the central cornea. When the pterygium is quite severe, it takes a long time for visual function to stabilize after pterygium surgery. The recurrence rate is lower for incipient pterygium than for recurrent pterygium with a short recurrence period. Analysis of DNA CpG methylation in pterygium has shown that suppressors of cell proliferation are downregulated, while accelerators of cell proliferation are upregulated. Therefore, cells tend to proliferate increasingly in the following order: normal conjunctiva (lowest proliferation rate), incipient pterygium (intermediate proliferation rate), and recurrent pterygium (highest proliferation rate). These findings help elucidate pterygial pathophysiology and prevent its recurrence. In keratorefractive surgery using an excimer laser, the long-term stability of visual function remains problematic. In a long-term study of changes in postoperative visual function and corneal shape, it is noted that physiological properties, including corneal sensitivity and higher-order corneal aberrations recovered at 1 year and stabilized at 10 years after in laser in situ keratomileusis surgery. However, corneal thickness increased continuously for 10 years post-surgery, and myopia continued to increase. In keratoplasty, the transparency of the transplanted cornea and visual functions need to be sustained for a long period. In penetrating keratoplasty (PKP), the mean cumulative transparency cure rate at 12 years post-surgery was 60.4%, which was highest in cases with keratoconus and corneal dystrophy, and lowest in cases with bullous keratopathy and regraft. At 5 years post-surgery, both the cumulative transparency cure rate and postoperative visual function were more favorable in Descemet stripping automated endothelial keratoplasty (DSAEK) than in PKP. Moreover, for artificial corneas (Boston keratoprosthesis) introduced in cases of regraft, both the survival rate and postoperative visual function were more favorable in DSAEK than in PKP. A continuous increase in surface light scattering of specific intraocular lenses (IOL) has been a long-term concern. However, even with an increase in surface light scattering over a period of more than 10 years post-surgery, visual function remained largely unaffected. The observation of frozen torn surfaces of IOLs explanted from patients and unused IOLs that had undergone accelerated aging demonstrated that surface light scattering was caused by a slight phase separation of water on the surface of the IOL. Although forward scattering was not a marked component of the measured surface scattering, it was of clinical concern. Normal conjunctival bacterial flora is thought to have a protective effect against bacterial infection in daily life. However, perioperative prophylactic use of antibiotics may eliminate the normal conjunctival bacterial flora and it is unknown if, after completion of the course of antibiotics, the flora would recover to the same state as before, nor is the growth rate of the normal flora known. Therefore, we analyzed the sustainability of the normal conjunctival bacterial flora after anterior eye-segment surgery. To examine the microenvironment of the anterior eye segment, annual changes in the bacteria isolated from the conjunctival sac prior to cataract surgery were surveyed. The sensitivity of Staphylococcus epidermidis (SE) to levofloxacin (LVFX) decreased annually, indicating that normal conjunctival-sac flora has undergone a rapid increase in resistance to fluoroquinolones. The development of antibiotic resistance in conjunctival bacterial flora is a serious concern. We analyzed the recovery period of normal conjunctival-sac flora and the change in the sensitivity of SE to LVFX over time. In our study, the number of bacterial strains detected was recovered by 3 months post-surgery, while the sensitivity of SE to LVFX had not recovered to the presurgical value even by 9 months post-surgery. In addition, analysis of the effect of the antimicrobial administration period on the acquisition of resistance and the long-term recovery period of bacteria showed a faster recovery of the sensitivity in cases with 1 week of LVFX administration post-surgery compared to those with a 1-month administration. Long-term data of cases with pterygium surgery, keratorefractive surgery, keratoplasty, and IOL were analyzed scientifically. There was recovery of normal flora after perioperative use of antibiotics. Analyses of a large amount of data accumulated over a long period resulted in new findings that would not have been observed using conventional data from short-term studies. This examination of sustainability in ophthalmic surgery provides a basis for the advancement of ophthalmic surgery, but it requires routine collection of clinical data from each patient.