The clinical effectiveness and safety of prophylactic retinal interventions to reduce the risk of retinal detachment and subsequent vision loss in adults and children with Stickler syndrome: a systematic review

Use of vitreous phenotype as a key clinical marker to identify Ocular-only Stickler syndrome in a family with Marfan syndrome

This clinical report describes a family with both Marfan and ocular-only Stickler syndromes. We report 2 cases of ocular-only Stickler syndrome and 2 cases of Marfan syndrome concurrent with ocular-only Stickler syndrome. Type 1 Stickler syndrome and Marfan syndrome share many clinical similarities, and it can be difficult to differentiate them solely based on clinical presentation. Vitreous phenotyping allows for the identification of vitreous anomalies pathognomonic of Stickler syndrome, which can guide future gene sequencing. Having the accurate diagnosis of Marfan or type 1 Stickler syndrome is important, as patients with type 1 Stickler syndrome have higher rates of retinal detachment and will benefit from prophylaxis.

Outcomes in Retinal Detachment Repair and Laser Prophylaxis for Syndromes with Optically Empty Vitreous

PURPOSE

To evaluate and compare surgical outcomes for syndromes with optically empty vitreous (SOEV)-associated rhegmatogenous retinal detachments.

DESIGN

A retrospective, cross-sectional, 2-arm study of a single pediatric vitreoretinal surgeon's patients from a quaternary referral center with SOEV was performed to examine visual and anatomical outcomes of rhegmatogenous retinal detachment and laser prophylaxis.

SUBJECTS

Patients identified either through slit-lamp examination (presence of an optically empty or void space in the vitreous gel structure) or genetic testing. Fifty-six eyes of 49 patients were identified in the retinal detachment arm. Sixty eyes of 48 patients were identified in the laser prophylaxis arm.

METHODS

Comparison of initial retinal detachment (RD) surgical repair via pars plana vitrectomy (PPV), scleral buckle (SB), or PPV-SB with final anatomical success, best-corrected visual acuity (BCVA), and number of surgical procedures. Secondary analysis was performed looking at eyes failing their initial SB, eyes with a giant retinal tear at presentation, eyes failing RD repair within specific time intervals, and eyes where hyaloid was elevated during initial vitrectomy. An additional study arm examined the outcomes of final BCVA and the presence and timing of developing a retinal tear or RD in eyes who received laser prophylaxis.

MAIN OUTCOME MEASURES

Visual acuity, surgical repair techniques (PPV, SB, PPV-SB), number of surgeries, anatomical retinal reattachment success.

RESULTS

Initial SB had statistically significant better final BCVA (P < 0.01) and better final anatomical success (P < 0.01). No statistical difference in the number of surgeries needed to achieve anatomical success between the initial SB versus initial PPV-SB/PPV. Hyaloidal elevation during the initial vitrectomy was associated with improved final BCVA and higher final anatomical success without the use of silicone oil (P < 0.01 and 0.04 respectively). Lastly, eyes that developed RDs after laser prophylaxis had better final BCVA than untreated eyes (P < 0.05).

CONCLUSION

Initial SB yields better overall outcomes in SOEV presenting with rhegmatogenous retinal detachment. Stickler Type-1 patients had similar outcomes compared with other SOEV, suggesting both populations should be treated with similar approaches.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Retinal Detachment Prophylaxis for Patients With Stickler Syndrome: A Survey of Pediatric Retinal Specialist Treatment Preferences

BACKGROUND AND OBJECTIVE

Stickler syndrome is the most common inherited cause of pediatric rhegmatogenous retinal detachment. The purpose of this study was to survey pediatric retinal surgeon preferences for prophylactic treatment of Stickler syndrome patients.

STUDY DESIGN

A voluntary, anonymous 27-question survey was developed by RedCap and distributed to the Association of Pediatric Retinal Surgeons. The survey was distributed on March 17, 2021. Results were tabulated on April 12, 2021 in Microsoft Excel. All surveys returned were included.

RESULTS

Thirty-four (76% response rate) respondents completed the survey. Twenty-six (76%) reported primarily using prophylactic laser retinopexy, four (12%) preferred use of cryotherapy, and 12% reported using prophylactic scleral buckle.

CONCLUSIONS

The majority of the United States. and international pediatric retinal surgeons use laser retinopexy as the primary method of prophylactic treatment. These results may serve as a benchmark for retinal surgeons less familiar with prophylactic treatment approaches. [Ophthalmic Surg Lasers Imaging Retina 2023;54:102-107.].

Preventing Retinal Detachment: Where are We? Implications from Stickler Syndrome

Stickler syndrome, a rare inherited disease, carries a lifetime risk of rhegmatogenous retinal detachment (RRD) of up to 65%, higher than any other predisposing condition known. Both syndromic and non-syndromic eyes suffer RRD predominately from the same pathogenesis, vitreous tractional tears in the peripheral retina. Consequently, extraordinary publications in 2021-2022, each reporting successful prevention of RRD in Stickler syndrome, using 360-degree (encircling) laser retinopexy, provide the first strong evidence upon which similar prophylaxis in non-syndromic eyes at high risk of RRD from peripheral retinal tears can confidently go forward.

THE PROPHYLAXIS OF FELLOW-EYE RETINAL DETACHMENT IN STICKLER SYNDROME: A RETROSPECTIVE SERIES

PURPOSE

To evaluate retrospectively if scleral buckling combined or not to cryopexy reduces fellow-eye retinal detachment (RD) in Stickler syndrome patients who lost their first eye due to RD.

METHODS

Retrospective review of 52 Stickler syndrome patients who received a 6-mm wide, 360° encircling scleral buckling. Thirty-nine (75%; Cryo + Group) also received cryo treatment, whereas the reminder 13/52 (25% Cryo - Group) did not.

RESULTS

Average follow-up was 15.6 ± 2.41 years. Five patients (5/52; 9.6%) developed a retinal detachment 2.6 ± 0.55 years after prophylactic treatment, respectively, 0/39 patients in the Cryo + Group and 5/13 in the Cryo - Group (P < 0.001). All five RD eyes were successfully reattached through revised episcleral surgery and adjunctive cryo treatment. Postop refraction changed an average -1.9 ± 0.74 diopters and best corrected visual acuity at the end of follow-up was 20/25 (0.1 ± 0.07 logarithm of the minimum angle of resolution), not significantly different from the rest of sample population who did not develop RD in their fellow eye.

CONCLUSION

Cryopexy significantly reduced the risk of RD in Stickler syndrome patients undergoing scleral buckling. If RD ensues, the presence of scleral buckling may ease surgical repair and improve final outcome.

Risk and Prevention of Retinal Detachments in Patients with Stickler Syndrome

BACKGROUND AND OBJECTIVE

To report the impact of prophylactic laser retinopexy in the prevention of retinal detachments (RDs) in patients with Stickler syndrome.

PATIENTS AND METHODS

This was a retrospective, comparative case series of patients with Stickler syndrome from the year 2000 to 2019. We compared the rate of RDs between individuals who did and did not receive prophylactic laser therapy. In patients with an RD, we compared the rate of RD in the fellow eye with and without prophylactic laser treatment.

RESULTS

A total of 95 eyes were identified. Fifty-four percent of the overall population was female. The RD rate was 26.7% among eyes without previous prophylactic laser retinopexy and 4.6% among eyes with previous prophylactic laser retinopexy. A Cox proportional model revealed that laser prophylaxis treatment had a statistically significant effect on the risk of RD or retinal tear during the 25-year survival period from birth (P = .034). Eyes receiving treatment were 70% less likely to experience RD or retinal tear (hazard ratio, 0.297; 95% CI, 0.097 to 0.913).

CONCLUSIONS

This study's results suggest a potential role for prophylactic laser retinopexy in the prevention of rhegmatogenous RD among patients with a clinical diagnosis of Stickler syndrome. [Ophthalmic Surg Lasers Imaging Retina. 2022;53:7-11.].

Stickler Syndrome (SS): Laser Prophylaxis for Retinal Detachment (Modified Ora Secunda Cerclage, OSC/SS)

Purpose

To introduce a novel technique of encircling laser prophylaxis (ora secunda cerclage Stickler syndrome, OSC/SS) to prevent rhegmatogenous retinal detachment (RRD) in Stickler syndrome eyes.

Patients and Methods

After first eye RRD at age 50 and at age 18, respectively, a 53-year-old father and his 22-year-old son with type 2 SS (STL2) gave informed consent and underwent OSC/SS prophylaxis, performed in each fellow eye. A 26-year-old STL2 daughter then suffered first eye retinal detachment and similarly chose fellow eye OSC/SS prophylaxis. A second son, 28 years of age with STL2, chose OSC/SS prophylaxis in both eyes.

Results

The three OSC/SS treated fellow eyes have gone 12 years, 11 years, and 8 years without RRD. STL1 and less common STL2 eyes are known to have a similar rate of RRD, and 80% of STL1 fellow eyes develop RRD at a median of 4 years in the absence of prophylaxis. Moreover, five of six (83%) known STL2 family members suffered RRD, only the STL2 son with bilateral OSC/SS remaining bilaterally attached. All five OSC/SS treated eyes (average 8.7 years post-prophylaxis) retained preoperative visual acuity of 20/20 to 20/30, with an average, asymptomatic reduction of meridional field in each eye to 50 degrees. In contrast, in the three eyes having suffered RRD prior to presentation, visual acuity ranged from 20/125 to 8/200 and average meridional field was 29 degrees.

Conclusion

Encircling grid laser (OSC) modified in Stickler eyes to encompass the ora serrata and extend posteriorly to and between the vortex vein ampullae (OSC/SS) is a reasonable RRD prophylaxis option to offer STL1 and STL2 patients as an alternative to no treatment or less effective prophylaxis. Because of rarity and severity, the ultimate proof of safety and efficacy will likely come not from randomized trials, but from a non-randomized, prospective, cohort comparison study of such individual efforts.

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Ocular complications and prophylactic strategies in Stickler syndrome: a systematic literature review

BACKGROUND

Stickler syndrome is a collagenopathy caused by mutations in the genes COL2A1 (STL1) or COL11A1 (STL2). Affected patients manifest ocular, auditory, articular, and craniofacial manifestations in varying degrees. Ocular symptoms include myopia, retinal detachment, cataract, and glaucoma. The aim of this systematic review was to evaluate the prevalence of ocular manifestations and the outcome of prophylactic treatment on reducing the risk of retinal detachment.

METHOD

A systematic literature search was performed in the PubMed database. Information on the cross-study prevalence of myopia, retinal detachment, cataract, glaucoma, visual impairment, severity and age of onset of myopia and retinal detachments. Studies that reported on the outcome of prophylactic treatment against a control group were explored.

RESULTS

37 articles with 2324 individual patients were included. Myopia was found in 83% of patients, mostly of a moderate to severe degree. Retinal detachments occurred in 45% of patients. Generally, the first detachment occurred in the second decade of life in STL1 patients and later in STL2. Cataracts were more common in STL2 patients, 59% versus 36% in STL1. Glaucoma (10%) and visual impairment (blind: 6%; vision loss in one eye: 10%) were rare. Three studies reported on the effect of prophylactic treatment being protective.

CONCLUSION

Ocular manifestations are common in Stickler patients, but the comparison between studies was difficult because of inconsistencies in diagnostic and inclusion criteria by different studies. Sight-threatening complications such as retinal detachments are common but although prophylactic therapy is reported to be effective in retrospective studies, evidence from randomized trials is missing.

Common variants in the COL2A1 gene are associated with lattice degeneration of the retina in a Japanese population

PURPOSE

Lattice degeneration of the retina is a vitreoretinal disorder characterized by a visible fundus lesion that predisposes the patient to retinal detachment. It has been suggested that collagen type II alpha 1 (COL2A1) gene variants may contribute to the development of disorders associated with retinal detachment. Here we investigated whether COL2A1 gene variants were associated with the risk of lattice degeneration of the retina.

METHODS

We recruited 634 Japanese patients with lattice degeneration of the retina and 1694 Japanese healthy controls. We genotyped 13 tagging single-nucleotide polymorphisms (SNPs) in COL2A1. We also performed imputation analysis to evaluate the potential association of un-genotyped COL2A1 SNPs, involving the imputation of 65 SNPs.

RESULTS

Two intronic SNPs-rs1793954 and rs1635533-were significantly associated with lattice degeneration of the retina. The SNP rs1793954 showed the strongest association, with its C allele carrying an increased disease risk (p = 0.0016, corrected p = 0.021, OR = 1.25). The rs1793954 and rs1635533 SNPs were in strong linkage disequilibrium with each other (r ² = 0.99), and conditional analysis revealed that rs1793954 could account for the association between rs1635533 and the disease.

CONCLUSIONS

Our results suggested that COL2A1 gene variants may contribute to the development of lattice degeneration of the retina. Further genetic and functional analyses of COL2A1 variants are needed to clarify the present findings.

Stickler syndrome: exploring prophylaxis for retinal detachment

PURPOSE OF REVIEW

The literature regarding prophylactic treatment of rhegmatogenous retinal detachment in Stickler syndrome remains controversial. We review major published clinical studies and offer a critical analysis of this subject.

SUMMARY

Stickler syndrome is a systemic collagenopathy affecting multiple organ systems including the eye, ear, and skeleton. Stickler syndrome is probably the most common cause of genetically determined pediatric rhegmatogenous retinal detachment. Congenital developmental anomalies constitute over half rhegmatogenous detachments (RRD) in patients less than 10 years. The majority are caused by hereditary vitreoretinopathies associated with Stickler syndrome. Sixty percent of patients with Stickler syndrome develop RRD's over their lifetime with possible severe visual loss and subsequent lifelong morbidity. In view of these complications, some have emphasized the importance of prophylactic laser treatment to the retina of patients with Stickler syndrome to reduce the occurrence of and/or prevent future rhegmatogenous retinal detachment, but there appears to be insufficient data to support the absolute benefit of such prophylactic treatment. Guidelines regarding the age at prophylactic treatment as well as type and frequency of intervention are scarce and would benefit from additional clinical investigations.

Best practice guidelines regarding diagnosis and management of patients with type II collagen disorders

PURPOSE

Skeletal dysplasias comprise a heterogeneous group of inherited disorders of development, growth, and maintenance of the human skeleton. Because of their relative rarity and wide phenotypic variability, patients should be accurately identified, uniformly assessed, and managed by clinicians who are aware of their potential complications and possess the knowledge and resources to treat them effectively. This study presents expert guidelines developed to improve the diagnosis and management of patients with type II collagen skeletal disorders to optimize clinical outcomes.

METHODS

A panel of 11 multidisciplinary international experts in the field of skeletal dysplasia participated in a Delphi process, which comprised analysis of a thorough literature review with subsequent generation of 26 diagnosis and care recommendations, followed by two rounds of anonymous voting with an intervening face-to-face meeting. Those recommendations with more than 80% agreement were considered as consensual.

RESULTS

After the first voting round, consensus was reached to support 12 of 26 (46%) statements. After the panel discussion, the group reached consensus on 22 of 24 revised statements (92%).

CONCLUSIONS

Consensus-based, expert best practice guidelines developed as a standard of care to assist accurate diagnosis, minimize associated health risks, and improve clinical outcomes for patients with type II collagen skeletal dysplasias.

Case Report of a Family Affected by Stickler Syndrome in Which Rhegmatogenous Retinal Detachment Occurred in Five Eyes of Three Siblings

Purpose

Stickler syndrome is an autosomal dominant inherited disorder that is well known to be highly associated with the development of rhegmatogenous retinal detachment. In this study, we report the case of a family affected by Stickler syndrome in which rhegmatogenous retinal detachment developed in 5 eyes of 3 siblings.

Case Series

For treatment, we performed vitreous surgery on 1 eye of the eldest son, and bilateral scleral buckling surgery on the 2 younger children. A good postoperative outcome was obtained on the 4 eyes that underwent scleral buckling surgery, yet the prognosis was poor on the 1 eye that underwent vitrectomy due to redetachment of the retina and corneal complication. Since vitreous surgery was quite difficult due to strong vitreoretinal adhesion, we created an artificial posterior vitreous detachment via the bimanual technique combined with encircling. For the scleral buckling surgery, broad scleral extrusion was needed to seal multiple retinal breaks.

Conclusions

The findings of this study showed a high prevalence of rhegmatogenous retinal detachment in a single family with Stickler syndrome. In these cases, scleral buckling surgery was effective for treating the detached retina, and some prophylactic treatment, such as laser photocoagulation to prevent the occurrence of rhegmatogenous retinal detachment, should be considered for such cases in the future.

Molecular genetics of the COL2A1-related disorders

Type II collagen, comprised of three identical alpha-1(II) chains, is the major collagen synthesized by chondrocytes, and is found in articular cartilage, vitreous humour, inner ear and nucleus pulposus. Mutations in the collagen type II alpha-1 gene (COL2A1) have been reported to be responsible for a series of abnormalities, known as type II collagenopathies. To date, 16 definite disorders, inherited in an autosomal dominant or recessive pattern, have been described to be associated with the COL2A1 mutations, and at least 405 mutations ranging from point mutations to complex rearrangements have been reported, though the underlying pathogenesis remains unclear. Significant clinical heterogeneity has been reported in COL2A1-associated type II collagenopathies. In this review, we highlight current knowledge of known mutations in the COL2A1 gene for these disorders, as well as genetic animal models related to the COL2A1 gene, which may help us understand the nature of complex phenotypes and underlying pathogenesis of these conditions.

Rhegmatogenous retinal detachments associated to Stickler syndrome in a tertiary eye care center in Saudi Arabia

Purpose

To investigate the clinical findings and outcomes of rhegmatogenous retinal detachment (RRD) in Stickler syndrome on affected and fellow eyes that underwent prophylactic retinopexy.

Patients and methods

Chart review of 70 eyes (62 patients). Incidence of RRD, postoperative visual acuity, and risk factors were evaluated.

Results

Twenty-two patients (35%) had RRD in the fellow eye, 37% of the eyes had cataract, 93% had macular detachment, 50% had proliferative vitreoretinopathy, and 41% had posterior vitreous detachment. Success rates were: 60% of patients after scleral buckling; 57.1% after pars plana vitrectomy; and 75% after combined scleral buckling and pars plana vitrectomy. Sixty-one (93.8%) of patients had successful surgery (including second surgery). Silicone oil tamponade was significantly associated with final anatomic outcome, with a protective odds ratio of 0.11 (P=0.027). Visual acuity improved in 54% of eyes and decreased in 5%. Statistically significant associations were present for eyes with final visual acuity ≥20/200, and total retinal detachment (P<0.001); preoperative cataract (P=0.023); and proliferative vitreoretinopathy (P<0.001). RRD developed in 16/44 eyes despite laser prophylaxis.

Conclusion

Prophylactic retinopexy was not beneficial for Stickler syndrome patients. Success of primary surgery for RRD remains low. The primary surgery should be vitrectomy combined with scleral buckling and silicone oil tamponade.

Retinal detachment postphacoemulsification in Bichon Frises: a retrospective study of 54 dogs

OBJECTIVE

To compare rates of retinal detachment (RD) postphacoemulsification in American Bichon Frises with and without prophylactic retinopexy.

PROCEDURES

Medical records of 54 Bichon Frises undergoing phacoemulsification with or without prophylactic retinopexy between 2003 and 2013 in one or both eyes were reviewed from five Midwestern university veterinary teaching hospitals. Inclusion criteria were preoperative ERG, at least 6 months of follow-up postphacoemulsification, and the absence of preexisting RD as determined by ophthalmic examination and/or ultrasound. Statistical analyses were performed using chi-squared test, and Wilcoxon rank-sum tests and Wilson confidence intervals with the P-value <0.05 were considered significant.

RESULTS

Phacoemulsification was performed without retinopexy in 79 eyes (42 dogs, non-PR group) and with prophylactic retinopexy in 23 eyes (12 dogs, PR group). Incidence of diabetes mellitus was 10/42 and 3/12 in the non-PR and the PR groups, respectively (P = 0.93). Intraocular lens implantation was performed in 40/42 non-PR dogs and 11/12 PR dogs (P = 0.63, 73/79 vs. 21/23 eyes). At final re-examination, RD occurred in 4/79 eyes without retinopexy, compared to 0/23 RD in the retinopexy group. There was no statistically significant difference in RD rates between the two groups (P = 0.27).

CONCLUSIONS

These data provide no statistical evidence to support prophylactic retinopexy in Bichon Frises. Due to the low rate of retinal detachment following phacoemulsification without prophylactic retinopexy, the procedure appears to offer limited benefit to offset cost, procedural risk, and risk of extended or repeated anesthesia in Bichon Frises.

Bilateral rhegmatogenous retinal detachment in spondyloepimetaphyseal dysplasia-Strudwick type

PURPOSE

To document the diagnosis and repair of bilateral retinal detachments in a child with spondyloepimetaphyseal dysplasia-Strudwick type, a rare autosomal dominant genetic disorder involving abnormal production of Type II collagen.

METHODS

Case report.

RESULTS

A 13-year-old patient diagnosed with spondyloepimetaphyseal dysplasia-Strudwick type presented with a localized superior temporal retinal detachment in the right eye and a 180° giant retinal tear with an associated macula-off retinal detachment in the left eye. He was highly myopic and had a visual acuity of 20/80 in the right eye and counting fingers in the left eye. He underwent a pars plana vitrectomy in the left eye and laser retinoplexy in the right eye, achieving complete reattachment and/or stabilization of both retinae, with a visual acuity of 20/60 in the right eye and 20/100 in the left eye at 3 months postoperatively.

CONCLUSION

Patients with spondyloepimetaphyseal dysplasia-Strudwick type may be at a higher risk of developing myopia, vitreoretinal degeneration, and a subsequent retinal detachment, although the scientific literature provides a loose association between these conditions. Critically, we propose a temporal association between retinal detachment and the onset of puberty in these patients and suggest that a dilated retinal screening examination should be scheduled at around the time of puberty for patients with spondyloepimetaphyseal dysplasia-Strudwick type to detect any asymptomatic retinal pathology.

Mutation in collagen II alpha 1 isoforms delineates Stickler and Wagner syndrome phenotypes

PURPOSE

Stickler syndrome is an arthro-ophthalmopathy with phenotypic overlap with Wagner syndrome. The common Stickler syndrome type I is inherited as an autosomal dominant trait, with causal mutations in collagen type II alpha 1 (COL2A1). Wagner syndrome is associated with mutations in versican (VCAN), which encodes for a chondroitin sulfate proteoglycan. A three-generation Caucasian family variably diagnosed with either syndrome was screened for sequence variants in the COL2A1 and VCAN genes.

METHODS

Genomic DNA samples derived from saliva were collected from all family members (six affected and four unaffected individuals). Complete sequencing of COL2A1 and VCAN was performed on two affected individuals. Direct sequencing of remaining family members was conducted if the discovered variants followed segregation.

RESULTS

A base-pair substitution (c.258C>A) in exon 2 of COL2A1 cosegregated with familial disease status. This known mutation occurs in a highly conserved site that causes a premature stop codon (p.C86X). The mutation was not seen in 1,142 ethnically matched control DNA samples.

CONCLUSIONS

Premature stop codons in COL2A1 exon 2 lead to a Stickler syndrome type I ocular-only phenotype with few or no systemic manifestations. Mutation screening of COL2A1 exon 2 in families with autosomal dominant vitreoretinopathy is important for accurate clinical diagnosis.

Evaluation and management of pediatric rhegmatogenous retinal detachment

Pediatric rhegmatogenous retinal detachments are rare, accounting for less than ten percent of all rhegmatogenous retinal detachments. While most retinal detachments in the adult population are related to posterior vitreous detachment, pediatric retinal detachment are often related to trauma or an underlying congenital abnormalities or genetic syndrome. The anatomy of pediatric eyes, the often late presentation of the disease, and the high incidence of bilateral pathology in children all pose significant challenges in the management of these patients. We discuss the epidemiology of pediatric rhegmatogenous retinal detachment, review the genetic syndromes associated with a high incidence of retinal detachment, and examine other common causes of retinal detachment in this age group. We then outline an approach to evaluation and management and describe the expected outcomes of repair of retinal detachment in the pediatric population.

Splicing analysis of unclassified variants in COL2A1 and COL11A1 identifies deep intronic pathogenic mutations

UK NHS diagnostic service sequence analysis of genes generally examines and reports on variations within a designated region 5' and 3' of each exon, typically 30 bp up and downstream. However, because of the degenerate nature of the splice sites, intronic variants outside the AG and GT dinucleotides of the acceptor and donor splice sites (ASS and DSS) are most often classified as being of unknown clinical significance, unless there is some functional evidence of their pathogenicity. It is now becoming clear that mutations deep within introns can also interfere with normal processing of pre-mRNA and result in pathogenic effects on the mature transcript. In diagnostic laboratories, these deep intronic variants most often fall outside of the regions analysed and so are rarely reported. With the likelihood that next generation sequencing will identify more of these unclassified variants, it will become important to perform additional studies to determine the pathogenicity of such sequence anomalies. Here, we analyse variants detected in either COL2A1 or COL11A1 in patients with Stickler syndrome. These have been analysed both in silico and functionally using either RNA isolated from the patient's cells or, more commonly, minigenes as splicing reporters. We show that deep intronic mutations are not a rare occurrence, including one variant that results in multiple transcripts, where both de novo donor and ASS are created by the mutation. Another variant produces transcripts that result in either haploinsufficiency or a dominant negative effect, potentially modifying the disease phenotype.