Climatic proteoglycan stromal keratopathy, a new corneal degeneration

Spheroidal Degeneration in Two Siblings: Clinical and Histopathological Features

Spheroidal corneal degeneration is predominantly seen in advanced age and hereditary predisposition to this disorder is very rare. This report describes the occurrence of bilateral band-shaped spheroidal corneal degeneration in two siblings.

The expression pattern of the subunit of chaperonin containing T-complex polypeptide 1 and its substrate, alpha-smooth muscle actin, during corneal wound healing

PURPOSE

This study was designed to demonstrate the expression of the chaperonin containing T-complex polypeptide 1 (CCT) and alpha-smooth muscle actin (alpha-SMA), in normal corneas and corneas treated with ultraviolet radiation (UVR). The wound model chosen is previously characterized, the injury is mild and the cornea heals to transparency.

METHODS

Rabbit corneas were exposed to UVR at the dose producing keratitis. The corneas were allowed to heal for up to 5 days and the paraffin-embedded tissue specimens were double stained and examined morphologically and immunohistochemically. Expression of CCT and alpha-SMA genes was investigated by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

There was a front of repopulating keratocytes that showed positive staining for alpha-SMA after 3 days. The alpha-SMA mRNA was already strongly expressed after 1 day, whereas the expression level of CCT was increased after 2 days. After 5 days the levels were decreased. By this time the stroma was partly repopulated by keratocytes.

CONCLUSION

In a mild wound, the expression of alpha-SMA mRNA is followed by expression of mRNA of at least one subunit of the complex folding alpha-SMA. At protein level, alpha-SMA is detected in the front line of repopulating keratocytes. Expression levels for both mRNAs decline as the stroma repopulation process progresses.

Biglycan gene expression in UVR-exposed rabbit corneas

PURPOSE

It is known that stromal proteoglycans play an important role in the hydration and transparency of the mammalian cornea. Proteoglycans have been described as a pathological deposit in climatic proteoglycan stromal keratopathy, which is associated with chronic ultraviolet radiation (UVR) exposure. The expression of dermatan sulfate proteoglycan biglycan in the cornea was thus studied after exposure of rabbit eyes to UVR.

METHODS

New Zealand albino rabbit corneas were exposed to UVR at 310 nm at the dose producing biomicroscopically significant keratitis (0.47 J/cm2). Animals were killed 3, 7 and 28 days after exposure (five rabbits in each group). Five rabbits were used as controls and did not receive any UVR treatment. Expression of biglycan mRNA in the corneas was investigated by competitive reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

There was no expression of biglycan mRNA in the control group. In the UVR-exposed groups, biglycan mRNA had still not been expressed 3 days after exposure. The expression of biglycan mRNA was observed in all UVR-treated corneas 7 days after exposure (p < 0.05). By 28 days after UVR exposure the expression of biglycan mRNA had decreased (not statistically significant).

CONCLUSIONS

There is no detectable biglycan gene expression in the normal rabbit cornea. Ultraviolet radiation exposure leads to a distinct expression of biglycan mRNA in the rabbit cornea that decreases 4 weeks after exposure, indicating the involvement of biglycan in the corneal repair process. Biglycan appears to be a novel marker of corneal wound healing.

Bilateral central anterior stromal opacity of the cornea: dystrophy or degeneration?

PURPOSE

To describe a bilateral, central, oval corneal opacity not resembling any known corneal degeneration or dystrophy.

METHODS

Ophthalmic examination, corneal topography, and pachymetry.

RESULTS

A 30-year-old woman presented complaining of blurred vision. Biomicroscopic examination revealed bilateral, centrally located, oval, diffuse opacification of the anterior corneal stroma. Corneal topography showed slightly paracentral corneal flattening and irregular astigmatism in both eyes. Pachymetry indicated thinning of the central cornea in the left eye. No evidence of systemic disease was found. Family members had no corneal abnormalities.

CONCLUSIONS

This unusual keratopathy closely resembles climatic proteoglycan stromal keratopathy. However, it is not clear whether the condition should be described as a dystrophy or degeneration.

Repeated UVR exposures cause keratocyte resistance to apoptosis and hyaluronan accumulation in the rabbit cornea

PURPOSE

To evaluate hyaluronan (HA) production and level of apoptosis of corneal cells after repeated UVR exposures.

METHODS

Fifteen albino rabbit corneas were exposed to 310 nm UVR at a dose that causes biomicroscopically significant keratitis (0.47 J/cm2). Nine rabbits received a single dose of UVR. Six rabbits were irradiated 3 times at 7-day intervals. Rabbits exposed to the single dose of UVR, were sacrificed 24 hours, 7 and 14 days after irradiation. Rabbits exposed to the repeated doses of UVR, were sacrificed 24 hours and 14 days after the last irradiation. The corneal tissue specimens were processed for histological analysis using specific staining for HA, and the TdT-dUTP terminal nick-end labeling (TUNEL) assay.

RESULTS

Corneas exposed to a single UVR dose showed extensive positive TUNEL staining 24 hours after exposure. Almost all basal epithelial cells, keratocytes throughout the entire thickness of the stroma, and endothelial cells were TUNEL-positive. No HA was found 24 hours after exposure. Extracellular HA staining of high intensity was found at day 7 throughout the entire central stroma, except the anterior one-fourth. At day 14 only a faint HA staining was detected in the posterior stroma, close to Descemet's membrane. Corneas exposed to repeated UVR doses showed at 24 hours positive TUNEL staining only in epithelial cells and in very few stromal cells. The majority of stromal cells and endothelial cells were unaffected. At the same time HA staining of very high intensity was found both at 24 hours and day 14, and it was evenly distributed throughout the entire thickness of the stroma.

CONCLUSION

Repeated UVR exposures lead to increased production and accumulation of HA in the corneal stroma. The repopulated keratocytes are much more resistant to apoptosis than the native ones. HA accumulation may be a sign of long-term changes in the cornea.

Excimer laser phototherapeutic keratectomy before cataract extraction and intraocular lens implantation

PURPOSE

To determine whether sequential excimer laser phototherapeutic keratectomy (PTK) followed by cataract extraction and intraocular lens (IOL) implantation with power calculation based on the new corneal curvature is effective in managing superficial corneal disease.

METHODS

Of a consecutive series of 18 eyes of 16 patients who received PTK, extracapsular cataract extraction, and posterior chamber IOL insertion, twelve eyes had spheroidal degeneration and six eyes, calcific band keratopathy. The PTK was done with either a Summit ExciMed laser or a Visx 20/20 laser using a 5.0 to 6.0 mm diameter ablation zone. Intraocular lens calculations were done a mean of 3.3 months after PTK. Cataract surgery was by extracapsular cataract extraction with posterior chamber IOL implantation. Patients were followed up for a mean of 14 months.

RESULTS

Eighteen eyes completed follow-up examinations. Mean time between PTK and cataract surgery was 3.3 months. Phototherapeutic keratectomy was completed in one surgery session using one ablation treatment (ablation and slitlamp microscopy) in five eyes, two treatments in seven eyes, and three to seven treatments in six eyes. Eleven (61%) of 18 eyes had a final spherical equivalent refraction within +/- 1.00 diopter. Two eyes developed moderate to marked subepithelial reticular corneal haze from PTK. No vision-threatening complications occurred.

CONCLUSION

Excimer laser PTK followed by cataract extraction and posterior chamber IOL implantation can safely and effectively treat eyes with superficial corneal disease and age-related cataract. Calculation of the IOL power after the cornea has healed from the PTK compensates for changes in corneal curvature.