Anterior membrane dystrophy following cataract extraction

Optimizing the ocular surface prior to cataract surgery

PURPOSE OF REVIEW

Ocular surface disease can significantly impact the outcomes of cataract surgery. Recent studies have examined the efficacy of several new dry eye disease (DED) therapies, the extent to which epithelial debridement affects keratometric measurements in epithelial basement membrane dystrophy (EBMD) and Salzmann nodular degeneration (SND), and the predictability of refractive error following combined pterygium and cataract removal. This review aims to incorporate these newer studies in updating and further emphasizing the need for careful management and optimization of common ocular surface conditions prior to cataract surgery.

RECENT FINDINGS

Common ocular surface conditions such as DED, EBMD, SND, and pterygium can cause significant irregular astigmatism and higher-order aberrations. Their resolution can substantially alter biometry measurements in preparation for cataract surgery, affecting the final visual outcome. Newer therapies for DED, such as topical lifitegrast and thermal pulsation treatment, can aid in this optimization process. If superficial keratectomy or excisions of lesions on the ocular surface are performed, sufficient healing time is needed to allow the ocular surface to reach stability prior to biometry measurements.

SUMMARY

Ocular surface optimization is key to successful cataract surgery planning and reaching desired outcomes.

Treatment of recalcitrant recurrent corneal erosions with inhibitors of matrix metalloproteinase-9, doxycycline and corticosteroids

PURPOSE

To review the efficacy of inhibitors of matrix metalloproteinase-9, corticosteroids, and doxycycline for treatment of recalcitrant recurrent corneal erosion.

METHODS

Retrospective, clinic-based, interventional case series. The medical records of seven consecutive patients who were treated between January 1995 to January 2000 for recurrent corneal erosion who had not responded to conventional therapy were reviewed. Treatment of seven eyes of seven patients consisted of oral doxycycline (50 mg, two times a day) for 2 months along with a topical corticosteroid (either methylprednisolone 1%, prednisolone acetate 1%, or fluoromethalone 0.1%) three times a day, for 2 to 3 weeks. The effects of doxycycline and methylprednisolone on metalloproteinase-9 activity in human corneal epithelial cultures were evaluated by gelatin zymography and a commercial metalloproteinase-9 activity assay kit.

RESULT

Fingernail injury in three of the seven eyes was the most common form of corneal injury. There was no evidence of epithelial basement membrane or corneal stromal dystrophy in any of the patients, although epithelial microcysts were observed in the involved area in three patients. One eye had intact elevated corneal epithelium that showed abnormal diffuse staining with fluorescein dye, and six eyes had a corneal epithelial defect at the time of presentation. In all seven eyes, pain resolved and epithelial defects healed within 2 to 10 days after initiation of therapy. No recurrence was observed during an average follow-up period of 21.9 months (range, 1.5 to 60 months). Methylprednisolone and doxycycline each produced a statistically significant decrease in amount and activity of metalloproteinase-9 in conditioned media of human corneal epithelial cultures.

CONCLUSIONS

Therapy with a combination of medications that inhibit metalloproteinase-9 produced rapid resolution and prevented further recurrence of cases of recurrent corneal erosions that were unresponsive to conventional therapies.

Combined PRK and PTK in myopic patients with recurrent corneal erosion

AIM

To study the results of combined photorefractive keratectomy (PRK) and phototherapeutic keratectomy (PTK) in myopic patients with recalcitrant recurrent corneal erosion.

METHODS

PRK was performed in 16 eyes with the Visx 20/20 excimer laser at a central 6.0 mm zone, following total epithelial scraping. Subsequently, confluent 3.0 mm zones of PTK were ablated at a depth of 6.0 microns, surrounding the zone of PRK. The follow up period ranged from 26 to 42 months.

RESULTS

Complete alleviation of symptoms was demonstrated and there was no recurrence of corneal erosion. Visual acuity (VA) improved slowly following treatment, with a final uncorrected VA ranging between 6/9 and 6/12. A final myopic spherical equivalent < or = -1.0 D was found in 14 out of 16 eyes.

CONCLUSIONS

A combination of PRK and PTK is effective in the alleviation of symptoms and prevention of recurrences of corneal erosion. It is suggested that recalcitrant recurrent corneal erosion is a diffuse disease, although it often manifests as a local problem, and therefore extensive excimer laser ablation is required to prevent recurrence and to alleviate symptoms completely.

Ultrastructural study of the corneal epithelium in the recurrent erosion syndrome

BACKGROUND

This study describes the adhesion systems in the corneal epithelium in the recurrent erosion syndrome and the mechanisms by which binucleate and multinucleate cells are formed within the epithelium.

METHODS

Twenty five samples of sliding epithelium were obtained from 23 patients and were examined by conventional light and transmission electron microscopy.

RESULTS

The separation of the anchoring system occurred either below the level of the anchoring plaques or at the level of the epithelial cell membrane. Normal and degenerate polymorphonuclear leucocytes were found within and between the epithelial cells and within the anchoring layer. Binucleate and multinucleate cells were found within all the layers of the epithelium as were cysts containing degenerate cellular material.

CONCLUSION

The presence of leucocytes and degenerate epithelial cells within the sliding epithelium suggests that these are the source of the metalloproteinases which cleave Bowman's layer below the anchoring system. The formation of binucleate and multinucleate giant cells does not appear to occur by fusion of adjacent cells, but rather by nuclear indentation and cleaving due to an abnormal microtubular system in the cytoskeleton.

Pathology and pathomechanisms of epithelial microcystic and basement membrane abnormalities of the cornea

Four patients with 'microcystic epithelial abnormality' were studied. Photographs demonstrated biomicroscopically visible alterations taking place over months. The histopathology comprising intraepithelial basement membrane abnormalities and intraepithelial cysts is described at the light and electron microscopical level. The biomicroscopically grey-white microcysts correspond in size to the basement membrane abnormalities. The histopathologically described cysts are much smaller. The pathogenetic mechanisms are discussed and it is suggested that breaks in the normal basement membrane are a more likely initial event than a speculative 'primary cellular dystrophy or degeneration'. Cells grow beneath the basement membrane and lift it up into the epithelium. A subsequent intraepithelial synthesis of basement membrane material may account for part of the ultrastructural appearance. The epithelial cysts were found exclusively beneath the basement membrane. They are thought to reflect the cellular maturation which is altered by the inserted membrane. It is suggested that the cysts pass through stages of maturation, which account for the observed difference in appearance.