Sturge-Weber Syndrome Treatment & Management

Medical care in Sturge-Weber syndrome (SWS) includes antiepileptic medications for seizure control, symptomatic and prophylactic therapy for headache, glaucoma treatment to reduce the intraocular pressure (IOP), and laser therapy for port-wine birthmark (PWB).

Surgery is desirable in patients with SWS for refractory seizures, glaucoma, and specific problems related to various SWS-associated disorders, such as scoliosis. ^[3]

Medical treatment of glaucoma in SWS usually fails with time, so most ophthalmologists consider surgical therapy to be the mainstay of treatment for SWS-associated glaucoma. ^[94]

Because seizures in Sturge-Weber syndrome (SWS) are typically focal, an antiepileptic medication with efficacy in focal seizures is preferable. Antiepileptic medications include the following:

• Oxcarbazepine (Trileptal)

• Carbamazepine (Tegretol)

• Phenytoin (Dilantin)

• Lamotrigine (Lamictal)

• Levetiracetam (Keppra)

• Valproic acid (Depakote, Depakene, Depacon)

• Zonisamide (Zonegran)

• Topiramate (Topamax)

• Lorazepam (Ativan)

• Phenobarbital (Luminal, Barbita)

• Gabapentin (Neurontin)

• Pregabalin (Lyrica)

• Tiagabine (Gabitril)

• Diazepam (Valium)

• Felbamate (Felbatol)

• Lacosamide (Vimpat)

• Clonazepam (Klonopin)

The modified Atkins diet was reported as safe and effective in reducing seizure frequency in 5 children with SWS. ^[95]

The chance of achieving seizure control with medical therapy in SWS varies. Depending on the series, complete seizure control has been achieved in 10-50% of patients, and refractory seizures occur in 11-83% (see Table 4, below). Results vary by the patient population seen at different centers, with a higher incidence of medical failures reported by surgical centers. However, according to Arizmanoglou, even data from the surgical centers indicate that good seizure control is achieved in one third to one half of the patients seen at these centers. ^[96]

Table 4. Seizure Control in Sturge-Weber Syndrome (Open Table in a new window)

The goal of treatment is control of intraocular pressure (IOP) to prevent optic nerve injury. This can be achieved with the following agents:

• Beta-antagonist eye drops - Decrease the production of aqueous fluid

• Carbonic anhydrase inhibitors - Also decrease production of aqueous fluid

• Adrenergic eye drops and miotic eye drops - Promote drainage of aqueous fluid

Although medical treatment of SWS glaucoma usually fails with time, it may be tried initially. This is because a significant reduction in IOP may be seen, at least temporarily, and may be helpful in clearing the cornea, thus facilitating surgical therapy. Moreover, it can be used to delay filtration surgery in younger patients. This is especially important, because the technical difficulties of operating on a smaller eye are excessive, and there is an increased tendency for scarring at the site of the scleral flap in the younger patient, reducing the chances for long-term surgical success.

Medical therapy can also be used as an adjunct to surgery. Topical antiglaucoma therapy for extended periods of time is sometimes helpful postoperatively to further reduce borderline IOP elevations without the need for reoperation. Initial medical therapy with a topical beta blocker, followed sequentially with the addition of a carbonic anhydrase inhibitor (systemic in infants and topical in older children) and topical prostaglandin (latanoprost [Xalatan]), is a reasonable protocol in patients with SWS.

Recurrent headaches can be treated with symptomatic and prophylactic medications. Kossoff et al found evidence that headaches in Sturge-Weber syndrome (SWS) may be undertreated. The investigators evaluated 68 patients with SWS regarding headaches, identified through the Sturge-Weber Foundation. ^[99] Mean onset of the headaches was 8 years. Fifty-five of the 68 patients had epilepsy as well. Twenty-two of these patients perceived that the headaches were a more significant problem compared with their epilepsy. A positive family history of headaches was seen in 37 of these patients.

Most of the patients were using only abortive treatment, mainly acetaminophen and ibuprofen, while only 15 were tried on preventative agents, including gabapentin, valproate, and amitriptyline (none were on beta-adrenergic blockers).

Kossoff et al also reported that in SWS, triptans and preventative agents appear to be effective for headaches. In the study, 104 patients with SWS and migraine headaches self-reported treatment patterns through a questionnaire. ^[100]

Aspirin has been used for headaches and to prevent vascular disease, although it typically is used in patients who have had neurologic progression or recurrent vascular events. ^[101] Aspirin needs to be used with extreme caution in children because of the risk that Reye syndrome could develop, and the risks and benefits need to be carefully weighed.

Thomas-Sohl, Vaslow, and Maria have recommended 3-5 mg/kg/day of aspirin for stroke-like events. They also recommended varicella and yearly influenza immunizations because of the association of varicella and influenza infections with Reye syndrome. ^[1]

Maria et al reported a decreased incidence of strokelike events in 20 patients with Sturge-Weber syndrome (SWS) who received aspirin. Of 119 strokelike events, 31 occurred in patients treated with aspirin, whereas 88 of these events occurred in those not treated with aspirin. The authors suggested further investigation of aspirin treatment in SWS. ^[21]

Using data from a survey on aspirin use in 34 SWS patients, Bay et al reported a reduction of strokelike episodes from 1.1 to 0.3 per month and a reduction of seizures from 3 to 1 per month. The investigators found that 39% of patients had complications of predominantly bruising or gum/nose bleeding, although none were reported to have discontinued aspirin due to adverse effects. ^[102]

Lance et al, in a review of 58 patients with SWS on aspirin, found that 49 had no significant adverse effects, while the remaining 9 had allergic reactions or minimal to significant bleeding while on aspirin. Reasonable seizure control was seen in 91% of the patients, no or mild hemiparesis occurred in 57% of them, no vision impairment was found in 71% of patients, and no or mild cognitive impairment was seen in 80% of them. The authors suggested that these data support the use of low-dose aspirin for optimizing neurodevelopmental outcome in SWS. ^[103]

The port-wine birthmark (PWB) needs to be evaluated within the first week of life and differentiated from hemangioma.

Treatment of the cutaneous PWB with dye laser photocoagulation has been helpful in reducing the cosmetic blemish from the cutaneous vascular dilatation. ^[2] The therapy should start as soon as possible, since multiple treatments are needed and earlier treatment may reduce the number of sessions required. Also, the smaller the lesion is initially, the lower the number of flashes that will be required to remove it. ^{[104, 105]}

In a survey of patients with PWB that examined the potential psychological benefits from early treatment of the lesion, Troilius et al found that 75% of the patients reported that the PWB had affected their lives negatively, 62% of them were convinced that their lives would improve if the PWB were removed, 47% of them suffered low self-esteem, and 28% of the patients said that the PWB made their school life and education more difficult. No persistent pigmentation changes or posttreatment scarring were reported after laser therapy. ^[106]

Surgical options are available for seizures refractory to medical treatment, especially for focal seizures. ^[107] Erba and Cavazzuti estimated that 40% of patients with SWS could become epilepsy surgery candidates, excluding those with either good seizure control or bilateral disease. ^[39]

Surgical procedures include focal cortical resection, hemispherectomy, corpus callosotomy, and vagal nerve stimulation (VNS). ^[4] SWS is considered one of the catastrophic epilepsies, which, according to Holmes, result in poor seizure control and developmental outcome if not controlled early. However, criteria for medical intractability should be fulfilled before considering surgery. ^[108]

Early surgery has been advocated specifically in SWS to improve outcome and prevent refractory seizures, developmental delay, and hemiparesis. In the era prior to modern neuroimaging, Alexander and Norman suggested exploratory craniotomy and lobectomy if the diagnosis was confirmed, even before seizures started, because they believed that early onset seizures were associated with intellectual disability. ^[109]

Hoffman et al and Ogunmegan et al later advocated early hemispherectomy for seizures. ^{[98, 110]}

Erba and Cavazzuti recommended surgery when seizures, as well as other neurologic events, such as headaches or mild head trauma, are associated with functional neurologic deficits. The presence of such deficits indicates an impairment in cortical perfusion. ^[39]

Arzimanoglou and Aicardi preferred to treat seizures initially with antiepileptic drugs (AEDs), no matter what the age of onset, and recommended surgery when seizures are intractable or when evidence of progressive cortical damage is noted. The appropriate surgical procedure would be determined individually by clinical course, EEG, and neuroimaging. ^{[96, 111]}

Overall, while some variations exist in the criteria, most studies recommend early surgery with difficult-to-control seizures and a progressive clinical course, determined on an individual basis, as noted above.

Outcome of epilepsy surgery in SWS

Three centers have reported surgery outcomes involving groups of more than 10 patients, including Hoffman et al, from Toronto; Arzimanoglou and Aicardi, from Paris; and the authors' series, from Children's Hospital, Boston (see Table 5, below). Of the 32 patients from these groups who had limited resection, 18 became seizure free, 10 experienced improvement, and 4 had no improvement. Of the 26 patients who were treated with hemispherectomy, 24 became seizure free.

The Toronto researchers found that, in terms of developmental outcome, surgical treatment was preferable to medical therapy. They compared the ultimate developmental outcome (determined by intelligence quotient [IQ] score) of medical and surgical therapies in 50 patients, 17 of whom underwent surgery and 33 of whom were given medical therapy. Normal or borderline functioning was more common after surgical treatment (10 of 17 patients [58.8%]) than after medical therapy (11 of 33 patients [33.3%]). ^[92]

When surgery is considered, the choice of appropriate procedure must be the main consideration. The epileptogenic region is located in the cortex adjacent to the angioma, and electrocorticography (ECOG) may be needed. However, the LA usually covers the entire hemisphere, and even areas without angioma may be epileptogenic and therefore need resection to achieve seizure control.

Focal cortical resection

A focal cortical resection (a more limited resection) is performed when the LA and, therefore, the epileptogenic region is smaller and more localized. This can be demonstrated preoperatively by localizing the area of seizure onset, either with surface EEG or ECOG (if invasive monitoring has been done), with a combination of structural and functional neuroimaging, and with intraoperative ECOG.

A hemispherectomy is performed when an extensive, unilateral epileptogenic region exists. When the epileptogenic region is smaller, a focal cortical resection (ie, a more limited resection) is preferable, since it is less likely to cause a neurological deficit. Hoffman reported that focal disease responds well to resection, ECOG identifies adjacent epileptogenic cortex, and hemispherectomy produces a significant improvement in outcome, leading to normal intelligence and a greater than 90% chance of becoming seizure free.

Residual seizures, however, are more likely to occur after a more limited resection than they are following hemispherectomy. Gilly et al reported a 30% failure rate after limited resection, ^[97] and in the combined data from 3 surgical centers, 12.5% of those patients who underwent a limited resection had no improvement. (See Table 5, below.)

Table 5. Surgical Results of Hemispherectomy and Limited Resection from 3 Centers (Open Table in a new window)

In a study of hemispherectomy outcomes in cases of SWS, 81% of patients were found to be seizure free, with 53% off antiepileptic drugs; the type of surgery (anatomic hemispherectomy vs functional hemispherectomy vs hemidecortication) did not influence outcome. In the report, Kossoff et al evaluated the results of hemispherectomy in 32 patients with SWS, using a questionnaire; these patients were identified through the Sturge-Weber Foundation. ^[112]

Although this study was limited because of the volunteer basis of the returned questionnaires, it nonetheless included a larger number of patients were involved in previous studies. Patients had hemispherectomy between 1979 and 2001; the mean age of seizure onset was 4 months, and the median age of surgery was 1.2 years.

Sixteen patients in the study had anatomic hemispherectomy, 14 had functional hemispherectomy, and 2 had hemidecortications, with the surgeries performed in 18 different centers throughout the world. Fifteen patients had complications in the immediate postoperative period, including hemorrhage, infection, and severe headaches, and they underwent reoperation due to persistent seizures, shunting, or hypertension. No deaths occurred.

Age of seizure onset did not predict seizure freedom. Older age, however, had a positive correlation with surgical outcome. Postoperative hemiparesis was not worse than it was before the surgery. Cognitive outcome was not related to age at surgery, side of surgery, or seizure freedom.

The Toronto group suggested that hemispherectomy is more successful if done during infancy, since earlier seizure control helps to preserve the function of the normal hemisphere. ^{[92, 98]}

Alternatively, if the patient is not a candidate for a limited resection or hemispherectomy, such as when disease is bilateral, corpus callosotomy can be performed or VNS can be administered. VNS has been shown to be effective for focal seizures; its mechanism of action is a putative increase in CNS inhibitory activity.

Surgical recommendations

The Sturge-Weber Foundation recruited a task force to evaluate epilepsy surgery in SWS. The following is a summary of recommendations for such surgery, modified to include VNS:

• Hemispherectomy should not be done in every patient with SWS solely because of the emphasis on increasingly early surgery; surgery is appropriate only for medically refractory seizures

• Patients with intractable seizures and very localized lesions should have a limited resection that preserves as much normal tissue as possible

• Video EEG and structural and functional neuroimaging should be used to define the extent of the lesion and the site of seizure origin

• Corpus callosotomy is reserved for patients with intractable atonic or tonic seizures leading to secondary injury, if the patients are not candidates for more definitive surgery

• Surgery should be performed only in a center with an ongoing pediatric epilepsy surgery program

• Although the benefit of surgery for refractory seizures is accepted generally, additional work is needed to evaluate the natural history of the syndrome and the potential benefits and risks of surgery

• VNS can be performed in patients who are not candidates for other surgical procedures

Data on the natural history of SWS are not yet sufficient to advocate hemispherectomy unless refractory seizures occur.

Management of affected eyes emphasizes the reduction of subretinal fluid as the main therapeutic aim in an attempt to stabilize or reverse, if possible, visual impairment caused by nonrhegmatogenous retinal detachment.

However, no reliable treatment of the retinal detachment that develops in these patients has been found, and even in the exceptional case in which the retina can be reattached, fibrous metaplasia of the retinal pigment epithelium and cystoid degeneration of the retina overlying the choroidal hemangioma prevent good visual result. Many such eyes eventually become blind and painful and must be enucleated.

Attempts at repairing the nonrhegmatogenous retinal detachment variously involve cryotherapy and diathermy, xenon arc or argon laser photocoagulation, subretinal fluid drainage, and radiation therapy. A critical factor in a successful outcome appears to be the early initiation of treatment.

Laser photocoagulation

In laser photocoagulation, which is generally considered to be the preferred therapeutic intervention, placement of light photocoagulation scars over the entire tumor is completed in an attempt to strengthen the adhesion between the retina and the underlying pigment epithelium and, thus, to prevent the spread of the retinal detachment. This form of treatment has afforded limited success. However, retinal detachment often recurs even after photocoagulation therapy, and in some patients, complete reattachment of the retina is not possible. Furthermore, treatment success with large hemangiomas, as well as with diffuse, infiltrating tumors of the macula, is limited.

Radiation therapy

A few patients with diffuse choroidal hemangiomas associated with a bullous, nonrhegmatogenous retinal detachment have been treated with radiation therapy (such as brachytherapy or external beam irradiation). Preliminary reports on this treatment suggest that radiation therapy for diffuse choroidal hemangiomas may be a reasonable alternative to photocoagulation, the currently preferred therapy, in selected patients. However, the ultimate risk-to-benefit ratio for this form of treatment is still unknown. Furthermore, the precise indications and contraindications for such treatment currently are unknown.

Drainage

External drainage of subretinal fluid with or without scleral buckling in conjunction with xenon photocoagulation has been used to treat diffuse choroidal hemangiomas associated with large, exudative retinal detachments in SWS.

Pars plana vitrectomy, endolaser, and internal drainage of subretinal fluid can be performed. Cryotherapy and penetrating diathermy are of limited use because of the posterior location of the tumor.

Most ophthalmologists consider surgical therapy to be the mainstay of glaucoma therapy in patients with Sturge-Weber syndrome, ^[94] with antiglaucoma medications primarily useful as treatment adjuncts. However, the selection of surgical technique remains controversial. ^[113] Surgical options in SWS glaucoma include the following:

• Goniotomy

• Trabeculotomy

• Full-thickness filtration surgery

• Partial-thickness filtration surgery (trabeculectomy)

• Combined trabeculotomy-trabeculectomy

• Argon laser trabeculoplasty

• Neodymium:yttrium-aluminum-garnet (Nd:YAG) laser goniotomy

• Seton procedures

Trabeculectomy increases the release of aqueous fluid from the anterior chamber and opens the outflow pathway. Goniotomy is similar but is done through the eye. A Molteno valve can be placed (similar to a shunt), and cyclodestructive procedures with either freezing or laser decrease the production of aqueous fluid. ^[48]

The long-term results of SWS glaucoma surgery are often disappointing, as they are associated with a high failure rate compared with the same procedure performed for primary infantile glaucoma.

Because SWS glaucoma is relatively rare, no controlled series of cases comparing one intervention to another have been published, nor are standard treatment guidelines available. The objective of therapy is rapid and permanent lowering of the IOP into the normal range (generally < 20 mm Hg) or to a level slightly higher but without progression of other signs, such as corneal enlargement, increased myopia, or increased optic nerve cupping.

The anesthesiologist should be aware that the patient has SWS, because the presence of a spinal cord or brain hemangioma may increase the risk of intracerebral bleeding or disseminated intravascular coagulation with anesthesia. In addition, an anesthesia protocol should be planned to prevent the development of hypertension, which could result in hemorrhage.

Goniotomy and trabeculotomy

Goniotomy or trabeculotomy is believed by some to be the treatment of choice in early onset glaucoma in infancy when the probable mechanism for pressure elevation is an abnormal outflow angle. These procedures are often unsuccessful in infants with SWS or are successful only after being repeated several times and with the addition of adjunctive medical therapy. Nevertheless, some authors prefer to perform these procedures initially, because they are sometimes successful and goniotomy also is thought to be less likely to cause complications (especially expulsive choroidal hemorrhage or choroidal effusion) that are associated with a precipitous drop in intraocular pressure.

Filtration surgery

With glaucoma onset in the older age group, when the outflow angle appears clinically normal, glaucoma filtration surgery, either full thickness or partial thickness (trabeculectomy), is more likely to be successful, because it bypasses any component of the glaucoma possibly caused by elevated episcleral venous pressure. Combined trabeculotomy-trabeculectomy may be a reasonable compromise in the older patient with Sturge-Weber syndrome in view of the possible combination of angle abnormality and raised episcleral pressure in glaucoma.

Adjunctive antimetabolites used in conjunction with a filtration surgery may create a more satisfactory degree of intraocular pressure control in this patient population, by slowing wound healing and scar formation. The most commonly used clinical agents are 5-fluorouracil (5-FU) and mitomycin-C. 5-FU usually is given as a series of subconjunctival injections postoperatively. Mitomycin-C is usually applied intraoperatively, using a sponge saturated with mitomycin solution.

Postoperative subconjunctival injections usually are impossible in very young patients; thus, intraoperative application of mitomycin-C most frequently is required in these patients. Mitomycin-C and 5-FU are associated with thinner, more cystic blebs and may carry a higher rate of complications, such as wound leaks, chronic hypotony, and, possibly, late endophthalmitis.

Corticosteroids should be used after filtration surgery to diminish postoperative inflammation and scarring of the bleb. A sub-Tenon injection of a short-acting corticosteroid (eg, dexamethasone, triamcinolone) at the completion of surgery and the use of topical corticosteroid drops or ointment after surgery are recommended.

Cyclocryotherapy

Cyclocryotherapy is difficult to control and has a high complication rate. Therefore, it should be used only when all other procedures have failed or are not feasible, to save useful vision or to prevent or relieve severe pain. New types of cyclodestructive procedures, such as Nd:YAG transscleral laser and therapeutic ultrasonic cyclodestructive procedures, have had only limited trial in pediatric and SWS glaucoma, and their potential for long-term success, as well as for complications, in young patients is not fully understood.

Seton procedures

Seton devices are being used when routine filtration surgery has failed. Encouraging initial results have been reported using various posterior tube shunt implant devices, but long-term follow-up results are not yet available.

Laser surgery

Nd:YAG laser goniotomy and argon laser trabeculoplasty have been used to a limited extent in pediatric glaucoma, and favorable results in some patients with SWS have been reported.

Complications in glaucoma surgery

Management of secondary open-angle glaucoma in patients with SWS, using filtration surgery and seton procedures, bears an increased risk for a number of surgical complications. The most vision threatening and feared of these are expulsive choroidal hemorrhage and intraoperative massive choroidal effusion.

Choroidal hemorrhage and effusion

Sudden change in the IOP gradient when the eye is opened may result in expulsive choroidal hemorrhage from the choroidal hemangioma. Treatment involves rapid closure of all scleral incisions, with restoration of IOP. Transscleral drainage of suprachoroidal blood may also be indicated.

The intraoperative formation of a massive choroidal effusion without hemorrhage occurs frequently during filtration surgery in patients with SWS. Increased episcleral venous pressure in these patients is assumed to cause a similar increase in the venous pressure within the ciliary body and choroid.

Choroidal and retinal detachment

During surgery, when the eye is opened and the IOP falls, rapid transudation of fluid from the intravascular to the extravascular space results. The extravasation of fluid can be massive enough to instantly cause choroidal detachment and, later, serous retinal detachment. Although the mechanism is probably similar to that for the more commonly seen benign postoperative choroidal detachment, the degree and the speed of fluid extravasation during surgery make this entity more serious.

This intraoperative event can mimic an expulsive suprachoroidal hemorrhage because of rapid fluid accumulation after the commencement of surgery. It differs, however, because, if the suprachoroidal space is evacuated, clear, copious amounts of yellow fluid are found and the eye can be decompressed transiently.

It seems that once the intraoperative effusion is treated with immediate drainage, the postoperative prognosis becomes excellent despite the persistence of some degree of choroidal and serous retinal detachment. Smaller, postoperative serous choroidal detachment is another possible complication in SWS.

Serous retinal detachment often occurs in association with choroidal effusion and hypotony. A choroidal effusion may temporarily interfere with the metabolic transport systems of the retinal pigment epithelium. These serous retinal detachments usually resolve spontaneously as the IOP normalizes.

Prevention of complications

Various preoperative and perioperative prophylactic measures to counteract or prevent the above complications have been suggested, including the use of hyperosmotics, maximum preoperative antiglaucoma therapy, prophylactic posterior sclerotomy, prophylactic radiotherapy or laser photocoagulation of the choroidal hemangioma, and electrocautery of the anterior episcleral vascular anomaly.

Eibschitz-Tsimhoni and colleagues demonstrated minimal risk of subchoroidal hemorrhage or effusion in a large case series of patients with SWS undergoing filtration surgery using modern surgical techniques. ^[114] The authors questioned the need for prophylactic posterior sclerotomy in patients with SWS.

Suggested steps to minimize the intraoperative and postoperative hypotony include the following:

• Preplacement of scleral flap sutures

• Injection of a viscoelastic prior to excision of the trabecular meshwork

• Tight suturing of the scleral flap with releasable sutures that can be lysed after surgery with argon laser, removed at the slit lamp or at the time of examination under anesthesia

Any recent intraocular surgery predisposes the eye to the risk of bacterial endophthalmitis. Patients with filtering blebs, especially the thin, avascular blebs seen with the use of mitomycin-C, are at increased risk for developing bacterial endophthalmitis months, or even years, after surgery. Because this risk is increased further by contact lens wear, the use of any type of contact lens in these patients is discouraged. Other potential sources of infection include normal conjunctival flora, episodes of bacterial conjunctivitis, and contaminated medicine dropper bottle tips.

For small degrees of anisometropia in SWS, full optical correction of both eyes or at least full correction of the refractive difference between the eyes is desirable. In higher degrees of anisometropia or in children who develop strabismus, measures to prevent amblyopia and treat strabismus should be initiated. Anisometropic amblyopia may require occlusion therapy along with correction of the refractive error. In some patients, a contact lens may be required to treat fusion difficulty due to aniseikonia.

Any significant strabismus that is still present after the completion of amblyopia therapy, refractive lens correction, and orthoptics is treated best with eye muscle surgery. Avoiding or carefully cauterizing the dilated subconjunctival and episcleral vessels during strabismus surgery is important to prevent bleeding and scarring, so that the conjunctiva and anterior sclera are preserved for future glaucoma procedures.

Primary-care providers should be educated about SWS. Consultations are needed from the following clinicians:

• Neurologist

• Epileptologist - Especially if seizures are intractable

• Dermatologist

• Plastic surgeon

• Psychologist

• Psychiatrist

• Neuropsychologist

• Neuroendocrinologist

Postoperative care frequently requires repeated examination under anesthesia in infants and young children to assess surgical success. If continued borderline IOP elevation is found, then a trial of adjunctive medical therapy with close follow-up care may be continued safely as long as no evidence of progression of glaucoma damage is observed. However, if the IOP remains clearly elevated or evidence of progressive glaucomatous damage is detected, then repeat glaucoma surgery should be performed.

All patients with SWS must have regular ophthalmologic examinations for life, even when no ocular abnormalities are detected initially, to avoid later loss of vision secondary to late-onset glaucoma.