Autosomal dominant iris hypoplasia is caused by a mutation in the Rieger syndrome (RIEG/PITX2) gene

PURPOSE

To determine whether autosomal dominant iris hypoplasia is caused by mutations in the newly described gene for Rieger syndrome (RIEG/PITX2).

METHOD

Mutation screening and sequence analysis was performed in a single family.

RESULTS

A novel mutation in the RIEG/PITX2 gene was found in all affected but no unaffected individuals. This mutation would be expected to result in an arginine to tryptophan amino acid change in the homeodomain of solurshin, the RIEG/ITX2 gene product.

CONCLUSION

Autosomal dominant iris hypoplasia is caused by a defect in the same gene that is defective in many cases of Rieger syndrome.

A randomized study of mitomycin augmentation in combined phacoemulsification and trabeculectomy

PURPOSE

The purpose of the study is to determine whether the intraoperative application of subconjunctival mitomycin C (MMC), during combined phacoemulsification and trabeculectomy, is an effective means of improving filtration, defined as overall lower intraocular pressure (IOP) and less antiglaucoma medication use.

METHODS

Twenty-nine patients with a visually significant cataract and glaucoma were randomized, in a double-masked fashion, to receive intraoperative MMC (0.5 mg/ml) or placebo.

RESULTS

Follow-up ranged from 6 to 30 months (mean, 20 months). Postoperative visual acuity at 1 year was 20/40 or better in 14 of 15 eyes operated on in the placebo group and 13 of 14 eyes operated on in the MMC group. Intraocular pressure at 8 months averaged 15.2 +/- 1.5 mmHg in the placebo-treated eyes versus 12.3 +/- 1.6 mmHg in the MMC-treated eyes. At 12 months, IOPs averaged 16.2 +/- 1.5 mmHg in the placebo-treated eyes versus 12.6 +/- 1.0 mmHg in the MMC-treated eyes. On average, the MMC group had postoperative IOP levels 3.0 mmHg lower than did the placebo group (P = 0.04) throughout the study. In the placebo group, laser suture lysis was required in a greater number of patients (80% versus 43%) and to a greater extent (mean = 2.0 versus 0.7 suture lysed) (P < 0.05). At 12 months, 5 of the 15 patients in the placebo group required an average of 1.8 medications for IOP control, whereas 0 of the 14 patients in the MMC group needed IOP-lowering medications. A late endophthalmitis developed through an intact bleb in one patient in the MMC group; otherwise, complications were minimal in each group.

CONCLUSION

These results suggest that intraoperative MMC application, during combined phacoemulsification and trabeculectomy surgery, does improve early filtration as shown by overall lower IOPs and less antiglaucoma medication use.

Identification of a gene that causes primary open angle glaucoma

Glaucoma is a major cause of blindness and is characterized by progressive degeneration of the optic nerve and is usually associated with elevated intraocular pressure. Analyses of sequence tagged site (STS) content and haplotype sharing between families affected with chromosome 1q-linked open angle glaucoma (GLC1A) were used to prioritize candidate genes for mutation screening. A gene encoding a trabecular meshwork protein (TIGR) mapped to the narrowest disease interval by STS content and radiation hybrid mapping. Thirteen glaucoma patients were found to have one of three mutations in this gene (3.9 percent of the population studied). One of these mutations was also found in a control individual (0.2 percent). Identification of these mutations will aid in early diagnosis, which is essential for optimal application of existing therapies.

Cloning and characterization of a novel bicoid-related homeobox transcription factor gene, RIEG, involved in Rieger syndrome

Rieger syndrome (RIEG) is an autosomal-dominant human disorder that includes anomalies of the anterior chamber of the eye, dental hypoplasia and a protuberant umbilicus. We report the human cDNA and genomic characterization of a new homeobox gene, RIEG, causing this disorder. Six mutations in RIEG were found in individuals with the disorder. The cDNA sequence of Rieg, the murine homologue of RIEG, has also been isolated and shows strong homology with the human sequence. In mouse embryos Rieg mRNA localized in the periocular mesenchyme, maxillary and mandibular epithelia, and umbilicus, all consistent with RIEG abnormalities. The gene is also expressed in Rathke's pouch, vitelline vessels and the limb mesenchyme. RIEG characterization provides opportunities for understanding ocular, dental and umbilical development and the pleiotropic interactions of pituitary and limb morphogenesis.

Fine mapping of the autosomal dominant juvenile open angle glaucoma (GLC1A) region and evaluation of candidate genes

Juvenile Open Angle Glaucoma (GLC1A) is an autosomal optic neuropathy that has been localized previously to chromosome 1q. Here we report the fine mapping of the disease region using YACs and a high density of polymorphic microsatellite markers. This study utilized two large JOAG pedigrees genotyped at 36 loci from chromosome 1q21-q31 to refine the GLC1A locus to a approximately 3-cM region flanked by YAC-derived microsatellite markers D1S3665 and D1S3664. The candidate genes LAMC1, NPR1, and CNR2 were excluded from the region by linkage. Four other genes, SELE, SELL, TXGP1, and APT1LG1, were determined to lie within the critical region through YAC content and linkage mapping. The YAC-STS content map of the critical region provides the groundwork for the construction of a transcription map and the identification of the disease-causing gene.

Comparison of the miotic effects of dapiprazole and dilute pilocarpine in patients with the pigment dispersion syndrome

PURPOSE

Pharmacologically induced miosis can inhibit exercise-induced anterior chamber pigment dispersion in patients with the pigment dispersion syndrome. Long-term inhibition of pigment dispersion in these patients could delay or prevent the development of glaucoma. Unfortunately, most commercially available miotic medications are poorly tolerated by these patients due to their visual side effects. This study evaluates the miotic effects of two medications that cause minimal visual side effects in patients with the pigment dispersion syndrome.

PATIENTS AND METHODS

Pupil diameter in darkness and amplitude of pupil constriction to light were measured before and 1 h after instillation of two drops of 0. 5 dapiprazole in one eye and two drops of 1/6 pilocarpine in the fellow eye of 10 patients with the pigment dispersion syndrome. Gonioscopic photography of iris contour before and after medications was performed in two patients who had significant posterior iris bowing on baseline examination.

RESULTS

Pupil diameter in darkness and amplitude of pupil constriction to light were significantly smaller in eyes treated with 1/6 pilocarpine. Posterior iris bowing was markedly reduced by 1/6 pilocarpine but not by 0. 5 dapiprazole in the two patients with posterior iris bowing.

CONCLUSION

Cholinergic agonists appear to be superior to alpha-adrenergic antagonists as candidate drugs for inhibiting pigment dispersion in patients with the pigment dispersion syndrome.

Linkage of autosomal dominant iris hypoplasia to the region of the Rieger syndrome locus (4q25)

Iris hypoplasia is an autosomal dominant disorder which is frequently associated with glaucoma. This glaucoma is usually resistant to medical therapy and can lead to blindness. A large family of Scandinavian descent with a five generation history of iris hypoplasia was studied. Fifteen individuals were found to have iris hypoplasia, nine of whom had associated glaucoma. In an attempt to identify the chromosomal location of the disease-causing gene, this family was genotyped with short tandem repeat polymorphisms (STRPs) known to map to loci previously associated with glaucoma. The juvenile glaucoma locus at 1q25 and a congenital glaucoma locus on 6p were both statistically excluded. However, significant linkage was demonstrated at the Rieger syndrome locus at 4q25. The highest observed LOD score was 3.70 (theta = 0) and was obtained with marker D4S1616. Three recombination events were observed in affected individuals that together demonstrate that the disease-causing gene lies between markers ACT3E03 and D4S1611, an interval of approximately 7 cM. These results suggest that autosomal dominant iris hypoplasia and Rieger syndrome are allelic.

Rapid visual recovery and long-term intraocular pressure control after donor scleral patch grafting for trabeculectomy-induced hypotony maculopathy

PURPOSE

To report on a 21-year-old man who had persistent hypotony maculopathy eight months after trabeculectomy with mitomycin C.

METHODS

He was treated by excising the filtering bleb, placing a donor scleral patch graft over the trabeculectomy site, and bringing conjunctiva superior to the previous bleb over the patch graft.

RESULTS

He had rapid resolution of his hypotony accompanied by an increase in visual acuity from 4/200 preoperatively to 20/80 at one day, and 20/20 at three months postoperatively. He also established and maintained a filtration bleb which kept his intraocular pressure in the mid teens without the use of medication.

CONCLUSION

Scleral patch grafting may provide rapid resolution of visual loss secondary to hypotony maculopathy.

Aggressive nevus of the iris with secondary glaucoma in a child

PURPOSE/METHODS

We studied a case of an aggressive iris nevus that caused secondary glaucoma in a child.

RESULTS/CONCLUSION

Unlike most iris tumors, this tumor grew from the superior aspect of the iris. The nevus was also unusual because it invaded the trabecular meshwork and caused secondary glaucoma.

Linkage of posterior polymorphous corneal dystrophy to 20q11

Posterior polymorphous dystrophy (PPMD) is an autosomal dominant disorder of the cornea that is clinically recognized by the presence of vesicles on the endothelial surface of the cornea. The corneal endothelium is normally a single layer of cells that lose their mitotic potential after development is complete. In PPMD, the endothelium is often multi-layered and has several other characteristics of an epithelium including the presence of desmosomes, tonofilaments, and microvilli. These abnormal cells retain their ability to divide and extend onto the trabecular meshwork to cause glaucoma in up to 40% of cases. A large family with 21 members affected with PPMD was genotyped with short tandem repeat polymorphisms distributed across the autosomal genome. Linkage was established with markers on the long arm of chromosome 20. The highest observed LOD score was 5.54 (theta = 0) with marker D20S45. Analysis of recombination events in four affected individuals revealed that the disease gene lies within a 30cM interval between markers D20S98 and D20S108.

Tenon's cyst formation after trabeculectomy with mitomycin C

One hundred eyes of 100 patients in whom Tenon's cysts (TCs) developed in the early postoperative period following trabeculectomy with mitomycin C were retrospectively studied to determine their incidence, possible risk factors associated with their development, and the clinical course of the patients in whom they occurred. The incidence of TC formation was 29/100 (29%). Significantly more cysts developed in the men than in the women. There were no significant differences between those patients in whom TCs developed and those in whom they did not in terms of age, race, type of preoperative medications, mean preoperative intraocular pressure (IOP), prior argon laser trabeculoplasty, prior trabeculectomy, prior Tenon's cyst formation, or prior cataract surgery. The 29 patients in whom a Tenon's cyst developed had a mean follow up of 22.0 +/- 12.9 weeks, with a mean IOP at the last examination of 14.2 +/- 6.3 mm Hg (as compared with 20.7 +/- 8.3 mm Hg at the time of diagnosis). One patient required a repeat trabeculectomy with mitomycin C. Two patients required bleb needling, subsequent TC excision, and eventual seton placement. Of the remaining 26, 14 (54%) required no glaucoma medication for IOP control, 11 (42%) required one, and 1 (4%) required two.

Combined phacoemulsification, posterior chamber intraocular lens implantation, and trabeculectomy with mitomycin C

PURPOSE

We evaluated the effectiveness of combined phacoemulsification, posterior chamber intraocular lens implantation, and trabeculectomy with mitomycin C in patients with coexisting cataract and glaucoma.

METHODS

We conducted a retrospective review of the records of 21 consecutive patients who had combined phacoemulsification, posterior chamber intraocular lens implantation, and trabeculectomy with mitomycin C. Patients were selected for the combined procedure on the basis of the degree to which intraocular pressure was controlled, toleration of medical therapy, degree of glaucomatous optic nerve damage, and extent of visual impairment because of cataract. Nine (43%) of the 21 patients had previous incisional surgery and were at high risk of surgical failure. All patients had at least six months' follow-up. Sixteen (76%) of 21 patients had at least one year of follow-up.

RESULTS

The mean preoperative intraocular pressure was 20.8 +/- 5.0 mm Hg (range, 13 to 35 mm Hg), which decreased to a mean postoperative intraocular pressure of 15.1 +/- 3.1 mm Hg (range, 9 to 21 mm Hg) as measured at last follow-up (P = .0002). The intraocular pressure was controlled between 6 and 21 mm Hg) in all patients at last follow-up. Seventeen (81%) of 21 patients had a best-corrected visual acuity of 20/40 or better at last follow-up. No patient had a decrease in visual acuity after surgery. Fifteen (71%) of 21 patients were using no antiglaucoma medications at last follow-up. Four of the remaining six patients were using one medication, and two were using two medications. A hyphema (less than 1.0 mm) was seen in seven (33%) of 21 patients and was the most common postoperative complication. No patient had a postoperative wound or bleb leak or a shallow anterior chamber. No patient developed symptomatic hypotony.

CONCLUSIONS

The glaucoma triple procedure with adjunctive mitomycin C appears to be a safe and effective surgical technique for treating selected patients with coexisting cataract and glaucoma.

Nocturnal arterial hypotension and its role in optic nerve head and ocular ischemic disorders

We measured 24-hour ambulatory blood pressure monitoring and diurnal curve of the intraocular pressure in 166 white patients with anterior ischemic optic neuropathy, normal-tension glaucoma, primary open-angle glaucoma, and other optic nerve head disorders. Hourly average blood pressure data analyses showed a significant (P < .0001) decrease in mean systolic (26%) and diastolic (33%) blood pressure measurements at night. A significantly (P = .0028) lower nighttime mean diastolic blood pressure and a significantly (P = .0044) greater mean percentage decrease in diastolic blood pressure were noted in normal-tension glaucoma than in anterior ischemic optic neuropathy. Patients with arterial hypertension taking oral hypotensive therapy showed a significant association between progressive visual field deterioration and nocturnal hypotension, particularly in anterior ischemic optic neuropathy. Intraocular pressure showed no significant correlation with visual field deterioration in any of these conditions. Our findings suggest that nocturnal hypotension, in the presence of other vascular risk factors, may reduce the optic nerve head blood flow below a critical level, and thereby may play a role in the pathogenesis of anterior ischemic optic neuropathy and glaucomatous optic neuropathy; that is, nocturnal hypotension may be the final insult in a multifactorial situation. The same mechanisms may be true of a number of other ocular ischemic disorders. This finding opens a new dimension in the understanding and management of these visually disabling diseases.

Quantitation of iris transillumination defects in eyes of patients with pigmentary glaucoma

Iris transillumination defects may be important markers of disease severity and/or disease activity in patients with pigmentary glaucoma. We present a simple method for quantitation of iris transillumination defects using infrared iris transillumination videography and computerized image analysis. Three observers independently made multiple measurements of percent iris transillumination (the percentage of visible iris that transilluminates) from three standard images using the technique. The interobserver coefficient of variation was 20.35, 6.55, and 8.01%, respectively, for mild, moderate, and marked iris transillumination. The intraobserver coefficient of variation was much smaller for each image, measuring 4.11, 3.23, and 2.38%, respectively, for mild, moderate, and marked iris transillumination. To exemplify the utility of the technique, a single observer measured percent iris transillumination for both eyes of a group of 13 consecutive patients with asymmetric pigmentary glaucoma. There was a significant correlation between the amount of iris trapsillumination and the severity of glaucoma in the eyes of these patients.

Experimental endoscopic goniotomy. A potential treatment for primary infantile glaucoma

PURPOSE

The purpose of this study is to determine if an endoscope would improve visualization of the anterior chamber angle and facilitate goniotomy in a surgical cloudy corneal model of primary infantile glaucoma.

METHODS

A 23-gauge needle coupled to a 0.8-mm diameter flexible endoscope entered the anterior chamber of porcine cadaver eyes through a corneal incision near the limbus. Internal structures were observed on a videoscreen and recorded as the needle approached and incised pectinate ligaments near Schwalbe's line. The eyes were then prepared for light microscopy and scanning electron microscopy.

RESULTS

Internal structures were clearly visualized on the videoscreen during the goniotomy. The incision of pectinate ligaments was accompanied by the iris falling back and opening of the trabecular meshwork compared with the untreated portion of the angle. This was confirmed histopathologically.

CONCLUSIONS

An endoscope coaxially coupled to a goniotomy needle tip allows visualization of the anterior chamber angle during goniotomy in the pig despite the presence of a cloudy cornea. The porcine anterior chamber angle is a useful animal model for studying the surgical treatment of primary infantile glaucoma.

Genetic linkage of familial open angle glaucoma to chromosome 1q21-q31

Glaucoma is a significant cause of blindness world wide. There is evidence to suggest that at least a subset of the disease is determined genetically. We studied 37 members of a family affected with an autosomal dominant form of juvenile open angle glaucoma and 22 were found to be affected. Linkage analysis using short tandem repeat markers mapped the disease-causing gene to chromosome 1q21-q31. Eight markers were significantly linked (Zmax > 3.0) to the disease, with the highest lod score 6.5 (theta = 0), provided by D1S212. The atrial natriuretic peptide (ANP)/receptor system has been proposed to have a role in glaucoma and one of the ANP receptor genes maps to chromosome 1q.